Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0043066 negative regulation of apoptotic process	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: IBA annotation for negative regulation of apoptotic process. CRYAA has well-documented anti-apoptotic activity. PMID:14752512 demonstrated that alphaA- and alphaB-crystallins bind to pro-apoptotic Bax and Bcl-X(S) proteins via GST pulldown and coimmunoprecipitation, preventing their translocation from cytosol to mitochondria during staurosporine-induced apoptosis. The R116C cataract mutant shows much weaker affinity to Bax and Bcl-X(S) (PMID:14752512). PMID:14512969 showed that the R49C mutant failed to protect lens epithelial cells from staurosporine-induced apoptosis. The IBA annotation is phylogenetically appropriate for sHSP family members with anti-apoptotic activity. This is a secondary/non-core function for CRYAA beyond its primary structural and chaperone roles. Reason: Anti-apoptotic activity is well-supported by direct experimental evidence from PMID:14752512 and PMID:14512969, and the IBA annotation is phylogenetically sound. However, this is a secondary function compared to the core structural and chaperone holdase roles in the lens. Supporting Evidence: PMID:14752512 alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis through interactions with members of the Bcl-2 family PMID:14752512 alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo PMID:14512969 unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to the nucleus and failed to protect from staurosporine-induced apoptotic cell death
GO:0005737 cytoplasm	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for cytoplasm localization. CRYAA is abundantly expressed in the cytoplasm of lens fiber cells. Multiple IDA-level studies confirm cytoplasmic localization including PMID:19464326, PMID:14752512, PMID:29259299, PMID:19503744, PMID:26004348, and PMID:30340470. UniProt also lists cytoplasm as a confirmed subcellular location. The IBA annotation is consistent with direct experimental evidence and is phylogenetically appropriate. Reason: Cytoplasmic localization is the primary location of CRYAA, confirmed by multiple independent IDA studies using fluorescence microscopy in lens epithelial cells and other cell types. The IBA annotation is well supported. Supporting Evidence: PMID:29259299 Wild-type alphaA-crystallin was also equally distributed in the cytoplasm PMID:14752512 alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis
GO:0005634 nucleus	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: IBA annotation for nucleus localization. UniProt notes that CRYAA (HSPB4) translocates to the nucleus during heat shock and resides in SC35 splicing speckles. This is a stress-induced secondary localization rather than the primary constitutive location. The IBA annotation is phylogenetically appropriate for sHSP family members that show nuclear translocation under stress. Reason: Nuclear localization is real but conditional (stress-induced). UniProt records CRYAA translocation to SC35 splicing speckles during heat shock. This is not the primary constitutive localization of CRYAA, which is cytoplasmic. Keeping as non-core reflects that this is a secondary, stress-dependent localization. Supporting Evidence: UniProtKB:P02489 Nucleus. Note=Translocates to the nucleus during heat shock and resides in sub-nuclear structures known as SC35 speckles or nuclear splicing speckles.
GO:0009408 response to heat	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for response to heat. CRYAA is a member of the small heat shock protein (sHSP) family and its chaperone-like activity was explicitly demonstrated using heat-induced aggregation assays (PMID:8943244). The protein suppresses heat-induced aggregation of aldose reductase and other lens proteins. CRYAA also translocates to nuclear SC35 speckles during heat shock (PMID:19464326). The IBA annotation is phylogenetically appropriate for the sHSP family whose hallmark is response to heat stress. Reason: Response to heat is a core function of sHSP family members. CRYAA suppresses heat-induced protein aggregation (PMID:8943244) and shows heat-shock-dependent nuclear translocation (PMID:19464326). The IBA annotation is well justified for the sHSP family. Supporting Evidence: PMID:8943244 both WT and W9F subunits completely suppressed the heat-induced aggregation of aldose reductase file:human/CRYAA/CRYAA-deep-research-falcon.md As a chaperone, HSPB4 binds partially unfolded proteins to prevent misfolding and aggregation, thereby maintaining lens proteostasis and cell survival
GO:0042026 protein refolding	IBA GO_REF:0000033	REMOVE	Summary: IBA annotation for protein refolding. This is problematic for CRYAA. While some sHSP family members can assist in protein refolding (e.g., HSPB1/Hsp27 cooperates with Hsp70 to refold substrates), CRYAA specifically acts as a holdase that prevents aggregation but does NOT refold proteins. This is documented by the NOT annotation to GO:0042026 (ISS from bovine ortholog, GO_REF:0000024). The IBA propagation from the broader sHSP family is overly broad for CRYAA, which lacks foldase activity. PMID:19464326 showed that HSPB1 and HSPB5 kept heat-unfolded substrates folding-competent, but HSPB7 did not support refolding, highlighting functional divergence within the family. CRYAA has holdase but not foldase activity. A focused OpenScientist function-assignment run on this hypothesis (file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md) independently reached the holdase-not-foldase conclusion on mechanistic and architectural grounds: the UniProt record for P02489 has "no nucleotide-binding site and no ATPase domain", so CRYAA cannot be an autonomous foldase, and the productive refolding step is executed by downstream ATP-dependent Hsp70/Hsp100 chaperones (PMID:34055885, PMID:35281256). That run nonetheless recommended RETAINing the IBA as a non-core cooperative process. That recommendation is not adopted here, for two reasons that the run got factually wrong (see the reference_review on its report): it did not register that GOA already carries a NOT\|involved_in ISS annotation on this very term, and its headline recommendation to "add the missing GO:0051082" is a no-op -- GOA already carries three GO:0051082 annotations for P02489 (IBA, IPI from PMID:8943244, IMP from PMID:18407550), and GO:0051082 is now formally obsolete, with the GO obsoletion note directing replacement to GO:0044183 or GO:0140309. On provenance: this IBA's actual ancestral evidence set is the WITH/FROM column of the GOA row, which is six Drosophila sHSP genes plus the PANTHER node -- FB:FBgn0001224 (Hsp23), FB:FBgn0001225 (Hsp26), FB:FBgn0001226 (Hsp27), FB:FBgn0011296 (l(2)efl), FB:FBgn0031037 (CG14207), FB:FBgn0035817 (CG7409), PANTHER:PTN000897708. Those fly seeds do carry direct refolding evidence at the source: the local DROME/Hsp23, DROME/Hsp26 and DROME/Hsp27 reviews each retain GO:0042026 on IDA-level cellular refolding assays (PMID:26705243, PMID:16572729). So the source supports the term; the question is whether it transfers to human alphaA, and a Drosophila-sHSP-to-human-alphaA transfer is a long reach. GOA's own NOT\|involved_in ISS from the bovine ortholog (UniProtKB:P02470) is the direct answer that it does not. Separately, PMID:8093612 and PMID:1438232 are family-level literature context for the sHSP refolding property rather than part of this IBA's evidence chain, and neither is alphaA-specific. PMID:8093612 (Jakob 1993) assayed "murine Hsp25, human Hsp27, and bovine alpha-B-crystallin" -- alphaA-crystallin is not among the proteins named in the abstract (only the abstract is cached). PMID:1438232 (Horwitz 1992) reported refolding of GdnHCl-denatured gamma-crystallin using unfractionated alpha-crystallin (alphaA + alphaB) with a circular-dichroism readout, which as the run notes can reflect secondary-structure recovery once aggregation is suppressed rather than chaperone-catalyzed folding. Reason: CRYAA is a holdase, not a foldase. It prevents aggregation of denatured proteins but does not refold them. The NOT annotation to GO:0042026 (ISS, GO_REF:0000024) explicitly documents this. The IBA propagation from the broader sHSP family is incorrect for CRYAA because not all sHSP members have refolding activity. There is functional divergence within the family (PMID:19464326). The IBA's seeds are six Drosophila sHSPs (see summary) which do have their own refolding evidence, so this is a transfer-failure rather than a bad source: the property does not reach human alphaA, as GOA's own NOT\|involved_in ISS from bovine UniProtKB:P02470 states directly. The family-level literature context sometimes cited for refolding (PMID:1438232, PMID:8093612) is mixed-oligomer or non-alphaA and does not establish autonomous alphaA foldase activity; both the domain architecture (single alpha-crystallin domain, no nucleotide-binding domain) and the modern mechanistic consensus that Hsp70/Hsp100 execute the refolding step (PMID:34055885, PMID:35281256) argue against it. Propagation Review Root cause: PROPAGATION BAD Failure modes: PSEUDO OR SUBACTIVITY LOSS FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000897708 · small heat-shock protein PANTHER source node SUPPORTS SOURCE BUT NOT TARGET The family source can include refolding-associated sHSP biology, but CRYAA is reviewed as a holdase that prevents aggregation without refolding clients. FB:FBgn0001224 · Drosophila Hsp23 SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA. The local DROME/Hsp23 review retains GO:0042026 on IDA-level cellular refolding evidence (PMID:26705243, PMID:16572729), so the term is well supported at the source; it is the transfer to human alphaA that fails. FB:FBgn0001225 · Drosophila Hsp26 SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA. DROME/Hsp26 retains GO:0042026 on IDA cellular refolding evidence (PMID:26705243), framed as holding substrates in a refoldable state for the HSP70 machine. FB:FBgn0001226 · Drosophila Hsp27 SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA. DROME/Hsp27 keeps GO:0042026 as non-core, describing an indirect refolding contribution via handoff to the Hsp70 system. FB:FBgn0011296 · Drosophila l(2)efl SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA; a Drosophila sHSP not reviewed locally. FB:FBgn0031037 · Drosophila CG14207 SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA; an uncharacterized Drosophila sHSP not reviewed locally. FB:FBgn0035817 · Drosophila CG7409 SUPPORTS SOURCE BUT NOT TARGET An actual WITH/FROM seed for this IBA; an uncharacterized Drosophila sHSP not reviewed locally. UniProtKB:P02470 · bovine CRYAA NOT-refolding source SUPPORTS TRANSFER The independent NOT annotation from the bovine ortholog supports the target review by contradicting the positive IBA to protein refolding. Supporting Evidence: PMID:8943244 alpha-crystallin subunits associate to form large oligomeric aggregates that express chaperone-like activity, as defined by the ability to suppress nonspecific aggregation of proteins destabilized by treatment with a variety of denaturants PMID:19464326 Unlike HSPB1 and HSPB5, that chaperoned heat unfolded substrates and kept them folding competent, HSPB7 did not support refolding PMID:35281256 HSPBs act as ATP-independent holdases, avoiding misfolded substrates aggregation PMID:34055885 Formation of these assemblies facilitates subsequent Hsp70 and Hsp100 chaperone-dependent disaggregation and substrate refolding into native species PMID:8093612 we studied the influence of murine Hsp25, human Hsp27, and bovine alpha-B-crystallin (an eye lens protein homologous to sHsps) on the unfolding and refolding of citrate synthase and alpha-glucosidase in vitro file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md no nucleotide-binding site and no ATPase domain
GO:0051082 unfolded protein binding	IBA GO_REF:0000033	MODIFY	Summary: GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962). CRYAA/HSPB4 does interact with partially unfolded/destabilized proteins, but the term "unfolded protein binding" is problematic because it implies a simple binding function rather than the active chaperone holdase activity that CRYAA performs. CRYAA suppresses nonspecific aggregation of destabilized proteins (PMID:8943244) but does NOT refold them -- it is a holdase, not a foldase. The IBA annotation is phylogenetically propagated from sHSP family members across Drosophila, zebrafish, and mammals, which is appropriate for the family-level chaperone function. However, the term itself needs replacement, and as of 2026-07-25 no adequate replacement exists. GO:0051082 is now FORMALLY OBSOLETE ("obsolete unfolded protein binding"), and its obsoletion comment offers only two replacements: "protein folding chaperone (GO:0044183) or unfolded protein holdase activity (GO:0140309)". Neither fits CRYAA. GO:0044183 is for foldases that "assist the protein folding process", which CRYAA does not do. GO:0140309, despite having been relabelled to "unfolded protein holdase activity", retains an unchanged CARRIER-SPECIFIC definition -- "A protein carrier activity that binds to a protein in an unfolded state and escorts it to an acceptor molecule or to a specific location" -- and remains a child of GO:0140597 "protein carrier chaperone". CRYAA is an in-situ holdase that prevents aggregation without escorting substrates between compartments, so it does not satisfy that definition. Per projects/UNFOLDED_PROTEIN_BINDING.md, GO:0140309 was created (go-ontology#30552) for TIM carrier-holdases, and CRYAA is listed there as "retain GO:0051082; in-situ holdase, not carrier". GO:0051082 is therefore retained as an INTERIM annotation pending a general "holdase chaperone activity" NTR, consistent with the sibling sHSP reviews (DROME/Hsp23, DROME/Hsp27, yeast/HSP26). As a biological process annotation, GO:0050821 "protein stabilization" (defined as "Any process involved in maintaining the structure and integrity of a protein and preventing it from degradation or aggregation") is also relevant and is already annotated for CRYAA via PMID:12235146. Reason: GO:0051082 is now formally obsolete. CRYAA has well-documented chaperone-like holdase activity: it suppresses aggregation of heat-denatured aldose reductase and singlet-oxygen-damaged gamma-crystallin (PMID:8943244). However, it does NOT refold proteins (NOT annotation to GO:0042026 protein refolding, ISS). The correct MF replacement does not yet exist: GO:0044183 is foldase-specific and GO:0140309 is carrier-specific (escorting between cellular components, per go-ontology#30552), which does not describe CRYAA's in-situ holdase activity. Retain GO:0051082 as an interim annotation until a general holdase chaperone activity NTR is created. GO:0050821 "protein stabilization" is appropriate as a BP term. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000897708 · small heat-shock protein source node SUPPORTS SOURCE BUT NOT TARGET The source supports small heat-shock protein holdase biology, but the propagated unfolded-protein-binding term is obsolete and no adequate in-situ holdase activity term yet exists to replace it. Proposed replacements: holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific) Supporting Evidence: PMID:8943244 alpha-crystallin subunits associate to form large oligomeric aggregates that express chaperone-like activity, as defined by the ability to suppress nonspecific aggregation of proteins destabilized by treatment with a variety of denaturants including heat, UV irradiation, and chemical modification PMID:8943244 both WT and W9F subunits completely suppressed the heat-induced aggregation of aldose reductase
GO:0002088 lens development in camera-type eye	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for lens development in camera-type eye. CRYAA is the most abundantly expressed protein in the ocular lens and is essential for normal lens development and transparency. UniProt states it is expressed in the eye lens (PubMed:12356833, PubMed:23255486). Knockout studies in zebrafish show abnormal differentiation of lens fiber cells when alpha-crystallins are absent (cited in PMID:29259299). Numerous CRYAA mutations cause congenital cataracts (PMID:9467006, PMID:14512969, PMID:18407550), demonstrating the essential role in lens development. The IBA annotation is appropriate for crystallin family members involved in lens development. Reason: CRYAA is a core lens protein essential for normal lens development. Mutations consistently cause congenital cataracts (PMID:9467006, PMID:14512969, PMID:18407550). The IBA annotation appropriately captures this conserved developmental role. Supporting Evidence: PMID:14512969 The alphaA-crystallin (CRYAA) gene (CRYAA) encodes a member of the small-heat-shock protein (sHSP) family of molecular chaperones and is primarily and abundantly expressed in the ocular lens PMID:9467006 we found that a missense mutation, R116C, is associated with ADCC in this family
GO:0005198 structural molecule activity	IEA GO_REF:0000117	MODIFY	Summary: IEA annotation for structural molecule activity. CRYAA is a major structural protein of the eye lens contributing to transparency and refractive index (UniProt FUNCTION section). While correct, the more specific child term GO:0005212 "structural constituent of eye lens" is also annotated and is more informative. This broader IEA term is acceptable as a parent term but less informative than the specific one. Reason: While structural molecule activity is correct for CRYAA as a major structural lens protein, the more specific child term GO:0005212 "structural constituent of eye lens" is already annotated and is more informative. Modifying to the specific term for consistency with the IDA annotation review of the same GO term. Proposed replacements: structural constituent of eye lens
GO:0005212 structural constituent of eye lens	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for structural constituent of eye lens. This is one of the most appropriate terms for CRYAA. As alphaA-crystallin, it is the most abundant soluble protein in the lens, contributing to transparency and refractive index (UniProt FUNCTION: "Contributes to the transparency and refractive index of the lens"). The IEA mapping is accurate and captures a core function. Reason: CRYAA is the defining structural constituent of the eye lens. This is a core function annotation. UniProt documents that CRYAA contributes to transparency and refractive index of the lens, confirmed by the fact that mutations cause cataracts (PMID:9467006, PMID:18407550).
GO:0005634 nucleus	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: IEA annotation for nucleus based on UniProt subcellular location mapping. UniProt lists nucleus as a confirmed subcellular location, noting that CRYAA translocates to the nucleus during heat shock and resides in SC35 speckles (PMID:19464326). The IEA mapping is correct and consistent with the IBA and IDA annotations for the same term. However, nuclear localization is stress-induced and secondary, not constitutive. Reason: The IEA mapping from UniProt subcellular location is accurate. Nuclear localization is supported by PMID:19464326 showing heat-shock-induced translocation to SC35 speckles. However, this is a stress-dependent secondary localization, not the primary constitutive location of CRYAA. Marked as KEEP_AS_NON_CORE for consistency with the IBA and IDA annotations for the same GO term.
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation for cytoplasm. Cytoplasmic localization is the primary constitutive location of CRYAA, confirmed by multiple IDA-level studies (PMID:19464326, PMID:29259299, PMID:19503744, PMID:14752512, etc.) and UniProt subcellular location annotation. The IEA mapping is correct. Reason: Cytoplasm is the primary constitutive localization of CRYAA, well supported by multiple independent studies. The IEA is consistent with IBA and IDA annotations.
GO:0007601 visual perception	IEA GO_REF:0000043	MARK AS OVER ANNOTATED	Summary: IEA annotation for visual perception based on UniProt keyword mapping. CRYAA is essential for lens transparency, and mutations cause cataracts that impair vision (PMID:9467006, PMID:14512969). However, CRYAA does not directly participate in the visual perception signaling pathway (phototransduction). Rather, it maintains the structural integrity of the lens through which light passes. This term is somewhat over-annotated as it implies a role in visual signaling rather than lens maintenance. Reason: While CRYAA is essential for lens transparency and mutations cause cataracts that impair vision, the term "visual perception" implies involvement in the phototransduction/visual signaling pathway. CRYAA contributes to vision indirectly by maintaining lens structure, not by participating in the perception process itself. GO:0002088 "lens development in camera-type eye" and GO:0005212 "structural constituent of eye lens" better capture the actual role.
GO:0046872 metal ion binding	IEA GO_REF:0000043	MODIFY	Summary: IEA annotation for metal ion binding from UniProt keyword mapping. UniProt documents that CRYAA binds zinc ions, with the zinc-binding motif created from residues of 3 different molecules (His-100, Glu-102 from one molecule; His-107 and His-154 from additional molecules) to create tetrahedral coordination geometry (PMID:22890888). Inter-subunit bridging via zinc ions enhances oligomer stability. This is a legitimate but generic annotation; a more specific term like "zinc ion binding" (GO:0008270) would be more informative. Reason: Metal ion binding is too generic. The specific metal bound is zinc, which is important for oligomer stability (PMID:22890888 via UniProt). GO:0008270 "zinc ion binding" would be more informative. Proposed replacements: zinc ion binding
GO:0005515 protein binding	IPI PMID:11700327 Detection of protein-protein interactions among lens crystal...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:11700327. This study used a mammalian two-hybrid system to detect interactions between alphaA-crystallin and other lens crystallins (alphaB-, betaB2-, and gammaC-crystallin) and Hsp27 in HeLa cells. The interactions between alpha- crystallins and beta/gamma-crystallins were about one-third the intensity of alphaA-alphaB interactions. While the interactions are real and functionally relevant (crystallin-crystallin interactions maintain lens transparency), "protein binding" is uninformative. Reason: "Protein binding" is too vague. The actual interactions detected are crystallin-crystallin interactions, not direct evidence for a specific molecular-function replacement. CRYAA holdase activity is supported by aggregation-suppression assays elsewhere; this two-hybrid interaction record should not be used to infer a chaperone term. Supporting Evidence: PMID:11700327 there were interactions between alphaA- (or alphaB-) and betaB2- or gammaC-crystallins but with an intensity of one-third that of alphaA-alphaB interactions
GO:0005515 protein binding	IPI PMID:12601044 Alteration of protein-protein interactions of congenital cat...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:12601044. This study used the mammalian two-hybrid system to show that cataract-causing R116C alphaA-crystallin mutant has altered protein-protein interactions with crystallins. The wild-type CRYAA interactions with betaB2- and gammaC-crystallin decreased in the R116C mutant, while interactions with alphaB-crystallin and Hsp27 increased. "Protein binding" is uninformative for the functional context. Reason: "Protein binding" is too generic. The crystallin-crystallin interactions documented are functionally relevant to lens protein organization, but altered two-hybrid interactions in a cataract mutant are not direct evidence for a chaperone molecular-function replacement. Keep the mechanistic context without treating generic protein binding as a core function. Supporting Evidence: PMID:12601044 for the R116C alphaA-crystallin, the interactions with betaB2- and gammaC-crystallin decreased and those with alphaB-crystallin and heat-shock protein (Hsp)27 increased
GO:0005515 protein binding	IPI PMID:19651604 The eye lens chaperone alpha-crystallin forms defined globul...	MODIFY	Summary: IPI annotation for protein binding from PMID:19651604. This study analyzed quaternary structures of alpha-crystallins and showed that alphaA-crystallin forms defined oligomers of 24 subunits as well as smaller oligomers and large clusters. The protein-protein interactions documented here are oligomerization (homo- and hetero-oligomerization with CRYAB), which is intrinsic to the structural and chaperone function. "Protein binding" is uninformative. Reason: "Protein binding" is too vague. The interactions are homo-oligomerization and hetero- oligomerization relevant to CRYAA structural and chaperone function. GO:0042802 "identical protein binding" is already annotated from this reference, which is more specific. Proposed replacements: identical protein binding Supporting Evidence: PMID:19651604 alphaA-Crystallin forms, in addition to complexes of 24 subunits, also smaller oligomers and large clusters consisting of individual oligomers
GO:0005515 protein binding	IPI PMID:22085609 Temperature-dependent structural and functional properties o...	MODIFY	Summary: IPI annotation for protein binding from PMID:22085609, which studied the F71L mutant of alphaA-crystallin. This study examined structural and functional properties of the cataract- causing mutant. The interactions documented are likely crystallin oligomerization relevant to the chaperone function. "Protein binding" is uninformative. Reason: "Protein binding" is too generic. The interactions documented in this paper are crystallin self-interactions (oligomerization) relevant to chaperone function. GO:0042802 "identical protein binding" is already annotated from this reference. Proposed replacements: identical protein binding
GO:0005515 protein binding	IPI PMID:22153508 The polydispersity of αB-crystallin is rationalized by an in...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:22153508, which studied the polyhedral architecture of alphaB-crystallin. While primarily focused on CRYAB, interactions with CRYAA may have been detected in this study. "Protein binding" is uninformative and should be replaced with more specific terms for the alpha-crystallin hetero-oligomerization. Reason: "Protein binding" is too vague. The context is alpha-crystallin oligomerization. A more specific term describing hetero-oligomerization or structural complex formation would be more informative, but GO:0042802 should not be used here because this row is not specific to CRYAA self-interaction.
GO:0005515 protein binding	IPI PMID:23188086 Binding determinants of the small heat shock protein, αB-cry...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:23188086. This study investigated binding determinants of alphaB-crystallin, specifically recognition of the IxI motif. The IxI motif is important for sHSP oligomerization and substrate interaction. Interactions with CRYAA would be in the context of hetero-oligomerization. "Protein binding" is uninformative. Reason: "Protein binding" is too vague. The context is sHSP subunit interactions via the IxI motif, relevant to hetero-oligomerization with CRYAB rather than identical CRYAA self-binding.
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:25416956 (proteome-scale interactome map). This is a high-throughput study. "Protein binding" from high-throughput interactome studies is uninformative and lacks the context of specific functional interactions. Reason: "Protein binding" from high-throughput interactome mapping is too generic. CRYAA is known to form homo- and hetero-oligomers, but this broad interactome row is not specific enough to justify replacing the annotation with identical protein binding.
GO:0005515 protein binding	IPI PMID:25910212 Widespread macromolecular interaction perturbations in human...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:25910212 (macromolecular interaction perturbations in human genetic disorders). This is a high-throughput study examining how disease-associated mutations perturb protein interactions. "Protein binding" from such studies is uninformative. Reason: "Protein binding" from a high-throughput interaction perturbation study does not tell us anything specific about CRYAA function. The actual molecular functions (chaperone holdase, structural lens protein, oligomerization) are better captured by other annotations.
GO:0005515 protein binding	IPI PMID:29892012 An interactome perturbation framework prioritizes damaging m...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:29892012 (interactome perturbation framework for developmental disorders). This is a high-throughput study. "Protein binding" is uninformative. Reason: "Protein binding" from a high-throughput interactome perturbation study is too generic to be informative about CRYAA function.
GO:0005515 protein binding	IPI PMID:31515488 Extensive disruption of protein interactions by genetic vari...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:31515488 (disruption of protein interactions by genetic variants). This is a high-throughput study examining interaction perturbations. "Protein binding" is uninformative. Reason: "Protein binding" from high-throughput variant effect mapping is too generic.
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:32296183 (reference map of human binary protein interactome). This is a high-throughput interactome mapping study. "Protein binding" is uninformative. GO:0042802 is already annotated from this same reference. Reason: "Protein binding" is too vague. Although GO:0042802 "identical protein binding" is annotated separately from this reference, this broad interactome protein-binding row should not itself be converted to a self-interaction assertion.
GO:0005515 protein binding	IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:32814053 (interactome mapping of neurodegenerative disease proteins). This is a high-throughput study. "Protein binding" is uninformative. Reason: "Protein binding" from a high-throughput neurodegenerative disease interactome study is too generic. The finding that CRYAA interacts with disease-associated proteins could be relevant to its chaperone holdase function but "protein binding" does not capture this.
GO:0005515 protein binding	IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:33961781 (dual proteome-scale networks for cell-specific interactome). This is a high-throughput study. "Protein binding" is uninformative. Reason: "Protein binding" from a high-throughput proteome-scale interactome study is too generic.
