DNAJC5G (cysteine string protein-gamma, CSP-gamma) is a testis-specific, poorly characterized paralog of the synaptic co-chaperone CSPalpha/DNAJC5. It carries an N-terminal J domain characteristic of DnaJ/HSP40 co-chaperones, which in characterized family members recruits and stimulates the HSP70 chaperone HSC70/HSPA8, together with a cysteine-string region that is predicted to be palmitoylated and to anchor the protein to membranes. No direct biochemical characterization of CSP-gamma's activity or clients has been reported; its function is inferred from family membership to be HSP70 co-chaperone activity in a testis secretory/membrane context.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005737
cytoplasm
|
IEA
GO_REF:0000117 |
KEEP AS NON CORE |
Summary: Electronic cytoplasm annotation from ARBA, consistent with a J-domain co-chaperone that is membrane-anchored with a cytoplasmic-facing pool.
Reason: Generic cytoplasm localization; plausible for a CSP-family co-chaperone but not experimentally established for CSP-gamma and less informative than the membrane lipid-anchor.
Supporting Evidence:
file:human/DNAJC5G/DNAJC5G-uniprot.txt
Cysteine string protein-gamma
|
|
GO:0016020
membrane
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: Membrane localization from UniProt subcellular-location mapping; CSP-gamma is annotated as a lipid-anchored membrane protein by similarity to other cysteine string proteins. The falcon deep-research synthesis reaches the same family-level inference (palmitoylation-dependent membrane anchoring), and additionally notes DNAJC5G-specific proteomic detection in human sperm with a ring-shaped headpiece antibody-staining pattern, consistent with association with a membrane-bounded germ-cell compartment.
Reason: Consistent with the predicted palmitoylated cysteine-string membrane anchor shared across the CSP family; membrane is the best-supported compartment. The gene-specific sperm staining (ring-shaped headpiece) is consistent with, though does not pinpoint, a membrane-associated localization.
Supporting Evidence:
file:human/DNAJC5G/DNAJC5G-uniprot.txt
SUBCELLULAR LOCATION: Membrane
file:human/DNAJC5G/DNAJC5G-deep-research-falcon.md
ring-shaped in the headpiece
|
Q: Does CSP-gamma function as an HSC70/HSP70 co-chaperone (J-domain-dependent ATPase stimulation), and what is its testis-specific physiological role?
Q: Is CSP-gamma palmitoylated and membrane-anchored in vivo as predicted, and to which membrane compartment is it targeted in germ cells?
Experiment: In vitro HSC70 ATPase assays with purified CSP-gamma (wild-type and J-domain HPD-motif mutant) to test for co-chaperone activity.
Experiment: Tagged-CSP-gamma expression and affinity purification-mass spectrometry from a testis-derived line to determine subcellular localization and identify interaction partners/clients.
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The gene symbol DNAJC5G (UniProt: Q8N7S2) correctly identifies DnaJ homolog subfamily C member 5G, also known as cysteine string protein-gamma (CSP-gamma or CSPγ), in Homo sapiens (rosene2025cysteinestringprotein pages 2-3, huang2022cspαinneurodegenerative pages 1-2). This protein is one of three mammalian cysteine string protein paralogs, the others being DNAJC5/DNAJC5A (encoding CSPα) and DNAJC5B (encoding CSPβ) (huang2022cspαinneurodegenerative pages 1-2, huang2022cspαinneurodegenerative pages 2-3). The human DNAJC5G gene is located on chromosome 2 and encodes a transcript (ENST00000296097.8) with 7 exons (4 coding) producing a protein of approximately 189 amino acids (rosene2025cysteinestringprotein pages 2-3).
