{"gene":"HSPA4","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2011,"finding":"HSPA4 is a member of the HSP110 family that acts as a nucleotide exchange factor (NEF) for HSP70 chaperones during the ATP hydrolysis cycle. Knockout of Hspa4 in mice leads to impaired spermatogenesis, with pachytene spermatocytes failing to complete meiotic prophase I and undergoing apoptosis, establishing a required role for HSPA4 in spermatogenesis.","method":"Hspa4 knockout mouse model; histological analysis; TUNEL assay; RT-PCR for spermatocyte-specific transcripts","journal":"Reproduction (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse with defined cellular phenotype (meiotic arrest, apoptosis) replicated across developmental time points, multiple orthogonal methods","pmids":["21487003"],"is_preprint":false},{"year":2012,"finding":"HSPA4, acting as a nucleotide exchange factor for HSP70 chaperones, is required for cardiac protein quality control. Hspa4 knockout mice develop cardiac hypertrophy and fibrosis associated with accumulation of polyubiquitinated proteins in cardiomyocytes, and with enhanced activation of gp130-STAT3, CaMKII, and calcineurin-NFAT signaling pathways.","method":"Hspa4 knockout mouse model; Western blot for polyubiquitinated proteins and hypertrophic markers; immunofluorescence; echocardiography; pressure overload model; cultured neonatal Hspa4 KO cardiomyocytes; gene expression profiling","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse with multiple orthogonal methods (protein aggregation, signaling, histology, in vitro cardiomyocyte culture), single rigorous study","pmids":["22884543"],"is_preprint":false},{"year":2014,"finding":"HSPA4 and its paralog HSPA4L functionally collaborate as cochaperones during embryonic lung maturation. Double-knockout Hspa4l−/−Hspa4−/− mice display pulmonary hypoplasia with accumulation of ubiquitinated proteins in lungs, impaired type I/II pneumocyte maturation, and neonatal lethality, while single knockouts survive, demonstrating functional redundancy between the two HSP110 family members.","method":"Hspa4l−/−Hspa4−/− double-knockout mouse model; histological analysis; immunofluorescence for surfactant proteins; Western blot for ubiquitinated proteins and Bcl-2; proliferation and apoptosis assays","journal":"American journal of respiratory cell and molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — double-KO genetic epistasis with multiple orthogonal readouts in a single rigorous study demonstrating functional complementarity","pmids":["23980576"],"is_preprint":false},{"year":2011,"finding":"NBS1 overexpression induces HSPA4 expression via upregulation of heat shock transcription factor 4b (HSF4b). siRNA-mediated knockdown of HSPA4 in NBS1-overexpressing H1299 cells decreased in vitro migration, invasion, and anchorage-independent growth, establishing a NBS1-HSF4b-HSPA4 signaling axis promoting metastatic behavior independently of MMP2.","method":"RT-PCR; Western blot; siRNA knockdown; in vitro migration/invasion assays; soft agar colony formation; gelatin zymography","journal":"Journal of biomedical science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA KD with defined phenotypic readouts and pathway placement, single lab, two orthogonal functional assays","pmids":["21208456"],"is_preprint":false},{"year":2019,"finding":"Membrane-expressed glycosylated HSPA4 is targeted by pathogenic IgG produced by tumor-educated B cells in draining lymph nodes. Anti-HSPA4 IgG activates ITGB5 (a HSPA4-binding protein) and downstream Src/NF-κB signaling in tumor cells, promoting CXCR4/SDF1α-mediated lymph node metastasis.","method":"Mouse model of spontaneous lymph node metastasis; B cell depletion; IgG isolation and treatment; co-IP/binding assays for HSPA4-ITGB5 interaction; signaling pathway analysis; serum IgG ELISA in human subjects","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assay identifying HSPA4-ITGB5 interaction, in vivo mouse model, mechanistic signaling pathway validation, multiple orthogonal methods","pmids":["30643287"],"is_preprint":false},{"year":2022,"finding":"SIRT1 physically interacts with HSPA4 and deacetylates it at lysine residues K305, K351, and K605. This deacetylation induces nuclear translocation of HSPA4 and represses proinflammatory cytokine expression in glial cells. Mutation of these lysine residues to arginine retains HSPA4 in the cytoplasm and abolishes its anti-inflammatory activity.","method":"Co-immunoprecipitation; site-directed mutagenesis of K305/351/605R; subcellular fractionation/immunofluorescence; SIRT1 transgenic mice; MPTP-induced PD model; cytokine expression analysis","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — site-directed mutagenesis of specific deacetylation sites combined with Co-IP