{"gene":"DNAJB2","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":2005,"finding":"HSJ1 (DNAJB2) isoforms function as neuronal shuttling factors for ubiquitylated proteins, combining a J-domain that stimulates substrate loading onto Hsc70 with ubiquitin interaction motifs (UIMs) that bind ubiquitylated chaperone clients. HSJ1 prevents client aggregation, shields clients against chain trimming by ubiquitin hydrolases, and stimulates their sorting to the proteasome, participating in ERAD.","method":"Functional biochemical assays, co-immunoprecipitation, cellular proteotoxicity models","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro functional assays, cellular aggregation models), replicated by subsequent studies","pmids":["15936278"],"is_preprint":false},{"year":1996,"finding":"HSJ1a and HSJ1b proteins inhibit hsc70-catalysed clathrin uncoating by over 40% in vitro. This inhibition correlates with an increase in hsc70 associated with the coated vesicle fraction, suggesting a non-productive stabilization of hsc70 with a coated vesicle component, and is not due to ADP binding by hsc70 or hsc70 aggregation.","method":"Quantitative two-site ELISA for clathrin triskelions, in vitro uncoating assay, coated vesicle fractionation","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution assay with mechanistic dissection (ruling out ADP binding and aggregation as causes), single lab but multiple orthogonal approaches","pmids":["8870655"],"is_preprint":false},{"year":2017,"finding":"Protein kinase CK2 phosphorylates HSJ1 (DNAJB2) within its second UIM domain at the dominant site Ser250 and hierarchical site Ser247. Phosphorylation at these sites reduces HSJ1's ability to bind ubiquitylated clients and exert chaperone activity, as shown by phospho-site mutation and CK2-specific inhibitor treatment.","method":"Phospho-site mutagenesis, phospho-specific antibody, CK2 inhibitor treatment, ubiquitin-binding assays, in vitro kinase assay","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with mutagenesis and inhibitor validation, phospho-specific antibody confirmation of endogenous phosphorylation, multiple orthogonal methods in single lab","pmids":["28031292"],"is_preprint":false},{"year":2021,"finding":"HSJ1 (DNAJB2) is an essential factor orchestrating the proteostasis balance of ataxin-3. Polyglutamine-expanded proteins (ataxin-7 and huntingtin fragments) sequester HSJ1 into aggregates/inclusions in a UIM domain-dependent manner, thereby impairing HSJ1 function and disrupting ataxin-3 proteostasis.","method":"Cellular aggregation models, co-immunoprecipitation, UIM domain deletion mutants, immunofluorescence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and domain mutant analysis in cellular models, single lab with two orthogonal methods","pmids":["33837238"],"is_preprint":false},{"year":2012,"finding":"Loss-of-function of HSJ1 (DNAJB2) due to a homozygous splice mutation causes distal hereditary motor neuropathy. Overexpression of both HSJ1a and HSJ1b isoforms reduced inclusion formation induced by mutated SOD1-A4V in a neuronal cellular model, demonstrating a protective role against protein aggregation in motor neurons.","method":"Cellular model of motor neuron disease (SOD1-A4V overexpression), homozygosity mapping, splice mutation characterization, protein expression studies in patient fibroblasts","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined cellular loss-of-function phenotype with rescue by overexpression, single lab with multiple methods","pmids":["22522442"],"is_preprint":false},{"year":2016,"finding":"Deletion of the DnaJ domain of HSJ1b leads to loss of HSJ1b protein, increased cell death, protein aggregation, and enhanced autophagy. HSJ1b deficiency was also associated with significant reductions in tau and BDNF levels, suggesting the DnaJ domain is required for HSJ1b's role in maintaining proteostasis and preventing protein aggregation.","method":"Functional assays in cells carrying DnaJ domain deletion, protein expression analysis, cell death assays, autophagy markers","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined loss-of-function cellular phenotype with multiple readouts (aggregation, autophagy, cell death), single lab","pmids":["27449489"],"is_preprint":false},{"year":2025,"finding":"DNAJB2 overexpression inhibits ERS marker proteins and the activated TLR2/Myd88/NF-κB pathway, reducing skin inflammation and angiogenesis in a rosacea model, linking DNAJB2 to endoplasmic reticulum stress-mediated inflammatory signaling.","method":"Overexpression in LL37-induced mouse rosacea model