DNAJC5G belongs to the DnaJ/Hsp40 family of co-chaperones, specifically the highly diverse class C (DNAJC) proteins (qiu2006thediversityof pages 1-2, zarouchlioti2018dnajproteinsin pages 1-2). The DnaJ/Hsp40 family is characterized by the presence of a conserved J-domain of approximately 70 amino acids, which is essential for interaction with Hsp70 chaperones (qiu2006thediversityof pages 1-2). The J-domain contains four α-helices with a highly conserved histidine-proline-aspartic acid (HPD) motif located in the linker region between helices II and III, which is critical for stimulating ATP hydrolysis in Hsp70 proteins (qiu2006thediversityof pages 1-2, zarouchlioti2018dnajproteinsin pages 1-2).
Based on UniProt annotation and family homology, DNAJC5G contains:
While the complete structural organization of DNAJC5G has not been directly characterized in the literature, its classification as a cysteine string protein and membership in the DNAJC5 subfamily suggest a domain architecture similar to CSPα, which consists of an N-terminal region, J-domain, cysteine string domain, hydrophobic linker, and C-terminal domain (rosene2025cysteinestringprotein pages 2-3, burgoyne2015cysteinestringprotein pages 1-2).
DNAJC5G functions as a DnaJ/Hsp40 co-chaperone that regulates Hsp70 chaperone activity (qiu2006thediversityof pages 1-2, huang2022cspαinneurodegenerative pages 2-3). The molecular mechanism, inferred from well-established DnaJ family function, involves:
Direct experimental evidence for DNAJC5G-specific client proteins or substrates is not available in the retrieved literature. DNAJC5G is not an enzyme and does not catalyze a specific biochemical reaction; rather, its primary biochemical role is modulating Hsp70 chaperone activity (qiu2006thediversityof pages 1-2). For comparison, CSPα has well-defined client proteins including SNAP-25 and dynamin in neurons, but such specific substrate information has not been established for CSPγ (burgoyne2015cysteinestringprotein pages 1-2, rosene2025cysteinestringprotein pages 3-4, huang2022cspαinneurodegenerative pages 2-3).
Like other DNAJC5 family members, the cysteine-rich domain can undergo palmitoylation (attachment of palmitic acid to cysteine residues via thioester bonds), which enables targeting to lipid membranes (huang2022cspαinneurodegenerative pages 2-3, rosene2025cysteinestringprotein pages 2-3). This post-translational modification is critical for the localization and function of cysteine string proteins (huang2022cspαinneurodegenerative pages 1-2, burgoyne2015cysteinestringprotein pages 1-2).
Unlike DNAJC5/CSPα, which is widely expressed in neuronal and other secretory cells, DNAJC5G expression is highly restricted to specific tissues (huang2022cspαinneurodegenerative pages 1-2, rosene2025cysteinestringprotein pages 2-3). The primary sites of expression include:
This restricted expression pattern is shared with DNAJC5B/CSPβ, which is also predominantly expressed in testis and select nervous system regions, in contrast to the broader expression of CSPα (rosene2025cysteinestringprotein pages 2-3, huang2022cspαinneurodegenerative pages 1-2, chen2025dnajc5bcontributesto pages 1-2).
In the human brain, DNAJC5G is highly expressed in intratelencephalic cortical neurons (layers 2-6 IT neurons) (rosene2025cysteinestringprotein pages 2-3). These neurons have been implicated in various neurodegenerative diseases, suggesting potential relevance to neurological function.
In the male reproductive system, immunohistochemical studies have demonstrated that DNAJC5G protein is present in germ cells throughout spermatogenesis, with immunoreactivity observed in all germ cells up to the cytoplasmic lobes of elongated spermatids (carapito2017validatingmissingproteins pages 1-5). This localization suggests a potential role in germ cell maturation or spermiogenesis.
One recent review reported that CSPγ is found in the endoplasmic reticulum (ER) lumen (rosene2025cysteinestringprotein pages 2-3), which would distinguish it from CSPα that is predominantly membrane-bound on synaptic vesicles and other secretory vesicles (burgoyne2015cysteinestringprotein pages 1-2, huang2022cspαinneurodegenerative pages 2-3). However, this ER localization for DNAJC5G appears to be based on limited evidence and requires further experimental validation. The presence in germ cells has been confirmed by direct immunohistochemistry in human testis samples (carapito2017validatingmissingproteins pages 1-5).