and subcellular localization with functional consequence, supported by in vivo transgenic mouse model","pmids":["35158021"],"is_preprint":false},{"year":2002,"finding":"HSPA4 (HSP70) is involved in the radioadaptive response. High-dose radiation upregulates Hspa4 expression in mouse splenocytes. Splenocytes from Hspa4 transgenic mice showed reduced cell death after high-dose irradiation when preirradiated with a low dose, demonstrating that HSPA4 upregulation mediates the adaptive cytoprotective response to radiation.","method":"RT-PCR; Hspa4 transgenic mice; low-dose pre-irradiation followed by high-dose challenge; cell viability/death assay","journal":"Radiation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic mouse model with defined functional phenotype, single lab, two methods (expression + cell death)","pmids":["12005543"],"is_preprint":false},{"year":2024,"finding":"HSPA4 upregulation in gastric cancer stabilizes the m6A demethylase ALKBH5 protein, which in turn reduces CD58 expression via m6A methylation regulation in GC cells, leading to impaired CD8+ T cell cytotoxicity and PD1/PDL1 axis activation and thereby promoting immune evasion.","method":"Co-immunoprecipitation; meRIP (methylated RNA immunoprecipitation); co-culture cytotoxicity assay with CD8+ T cells; HSPA4 overexpression/knockdown; Western blot; multiplex fluorescent immunohistochemistry","journal":"Journal of experimental & clinical cancer research : CR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for protein interaction, meRIP for m6A regulation, functional co-culture assay, single lab, multiple orthogonal methods","pmids":["38589927"],"is_preprint":false},{"year":2024,"finding":"HSPA4 promotes clathrin-mediated endocytosis and facilitates bovine respiratory syncytial virus (BRSV) entry by activating the PI3K-Akt signaling pathway to upregulate clathrin heavy chain (CHC) expression, and by increasing the ATPase activity of HSC70, thereby enhancing clathrin-mediated endocytic efficiency.","method":"Western blot; virus titer assay; virus copy analysis; immunofluorescence assay (IFA); HSPA4 knockdown/overexpression; PI3K-Akt pathway inhibition; ATPase activity assay","journal":"Viruses","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays (ATPase activity, viral entry, signaling), single lab, orthogonal readouts but no structural or reconstitution data","pmids":["39599898"],"is_preprint":false},{"year":2025,"finding":"HSPA4 physically interacts with transferrin in the cytoplasm of dopaminergic neurons and inhibits transferrin export from the cell, thereby reducing extracellular iron uptake and attenuating ferroptosis. HSPA4 overexpression reduces ferroptosis in erastin-treated cells and MPTP-treated PD model mice, while HSPA4 knockdown exacerbates ferroptosis.","method":"Co-immunoprecipitation for HSPA4-transferrin interaction; HSPA4 overexpression/knockdown in SH-SY5Y cells and primary dopaminergic neurons; MPTP-induced mouse PD model; ferroptosis assays; behavioral testing","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifying HSPA4-transferrin interaction, gain/loss-of-function in vitro and in vivo, single lab, multiple orthogonal methods","pmids":["41068261"],"is_preprint":false},{"year":2022,"finding":"DNAJC12 (an HSP40 co-chaperone) physically interacts with HSPA4 as demonstrated by co-immunoprecipitation. Rescue experiments showed that HSPA4 overexpression restored proliferation and migration capacity suppressed by DNAJC12 silencing, placing HSPA4 downstream of DNAJC12 in rectal cancer cell biology. (Note: the original paper PMID:36185081 was subsequently retracted per PMID:37565223.)","method":"Co-immunoprecipitation; siRNA knockdown; rescue overexpression experiments; CCK-8; wound healing; xenograft","journal":"Evidence-based complementary and alternative medicine : eCAM","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single Co-IP method, and the paper was retracted (PMID:37565223); evidence should not be relied upon","pmids":["36185081","37565223"],"is_preprint":false},{"year":2024,"finding":"miR-1287-5p directly targets HSPA4 mRNA, negatively regulating HSPA4 protein levels. HSPA4 acts as a downstream functional mediator in the LINC01089/miR-1287-5p axis that inhibits osteogenic differentiation of human mesenchymal stem cells; miR-1287-5p depletion blocked LINC01089 knockdown-induced osteogenesis, and HSPA4 knockdown attenuated osteogenic differentiation.","method":"Dual-luciferase reporter assay; RNA immunoprecipitation (RIP); RT-qPCR; Western blot; ALP activity; alizarin red S staining; siRNA knockdown","journal":"Bone & joint research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dual-luciferase and RIP confirm miRNA-target interaction, functional osteogenesis assays with KD, single