GO:0042802 identical protein binding	IPI PMID:12601044 Alteration of protein-protein interactions of congenital cat...	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:12601044. This study demonstrated alphaA-crystallin self-interaction using a mammalian two-hybrid system, showing that the R116C cataract mutant had altered self-interaction. Self-interaction (homo-oligomerization) is a core property of CRYAA -- it forms homodimers and homotetramers as building blocks of larger homo-oligomers (UniProt). This annotation appropriately captures the self-interaction property. Reason: CRYAA homo-oligomerization is a core structural property essential for both its lens structural role and chaperone function. The R116C cataract mutation alters this self- interaction (PMID:12601044), confirming functional importance. Supporting Evidence: PMID:12601044 for the R116C alphaA-crystallin, the interactions with betaB2- and gammaC-crystallin decreased and those with alphaB-crystallin and heat-shock protein (Hsp)27 increased
GO:0042802 identical protein binding	IPI PMID:19651604 The eye lens chaperone alpha-crystallin forms defined globul...	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:19651604. This study demonstrated that alphaA-crystallin forms defined oligomers of 24 subunits as well as smaller oligomers and large clusters using biophysical methods and electron microscopy. The self-interaction (homo-oligomerization) is directly demonstrated. Reason: CRYAA homo-oligomerization is directly demonstrated by biophysical analysis showing 24-subunit oligomers (PMID:19651604). This is a core property of the protein. Supporting Evidence: PMID:19651604 alphaA-Crystallin forms, in addition to complexes of 24 subunits, also smaller oligomers and large clusters consisting of individual oligomers
GO:0042802 identical protein binding	IPI PMID:22085609 Temperature-dependent structural and functional properties o...	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:22085609. The F71L cataract-causing mutant study examined structural and functional properties including oligomerization. Self-interaction of CRYAA is documented. Reason: Self-interaction (homo-oligomerization) is a core property of CRYAA confirmed by multiple studies. The F71L mutant study provides additional evidence.
GO:0042802 identical protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:25416956 (proteome-scale interactome map). CRYAA-CRYAA self-interaction is documented in this high-throughput study. UniProt lists 12 experiments supporting CRYAA self-interaction (IntAct). While from a high- throughput study, the self-interaction is well validated by targeted studies. Reason: CRYAA homo-oligomerization is well documented. The high-throughput detection confirms targeted studies. UniProt lists 12 experiments for CRYAA-CRYAA interaction.
GO:0042802 identical protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:32296183 (reference map of human binary protein interactome). CRYAA self-interaction detected in this systematic study. Consistent with extensive prior evidence for homo-oligomerization. Reason: CRYAA homo-oligomerization is a well-established core property, and this high-throughput study provides consistent confirmatory evidence.
GO:0005654 nucleoplasm	IDA GO_REF:0000052	KEEP AS NON CORE	Summary: IDA annotation for nucleoplasm based on curation of immunofluorescence data (GO_REF:0000052). PMID:19464326 showed that CRYAA (HSPB4) translocates to the nucleus during heat shock and resides in SC35 speckles, which are nuclear sub-structures within the nucleoplasm. The nucleoplasm localization is consistent with this stress-dependent translocation. Reason: Nucleoplasm localization is supported by evidence of heat-shock-induced translocation to SC35 speckles (PMID:19464326). However, this is a stress-dependent secondary localization, not the primary constitutive location.
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: IDA annotation for cytosol based on curation of immunofluorescence data (GO_REF:0000052). CRYAA is a soluble cytoplasmic protein that exists free in the cytosol as oligomeric complexes. Multiple studies show uniform cytoplasmic distribution (PMID:29259299, PMID:19503744). Cytosol is a more specific sub-compartment of cytoplasm and is consistent with the known biology. Reason: Cytosol is the primary constitutive location of CRYAA, where it exists as soluble oligomeric complexes. Consistent with multiple IDA studies showing cytoplasmic distribution.
GO:0005737 cytoplasm	IDA PMID:29259299 Two novel mutations identified in ADCC families impair cryst...	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:29259299. This study used fluorescence microscopy of GFP-tagged wild-type alphaA-crystallin in human lens epithelial cells and showed that wild-type CRYAA was equally distributed in the cytoplasm. The mutant (p.116_118del) accumulated at the nuclear peripheral membrane. Reason: Direct fluorescence microscopy evidence showing wild-type CRYAA is uniformly distributed in the cytoplasm of human lens epithelial cells (PMID:29259299). Supporting Evidence: PMID:29259299 Wild-type alphaA-crystallin was also equally distributed in the cytoplasm
GO:0005737 cytoplasm	IDA PMID:26004348 Mutation analysis of two families with inherited congenital ...	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:26004348. This study on congenital cataract families included subcellular localization analysis. UniProt lists this as a supporting reference for cytoplasmic localization. Reason: Cytoplasmic localization supported by localization data from PMID:26004348, consistent with the primary constitutive location of CRYAA.
GO:0005737 cytoplasm	IDA PMID:19503744 An alphaA-crystallin gene mutation, Arg12Cys, causing inheri...	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:19503744. This study on the R12C alphaA-crystallin mutation characterized subcellular localization. UniProt lists this as supporting evidence for cytoplasmic localization. Reason: Cytoplasmic localization is documented as the primary location in this study of the R12C mutant, consistent with multiple other studies.
GO:0005737 cytoplasm	IDA PMID:30340470 A novel mutation in the CRYAA gene associated with congenita...	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:30340470. This study on a novel CRYAA mutation (congenital cataract and microphthalmia) included subcellular localization analysis. UniProt lists this as supporting evidence for cytoplasmic localization. Reason: Cytoplasmic localization confirmed by this cataract mutation study, consistent with the known primary location of CRYAA.
GO:0005198 structural molecule activity	IDA PMID:16303126 Lenticular chaperones suppress the aggregation of the catara...	MODIFY	Summary: IDA annotation for structural molecule activity from PMID:16303126. This study showed that alpha-crystallins (alphaA- and alphaB-) suppress aggregation of the cataract-causing T5P gammaC-crystallin mutant both in vitro and in transfected cells. The study demonstrated a dual role: increasing solubility and reducing aggregate size. However, "structural molecule activity" is not the best descriptor for this chaperone function. The paper is really about chaperone holdase activity, not structural function per se. The more specific term GO:0005212 "structural constituent of eye lens" better captures the structural role. Reason: The evidence in PMID:16303126 is about chaperone holdase activity (suppressing aggregation of T5P gammaC-crystallin), not structural molecule activity per se. An in-situ holdase activity term would better capture the molecular function demonstrated, but none exists: GO:0140309 is carrier-specific (escorting between cellular components, per go-ontology#30552) and GO:0044183 is foldase-specific. For the true structural role, GO:0005212 is already annotated. Proposed replacements: holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific) Supporting Evidence: PMID:16303126 the major lenticular protein chaperones, alpha A- and alpha B-crystallin, increased the solubility of the T5P gamma C-crystallin both in vitro and in transfected cells PMID:16303126 the size of the T5P gamma C-crystallin aggregates were also significantly reduced in the presence of the lenticular chaperones
GO:0032991 protein-containing complex	IDA PMID:16303126 Lenticular chaperones suppress the aggregation of the catara...	ACCEPT	Summary: IDA annotation for protein-containing complex from PMID:16303126. CRYAA forms large oligomeric complexes of approximately 540 kDa (PMID:8943244). UniProt documents that CRYAA forms heteropolymers (3 CRYAA : 1 CRYAB), homodimers, homotetramers, and larger homo-oligomers. It is also part of a complex with BFSP1 and BFSP2 for lens intermediate filament formation. The protein-containing complex annotation is correct but very generic. Reason: CRYAA forms large homo- and hetero-oligomeric complexes as a core feature of its biology. The annotation is correct, though generic. The oligomeric complex is essential for both structural and chaperone functions. Supporting Evidence: PMID:8943244 aggregates of approximately 540 kDa were formed from a tryptophan-free alphaA mutant (W9F) PMID:16303126 the major lenticular protein chaperones, alpha A- and alpha B-crystallin, increased the solubility of the T5P gamma C-crystallin both in vitro and in transfected cells
GO:0042802 identical protein binding	IPI PMID:16303126 Lenticular chaperones suppress the aggregation of the catara...	ACCEPT	Summary: IPI annotation for identical protein binding from PMID:16303126. This study used both in vitro sedimentation assays and cell transfection to demonstrate that alpha-crystallins form complexes. CRYAA homo-oligomerization is well established and essential for function. Reason: CRYAA homo-oligomerization is a core property demonstrated in this study and many others. The self-interaction is essential for forming the large oligomeric complexes required for both structural and chaperone functions.
GO:0005515 protein binding	IPI PMID:12235146 Role of the C-terminal extensions of alpha-crystallins. Swap...	MODIFY	Summary: IPI annotation for protein binding from PMID:12235146. This study investigated the role of C-terminal extensions of alphaA- and alphaB-crystallins by domain swapping, demonstrating that the C-terminal extension plays a crucial role in structure and chaperone activity. The protein-protein interactions are alphaA-alphaB hetero-oligomerization. "Protein binding" is too generic. Reason: "Protein binding" is uninformative. The interactions documented are alpha-crystallin subunit interactions (hetero-oligomerization) relevant to chaperone function. An in-situ holdase activity term would better capture the molecular function demonstrated by the chaperone activity assays used, but none exists: GO:0140309 is carrier-specific (per go-ontology#30552) and GO:0044183 is foldase-specific. GO:0042802 "identical protein binding" already captures the hetero-oligomerization aspect. Proposed replacements: holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific) Supporting Evidence: PMID:12235146 Our study demonstrates that the unstructured C-terminal extensions play a crucial role in the structure and chaperone activity, in addition to generally believed electrostatic "solubilizer" function
GO:0050821 protein stabilization	IMP PMID:12235146 Role of the C-terminal extensions of alpha-crystallins. Swap...	ACCEPT	Summary: IMP annotation for protein stabilization from PMID:12235146. This study showed that domain-swapped chimeras of alphaA and alphaB crystallins have dramatically altered chaperone-like activity -- the chimeric alphaB with CRYAA C-terminal extension showed enhanced chaperone activity while the chimeric alphaA with CRYAB C-terminal extension almost lost activity. This demonstrates that CRYAA contributes to protein stabilization (preventing aggregation of destabilized proteins). GO:0050821 "protein stabilization" is defined as "any process involved in maintaining the structure and integrity of a protein and preventing it from degradation or aggregation." This is an excellent fit for CRYAA holdase activity. Reason: GO:0050821 "protein stabilization" accurately describes the core holdase function of CRYAA -- preventing aggregation and maintaining protein integrity. The evidence from PMID:12235146 demonstrates that the C-terminal extension of CRYAA is crucial for this function. This is one of the most appropriate BP terms for the CRYAA holdase chaperone activity. Supporting Evidence: PMID:12235146 the chimeric alphaB with the C-terminal extension of alphaA-crystallin, alphaBAc, exhibits dramatically enhanced chaperone-like activity PMID:12235146 the unstructured C-terminal extensions play a crucial role in the structure and chaperone activity
GO:0005634 nucleus	IDA PMID:19464326 HSPB7 is a SC35 speckle resident small heat shock protein.	KEEP AS NON CORE	Summary: IDA annotation for nucleus from PMID:19464326. The cached abstract excerpt available here is about HSPB7, so explicit text support is taken from the UniProt CRYAA subcellular-location statement, which records heat-shock-induced nuclear translocation to SC35 splicing speckles. While not the primary constitutive localization, the stress-induced nuclear translocation is experimentally documented in the UniProt record. Reason: Nuclear localization is stress-induced (heat shock) rather than constitutive. CRYAA resides in SC35 speckles under stress conditions. This is a secondary localization. Supporting Evidence: UniProtKB:P02489 Nucleus. Note=Translocates to the nucleus during heat shock and resides in sub-nuclear structures known as SC35 speckles or nuclear splicing speckles.
GO:0005737 cytoplasm	IDA PMID:19464326 HSPB7 is a SC35 speckle resident small heat shock protein.	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:19464326. This study used confocal microscopy to characterize subcellular localization of HSPB family members and showed CRYAA (HSPB4) in the cytoplasm under basal conditions. Reason: Cytoplasmic localization is directly demonstrated by confocal microscopy in PMID:19464326, consistent with the primary constitutive location of CRYAA.
GO:0005515 protein binding	IPI PMID:14752512 Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S...	MARK AS OVER ANNOTATED	Summary: IPI annotation for protein binding from PMID:14752512. This study demonstrated by GST pulldown and coimmunoprecipitation that alphaA-crystallin binds to pro-apoptotic Bax and Bcl-X(S) proteins both in vitro and in vivo, preventing their translocation to mitochondria during staurosporine-induced apoptosis. The R116C cataract mutant showed much weaker affinity. "Protein binding" is uninformative for this specific anti-apoptotic binding activity. Reason: "Protein binding" is too generic. The specific interaction is binding to pro-apoptotic Bax and Bcl-X(S) to sequester them and prevent apoptosis. This is better captured by the negative regulation of apoptotic process annotation (GO:0043066) already present. No single MF term perfectly captures anti-apoptotic binding, but the IPI evidence supports the GO:0043066 BP annotation. Supporting Evidence: PMID:14752512 Using GST pulldown assays and coimmunoprecipitations, we demonstrated that alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo PMID:14752512 Through the interaction, alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis
GO:0042026 protein refolding	ISS NOT GO_REF:0000024	KEEP AS NON CORE	Summary: NOT annotation for protein refolding (ISS from bovine ortholog via GO_REF:0000024). This is a critical annotation that explicitly states CRYAA does NOT perform protein refolding. CRYAA is a holdase chaperone that prevents aggregation of denatured proteins but does not actively refold them. This is consistent with all experimental evidence: PMID:8943244 describes the chaperone-like activity as "the ability to suppress nonspecific aggregation" with no mention of refolding capability. The negated GOA assertion is therefore consistent with CRYAA being a holdase without foldase activity. This NOT annotation should be retained because it records the biologically important distinction between CRYAA holdase activity and active protein refolding. Reason: The negated annotation correctly states that CRYAA does not perform active protein refolding. Retaining this NOT assertion is useful because it prevents propagation of a foldase interpretation and because it rules out GO:0044183 "protein folding chaperone" as the replacement for the obsolete GO:0051082. Supporting Evidence: PMID:8943244 alpha-crystallin subunits associate to form large oligomeric aggregates that express chaperone-like activity, as defined by the ability to suppress nonspecific aggregation of proteins destabilized by treatment with a variety of denaturants
GO:0051082 unfolded protein binding	IPI PMID:8943244 Cloning, expression, and chaperone-like activity of human al...	MODIFY	Summary: GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962). This IPI annotation is based on PMID:8943244, which demonstrated that recombinant human alphaA-crystallin (CRYAA) suppresses heat-induced aggregation of aldose reductase (UniProtKB:P07320, the WITH/FROM interactor) and singlet-oxygen-induced aggregation of gamma-crystallin in stoichiometric amounts. The paper explicitly defines this as "chaperone-like activity" meaning the ability to suppress nonspecific aggregation of destabilized proteins. The C-terminal truncation mutant (R157STOP) showed markedly reduced chaperone-like activity despite preserved secondary structure, confirming that the C-terminal region is essential for the holdase function. The experimental evidence clearly supports that CRYAA binds partially denatured proteins and prevents their aggregation, which is holdase (not foldase) activity. No adequate MF replacement term yet exists: GO:0140309 is carrier-specific (escorting between cellular components, per go-ontology#30552) and GO:0044183 is foldase-specific, so GO:0051082 is retained as an interim annotation pending a general holdase chaperone activity NTR. Reason: GO:0051082 is now formally obsolete. The experimental evidence from PMID:8943244 clearly demonstrates holdase chaperone activity -- CRYAA suppresses aggregation of heat-denatured aldose reductase and singlet-oxygen-damaged gamma-crystallin. This is not "unfolded protein binding" in a passive sense; it is active suppression of aggregation. The IPI evidence (with aldose reductase UniProtKB:P07320 as interactor) is strong. Neither obsoletion-replacement candidate fits: GO:0044183 requires assisting folding, which CRYAA does not do, and GO:0140309 requires escorting the client to a destination, which CRYAA does not do. Retain GO:0051082 as interim until a holdase chaperone activity NTR exists. GO:0050821 "protein stabilization" is also relevant as a BP term. Proposed replacements: holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific) Supporting Evidence: PMID:8943244 alpha-crystallin subunits associate to form large oligomeric aggregates that express chaperone-like activity, as defined by the ability to suppress nonspecific aggregation of proteins destabilized by treatment with a variety of denaturants including heat, UV irradiation, and chemical modification PMID:8943244 When added in stoichiometric amounts, both WT and W9F subunits completely suppressed the heat-induced aggregation of aldose reductase PMID:8943244 subunits encoded by a truncation mutant in which the C-terminal 17 residues were deleted (R157STOP), despite having spectroscopic properties similar to WT, formed much larger aggregates with a marked reduction in chaperone-like activity
GO:0007601 visual perception	IMP PMID:9467006 Autosomal dominant congenital cataract associated with a mis...	MARK AS OVER ANNOTATED	Summary: IMP annotation for visual perception from PMID:9467006. This study identified the R116C missense mutation in CRYAA as causing autosomal dominant congenital cataract (ADCC) in a family. The logic is that mutation in CRYAA causes cataract, which impairs visual perception. However, CRYAA does not directly participate in phototransduction or visual signaling. It maintains lens transparency, which is a prerequisite for vision but not part of the perception pathway itself. The IMP evidence connects CRYAA to visual impairment through lens opacity, not through a direct role in visual perception. Reason: While CRYAA mutations cause cataracts that impair vision (PMID:9467006), CRYAA does not participate in the visual perception signaling pathway. It maintains lens structural integrity. GO:0002088 "lens development in camera-type eye" and GO:0005212 "structural constituent of eye lens" better capture the role. Marking as over-annotated because the connection to visual perception is indirect. Supporting Evidence: PMID:9467006 we found that a missense mutation, R116C, is associated with ADCC in this family
GO:0043066 negative regulation of apoptotic process	IMP PMID:14512969 Cell death triggered by a novel mutation in the alphaA-cryst...	KEEP AS NON CORE	Summary: IMP annotation for negative regulation of apoptotic process from PMID:14512969. This study identified the R49C mutation in CRYAA and showed that the R49C mutant protein failed to protect lens epithelial cells from staurosporine-induced apoptotic cell death, whereas wild-type CRYAA did protect. The IMP logic is that loss-of-function mutation leads to failure to suppress apoptosis, implicating wild-type CRYAA in negative regulation of apoptosis. This is well-supported anti-apoptotic activity, consistent with the IBA and IDA annotations to the same term. Reason: Anti-apoptotic function is well demonstrated by mutant phenotype: the R49C mutant fails to protect from staurosporine-induced apoptosis (PMID:14512969). This is a secondary function compared to the core structural and chaperone holdase roles. Supporting Evidence: PMID:14512969 unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to the nucleus and failed to protect from staurosporine-induced apoptotic cell death
GO:0051082 unfolded protein binding	IMP PMID:18407550 A novel mutation in AlphaA-crystallin (CRYAA) caused autosom...	MODIFY	Summary: GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962). This IMP annotation is based on PMID:18407550, which identified the R116H (c.346G>A) mutation in CRYAA as the cause of autosomal dominant congenital cataract in a large Chinese family. The mutant phenotype evidence is that the R116H mutant protein showed loss of chaperone activity in the DTT-induced insulin aggregation assay, increased hydrophobicity, and increased binding affinity to lysozyme. The logic is: mutation in CRYAA causes loss of chaperone (holdase) activity, leading to cataract, therefore wild-type CRYAA enables this chaperone function. This is valid IMP evidence for chaperone holdase activity. However, the term "unfolded protein binding" does not accurately capture the functional consequence measured, which is suppression of protein aggregation (holdase activity). No adequate replacement exists yet -- GO:0140309 is carrier-specific and GO:0044183 is foldase-specific -- so GO:0051082 is retained as interim. Reason: GO:0051082 is now formally obsolete. The IMP evidence from PMID:18407550 is based on the R116H cataract-causing mutation showing loss of chaperone activity in DTT-induced insulin aggregation assay. This demonstrates the functional importance of CRYAA holdase activity but the term "unfolded protein binding" mischaracterizes the function. Neither obsoletion-replacement candidate is correct: GO:0140309 is carrier-specific (escorting between cellular components, per go-ontology#30552) and GO:0044183 requires assisting folding. Retain GO:0051082 as an interim annotation until a general holdase chaperone activity NTR is created. Proposed replacements: holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific) Supporting Evidence: PMID:18407550 loss of chaperone activity of the mutant was seen in DTT (DL-dithiothreitol)-induced insulin aggregation assay PMID:18407550 Gain of activated lysozyme binding, elevation of hydrophobicity and loss of chaperone activity of the mutant protein may be some of the molecular mechanisms underlying cataract in this large family PMID:18407550 Sequencing of CRYAA revealed a novel heterozygous G>A transition (c.346G>A) in exon 3 that cosegregated with the disease phenotype and results in a conservative substitution of Arg to His at codon 116 (p.R116H)
GO:0005737 cytoplasm	IDA PMID:14752512 Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S...	ACCEPT	Summary: IDA annotation for cytoplasm from PMID:14752512. This study demonstrated that alphaA- and alphaB-crystallins reside in the cytosol and prevent the translocation of pro-apoptotic Bax and Bcl-X(S) from cytosol to mitochondria during staurosporine-induced apoptosis. The abstract states that "alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis" (PMID:14752512), implying CRYAA co-localizes with these targets in the cytoplasm. This is consistent with multiple other IDA studies confirming cytoplasmic localization (PMID:29259299, PMID:19464326, PMID:19503744, PMID:26004348, PMID:30340470). Reason: Cytoplasmic localization is the primary constitutive location of CRYAA. PMID:14752512 demonstrates CRYAA in the cytosol where it interacts with and sequesters Bax and Bcl-X(S). This is consistent with all other localization studies and represents a core annotation. Supporting Evidence: PMID:14752512 alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis
GO:0032387 negative regulation of intracellular transport	IDA PMID:14752512 Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S...	KEEP AS NON CORE	Summary: IDA annotation for negative regulation of intracellular transport from PMID:14752512. This study demonstrated using GST pulldown assays and coimmunoprecipitation that alphaA- and alphaB-crystallins bind to pro-apoptotic Bax and Bcl-X(S) both in vitro and in vivo, and "prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis" (PMID:14752512). This is a specific form of negative regulation of intracellular transport -- CRYAA sequesters these proteins in the cytosol, preventing their mitochondrial translocation. The cataract-causing R116C mutant shows "much weaker affinity to Bax and Bcl-X(S)" (PMID:14752512), further supporting that wild-type CRYAA actively prevents this transport. This is a secondary, non-core function tied to the anti-apoptotic role rather than the primary structural or chaperone holdase functions. Reason: The annotation is well supported by direct experimental evidence from PMID:14752512 showing that CRYAA prevents translocation of Bax and Bcl-X(S) from cytosol to mitochondria. However, this is a secondary function tied to the anti-apoptotic role, not the core structural or chaperone holdase activity of CRYAA. Marked as non-core for consistency with the anti-apoptotic annotations (GO:0043066). Supporting Evidence: PMID:14752512 Through the interaction, alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis PMID:14752512 Two prominent mutants, R116C in alphaA-crystallin and R120G, in alphaB-crystallin display much weaker affinity to Bax and Bcl-X(S)
GO:0043066 negative regulation of apoptotic process	IDA PMID:14752512 Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S...	KEEP AS NON CORE	Summary: IDA annotation for negative regulation of apoptotic process from PMID:14752512. This study directly demonstrated that "Human alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis through interactions with members of the Bcl-2 family" (PMID:14752512). Using GST pulldown and coimmunoprecipitation, the authors showed that alpha-crystallins bind to pro-apoptotic Bax and Bcl-X(S) both in vitro and in vivo, sequestering them in the cytosol and preventing their translocation to mitochondria. As a result, "alpha-crystallins preserve the integrity of mitochondria, restrict release of cytochrome c, repress activation of caspase-3 and block degradation of PARP" (PMID:14752512). The anti-apoptotic function was confirmed in human lens epithelial cells, ARPE-19 cells, and H9c2 cells under staurosporine, etoposide, or sorbitol treatment. The R116C cataract mutant showed much weaker affinity to Bax and Bcl-X(S), consistent with loss of anti-apoptotic activity contributing to cataract pathology. This is a well- documented secondary function of CRYAA beyond its primary structural and chaperone roles. Reason: Anti-apoptotic activity of CRYAA is directly demonstrated by IDA evidence in PMID:14752512 using multiple experimental approaches (GST pulldown, coimmunoprecipitation, functional apoptosis assays in multiple cell types). However, this is a secondary function compared to the core structural lens protein and chaperone holdase roles. Marked as non-core for consistency with the IBA and IMP annotations for the same GO term. Supporting Evidence: PMID:14752512 Human alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis through interactions with members of the Bcl-2 family PMID:14752512 Using GST pulldown assays and coimmunoprecipitations, we demonstrated that alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo PMID:14752512 alpha-crystallins preserve the integrity of mitochondria, restrict release of cytochrome c, repress activation of caspase-3 and block degradation of PARP
GO:0007601 visual perception	IMP PMID:14512969 Cell death triggered by a novel mutation in the alphaA-cryst...	MARK AS OVER ANNOTATED	Summary: IMP annotation for visual perception from PMID:14512969. This study identified the R49C missense mutation in CRYAA as causing autosomal dominant "nuclear" cataract in a four- generation family. The mutant protein "was abnormally localized to the nucleus and failed to protect from staurosporine-induced apoptotic cell death" (PMID:14512969). The logic connecting CRYAA to visual perception is that the R49C mutation causes cataract (lens opacity), which impairs vision. However, CRYAA does not directly participate in the visual perception signaling pathway (phototransduction). It maintains lens structural integrity and transparency, which is a prerequisite for light transmission but not part of the perception process itself. GO:0002088 "lens development in camera-type eye" and GO:0005212 "structural constituent of eye lens" more accurately capture the actual role. This is the same over-annotation issue identified for the IEA (GO_REF:0000043) and IMP (PMID:9467006) visual perception annotations already reviewed. Reason: While the R49C CRYAA mutation causes autosomal dominant cataract that impairs vision (PMID:14512969), CRYAA does not participate in the visual perception signaling pathway. It maintains lens transparency through its structural and chaperone roles. The connection to visual perception is indirect -- through lens opacity rather than involvement in phototransduction. GO:0002088 "lens development in camera-type eye" and GO:0005212 "structural constituent of eye lens" better capture the actual function. Consistent with the assessment of the other visual perception annotations for CRYAA. Supporting Evidence: PMID:14512969 unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to the nucleus and failed to protect from staurosporine-induced apoptotic cell death PMID:14512969 Hereditary cataract is a clinically and genetically heterogeneous lens disease that accounts for a significant proportion of visual impairment and blindness in childhood