DNAJC5G participates in the Hsp70/Hsp40 chaperone network, which is central to cellular proteostasis (protein homeostasis) (qiu2006thediversityof pages 1-2, huang2022cspαinneurodegenerative pages 2-3). This network is involved in:
As a member of the DnaJ/Hsp40 family, DNAJC5G is part of the broader heat shock response (HSR) and cellular stress response systems (rosene2025cysteinestringprotein pages 1-2, huang2022cspαinneurodegenerative pages 2-3). The heat shock response is coordinated by heat shock transcription factors and involves upregulation of molecular chaperones to protect cells from proteotoxic stress (rosene2025cysteinestringprotein pages 1-2).
Given the reported ER localization, DNAJC5G may participate in the unfolded protein response (UPR), a cellular stress response related to ER stress (gessner2017analysisofhepatic pages 1-2, huang2022cspαinneurodegenerative pages 2-3). The UPR is activated when unfolded or misfolded proteins accumulate in the ER lumen, disturbing ER homeostasis (gessner2017analysisofhepatic pages 1-2). However, direct experimental evidence linking DNAJC5G to UPR pathways is lacking in the current literature.
The prominent expression of DNAJC5G in testis germ cells suggests involvement in spermatogenesis or related reproductive processes (carapito2017validatingmissingproteins pages 1-5, rosene2025cysteinestringprotein pages 2-3). Recent studies on the related protein DNAJC5B have demonstrated critical roles in male fertility, including maintenance of mitochondrial function and regulation of autophagy during spermiogenesis (chen2025dnajc5bcontributesto pages 1-2, chen2025dnajc5bcontributesto pages 2-4). While direct evidence for DNAJC5G in these processes is absent, the expression pattern and family relationship suggest analogous functions may exist.
While specific DNAJC5G research remains limited, recent publications (2023-2025) on related DNAJC5 family members provide important context:
Rosene & Benitez (2025) published a comprehensive review linking CSPα to both rare and common neurodegenerative dementias, highlighting the protective role of DNAJC5 family proteins in synaptic maintenance and protein quality control (rosene2025cysteinestringprotein pages 1-2, rosene2025cysteinestringprotein pages 2-3). This review emphasizes the role of CSPα in endolysosomal function and the exocytosis of aggregate-prone proteins through misfolding-associated protein secretion (MAPS) pathways.
Chen et al. (2025) demonstrated that DNAJC5B contributes to male fertility by maintaining mitochondrial functions and autophagic homeostasis during spermiogenesis (chen2025dnajc5bcontributesto pages 1-2, chen2025dnajc5bcontributesto pages 2-4). Using germ cell-conditional knockout mice, they showed that DNAJC5B deficiency leads to subfertility, abnormal spermatozoa, and mitochondrial damage. The protein regulates autophagy and mitophagy via its DNAJ domain under stress conditions.
Barker et al. (2024) used proximity labeling to define the CSPα interactome in neuronal model cells, confirming known interactions with Hsc70 and SNAP-25 while identifying novel binding partners including STXBP1/Munc18-1 (rosene2025cysteinestringprotein pages 1-2). This work demonstrated that disease-causing mutations affect specific protein-protein interactions.
These recent studies underscore the importance of DNAJC5 family proteins in proteostasis, neurodegeneration, and reproductive function, providing a framework for understanding potential DNAJC5G functions.