lab","pmids":["39679709"],"is_preprint":false},{"year":2024,"finding":"In Drosophila, the HSPA4 family ortholog Hsc70Cb is required for spermatogonia survival and sperm individualisation. Introduction of human HSPA4 cDNA into Hsc70Cb-deficient flies partially rescued germ cell survival to the spermatocyte stage, demonstrating functional conservation between Drosophila Hsc70Cb and human HSPA4 in spermatogenesis.","method":"RNAi-mediated knockdown using Nanos-Gal4; human HSPA4 cDNA rescue experiment in Drosophila; testis histology","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic rescue with human HSPA4 cDNA in Drosophila model, preprint not yet peer-reviewed, single lab","pmids":[],"is_preprint":true}],"current_model":"HSPA4 is a member of the HSP110 family that functions as a nucleotide exchange factor (NEF) for HSP70 chaperones in protein quality control; it is required for spermatogenesis (meiotic prophase I completion), cardiac proteostasis (preventing accumulation of misfolded/polyubiquitinated proteins and hypertrophic signaling), and embryonic lung maturation (redundantly with HSPA4L); it is deacetylated by SIRT1 at K305/K351/K605, promoting its nuclear translocation to repress neuroinflammation; it interacts with transferrin to restrain iron import and attenuate ferroptosis in dopaminergic neurons; at the plasma membrane it acts as a glycosylated antigen whose ligation by IgG activates ITGB5/Src/NF-κB to drive tumor metastasis; and it promotes viral clathrin-mediated endocytosis by activating PI3K-Akt/CHC and increasing HSC70 ATPase activity."},"narrative":{"mechanistic_narrative":"HSPA4 is an HSP110-family nucleotide exchange factor for HSP70 chaperones that supports protein quality control across multiple tissues, with loss-of-function phenotypes converging on accumulation of polyubiquitinated/misfolded proteins [PMID:21487003, PMID:22884543]. Genetic ablation in mice arrests pachytene spermatocytes in meiotic prophase I and triggers their apoptosis, establishing an essential role in spermatogenesis [PMID:21487003], a function conserved through the Drosophila ortholog Hsc70Cb, which human HSPA4 cDNA partially rescues. In the heart, HSPA4 loss causes accumulation of polyubiquitinated proteins and drives hypertrophy and fibrosis through gp130-STAT3, CaMKII, and calcineurin-NFAT signaling [PMID:22884543], and together with its redundant paralog HSPA4L it is required for embryonic lung maturation, with double-knockout mice showing pulmonary hypoplasia and accumulated ubiquitinated proteins [PMID:23980576]. Beyond chaperone-associated proteostasis, HSPA4 is subject to regulation and moonlighting roles: SIRT1 deacetylates it at K305/K351/K605 to drive nuclear translocation that represses proinflammatory cytokine expression in glia [PMID:35158021], and cytoplasmic HSPA4 binds transferrin to limit iron uptake and attenuate ferroptosis in dopaminergic neurons [PMID:41068261]. In cancer, membrane-displayed glycosylated HSPA4 binds ITGB5 and, when ligated by tumor-educated B-cell IgG, activates Src/NF-κB signaling to promote lymph-node metastasis [PMID:30643287], while intracellular HSPA4 stabilizes the m6A demethylase ALKBH5 to suppress CD58 and impair CD8+ T-cell cytotoxicity [PMID:38589927]. HSPA4 also promotes clathrin-mediated viral endocytosis by activating PI3K-Akt to upregulate clathrin heavy chain and by increasing HSC70 ATPase activity [PMID:39599898].","teleology":[{"year":2002,"claim":"Whether HSPA4 contributes to stress-protective adaptation was unknown; this work showed it mediates a cytoprotective radioadaptive response.","evidence":"Hspa4 transgenic mice with low-dose pre-irradiation followed by high-dose challenge and cell-death assays in splenocytes","pmids":["12005543"],"confidence":"Medium","gaps":["Mechanism linking HSPA4 levels to survival not defined","No molecular targets identified","Effect on intact tissue/organism survival not assessed"]},{"year":2011,"claim":"The physiological requirement for HSPA4 as an HSP70 nucleotide exchange factor was unestablished; knockout revealed an essential role in completing meiotic prophase I during spermatogenesis.","evidence":"Hspa4 knockout mouse with histology, TUNEL, and spermatocyte transcript profiling","pmids":["21487003"],"confidence":"High","gaps":["Specific client proteins protected during meiosis not identified","Whether NEF activity per se is the rescuing function not directly tested","Mechanism of pachytene-stage specificity unknown"]},{"year":2011,"claim":"Whether HSPA4 could be co-opted to promote malignant behavior was unknown; an NBS1-HSF4b-HSPA4 transcriptional axis was shown to drive migration, invasion, and anchorage-independent growth.","evidence":"RT-PCR, Western blot, siRNA knockdown, migration/invasion and soft-agar assays in H1299 