DNAJC3 (p58IPK, also ERdj6/PRKRI) is an ER-resident J-domain co-chaperone with an N-terminal TPR-repeat region (nine TPR motifs) and a C-terminal J domain. It has two interlinked roles. As a co-chaperone it binds the HSP70 chaperones BiP (HSPA5) and HSC70 (HSPA8) via its J domain, stimulates their ATPase activity, and binds misfolded proteins through its TPR groove, functioning in ER protein folding and the unfolded protein response. As a stress-inducible inhibitor of the eIF2-alpha protein kinases, it binds and inhibits PKR (EIF2AK2), PERK (EIF2AK3) and GCN2 (EIF2AK4), preventing eIF2-alpha (Ser-51/52) phosphorylation and thereby restoring/attenuating protein synthesis during ER, viral, hypothermic and amino-acid-starvation stress. It is broadly expressed (high in pancreas and testis), induced via ATF6 during ER stress, and its loss causes an autosomal-recessive syndrome of juvenile-onset diabetes mellitus with multisystem neurodegeneration (ACPHD).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0051087 protein-folding chaperone binding | IBA GO_REF:0000033 | ACCEPT | Summary: DNAJC3 binds the HSP70 chaperones BiP (HSPA5) and HSC70 (HSPA8) via its J domain, a defining co-chaperone molecular function. Supported by experiment and phylogeny. Reason: Binding of the HSP70 chaperones BiP/HSC70 through the J domain is a core molecular function of DNAJC3, supported by direct interaction data. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt The J domain mediates interaction with HSPA8 |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: DNAJC3/ERdj6 is an ER-resident J-protein; the ER is its principal site of action, supported by phylogeny and experiment. Reason: ER residence is well documented for DNAJC3 and is the compartment where it acts as a BiP co-chaperone in the UPR. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0034975 protein folding in endoplasmic reticulum | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: As an ER co-chaperone of BiP, DNAJC3 participates in ER protein folding. Supported by phylogeny and its documented chaperone role. Reason: ER protein folding is a genuine process outcome of DNAJC3's BiP co-chaperone activity, but downstream of its direct molecular roles (chaperone binding, kinase inhibition). Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Involved in the unfolded protein response (UPR) |
| GO:0051787 misfolded protein binding | IBA GO_REF:0000033 | ACCEPT | Summary: DNAJC3 binds misfolded proteins via a hydrophobic groove in its first two TPR repeats, a core substrate-recognition molecular function. Reason: Misfolded-protein binding through the TPR groove is a documented molecular function of DNAJC3, supporting its co-chaperone substrate-delivery role. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Binding to misfolded proteins is mediated by a hydrophobic patch |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000120 | ACCEPT | Summary: Automated ER localization, consistent with the established ER residence of DNAJC3. Reason: Correct compartment; agrees with ISS/IBA/TAS ER evidence. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0004860 protein kinase inhibitor activity | IEA GO_REF:0000107 | ACCEPT | Summary: DNAJC3/p58IPK inhibits the eIF2-alpha protein kinases (PKR/EIF2AK2, PERK/EIF2AK3, GCN2/EIF2AK4). This is a core molecular function, also supported experimentally (PubMed:8576172) and by ISS. Reason: Inhibition of eIF2-alpha kinase autophosphorylation/activity is a defining, experimentally established molecular function of DNAJC3. Supporting Evidence: PMID:8576172 protein inhibits both the autophosphorylation of PKR and the phosphorylation of |
| GO:0005737 cytoplasm | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Ortholog-projected cytoplasmic localization. DNAJC3 inhibits the cytosolic kinase PKR and is reported in the cytoplasm in the original p58IPK literature, though its primary residence is the ER. Reason: A cytoplasmic pool is consistent with DNAJC3's documented inhibition of cytosolic PKR, but the ER is its primary compartment; retained as non-core. Fractionation and immunofluorescence placed p58 predominantly in the cytoplasm. Supporting Evidence: PMID:8666242 revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein |
| GO:0005788 endoplasmic reticulum lumen | IEA GO_REF:0000107 | ACCEPT | Summary: Ortholog-projected ER-lumen localization, consistent with DNAJC3's signal-peptide-driven ER residence. Reason: ER lumen is a precise, correct localization for this ER-resident J-protein. Consistent with UniProt's ER location and the sibling ER-lumen rows. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0005829 cytosol | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Ortholog-projected cytosolic localization, consistent with the documented cytosolic pool engaging PKR. Secondary to ER residence. Reason: Cytosolic localization reflects DNAJC3's PKR-inhibition role but is secondary to its primary ER residence. Fractionation placed p58 predominantly in the cytoplasm alongside its cytosolic target PKR. Supporting Evidence: PMID:8666242 revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein |
| GO:0019901 protein kinase binding | IEA GO_REF:0000107 | ACCEPT | Summary: DNAJC3 binds the eIF2-alpha protein kinases (PKR, PERK, GCN2). A core molecular function underlying its kinase-inhibitor activity; supported experimentally (PubMed:8576172) and by ISS. Reason: Binding to PKR/PERK/GCN2 is experimentally documented and is the basis of DNAJC3's eIF2-alpha kinase inhibition. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Interacts with EIF2AK2 |
| GO:0030968 endoplasmic reticulum unfolded protein response | IEA GO_REF:0000107 | ACCEPT | Summary: DNAJC3 is an ER-stress-inducible component of the UPR that modulates eIF2-alpha signaling. Well supported. Reason: DNAJC3's induction during ER stress and regulation of eIF2-alpha kinases place it squarely in the ER UPR. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Involved in the unfolded protein response (UPR) |
| GO:0034976 response to endoplasmic reticulum stress | IEA GO_REF:0000107 | ACCEPT | Summary: DNAJC3 is up-regulated during ER stress (via ATF6) and functions in the ER stress response. Reason: ER-stress induction and function are documented; a correct process annotation. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Up-regulated during an endoplasmic reticulum stress via |
| GO:0036494 positive regulation of translation initiation in response to endoplasmic reticulum stress | IEA GO_REF:0000107 | ACCEPT | Summary: By inhibiting eIF2-alpha kinases and preventing eIF2-alpha phosphorylation, DNAJC3 restores cap-dependent translation initiation during late ER stress. Consistent with its negative regulation of eIF2-alpha kinases. Reason: Preventing eIF2-alpha phosphorylation relieves translational repression, so promotion of translation initiation in late ER stress is a supported process role. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt attenuating general protein synthesis |
| GO:0051087 protein-folding chaperone binding | IEA GO_REF:0000107 | ACCEPT | Summary: Ortholog-projected chaperone-binding function, redundant with the IBA and experimental evidence that DNAJC3 binds BiP/HSC70. Reason: DNAJC3 binds the HSP70 chaperones; this is a correct, core molecular function. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt The J domain mediates interaction with HSPA8 |
| GO:0051787 misfolded protein binding | IEA GO_REF:0000107 | ACCEPT | Summary: Ortholog-projected misfolded-protein binding, redundant with the IBA misfolded-protein binding annotation and the TPR-groove substrate-binding mechanism. Reason: DNAJC3 binds misfolded proteins via its TPR groove; a correct molecular function. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Binding to misfolded proteins is mediated by a hydrophobic patch |
| GO:0070417 cellular response to cold | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: DNAJC3 inhibits GCN2 under hypothermic stress, attenuating eIF2-alpha phosphorylation; a documented (by-similarity) role in the cold response. Reason: The cold-response role is a specific stress context of DNAJC3's eIF2-alpha kinase regulation; genuine but specialized/non-core. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt hypothermic and amino acid starving stress conditions |
| GO:1902010 negative regulation of translation in response to endoplasmic reticulum stress | IMP PMID:22064321 ERp29 induces breast cancer cell growth arrest and survival ... | KEEP AS NON CORE | Summary: DNAJC3 modulates translation during ER stress through its eIF2-alpha kinase regulation. The cited study reports p58IPK upregulation downstream of ERp29-induced growth arrest, so the evidence for this specific direction is indirect, though a translation-regulatory role is mechanistically well supported. Reason: DNAJC3 regulates eIF2-alpha-dependent translation during ER stress; the specific IMP citation is correlative (p58IPK as a downstream marker), so retained as a non-core process annotation. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt attenuating general protein synthesis |
| GO:0005788 endoplasmic reticulum lumen | TAS Reactome:R-HSA-8952289 | ACCEPT | Summary: Reactome-curated ER-lumen localization, consistent with DNAJC3's ER residence. Reason: ER lumen is a precise, correct localization for this ER-resident J-protein. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-6798751 | UNDECIDED | Summary: Reactome annotation from neutrophil-degranulation curation. This reflects a secretome/granule context, not DNAJC3's core ER co-chaperone function. Reason: Curated localization from degranulation proteomics; peripheral to and not reflective of DNAJC3's principal ER role. Previously KEEP_AS_NON_CORE; set to UNDECIDED because the only cited support was the GOA row for this annotation, which records the annotation rather than evidence for it. |