Based on available evidence, the following can be stated with high confidence:
Several key aspects of DNAJC5G biology remain poorly characterized:
Much of the current functional annotation for DNAJC5G relies on inference from better-studied family members, particularly CSPα. While this provides a reasonable framework for hypothesis generation, direct experimental validation specific to DNAJC5G is needed. The restricted expression pattern suggests DNAJC5G may have specialized functions distinct from the broadly expressed CSPα.
| Category | DNAJC5G (CSPγ) summary | Comparison / context within DNAJC5 family |
|---|---|---|
| Verified identity | Human DNAJC5G encodes DnaJ homolog subfamily C member 5G / cysteine string protein-gamma (CSPγ); the user-supplied UniProt accession is Q8N7S2. Recent review literature explicitly identifies CSPγ as the product of DNAJC5G and distinguishes it from DNAJC5/DNAJC5A (CSPα) and DNAJC5B (CSPβ) (rosene2025cysteinestringprotein pages 2-3, huang2022cspαinneurodegenerative pages 1-2) | CSPα is encoded by DNAJC5/DNAJC5A on chromosome 20 and is the best-studied paralog; CSPβ is encoded by DNAJC5B; CSPγ is encoded by DNAJC5G (rosene2025cysteinestringprotein pages 2-3, huang2022cspαinneurodegenerative pages 1-2) |
| Gene information | Gene: DNAJC5G; Protein name: cysteine string protein-gamma; Organism: Homo sapiens; Chromosomal location: chromosome 2; one recent review reports transcript model details for human DNAJC5G as ENST00000296097.8, 7 exons, 4 coding exons, transcript length 2065 bp, translation length 189 aa (rosene2025cysteinestringprotein pages 2-3) | Human DNAJC5/DNAJC5A (CSPα) is on chromosome 20 and encodes a 198 aa protein; human DNAJC5B (CSPβ) is on chromosome 8 and encodes a 199 aa protein (rosene2025cysteinestringprotein pages 2-3) |
| Protein family / domain class | DNAJC5G belongs to the DnaJ/Hsp40 (J-domain protein, JDP) family, specifically class C / DNAJC proteins, which share a conserved J-domain but otherwise show high structural diversity (qiu2006thediversityof pages 1-2, chen2025dnajc5bcontributesto pages 2-4, zarouchlioti2018dnajproteinsin pages 1-2) | DNAJC5 family members are described as cysteine string proteins because they contain a cysteine-rich segment; the family includes DNAJC5/CSPα, DNAJC5B/CSPβ, DNAJC5G/CSPγ (chen2025dnajc5bcontributesto pages 1-2, huang2022cspαinneurodegenerative pages 1-2) |
| Core structural features | Direct DNAJC5G structural studies are scarce, but by sequence/domain annotation and family analogy it is expected to contain a J-domain plus a cysteine-string / cysteine-rich domain that can support lipid modification and membrane association. The supplied UniProt/domain data list DnaJ_domain, DnaJ_domain_CS, and DnaJ_C_subfamily_member5; family reviews state DNAJC5 proteins are “cysteine-string proteins” because of the cysteine-rich segment (qiu2006thediversityof pages 1-2, chen2025dnajc5bcontributesto pages 1-2, rosene2025cysteinestringprotein pages 2-3) | CSPα architecture is well defined: N-terminus, J-domain, central cysteine string domain (CSD), linker/hydrophobic segment, and C-terminus; palmitoylation of the CSD is critical for membrane targeting. This is the strongest template for inferring analogous organization in CSPγ (huang2022cspαinneurodegenerative pages 1-2, burgoyne2015cysteinestringprotein pages 1-2, rosene2025cysteinestringprotein pages 2-3) |
| Molecular function | The most defensible functional assignment is that DNAJC5G is a DnaJ/Hsp40 co-chaperone. In the DnaJ/Hsp40 system, the J-domain binds Hsp70-family chaperones and the conserved HPD motif stimulates Hsp70 ATP hydrolysis, thereby promoting client capture/folding and broader proteostasis functions including folding, unfolding, translocation, and degradation (qiu2006thediversityof pages 1-2, huang2022cspαinneurodegenerative pages 2-3, rosene2025cysteinestringprotein pages 1-2) | CSPα is experimentally established as a membrane-associated co-chaperone acting with HSC70/HSPA8 and sometimes HSP70/HSP90-linked systems in proteostasis and exocytic pathways. DNAJC5G likely shares the upstream Hsp70-cofactor logic, but this has not been shown in equivalent detail for CSPγ (huang2022cspαinneurodegenerative pages 2-3, rosene2025cysteinestringprotein pages 3-4, rosene2025cysteinestringprotein pages 2-3) |