cells","pmids":["21208456"],"confidence":"Medium","gaps":["Downstream effectors of HSPA4 in this context undefined","In vivo metastasis not tested","Direct vs. indirect transcriptional control by HSF4b not resolved"]},{"year":2012,"claim":"The role of HSPA4 in maintaining proteostasis in a post-mitotic tissue was unknown; knockout established it is required for cardiac protein quality control and restrains hypertrophic signaling.","evidence":"Hspa4 knockout mice with pressure-overload model, polyubiquitin/hypertrophic-marker blots, echocardiography, and neonatal cardiomyocyte culture","pmids":["22884543"],"confidence":"High","gaps":["Direct cardiac client proteins not identified","Causal order between aggregate accumulation and signaling activation unresolved","Whether NEF activity mediates the cardioprotection not directly shown"]},{"year":2014,"claim":"Whether HSPA4 acts alone was unclear; double-knockout epistasis demonstrated functional redundancy with HSPA4L in embryonic lung maturation.","evidence":"Hspa4l/Hspa4 double-knockout mice with histology, surfactant-protein immunofluorescence, and ubiquitin/Bcl-2 blots","pmids":["23980576"],"confidence":"High","gaps":["Tissue-specific contribution of each paralog not dissected","Pneumocyte client proteins unidentified","Mechanism of redundancy at the molecular level unknown"]},{"year":2019,"claim":"An extracellular/moonlighting role was undescribed; membrane-glycosylated HSPA4 was shown to bind ITGB5 and transduce tumor-IgG signals into Src/NF-κB-driven lymph-node metastasis.","evidence":"Spontaneous metastasis mouse model, B-cell depletion, IgG transfer, reciprocal HSPA4-ITGB5 binding assays, and human serum ELISA","pmids":["30643287"],"confidence":"High","gaps":["How chaperone HSPA4 reaches and is glycosylated at the plasma membrane unknown","Structural basis of HSPA4-ITGB5 interaction not resolved","Relationship to its intracellular NEF function unaddressed"]},{"year":2022,"claim":"Post-translational control of HSPA4 localization and immune function was unknown; SIRT1-mediated deacetylation at K305/K351/K605 was shown to drive nuclear translocation and anti-inflammatory activity.","evidence":"Co-IP, K-to-R site-directed mutagenesis, subcellular fractionation, and SIRT1 transgenic mice in an MPTP PD model","pmids":["35158021"],"confidence":"High","gaps":["Nuclear targets/mechanism of cytokine repression undefined","Which residue dominates the localization switch unclear","Connection to chaperone activity in the nucleus unknown"]},{"year":2024,"claim":"Whether HSPA4 modulates anti-tumor immunity was unknown; it was shown to stabilize ALKBH5 and suppress CD58 via m6A regulation, enabling immune evasion in gastric cancer.","evidence":"Co-IP, meRIP, CD8+ T-cell co-culture cytotoxicity assays, and HSPA4 gain/loss of function","pmids":["38589927"],"confidence":"Medium","gaps":["Whether ALKBH5 stabilization reflects classic chaperone activity unclear","Direct vs. indirect CD58 regulation not fully resolved","In vivo immune-evasion contribution not quantified"]},{"year":2024,"claim":"A role in pathogen entry was untested; HSPA4 was shown to promote clathrin-mediated endocytosis and viral entry via PI3K-Akt/clathrin upregulation and increased HSC70 ATPase activity.","evidence":"HSPA4 knockdown/overexpression, viral titer/copy assays, IFA, PI3K-Akt inhibition, and ATPase activity assays in BRSV infection","pmids":["39599898"],"confidence":"Medium","gaps":["Direct molecular link from HSPA4 to PI3K-Akt activation undefined","Whether HSPA4 acts as NEF for HSC70 in this setting not shown","Generality across other viruses unknown"]},{"year":2024,"claim":"Upstream regulation of HSPA4 in stem-cell differentiation was unknown; it was placed as the functional effector of a LINC01089/miR-1287-5p axis controlling osteogenesis.","evidence":"Dual-luciferase reporter, RIP, RT-qPCR/Western blot, and ALP/alizarin-red osteogenesis assays with knockdown","pmids":["39679709"],"confidence":"Medium","gaps":["Mechanism by which HSPA4 promotes osteogenic differentiation undefined","In vivo bone phenotype not assessed","Whether chaperone function is involved unknown"]},{"year":2024,"claim":"The evolutionary conservation of HSPA4's spermatogenic function was unconfirmed; human HSPA4 partially rescued germ-cell loss in Drosophila Hsc70Cb mutants.","evidence":"Nanos-Gal4 RNAi knockdown and human HSPA4 cDNA cross-species rescue in Drosophila testis (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Rescue is only partial; full functional equivalence not established","Conserved client proteins not identified"]},{"year":2025,"claim":"Whether HSPA4 influences metal homeostasis and cell death was unknown; cytoplasmic HSPA4 was shown to bind transferrin, restrict iron uptake, and attenuate ferroptosis in