and cell lines, western blot for ERS markers and NF-κB pathway components, cytokine assays","journal":"Inflammation","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, overexpression only with pathway marker readouts, no mechanistic reconstitution","pmids":["40035989"],"is_preprint":false},{"year":2025,"finding":"A heterozygous DNAJB2 c.823+6C>T mutation reduces baseline DNAJB2 protein levels and impairs the upregulation of DNAJB2 in response to heat shock in patient fibroblasts. Cystamine treatment (150 μM, 48 h) increased DNAJB2 levels in both control and patient fibroblasts.","method":"Heat shock assay in patient-derived fibroblasts, western blot for DNAJB2 expression, cystamine pharmacological treatment","journal":"Neurology international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single patient-derived cell line, single method (western blot), no mechanistic pathway dissection","pmids":["40423229"],"is_preprint":false},{"year":2025,"finding":"DNAJB2 (along with DNAJB6 and DNAJB8) prevents FG-rich nucleoporins (FG-Nups) from undergoing aberrant phase transitions, suggesting a role in nuclear pore complex quality control.","method":"Phase transition assays, co-expression experiments in cellular models","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, DNAJB2 mentioned as functionally similar to DNAJB6 but the paper focuses on DNAJB6; limited direct mechanistic data for DNAJB2 specifically","pmids":[],"is_preprint":true}],"current_model":"DNAJB2 (HSJ1) is a neuronal co-chaperone that uses its J-domain to stimulate substrate loading onto Hsc70 and its UIM domains to bind and shield ubiquitylated client proteins, directing them to the proteasome for degradation while preventing their aggregation; its chaperone activity is negatively regulated by CK2-mediated phosphorylation of UIM2 at Ser247/Ser250, and loss-of-function mutations cause inherited motor and sensory neuropathies through failure of proteostasis maintenance."},"narrative":{"mechanistic_narrative":"DNAJB2 (HSJ1) is a neuronal Hsp40-family co-chaperone that maintains proteostasis by coupling Hsc70-dependent chaperone activity to the ubiquitin-proteasome system [PMID:15936278]. It combines a J-domain that stimulates substrate loading onto Hsc70 with ubiquitin interaction motifs (UIMs) that bind ubiquitylated chaperone clients; through these activities HSJ1 prevents client aggregation, shields clients from deubiquitylation, and sorts them to the proteasome, including during ERAD [PMID:15936278]. This chaperone function is negatively regulated by CK2-mediated phosphorylation of UIM2 at the dominant Ser250 and hierarchical Ser247 sites, which reduces ubiquitin-client binding [PMID:28031292]. The J-domain is required for HSJ1b stability and its anti-aggregation function, as its deletion causes protein aggregation, increased cell death, and altered tau and BDNF levels [PMID:27449489]. HSJ1 acts as an essential balancing factor in polyglutamine proteostasis: expanded ataxin-7 and huntingtin fragments sequester it into inclusions in a UIM-dependent manner, disrupting ataxin-3 homeostasis [PMID:33837238]. Loss-of-function mutations in DNAJB2 cause distal hereditary motor neuropathy, and HSJ1 overexpression protects motor neurons against mutant SOD1-A4V aggregation [PMID:22522442].","teleology":[{"year":1996,"claim":"Established an early biochemical readout of HSJ1's interaction with the Hsc70 chaperone machinery by showing it modulates Hsc70-catalysed clathrin uncoating.","evidence":"in vitro clathrin uncoating assay and coated-vesicle fractionation with quantitative ELISA","pmids":["8870655"],"confidence":"High","gaps":["Did not define the physiological substrate range","Relationship between uncoating inhibition and later-defined ubiquitin shuttling role unresolved"]},{"year":2005,"claim":"Defined the core mechanism: HSJ1 bridges Hsc70 chaperone activity to the ubiquitin-proteasome system via a J-domain plus UIMs, acting as a shuttling factor for ubiquitylated clients.","evidence":"functional biochemical assays, co-IP, and cellular proteotoxicity models","pmids":["15936278"],"confidence":"High","gaps":["Specific client spectrum in neurons not fully enumerated","Regulation of the activity not addressed"]},{"year":2012,"claim":"Connected DNAJB2 to human disease, showing loss-of-function causes distal hereditary motor neuropathy and that HSJ1 protects against motor-neuron protein aggregation.","evidence":"homozygosity mapping, splice mutation characterization, and SOD1-A4V neuronal aggregation rescue","pmids":["22522442"],"confidence":"Medium","gaps":["Mechanism linking