| GO:0035578 azurophil granule lumen | TAS Reactome:R-HSA-6798751 | UNDECIDED | Summary: Reactome annotation from neutrophil azurophil-granule curation; a specialized context distinct from DNAJC3's ER co-chaperone role. Reason: Curated granule-lumen localization peripheral to DNAJC3's core ER function. Previously KEEP_AS_NON_CORE; set to UNDECIDED because the only cited support was the GOA row for this annotation, which records the annotation rather than evidence for it. |
| GO:0004860 protein kinase inhibitor activity | ISS GO_REF:0000024 | ACCEPT | Summary: Sequence/ortholog-based protein kinase inhibitor activity, redundant with the experimental PKR-inhibition evidence. A core molecular function. Reason: DNAJC3 inhibits the eIF2-alpha kinases; this ISS annotation is correct and core. Supporting Evidence: PMID:8576172 protein inhibits both the autophosphorylation of PKR and the phosphorylation of |
| GO:0005783 endoplasmic reticulum | ISS GO_REF:0000024 | ACCEPT | Summary: Sequence/ortholog-based ER localization, consistent with the established ER residence. Reason: Correct compartment for this ER-resident J-protein. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0005829 cytosol | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Sequence/ortholog-based cytosolic localization, consistent with the cytosolic pool that engages PKR. Secondary to ER residence. Reason: Cytosolic localization reflects the PKR-inhibition role but is secondary to DNAJC3's primary ER residence. Fractionation placed p58 predominantly in the cytoplasm alongside its cytosolic target PKR. Supporting Evidence: PMID:8666242 revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein |
| GO:0019901 protein kinase binding | ISS GO_REF:0000024 | ACCEPT | Summary: Sequence/ortholog-based protein kinase binding, redundant with the experimental PKR/PERK/GCN2 interaction evidence. Reason: DNAJC3 binds the eIF2-alpha kinases; a correct, core molecular function. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt Interacts with EIF2AK2 |
| GO:0036494 positive regulation of translation initiation in response to endoplasmic reticulum stress | ISS GO_REF:0000024 | ACCEPT | Summary: Ortholog-based; consistent with the IEA call that DNAJC3 promotes translation initiation late in ER stress by relieving eIF2-alpha phosphorylation. Reason: Supported by DNAJC3's prevention of eIF2-alpha phosphorylation, which relieves translational repression. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt attenuating general protein synthesis |
| GO:0070417 cellular response to cold | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Ortholog-based cold-response role via GCN2 inhibition under hypothermic stress. Reason: A specific stress-context role of DNAJC3's eIF2-alpha kinase regulation; genuine but specialized. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt hypothermic and amino acid starving stress conditions |
| GO:1903912 negative regulation of endoplasmic reticulum stress-induced eIF2 alpha phosphorylation | ISS GO_REF:0000024 | ACCEPT | Summary: DNAJC3 prevents phosphorylation of eIF2-alpha by inhibiting the eIF2-alpha kinases during ER stress. This is the central biological-process role of DNAJC3. Reason: Negative regulation of ER-stress-induced eIF2-alpha phosphorylation is the core process effected by DNAJC3's kinase inhibition. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt preventing the phosphorylation of eIF- |
| GO:1903561 extracellular vesicle | HDA PMID:24769233 Proteomic analysis of cerebrospinal fluid extracellular vesi... | MARK AS OVER ANNOTATED | Summary: Detected in an extracellular-vesicle proteome, but the detection does not establish that this protein is an EV constituent. Reason: ER-resident co-chaperone. Mainly resident in an intracellular compartment that MISEV2018 (PMID:30637094) lists as not enriched in small EVs of plasma-membrane/endosomal origin (category 4), and its own review keeps no experimental cell-surface or plasma-membrane pool; an exosome annotation from a bulk EV proteome is not supported. (Manual re-review for OMICS_EVIDENCE, 2026-10-10; previous action: KEEP_AS_NON_CORE.) The MISEV2018 category-4 statement backs this argument. Supporting Evidence: PMID:30637094 Proteins localized in/on intracellular compartments of eukaryotic secreting cells other than the plasma membrane and endosomes (i.e. components of the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, autophagosomes, peroxisomes) are found in some types of EVs, but a priori not enriched in the smaller EVs |