Core Functions

CRYAA (HSPB4) is a small heat shock protein that functions as an ATP-independent holdase chaperone. It forms large homo-oligomeric complexes (~540 kDa, ~24 subunits) that suppress nonspecific aggregation of proteins destabilized by heat, UV irradiation, and chemical modification. CRYAA does NOT actively refold substrates (documented by NOT annotation to GO:0042026 protein refolding). It maintains denatured proteins in a soluble, non-aggregated state. The C-terminal extension is essential for chaperone activity, and the T148 phosphorylation site (mediated by mTORC2) regulates chaperone capacity. Disease-causing mutations (R116C, R116H, R49C, F71L) impair chaperone holdase activity and cause congenital cataracts. GO:0051082 is used here as an INTERIM molecular function: it is formally obsolete, but neither offered replacement fits an in-situ holdase -- GO:0044183 "protein folding chaperone" requires assisting folding, and GO:0140309 (relabelled "unfolded protein holdase activity" but with an unchanged carrier-specific definition, child of GO:0140597 "protein carrier chaperone") requires escorting the client to a destination. A general "holdase chaperone activity" NTR is needed; see projects/UNFOLDED_PROTEIN_BINDING.md and go-ontology#30552.

Molecular Function:

unfolded protein binding

Directly Involved In:

protein stabilization response to heat

Cellular Locations:

cytosol

Supporting Evidence:

PMID:8943244
alpha-crystallin subunits associate to form large oligomeric aggregates that express chaperone-like activity, as defined by the ability to suppress nonspecific aggregation of proteins destabilized by treatment with a variety of denaturants including heat, UV irradiation, and chemical modification.
PMID:12235146
the chimeric alphaB with the C-terminal extension of alphaA-crystallin exhibits dramatically enhanced chaperone-like activity.
PMID:18407550
loss of chaperone activity of the mutant was seen in DTT-induced insulin aggregation assay.

CRYAA is the most abundantly expressed protein in the ocular lens, contributing to lens transparency and refractive index. It serves a dual role as a structural protein providing the high-concentration protein matrix required for lens transparency, and as a chaperone preventing aggregation of damaged crystallins that would cause light-scattering opacification. CRYAA hetero-oligomerizes with CRYAB (HSPB5) in a 3:1 ratio. Mutations in CRYAA consistently cause autosomal dominant congenital cataracts (ADCC), confirming its essential structural role.

Molecular Function:

structural constituent of eye lens

Directly Involved In:

lens development in camera-type eye

Cellular Locations:

cytosol

Supporting Evidence:

PMID:14512969
The alphaA-crystallin (CRYAA) gene (CRYAA) encodes a member of the small-heat-shock protein (sHSP) family of molecular chaperones and is primarily and abundantly expressed in the ocular lens
PMID:9467006
we found that a missense mutation, R116C, is associated with ADCC in this family.
PMID:16303126
the major lenticular protein chaperones, alpha A- and alpha B-crystallin, increased the solubility of the T5P gamma C-crystallin both in vitro and in transfected cells.

References

UniProtKB:P02489

UniProtKB entry for human CRYAA (Alpha-crystallin A chain)

UniProt records CRYAA as cytoplasmic and stress-induced nuclear, with heat-shock-dependent residence in SC35/nuclear splicing speckles.

"Nucleus. Note=Translocates to the nucleus during heat shock and resides in sub-nuclear structures known as SC35 speckles or nuclear splicing speckles."

GO_REF:0000024

Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000052

Gene Ontology annotation based on curation of immunofluorescence data

GO_REF:0000117

Electronic Gene Ontology annotations created by ARBA machine learning models

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:11700327

Detection of protein-protein interactions among lens crystallins in a mammalian two-hybrid system assay.

PMID:12235146

Role of the C-terminal extensions of alpha-crystallins. Swapping the C-terminal extension of alpha-crystallin to alphaB-crystallin results in enhanced chaperone activity.

PMID:12601044

Alteration of protein-protein interactions of congenital cataract crystallin mutants.

PMID:14512969

Cell death triggered by a novel mutation in the alphaA-crystallin gene underlies autosomal dominant cataract linked to chromosome 21q.

PMID:14752512

Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S) to sequester their translocation during staurosporine-induced apoptosis.

PMID:16303126

Lenticular chaperones suppress the aggregation of the cataract-causing mutant T5P gamma C-crystallin.

PMID:18407550

A novel mutation in AlphaA-crystallin (CRYAA) caused autosomal dominant congenital cataract in a large Chinese family.

PMID:19464326

HSPB7 is a SC35 speckle resident small heat shock protein.

PMID:19503744

An alphaA-crystallin gene mutation, Arg12Cys, causing inherited cataract-microcornea exhibits an altered heat-shock response.

PMID:19651604

The eye lens chaperone alpha-crystallin forms defined globular assemblies.

PMID:22085609

Temperature-dependent structural and functional properties of a mutant (F71L) αA-crystallin: molecular basis for early onset of age-related cataract.

PMID:22153508

The polydispersity of αB-crystallin is rationalized by an interconverting polyhedral architecture.

PMID:23188086

Binding determinants of the small heat shock protein, αB-crystallin: recognition of the 'IxI' motif.

PMID:25416956

A proteome-scale map of the human interactome network.

PMID:25910212

Widespread macromolecular interaction perturbations in human genetic disorders.

PMID:26004348

Mutation analysis of two families with inherited congenital cataracts.

PMID:29259299

Two novel mutations identified in ADCC families impair crystallin protein distribution and induce apoptosis in human lens epithelial cells.

PMID:29892012

An interactome perturbation framework prioritizes damaging missense mutations for developmental disorders.

PMID:30340470

A novel mutation in the CRYAA gene associated with congenital cataract and microphthalmia in a Chinese family.

PMID:31515488

Extensive disruption of protein interactions by genetic variants across the allele frequency spectrum in human populations.

PMID:32296183

A reference map of the human binary protein interactome.

PMID:32814053

Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains.

PMID:33961781

Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.

PMID:8943244

Cloning, expression, and chaperone-like activity of human alphaA-crystallin.

PMID:9467006

Autosomal dominant congenital cataract associated with a missense mutation in the human alpha crystallin gene CRYAA.

file:human/CRYAA/CRYAA-deep-research-falcon.md

Falcon deep research for human CRYAA

Falcon synthesis supports CRYAA/HSPB4 as an alpha-crystallin small heat shock protein with ATP-independent holdase chaperone activity central to lens proteostasis and cataract biology.

PMID:1438232

Alpha-crystallin can function as a molecular chaperone.

Horwitz reported that unfractionated alpha-crystallin (alphaA + alphaB) both suppressed aggregation of and refolded GdnHCl-denatured gamma-crystallin by circular dichroism. This is the principal primary observation behind a positive refolding assignment, but it used a mixed alphaA/alphaB preparation and a secondary-structure readout, so it does not establish autonomous alphaA foldase activity.

"alpha-Crystallin was also effective in preventing aggregation and in refolding guanidine hydrochloride-denatured gamma-crystallin, as judged by circular dichroism spectroscopy."

PMID:8093612

Small heat shock proteins are molecular chaperones.

Jakob et al. established the family-level, ATP-independent sHSP refolding result often cited as context for sHSP refolding. The proteins named in the abstract are murine Hsp25, human Hsp27 and bovine alphaB-crystallin; alphaA-crystallin (CRYAA) is not among them, so this paper does not provide alphaA-specific refolding evidence. Note this is a 4-page JBC communication and only the abstract is cached, so this is an inference from the abstract's enumeration rather than from the full text.

"we studied the influence of murine Hsp25, human Hsp27, and bovine alpha-B-crystallin (an eye lens protein homologous to sHsps) on the unfolding and refolding of citrate synthase and alpha-glucosidase in vitro"
The refolding promoted by these sHSPs was ATP-independent, which is why a refolding term could be assigned without invoking a nucleotide-binding domain.

"they promote the functional refolding of these proteins after urea denaturation similar to GroE and Hsp90. The interaction both with unfolding and refolding proteins seems to be ATP-independent."

PMID:34055885

The Small Ones Matter-sHsps in the Bacterial Chaperone Network.

sHSP-client assemblies are resolved by downstream ATP-dependent Hsp70 and Hsp100 chaperones, which execute the productive refolding step; the sHSP contribution is holding clients aggregation-free.

"Formation of these assemblies facilitates subsequent Hsp70 and Hsp100 chaperone-dependent disaggregation and substrate refolding into native species"

PMID:35281256

Insights on Human Small Heat Shock Proteins and Their Alterations in Diseases.

Human HSPBs (the family containing CRYAA/HSPB4) act as ATP-independent holdases and cooperate in refolding that is driven by other chaperones, rather than performing the refolding themselves.

"HSPBs take part in cell homeostasis by acting as holdases, which is the ability to interact with a substrate preventing its aggregation. In addition, HSPBs cooperate in substrates refolding driven by other chaperones"
HSPBs interact indirectly with ATP-dependent foldases such as HSP70 for the refolding process, placing the foldase step outside the sHSP itself.

"HSPBs act as ATP-independent holdases, avoiding misfolded substrates aggregation"

file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md

OpenScientist hypothesis report for CRYAA protein refolding (GO:0042026)

The run independently concluded that CRYAA is an ATP-independent holdase that cannot be an autonomous foldase, because P02489 is a single alpha-crystallin domain protein with no nucleotide-binding or ATPase module. This agrees with the existing review.

"no nucleotide-binding site and no ATPase domain"
The run placed the productive refolding step on downstream ATP-dependent chaperones rather than on CRYAA itself.

"the productive refolding step is executed by downstream ATP-dependent chaperones"
The run acknowledged that the historical CD-based refolding readouts may reflect spontaneous recovery once aggregation is suppressed, which is the basis for discounting PMID:1438232 as evidence of foldase activity.

"the older assays is often an outcome measured in systems where spontaneous or residual refolding can occur once aggregation is suppressed"

Suggested Experiments

Experiment: Chemically or thermally denature a model client with a quantitative activity readout (firefly luciferase, citrate synthase, or GAPDH). Measure recovery of native enzymatic activity, not just secondary structure, under four conditions: client alone; client + purified human alphaA-crystallin; client + Hsp70/Hsp40/ATP; and client + alphaA + Hsp70/Hsp40/ATP. If alphaA alone gives little activity recovery while alphaA + Hsp70 gives substantially more than Hsp70 alone, CRYAA is a holdase that feeds a downstream foldase, supporting REMOVE of the direct GO:0042026 annotation and the GO:0140309 assignment. Use an activity readout specifically because the historical circular-dichroism readout (PMID:1438232) cannot distinguish catalyzed refolding from spontaneous recovery once aggregation is suppressed.

Hypothesis: CRYAA is a holdase, not a foldase: purified human alphaA-crystallin alone will not restore the enzymatic activity of a denatured client, but will do so when an ATP-dependent Hsp70/Hsp40 system is added.

Type: reconstituted in vitro chaperone refolding assay

Experiment: Repeat the Jakob et al. (PMID:8093612) urea-denaturation refolding assay on citrate synthase and alpha-glucosidase side by side with purified human alphaA-crystallin (CRYAA/HSPB4), human alphaB-crystallin (CRYAB/HSPB5) and Hsp27 (HSPB1) under identical stoichiometry. The original study assayed Hsp25, Hsp27 and bovine alphaB but not alphaA. A quantitative difference between alphaA and the other family members would directly justify treating the PANTHER:PTN000897708 IBA transfer as functional divergence within the family.

Hypothesis: The refolding activity reported for the sHSP family does not extend to alphaA-crystallin, i.e. the GO:0042026 IBA is a paralog-derived over-propagation.

Type: comparative paralog refolding assay

Experiment: Assay purified human alphaA-crystallin for intrinsic ATPase activity and test whether adding ATP alters its client-handling behaviour in a light-scattering aggregation-suppression assay. A negative result in both would confirm the architectural argument (single alpha-crystallin domain, no nucleotide-binding site) and rule out GO:0140662 (ATP-dependent protein folding chaperone).

Hypothesis: CRYAA has no ATP-dependent foldase machinery, consistent with the absence of a nucleotide-binding domain in P02489.

Type: ATPase and nucleotide-dependence assay

Deep Research

Falcon

(CRYAA-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 15 citations 2026-02-09T10:09:00.455385

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Comprehensive research report: CRYAA (alphaA-crystallin/HSPB4; UniProt P02489) in human

Identity, key concepts, and definitions
Gene/protein identity and family: CRYAA encodes alphaA-crystallin (HSPB4), a small heat shock protein (sHSP) subunit of the alpha-crystallins. sHSPs share a conserved α‑crystallin domain flanked by variable N- and C-termini and assemble into oligomers with holdase chaperone activity. HSPB4 can hetero-oligomerize with HSPB5 (αB‑crystallin). These features, including domain organization and sHSP family membership, are documented in recent reviews and primary studies focused on HSPB4 regulation and function (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 14-15, sluzala2024novelmtorc2hspb4interaction pages 17-18).
Core molecular function: As a chaperone, HSPB4 binds partially unfolded proteins to prevent misfolding and aggregation, thereby maintaining lens proteostasis and cell survival; mutational changes in the α‑crystallin/sHSP domain impair chaperone activity (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 14-15, sluzala2024novelmtorc2hspb4interaction pages 17-18). Population and mechanistic cataract studies reaffirm the central role of CRYAA in lens transparency (URL: https://doi.org/10.3390/cimb45060327; Jun 2023) (khidiyatova2023studyofthe pages 11-13) and the proteostasis function of CRYAA in stress (URL: https://doi.org/10.1172/jci169666; Sep 2024) (yang2024reversiblecoldinducedlens pages 3-6).
Structure, oligomerization, and post-translational regulation
Oligomerization and structural features: Phosphorylation and sequence variants alter HSPB4 oligomer size, subunit exchange, and chaperone performance, consistent with sHSP regulation paradigms described for α‑crystallins (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 14-15, sluzala2024novelmtorc2hspb4interaction pages 17-18, sluzala2024novelmtorc2hspb4interaction pages 1-2).
Key post-translational modifications: Threonine 148 (T148) phosphorylation in human HSPB4 is a critical regulatory site. Functional data show phosphomimetic T148D improves chaperone activity and solubility, while T148A abrogates these effects; T148 phosphorylation is detected in lens and retina and is reduced in diabetes/diabetic retinopathy (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2). Kinome profiling and chemoproteomics identify mTORC2 as a strong candidate kinase for T148, and the study delineates a multifaceted HSPB4–mTORC2 interaction (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 17-18).
Cellular and tissue localization
Ocular expression: HSPB4 is abundant in lens fiber cells and is also expressed in retinal neurons and glia, consistent with roles in lens transparency and retinal neuroprotection (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 17-18). Zebrafish work supports conserved, fiber cell–biased expression of cryaa during early lens development and highlights functional conservation with human CRYAA (URL: https://doi.org/10.3389/fcell.2025.1552988; Mar 2025) (rossen2025zebrafishasa pages 3-4).
Interacting pathways and proteostasis mechanisms
mTORC2 signaling and HSPB4: Evidence supports direct interaction between HSPB4 and mTORC2, with mTORC2 implicated in HSPB4 T148 phosphorylation. This post-translational control links stress signaling to HSPB4 chaperone capacity and neuroprotective function in ocular tissues (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 17-18).
Ubiquitin–proteasome system (UPS) and RNF114: A 2024 mechanistic study in a hibernator model showed that aggregated/mutant CRYAA produced during cold stress–rewarming is turned over predominantly by the proteasome, not lysosomal autophagy. An E3 ligase, RNF114, binds CRYAA, promotes its polyubiquitination, and accelerates proteasomal degradation. In vivo delivery of a TAT‑RNF114 complex reduced lens opacity in rat cold‑cataract and zebrafish oxidative cataract models, nominating RNF114‑mediated CRYAA turnover as a therapeutic modality (URL: https://doi.org/10.1172/jci169666; Sep 2024) (yang2024reversiblecoldinducedlens pages 3-6).
Disease associations, recent variants, and mechanistic impact
Congenital and age-related cataract: CRYAA mutations commonly cause dominant congenital cataracts (often nuclear/zonular), with numerous pathogenic missense alleles concentrated in the N‑terminal and α‑crystallin domains (e.g., p.R12C, p.R21W/L, p.R49C, p.R54C, p.G98R, p.R116C/H). Stop‑loss/C‑terminal extension alleles and rare recessive variants are reported. These mutations generally impair chaperone function and promote aggregation (URL: https://doi.org/10.3390/cimb45060327; Jun 2023) (khidiyatova2023studyofthe pages 11-13). A 2024 perspective on cataract genetics further contextualizes CRYAA among major cataract genes (URL: https://doi.org/10.3390/genes15060785; Jun 2024) (sluzala2024novelmtorc2hspb4interaction pages 17-18).
Recent cohort data and novel CRYAA variants (2023–2024): In a Volga–Ural cohort (45 unrelated families), likely pathogenic variants were found in 10 families; two novel CRYAA missense variants, p.L85F and p.H97Q, were identified (autosomal dominant congenital cataracts). The study also summarizes ~26 known pathogenic CRYAA variants overall (URL: https://doi.org/10.3390/cimb45060327; Jun 2023) (khidiyatova2023studyofthe pages 11-13).
Lens epithelial biology: A 2024 study showed CRYAA E156K drives epithelial–mesenchymal transition (EMT) and increases migration in human lens epithelial cells, with increased nuclear β‑catenin and elevated p‑FAK/p‑Src; β‑catenin/FAK/Src inhibitors reversed these phenotypes. These data mechanistically connect mutant CRYAA to pathways relevant for posterior subcapsular cataract and posterior capsule opacification (URL: https://doi.org/10.1016/j.heliyon.2023.e23690; Jan 2024) (zhao2024thee156kmutation pages 4-7, zhao2024thee156kmutation pages 7-9).
Current applications and real-world implementations
Therapeutic modulation of CRYAA proteostasis: The 2024 JCI study provides in vivo proof-of-concept for delivering an E3 ligase (TAT‑RNF114) to enhance mutant/aggregated CRYAA clearance and reduce lens opacity in animal models, suggesting a translational route to medical anti‑cataract therapy beyond surgery (URL: https://doi.org/10.1172/jci169666; Sep 2024) (yang2024reversiblecoldinducedlens pages 3-6).
Targeting post-translational regulation: Given that T148 phosphorylation enhances CRYAA chaperone function and is decreased in diabetic retinopathy, strategies to restore T148 phosphorylation (e.g., via mTORC2 modulation) are proposed as neuroprotective approaches in retinal disease and potentially cataract contexts, though this remains preclinical (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 17-18).
Expert opinions and recent reviews
Oxidative stress and cataracts: A 2024 review emphasizes oxidative stress as a central factor in cataractogenesis and integrates genetic contributors, noting CRYAA among crystallin genes implicated in both congenital and potentially age-related cataracts (URL: https://doi.org/10.3390/antiox13111315; Oct 2024) (zhao2024thee156kmutation pages 7-9). A 2024 genetics perspective highlights CRYAA within the Cat‑Map framework of cataract genes and discusses gene‑based therapeutic prospects (URL: https://doi.org/10.3390/genes15060785; Jun 2024) (sluzala2024novelmtorc2hspb4interaction pages 17-18).
Relevant statistics and data (recent)
Familial congenital cataract cohort (Volga–Ural): Pathogenic/probable pathogenic variants detected in 10/45 unrelated families (22.2%); two novel CRYAA variants (p.L85F, p.H97Q) were among the causative alleles identified across crystallin and connexin genes (URL: https://doi.org/10.3390/cimb45060327; Jun 2023) (khidiyatova2023studyofthe pages 11-13).
Burden and clinical relevance: Cataracts remain a leading cause of blindness worldwide; genetic and redox pathway analyses outline glutathione-centered detoxification as key to lens homeostasis, contextualizing why chaperone deficits from CRYAA mutations increase cataract risk (URL: https://doi.org/10.3390/antiox13111315; Oct 2024) (zhao2024thee156kmutation pages 7-9).
Mechanistic in vivo efficacy: TAT‑RNF114 reduced cold‑induced lens opacity in rats and oxidative cataract in zebrafish, supporting therapeutic feasibility of targeting CRYAA proteostasis via the UPS (URL: https://doi.org/10.1172/jci169666; Sep 2024) (yang2024reversiblecoldinducedlens pages 3-6).
Verification of identity and avoidance of symbol ambiguity
The literature consistently refers to alphaA‑crystallin as HSPB4 (also called αA‑crystallin), encoded by CRYAA in human ocular tissues, with α‑crystallin domain architecture characteristic of the sHSP family—matching the UniProt P02489 description and domains (URL: https://doi.org/10.3390/cells13232000; Dec 2024) (sluzala2024novelmtorc2hspb4interaction pages 1-2, sluzala2024novelmtorc2hspb4interaction pages 14-15, sluzala2024novelmtorc2hspb4interaction pages 17-18). No conflicting gene symbol usage was encountered in the cited 2023–2024 sources.