proteostasis failure to selective motor neuron loss unresolved","Cellular model rather than in vivo confirmation"]},{"year":2016,"claim":"Demonstrated the J-domain is required for HSJ1b protein stability and anti-aggregation function, linking domain loss to autophagy and reduced tau/BDNF.","evidence":"J-domain deletion cellular assays with aggregation, cell-death, and autophagy readouts","pmids":["27449489"],"confidence":"Medium","gaps":["Direct mechanism by which J-domain loss destabilizes the protein not defined","Tau and BDNF reductions correlative"]},{"year":2017,"claim":"Identified a regulatory switch: CK2 phosphorylation of UIM2 at Ser250/Ser247 suppresses ubiquitin-client binding and chaperone activity.","evidence":"in vitro kinase assay, phospho-site mutagenesis, phospho-specific antibody, and CK2 inhibitor treatment","pmids":["28031292"],"confidence":"High","gaps":["Physiological signals controlling CK2 activity toward HSJ1 unknown","In vivo consequence of phospho-regulation not tested"]},{"year":2021,"claim":"Showed HSJ1 is a limiting factor in polyglutamine proteostasis, being sequestered into inclusions by expanded ataxin-7 and huntingtin in a UIM-dependent manner.","evidence":"cellular aggregation models, reciprocal co-IP, and UIM deletion mutants","pmids":["33837238"],"confidence":"Medium","gaps":["Quantitative threshold of sequestration for dysfunction undefined","Single-lab cellular evidence"]},{"year":2025,"claim":"Extended putative DNAJB2 roles beyond classical proteostasis into ER-stress inflammatory signaling and patient cell expression regulation, and toward nuclear pore quality control.","evidence":"rosacea overexpression model with NF-κB markers; patient fibroblast heat-shock/cystamine western blots; FG-Nup phase transition assays (preprint)","pmids":["40035989","40423229"],"confidence":"Low","gaps":["Overexpression-only with marker readouts, no mechanistic reconstitution","Single patient-derived cell line for expression studies","FG-Nup role based on preprint focused on DNAJB6"]},{"year":null,"claim":"How CK2 phospho-regulation, client selection, and the J-domain/UIM functional cycle are coordinated in vivo to protect specific neuronal populations remains open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No in vivo model linking phospho-regulation to neuropathy","Full neuronal client repertoire unmapped","Structural basis of UIM-ubiquitin and J-Hsc70 coupling not resolved in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0]}],"complexes":[],"partners":["HSPA8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P25686","full_name":"DnaJ homolog subfamily B member 2","aliases":["Heat shock 40 kDa protein 3","Heat shock protein J1","HSJ-1"],"length_aa":324,"mass_kda":35.6,"function":"Functions as a co-chaperone, regulating the substrate binding and activating the ATPase activity of chaperones of the HSP70/heat shock protein 70 family (PubMed:22219199, PubMed:7957263). In parallel, also contributes to the ubiquitin-dependent proteasomal degradation of misfolded proteins (PubMed:15936278, PubMed:21625540). Thereby, may regulate the aggregation and promote the functional recovery of misfolded proteins like HTT, MC4R, PRKN, RHO and SOD1 and be crucial for many biological processes (PubMed:12754272, PubMed:20889486, PubMed:21719532, PubMed:22396390, PubMed:24023695). Isoform 1 which is localized to the endoplasmic reticulum membranes may specifically function in ER-associated protein degradation of misfolded proteins (PubMed:15936278)","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/P25686/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DNAJB2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000135924","cell_line_id":"CID000017","localizations":[{"compartment":"big_aggregates","grade":3},{"compartment":"cytoplasmic","grade":2},{"compartment":"nucleoplasm","grade":1}],"interactors":[],"url":"https://opencell.sf.czbiohub.org/target/CID000017","total_profiled":1310},"omim":[{"mim_id":"614881","title":"NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL RECESSIVE 5; HMNR5","url":"https://www.omim.org/entry/614881"},{"mim_id":"604320","title":"NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL RECESSIVE 1; HMNR1","url":"https://www.omim.org/entry/604320"},{"mim_id":"604139","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY B, MEMBER 2; DNAJB2","url":"https://www.omim.org/entry/604139"},{"mim_id":"143100","title":"HUNTINGTON DISEASE; HD","url":"https://www.omim.org/entry/143100"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nuclear membrane","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":284.8}],"url":"https://www.proteinatlas.org/search/DNAJB2"},"hgnc":{"alias_symbol":["HSPF3","CMT2T"],"prev_symbol":["HSJ1"]},"alphafold":{"accession":"P25686","domains":[{"cath_id":"1.10.287.110","chopping":"3-74_96-119","consensus_level":"high","plddt":83.2963,"start":3,"end":119},{"cath_id":"-","chopping":"164-222","consensus_level":"high","plddt":90.0607,"start":164,"end":222}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P25686","model_url":"https://alphafold.ebi.ac.uk/files/AF-P25686-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P25686-F1-predicted_aligned_error_v6.png","plddt_mean":67.