id: P30040
gene_symbol: ERP29
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
alternative_products:
- name: '1'
  id: P30040-1
- name: '2'
  id: P30040-2
  sequence_note: VSP_045680, VSP_045681
description: ERP29 (endoplasmic reticulum resident protein 29; also called ERp28 and ERp31) is a soluble, ER-lumenal, homodimeric member of the protein disulfide isomerase (PDI) family that is catalytically redox-inactive - it has a thioredoxin-like fold but lacks the CXXC active-site motif and is not a disulfide isomerase. It functions as a non-catalytic escort/chaperone that assists the folding, processing and trafficking of secretory cargo in the ER, and is a component of a large ER chaperone multiprotein complex (containing BiP/HSPA5, GRP94/HSP90B1, PDI, the Hsp40 co-chaperone ERdj3/DNAJB11, cyclophilin B/PPIB, ERp72/PDIA4, UGGT1 and SDF2L1) that binds nascent, incompletely folded clients such as immunoglobulin heavy chains. It is retained in the ER lumen by a C-terminal KEEL retention signal and is broadly expressed, especially in secretory tissues; pools have also been detected at the cell surface, in melanosomes and secreted. Beyond its core chaperone role it has been implicated in handling of specific cargo (e.g. thyroglobulin, connexins) and in toxin/virus membrane penetration, and in cell-context-specific signaling (p38 MAPK, gene expression and secretion control in cancer models).
existing_annotations:
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: ERP29 is an ER-resident lumenal protein; the ER is its primary site of action.
    action: ACCEPT
    reason: ER localization is well supported (retention signal, immunofluorescence, fractionation) and is the core compartment for ERP29's chaperone function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: located_in
  review:
    summary: Electronic ER localization, consistent with the IBA/IDA evidence.
    action: ACCEPT
    reason: Correct compartment for this ER-resident chaperone.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: ERP29 is a soluble ER-lumenal protein with a KEEL retention signal; the precise compartment.
    action: ACCEPT
    reason: ER lumen is the documented, precise localization for this soluble chaperone.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0009306
    label: protein secretion
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: ERP29 participates in the processing and secretion of secretory proteins; a plausible downstream process of its chaperone role.
    action: KEEP_AS_NON_CORE
    reason: ERP29 facilitates secretory-protein processing/trafficking, so a protein-secretion process annotation is reasonable but is a downstream consequence of its chaperone function rather than a direct molecular activity.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Plays an important role in the processing of secretory proteins within the endoplasmic reticulum
- term:
    id: GO:0042470
    label: melanosome
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: ERP29 was identified by mass spectrometry in melanosome fractions; a secondary localization.
    action: KEEP_AS_NON_CORE
    reason: A proteomics-detected secondary localization, peripheral to the core ER-lumenal chaperone function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Identified by mass spectrometry in melanosome fractions
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:23864651
  qualifier: enables
  review:
    summary: Interaction with the GLP-1 receptor (GLP1R/P43220) identified in a screen for GLP1R-interacting proteins. The bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: A specific interaction (GLP1R) consistent with ERP29 handling secretory/membrane clients, but the generic protein binding term is uninformative and not core.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'P30040; P43220: GLP1R; NbExp=2; IntAct=EBI-946830, EBI-7466542;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: Reference binary interactome capturing many ERP29 interactions (e.g. SGTA, SGTB, TMBIM6, UBQLN1/2). Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput binary interactions; the generic protein binding term is uninformative and not part of the core function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'P30040; O43765: SGTA; NbExp=3; IntAct=EBI-946830, EBI-347996;'
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: located_in
  review:
    summary: Extracellular/secreted pool inferred from the rat ortholog; peripheral to the ER chaperone role.
    action: KEEP_AS_NON_CORE
    reason: A secreted pool is reported (and ERP29 is detected at the cell surface), but this is secondary to its core ER-lumenal localization.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Melanosome.
- term:
    id: GO:0005790
    label: smooth endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: located_in
  review:
    summary: Smooth-ER localization inferred from the rat ortholog; a sub-compartment refinement of the ER localization.
    action: KEEP_AS_NON_CORE
    reason: A plausible ER sub-compartment annotation transferred by similarity; subsumed by the core ER/ER-lumen localization.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0006888
    label: endoplasmic reticulum to Golgi vesicle-mediated transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: ER-to-Golgi transport role inferred from the rat ortholog; consistent with ERP29's role in secretory-cargo trafficking. The falcon deep research corroborates a role in the early secretory pathway, with ERP29 cycling between ER and Golgi via the KDEL receptor (its weaker KEEL retention variant) to escort clients such as ENaC.