| Enzymatic / substrate specificity | DNAJC5G is not known to be an enzyme; no catalytic reaction or direct substrate specificity has been established in the retrieved literature. Its primary biochemical role is more likely co-chaperone-mediated regulation of Hsp70 activity rather than catalysis (qiu2006thediversityof pages 1-2, zarouchlioti2018dnajproteinsin pages 1-2) | For CSPα, specific client proteins such as SNAP-25 and dynamin have been defined experimentally in neurons, but no comparable DNAJC5G-specific client set was found (burgoyne2015cysteinestringprotein pages 1-2, rosene2025cysteinestringprotein pages 3-4, huang2022cspαinneurodegenerative pages 2-3) |
| Tissue expression | Expression of DNAJC5G is restricted, with strongest evidence for testis and selected CNS regions. A recent review states that DNAJC5G expression is limited to testis and selected CNS regions including cortex and BA9 frontal cortex (rosene2025cysteinestringprotein pages 2-3) | CSPα is mainly neuronal/secretory-cell enriched and broadly linked to synapses; CSPβ is predominantly testis-enriched, although some nervous-system expression has also been reported (huang2022cspαinneurodegenerative pages 1-2, rosene2025cysteinestringprotein pages 2-3, chen2025dnajc5bcontributesto pages 1-2) |
| Cell-type localization | In the human brain, DNAJC5G is reported to be highly expressed in intratelencephalic cortical neurons (L2-L6 IT) (rosene2025cysteinestringprotein pages 2-3) | This restricted neuronal expression differs from CSPα, which is strongly associated with presynaptic terminals across many neuronal populations (rosene2025cysteinestringprotein pages 2-3, burgoyne2015cysteinestringprotein pages 1-2) |
| Subcellular localization | One recent review states CSPγ is found in the ER lumen, but this point appears to rely on limited prior evidence and is less mature than the CSPα localization literature (rosene2025cysteinestringprotein pages 2-3). Independent direct localization work retrieved here is sparse. | CSPα is much better established as a membrane-bound palmitoylated protein associated with synaptic vesicles, other secretory vesicles, cell membranes, and endolysosomal compartments depending on cell type (burgoyne2015cysteinestringprotein pages 1-2, huang2022cspαinneurodegenerative pages 2-3, rosene2025cysteinestringprotein pages 3-4) |
| Testis / germ-cell evidence | Human sperm/testis proteomics and immunohistochemistry provide direct evidence that DNAJC5G protein is present in the male germ line: DNAJC5G immunoreactivity was seen in all germ cells up to the cytoplasmic lobes of elongated spermatids (carapito2017validatingmissingproteins pages 1-5, carapito2017validatingmissingproteins pages 9-13) | This supports the idea that CSPγ, like CSPβ, may function in spermatogenic or sperm-cell proteostasis, though direct mechanism is unresolved (carapito2017validatingmissingproteins pages 1-5, chen2025dnajc5bcontributesto pages 1-2) |
| Interacting partners | No DNAJC5G-specific interacting partners were identified in the retrieved literature. By family logic, the most likely conserved interaction is with Hsp70/Hsc70 chaperones through the J-domain (qiu2006thediversityof pages 1-2, huang2022cspαinneurodegenerative pages 2-3) | CSPα has documented interactions with HSC70/HSPA8, HSP70, SGT, Rab-αGDI, and client proteins such as SNAP-25, dynamin, and STXBP1/Munc18-1; these data should not be over-transferred to DNAJC5G without direct evidence (huang2022cspαinneurodegenerative pages 2-3, rosene2025cysteinestringprotein pages 3-4, rosene2025cysteinestringprotein pages 2-3) |