dopaminergic neurons.","evidence":"Co-IP, HSPA4 gain/loss of function in SH-SY5Y and primary neurons, MPTP PD model, ferroptosis assays, and behavioral testing","pmids":["41068261"],"confidence":"Medium","gaps":["Structural basis of HSPA4-transferrin interaction unresolved","Whether the effect depends on chaperone/NEF activity unknown","Reciprocal validation of the interaction limited"]},{"year":null,"claim":"How HSPA4's core HSP70 nucleotide-exchange activity mechanistically connects to its diverse moonlighting roles (membrane antigen, transferrin binding, ALKBH5 stabilization, nuclear cytokine repression) and which specific client proteins it protects in each tissue remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No tissue-specific HSPA4 client/substrate catalog","No structural model linking NEF activity to non-canonical interactions","Mechanism of plasma-membrane and nuclear targeting undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,9]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,7]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[8]}],"complexes":[],"partners":["HSPA4L","ITGB5","SIRT1","TF","ALKBH5","DNAJC12"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P34932","full_name":"Heat shock 70 kDa protein 4","aliases":["HSP70RY","Heat shock 70-related protein APG-2","Heat shock protein family H member 2"],"length_aa":840,"mass_kda":94.3,"function":"","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P34932/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HSPA4","classification":"Not Classified","n_dependent_lines":22,"n_total_lines":1208,"dependency_fraction":0.018211920529801324},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000170606","cell_line_id":"CID000047","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":2},{"compartment":"nuclear_punctae","grade":2}],"interactors":[{"gene":"HSPA8","stoichiometry":10.0},{"gene":"ATG9A","stoichiometry":0.2},{"gene":"BTF3","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CLTA","stoichiometry":0.2},{"gene":"CLTB","stoichiometry":0.2},{"gene":"DNAJB1","stoichiometry":0.2},{"gene":"DNAJB4","stoichiometry":0.2},{"gene":"DNAJC9","stoichiometry":0.2},{"gene":"POLQ","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000047","total_profiled":1310},"omim":[{"mim_id":"619077","title":"HEAT-SHOCK PROTEIN FAMILY A (HSP70) MEMBER 4-LIKE PROTEIN; HSPA4L","url":"https://www.omim.org/entry/619077"},{"mim_id":"617487","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY B, MEMBER 14; DNAJB14","url":"https://www.omim.org/entry/617487"},{"mim_id":"616333","title":"WNT SIGNALING PATHWAY ACTIVATING NONCODING RNA; WSPAR","url":"https://www.omim.org/entry/616333"},{"mim_id":"601113","title":"HEAT-SHOCK PROTEIN FAMILY A (HSP70), MEMBER 4; HSPA4","url":"https://www.omim.org/entry/601113"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HSPA4"},"hgnc":{"alias_symbol":["HS24/P52","HSPH2"],"prev_symbol":[]},"alphafold":{"accession":"P34932","domains":[{"cath_id":"3.30.420.40","chopping":"5-233_314-395","consensus_level":"medium","plddt":96.0076,"start":5,"end":395},{"cath_id":"2.60.34.10","chopping":"401-503_574-590","consensus_level":"medium","plddt":90.4968,"start":401,"end":590},{"cath_id":"1.20.1270.10","chopping":"593-784","consensus_level":"medium","plddt":93.8249,"start":593,"end":784}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P34932","model_url":"https://alphafold.ebi.ac.uk/files/AF-P34932-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P34932-F1-predicted_aligned_error_v6.png","plddt_mean":86.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HSPA4","jax_strain_url":"https://www.jax.org/strain/search?query=HSPA4"},"sequence":{"accession":"P34932","fasta_url":"https://rest.uniprot.org/uniprotkb/P34932.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P34932/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P34932"}},"corpus_meta":[{"pmid":"30643287","id":"PMC_30643287","title":"Tumor-educated B cells selectively promote breast cancer lymph node metastasis by HSPA4-targeting IgG.","date":"2019","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30643287","citation_count":215,"is_preprint":false},{"pmid":"25798051","id":"PMC_25798051","title":"Upregulation of heat shock proteins (HSPA12A, HSP90B1, HSPA4, HSPA5 and HSPA6) in tumour tissues is associated with poor outcomes from HBV-related early-stage hepatocellular carcinoma.","date":"2015","source":"International journal of medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/25798051","citation_count":149,"is_preprint":false},{"pmid":"21208456","id":"PMC_21208456","title":"Induction of HSPA4 and HSPA14 by NBS1 overexpression contributes to NBS1-induced in vitro metastatic and transformation activity.","date":"2011","source":"Journal of biomedical