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DNAJB2","jax_strain_url":"https://www.jax.org/strain/search?query=DNAJB2"},"sequence":{"accession":"P25686","fasta_url":"https://rest.uniprot.org/uniprotkb/P25686.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P25686/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P25686"}},"corpus_meta":[{"pmid":"15936278","id":"PMC_15936278","title":"HSJ1 is a neuronal shuttling factor for the sorting of chaperone clients to the proteasome.","date":"2005","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/15936278","citation_count":109,"is_preprint":false},{"pmid":"22522442","id":"PMC_22522442","title":"A rare recessive distal hereditary motor neuropathy with HSJ1 chaperone mutation.","date":"2012","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/22522442","citation_count":64,"is_preprint":false},{"pmid":"25274842","id":"PMC_25274842","title":"HSJ1-related hereditary neuropathies: novel mutations and extended clinical spectrum.","date":"2014","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/25274842","citation_count":45,"is_preprint":false},{"pmid":"27449489","id":"PMC_27449489","title":"Identification of a Large DNAJB2 Deletion in a Family with Spinal Muscular Atrophy and Parkinsonism.","date":"2016","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/27449489","citation_count":43,"is_preprint":false},{"pmid":"8870655","id":"PMC_8870655","title":"Inhibition of hsc70-catalysed clathrin uncoating by HSJ1 proteins.","date":"1996","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/8870655","citation_count":32,"is_preprint":false},{"pmid":"20395441","id":"PMC_20395441","title":"DNAJB2 expression in normal and diseased human and mouse skeletal muscle.","date":"2010","source":"The American journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/20395441","citation_count":24,"is_preprint":false},{"pmid":"35286755","id":"PMC_35286755","title":"DNAJB2-related Charcot-Marie-Tooth disease type 2: Pathomechanism insights and phenotypic spectrum widening.","date":"2022","source":"European journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/35286755","citation_count":16,"is_preprint":false},{"pmid":"33837238","id":"PMC_33837238","title":"PolyQ-expanded proteins impair cellular proteostasis of ataxin-3 through sequestering the co-chaperone HSJ1 into aggregates.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33837238","citation_count":13,"is_preprint":false},{"pmid":"28031292","id":"PMC_28031292","title":"Protein kinase CK2 modulates HSJ1 function through phosphorylation of the UIM2 domain.","date":"2017","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28031292","citation_count":11,"is_preprint":false},{"pmid":"35652544","id":"PMC_35652544","title":"DNAJB2 c.184C>T mutation associated with distal hereditary motor neuropathy with rimmed vacuolar myopathy.","date":"2022","source":"Clinical neuropathology","url":"https://pubmed.ncbi.nlm.nih.gov/35652544","citation_count":10,"is_preprint":false},{"pmid":"40035989","id":"PMC_40035989","title":"DNAJB2 Attenuates Rosacea Skin Inflammation and Angiogenesis by Inhibiting the Endoplasmic Reticulum Stress-mediated TLR2/Myd88/NF-κB pathway.","date":"2025","source":"Inflammation","url":"https://pubmed.ncbi.nlm.nih.gov/40035989","citation_count":2,"is_preprint":false},{"pmid":"39251209","id":"PMC_39251209","title":"Clinical and genetic features of CMT2T in Italian patients confirm the importance of MME pathogenic variants in idiopathic, late-onset axonal neuropathies.","date":"2024","source":"Journal of the peripheral nervous system : JPNS","url":"https://pubmed.ncbi.nlm.nih.gov/39251209","citation_count":1,"is_preprint":false},{"pmid":"41549766","id":"PMC_41549766","title":"Broadening the Clinical Spectrum of Axonal Hereditary Neuropathies: A Comparative Case Study on DNAJB2- and HINT1-Related Disease.","date":"2026","source":"Journal of the peripheral nervous system : JPNS","url":"https://pubmed.ncbi.nlm.nih.gov/41549766","citation_count":1,"is_preprint":false},{"pmid":"40423229","id":"PMC_40423229","title":"Impaired DNAJB2 Response to Heat Shock in Fibroblasts from a Neuropathy Patient with DNAJB2/HSJ1 Mutation: Cystamine as a Potential Therapeutic Intervention.","date":"2025","source":"Neurology international","url":"https://pubmed.ncbi.nlm.nih.gov/40423229","citation_count":0,"is_preprint":false},{"pmid":"41799927","id":"PMC_41799927","title":"Co-Existing Charcot-Marie-Tooth Disease Type II and Parkinson's Disease Linked to a Novel DNAjB2 Pathogenic Variant.","date":"2026","source":"Journal of central nervous system disease","url":"https://pubmed.ncbi.nlm.nih.gov/41799927","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.20.683411","title":"Conserved intrinsically disordered region of DNAJB6 dictates its surveillance of FG-Nup condensates","date":"2025-10-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.20.683411","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.30.615881","title":"Quorum sensing and DNA methylation play active roles in clinical  <i>Burkholderia</i>  phase variation","date":"2024-10-01","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.30.615881","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10824,"output_tokens":2238,"usd":0.033021,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9329,"output_tokens":2459,"usd":0.05406,"stage2_stop_reason":"end_turn"},"total_usd":0.087081,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"HSJ1 (DNAJB2) isoforms function as neuronal shuttling factors for ubiquitylated proteins, combining a J-domain that stimulates substrate loading onto Hsc70 with ubiquitin interaction motifs (UIMs) that bind ubiquitylated chaperone clients. HSJ1 prevents client aggregation, shields clients against chain trimming by ubiquitin hydrolases, and stimulates their sorting to the proteasome, participating in ERAD.\",\n      \"method\": \"Functional biochemical assays, co-immunoprecipitation, cellular proteotoxicity models\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro functional assays, cellular aggregation models), replicated by subsequent studies\",\n      \"pmids\": [\"15936278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"HSJ1a and HSJ1b proteins inhibit hsc70-catalysed clathrin uncoating by over 40% in vitro. This inhibition correlates with an increase in hsc70 associated with the coated vesicle fraction, suggesting a non-productive stabilization of hsc70 with a coated vesicle component, and is not due to ADP binding by hsc70 or hsc70 aggregation.\",\n      \"method\": \"Quantitative two-site ELISA for clathrin triskelions, in vitro uncoating assay, coated vesicle fractionation\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution assay with mechanistic dissection (ruling out ADP binding and aggregation as causes), single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"8870655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Protein kinase CK2 phosphorylates HSJ1 (DNAJB2) within its second UIM domain at the dominant site Ser250 and hierarchical site Ser247. Phosphorylation at these sites reduces HSJ1's ability to bind ubiquitylated clients and exert chaperone activity, as shown by phospho-site mutation and CK2-specific inhibitor treatment.\",\n      \"method\": \"Phospho-site mutagenesis, phospho-specific antibody, CK2 inhibitor treatment, ubiquitin-binding assays, in vitro kinase assay\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with mutagenesis and inhibitor validation, phospho-specific antibody confirmation of endogenous phosphorylation, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"28031292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HSJ1 (DNAJB2) is an essential factor orchestrating the proteostasis balance of ataxin-3. Polyglutamine-expanded proteins (ataxin-7 and huntingtin fragments) sequester HSJ1 into aggregates/inclusions in a UIM domain-dependent manner, thereby impairing HSJ1 function and disrupting ataxin-3 proteostasis.\",\n      \"method\": \"Cellular aggregation models, co-immunoprecipitation, UIM domain deletion mutants, immunofluorescence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and domain mutant analysis in cellular models, single lab with two orthogonal methods\",\n      \"pmids\": [\"33837238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Loss-of-function of HSJ1 (DNAJB2) due to a homozygous splice mutation causes distal hereditary motor neuropathy. Overexpression of both HSJ1a and HSJ1b isoforms reduced inclusion formation induced by mutated SOD1-A4V in a neuronal cellular model, demonstrating a protective role against protein aggregation in motor neurons.