    action: KEEP_AS_NON_CORE
    reason: A plausible downstream trafficking process inferred by similarity; non-core relative to the chaperone molecular function. The falcon deep research provides additional (unverified) support for dynamic ER-to-Golgi cycling via the KDEL receptor and a role in client forward trafficking, reinforcing the biological plausibility of this process annotation.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Plays an important role in the processing of secretory proteins within the endoplasmic reticulum
    - reference_id: file:human/ERP29/ERP29-deep-research-falcon.md
      supporting_text: dynamic cycling between the ER and Golgi apparatus via interactions with the KDEL receptor
- term:
    id: GO:0009725
    label: response to hormone
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: A broad 'response to hormone' process inferred from the rat ortholog; vague and not characteristic of ERP29's molecular function.
    action: MARK_AS_OVER_ANNOTATED
    reason: An unspecific, by-similarity process annotation with no direct human evidence and no clear connection to ERP29's chaperone function; over-annotated.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-goa.tsv
      supporting_text: GO:0009725
- term:
    id: GO:0009986
    label: cell surface
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: located_in
  review:
    summary: Cell-surface localization inferred from the mouse ortholog; corroborated by direct evidence in platelets, but secondary to the ER role.
    action: KEEP_AS_NON_CORE
    reason: A genuine but minor surface pool (also IDA in platelets); peripheral to ERP29's core ER-lumenal chaperone function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Melanosome.
- term:
    id: GO:0042803
    label: protein homodimerization activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: ERP29 functions as a homodimer; homodimerization is a genuine structural property documented by UniProt and crystal structures.
    action: ACCEPT
    reason: ERP29 is a well-documented homodimer; homodimerization activity is correct, though it is structural rather than the principal client-facing function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBUNIT: Homodimer.'
- term:
    id: GO:0051087
    label: protein-folding chaperone binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: ERP29 binds molecular chaperones as part of a large ER chaperone complex (BiP, GRP94, PDI, ERdj3, cyclophilin B, ERp72, etc.) and, per the falcon deep research, is recruited to the calnexin/calreticulin (CNX/CRT) lectin-chaperone cycle, with its C-terminal D domain serving as the binding interface for the CNX/CRT P domains; chaperone binding is central to its escort function.
    action: ACCEPT
    reason: ERP29's participation in the ER chaperone multiprotein complex is experimentally documented; protein-folding chaperone binding is an informative, core molecular function. The falcon deep research adds a specific mechanistic basis - ERP29 is recruited as a function-specific co-chaperone within the calnexin/calreticulin cycle via direct binding of its D domain to the CNX/CRT P domains - consistent with this chaperone-binding annotation (these CNX/CRT-cycle citations were not independently verified against cached publications).
    supported_by:
    - reference_id: PMID:12475965
      supporting_text: large endoplasmic reticulum (ER)-localized multiprotein complex that is comprised of the molecular chaperones BiP
    - reference_id: file:human/ERP29/ERP29-deep-research-falcon.md
      supporting_text: C-terminal D domain serves as the principal binding interface for lectin chaperones in the calnexin/calreticulin system
- term:
    id: GO:1902235
    label: regulation of endoplasmic reticulum stress-induced intrinsic apoptotic signaling pathway
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: A role in regulating ER-stress-induced apoptosis inferred from the mouse ortholog; consistent with ERP29's ER-stress-related functions but indirect. The falcon deep research reports human-cell evidence (RPE cells) that ERP29 overexpression raises protective stress proteins (GRP78, p58IPK, Nrf2) and lowers pro-apoptotic CHOP, supporting a protective modulation of ER-stress-induced apoptotic signaling.
    action: KEEP_AS_NON_CORE
    reason: A plausible context-specific process inferred by similarity; non-core relative to the chaperone molecular function. The falcon deep research adds (unverified) supportive evidence that ERP29 attenuates ER stress and shifts the balance away from CHOP-driven apoptosis, consistent with this regulatory annotation though still peripheral to its core chaperone-binding function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Plays an important role in the processing of secretory proteins within the endoplasmic reticulum
    - reference_id: file:human/ERP29/ERP29-deep-research-falcon.md
      supporting_text: increased levels of protective stress response proteins including GRP78, p58IPK, and Nrf2, while reducing pro-apoptotic markers phospho-eIF2α and CHOP
- term:
    id: GO:0043410
    label: positive regulation of MAPK cascade
  evidence_type: IDA
  original_reference_id: PMID:22064321
  qualifier: involved_in
  review:
    summary: In breast cancer cells, ERP29 overexpression activates p38 MAPK and induces growth arrest; a cell-context-specific signaling effect.