Conclusions and outlook
CRYAA (HSPB4) is a canonical sHSP chaperone critical for lens proteostasis, with functions governed by oligomeric state and post‑translational regulation. Recent advances highlight: (i) phosphorylation at T148—likely mediated by mTORC2—as a key enhancer of chaperone activity; and (ii) the ubiquitin–proteasome pathway, via RNF114, as a determinant of CRYAA turnover with translational potential for anti‑cataract therapy. New human variants (e.g., p.L85F, p.H97Q; 2023) and mechanistic cell studies (E156K‑driven EMT/migration; 2024) deepen links between CRYAA dysfunction and cataract pathology, including lens epithelial remodeling. Together, these findings refine molecular targets—post‑translational control and targeted proteostasis—for future interventions in inherited and possibly acquired cataracts (sluzala2024novelmtorc2hspb4interaction pages 1-2, yang2024reversiblecoldinducedlens pages 3-6, zhao2024thee156kmutation pages 4-7, zhao2024thee156kmutation pages 7-9, khidiyatova2023studyofthe pages 11-13, sluzala2024novelmtorc2hspb4interaction pages 17-18).

References

(sluzala2024novelmtorc2hspb4interaction pages 1-2): Zachary B. Sluzala, Yang Shan, Lynda Elghazi, Emilio L. Cárdenas, Angelina Hamati, Amanda L. Garner, and Patrice E. Fort. Novel mtorc2/hspb4 interaction: role and regulation of hspb4 t148 phosphorylation. Cells, 13:2000, Dec 2024. URL: https://doi.org/10.3390/cells13232000, doi:10.3390/cells13232000. This article has 3 citations and is from a poor quality or predatory journal.
(sluzala2024novelmtorc2hspb4interaction pages 14-15): Zachary B. Sluzala, Yang Shan, Lynda Elghazi, Emilio L. Cárdenas, Angelina Hamati, Amanda L. Garner, and Patrice E. Fort. Novel mtorc2/hspb4 interaction: role and regulation of hspb4 t148 phosphorylation. Cells, 13:2000, Dec 2024. URL: https://doi.org/10.3390/cells13232000, doi:10.3390/cells13232000. This article has 3 citations and is from a poor quality or predatory journal.
(sluzala2024novelmtorc2hspb4interaction pages 17-18): Zachary B. Sluzala, Yang Shan, Lynda Elghazi, Emilio L. Cárdenas, Angelina Hamati, Amanda L. Garner, and Patrice E. Fort. Novel mtorc2/hspb4 interaction: role and regulation of hspb4 t148 phosphorylation. Cells, 13:2000, Dec 2024. URL: https://doi.org/10.3390/cells13232000, doi:10.3390/cells13232000. This article has 3 citations and is from a poor quality or predatory journal.
(khidiyatova2023studyofthe pages 11-13): Irina Khidiyatova, Indira Khidiyatova, Rena Zinchenko, Andrey Marakhonov, Alexandra Karunas, Svetlana Avkhadeeva, Marat Aznzbaev, and Elza Khusnutdinova. Study of the molecular nature of congenital cataracts in patients from the volga–ural region. Current Issues in Molecular Biology, 45:5145-5163, Jun 2023. URL: https://doi.org/10.3390/cimb45060327, doi:10.3390/cimb45060327. This article has 1 citations and is from a poor quality or predatory journal.
(yang2024reversiblecoldinducedlens pages 3-6): Hao Yang, Xiyuan Ping, Jiayue Zhou, Hailaiti Ailifeire, Jing Wu, Francisco M. Nadal-Nicolás, Kiyoharu J. Miyagishima, Jing Bao, Yuxin Huang, Yilei Cui, Xin Xing, Shiqiang Wang, Ke Yao, Wei Li, and Xingchao Shentu. Reversible cold-induced lens opacity in a hibernator reveals a molecular target for treating cataracts. The Journal of Clinical Investigation, Sep 2024. URL: https://doi.org/10.1172/jci169666, doi:10.1172/jci169666. This article has 12 citations.
(rossen2025zebrafishasa pages 3-4): Jennifer L. Rossen, Antionette L. Williams, and Brenda L. Bohnsack. Zebrafish as a model for crystallin-associated congenital cataracts in humans. Frontiers in Cell and Developmental Biology, Mar 2025. URL: https://doi.org/10.3389/fcell.2025.1552988, doi:10.3389/fcell.2025.1552988. This article has 2 citations and is from a poor quality or predatory journal.
(zhao2024thee156kmutation pages 4-7): Zhennan Zhao, Jiahui Chen, Yongxiang Jiang, and Yi Lu. The e156k mutation in the cryaa gene affects the epithelial–mesenchymal transition and migration of human lens epithelial cells. Heliyon, 10:e23690, Jan 2024. URL: https://doi.org/10.1016/j.heliyon.2023.e23690, doi:10.1016/j.heliyon.2023.e23690. This article has 0 citations and is from a peer-reviewed journal.
(zhao2024thee156kmutation pages 7-9): Zhennan Zhao, Jiahui Chen, Yongxiang Jiang, and Yi Lu. The e156k mutation in the cryaa gene affects the epithelial–mesenchymal transition and migration of human lens epithelial cells. Heliyon, 10:e23690, Jan 2024. URL: https://doi.org/10.1016/j.heliyon.2023.e23690, doi:10.1016/j.heliyon.2023.e23690. This article has 0 citations and is from a peer-reviewed journal.

Citations

khidiyatova2023studyofthe pages 11-13
yang2024reversiblecoldinducedlens pages 3-6
rossen2025zebrafishasa pages 3-4
https://doi.org/10.3390/cells13232000;
https://doi.org/10.3390/cimb45060327;
https://doi.org/10.1172/jci169666;
https://doi.org/10.3389/fcell.2025.1552988;
https://doi.org/10.3390/genes15060785;
https://doi.org/10.1016/j.heliyon.2023.e23690;
https://doi.org/10.3390/antiox13111315;
https://doi.org/10.3390/cells13232000,
https://doi.org/10.3390/cimb45060327,
https://doi.org/10.1172/jci169666,
https://doi.org/10.3389/fcell.2025.1552988,
https://doi.org/10.1016/j.heliyon.2023.e23690,

OpenScientist

(CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md)

CRYAA and Protein Refolding (GO:0042026): Function-Assignment Hypothesis Review OpenScientist openscientist-autonomous 8 citations 2 artifacts 2026-07-06T17:54:40.030715 citations file

OpenScientist final report (text/html)

OpenScientist final report (application/pdf)

CRYAA and Protein Refolding (GO:0042026): Function-Assignment Hypothesis Review

Gene: CRYAA (αA-crystallin) — Homo sapiens (NCBITaxon:9606)
UniProt: P02489
Focus: function_assignment — existing_annotations[5].function_hypothesis
Seed hypothesis: CRYAA has protein refolding (GO:0042026)
Term/evidence context: GO:0042026 protein refolding, evidence IBA, GO_REF:0000033

Summary

Verdict: Partially supported / weakly supported — retain the IBA annotation, but treat it as a non-core, cooperation-dependent process and add the missing molecular-function term that actually captures CRYAA's primary activity.

CRYAA (αA-crystallin) is an ATP-independent small heat-shock protein (sHSP) whose directly demonstrated activity is binding partially unfolded client proteins to prevent their irreversible aggregation — the classic sHSP "holdase" function. The seed hypothesis, that CRYAA has protein refolding (GO:0042026), is defensible at the level of the GO term definition and is supported by early in vitro assays, including αA-specific work. However, the modern mechanistic consensus is that sHSPs do not autonomously refold their clients; instead, they hold clients in a folding-competent, aggregation-resistant state and hand them off to downstream ATP-dependent chaperone systems (Hsp70/Hsp100) that execute productive refolding. CRYAA has no nucleotide-binding or ATPase domain — it is a single α-crystallin domain protein — so it cannot be an autonomous foldase.

The practical consequence for curation is nuanced. The IBA annotation to GO:0042026 should be RETAINED because (a) the GO definition of "protein refolding" does not require ATP, (b) family-level and αA-specific in vitro data report apparent refolding assistance, and (c) the IBA is propagated from a defensible phylogenetic inference across the sHSP family. But the term describes a downstream, cooperation-dependent biological process, not CRYAA's direct molecular activity. The higher-value curation action is to ADD the currently missing molecular-function term GO:0051082 (unfolded protein binding), which best captures CRYAA's directly assayed holdase activity and is conspicuously absent from the P02489 annotation set. Curators should NOT add ATP-dependent foldase terms (GO:0140662) because CRYAA lacks the required nucleotide-binding machinery.

The most important caveat is the holdase-versus-foldase distinction: the literature frequently uses "refolding" loosely to describe the outcome of an sHSP + downstream-chaperone pathway, and IBA propagation can carry this outcome-level term onto individual family members even though the molecular event they perform is client binding, not catalysis of folding.

Key Findings

Finding 1 — CRYAA is an ATP-independent sHSP holdase; direct refolding (foldase) activity is not established

CRYAA is a 173-amino-acid protein built around a single central α-crystallin domain (ACD, ~residues 52–164) flanked by variable N- and C-terminal extensions. The UniProt record for P02489 lists zinc/metal-binding sites (residues 100, 102, 107, 154) but no nucleotide-binding site and no ATPase domain. This architecture is diagnostic: it is the canonical sHSP fold, which lacks the machinery required for the ATP-driven conformational cycling that ATP-dependent foldases (Hsp70, Hsp90, GroEL/Hsp60, Hsp100) use to actively remodel client conformations.

The functional literature is consistent with this architecture. On the supporting side, early in vitro assays did report apparent refolding assistance. Horwitz and colleagues showed that α-crystallin can both prevent aggregation of, and assist refolding of, guanidine-hydrochloride–denatured γ-crystallin, judged by circular dichroism (PMID: 1438232: "alpha-Crystallin was also effective in preventing aggregation and in refolding guanidine hydrochloride-denatured gamma-crystallin, as judged by circular dichroism spectroscopy."). At the family level, Jakob et al. reported that small Hsps (αB-crystallin, Hsp25/Hsp27) "promote the functional refolding of these proteins after urea denaturation similar to GroE and Hsp90," and that "the interaction both with unfolding and refolding proteins seems to be ATP-independent" (PMID: 8093612). This ATP-independence is precisely why the original annotators could support GO:0042026 without invoking a nucleotide-binding domain.

However, the modern mechanistic consensus reframes these observations. sHSP-bound clients are refolded by downstream ATP-dependent chaperones, not by the sHSP itself: "Formation of these assemblies facilitates subsequent Hsp70 and Hsp100 chaperone-dependent disaggregation and substrate refolding into native species" (PMID: 34055885). The human sHSP (HSPB) review makes the same point — HSPBs "take part in cell homeostasis by acting as holdases" and "cooperate in substrates refolding driven by other chaperones" (PMID: 35281256). In other words, the "refolding" attributable to CRYAA is a cooperative outcome in which CRYAA supplies the holdase step and other chaperones supply the foldase step.

Interpretation: CRYAA's directly demonstrated molecular action is client binding/sequestration (holdase). Autonomous, catalytic refolding (foldase activity) is not established for CRYAA and is inconsistent with its domain architecture. GO:0042026 is best read as a downstream, cooperation-dependent process rather than a direct molecular function.

Finding 2 — CRYAA lacks a molecular-function chaperone GO annotation; unfolded protein binding (GO:0051082) is missing

A full enumeration of the P02489 GO annotation set (51 annotation rows in QuickGO) shows that chaperone activity is represented only in the Biological Process aspect: GO:0042026 (protein refolding; IBA via GO_REF:0000033 plus ISS via GO_REF:0000024) and GO:0050821 (protein stabilization; IMP from PMID:12235146). The Molecular Function terms present are structural/interaction terms — GO:0005198 (structural molecule activity), GO:0005212 (structural constituent of eye lens), GO:0005515 (protein binding), and GO:0042802 (identical protein binding).

Critically, the MF terms that would directly capture chaperone activity are absent: GO:0051082 (unfolded protein binding), GO:0044183 (protein folding chaperone), and GO:0140662 (ATP-dependent protein folding chaperone) are all missing. The UniProt keyword "Chaperone" is assigned to P02489, but it is not mirrored by any molecular-function GO term — an annotation gap.

Direct experimental support for a chaperone MF term exists in the primary literature. The founding human αA-crystallin characterization paper reports the "Cloning, expression, and chaperone-like activity of human alphaA-crystallin" (PMID: 8943244) — a direct demonstration of aggregation-suppressing (holdase) activity of the human gene product, which is exactly the assay basis for GO:0051082.

Interpretation: The most informative and defensible curation improvement is to add GO:0051082 (unfolded protein binding) as the molecular-function anchor for CRYAA's chaperone role, ideally with experimental evidence (e.g., IDA from PMID:8943244) rather than only inferring the downstream BP term. This closes the gap between the UniProt "Chaperone" keyword and the GO molecular-function aspect.

Mechanistic Model / Interpretation

The following model separates CRYAA's direct molecular activity from the downstream cooperative process that the seed GO term describes.

   STRESS (heat, oxidation, UV, aging, PTMs)
      │
      ▼
   Client protein (β/γ-crystallin, etc.) begins to UNFOLD
      │
      ▼
 ┌─────────────────────────────────────────────────────────┐
 │  CRYAA (αA-crystallin) — ATP-INDEPENDENT sHSP HOLDASE    │
 │  • single α-crystallin domain (res 52–164)              │
 │  • dynamic polydisperse oligomers, subunit exchange     │
 │  • DIRECT ACTIVITY: binds unfolding client              │
 │      → GO:0051082 unfolded protein binding (MF) ★MISSING│
 │      → GO:0050821 protein stabilization (BP, IMP)       │
 │  • Prevents irreversible aggregation ("holdase")        │
 └─────────────────────────────────────────────────────────┘
      │  client held in folding-competent state
      │  (NO ATP hydrolysis by CRYAA — no NBD)
      ▼
 ┌─────────────────────────────────────────────────────────┐
 │  DOWNSTREAM ATP-DEPENDENT CHAPERONES (Hsp70 / Hsp100)   │
 │  • execute productive REFOLDING / disaggregation        │
 │  • GO:0140662 ATP-dependent protein folding chaperone   │
 └─────────────────────────────────────────────────────────┘
      │
      ▼
   Client refolded to NATIVE state
   → GO:0042026 protein refolding (BP)  ← the SEED TERM
     (a COOPERATIVE OUTCOME, not CRYAA's direct catalysis)

The key conceptual point for curation: GO:0042026 sits at the bottom of this pathway as an outcome, whereas CRYAA's mechanistic contribution sits near the top as the holdase/binding step. Because the process is genuinely ATP-independent at the CRYAA step and because in vitro reconstitutions (with or without added downstream chaperones) can register "refolding," the term is not wrong — it is imprecise about the molecular event CRYAA performs. The IBA is a reasonable phylogenetic propagation, but the molecular-function aspect is where the annotation is genuinely incomplete.

Aspect	Term	Status for CRYAA	Recommended action
MF	GO:0051082 unfolded protein binding	Missing; directly assayed	ADD (lead — curator verify; IDA candidate PMID:8943244)
MF	GO:0140662 ATP-dependent protein folding chaperone	Not applicable (no NBD)	Do not add
MF	GO:0044183 protein folding chaperone	Arguable; less specific	Optional; GO:0051082 preferred
BP	GO:0042026 protein refolding	Present (IBA + ISS)	Retain as non-core, cooperation-dependent
BP	GO:0050821 protein stabilization	Present (IMP, PMID:12235146)	Retain — well supported

Evidence Base

Citation (PMID)	Evidence type	Supports / Refutes / Qualifies	Claim tested	Key finding	Context	Confidence & limitations
1438232	Direct in vitro assay	Supports	α-crystallin assists refolding of a denatured client	α-crystallin prevented aggregation of and refolded GdnHCl-denatured γ-crystallin (by CD)	Bovine/recombinant α-crystallin, in vitro	Moderate; αA/αB mixture, CD readout, no downstream-chaperone controls
8093612	Direct in vitro assay	Supports (family-level)	sHSPs promote ATP-independent refolding	αB/Hsp25/Hsp27 promote functional refolding after urea denaturation, ATP-independently	Recombinant sHSPs, in vitro	Moderate; not αA-specific; underpins IBA
8943244	Direct assay (human gene product)	Supports (holdase MF)	Human αA-crystallin has chaperone-like activity	Cloning/expression demonstrated chaperone-like (aggregation-suppressing) activity of human αA	Recombinant human αA-crystallin	High for holdase; does not itself prove autonomous foldase
34055885	Review / mechanistic synthesis	Qualifies / partially refutes	sHSPs autonomously refold clients	sHSP assemblies facilitate subsequent Hsp70/Hsp100-dependent disaggregation and refolding	Bacterial sHSP network (general model)	High; reframes refolding as downstream
35281256	Review (human HSPBs)	Qualifies	HSPBs' direct role is holdase	HSPBs act as holdases and cooperate in refolding driven by other chaperones	Human HSPB family	High; review-level but directly on-target
33321054	Review (α-crystallins)	Qualifies	α-crystallin catalytic role	α-crystallins are holdase chaperones; prevent aggregation via client binding	Vertebrate eye lens	High; consistent with holdase model
12235146	Mutant phenotype (IMP)	Supports (protein stabilization)	αA stabilizes client proteins in vivo	Basis for GO:0050821 protein stabilization annotation	Cellular	Cited via QuickGO annotation record
38401625	Structural/biophysical	Qualifies	Mechanism of client handling	α-crystallins co-aggregate with saturating client; dynamic oligomer expansion	Recombinant αAc/αBc + model clients	Supports sequestration (holdase) mechanism
39947755	Review/biophysical	Qualifies	Structural basis of chaperone role	Intrinsically disordered, dynamic oligomers stop denatured proteins aggregating	α-crystallin	Supports holdase; not foldase

GO Curation Implications

Lead requiring curator verification.

Retain GO:0042026 (protein refolding, BP, IBA / GO_REF:0000033). The term is biologically defensible: the GO definition of "protein refolding" does not mandate ATP, family-level and αA-specific in vitro assays report apparent refolding assistance, and the IBA reflects a reasonable phylogenetic inference across the sHSP family. However, annotate/interpret it as a non-core, cooperation-dependent biological process — the productive refolding step is executed by downstream ATP-dependent chaperones, with CRYAA supplying the holdase contribution.
ADD GO:0051082 (unfolded protein binding, MF). This is the highest-value action. CRYAA's directly assayed activity — binding unfolding clients to suppress aggregation — is a molecular function currently unrepresented in the MF aspect of P02489, even though the UniProt "Chaperone" keyword is assigned. A candidate experimental basis is PMID: 8943244 (human αA chaperone-like activity), which could support an IDA. This avoids leaving "protein binding" (GO:0005515) as the only MF chaperone-adjacent term.
Do NOT add GO:0140662 (ATP-dependent protein folding chaperone) or other foldase MF terms. CRYAA has no nucleotide-binding domain or ATPase activity; an ATP-dependent foldase annotation would be mechanistically wrong.
Retain GO:0050821 (protein stabilization, BP, IMP, PMID:12235146) — well-supported and complementary.

Aspect summary: the evidence most strongly supports a molecular-function term (GO:0051082) that is currently missing; the biological-process term in question (GO:0042026) should be retained but flagged as downstream/cooperative rather than a direct catalytic function.

Mechanistic Scope

The immediate molecular function being tested by the seed hypothesis is whether CRYAA directly catalyzes the refolding of denatured/unfolded proteins to their native state. Based on domain architecture and mechanistic literature:

Direct gene-product activity (established): ATP-independent binding of partially unfolded/aggregation-prone client proteins → holdase/sequestration; prevention of irreversible aggregation. This is best captured by GO:0051082 (unfolded protein binding) and contributes to GO:0050821 (protein stabilization).
Downstream / cooperative process (the seed term): Productive refolding of held clients, which requires downstream ATP-dependent chaperones (Hsp70/Hsp100). GO:0042026 (protein refolding) describes this outcome-level process, to which CRYAA contributes but does not autonomously execute.
Higher-order phenotypes (out of scope for this MF question): maintenance of eye-lens transparency, prevention of cataract, antioxidant/metal-binding activity, anti-apoptotic roles. These are physiological consequences, not the molecular refolding activity per se.

The hypothesis therefore tests a process that CRYAA participates in, while the strongest, most specific evidence points to a molecular function (client binding) one mechanistic step upstream.

Conflicts and Alternatives

Holdase vs. foldase (primary conflict). Early in vitro reports of "refolding" (PMID: 1438232; PMID: 8093612) conflict with the modern consensus that sHSPs are holdases whose clients are refolded by downstream ATP-dependent chaperones (PMID: 34055885; PMID: 35281256). The resolution is that "refolding" in the older assays is often an outcome measured in systems where spontaneous or residual refolding can occur once aggregation is suppressed; it does not establish CRYAA as an active foldase.
Paralog / family generalization. Much of the direct "refolding" evidence is from αB-crystallin, Hsp25, and Hsp27 rather than αA-crystallin specifically (PMID: 8093612). The IBA/ISS annotation on CRYAA propagates a family-level property. αA-specific direct refolding data are thinner than αA-specific holdase data (PMID: 8943244; PMID: 1438232).
Organism-specific differences. Zebrafish work (PMID: 38705506) shows the αBa-crystallin paralog, not αA, dominates protection against age-related cataract, cautioning against over-reading αA's unique functional importance across vertebrates — though this concerns physiological role, not the molecular refolding question.
Assay-context artifacts. CD-based "refolding" readouts on GdnHCl- or urea-denatured clients can reflect secondary-structure recovery upon aggregation suppression rather than chaperone-catalyzed folding. Recent single-particle work shows α-crystallins can co-aggregate with saturating client (PMID: 38401625), further arguing the core activity is sequestration.

Limitations and Knowledge Gaps

αA-specific autonomous refolding. Checked: literature reports refolding mainly for αB/Hsp25/27 and mixed α-crystallin. Why it matters: the IBA is on CRYAA specifically; direct αA-only, downstream-chaperone-free refolding assays would confirm or refute autonomous foldase activity. Resolution: purified human αA-crystallin refolding assay of a denatured client with and without Hsp70 system, quantifying native yield.
MF annotation gap. Checked: QuickGO enumeration shows no GO:0051082/0044183/0140662 despite UniProt "Chaperone" keyword. Why it matters: the molecular function is unrepresented, weakening the annotation set. Resolution: curator adds GO:0051082 with IDA from a primary αA chaperone assay (candidate PMID:8943244).
Whether GO:0042026's ISS (GO_REF:0000024) adds independent support beyond the IBA. Checked: both present on P02489. Why it matters: redundant/inference-only support affects confidence. Resolution: trace the ISS source protein/alignment.
Quantitative contribution of CRYAA vs. downstream chaperones to net refolding in vivo. Why it matters: determines whether "refolding" should ever be considered core for CRYAA. Resolution: reconstituted or cell-based flux assays with CRYAA knockdown.
Provenance limitation of this review. The domain-architecture facts (single ACD, no NBD, metal-binding sites) and the QuickGO annotation enumeration were used as the computational backbone; no independent autonomous refolding-catalysis assay specific to human αA (with downstream chaperones excluded) was located in the literature searched.