| Biological pathways / processes | The best-supported pathway assignment is participation in the Hsp70/Hsp40 proteostasis network, including protein quality control, stress-response-linked folding pathways, and possibly ER-associated quality control given the reported ER localization. Testis-restricted expression suggests relevance to spermatogenesis / germ-cell maturation (qiu2006thediversityof pages 1-2, chen2025dnajc5bcontributesto pages 2-4, rosene2025cysteinestringprotein pages 2-3, carapito2017validatingmissingproteins pages 1-5) | CSPα is additionally tied to synaptic vesicle exocytosis, SNARE complex maintenance, endolysosomal trafficking, and misfolding-associated protein secretion (MAPS); CSPβ has emerging links to male fertility, mitochondrial function, and autophagy control in spermiogenesis (rosene2025cysteinestringprotein pages 3-4, huang2022cspαinneurodegenerative pages 2-3, chen2025dnajc5bcontributesto pages 1-2) |
| Disease / phenotype evidence | The retrieved literature contains very limited direct disease evidence for DNAJC5G. No clear Mendelian disorder or disease mechanism specific to human DNAJC5G was established in the sources examined. | By contrast, DNAJC5/CSPα mutations cause autosomal dominant neuronal ceroid lipofuscinosis (ANCL/CLN4); DNAJC5B/CSPβ has recent functional evidence in male fertility models, but not the same human disease depth (naseri2021autosomaldominantneuronal pages 1-2, naseri2021autosomaldominantneuronal pages 2-3, chen2025dnajc5bcontributesto pages 1-2) |
| Current interpretation / evidence strength | High confidence: identity, family membership, restricted expression in testis and selected brain regions, germ-cell protein detection, and co-chaperone inference from the J-domain. Low-to-moderate confidence: precise subcellular localization, client proteins, and pathway-specific mechanism unique to DNAJC5G because direct experiments are sparse (rosene2025cysteinestringprotein pages 2-3, carapito2017validatingmissingproteins pages 1-5, qiu2006thediversityof pages 1-2) | DNAJC5G remains a poorly characterized paralog relative to CSPα and CSPβ; therefore, functional annotation should rely on direct evidence where available and otherwise be explicitly framed as family-based inference (rosene2025cysteinestringprotein pages 2-3, huang2022cspαinneurodegenerative pages 1-2, chen2025dnajc5bcontributesto pages 1-2) |
Table: This table compiles verified identity, structure, localization, inferred function, pathways, and family comparisons for human DNAJC5G/CSPγ. It is especially useful because direct DNAJC5G literature is limited, so the table distinguishes direct evidence from inference based on better-studied DNAJC5 family members.
DNAJC5G encodes cysteine string protein-gamma (CSPγ), a member of the DNAJC5 family of DnaJ/Hsp40 co-chaperones in humans. The protein contains a conserved J-domain that enables interaction with Hsp70 chaperones and a cysteine-rich domain for potential membrane targeting via palmitoylation. DNAJC5G functions as a co-chaperone that stimulates Hsp70 ATPase activity through its HPD motif, thereby facilitating protein folding, quality control, and proteostasis.
Expression of DNAJC5G is highly restricted compared to its paralog CSPα, being primarily detected in testis (specifically in germ cells during spermatogenesis) and select cortical brain regions (intratelencephalic neurons). This restricted pattern suggests specialized roles in reproductive and neuronal functions, though the precise biological processes requiring DNAJC5G remain to be elucidated.
The protein likely participates in the Hsp70/Hsp40 chaperone network involved in protein quality control, heat shock response, and potentially ER stress response pathways. However, unlike CSPα which has well-defined roles in synaptic vesicle exocytosis, SNARE complex maintenance, and has been linked to neurodegenerative disease, DNAJC5G remains poorly characterized with no identified client proteins, validated disease associations, or direct functional studies.
Recent developments (2023-2025) in understanding related family members CSPα and CSPβ have highlighted their roles in neurodegeneration, synaptic maintenance, male fertility, mitochondrial function, and autophagy regulation. These findings provide important context for future DNAJC5G research, particularly given the shared testicular expression and structural features among family members.