    action: KEEP_AS_NON_CORE
    reason: Documented in a cancer-overexpression model; a specialized downstream signaling effect rather than ERP29's core ER chaperone function.
    supported_by:
    - reference_id: PMID:22064321
      supporting_text: ERp29-induced cancer cell growth arrest is modulated by the interplay between the concomitant phosphorylation of p38
- term:
    id: GO:0005790
    label: smooth endoplasmic reticulum
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    summary: ISS smooth-ER localization (rat ortholog); a sub-compartment refinement.
    action: KEEP_AS_NON_CORE
    reason: Redundant with the IEA smooth-ER annotation; subsumed by the core ER/ER-lumen localization.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0051087
    label: protein-folding chaperone binding
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: enables
  review:
    summary: ISS protein-folding chaperone binding (rat ortholog), consistent with ERP29's role in the ER chaperone complex.
    action: ACCEPT
    reason: Corroborates the experimentally supported chaperone-binding function (ER chaperone complex membership); an informative core molecular function.
    supported_by:
    - reference_id: PMID:12475965
      supporting_text: large endoplasmic reticulum (ER)-localized multiprotein complex that is comprised of the molecular chaperones BiP
- term:
    id: GO:0003756
    label: protein disulfide isomerase activity
  evidence_type: IKR
  original_reference_id: PMID:9738895
  qualifier: enables
  negated: true
  review:
    summary: This is a NOT (negated) annotation - ERP29 does NOT have protein disulfide isomerase activity, because it lacks the CXXC thioredoxin-box motif. The negation is correct.
    action: ACCEPT
    reason: Directly supported - ERP29 lacks the CXXC (CGHC) active-site motif and is not a disulfide isomerase; the NOT annotation correctly blocks transfer of isomerase activity. The falcon deep research independently affirms the redox-inactive, non-catalytic nature of ERP29 (lacks the CXXC catalytic motif; functions as a chaperone, not a catalyst).
    supported_by:
    - reference_id: PMID:9738895
      supporting_text: member of the protein disulfide isomerase family but lacks a CXXC thioredoxin-box motif
    - reference_id: file:human/ERP29/ERP29-deep-research-falcon.md
      supporting_text: lacks the characteristic CXXC catalytic motif
    - reference_id: file:human/ERP29/ERP29-deep-research-falcon.md
      supporting_text: establishing its primary role as a chaperone rather than a catalyst
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: PMID:9738895
  qualifier: located_in
  review:
    summary: Direct evidence (fractionation and immunofluorescence) for ER localization.
    action: ACCEPT
    reason: IDA-supported ER localization from the founding characterization.
    supported_by:
    - reference_id: PMID:9738895
      supporting_text: localizes to the endoplasmic reticulum (ER) as seen by subcellular fractionation and immunofluorescence studies
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: NAS
  original_reference_id: PMID:22064321
  qualifier: located_in
  review:
    summary: ER-lumen localization asserted in the literature; correct and core.
    action: ACCEPT
    reason: ERP29 is a soluble ER-lumenal protein; consistent with its retention signal and direct localization data.
    supported_by:
    - reference_id: PMID:22064321
      supporting_text: ERp29) is an ER luminal protein
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: NAS
  original_reference_id: PMID:9738895
  qualifier: involved_in
  review:
    summary: ERP29 may participate in folding of secretory proteins as a non-catalytic chaperone; protein folding is a plausible downstream process.
    action: KEEP_AS_NON_CORE
    reason: ERP29 assists folding indirectly as an escort/chaperone (it is not a foldase); protein folding is a non-core process annotation.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: possibly by participating in the folding of proteins in the ER
- term:
    id: GO:0006886
    label: intracellular protein transport
  evidence_type: NAS
  original_reference_id: PMID:9738895
  qualifier: involved_in
  review:
    summary: ERP29 participates in the trafficking/processing of secretory proteins; intracellular protein transport is a plausible downstream process.
    action: KEEP_AS_NON_CORE
    reason: A reasonable downstream process consequence of ERP29's escort/chaperone role; non-core relative to its molecular function.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: Plays an important role in the processing of secretory proteins within the endoplasmic reticulum
- term:
    id: GO:0010628
    label: positive regulation of gene expression
  evidence_type: IDA
  original_reference_id: PMID:22064321
  qualifier: involved_in
  review:
    summary: In a breast-cancer overexpression model, ERP29 modulates gene expression (e.g. upregulation of p58IPK); a context-specific downstream effect.
    action: KEEP_AS_NON_CORE
    reason: A specialized, cell-context-specific transcriptional effect from an overexpression study; not ERP29's core ER chaperone function.