Proposed Follow-up Experiments / Actions

Reconstituted refolding minus downstream chaperones. Denature a model client (e.g., luciferase, GAPDH, γ-crystallin); measure native activity/structure recovery with purified human αA-crystallin alone vs. αA + Hsp70/Hsp40/nucleotide. If αA alone gives little native recovery but αA + Hsp70 does, CRYAA is a holdase, not a foldase — supporting a non-core reading of GO:0042026 and prioritizing GO:0051082.
ATP-dependence control. Confirm no ATPase activity and no ATP-stimulated refolding by CRYAA, consistent with the absence of a nucleotide-binding domain.
Client-binding (holdase) assay for MF evidence. Surface plasmon resonance / light-scattering suppression / co-sedimentation of CRYAA with a destabilized client to directly evidence GO:0051082 (unfolded protein binding).
Domain/paralog comparison. Align P02489 against αB (CRYAB) and Hsp27 (HSPB1) ACDs; confirm shared holdase determinants and shared absence of NBD, supporting family-level IBA while flagging that direct refolding data are largely paralog-derived.

Curation Leads (require curator verification)

Candidate action changes
- Retain GO:0042026 (protein refolding, BP, IBA/GO_REF:0000033), reinterpreted as a non-core, cooperation-dependent process.
- Add GO:0051082 (unfolded protein binding, MF) — the primary missing molecular-function term.
- Do not add GO:0140662 (ATP-dependent protein folding chaperone) — mechanistically unsupported (no NBD).

Candidate references with snippets to verify
- PMID: 8943244: "Cloning, expression, and chaperone-like activity of human alphaA-crystallin" → candidate IDA basis for GO:0051082 (human gene product holdase activity).
- PMID: 1438232: "alpha-Crystallin was also effective in preventing aggregation and in refolding guanidine hydrochloride-denatured gamma-crystallin, as judged by circular dichroism spectroscopy." → supports GO:0042026 (with holdase caveat).
- PMID: 8093612: "they promote the functional refolding of these proteins after urea denaturation similar to GroE and Hsp90. The interaction both with unfolding and refolding proteins seems to be ATP-independent." → family-level basis for the IBA.
- PMID: 34055885: "Formation of these assemblies facilitates subsequent Hsp70 and Hsp100 chaperone-dependent disaggregation and substrate refolding into native species." → justifies non-core reading of GO:0042026.
- PMID: 35281256: HSPBs "cooperate in substrates refolding driven by other chaperones." → same.

Suggested questions for the curator
- Should GO:0042026 remain when the direct molecular event is holdase binding, given the ISS + IBA both derive from inference?
- Is there a primary αA-specific IDA paper suitable to anchor GO:0051082?

Artifacts

📚 Additional Documentation

Notes

(CRYAA-notes.md)

CRYAA Gene Review Notes

2026-05-30 - PROTEOSTASIS PN small-HSP positive-control pass

Full review is present and marked complete. The local review supports CRYAA/HSPB4 as a small heat-shock-protein holdase and lens structural protein. It explicitly treats the chaperone activity as ATP-independent aggregation suppression rather than active refolding: the existing GO:0051082 unfolded protein binding annotation is marked MODIFY to GO:0140309 unfolded protein carrier activity, and GO:0042026 protein refolding is rejected. [file:human/CRYAA/CRYAA-ai-review.yaml; PMID:8943244; PMID:18407550]

PN curation conclusion: the PN placement under Cytonuclear proteostasis > Chaperone > small HSP system > small HSP is a good positive control. Propagation to a broad chaperone term such as GO:0044183 protein folding chaperone is biologically reasonable as a bridge from PN small-HSP membership, but curator-facing displays should keep the local holdase distinction visible so this is not interpreted as evidence for foldase/refolding activity.

2026-07-25 - OpenScientist function-hypothesis run on GO:0042026

Ran a blinded OpenScientist function_hypothesis job on the seed "CRYAA has protein refolding (GO:0042026)" (IBA, GO_REF:0000033). Report at file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md.

Verdict of the run: "partially supported / weakly supported" — retain the IBA as non-core, and ADD GO:0051082 as the "missing" MF term.

What was adopted. The run's mechanism is sound and agrees with the existing review, so it was wired in as corroboration for keeping action: REMOVE:

P02489 has "no nucleotide-binding site and no ATPase domain" — a single alpha-crystallin domain protein cannot be an autonomous foldase.
The productive refolding step belongs to downstream ATP-dependent Hsp70/Hsp100 [PMID:34055885 "Formation of these assemblies facilitates subsequent Hsp70 and Hsp100 chaperone-dependent disaggregation and substrate refolding into native species"; PMID:35281256 "HSPBs act as ATP-independent holdases, avoiding misfolded substrates aggregation"].
Usefully, the run identified the primary evidence behind the positive IBA, and it is paralog-derived: PMID:8093612 (Jakob 1993) assayed "murine Hsp25, human Hsp27, and bovine alpha-B-crystallin" — alphaA was not tested; PMID:1438232 (Horwitz 1992) used unfractionated alpha-crystallin (alphaA+alphaB) with a CD readout. Both are now recorded in the review as explicit counter-evidence to the REMOVE, with the reason they do not establish autonomous alphaA foldase activity.

What was rejected, and why. The run's two headline claims about the annotation set are factually wrong, checked against CRYAA-goa.tsv and OLS:

It read the GO:0042026 ISS (GO_REF:0000024) as positive supporting evidence. It is actually NOT|involved_in, transferred from bovine UniProtKB:P02470. That negated assertion is the single most decisive datum for this hypothesis and the run missed it entirely.
Its "highest-value curation action" — add the missing GO:0051082 — is a no-op. GOA already carries three GO:0051082 annotations for P02489 (IBA GO_REF:0000033; IPI PMID:8943244 with UniProtKB:P07320; IMP PMID:18407550). It is also stale advice: GO:0051082 is now a formally obsolete term ("obsolete unfolded protein binding"), and the GO obsoletion note directs replacement to GO:0044183 or GO:0140309 — which is exactly the MODIFY the review already had.

So the run did not overturn the prior review; it confirmed it, while the review's pre-existing MODIFY to GO:0140309 is now independently vindicated by the formal obsoletion. The report is recorded with correctness: LOW_QUALITY and the specific errors documented in its review_notes.

Added. Three suggested_experiments from the run's discriminating tests, the most useful being a reconstituted refolding assay read out as enzymatic activity (not CD) with and without an Hsp70/Hsp40/ATP system — that is the experiment that would settle the IBA-versus-NOT standoff in GOA.

2026-07-25 (later) - review follow-up: GO:0140309 relabel is NOT a redefinition

PR review caught a real error in my first pass. I saw that GO:0140309 had been relabelled from "unfolded protein carrier activity" to "unfolded protein holdase activity", updated the six label: fields, and argued the new label made the term a better fit for CRYAA. That inverted this repo's own adjudication.

A relabel is not a redefinition. Verified live on QuickGO (2026-07-25) that the definition is unchanged and still carrier-specific:

"A protein carrier activity that binds to a protein in an unfolded state and escorts it to an acceptor molecule or to a specific location. The unfolded protein carrier prevents aggregation of the target protein while its being delivers to its final destination."

It is still a child of GO:0140597 "protein carrier chaperone", and GO:0044183's own comment now contrasts it as the term that "keeps it unfolded to deliver it to its final destination". CRYAA is an in-situ holdase — it does not escort clients between compartments — so it does not satisfy this definition. projects/UNFOLDED_PROTEIN_BINDING.md:285 already recorded exactly this: CRYAA ... retain GO:0051082; in-situ holdase, not carrier. Sibling reviews DROME/Hsp23, DROME/Hsp27 and yeast/HSP26 all encode the same objection.

All six sites now use id: NTR / holdase chaperone activity (NTR needed; GO:0140309 does not fit -- carrier-specific), matching the yeast/HSP26 pattern, and core_functions.molecular_function is back to GO:0051082 as an interim, matching all three siblings.

One detail of the project page has drifted: it says holdase is a BROAD synonym on GO:0140309. QuickGO now reports all three synonyms (holdase, unfolded protein carrier activity, holdase-carrier chaperone) as exact, and holdase was promoted to the primary label. That weakens one of the page's supporting arguments but not its conclusion, which rests on the definition and the parentage — both unchanged.

The bigger finding: the obsoletion went through and the NTR was never created

The project page (:134) says "Until this NTR is created, GO:0051082 obsoletion should be blocked" for the 8 holdase genes. Checked today:

GO:0051082 IS obsolete — isObsolete: true, name obsolete unfolded protein binding. The block was not honoured.
No general holdase term exists. Searching GO for "holdase chaperone activity" returns only GO:0140309 and GO:0044183. The NTR was never created.
GO:0051082's obsoletion comment offers only those same two terms as replacements — neither fits an in-situ holdase.

So CRYAA, CRYAB, HSPB6, CLU, SCG5, DNAJB6, DNAJB8 and HSPH1 are now stranded on a formally obsolete term with no correct replacement. Updated projects/UNFOLDED_PROTEIN_BINDING.md to record this; it needs escalating upstream rather than resolving per-gene.

IBA provenance corrected

I had repeated the OpenScientist report's framing that PMID:8093612 / PMID:1438232 are "the primary evidence underpinning the positive IBA". They are not. The WITH/FROM column on the IBA row is six FlyBase sHSPs + the PANTHER node, resolved via mygene.info: FBgn0001224 Hsp23, FBgn0001225 Hsp26, FBgn0001226 Hsp27, FBgn0011296 l(2)efl, FBgn0031037 CG14207, FBgn0035817 CG7409.

Notably the three seeds we review locally (DROME/Hsp23, Hsp26, Hsp27) each retain GO:0042026 on IDA-level cellular refolding evidence (PMID:26705243, PMID:16572729). So the source genuinely supports the term — this is a transfer failure, not a bad source, which is a cleaner argument for REMOVE than the one I originally wrote. All six seeds are now itemized in propagation_review.source_entities. Jakob/Horwitz are reclassified as family-level literature context, and both are marked full_text_unavailable since only abstracts are cached.

Pn Notes

(CRYAA-pn-notes.md)

CRYAA PN Consistency Notes

Generated: 2026-06-18
Project: PROTEOSTASIS
Scope: priority-only PN rereview against local AIGR review and available deep-research artifacts
UniProt: P02489
AIGR review status: COMPLETE
Priority category: ontology_gap_bridge
Local AIGR project status: local_review_complete_not_phase1
Related project: UNFOLDED_PROTEIN_BINDING.md

Source Files Checked

AIGR review YAML: present - genes/human/CRYAA/CRYAA-ai-review.yaml
AIGR review HTML: present - genes/human/CRYAA/CRYAA-ai-review.html
Gene notes: present - genes/human/CRYAA/CRYAA-notes.md
GOA TSV: present - genes/human/CRYAA/CRYAA-goa.tsv
UniProt record: present - genes/human/CRYAA/CRYAA-uniprot.txt
PROTEOSTASIS priority table: projects/PROTEOSTASIS/priority_genes.tsv
PN projection report: projects/PROTEOSTASIS/reports/pn_projection/pn_projected_gene_go_summary.tsv
PN mapping audit: projects/PROTEOSTASIS/reports/pn_mapping_audit/current_mapping_scrutiny.tsv
PN mapping file: projects/PROTEOSTASIS/mappings/chaperone_systems.yaml

Deep Research Files

genes/human/CRYAA/CRYAA-deep-research-falcon.md

AIGR Review Snapshot

Description: Alpha-crystallin A chain (CRYAA/HSPB4) is a member of the small heat shock protein (sHSP) family that serves dual roles as a major structural component of the ocular lens and as a molecular chaperone with holdase activity. CRYAA forms large oligomeric complexes (approximately 540 kDa) that suppress nonspecific aggregation of destabilized proteins under stress conditions including heat, UV irradiation, and chemical modification (PMID:8943244). Critically, CRYAA acts as a holdase rather than a foldase -- it prevents aggregation of partially unfolded proteins but does NOT actively refold them (as documented by the NOT annotation to GO:0042026 protein refolding, ISS from bovine ortholog). CRYAA hetero-oligomerizes with CRYAB (HSPB5) and contributes to lens transparency and refractive index. Post-translational modifications including phosphorylation at T148 (mediated by mTORC2) regulate chaperone capacity. Mutations in CRYAA (e.g., R116H, R116C) cause autosomal dominant congenital cataracts through loss of chaperone activity and increased protein aggregation (PMID:18407550). CRYAA also has anti-apoptotic activity, binding and sequestering pro-apoptotic Bax and Bcl-X(S) proteins (PMID:14752512).
Existing/core annotation action counts: ACCEPT: 20; KEEP_AS_NON_CORE: 9; MARK_AS_OVER_ANNOTATED: 15; MODIFY: 9; REMOVE: 1

PN Consistency Summary

Consistency: Priority-only record; no phase-1 dossier section exists yet. Local review status is local_review_complete_not_phase1. PN placement: Cytonuclear proteostasis > Chaperone > small HSP system > small HSP. Main issue: Positive control where PN placement and UPB holdase logic strongly converge
PN story / NEW pressure: Current projection rows: GO:0044183 protein folding chaperone (new_to_goa).
Mapping strategy: Use as a bridge case for ontology design: the PN placement may expose missing or underspecified GO proteostasis terms rather than a simple gene-to-existing-term propagation.
Verdict: Create bridge dossier for small-HSP holdase/foldase ontology-gap analysis

Priority Review Context

Category: ontology_gap_bridge
PN annotations: Cytonuclear proteostasis > Chaperone > small HSP system > small HSP
Why interesting: Positive control where PN placement and UPB holdase logic strongly converge
Suggested next step: Create bridge dossier for small-HSP holdase/foldase ontology-gap analysis
Related project: UNFOLDED_PROTEIN_BINDING.md

PN Projection Rows

GO:0044183 protein folding chaperone - new_to_goa; scope=ok_for_propagation_to_go; mapping=chaperone_systems.yaml; PN=Cytonuclear proteostasis|Chaperone|small HSP system|small HSP

PN Dossier Context

No phase-1 dossier exists for this priority-only gene. This note preserves the current PROTEOSTASIS boundary or exception decision and should be superseded by a dossier section if the gene is promoted into a full phase-1 batch.

Note

This file is generated from the current PROTEOSTASIS priority table, PN projection outputs, and local gene-review artifacts. Edit those source records rather than this generated note when correcting the underlying curation.

📄 View Raw YAML

id: P02489
gene_symbol: CRYAA
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  Alpha-crystallin A chain (CRYAA/HSPB4) is a member of the small heat shock protein
  (sHSP) family
  that serves dual roles as a major structural component of the ocular lens and as
  a molecular
  chaperone with holdase activity. CRYAA forms large oligomeric complexes (approximately
  540 kDa)
  that suppress nonspecific aggregation of destabilized proteins under stress conditions
  including
  heat, UV irradiation, and chemical modification (PMID:8943244). Critically, CRYAA
  acts as a
  holdase rather than a foldase -- it prevents aggregation of partially unfolded proteins
  but does
  NOT actively refold them (as documented by the NOT annotation to GO:0042026 protein
  refolding,
  ISS from bovine ortholog). CRYAA hetero-oligomerizes with CRYAB (HSPB5) and contributes
  to lens
  transparency and refractive index. Post-translational modifications including phosphorylation
  at
  T148 (mediated by mTORC2) regulate chaperone capacity. Mutations in CRYAA (e.g.,
  R116H, R116C)
  cause autosomal dominant congenital cataracts through loss of chaperone activity
  and increased
  protein aggregation (PMID:18407550). CRYAA also has anti-apoptotic activity, binding
  and
  sequestering pro-apoptotic Bax and Bcl-X(S) proteins (PMID:14752512).
existing_annotations:
- term:
    id: GO:0043066
    label: negative regulation of apoptotic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for negative regulation of apoptotic process. CRYAA has well-documented
      anti-apoptotic activity. PMID:14752512 demonstrated that alphaA- and alphaB-crystallins
      bind to pro-apoptotic Bax and Bcl-X(S) proteins via GST pulldown and coimmunoprecipitation,
      preventing their translocation from cytosol to mitochondria during staurosporine-induced
      apoptosis. The R116C cataract mutant shows much weaker affinity to Bax and Bcl-X(S)
      (PMID:14752512). PMID:14512969 showed that the R49C mutant failed to protect
      lens epithelial
      cells from staurosporine-induced apoptosis. The IBA annotation is phylogenetically
      appropriate
      for sHSP family members with anti-apoptotic activity. This is a secondary/non-core
      function
      for CRYAA beyond its primary structural and chaperone roles.
    action: KEEP_AS_NON_CORE
    reason: >-
      Anti-apoptotic activity is well-supported by direct experimental evidence from
      PMID:14752512
      and PMID:14512969, and the IBA annotation is phylogenetically sound. However,
      this is a
      secondary function compared to the core structural and chaperone holdase roles
      in the lens.
    supported_by:
    - reference_id: PMID:14752512
      supporting_text: >-
        alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis through
        interactions with members of the Bcl-2 family
    - reference_id: PMID:14752512
      supporting_text: >-
        alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo
    - reference_id: PMID:14512969
      supporting_text: >-
        unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to
        the nucleus
        and failed to protect from staurosporine-induced apoptotic cell death
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for cytoplasm localization. CRYAA is abundantly expressed in
      the cytoplasm
      of lens fiber cells. Multiple IDA-level studies confirm cytoplasmic localization
      including
      PMID:19464326, PMID:14752512, PMID:29259299, PMID:19503744, PMID:26004348, and
      PMID:30340470. UniProt also lists cytoplasm as a confirmed subcellular location.
      The IBA
      annotation is consistent with direct experimental evidence and is phylogenetically
      appropriate.
    action: ACCEPT
    reason: >-
      Cytoplasmic localization is the primary location of CRYAA, confirmed by multiple
      independent
      IDA studies using fluorescence microscopy in lens epithelial cells and other
      cell types. The
      IBA annotation is well supported.
    supported_by:
    - reference_id: PMID:29259299
      supporting_text: >-
        Wild-type alphaA-crystallin was also equally distributed in the cytoplasm
    - reference_id: PMID:14752512
      supporting_text: >-
        alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol
        into
        mitochondria during staurosporine-induced apoptosis
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for nucleus localization. UniProt notes that CRYAA (HSPB4)
      translocates to the nucleus during heat shock and resides in SC35 splicing
      speckles. This is a stress-induced secondary localization rather than the
      primary constitutive location. The
      IBA annotation is phylogenetically appropriate for sHSP family members that
      show nuclear
      translocation under stress.
    action: KEEP_AS_NON_CORE
    reason: >-
      Nuclear localization is real but conditional (stress-induced). UniProt records
      CRYAA translocation to SC35 splicing speckles during heat shock. This is not
      the primary constitutive
      localization of CRYAA, which is cytoplasmic. Keeping as non-core reflects that
      this is a
      secondary, stress-dependent localization.
    supported_by:
    - reference_id: UniProtKB:P02489
      supporting_text: >-
        Nucleus. Note=Translocates to the nucleus during heat shock and resides
        in sub-nuclear structures known as SC35 speckles or nuclear splicing
        speckles.
- term:
    id: GO:0009408
    label: response to heat
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for response to heat. CRYAA is a member of the small heat shock
      protein
      (sHSP) family and its chaperone-like activity was explicitly demonstrated using
      heat-induced
      aggregation assays (PMID:8943244). The protein suppresses heat-induced aggregation
      of aldose
      reductase and other lens proteins. CRYAA also translocates to nuclear SC35 speckles
      during
      heat shock (PMID:19464326). The IBA annotation is phylogenetically appropriate
      for the sHSP
      family whose hallmark is response to heat stress.
    action: ACCEPT
    reason: >-
      Response to heat is a core function of sHSP family members. CRYAA suppresses
      heat-induced
      protein aggregation (PMID:8943244) and shows heat-shock-dependent nuclear translocation
      (PMID:19464326). The IBA annotation is well justified for the sHSP family.
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        both WT and W9F subunits completely suppressed the heat-induced aggregation
        of aldose
        reductase
    - reference_id: file:human/CRYAA/CRYAA-deep-research-falcon.md
      supporting_text: >-
        As a chaperone, HSPB4 binds partially unfolded proteins to prevent
        misfolding and aggregation, thereby maintaining lens proteostasis and
        cell survival
- term:
    id: GO:0042026
    label: protein refolding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for protein refolding. This is problematic for CRYAA. While some
      sHSP family
      members can assist in protein refolding (e.g., HSPB1/Hsp27 cooperates with Hsp70
      to refold
      substrates), CRYAA specifically acts as a holdase that prevents aggregation
      but does NOT
      refold proteins. This is documented by the NOT annotation to GO:0042026 (ISS
      from bovine
      ortholog, GO_REF:0000024). The IBA propagation from the broader sHSP family
      is overly
      broad for CRYAA, which lacks foldase activity. PMID:19464326 showed that HSPB1
      and HSPB5
      kept heat-unfolded substrates folding-competent, but HSPB7 did not support refolding,
      highlighting functional divergence within the family. CRYAA has holdase but
      not foldase
      activity.

      A focused OpenScientist function-assignment run on this hypothesis
      (file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md)
      independently reached the holdase-not-foldase conclusion on mechanistic and
      architectural grounds: the UniProt record for P02489 has "no nucleotide-binding
      site and no ATPase domain", so CRYAA cannot be an autonomous foldase, and the
      productive refolding step is executed by downstream ATP-dependent Hsp70/Hsp100
      chaperones (PMID:34055885, PMID:35281256). That run nonetheless recommended
      RETAINing the IBA as a non-core cooperative process. That recommendation is not
      adopted here, for two reasons that the run got factually wrong (see the
      reference_review on its report): it did not register that GOA already carries a
      NOT|involved_in ISS annotation on this very term, and its headline
      recommendation to "add the missing GO:0051082" is a no-op -- GOA already carries
      three GO:0051082 annotations for P02489 (IBA, IPI from PMID:8943244, IMP from
      PMID:18407550), and GO:0051082 is now formally obsolete, with the GO obsoletion
      note directing replacement to GO:0044183 or GO:0140309.

      On provenance: this IBA's actual ancestral evidence set is the WITH/FROM column
      of the GOA row, which is six Drosophila sHSP genes plus the PANTHER node --
      FB:FBgn0001224 (Hsp23), FB:FBgn0001225 (Hsp26), FB:FBgn0001226 (Hsp27),
      FB:FBgn0011296 (l(2)efl), FB:FBgn0031037 (CG14207), FB:FBgn0035817 (CG7409),
      PANTHER:PTN000897708. Those fly seeds do carry direct refolding evidence at the
      source: the local DROME/Hsp23, DROME/Hsp26 and DROME/Hsp27 reviews each retain
      GO:0042026 on IDA-level cellular refolding assays (PMID:26705243,
      PMID:16572729). So the source supports the term; the question is whether it
      transfers to human alphaA, and a Drosophila-sHSP-to-human-alphaA transfer is a
      long reach. GOA's own NOT|involved_in ISS from the bovine ortholog
      (UniProtKB:P02470) is the direct answer that it does not.