science","url":"https://pubmed.ncbi.nlm.nih.gov/21208456","citation_count":68,"is_preprint":false},{"pmid":"21487003","id":"PMC_21487003","title":"Heat-shock protein HSPA4 is required for progression of spermatogenesis.","date":"2011","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/21487003","citation_count":50,"is_preprint":false},{"pmid":"12005543","id":"PMC_12005543","title":"Hspa4 (HSP70) is involved in the radioadaptive response: results from mouse splenocytes.","date":"2002","source":"Radiation research","url":"https://pubmed.ncbi.nlm.nih.gov/12005543","citation_count":42,"is_preprint":false},{"pmid":"22884543","id":"PMC_22884543","title":"Targeted disruption of Hspa4 gene leads to cardiac hypertrophy and fibrosis.","date":"2012","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/22884543","citation_count":39,"is_preprint":false},{"pmid":"35158021","id":"PMC_35158021","title":"SIRT1 attenuates neuroinflammation by deacetylating HSPA4 in a mouse model of Parkinson's disease.","date":"2022","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/35158021","citation_count":29,"is_preprint":false},{"pmid":"38589927","id":"PMC_38589927","title":"HSPA4 upregulation induces immune evasion via ALKBH5/CD58 axis in gastric cancer.","date":"2024","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/38589927","citation_count":23,"is_preprint":false},{"pmid":"23980576","id":"PMC_23980576","title":"Respiratory distress and early neonatal lethality in Hspa4l/Hspa4 double-mutant mice.","date":"2014","source":"American journal of respiratory cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/23980576","citation_count":18,"is_preprint":false},{"pmid":"27129500","id":"PMC_27129500","title":"Frameshift Mutations of HSPA4 and MED13 in Gastric and Colorectal Cancers.","date":"2016","source":"Pathology oncology research : POR","url":"https://pubmed.ncbi.nlm.nih.gov/27129500","citation_count":15,"is_preprint":false},{"pmid":"34163243","id":"PMC_34163243","title":"HSPA4 Knockdown Retarded Progression and Development of Colorectal Cancer.","date":"2021","source":"Cancer management and research","url":"https://pubmed.ncbi.nlm.nih.gov/34163243","citation_count":15,"is_preprint":false},{"pmid":"35628491","id":"PMC_35628491","title":"HSPA4 Is a Biomarker of Placenta Accreta and Enhances the Angiogenesis Ability of Vessel Endothelial Cells.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35628491","citation_count":9,"is_preprint":false},{"pmid":"37339521","id":"PMC_37339521","title":"HSPA4 regulated glioma progression via activation of AKT signaling pathway.","date":"2023","source":"Biochemistry and cell biology = Biochimie et biologie 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European Society for Engineering and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40105158","citation_count":2,"is_preprint":false},{"pmid":"39599898","id":"PMC_39599898","title":"HSPA4 Enhances BRSV Entry via Clathrin-Mediated Endocytosis Through Regulating the PI3K-Akt Signaling Pathway and ATPase Activity of HSC70.","date":"2024","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/39599898","citation_count":1,"is_preprint":false},{"pmid":"36185081","id":"PMC_36185081","title":"Inhibition of DNAJC12 Inhibited Tumorigenesis of Rectal Cancer via Downregulating HSPA4 Expression.","date":"2022","source":"Evidence-based complementary and alternative medicine : eCAM","url":"https://pubmed.ncbi.nlm.nih.gov/36185081","citation_count":1,"is_preprint":false},{"pmid":"41068261","id":"PMC_41068261","title":"HSPA4 restrains transferrin in dopaminergic neurons to attenuate ferroptosis in a Parkinson's disease model.","date":"2025","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/41068261","citation_count":0,"is_preprint":false},{"pmid":"41678149","id":"PMC_41678149","title":"HSPA4 and SYVN1 positivity in osteoarthritis synovium as indicators of proteostasis dysfunction.","date":"2026","source":"Clinical and experimental rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/41678149","citation_count":0,"is_preprint":false},{"pmid":"37565223","id":"PMC_37565223","title":"Retracted: Inhibition of DNAJC12 Inhibited Tumorigenesis of Rectal Cancer via Downregulating HSPA4 Expression.","date":"2023","source":"Evidence-based complementary and alternative medicine : eCAM","url":"https://pubmed.ncbi.nlm.nih.gov/37565223","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.13.25337858","title":"The tissue-specific effects of glucose-lowering drug targets on aging mediated through DNA methylation: a multi-omics genetic 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Knockout of Hspa4 in mice leads to impaired spermatogenesis, with pachytene spermatocytes failing to complete meiotic prophase I and undergoing apoptosis, establishing a required role for HSPA4 in spermatogenesis.