    supported_by:
    - reference_id: PMID:22064321
      supporting_text: upregulation of the inhibitor of the interferon-induced, double-stranded RNA-activated protein kinase, p58(IPK)
- term:
    id: GO:0010629
    label: negative regulation of gene expression
  evidence_type: IDA
  original_reference_id: PMID:22064321
  qualifier: involved_in
  review:
    summary: ERP29 also negatively regulates expression of certain genes in the cancer-cell model; a context-specific downstream effect.
    action: KEEP_AS_NON_CORE
    reason: A specialized transcriptional effect in an overexpression model; non-core relative to the chaperone function.
    supported_by:
    - reference_id: PMID:22064321
      supporting_text: ERp29-induced cancer cell growth arrest
- term:
    id: GO:0043335
    label: protein unfolding
  evidence_type: NAS
  original_reference_id: PMID:22064321
  qualifier: involved_in
  review:
    summary: ERP29 has been proposed to have a protein-unfolding activity (e.g. in toxin/virus membrane penetration); asserted in the literature but mechanistically limited.
    action: KEEP_AS_NON_CORE
    reason: A proposed specialized activity (substrate unfolding/local conformational change) rather than ERP29's principal chaperone-binding function; retained as non-core.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: a role in protein unfolding and secretion
- term:
    id: GO:0050709
    label: negative regulation of protein secretion
  evidence_type: IDA
  original_reference_id: PMID:22064321
  qualifier: involved_in
  review:
    summary: ERP29 overexpression can negatively regulate secretion of specific proteins in the cancer model; a context-specific effect.
    action: KEEP_AS_NON_CORE
    reason: A specialized, context-dependent secretion-regulation effect; non-core relative to the chaperone function.
    supported_by:
    - reference_id: PMID:22064321
      supporting_text: ERp29) is an ER luminal protein that has a role in protein unfolding and secretion
- term:
    id: GO:0016020
    label: membrane
  evidence_type: HDA
  original_reference_id: PMID:19946888
  qualifier: located_in
  review:
    summary: High-throughput membrane-proteome detection; generic and uninformative for this soluble ER-lumenal protein (likely reflects ER-membrane-associated complexes or surface pool).
    action: KEEP_AS_NON_CORE
    reason: A generic proteomic localization; uninformative relative to the precise ER-lumen localization.
    supported_by:
    - reference_id: file:human/ERP29/ERP29-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0009986
    label: cell surface
  evidence_type: IDA
  original_reference_id: PMID:19995400
  qualifier: located_in
  review:
    summary: Direct evidence that ERP29 (a thiol-isomerase-family protein) is released by platelets and recruited to the cell surface upon activation; a genuine but specialized surface pool.
    action: KEEP_AS_NON_CORE
    reason: A real activation-dependent surface pool in platelets, but peripheral to ERP29's core ER-lumenal chaperone function.
    supported_by:
    - reference_id: PMID:19995400
      supporting_text: Platelets release novel thiol isomerase enzymes which are recruited to the cell surface following activation
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- 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:0000044
  title: Gene Ontology annotation based on UniProtKB Subcellular Location vocabulary mapping
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:9738895
  title: ERp28, a human endoplasmic-reticulum-lumenal protein, is a member of the protein disulfide isomerase family but lacks a CXXC thioredoxin-box motif.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: "Cached publications/PMID_9738895.md title matches YAML; establishes ERP29 as an ER-lumenal PDI-family member lacking the CXXC motif (non-catalytic), central to its core chaperone/escort identity. GOA anchors this PMID to GO:0005783 (ER, IDA) and GO:0003756 (IKR, i.e. NOT a disulfide isomerase)."
  findings:
  - statement: ERp28/ERp29 is an ER-lumenal protein with a KEEL retention signal that is a PDI-family member but lacks the CXXC (CGHC) thioredoxin-box motif, hence is not a disulfide isomerase.
    reference_section_type: ABSTRACT
- id: PMID:12475965
  title: A subset of chaperones and folding enzymes form multiprotein complexes in endoplasmic reticulum to bind nascent proteins.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: "Cached publications/PMID_12475965.md title matches YAML; supports the core MF (protein-folding chaperone binding) by showing ERP29 participates in ER multiprotein chaperone/folding-enzyme complexes binding nascent proteins."
  findings:
  - statement: ERp29 is part of a large ER chaperone multiprotein complex (BiP, GRP94, PDI, ERdj3, cyclophilin B, ERp72, GRP170, UGGT, SDF2-L1) that binds unassembled, incompletely folded immunoglobulin heavy chains.