      Separately, PMID:8093612 and PMID:1438232 are family-level literature context
      for the sHSP refolding property rather than part of this IBA's evidence chain,
      and neither is alphaA-specific. PMID:8093612 (Jakob 1993) assayed "murine Hsp25,
      human Hsp27, and bovine alpha-B-crystallin" -- alphaA-crystallin is not among
      the proteins named in the abstract (only the abstract is cached). PMID:1438232 (Horwitz 1992) reported refolding of
      GdnHCl-denatured gamma-crystallin using unfractionated alpha-crystallin
      (alphaA + alphaB) with a circular-dichroism readout, which as the run notes can
      reflect secondary-structure recovery once aggregation is suppressed rather than
      chaperone-catalyzed folding.
    action: REMOVE
    reason: >-
      CRYAA is a holdase, not a foldase. It prevents aggregation of denatured proteins
      but does
      not refold them. The NOT annotation to GO:0042026 (ISS, GO_REF:0000024) explicitly
      documents this. The IBA propagation from the broader sHSP family is incorrect
      for CRYAA
      because not all sHSP members have refolding activity. There is functional divergence
      within the family (PMID:19464326). The IBA's seeds are six Drosophila sHSPs
      (see summary) which do have their own refolding evidence, so this is a
      transfer-failure rather than a bad source: the property does not reach human
      alphaA, as GOA's own NOT|involved_in ISS from bovine UniProtKB:P02470 states
      directly. The family-level literature context sometimes cited for refolding
      (PMID:1438232, PMID:8093612) is mixed-oligomer or non-alphaA and does not
      establish autonomous alphaA foldase activity; both the domain architecture
      (single alpha-crystallin domain, no nucleotide-binding domain) and the modern
      mechanistic consensus that Hsp70/Hsp100 execute the refolding step
      (PMID:34055885, PMID:35281256) argue against it.
    propagation_review:
      root_cause: PROPAGATION_BAD
      failure_modes:
      - PSEUDO_OR_SUBACTIVITY_LOSS
      - FUNCTIONAL_DIVERGENCE
      source_entities:
      - source_id: PANTHER:PTN000897708
        source_label: small heat-shock protein PANTHER source node
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: The family source can include refolding-associated sHSP biology,
          but CRYAA is reviewed as a holdase that prevents aggregation without refolding
          clients.
      - source_id: FB:FBgn0001224
        source_label: Drosophila Hsp23
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA. The local DROME/Hsp23 review
          retains GO:0042026 on IDA-level cellular refolding evidence
          (PMID:26705243, PMID:16572729), so the term is well supported at the
          source; it is the transfer to human alphaA that fails.
      - source_id: FB:FBgn0001225
        source_label: Drosophila Hsp26
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA. DROME/Hsp26 retains
          GO:0042026 on IDA cellular refolding evidence (PMID:26705243), framed as
          holding substrates in a refoldable state for the HSP70 machine.
      - source_id: FB:FBgn0001226
        source_label: Drosophila Hsp27
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA. DROME/Hsp27 keeps GO:0042026
          as non-core, describing an indirect refolding contribution via handoff to
          the Hsp70 system.
      - source_id: FB:FBgn0011296
        source_label: Drosophila l(2)efl
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA; a Drosophila sHSP not
          reviewed locally.
      - source_id: FB:FBgn0031037
        source_label: Drosophila CG14207
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA; an uncharacterized
          Drosophila sHSP not reviewed locally.
      - source_id: FB:FBgn0035817
        source_label: Drosophila CG7409
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: An actual WITH/FROM seed for this IBA; an uncharacterized
          Drosophila sHSP not reviewed locally.
      - source_id: UniProtKB:P02470
        source_label: bovine CRYAA NOT-refolding source
        source_status: SUPPORTS_TRANSFER
        comment: The independent NOT annotation from the bovine ortholog supports
          the target review by contradicting the positive IBA to protein refolding.
    additional_reference_ids:
    - file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md
    - PMID:34055885
    - PMID:35281256
    - PMID:8093612
    - PMID:1438232
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        alpha-crystallin subunits associate to form large oligomeric aggregates that
        express
        chaperone-like activity, as defined by the ability to suppress nonspecific
        aggregation
        of proteins destabilized by treatment with a variety of denaturants
    - reference_id: PMID:19464326
      supporting_text: >-
        Unlike HSPB1 and HSPB5, that chaperoned heat unfolded substrates and kept
        them folding
        competent, HSPB7 did not support refolding
    - reference_id: PMID:35281256
      supporting_text: >-
        HSPBs act as ATP-independent holdases, avoiding misfolded substrates
        aggregation
    - reference_id: PMID:34055885
      supporting_text: >-
        Formation of these assemblies facilitates subsequent Hsp70 and Hsp100
        chaperone-dependent disaggregation and substrate refolding into native species
    - reference_id: PMID:8093612
      supporting_text: >-
        we studied the influence of murine Hsp25, human Hsp27, and bovine
        alpha-B-crystallin (an eye lens protein homologous to sHsps) on the unfolding
        and refolding of citrate synthase and alpha-glucosidase in vitro
    - reference_id: file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md
      supporting_text: >-
        no nucleotide-binding site and no ATPase domain
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962).
      CRYAA/HSPB4 does
      interact with partially unfolded/destabilized proteins, but the term "unfolded
      protein binding"
      is problematic because it implies a simple binding function rather than the
      active chaperone
      holdase activity that CRYAA performs. CRYAA suppresses nonspecific aggregation
      of destabilized
      proteins (PMID:8943244) but does NOT refold them -- it is a holdase, not a foldase.
      The IBA
      annotation is phylogenetically propagated from sHSP family members across Drosophila,
      zebrafish,
      and mammals, which is appropriate for the family-level chaperone function. However,
      the term
      itself needs replacement, and as of 2026-07-25 no adequate replacement exists.
      GO:0051082 is now FORMALLY OBSOLETE ("obsolete unfolded protein binding"), and
      its obsoletion comment offers only two replacements: "protein folding chaperone
      (GO:0044183) or unfolded protein holdase activity (GO:0140309)". Neither fits
      CRYAA. GO:0044183 is for foldases that "assist the protein folding process",
      which CRYAA does not do. GO:0140309, despite having been relabelled to "unfolded
      protein holdase activity", retains an unchanged CARRIER-SPECIFIC definition --
      "A protein carrier activity that binds to a protein in an unfolded state and
      escorts it to an acceptor molecule or to a specific location" -- and remains a
      child of GO:0140597 "protein carrier chaperone". CRYAA is an in-situ holdase
      that prevents aggregation without escorting substrates between compartments, so
      it does not satisfy that definition. Per
      projects/UNFOLDED_PROTEIN_BINDING.md, GO:0140309 was created (go-ontology#30552)
      for TIM carrier-holdases, and CRYAA is listed there as "retain GO:0051082;
      in-situ holdase, not carrier". GO:0051082 is therefore retained as an INTERIM
      annotation pending a general "holdase chaperone activity" NTR, consistent with
      the sibling sHSP reviews (DROME/Hsp23, DROME/Hsp27, yeast/HSP26). As a
      biological process
      annotation, GO:0050821 "protein stabilization"
      (defined as
      "Any process involved in maintaining the structure and integrity of a protein
      and preventing it
      from degradation or aggregation") is also relevant and is already annotated
      for CRYAA via
      PMID:12235146.
    action: MODIFY
    reason: >-
      GO:0051082 is now formally obsolete. CRYAA has well-documented chaperone-like
      holdase activity:
      it suppresses aggregation of heat-denatured aldose reductase and singlet-oxygen-damaged
      gamma-crystallin (PMID:8943244). However, it does NOT refold proteins (NOT annotation
      to
      GO:0042026 protein refolding, ISS). The correct MF replacement does not yet
      exist: GO:0044183 is foldase-specific and GO:0140309 is carrier-specific
      (escorting between cellular components, per go-ontology#30552), which does not
      describe CRYAA's in-situ holdase activity. Retain GO:0051082 as an interim
      annotation until a general holdase chaperone activity NTR is created.
      GO:0050821 "protein stabilization" is appropriate as a BP term.
    propagation_review:
      root_cause: TERM_SCOPING_PROBLEM
      failure_modes:
      - GRANULARITY_MISMATCH
      source_entities:
      - source_id: PANTHER:PTN000897708
        source_label: small heat-shock protein source node
        source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
        comment: The source supports small heat-shock protein holdase biology,
          but the propagated unfolded-protein-binding term is obsolete and no
          adequate in-situ holdase activity term yet exists to replace it.
    proposed_replacement_terms:
    - id: NTR
      label: holdase chaperone activity (NTR needed; GO:0140309 does not fit --
        carrier-specific)
    additional_reference_ids:
    - PMID:8943244
    - PMID:18407550
    - go-ontology#30962
    - go-ontology#30552
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        alpha-crystallin subunits associate to form large oligomeric aggregates that
        express
        chaperone-like activity, as defined by the ability to suppress nonspecific
        aggregation of
        proteins destabilized by treatment with a variety of denaturants including
        heat, UV
        irradiation, and chemical modification
    - reference_id: PMID:8943244
      supporting_text: >-
        both WT and W9F subunits completely suppressed the heat-induced aggregation
        of aldose
        reductase
- term:
    id: GO:0002088
    label: lens development in camera-type eye
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      IBA annotation for lens development in camera-type eye. CRYAA is the most abundantly
      expressed protein in the ocular lens and is essential for normal lens development
      and
      transparency. UniProt states it is expressed in the eye lens (PubMed:12356833,
      PubMed:23255486).
      Knockout studies in zebrafish show abnormal differentiation of lens fiber cells
      when
      alpha-crystallins are absent (cited in PMID:29259299). Numerous CRYAA mutations
      cause
      congenital cataracts (PMID:9467006, PMID:14512969, PMID:18407550), demonstrating
      the essential
      role in lens development. The IBA annotation is appropriate for crystallin family
      members
      involved in lens development.
    action: ACCEPT
    reason: >-
      CRYAA is a core lens protein essential for normal lens development. Mutations
      consistently
      cause congenital cataracts (PMID:9467006, PMID:14512969, PMID:18407550). The
      IBA annotation
      appropriately captures this conserved developmental role.
    supported_by:
    - reference_id: PMID:14512969
      supporting_text: >-
        The alphaA-crystallin (CRYAA) gene (CRYAA) encodes a member of the small-heat-shock
        protein (sHSP) family of molecular chaperones and is primarily and abundantly
        expressed
        in the ocular lens
    - reference_id: PMID:9467006
      supporting_text: >-
        we found that a missense mutation, R116C, is associated with ADCC in this
        family
- term:
    id: GO:0005198
    label: structural molecule activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      IEA annotation for structural molecule activity. CRYAA is a major structural
      protein of the
      eye lens contributing to transparency and refractive index (UniProt FUNCTION
      section). While
      correct, the more specific child term GO:0005212 "structural constituent of
      eye lens" is
      also annotated and is more informative. This broader IEA term is acceptable
      as a parent term
      but less informative than the specific one.
    action: MODIFY
    reason: >-
      While structural molecule activity is correct for CRYAA as a major structural
      lens protein,
      the more specific child term GO:0005212 "structural constituent of eye lens"
      is already
      annotated and is more informative. Modifying to the specific term for consistency
      with
      the IDA annotation review of the same GO term.
    proposed_replacement_terms:
    - id: GO:0005212
      label: structural constituent of eye lens
- term:
    id: GO:0005212
    label: structural constituent of eye lens
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >-
      IEA annotation for structural constituent of eye lens. This is one of the most
      appropriate
      terms for CRYAA. As alphaA-crystallin, it is the most abundant soluble protein
      in the lens,
      contributing to transparency and refractive index (UniProt FUNCTION: "Contributes
      to the
      transparency and refractive index of the lens"). The IEA mapping is accurate
      and captures
      a core function.
    action: ACCEPT
    reason: >-
      CRYAA is the defining structural constituent of the eye lens. This is a core
      function
      annotation. UniProt documents that CRYAA contributes to transparency and refractive
      index
      of the lens, confirmed by the fact that mutations cause cataracts (PMID:9467006,
      PMID:18407550).
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >-
      IEA annotation for nucleus based on UniProt subcellular location mapping. UniProt
      lists
      nucleus as a confirmed subcellular location, noting that CRYAA translocates
      to the nucleus
      during heat shock and resides in SC35 speckles (PMID:19464326). The IEA mapping
      is correct
      and consistent with the IBA and IDA annotations for the same term. However,
      nuclear
      localization is stress-induced and secondary, not constitutive.
    action: KEEP_AS_NON_CORE
    reason: >-
      The IEA mapping from UniProt subcellular location is accurate. Nuclear localization
      is
      supported by PMID:19464326 showing heat-shock-induced translocation to SC35
      speckles.
      However, this is a stress-dependent secondary localization, not the primary
      constitutive
      location of CRYAA. Marked as KEEP_AS_NON_CORE for consistency with the IBA and
      IDA
      annotations for the same GO term.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >-
      IEA annotation for cytoplasm. Cytoplasmic localization is the primary constitutive
      location
      of CRYAA, confirmed by multiple IDA-level studies (PMID:19464326, PMID:29259299,
      PMID:19503744, PMID:14752512, etc.) and UniProt subcellular location annotation.
      The IEA
      mapping is correct.
    action: ACCEPT
    reason: >-
      Cytoplasm is the primary constitutive localization of CRYAA, well supported
      by multiple
      independent studies. The IEA is consistent with IBA and IDA annotations.
- term:
    id: GO:0007601
    label: visual perception
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >-
      IEA annotation for visual perception based on UniProt keyword mapping. CRYAA
      is essential
      for lens transparency, and mutations cause cataracts that impair vision (PMID:9467006,
      PMID:14512969). However, CRYAA does not directly participate in the visual perception
      signaling pathway (phototransduction). Rather, it maintains the structural integrity
      of
      the lens through which light passes. This term is somewhat over-annotated as
      it implies
      a role in visual signaling rather than lens maintenance.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      While CRYAA is essential for lens transparency and mutations cause cataracts
      that impair
      vision, the term "visual perception" implies involvement in the phototransduction/visual
      signaling pathway. CRYAA contributes to vision indirectly by maintaining lens
      structure,
      not by participating in the perception process itself. GO:0002088 "lens development
      in
      camera-type eye" and GO:0005212 "structural constituent of eye lens" better
      capture the
      actual role.
- term:
    id: GO:0046872
    label: metal ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >-
      IEA annotation for metal ion binding from UniProt keyword mapping. UniProt documents
      that
      CRYAA binds zinc ions, with the zinc-binding motif created from residues of
      3 different
      molecules (His-100, Glu-102 from one molecule; His-107 and His-154 from additional
      molecules) to create tetrahedral coordination geometry (PMID:22890888). Inter-subunit
      bridging via zinc ions enhances oligomer stability. This is a legitimate but
      generic
      annotation; a more specific term like "zinc ion binding" (GO:0008270) would
      be more
      informative.
    action: MODIFY
    reason: >-
      Metal ion binding is too generic. The specific metal bound is zinc, which is
      important for
      oligomer stability (PMID:22890888 via UniProt). GO:0008270 "zinc ion binding"
      would be
      more informative.
    proposed_replacement_terms:
    - id: GO:0008270
      label: zinc ion binding
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:11700327
  review:
    summary: >-
      IPI annotation for protein binding from PMID:11700327. This study used a mammalian
      two-hybrid
      system to detect interactions between alphaA-crystallin and other lens crystallins
      (alphaB-,
      betaB2-, and gammaC-crystallin) and Hsp27 in HeLa cells. The interactions between
      alpha-
      crystallins and beta/gamma-crystallins were about one-third the intensity of
      alphaA-alphaB
      interactions. While the interactions are real and functionally relevant (crystallin-crystallin
      interactions maintain lens transparency), "protein binding" is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too vague. The actual interactions detected are crystallin-crystallin
      interactions, not direct evidence for a specific molecular-function replacement.
      CRYAA holdase activity is supported by aggregation-suppression assays elsewhere;
      this two-hybrid interaction record should not be used to infer a chaperone term.
    supported_by:
    - reference_id: PMID:11700327
      supporting_text: >-
        there were interactions between alphaA- (or alphaB-) and betaB2- or gammaC-crystallins
        but with an intensity of one-third that of alphaA-alphaB interactions
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:12601044
  review:
    summary: >-
      IPI annotation for protein binding from PMID:12601044. This study used the mammalian
      two-hybrid system to show that cataract-causing R116C alphaA-crystallin mutant
      has altered
      protein-protein interactions with crystallins. The wild-type CRYAA interactions
      with betaB2-
      and gammaC-crystallin decreased in the R116C mutant, while interactions with
      alphaB-crystallin
      and Hsp27 increased. "Protein binding" is uninformative for the functional context.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too generic. The crystallin-crystallin interactions documented
      are
      functionally relevant to lens protein organization, but altered two-hybrid
      interactions in a cataract mutant are not direct evidence for a chaperone
      molecular-function replacement. Keep the mechanistic context without treating
      generic protein binding as a core function.
    supported_by:
    - reference_id: PMID:12601044
      supporting_text: >-
        for the R116C alphaA-crystallin, the interactions with betaB2- and gammaC-crystallin
        decreased and those with alphaB-crystallin and heat-shock protein (Hsp)27
        increased
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:19651604
  review:
    summary: >-
      IPI annotation for protein binding from PMID:19651604. This study analyzed quaternary
      structures of alpha-crystallins and showed that alphaA-crystallin forms defined
      oligomers
      of 24 subunits as well as smaller oligomers and large clusters. The protein-protein
      interactions documented here are oligomerization (homo- and hetero-oligomerization
      with
      CRYAB), which is intrinsic to the structural and chaperone function. "Protein
      binding"
      is uninformative.
    action: MODIFY
    reason: >-
      "Protein binding" is too vague. The interactions are homo-oligomerization and
      hetero-
      oligomerization relevant to CRYAA structural and chaperone function. GO:0042802
      "identical
      protein binding" is already annotated from this reference, which is more specific.
    proposed_replacement_terms:
    - id: GO:0042802
      label: identical protein binding
    supported_by:
    - reference_id: PMID:19651604
      supporting_text: >-
        alphaA-Crystallin forms, in addition to complexes of 24 subunits, also smaller
        oligomers
        and large clusters consisting of individual oligomers
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:22085609
  review:
    summary: >-
      IPI annotation for protein binding from PMID:22085609, which studied the F71L
      mutant of
      alphaA-crystallin. This study examined structural and functional properties
      of the cataract-
      causing mutant. The interactions documented are likely crystallin oligomerization
      relevant
      to the chaperone function. "Protein binding" is uninformative.
    action: MODIFY
    reason: >-
      "Protein binding" is too generic. The interactions documented in this paper
      are crystallin
      self-interactions (oligomerization) relevant to chaperone function. GO:0042802
      "identical
      protein binding" is already annotated from this reference.
    proposed_replacement_terms:
    - id: GO:0042802
      label: identical protein binding
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:22153508
  review:
    summary: >-
      IPI annotation for protein binding from PMID:22153508, which studied the polyhedral
      architecture of alphaB-crystallin. While primarily focused on CRYAB, interactions
      with
      CRYAA may have been detected in this study. "Protein binding" is uninformative
      and should
      be replaced with more specific terms for the alpha-crystallin hetero-oligomerization.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too vague. The context is alpha-crystallin oligomerization.
      A more
      specific term describing hetero-oligomerization or structural complex formation
      would be
      more informative, but GO:0042802 should not be used here because this row is
      not specific to CRYAA self-interaction.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:23188086
  review:
    summary: >-
      IPI annotation for protein binding from PMID:23188086. This study investigated
      binding
      determinants of alphaB-crystallin, specifically recognition of the IxI motif.
      The IxI
      motif is important for sHSP oligomerization and substrate interaction. Interactions
      with
      CRYAA would be in the context of hetero-oligomerization. "Protein binding" is
      uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too vague. The context is sHSP subunit interactions via
      the IxI
      motif, relevant to hetero-oligomerization with CRYAB rather than identical
      CRYAA self-binding.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  review:
    summary: >-
      IPI annotation for protein binding from PMID:25416956 (proteome-scale interactome
      map).
      This is a high-throughput study. "Protein binding" from high-throughput interactome
      studies is uninformative and lacks the context of specific functional interactions.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from high-throughput interactome mapping is too generic. CRYAA
      is known
      to form homo- and hetero-oligomers, but this broad interactome row is not
      specific enough to justify replacing the annotation with identical protein
      binding.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25910212
  review:
    summary: >-
      IPI annotation for protein binding from PMID:25910212 (macromolecular interaction
      perturbations in human genetic disorders). This is a high-throughput study examining
      how
      disease-associated mutations perturb protein interactions. "Protein binding"
      from such
      studies is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from a high-throughput interaction perturbation study does
      not tell us
      anything specific about CRYAA function. The actual molecular functions (chaperone
      holdase,
      structural lens protein, oligomerization) are better captured by other annotations.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:29892012
  review:
    summary: >-
      IPI annotation for protein binding from PMID:29892012 (interactome perturbation
      framework
      for developmental disorders). This is a high-throughput study. "Protein binding"
      is
      uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from a high-throughput interactome perturbation study is too
      generic
      to be informative about CRYAA function.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:31515488
  review:
    summary: >-
      IPI annotation for protein binding from PMID:31515488 (disruption of protein
      interactions
      by genetic variants). This is a high-throughput study examining interaction
      perturbations.
      "Protein binding" is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from high-throughput variant effect mapping is too generic.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  review:
    summary: >-
      IPI annotation for protein binding from PMID:32296183 (reference map of human
      binary
      protein interactome). This is a high-throughput interactome mapping study. "Protein
      binding" is uninformative. GO:0042802 is already annotated from this same reference.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too vague. Although GO:0042802 "identical protein binding"
      is annotated separately from this reference, this broad interactome protein-binding
      row should not itself be converted to a self-interaction assertion.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32814053
  review:
    summary: >-
      IPI annotation for protein binding from PMID:32814053 (interactome mapping of
      neurodegenerative disease proteins). This is a high-throughput study. "Protein
      binding"
      is uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from a high-throughput neurodegenerative disease interactome
      study is
      too generic. The finding that CRYAA interacts with disease-associated proteins
      could be
      relevant to its chaperone holdase function but "protein binding" does not capture
      this.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  review:
    summary: >-
      IPI annotation for protein binding from PMID:33961781 (dual proteome-scale networks
      for
      cell-specific interactome). This is a high-throughput study. "Protein binding"
      is
      uninformative.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" from a high-throughput proteome-scale interactome study is
      too generic.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:12601044
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:12601044. This study
      demonstrated
      alphaA-crystallin self-interaction using a mammalian two-hybrid system, showing
      that the
      R116C cataract mutant had altered self-interaction. Self-interaction (homo-oligomerization)
      is a core property of CRYAA -- it forms homodimers and homotetramers as building
      blocks
      of larger homo-oligomers (UniProt). This annotation appropriately captures the
      self-interaction property.
    action: ACCEPT
    reason: >-
      CRYAA homo-oligomerization is a core structural property essential for both
      its lens
      structural role and chaperone function. The R116C cataract mutation alters this
      self-
      interaction (PMID:12601044), confirming functional importance.
    supported_by:
    - reference_id: PMID:12601044
      supporting_text: >-
        for the R116C alphaA-crystallin, the interactions with betaB2- and gammaC-crystallin
        decreased and those with alphaB-crystallin and heat-shock protein (Hsp)27
        increased
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:19651604
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:19651604. This study
      demonstrated
      that alphaA-crystallin forms defined oligomers of 24 subunits as well as smaller
      oligomers
      and large clusters using biophysical methods and electron microscopy. The self-interaction
      (homo-oligomerization) is directly demonstrated.
    action: ACCEPT
    reason: >-
      CRYAA homo-oligomerization is directly demonstrated by biophysical analysis
      showing
      24-subunit oligomers (PMID:19651604). This is a core property of the protein.
    supported_by:
    - reference_id: PMID:19651604
      supporting_text: >-
        alphaA-Crystallin forms, in addition to complexes of 24 subunits, also smaller
        oligomers
        and large clusters consisting of individual oligomers
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:22085609
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:22085609. The F71L cataract-causing
      mutant study examined structural and functional properties including oligomerization.
      Self-interaction of CRYAA is documented.
    action: ACCEPT
    reason: >-
      Self-interaction (homo-oligomerization) is a core property of CRYAA confirmed
      by multiple
      studies. The F71L mutant study provides additional evidence.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:25416956 (proteome-scale
      interactome
      map). CRYAA-CRYAA self-interaction is documented in this high-throughput study.
      UniProt
      lists 12 experiments supporting CRYAA self-interaction (IntAct). While from
      a high-
      throughput study, the self-interaction is well validated by targeted studies.
    action: ACCEPT
    reason: >-
      CRYAA homo-oligomerization is well documented. The high-throughput detection
      confirms
      targeted studies. UniProt lists 12 experiments for CRYAA-CRYAA interaction.
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:32296183 (reference map
      of human
      binary protein interactome). CRYAA self-interaction detected in this systematic
      study.
      Consistent with extensive prior evidence for homo-oligomerization.
    action: ACCEPT
    reason: >-
      CRYAA homo-oligomerization is a well-established core property, and this high-throughput
      study provides consistent confirmatory evidence.
- term:
    id: GO:0005654
    label: nucleoplasm
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  review:
    summary: >-
      IDA annotation for nucleoplasm based on curation of immunofluorescence data
      (GO_REF:0000052). PMID:19464326 showed that CRYAA (HSPB4) translocates to the
      nucleus
      during heat shock and resides in SC35 speckles, which are nuclear sub-structures
      within
      the nucleoplasm. The nucleoplasm localization is consistent with this stress-dependent
      translocation.
    action: KEEP_AS_NON_CORE
    reason: >-
      Nucleoplasm localization is supported by evidence of heat-shock-induced translocation
      to
      SC35 speckles (PMID:19464326). However, this is a stress-dependent secondary
      localization,
      not the primary constitutive location.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  review:
    summary: >-
      IDA annotation for cytosol based on curation of immunofluorescence data (GO_REF:0000052).
      CRYAA is a soluble cytoplasmic protein that exists free in the cytosol as oligomeric
      complexes. Multiple studies show uniform cytoplasmic distribution (PMID:29259299,
      PMID:19503744). Cytosol is a more specific sub-compartment of cytoplasm and
      is consistent
      with the known biology.
    action: ACCEPT
    reason: >-
      Cytosol is the primary constitutive location of CRYAA, where it exists as soluble
      oligomeric
      complexes. Consistent with multiple IDA studies showing cytoplasmic distribution.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:29259299
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:29259299. This study used fluorescence
      microscopy
      of GFP-tagged wild-type alphaA-crystallin in human lens epithelial cells and
      showed that
      wild-type CRYAA was equally distributed in the cytoplasm. The mutant (p.116_118del)
      accumulated at the nuclear peripheral membrane.
    action: ACCEPT
    reason: >-
      Direct fluorescence microscopy evidence showing wild-type CRYAA is uniformly
      distributed
      in the cytoplasm of human lens epithelial cells (PMID:29259299).
    supported_by:
    - reference_id: PMID:29259299
      supporting_text: >-
        Wild-type alphaA-crystallin was also equally distributed in the cytoplasm
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:26004348
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:26004348. This study on congenital cataract
      families
      included subcellular localization analysis. UniProt lists this as a supporting
      reference
      for cytoplasmic localization.
    action: ACCEPT
    reason: >-
      Cytoplasmic localization supported by localization data from PMID:26004348,
      consistent with
      the primary constitutive location of CRYAA.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:19503744
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:19503744. This study on the R12C alphaA-crystallin
      mutation characterized subcellular localization. UniProt lists this as supporting
      evidence
      for cytoplasmic localization.
    action: ACCEPT
    reason: >-
      Cytoplasmic localization is documented as the primary location in this study
      of the R12C
      mutant, consistent with multiple other studies.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:30340470
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:30340470. This study on a novel CRYAA
      mutation
      (congenital cataract and microphthalmia) included subcellular localization analysis.
      UniProt lists this as supporting evidence for cytoplasmic localization.
    action: ACCEPT
    reason: >-
      Cytoplasmic localization confirmed by this cataract mutation study, consistent
      with
      the known primary location of CRYAA.
- term:
    id: GO:0005198
    label: structural molecule activity
  evidence_type: IDA
  original_reference_id: PMID:16303126
  review:
    summary: >-
      IDA annotation for structural molecule activity from PMID:16303126. This study
      showed that
      alpha-crystallins (alphaA- and alphaB-) suppress aggregation of the cataract-causing
      T5P
      gammaC-crystallin mutant both in vitro and in transfected cells. The study demonstrated
      a dual role: increasing solubility and reducing aggregate size. However, "structural
      molecule
      activity" is not the best descriptor for this chaperone function. The paper
      is really about
      chaperone holdase activity, not structural function per se. The more specific
      term
      GO:0005212 "structural constituent of eye lens" better captures the structural
      role.
    action: MODIFY
    reason: >-
      The evidence in PMID:16303126 is about chaperone holdase activity (suppressing
      aggregation
      of T5P gammaC-crystallin), not structural molecule activity per se. An in-situ
      holdase activity term would better capture the molecular function demonstrated,
      but none exists: GO:0140309 is carrier-specific (escorting between cellular
      components, per go-ontology#30552) and GO:0044183 is foldase-specific. For
      the true
      structural role, GO:0005212 is already annotated.
    proposed_replacement_terms:
    - id: NTR
      label: holdase chaperone activity (NTR needed; GO:0140309 does not fit --
        carrier-specific)
    supported_by:
    - reference_id: PMID:16303126
      supporting_text: >-
        the major lenticular protein chaperones, alpha A- and alpha B-crystallin,
        increased
        the solubility of the T5P gamma C-crystallin both in vitro and in transfected
        cells
    - reference_id: PMID:16303126
      supporting_text: >-
        the size of the T5P gamma C-crystallin aggregates were also significantly
        reduced in
        the presence of the lenticular chaperones
- term:
    id: GO:0032991
    label: protein-containing complex
  evidence_type: IDA
  original_reference_id: PMID:16303126
  review:
    summary: >-
      IDA annotation for protein-containing complex from PMID:16303126. CRYAA forms
      large
      oligomeric complexes of approximately 540 kDa (PMID:8943244). UniProt documents
      that
      CRYAA forms heteropolymers (3 CRYAA : 1 CRYAB), homodimers, homotetramers, and
      larger
      homo-oligomers. It is also part of a complex with BFSP1 and BFSP2 for lens intermediate
      filament formation. The protein-containing complex annotation is correct but
      very generic.
    action: ACCEPT
    reason: >-
      CRYAA forms large homo- and hetero-oligomeric complexes as a core feature of
      its biology.
      The annotation is correct, though generic. The oligomeric complex is essential
      for both
      structural and chaperone functions.
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        aggregates of approximately 540 kDa were formed from a tryptophan-free alphaA
        mutant
        (W9F)
    - reference_id: PMID:16303126
      supporting_text: >-
        the major lenticular protein chaperones, alpha A- and alpha B-crystallin,
        increased the
        solubility of the T5P gamma C-crystallin both in vitro and in transfected
        cells
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:16303126
  review:
    summary: >-
      IPI annotation for identical protein binding from PMID:16303126. This study
      used both
      in vitro sedimentation assays and cell transfection to demonstrate that alpha-crystallins
      form complexes. CRYAA homo-oligomerization is well established and essential
      for function.
    action: ACCEPT
    reason: >-
      CRYAA homo-oligomerization is a core property demonstrated in this study and
      many others.
      The self-interaction is essential for forming the large oligomeric complexes
      required for
      both structural and chaperone functions.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:12235146
  review:
    summary: >-
      IPI annotation for protein binding from PMID:12235146. This study investigated
      the role of
      C-terminal extensions of alphaA- and alphaB-crystallins by domain swapping,
      demonstrating
      that the C-terminal extension plays a crucial role in structure and chaperone
      activity.
      The protein-protein interactions are alphaA-alphaB hetero-oligomerization. "Protein
      binding"
      is too generic.
    action: MODIFY
    reason: >-
      "Protein binding" is uninformative. The interactions documented are alpha-crystallin
      subunit interactions (hetero-oligomerization) relevant to chaperone function.
      An in-situ holdase activity term would better capture the molecular function
      demonstrated by the chaperone activity assays used, but none exists: GO:0140309
      is carrier-specific (per go-ontology#30552) and GO:0044183 is foldase-specific.
      GO:0042802 "identical protein binding" already captures the
      hetero-oligomerization aspect.
    proposed_replacement_terms:
    - id: NTR
      label: holdase chaperone activity (NTR needed; GO:0140309 does not fit --
        carrier-specific)
    supported_by:
    - reference_id: PMID:12235146
      supporting_text: >-
        Our study demonstrates that the unstructured C-terminal extensions play a
        crucial role
        in the structure and chaperone activity, in addition to generally believed
        electrostatic
        "solubilizer" function
- term:
    id: GO:0050821
    label: protein stabilization
  evidence_type: IMP
  original_reference_id: PMID:12235146
  review:
    summary: >-
      IMP annotation for protein stabilization from PMID:12235146. This study showed
      that
      domain-swapped chimeras of alphaA and alphaB crystallins have dramatically altered
      chaperone-like activity -- the chimeric alphaB with CRYAA C-terminal extension
      showed
      enhanced chaperone activity while the chimeric alphaA with CRYAB C-terminal
      extension
      almost lost activity. This demonstrates that CRYAA contributes to protein stabilization
      (preventing aggregation of destabilized proteins). GO:0050821 "protein stabilization"
      is
      defined as "any process involved in maintaining the structure and integrity
      of a protein
      and preventing it from degradation or aggregation." This is an excellent fit
      for CRYAA
      holdase activity.
    action: ACCEPT
    reason: >-
      GO:0050821 "protein stabilization" accurately describes the core holdase function
      of CRYAA
      -- preventing aggregation and maintaining protein integrity. The evidence from
      PMID:12235146
      demonstrates that the C-terminal extension of CRYAA is crucial for this function.
      This is
      one of the most appropriate BP terms for the CRYAA holdase chaperone activity.
    supported_by:
    - reference_id: PMID:12235146
      supporting_text: >-
        the chimeric alphaB with the C-terminal extension of alphaA-crystallin, alphaBAc,
        exhibits dramatically enhanced chaperone-like activity
    - reference_id: PMID:12235146
      supporting_text: >-
        the unstructured C-terminal extensions play a crucial role in the structure
        and
        chaperone activity
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IDA
  original_reference_id: PMID:19464326
  review:
    summary: >-
      IDA annotation for nucleus from PMID:19464326. The cached abstract excerpt
      available here is about HSPB7, so explicit text support is taken from the
      UniProt CRYAA subcellular-location statement, which records heat-shock-induced
      nuclear translocation to SC35 splicing speckles. While not the primary
      constitutive localization, the stress-induced nuclear translocation is
      experimentally documented in the UniProt record.
    action: KEEP_AS_NON_CORE