\",\n      \"method\": \"Cellular model of motor neuron disease (SOD1-A4V overexpression), homozygosity mapping, splice mutation characterization, protein expression studies in patient fibroblasts\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined cellular loss-of-function phenotype with rescue by overexpression, single lab with multiple methods\",\n      \"pmids\": [\"22522442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deletion of the DnaJ domain of HSJ1b leads to loss of HSJ1b protein, increased cell death, protein aggregation, and enhanced autophagy. HSJ1b deficiency was also associated with significant reductions in tau and BDNF levels, suggesting the DnaJ domain is required for HSJ1b's role in maintaining proteostasis and preventing protein aggregation.\",\n      \"method\": \"Functional assays in cells carrying DnaJ domain deletion, protein expression analysis, cell death assays, autophagy markers\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined loss-of-function cellular phenotype with multiple readouts (aggregation, autophagy, cell death), single lab\",\n      \"pmids\": [\"27449489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DNAJB2 overexpression inhibits ERS marker proteins and the activated TLR2/Myd88/NF-κB pathway, reducing skin inflammation and angiogenesis in a rosacea model, linking DNAJB2 to endoplasmic reticulum stress-mediated inflammatory signaling.\",\n      \"method\": \"Overexpression in LL37-induced mouse rosacea model and cell lines, western blot for ERS markers and NF-κB pathway components, cytokine assays\",\n      \"journal\": \"Inflammation\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, overexpression only with pathway marker readouts, no mechanistic reconstitution\",\n      \"pmids\": [\"40035989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A heterozygous DNAJB2 c.823+6C>T mutation reduces baseline DNAJB2 protein levels and impairs the upregulation of DNAJB2 in response to heat shock in patient fibroblasts. Cystamine treatment (150 μM, 48 h) increased DNAJB2 levels in both control and patient fibroblasts.\",\n      \"method\": \"Heat shock assay in patient-derived fibroblasts, western blot for DNAJB2 expression, cystamine pharmacological treatment\",\n      \"journal\": \"Neurology international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single patient-derived cell line, single method (western blot), no mechanistic pathway dissection\",\n      \"pmids\": [\"40423229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DNAJB2 (along with DNAJB6 and DNAJB8) prevents FG-rich nucleoporins (FG-Nups) from undergoing aberrant phase transitions, suggesting a role in nuclear pore complex quality control.\",\n      \"method\": \"Phase transition assays, co-expression experiments in cellular models\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, DNAJB2 mentioned as functionally similar to DNAJB6 but the paper focuses on DNAJB6; limited direct mechanistic data for DNAJB2 specifically\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"DNAJB2 (HSJ1) is a neuronal co-chaperone that uses its J-domain to stimulate substrate loading onto Hsc70 and its UIM domains to bind and shield ubiquitylated client proteins, directing them to the proteasome for degradation while preventing their aggregation; its chaperone activity is negatively regulated by CK2-mediated phosphorylation of UIM2 at Ser247/Ser250, and loss-of-function mutations cause inherited motor and sensory neuropathies through failure of proteostasis maintenance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DNAJB2 (HSJ1) is a neuronal Hsp40-family co-chaperone that maintains proteostasis by coupling Hsc70-dependent chaperone activity to the ubiquitin-proteasome system [#0]. It combines a J-domain that stimulates substrate loading onto Hsc70 with ubiquitin interaction motifs (UIMs) that bind ubiquitylated chaperone clients; through these activities HSJ1 prevents client aggregation, shields clients from deubiquitylation, and sorts them to the proteasome, including during ERAD [#0]. This chaperone function is negatively regulated by CK2-mediated phosphorylation of UIM2 at the dominant Ser250 and hierarchical Ser247 sites, which reduces ubiquitin-client binding [#2]. The J-domain is required for HSJ1b stability and its anti-aggregation function, as its deletion causes protein aggregation, increased cell death, and altered tau and BDNF levels [#5]. HSJ1 acts as an essential balancing factor in polyglutamine proteostasis: expanded ataxin-7 and huntingtin fragments sequester it into inclusions in a UIM-dependent manner, disrupting ataxin-3 homeostasis [#3]. Loss-of-function mutations in DNAJB2 cause distal hereditary motor neuropathy, and HSJ1 overexpression protects motor neurons against mutant SOD1-A4V aggregation [#4].