| GO:0043066 negative regulation of apoptotic process | IMP PMID:22064321 ERp29 induces breast cancer cell growth arrest and survival ... | KEEP AS NON CORE | Summary: An anti-apoptotic/survival role is annotated from a study where p58IPK is up-regulated downstream of ERp29-induced growth arrest. The evidence is correlative rather than a direct DNAJC3 perturbation, so this is weakly grounded. Reason: The apoptosis-regulation annotation rests on correlative p58IPK upregulation in the cited study, not a direct DNAJC3 loss/gain experiment; retained as non-core. The abstract does report a p58IPK RNAi experiment, though its direct readout is eIF2alpha phosphorylation, and attributes protection from ER-dependent apoptosis to p58IPK. Supporting Evidence: PMID:22064321 reduction of p58(IPK) expression by RNA interference stimulated eIF2Ξ± phosphorylation. The repression of eIF2Ξ± phosphorylation by p58(IPK) prevents ERp29-transfected cells from undergoing ER-dependent apoptosis |
| GO:0016020 membrane | HDA PMID:19946888 Defining the membrane proteome of NK cells. | MARK AS OVER ANNOTATED | Summary: Recovered in a membrane-fraction proteome without protein-specific evidence that it associates with membranes. Reason: UniProt: endoplasmic reticulum (by similarity); GOA leads place it in the ER lumen and cytosol. No membrane association on record. (Manual re-review for OMICS_EVIDENCE, 2026-10-10; previous action: KEEP_AS_NON_CORE.) The cited proteome itself notes that most non-integral hits are only transiently membrane-associated. Supporting Evidence: PMID:19946888 The remaining species were largely involved in cellular processes and molecular functions that could be predicted to be transiently associated with membranes. |
| GO:0070062 extracellular exosome | HDA PMID:19199708 Proteomic analysis of human parotid gland exosomes by multid... | MARK AS OVER ANNOTATED | Summary: Detected in an extracellular-vesicle proteome, but the detection does not establish that this protein is an EV constituent. Reason: ER-resident co-chaperone. Mainly resident in an intracellular compartment that MISEV2018 (PMID:30637094) lists as not enriched in small EVs of plasma-membrane/endosomal origin (category 4), and its own review keeps no experimental cell-surface or plasma-membrane pool; an exosome annotation from a bulk EV proteome is not supported. (Manual re-review for OMICS_EVIDENCE, 2026-10-10; previous action: KEEP_AS_NON_CORE.) The MISEV2018 category-4 statement backs this argument. Supporting Evidence: PMID:30637094 Proteins localized in/on intracellular compartments of eukaryotic secreting cells other than the plasma membrane and endosomes (i.e. components of the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, autophagosomes, peroxisomes) are found in some types of EVs, but a priori not enriched in the smaller EVs |
| GO:0005788 endoplasmic reticulum lumen | TAS Reactome:R-HSA-1791157 | ACCEPT | Summary: Reactome-curated ER-lumen localization, consistent with DNAJC3's ER residence. Reason: ER lumen is a precise, correct localization for DNAJC3. Supporting Evidence: file:human/DNAJC3/DNAJC3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum |
| GO:0005829 cytosol | TAS Reactome:R-HSA-9835454 | KEEP AS NON CORE | Summary: Reactome-curated cytosolic localization, consistent with the cytosolic pool engaging PKR. Secondary to ER residence. Reason: Cytosolic localization reflects DNAJC3's PKR-inhibition role but is secondary to its ER residence. Fractionation placed p58 predominantly in the cytoplasm alongside its cytosolic target PKR. Supporting Evidence: PMID:8666242 revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein |
| GO:0005737 cytoplasm | TAS PMID:8666242 Cloning, expression, and cellular localization of the oncoge... | KEEP AS NON CORE | Summary: The original p58IPK characterization reported cytoplasmic localization, consistent with its inhibition of the cytosolic kinase PKR. Secondary to ER residence. Reason: Cytoplasmic localization is documented in early p58IPK studies and reflects its PKR-inhibition role, but the ER is its primary compartment. The cited study's fractionation and immunofluorescence placed p58 predominantly in the cytoplasm. Supporting Evidence: PMID:8666242 revealed that p58 was found predominantly in the cytoplasm, consistent with its function as an inhibitor of PKR, which is also a predominantly cytoplasmic protein |
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Download this section (compressed HTML)Q: How does DNAJC3 partition between the ER lumen (BiP co-chaperone) and the cytosol (PKR inhibition), and is the same molecule responsible for both activities?
Q: Which activity loss (BiP co-chaperone versus eIF2-alpha kinase inhibition) drives the beta-cell failure and neurodegeneration in DNAJC3-deficient ACPHD?
Experiment: In vitro kinase assays measuring DNAJC3 inhibition of PKR, PERK and GCN2 autophosphorylation and eIF2-alpha phosphorylation, with TPR-domain and J-domain variants to map the inhibitory determinants.
Experiment: Tissue-specific (beta-cell, neuron) DNAJC3 knockout with separation-of-function alleles (chaperone-dead versus kinase-inhibition-dead) to dissect which function underlies the diabetes/neurodegeneration phenotype.
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