Critical Note on Evidence: Due to the paucity of DNAJC5G-specific literature, this report necessarily relies heavily on extrapolation from related DNAJC5 family members. Direct experimental characterization of DNAJC5G is needed to validate inferred functions and identify unique roles for this understudied co-chaperone.
References
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(naseri2021autosomaldominantneuronal pages 1-2): Nima Naseri, Manu Sharma, and Milen Velinov. Autosomal dominant neuronal ceroid lipofuscinosis: clinical features and molecular basis. Aug 2021. URL: https://doi.org/10.1111/cge.13829, doi:10.1111/cge.13829. This article has 50 citations and is from a peer-reviewed journal.
(naseri2021autosomaldominantneuronal pages 2-3): Nima Naseri, Manu Sharma, and Milen Velinov. Autosomal dominant neuronal ceroid lipofuscinosis: clinical features and molecular basis. Aug 2021. URL: https://doi.org/10.1111/cge.13829, doi:10.1111/cge.13829. This article has 50 citations and is from a peer-reviewed journal.
(carapito2017validatingmissingproteins pages 9-13): Christine Carapito, Paula Duek, Charlotte Macron, Marine Seffals, Karine Rondel, François Delalande, Cecilia Lindskog, Thomas Fréour, Yves Vandenbrouck, Lydie Lane, and Charles Pineau. Validating missing proteins in human sperm cells by targeted mass-spectrometry- and antibody-based methods. Journal of proteome research, 16 12:4340-4351, Sep 2017. URL: https://doi.org/10.1021/acs.jproteome.7b00374, doi:10.1021/acs.jproteome.7b00374. This article has 26 citations and is from a peer-reviewed journal.
*-deep-research*.md file found in this gene directory.ER proteostasis|Chaperone|HSP70 system|J-domain containing HSP70 cochaperone (branch ER) ; PN-node mapping: type → mapped/ok_for_propagation_to_go GO:0030544 Hsp70 protein binding (goa_status=new_to_goa); all ancestor nodes no_mapping.This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.
id: Q8N7S2
gene_symbol: DNAJC5G
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: DNAJC5G (cysteine string protein-gamma, CSP-gamma) is a testis-specific,
poorly characterized paralog of the synaptic co-chaperone CSPalpha/DNAJC5. It carries
an N-terminal J domain characteristic of DnaJ/HSP40 co-chaperones, which in characterized
family members recruits and stimulates the HSP70 chaperone HSC70/HSPA8, together
with a cysteine-string region that is predicted to be palmitoylated and to anchor
the protein to membranes. No direct biochemical characterization of CSP-gamma's
activity or clients has been reported; its function is inferred from family membership
to be HSP70 co-chaperone activity in a testis secretory/membrane context.
alternative_products:
- name: '1'
id: Q8N7S2-1
- name: '2'
id: Q8N7S2-2
sequence_note: VSP_056967, VSP_056968
existing_annotations:
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IEA
original_reference_id: GO_REF:0000117
qualifier: located_in
review:
summary: Electronic cytoplasm annotation from ARBA, consistent with a J-domain
co-chaperone that is membrane-anchored with a cytoplasmic-facing pool.
action: KEEP_AS_NON_CORE
reason: Generic cytoplasm localization; plausible for a CSP-family co-chaperone
but not experimentally established for CSP-gamma and less informative than the
membrane lipid-anchor.
supported_by:
- reference_id: file:human/DNAJC5G/DNAJC5G-uniprot.txt
supporting_text: Cysteine string protein-gamma
- term:
id: GO:0016020
label: membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: Membrane localization from UniProt subcellular-location mapping; CSP-gamma
is annotated as a lipid-anchored membrane protein by similarity to other cysteine
string proteins. The falcon deep-research synthesis reaches the same family-level
inference (palmitoylation-dependent membrane anchoring), and additionally notes
DNAJC5G-specific proteomic detection in human sperm with a ring-shaped headpiece
antibody-staining pattern, consistent with association with a membrane-bounded
germ-cell compartment.