\",\n      \"method\": \"Hspa4 knockout mouse model; histological analysis; TUNEL assay; RT-PCR for spermatocyte-specific transcripts\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse with defined cellular phenotype (meiotic arrest, apoptosis) replicated across developmental time points, multiple orthogonal methods\",\n      \"pmids\": [\"21487003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HSPA4, acting as a nucleotide exchange factor for HSP70 chaperones, is required for cardiac protein quality control. Hspa4 knockout mice develop cardiac hypertrophy and fibrosis associated with accumulation of polyubiquitinated proteins in cardiomyocytes, and with enhanced activation of gp130-STAT3, CaMKII, and calcineurin-NFAT signaling pathways.\",\n      \"method\": \"Hspa4 knockout mouse model; Western blot for polyubiquitinated proteins and hypertrophic markers; immunofluorescence; echocardiography; pressure overload model; cultured neonatal Hspa4 KO cardiomyocytes; gene expression profiling\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse with multiple orthogonal methods (protein aggregation, signaling, histology, in vitro cardiomyocyte culture), single rigorous study\",\n      \"pmids\": [\"22884543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HSPA4 and its paralog HSPA4L functionally collaborate as cochaperones during embryonic lung maturation. Double-knockout Hspa4l−/−Hspa4−/− mice display pulmonary hypoplasia with accumulation of ubiquitinated proteins in lungs, impaired type I/II pneumocyte maturation, and neonatal lethality, while single knockouts survive, demonstrating functional redundancy between the two HSP110 family members.\",\n      \"method\": \"Hspa4l−/−Hspa4−/− double-knockout mouse model; histological analysis; immunofluorescence for surfactant proteins; Western blot for ubiquitinated proteins and Bcl-2; proliferation and apoptosis assays\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — double-KO genetic epistasis with multiple orthogonal readouts in a single rigorous study demonstrating functional complementarity\",\n      \"pmids\": [\"23980576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NBS1 overexpression induces HSPA4 expression via upregulation of heat shock transcription factor 4b (HSF4b). siRNA-mediated knockdown of HSPA4 in NBS1-overexpressing H1299 cells decreased in vitro migration, invasion, and anchorage-independent growth, establishing a NBS1-HSF4b-HSPA4 signaling axis promoting metastatic behavior independently of MMP2.\",\n      \"method\": \"RT-PCR; Western blot; siRNA knockdown; in vitro migration/invasion assays; soft agar colony formation; gelatin zymography\",\n      \"journal\": \"Journal of biomedical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA KD with defined phenotypic readouts and pathway placement, single lab, two orthogonal functional assays\",\n      \"pmids\": [\"21208456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Membrane-expressed glycosylated HSPA4 is targeted by pathogenic IgG produced by tumor-educated B cells in draining lymph nodes. Anti-HSPA4 IgG activates ITGB5 (a HSPA4-binding protein) and downstream Src/NF-κB signaling in tumor cells, promoting CXCR4/SDF1α-mediated lymph node metastasis.\",\n      \"method\": \"Mouse model of spontaneous lymph node metastasis; B cell depletion; IgG isolation and treatment; co-IP/binding assays for HSPA4-ITGB5 interaction; signaling pathway analysis; serum IgG ELISA in human subjects\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assay identifying HSPA4-ITGB5 interaction, in vivo mouse model, mechanistic signaling pathway validation, multiple orthogonal methods\",\n      \"pmids\": [\"30643287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SIRT1 physically interacts with HSPA4 and deacetylates it at lysine residues K305, K351, and K605. This deacetylation induces nuclear translocation of HSPA4 and represses proinflammatory cytokine expression in glial cells. Mutation of these lysine residues to arginine retains HSPA4 in the cytoplasm and abolishes its anti-inflammatory activity.\",\n      \"method\": \"Co-immunoprecipitation; site-directed mutagenesis of K305/351/605R; subcellular fractionation/immunofluorescence; SIRT1 transgenic mice; MPTP-induced PD model; cytokine expression analysis\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — site-directed mutagenesis of specific deacetylation sites combined with Co-IP and subcellular localization with functional consequence, supported by in vivo transgenic mouse model\",\n      \"pmids\": [\"35158021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HSPA4 (HSP70) is involved in the radioadaptive response. High-dose radiation upregulates Hspa4 expression in mouse splenocytes. Splenocytes from Hspa4 transgenic mice showed reduced cell death after high-dose irradiation when preirradiated with a low dose, demonstrating that HSPA4 upregulation mediates the adaptive cytoprotective response to radiation.