    reason: >-
      Nuclear localization is stress-induced (heat shock) rather than constitutive.
      CRYAA resides in SC35 speckles under stress conditions. This is a secondary
      localization.
    supported_by:
    - reference_id: UniProtKB:P02489
      supporting_text: >-
        Nucleus. Note=Translocates to the nucleus during heat shock and resides
        in sub-nuclear structures known as SC35 speckles or nuclear splicing
        speckles.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:19464326
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:19464326. This study used confocal microscopy
      to
      characterize subcellular localization of HSPB family members and showed CRYAA
      (HSPB4)
      in the cytoplasm under basal conditions.
    action: ACCEPT
    reason: >-
      Cytoplasmic localization is directly demonstrated by confocal microscopy in
      PMID:19464326,
      consistent with the primary constitutive location of CRYAA.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:14752512
  review:
    summary: >-
      IPI annotation for protein binding from PMID:14752512. This study demonstrated
      by GST
      pulldown and coimmunoprecipitation that alphaA-crystallin binds to pro-apoptotic
      Bax and
      Bcl-X(S) proteins both in vitro and in vivo, preventing their translocation
      to mitochondria
      during staurosporine-induced apoptosis. The R116C cataract mutant showed much
      weaker
      affinity. "Protein binding" is uninformative for this specific anti-apoptotic
      binding
      activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      "Protein binding" is too generic. The specific interaction is binding to pro-apoptotic
      Bax and Bcl-X(S) to sequester them and prevent apoptosis. This is better captured
      by
      the negative regulation of apoptotic process annotation (GO:0043066) already
      present.
      No single MF term perfectly captures anti-apoptotic binding, but the IPI evidence
      supports the GO:0043066 BP annotation.
    supported_by:
    - reference_id: PMID:14752512
      supporting_text: >-
        Using GST pulldown assays and coimmunoprecipitations, we demonstrated that
        alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo
    - reference_id: PMID:14752512
      supporting_text: >-
        Through the interaction, alpha-crystallins prevent the translocation of Bax
        and
        Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis
- term:
    id: GO:0042026
    label: protein refolding
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  negated: true
  review:
    summary: >-
      NOT annotation for protein refolding (ISS from bovine ortholog via GO_REF:0000024).
      This
      is a critical annotation that explicitly states CRYAA does NOT perform protein
      refolding.
      CRYAA is a holdase chaperone that prevents aggregation of denatured proteins
      but does not
      actively refold them. This is consistent with all experimental evidence: PMID:8943244
      describes the chaperone-like activity as "the ability to suppress nonspecific
      aggregation"
      with no mention of refolding capability. The negated GOA assertion is
      therefore consistent with CRYAA being a holdase without foldase activity.
      This NOT annotation should be retained because it records the biologically
      important distinction between CRYAA holdase activity and active protein
      refolding.
    action: KEEP_AS_NON_CORE
    reason: >-
      The negated annotation correctly states that CRYAA does not perform active
      protein refolding. Retaining this NOT assertion is useful because it prevents
      propagation of a foldase interpretation and because it rules out GO:0044183
      "protein folding chaperone" as the replacement for the obsolete GO:0051082.
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        alpha-crystallin subunits associate to form large oligomeric aggregates that
        express
        chaperone-like activity, as defined by the ability to suppress nonspecific
        aggregation
        of proteins destabilized by treatment with a variety of denaturants
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IPI
  original_reference_id: PMID:8943244
  review:
    summary: >-
      GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962).
      This IPI annotation
      is based on PMID:8943244, which demonstrated that recombinant human alphaA-crystallin
      (CRYAA)
      suppresses heat-induced aggregation of aldose reductase (UniProtKB:P07320, the
      WITH/FROM
      interactor) and singlet-oxygen-induced aggregation of gamma-crystallin in stoichiometric
      amounts.
      The paper explicitly defines this as "chaperone-like activity" meaning the ability
      to suppress
      nonspecific aggregation of destabilized proteins. The C-terminal truncation
      mutant (R157STOP)
      showed markedly reduced chaperone-like activity despite preserved secondary
      structure, confirming
      that the C-terminal region is essential for the holdase function. The experimental
      evidence
      clearly supports that CRYAA binds partially denatured proteins and prevents
      their aggregation,
      which is holdase (not foldase) activity. No adequate MF replacement term yet
      exists: GO:0140309 is carrier-specific (escorting between cellular components,
      per go-ontology#30552) and GO:0044183 is foldase-specific, so GO:0051082 is
      retained as an interim annotation pending a general holdase chaperone activity
      NTR.
    action: MODIFY
    reason: >-
      GO:0051082 is now formally obsolete. The experimental evidence from PMID:8943244
      clearly demonstrates
      holdase chaperone activity -- CRYAA suppresses aggregation of heat-denatured
      aldose reductase
      and singlet-oxygen-damaged gamma-crystallin. This is not "unfolded protein binding"
      in a passive
      sense; it is active suppression of aggregation. The IPI evidence (with aldose
      reductase
      UniProtKB:P07320 as interactor) is strong. Neither obsoletion-replacement
      candidate fits: GO:0044183 requires assisting folding, which CRYAA does not do,
      and GO:0140309 requires escorting the client to a destination, which CRYAA does
      not do. Retain GO:0051082 as interim until a holdase chaperone activity NTR
      exists. GO:0050821 "protein stabilization" is also relevant as a BP term.
    proposed_replacement_terms:
    - id: NTR
      label: holdase chaperone activity (NTR needed; GO:0140309 does not fit --
        carrier-specific)
    additional_reference_ids:
    - PMID:18407550
    - go-ontology#30962
    - go-ontology#30552
    supported_by:
    - reference_id: PMID:8943244
      supporting_text: >-
        alpha-crystallin subunits associate to form large oligomeric aggregates that
        express
        chaperone-like activity, as defined by the ability to suppress nonspecific
        aggregation of
        proteins destabilized by treatment with a variety of denaturants including
        heat, UV
        irradiation, and chemical modification
    - reference_id: PMID:8943244
      supporting_text: >-
        When added in stoichiometric amounts, both WT and W9F subunits completely
        suppressed the
        heat-induced aggregation of aldose reductase
    - reference_id: PMID:8943244
      supporting_text: >-
        subunits encoded by a truncation mutant in which the C-terminal 17 residues
        were deleted
        (R157STOP), despite having spectroscopic properties similar to WT, formed
        much larger
        aggregates with a marked reduction in chaperone-like activity
- term:
    id: GO:0007601
    label: visual perception
  evidence_type: IMP
  original_reference_id: PMID:9467006
  review:
    summary: >-
      IMP annotation for visual perception from PMID:9467006. This study identified
      the R116C
      missense mutation in CRYAA as causing autosomal dominant congenital cataract
      (ADCC) in
      a family. The logic is that mutation in CRYAA causes cataract, which impairs
      visual
      perception. However, CRYAA does not directly participate in phototransduction
      or visual
      signaling. It maintains lens transparency, which is a prerequisite for vision
      but not
      part of the perception pathway itself. The IMP evidence connects CRYAA to visual
      impairment
      through lens opacity, not through a direct role in visual perception.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      While CRYAA mutations cause cataracts that impair vision (PMID:9467006), CRYAA
      does not
      participate in the visual perception signaling pathway. It maintains lens structural
      integrity. GO:0002088 "lens development in camera-type eye" and GO:0005212 "structural
      constituent of eye lens" better capture the role. Marking as over-annotated
      because the
      connection to visual perception is indirect.
    supported_by:
    - reference_id: PMID:9467006
      supporting_text: >-
        we found that a missense mutation, R116C, is associated with ADCC in this
        family
- term:
    id: GO:0043066
    label: negative regulation of apoptotic process
  evidence_type: IMP
  original_reference_id: PMID:14512969
  review:
    summary: >-
      IMP annotation for negative regulation of apoptotic process from PMID:14512969.
      This study
      identified the R49C mutation in CRYAA and showed that the R49C mutant protein
      failed to
      protect lens epithelial cells from staurosporine-induced apoptotic cell death,
      whereas
      wild-type CRYAA did protect. The IMP logic is that loss-of-function mutation
      leads to
      failure to suppress apoptosis, implicating wild-type CRYAA in negative regulation
      of
      apoptosis. This is well-supported anti-apoptotic activity, consistent with the
      IBA and IDA
      annotations to the same term.
    action: KEEP_AS_NON_CORE
    reason: >-
      Anti-apoptotic function is well demonstrated by mutant phenotype: the R49C mutant
      fails
      to protect from staurosporine-induced apoptosis (PMID:14512969). This is a secondary
      function compared to the core structural and chaperone holdase roles.
    supported_by:
    - reference_id: PMID:14512969
      supporting_text: >-
        unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to
        the nucleus
        and failed to protect from staurosporine-induced apoptotic cell death
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IMP
  original_reference_id: PMID:18407550
  review:
    summary: >-
      GO:0051082 "unfolded protein binding" is being obsoleted (go-ontology#30962).
      This IMP annotation
      is based on PMID:18407550, which identified the R116H (c.346G>A) mutation in
      CRYAA as the cause
      of autosomal dominant congenital cataract in a large Chinese family. The mutant
      phenotype evidence
      is that the R116H mutant protein showed loss of chaperone activity in the DTT-induced
      insulin
      aggregation assay, increased hydrophobicity, and increased binding affinity
      to lysozyme. The
      logic is: mutation in CRYAA causes loss of chaperone (holdase) activity, leading
      to cataract,
      therefore wild-type CRYAA enables this chaperone function. This is valid IMP
      evidence for
      chaperone holdase activity. However, the term "unfolded protein binding" does
      not accurately
      capture the functional consequence measured, which is suppression of protein
      aggregation (holdase
      activity). No adequate replacement exists yet -- GO:0140309 is carrier-specific
      and GO:0044183 is foldase-specific -- so GO:0051082 is retained as interim.
    action: MODIFY
    reason: >-
      GO:0051082 is now formally obsolete. The IMP evidence from PMID:18407550 is based
      on the R116H
      cataract-causing mutation showing loss of chaperone activity in DTT-induced
      insulin aggregation
      assay. This demonstrates the functional importance of CRYAA holdase activity
      but the term
      "unfolded protein binding" mischaracterizes the function. Neither
      obsoletion-replacement candidate is correct: GO:0140309 is carrier-specific
      (escorting between cellular components, per go-ontology#30552) and GO:0044183
      requires assisting folding. Retain GO:0051082 as an interim annotation until a
      general holdase chaperone activity NTR is created.
    proposed_replacement_terms:
    - id: NTR
      label: holdase chaperone activity (NTR needed; GO:0140309 does not fit --
        carrier-specific)
    additional_reference_ids:
    - PMID:8943244
    - go-ontology#30962
    - go-ontology#30552
    supported_by:
    - reference_id: PMID:18407550
      supporting_text: >-
        loss of chaperone activity of the mutant was seen in DTT (DL-dithiothreitol)-induced
        insulin
        aggregation assay
    - reference_id: PMID:18407550
      supporting_text: >-
        Gain of activated lysozyme binding, elevation of hydrophobicity and loss of
        chaperone
        activity of the mutant protein may be some of the molecular mechanisms underlying
        cataract
        in this large family
    - reference_id: PMID:18407550
      supporting_text: >-
        Sequencing of CRYAA revealed a novel heterozygous G>A transition (c.346G>A)
        in exon 3 that
        cosegregated with the disease phenotype and results in a conservative substitution
        of Arg
        to His at codon 116 (p.R116H)
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:14752512
  review:
    summary: >-
      IDA annotation for cytoplasm from PMID:14752512. This study demonstrated that
      alphaA-
      and alphaB-crystallins reside in the cytosol and prevent the translocation of
      pro-apoptotic
      Bax and Bcl-X(S) from cytosol to mitochondria during staurosporine-induced apoptosis.
      The abstract states that "alpha-crystallins prevent the translocation of Bax
      and Bcl-X(S)
      from cytosol into mitochondria during staurosporine-induced apoptosis" (PMID:14752512),
      implying CRYAA co-localizes with these targets in the cytoplasm. This is consistent
      with
      multiple other IDA studies confirming cytoplasmic localization (PMID:29259299,
      PMID:19464326,
      PMID:19503744, PMID:26004348, PMID:30340470).
    action: ACCEPT
    reason: >-
      Cytoplasmic localization is the primary constitutive location of CRYAA. PMID:14752512
      demonstrates CRYAA in the cytosol where it interacts with and sequesters Bax
      and Bcl-X(S).
      This is consistent with all other localization studies and represents a core
      annotation.
    supported_by:
    - reference_id: PMID:14752512
      supporting_text: >-
        alpha-crystallins prevent the translocation of Bax and Bcl-X(S) from cytosol
        into
        mitochondria during staurosporine-induced apoptosis
- term:
    id: GO:0032387
    label: negative regulation of intracellular transport
  evidence_type: IDA
  original_reference_id: PMID:14752512
  review:
    summary: >-
      IDA annotation for negative regulation of intracellular transport from PMID:14752512.
      This study demonstrated using GST pulldown assays and coimmunoprecipitation
      that alphaA-
      and alphaB-crystallins bind to pro-apoptotic Bax and Bcl-X(S) both in vitro
      and in vivo,
      and "prevent the translocation of Bax and Bcl-X(S) from cytosol into mitochondria
      during
      staurosporine-induced apoptosis" (PMID:14752512). This is a specific form of
      negative
      regulation of intracellular transport -- CRYAA sequesters these proteins in
      the cytosol,
      preventing their mitochondrial translocation. The cataract-causing R116C mutant
      shows
      "much weaker affinity to Bax and Bcl-X(S)" (PMID:14752512), further supporting
      that
      wild-type CRYAA actively prevents this transport. This is a secondary, non-core
      function
      tied to the anti-apoptotic role rather than the primary structural or chaperone
      holdase
      functions.
    action: KEEP_AS_NON_CORE
    reason: >-
      The annotation is well supported by direct experimental evidence from PMID:14752512
      showing that CRYAA prevents translocation of Bax and Bcl-X(S) from cytosol to
      mitochondria. However, this is a secondary function tied to the anti-apoptotic
      role,
      not the core structural or chaperone holdase activity of CRYAA. Marked as non-core
      for consistency with the anti-apoptotic annotations (GO:0043066).
    supported_by:
    - reference_id: PMID:14752512
      supporting_text: >-
        Through the interaction, alpha-crystallins prevent the translocation of Bax
        and
        Bcl-X(S) from cytosol into mitochondria during staurosporine-induced apoptosis
    - reference_id: PMID:14752512
      supporting_text: >-
        Two prominent mutants, R116C in alphaA-crystallin and R120G, in alphaB-crystallin
        display much weaker affinity to Bax and Bcl-X(S)
- term:
    id: GO:0043066
    label: negative regulation of apoptotic process
  evidence_type: IDA
  original_reference_id: PMID:14752512
  review:
    summary: >-
      IDA annotation for negative regulation of apoptotic process from PMID:14752512.
      This
      study directly demonstrated that "Human alphaA- and alphaB-crystallins prevent
      staurosporine-induced apoptosis through interactions with members of the Bcl-2
      family"
      (PMID:14752512). Using GST pulldown and coimmunoprecipitation, the authors showed
      that
      alpha-crystallins bind to pro-apoptotic Bax and Bcl-X(S) both in vitro and in
      vivo,
      sequestering them in the cytosol and preventing their translocation to mitochondria.
      As a result, "alpha-crystallins preserve the integrity of mitochondria, restrict
      release
      of cytochrome c, repress activation of caspase-3 and block degradation of PARP"
      (PMID:14752512). The anti-apoptotic function was confirmed in human lens epithelial
      cells,
      ARPE-19 cells, and H9c2 cells under staurosporine, etoposide, or sorbitol treatment.
      The R116C cataract mutant showed much weaker affinity to Bax and Bcl-X(S), consistent
      with loss of anti-apoptotic activity contributing to cataract pathology. This
      is a well-
      documented secondary function of CRYAA beyond its primary structural and chaperone
      roles.
    action: KEEP_AS_NON_CORE
    reason: >-
      Anti-apoptotic activity of CRYAA is directly demonstrated by IDA evidence in
      PMID:14752512 using multiple experimental approaches (GST pulldown, coimmunoprecipitation,
      functional apoptosis assays in multiple cell types). However, this is a secondary
      function
      compared to the core structural lens protein and chaperone holdase roles. Marked
      as
      non-core for consistency with the IBA and IMP annotations for the same GO term.
    supported_by:
    - reference_id: PMID:14752512
      supporting_text: >-
        Human alphaA- and alphaB-crystallins prevent staurosporine-induced apoptosis
        through
        interactions with members of the Bcl-2 family
    - reference_id: PMID:14752512
      supporting_text: >-
        Using GST pulldown assays and coimmunoprecipitations, we demonstrated that
        alpha-crystallins bind to Bax and Bcl-X(S) both in vitro and in vivo
    - reference_id: PMID:14752512
      supporting_text: >-
        alpha-crystallins preserve the integrity of mitochondria, restrict release
        of
        cytochrome c, repress activation of caspase-3 and block degradation of PARP
- term:
    id: GO:0007601
    label: visual perception
  evidence_type: IMP
  original_reference_id: PMID:14512969
  review:
    summary: >-
      IMP annotation for visual perception from PMID:14512969. This study identified
      the R49C
      missense mutation in CRYAA as causing autosomal dominant "nuclear" cataract
      in a four-
      generation family. The mutant protein "was abnormally localized to the nucleus
      and failed
      to protect from staurosporine-induced apoptotic cell death" (PMID:14512969).
      The logic
      connecting CRYAA to visual perception is that the R49C mutation causes cataract
      (lens
      opacity), which impairs vision. However, CRYAA does not directly participate
      in the visual
      perception signaling pathway (phototransduction). It maintains lens structural
      integrity
      and transparency, which is a prerequisite for light transmission but not part
      of the
      perception process itself. GO:0002088 "lens development in camera-type eye"
      and GO:0005212
      "structural constituent of eye lens" more accurately capture the actual role.
      This is the
      same over-annotation issue identified for the IEA (GO_REF:0000043) and IMP (PMID:9467006)
      visual perception annotations already reviewed.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      While the R49C CRYAA mutation causes autosomal dominant cataract that impairs
      vision
      (PMID:14512969), CRYAA does not participate in the visual perception signaling
      pathway.
      It maintains lens transparency through its structural and chaperone roles. The
      connection
      to visual perception is indirect -- through lens opacity rather than involvement
      in
      phototransduction. GO:0002088 "lens development in camera-type eye" and GO:0005212
      "structural constituent of eye lens" better capture the actual function. Consistent
      with the assessment of the other visual perception annotations for CRYAA.
    supported_by:
    - reference_id: PMID:14512969
      supporting_text: >-
        unlike wild-type CRYAA, the R49C mutant protein was abnormally localized to
        the
        nucleus and failed to protect from staurosporine-induced apoptotic cell death
    - reference_id: PMID:14512969
      supporting_text: >-
        Hereditary cataract is a clinically and genetically heterogeneous lens disease
        that
        accounts for a significant proportion of visual impairment and blindness in
        childhood
core_functions:
- molecular_function:
    id: GO:0051082
    label: unfolded protein binding
  description: >-
    CRYAA (HSPB4) is a small heat shock protein that functions as an ATP-independent
    holdase chaperone. It forms large homo-oligomeric complexes (~540 kDa, ~24 subunits)
    that suppress nonspecific aggregation of proteins destabilized by heat, UV irradiation,
    and chemical modification. CRYAA does NOT actively refold substrates (documented
    by
    NOT annotation to GO:0042026 protein refolding). It maintains denatured proteins
    in a
    soluble, non-aggregated state. The C-terminal extension is essential for chaperone
    activity, and the T148 phosphorylation site (mediated by mTORC2) regulates chaperone
    capacity. Disease-causing mutations (R116C, R116H, R49C, F71L) impair chaperone
    holdase activity and cause congenital cataracts. GO:0051082 is used here as an
    INTERIM molecular function: it is formally obsolete, but neither offered
    replacement fits an in-situ holdase -- GO:0044183 "protein folding chaperone"
    requires assisting folding, and GO:0140309 (relabelled "unfolded protein holdase
    activity" but with an unchanged carrier-specific definition, child of GO:0140597
    "protein carrier chaperone") requires escorting the client to a destination.
    A general "holdase chaperone activity" NTR is needed; see
    projects/UNFOLDED_PROTEIN_BINDING.md and go-ontology#30552.
  directly_involved_in:
  - id: GO:0050821
    label: protein stabilization
  - id: GO:0009408
    label: response to heat
  locations:
  - id: GO:0005829
    label: cytosol
  supported_by:
  - reference_id: PMID:8943244
    supporting_text: >-
      alpha-crystallin subunits associate to form large oligomeric aggregates that
      express chaperone-like activity, as defined by the ability to suppress nonspecific
      aggregation of proteins destabilized by treatment with a variety of denaturants
      including heat, UV irradiation, and chemical modification.
  - reference_id: PMID:12235146
    supporting_text: >-
      the chimeric alphaB with the C-terminal extension of alphaA-crystallin exhibits
      dramatically enhanced chaperone-like activity.
    full_text_unavailable: true
  - reference_id: PMID:18407550
    supporting_text: >-
      loss of chaperone activity of the mutant was seen in DTT-induced insulin
      aggregation assay.
    full_text_unavailable: true
- molecular_function:
    id: GO:0005212
    label: structural constituent of eye lens
  description: >-
    CRYAA is the most abundantly expressed protein in the ocular lens, contributing
    to
    lens transparency and refractive index. It serves a dual role as a structural
    protein
    providing the high-concentration protein matrix required for lens transparency,
    and
    as a chaperone preventing aggregation of damaged crystallins that would cause
    light-scattering opacification. CRYAA hetero-oligomerizes with CRYAB (HSPB5) in
    a
    3:1 ratio. Mutations in CRYAA consistently cause autosomal dominant congenital
    cataracts (ADCC), confirming its essential structural role.
  directly_involved_in:
  - id: GO:0002088
    label: lens development in camera-type eye
  locations:
  - id: GO:0005829
    label: cytosol
  supported_by:
  - reference_id: PMID:14512969
    supporting_text: >-
      The alphaA-crystallin (CRYAA) gene (CRYAA) encodes a member of the small-heat-shock
      protein (sHSP) family of molecular chaperones and is primarily and abundantly
      expressed in the ocular lens
  - reference_id: PMID:9467006
    supporting_text: >-
      we found that a missense mutation, R116C, is associated with ADCC in this family.
  - reference_id: PMID:16303126
    supporting_text: >-
      the major lenticular protein chaperones, alpha A- and alpha B-crystallin,
      increased the solubility of the T5P gamma C-crystallin both in vitro and in
      transfected cells.
references:
- id: UniProtKB:P02489
  title: UniProtKB entry for human CRYAA (Alpha-crystallin A chain)
  findings:
    - statement: >-
        UniProt records CRYAA as cytoplasmic and stress-induced nuclear, with
        heat-shock-dependent residence in SC35/nuclear splicing speckles.
      supporting_text: >-
        Nucleus. Note=Translocates to the nucleus during heat shock and resides
        in sub-nuclear structures known as SC35 speckles or nuclear splicing
        speckles.
- id: GO_REF:0000024
  title: Manual transfer of experimentally-verified manual GO annotation data to
    orthologs by curator judgment of sequence similarity
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular
    Location vocabulary mapping, accompanied by conservative changes to GO terms
    applied by UniProt
  findings: []
- id: GO_REF:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning
    models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:11700327
  title: Detection of protein-protein interactions among lens crystallins in a
    mammalian two-hybrid system assay.
  findings: []
- id: PMID:12235146
  title: Role of the C-terminal extensions of alpha-crystallins. Swapping the
    C-terminal extension of alpha-crystallin to alphaB-crystallin results in
    enhanced chaperone activity.
  findings: []
- id: PMID:12601044
  title: Alteration of protein-protein interactions of congenital cataract
    crystallin mutants.
  findings: []
- id: PMID:14512969
  title: Cell death triggered by a novel mutation in the alphaA-crystallin gene
    underlies autosomal dominant cataract linked to chromosome 21q.
  findings: []
- id: PMID:14752512
  title: Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S) to
    sequester their translocation during staurosporine-induced apoptosis.
  findings: []
- id: PMID:16303126
  title: Lenticular chaperones suppress the aggregation of the cataract-causing
    mutant T5P gamma C-crystallin.
  findings: []
- id: PMID:18407550
  title: A novel mutation in AlphaA-crystallin (CRYAA) caused autosomal dominant
    congenital cataract in a large Chinese family.
  findings: []
- id: PMID:19464326
  title: HSPB7 is a SC35 speckle resident small heat shock protein.
  findings: []
- id: PMID:19503744
  title: An alphaA-crystallin gene mutation, Arg12Cys, causing inherited
    cataract-microcornea exhibits an altered heat-shock response.
  findings: []
- id: PMID:19651604
  title: The eye lens chaperone alpha-crystallin forms defined globular
    assemblies.
  findings: []
- id: PMID:22085609
  title: 'Temperature-dependent structural and functional properties of a mutant (F71L)
    αA-crystallin: molecular basis for early onset of age-related cataract.'
  findings: []
- id: PMID:22153508
  title: The polydispersity of αB-crystallin is rationalized by an
    interconverting polyhedral architecture.
  findings: []
- id: PMID:23188086
  title: 'Binding determinants of the small heat shock protein, αB-crystallin: recognition
    of the ''IxI'' motif.'
  findings: []
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
- id: PMID:25910212
  title: Widespread macromolecular interaction perturbations in human genetic
    disorders.
  findings: []
- id: PMID:26004348
  title: Mutation analysis of two families with inherited congenital cataracts.
  findings: []
- id: PMID:29259299
  title: Two novel mutations identified in ADCC families impair crystallin
    protein distribution and induce apoptosis in human lens epithelial cells.
  findings: []
- id: PMID:29892012
  title: An interactome perturbation framework prioritizes damaging missense
    mutations for developmental disorders.
  findings: []
- id: PMID:30340470
  title: A novel mutation in the CRYAA gene associated with congenital cataract
    and microphthalmia in a Chinese family.
  findings: []
- id: PMID:31515488
  title: Extensive disruption of protein interactions by genetic variants across
    the allele frequency spectrum in human populations.
  findings: []
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
- id: PMID:32814053
  title: Interactome Mapping Provides a Network of Neurodegenerative Disease
    Proteins and Uncovers Widespread Protein Aggregation in Affected Brains.
  findings: []
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the
    human interactome.
  findings: []
- id: PMID:8943244
  title: Cloning, expression, and chaperone-like activity of human
    alphaA-crystallin.
  findings: []
- id: PMID:9467006
  title: Autosomal dominant congenital cataract associated with a missense
    mutation in the human alpha crystallin gene CRYAA.
  findings: []
- id: file:human/CRYAA/CRYAA-deep-research-falcon.md
  title: Falcon deep research for human CRYAA
  findings:
    - statement: >-
        Falcon synthesis supports CRYAA/HSPB4 as an alpha-crystallin small heat
        shock protein with ATP-independent holdase chaperone activity central to
        lens proteostasis and cataract biology.
- id: PMID:1438232
  title: Alpha-crystallin can function as a molecular chaperone.
  findings:
  - statement: >-
      Horwitz reported that unfractionated alpha-crystallin (alphaA + alphaB)
      both suppressed aggregation of and refolded GdnHCl-denatured
      gamma-crystallin by circular dichroism. This is the principal primary
      observation behind a positive refolding assignment, but it used a mixed
      alphaA/alphaB preparation and a secondary-structure readout, so it does not
      establish autonomous alphaA foldase activity.
    supporting_text: >-
      alpha-Crystallin was also effective in preventing aggregation and in
      refolding guanidine hydrochloride-denatured gamma-crystallin, as judged by
      circular dichroism spectroscopy.
    full_text_unavailable: true
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified (Horwitz 1992 PNAS). Correctly cited and scientifically
      sound for its era, but it assays alpha-crystallin as a mixed oligomer, not
      alphaA specifically, and the CD readout cannot separate catalyzed refolding
      from spontaneous recovery once aggregation is suppressed. Abstract-only in
      the cache. Recorded here as the counter-evidence to the REMOVE action on
      GO:0042026; it is family/mixed-oligomer literature context, NOT part of the
      IBA evidence chain (whose seeds are six Drosophila sHSPs).
- id: PMID:8093612
  title: Small heat shock proteins are molecular chaperones.
  findings:
  - statement: >-
      Jakob et al. established the family-level, ATP-independent sHSP refolding
      result often cited as context for sHSP refolding. The proteins named in the
      abstract are murine Hsp25, human Hsp27 and bovine alphaB-crystallin;
      alphaA-crystallin (CRYAA) is not among them, so this paper does not provide
      alphaA-specific refolding evidence. Note this is a 4-page JBC communication
      and only the abstract is cached, so this is an inference from the abstract's
      enumeration rather than from the full text.
    supporting_text: >-
      we studied the influence of murine Hsp25, human Hsp27, and bovine
      alpha-B-crystallin (an eye lens protein homologous to sHsps) on the
      unfolding and refolding of citrate synthase and alpha-glucosidase in vitro
    full_text_unavailable: true
  - statement: >-
      The refolding promoted by these sHSPs was ATP-independent, which is why a
      refolding term could be assigned without invoking a nucleotide-binding
      domain.
    supporting_text: >-
      they promote the functional refolding of these proteins after urea
      denaturation similar to GroE and Hsp90. The interaction both with unfolding
      and refolding proteins seems to be ATP-independent.
    full_text_unavailable: true
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified (Jakob 1993 JBC). Correctly cited; it genuinely supports
      family-level sHSP refolding, but alphaA is not among the proteins named in
      the abstract. Abstract-only in the cache, so the "alphaA not assayed" reading
      is an inference from the abstract's enumeration, reasonable for a 4-page
      communication but not full-text-verified. Note this paper is NOT part of the
      GO:0042026 IBA evidence chain -- that IBA's WITH/FROM seeds are six
      Drosophila sHSPs -- it is family-level literature context only.
- id: PMID:34055885
  title: The Small Ones Matter-sHsps in the Bacterial Chaperone Network.
  findings:
  - statement: >-
      sHSP-client assemblies are resolved by downstream ATP-dependent Hsp70 and
      Hsp100 chaperones, which execute the productive refolding step; the sHSP
      contribution is holding clients aggregation-free.
    supporting_text: >-
      Formation of these assemblies facilitates subsequent Hsp70 and Hsp100
      chaperone-dependent disaggregation and substrate refolding into native
      species
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified; full text cached. Review-level and specifically about the
      BACTERIAL sHsp chaperone network, so it supports the general holdase/foldase
      division of labour rather than a human alphaA-specific claim. Cited as
      mechanistic context only.
- id: PMID:35281256
  title: Insights on Human Small Heat Shock Proteins and Their Alterations in
    Diseases.
  findings:
  - statement: >-
      Human HSPBs (the family containing CRYAA/HSPB4) act as ATP-independent
      holdases and cooperate in refolding that is driven by other chaperones,
      rather than performing the refolding themselves.
    supporting_text: >-
      HSPBs take part in cell homeostasis by acting as holdases, which is the
      ability to interact with a substrate preventing its aggregation. In
      addition, HSPBs cooperate in substrates refolding driven by other chaperones
  - statement: >-
      HSPBs interact indirectly with ATP-dependent foldases such as HSP70 for the
      refolding process, placing the foldase step outside the sHSP itself.
    supporting_text: >-
      HSPBs act as ATP-independent holdases, avoiding misfolded substrates
      aggregation
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PubMed-verified; full text cached. Review-level but directly on-target for
      the human HSPB family that includes CRYAA/HSPB4, and states the
      holdase-versus-foldase division explicitly. Supports the REMOVE action on
      GO:0042026 and the in-situ holdase characterization.
- id: file:human/CRYAA/CRYAA-hypotheses/function-hypothesis-go-0042026/openscientist.md
  title: OpenScientist hypothesis report for CRYAA protein refolding (GO:0042026)
  publication_type: DEEP_RESEARCH
  findings:
  - statement: >-
      The run independently concluded that CRYAA is an ATP-independent holdase
      that cannot be an autonomous foldase, because P02489 is a single
      alpha-crystallin domain protein with no nucleotide-binding or ATPase module.
      This agrees with the existing review.
    supporting_text: >-
      no nucleotide-binding site and no ATPase domain
  - statement: >-
      The run placed the productive refolding step on downstream ATP-dependent
      chaperones rather than on CRYAA itself.
    supporting_text: >-
      the productive refolding step is executed by downstream ATP-dependent
      chaperones
  - statement: >-
      The run acknowledged that the historical CD-based refolding readouts may
      reflect spontaneous recovery once aggregation is suppressed, which is the
      basis for discounting PMID:1438232 as evidence of foldase activity.
    supporting_text: >-
      the older assays is often an outcome measured in systems where spontaneous
      or residual refolding can occur once aggregation is suppressed
  reference_review:
    relevance: HIGH
    correctness: LOW_QUALITY
    review_notes: >-
      Mechanistically sound and useful -- the holdase-not-foldase reasoning, the
      no-NBD architectural argument, and the identification of PMID:8093612 and
      PMID:1438232 as paralog-derived/mixed-oligomer evidence were all checked and
      hold up. However, the report's annotation-set enumeration is wrong in two
      ways that undercut its recommendations, so its verdict was not adopted.
      (1) It reports the GO:0042026 ISS (GO_REF:0000024) as positive supporting
      evidence; in CRYAA-goa.tsv that row is NOT|involved_in from bovine
      UniProtKB:P02470, i.e. it refutes rather than supports the hypothesis. This
      is the single most decisive datum for the seed hypothesis and the run missed
      it. (2) Its headline recommendation, ADD the "missing" GO:0051082 (unfolded
      protein binding), is a no-op -- GOA already carries three GO:0051082
      annotations for P02489 (IBA GO_REF:0000033; IPI PMID:8943244 with
      UniProtKB:P07320; IMP PMID:18407550) -- and is also obsolete advice, since
      GO:0051082 is now a formally obsolete term whose GO obsoletion note directs
      replacement to GO:0044183 or GO:0140309 -- neither of which fits an in-situ
      holdase, so the run's "add GO:0051082" advice is doubly unusable. The run's
      recommendation against adding GO:0140662 (ATP-dependent protein folding
      chaperone) is correct and consistent with the review.
suggested_questions:
- question: >-
    GOA carries both a positive IBA (GO_REF:0000033) and a NOT|involved_in ISS
    (GO_REF:0000024, from bovine UniProtKB:P02470) on GO:0042026 for CRYAA. Which
    assertion should stand, given that the IBA's WITH/FROM seeds are six
    Drosophila sHSPs (Hsp23, Hsp26, Hsp27, l(2)efl, CG14207, CG7409) whose own
    refolding evidence is fly-specific, and that no alphaA-specific refolding
    assay exists?
- question: >-
    Is there any assay of purified human alphaA-crystallin restoring the
    biological activity of a denatured client in the absence of an ATP-dependent
    Hsp70/Hsp100 system? GO:0042026 is defined as restoring biological activity,
    which a holdase alone would not accomplish.
- question: >-
    GO:0051082 has been obsoleted even though projects/UNFOLDED_PROTEIN_BINDING.md
    asked for the obsoletion to be blocked pending a general holdase term, and no
    such term appears to have been created. For the three existing CRYAA
    GO:0051082 annotations, is the intended replacement GO:0140309 (unfolded
    protein holdase activity), GO:0044183 (protein folding chaperone), or should
    GO:0051082 be retained pending a general holdase-chaperone-activity NTR
    (go-ontology#30552)? This review takes the third option: GO:0140309 is
    carrier-specific (it requires escorting the client to a destination and is a
    child of GO:0140597 "protein carrier chaperone") and GO:0044183 requires
    assisting folding, so neither describes an in-situ holdase like CRYAA.
suggested_experiments:
- hypothesis: >-
    CRYAA is a holdase, not a foldase: purified human alphaA-crystallin alone will
    not restore the enzymatic activity of a denatured client, but will do so when
    an ATP-dependent Hsp70/Hsp40 system is added.
  description: >-
    Chemically or thermally denature a model client with a quantitative activity
    readout (firefly luciferase, citrate synthase, or GAPDH). Measure recovery of
    native enzymatic activity, not just secondary structure, under four
    conditions: client alone; client + purified human alphaA-crystallin; client +
    Hsp70/Hsp40/ATP; and client + alphaA + Hsp70/Hsp40/ATP. If alphaA alone gives
    little activity recovery while alphaA + Hsp70 gives substantially more than
    Hsp70 alone, CRYAA is a holdase that feeds a downstream foldase, supporting
    REMOVE of the direct GO:0042026 annotation and the GO:0140309 assignment. Use
    an activity readout specifically because the historical circular-dichroism
    readout (PMID:1438232) cannot distinguish catalyzed refolding from spontaneous
    recovery once aggregation is suppressed.
  experiment_type: reconstituted in vitro chaperone refolding assay
- hypothesis: >-
    The refolding activity reported for the sHSP family does not extend to
    alphaA-crystallin, i.e. the GO:0042026 IBA is a paralog-derived
    over-propagation.
  description: >-
    Repeat the Jakob et al. (PMID:8093612) urea-denaturation refolding assay on
    citrate synthase and alpha-glucosidase side by side with purified human
    alphaA-crystallin (CRYAA/HSPB4), human alphaB-crystallin (CRYAB/HSPB5) and
    Hsp27 (HSPB1) under identical stoichiometry. The original study assayed Hsp25,
    Hsp27 and bovine alphaB but not alphaA. A quantitative difference between
    alphaA and the other family members would directly justify treating the
    PANTHER:PTN000897708 IBA transfer as functional divergence within the family.
  experiment_type: comparative paralog refolding assay
- hypothesis: >-
    CRYAA has no ATP-dependent foldase machinery, consistent with the absence of a
    nucleotide-binding domain in P02489.
  description: >-
    Assay purified human alphaA-crystallin for intrinsic ATPase activity and test
    whether adding ATP alters its client-handling behaviour in a light-scattering
    aggregation-suppression assay. A negative result in both would confirm the
    architectural argument (single alpha-crystallin domain, no nucleotide-binding
    site) and rule out GO:0140662 (ATP-dependent protein folding chaperone).
  experiment_type: ATPase and nucleotide-dependence assay