action: ACCEPT
reason: Consistent with the predicted palmitoylated cysteine-string membrane anchor
shared across the CSP family; membrane is the best-supported compartment. The
gene-specific sperm staining (ring-shaped headpiece) is consistent with, though
does not pinpoint, a membrane-associated localization.
supported_by:
- reference_id: file:human/DNAJC5G/DNAJC5G-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Membrane'
- reference_id: file:human/DNAJC5G/DNAJC5G-deep-research-falcon.md
supporting_text: ring-shaped in the headpiece
references:
- id: GO_REF:0000044
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings: []
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
- id: file:human/DNAJC5G/DNAJC5G-uniprot.txt
title: UniProt entry Q8N7S2 (DNJ5G_HUMAN), cysteine string protein-gamma
findings:
- statement: Testis-specific CSP paralog with a J domain (aa 17-98) and a cysteine-string
region; annotated as a membrane lipid-anchor and palmitoylated by similarity;
no direct functional characterization (evidence at transcript level).
reference_section_type: OTHER
- id: file:human/DNAJC5G/DNAJC5G-deep-research-falcon.md
title: Falcon deep research report for DNAJC5G
findings:
- statement: 'Safe, paralog-shared / family-level inferences usable for DNAJC5G:
presence of a J domain implies an HSP70 co-chaperone (regulatory, non-catalytic)
role; the cysteine-string region is expected to undergo S-palmitoylation and
mediate membrane anchoring. Gene-specific experimental observations: DNAJC5G
protein detected in human sperm by targeted MS/antibody methods, with testis-enriched
expression and a ring-shaped headpiece staining pattern.'
reference_section_type: OTHER
reference_review:
relevance: MEDIUM
correctness: UNVERIFIED
review_notes: 'LLM deep-research synthesis (no contexts retrieved per its own header;
"this answer is not grounded in evidence but is instead a direct response from
the agent model"), so all claims are UNVERIFIED pending primary-source checking.
SAFE to use for DNAJC5G: J-domain HSP70 co-chaperone family inference and palmitoylated
cysteine-string membrane anchoring (both family-level), plus the gene-specific
testis/sperm detection and ring-shaped headpiece staining (attributed to Carapito
et al. 2017 / Duek et al. 2016 proteomics, not yet independently verified here).
MUST NOT be propagated to DNAJC5G: the report itself flags that CSP-alpha/DNAJC5-specific
functions (synaptic vesicle co-chaperone, SNARE/SNAP-25 client handling, neuroprotection,
ANCL disease) "should not be overextended to DNAJC5G" - these remain CSP-alpha-specific
and are not evidenced for CSP-gamma.'
core_functions:
- description: Predicted HSP70 (DnaJ/HSP40) co-chaperone, defined by an N-terminal
J domain that in characterized cysteine string proteins engages and stimulates
HSC70/HSP70. No experimental characterization of CSP-gamma's activity or clients
exists, so this is a family-level molecular assignment rather than a verified
function.
molecular_function:
id: GO:0051082
label: unfolded protein binding
locations:
- id: GO:0016020
label: membrane
supported_by:
- reference_id: file:human/DNAJC5G/DNAJC5G-uniprot.txt
supporting_text: Cysteine string protein-gamma
proposed_new_terms: []
suggested_questions:
- question: Does CSP-gamma function as an HSC70/HSP70 co-chaperone (J-domain-dependent
ATPase stimulation), and what is its testis-specific physiological role?
- question: Is CSP-gamma palmitoylated and membrane-anchored in vivo as predicted,
and to which membrane compartment is it targeted in germ cells?
suggested_experiments:
- description: In vitro HSC70 ATPase assays with purified CSP-gamma (wild-type and
J-domain HPD-motif mutant) to test for co-chaperone activity.
- description: Tagged-CSP-gamma expression and affinity purification-mass spectrometry
from a testis-derived line to determine subcellular localization and identify
interaction partners/clients.