    reference_section_type: RESULTS
- id: PMID:19946888
  title: Defining the membrane proteome of NK cells.
  findings: []
- id: PMID:19995400
  title: Platelets release novel thiol isomerase enzymes which are recruited to the cell surface following activation.
  findings:
  - statement: ERP29 is among thiol-isomerase-family proteins released by platelets and recruited to the platelet surface following activation.
    reference_section_type: RESULTS
- id: PMID:22064321
  title: ERp29 induces breast cancer cell growth arrest and survival through modulation of activation of p38 and upregulation of ER stress protein p58IPK.
  findings:
  - statement: In breast cancer cells, ERp29 (an ER luminal protein with a role in protein unfolding and secretion) overexpression induces growth arrest via p38 MAPK activation and upregulation of p58IPK, modulating gene expression and protein secretion.
    reference_section_type: ABSTRACT
- id: PMID:23864651
  title: The identification of novel proteins that interact with the GLP-1 receptor and restrain its activity.
  findings: []
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
- id: file:human/ERP29/ERP29-uniprot.txt
  title: UniProt entry P30040 (ERP29_HUMAN), Endoplasmic reticulum resident protein 29
  findings:
  - statement: Non-catalytic (no CXXC) PDI-family ER-lumenal homodimeric chaperone that assists processing/folding of secretory proteins; part of a large ER chaperone complex; KEEL ER-retention signal; also detected in melanosomes and at the cell surface.
    reference_section_type: OTHER
- id: file:human/ERP29/ERP29-deep-research-falcon.md
  title: Falcon deep research report for ERP29
  reference_review:
    relevance: MEDIUM
    correctness: UNVERIFIED
    review_notes: "LLM-synthesized (Edison/Falcon) deep-research report; its underlying primary citations (Kozlov 2017, Bikard 2019, Baryshev 2004, Huang 2015, etc.) are NOT in the publications cache and were not independently verified here, hence UNVERIFIED. The report is consistent with the established ERP29-specific picture: it correctly frames ERP29 as a non-catalytic, CXXC-lacking PDI-family chaperone (NOT a disulfide isomerase) and as a calnexin/calreticulin (CNX/CRT) co-chaperone whose D domain binds the CNX/CRT P domains. CAUTION: the report carries PDI-family background on oxidoreductase/disulfide-isomerase catalysis by family analogy; do NOT attribute any disulfide isomerase / oxidoreductase catalytic activity to the redox-inactive ERP29 on that basis. Used here only to strengthen non-catalytic chaperone-binding, ER-stress, and early-secretory-pathway trafficking annotations with verbatim quotes."
  findings:
  - statement: ERP29 lacks the characteristic CXXC catalytic motif of classical PDIs and acts as a chaperone rather than a catalyst; it is recruited to the calnexin/calreticulin cycle, its C-terminal D domain being the principal interface that binds the CNX/CRT P domains, and it cycles between ER and Golgi via the KDEL receptor (KEEL motif) to assist early-secretory-pathway folding/trafficking of clients such as thyroglobulin and ENaC.
    reference_section_type: OTHER
core_functions:
- description: Non-catalytic, ER-lumenal escort/chaperone of the PDI family (lacking a CXXC active site) that assists the folding, processing and trafficking of secretory cargo by binding molecular chaperones within a large ER chaperone multiprotein complex.
  molecular_function:
    id: GO:0051087
    label: protein-folding chaperone binding
  locations:
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  supported_by:
  - reference_id: PMID:12475965
    supporting_text: large endoplasmic reticulum (ER)-localized multiprotein complex that is comprised of the molecular chaperones BiP
  - reference_id: file:human/ERP29/ERP29-uniprot.txt
    supporting_text: Plays an important role in the processing of secretory proteins within the endoplasmic reticulum
proposed_new_terms: []
suggested_questions:
- question: What is the precise molecular contribution of ERP29 within the ER chaperone complex - does it have client specificity (e.g. thyroglobulin, connexins) distinct from its homodimerization and chaperone-binding roles?
- question: Are the cancer-associated signaling phenotypes (p38 MAPK, gene-expression and secretion control) a direct consequence of ERP29's ER chaperone function or secondary to altered ER proteostasis?
suggested_experiments:
- description: Reconstitute ERP29 within the ER chaperone complex and test, with defined unfolded clients, whether ERP29 modulates client binding, folding kinetics or release relative to ERP29-depleted complexes.
- description: ERP29 knockout/knockdown in secretory cell types followed by secretome and client-folding analysis (e.g. thyroglobulin, connexin trafficking) to define its non-redundant chaperone clients.