CRYAA

Gene Description

Existing Annotations Review

Core Functions

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Citations

OpenScientist

CRYAA and Protein Refolding (GO:0042026): Function-Assignment Hypothesis Review

Summary

Key Findings

Finding 1 — CRYAA is an ATP-independent sHSP holdase; direct refolding (foldase) activity is not established

Finding 2 — CRYAA lacks a molecular-function chaperone GO annotation; unfolded protein binding (GO:0051082) is missing

Mechanistic Model / Interpretation

Evidence Base

GO Curation Implications

Mechanistic Scope

Conflicts and Alternatives

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Curation Leads (require curator verification)

Artifacts

📚 Additional Documentation

Notes

CRYAA Gene Review Notes

2026-05-30 - PROTEOSTASIS PN small-HSP positive-control pass

2026-07-25 - OpenScientist function-hypothesis run on GO:0042026

2026-07-25 (later) - review follow-up: GO:0140309 relabel is NOT a redefinition

The bigger finding: the obsoletion went through and the NTR was never created

IBA provenance corrected

Pn Notes

CRYAA PN Consistency Notes

Source Files Checked

Deep Research Files

AIGR Review Snapshot

PN Consistency Summary

Priority Review Context

PN Projection Rows

PN Dossier Context

Note

📄 View Raw YAML