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established an early biochemical readout of HSJ1's interaction with the Hsc70 chaperone machinery by showing it modulates Hsc70-catalysed clathrin uncoating.\",\n      \"evidence\": \"in vitro clathrin uncoating assay and coated-vesicle fractionation with quantitative ELISA\",\n      \"pmids\": [\"8870655\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the physiological substrate range\", \"Relationship between uncoating inhibition and later-defined ubiquitin shuttling role unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the core mechanism: HSJ1 bridges Hsc70 chaperone activity to the ubiquitin-proteasome system via a J-domain plus UIMs, acting as a shuttling factor for ubiquitylated clients.\",\n      \"evidence\": \"functional biochemical assays, co-IP, and cellular proteotoxicity models\",\n      \"pmids\": [\"15936278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific client spectrum in neurons not fully enumerated\", \"Regulation of the activity not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected DNAJB2 to human disease, showing loss-of-function causes distal hereditary motor neuropathy and that HSJ1 protects against motor-neuron protein aggregation.\",\n      \"evidence\": \"homozygosity mapping, splice mutation characterization, and SOD1-A4V neuronal aggregation rescue\",\n      \"pmids\": [\"22522442\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking proteostasis failure to selective motor neuron loss unresolved\", \"Cellular model rather than in vivo confirmation\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated the J-domain is required for HSJ1b protein stability and anti-aggregation function, linking domain loss to autophagy and reduced tau/BDNF.\",\n      \"evidence\": \"J-domain deletion cellular assays with aggregation, cell-death, and autophagy readouts\",\n      \"pmids\": [\"27449489\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism by which J-domain loss destabilizes the protein not defined\", \"Tau and BDNF reductions correlative\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified a regulatory switch: CK2 phosphorylation of UIM2 at Ser250/Ser247 suppresses ubiquitin-client binding and chaperone activity.\",\n      \"evidence\": \"in vitro kinase assay, phospho-site mutagenesis, phospho-specific antibody, and CK2 inhibitor treatment\",\n      \"pmids\": [\"28031292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signals controlling CK2 activity toward HSJ1 unknown\", \"In vivo consequence of phospho-regulation not tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed HSJ1 is a limiting factor in polyglutamine proteostasis, being sequestered into inclusions by expanded ataxin-7 and huntingtin in a UIM-dependent manner.\",\n      \"evidence\": \"cellular aggregation models, reciprocal co-IP, and UIM deletion mutants\",\n      \"pmids\": [\"33837238\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative threshold of sequestration for dysfunction undefined\", \"Single-lab cellular evidence\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended putative DNAJB2 roles beyond classical proteostasis into ER-stress inflammatory signaling and patient cell expression regulation, and toward nuclear pore quality control.\",\n      \"evidence\": \"rosacea overexpression model with NF-\\u03baB markers; patient fibroblast heat-shock/cystamine western blots; FG-Nup phase transition assays (preprint)\",\n      \"pmids\": [\"40035989\", \"40423229\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Overexpression-only with marker readouts, no mechanistic reconstitution\", \"Single patient-derived cell line for expression studies\", \"FG-Nup role based on preprint focused on DNAJB6\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CK2 phospho-regulation, client selection, and the J-domain/UIM functional cycle are coordinated in vivo to protect specific neuronal populations remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo model linking phospho-regulation to neuropathy\", \"Full neuronal client repertoire unmapped\", \"Structural basis of UIM-ubiquitin and J-Hsc70 coupling not resolved in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HSPA8\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}