\",\n      \"method\": \"RT-PCR; Hspa4 transgenic mice; low-dose pre-irradiation followed by high-dose challenge; cell viability/death assay\",\n      \"journal\": \"Radiation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic mouse model with defined functional phenotype, single lab, two methods (expression + cell death)\",\n      \"pmids\": [\"12005543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HSPA4 upregulation in gastric cancer stabilizes the m6A demethylase ALKBH5 protein, which in turn reduces CD58 expression via m6A methylation regulation in GC cells, leading to impaired CD8+ T cell cytotoxicity and PD1/PDL1 axis activation and thereby promoting immune evasion.\",\n      \"method\": \"Co-immunoprecipitation; meRIP (methylated RNA immunoprecipitation); co-culture cytotoxicity assay with CD8+ T cells; HSPA4 overexpression/knockdown; Western blot; multiplex fluorescent immunohistochemistry\",\n      \"journal\": \"Journal of experimental & clinical cancer research : CR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for protein interaction, meRIP for m6A regulation, functional co-culture assay, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"38589927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HSPA4 promotes clathrin-mediated endocytosis and facilitates bovine respiratory syncytial virus (BRSV) entry by activating the PI3K-Akt signaling pathway to upregulate clathrin heavy chain (CHC) expression, and by increasing the ATPase activity of HSC70, thereby enhancing clathrin-mediated endocytic efficiency.\",\n      \"method\": \"Western blot; virus titer assay; virus copy analysis; immunofluorescence assay (IFA); HSPA4 knockdown/overexpression; PI3K-Akt pathway inhibition; ATPase activity assay\",\n      \"journal\": \"Viruses\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays (ATPase activity, viral entry, signaling), single lab, orthogonal readouts but no structural or reconstitution data\",\n      \"pmids\": [\"39599898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HSPA4 physically interacts with transferrin in the cytoplasm of dopaminergic neurons and inhibits transferrin export from the cell, thereby reducing extracellular iron uptake and attenuating ferroptosis. HSPA4 overexpression reduces ferroptosis in erastin-treated cells and MPTP-treated PD model mice, while HSPA4 knockdown exacerbates ferroptosis.\",\n      \"method\": \"Co-immunoprecipitation for HSPA4-transferrin interaction; HSPA4 overexpression/knockdown in SH-SY5Y cells and primary dopaminergic neurons; MPTP-induced mouse PD model; ferroptosis assays; behavioral testing\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifying HSPA4-transferrin interaction, gain/loss-of-function in vitro and in vivo, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41068261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNAJC12 (an HSP40 co-chaperone) physically interacts with HSPA4 as demonstrated by co-immunoprecipitation. Rescue experiments showed that HSPA4 overexpression restored proliferation and migration capacity suppressed by DNAJC12 silencing, placing HSPA4 downstream of DNAJC12 in rectal cancer cell biology. (Note: the original paper PMID:36185081 was subsequently retracted per PMID:37565223.)\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; rescue overexpression experiments; CCK-8; wound healing; xenograft\",\n      \"journal\": \"Evidence-based complementary and alternative medicine : eCAM\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single Co-IP method, and the paper was retracted (PMID:37565223); evidence should not be relied upon\",\n      \"pmids\": [\"36185081\", \"37565223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"miR-1287-5p directly targets HSPA4 mRNA, negatively regulating HSPA4 protein levels. HSPA4 acts as a downstream functional mediator in the LINC01089/miR-1287-5p axis that inhibits osteogenic differentiation of human mesenchymal stem cells; miR-1287-5p depletion blocked LINC01089 knockdown-induced osteogenesis, and HSPA4 knockdown attenuated osteogenic differentiation.\",\n      \"method\": \"Dual-luciferase reporter assay; RNA immunoprecipitation (RIP); RT-qPCR; Western blot; ALP activity; alizarin red S staining; siRNA knockdown\",\n      \"journal\": \"Bone & joint research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual-luciferase and RIP confirm miRNA-target interaction, functional osteogenesis assays with KD, single lab\",\n      \"pmids\": [\"39679709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In Drosophila, the HSPA4 family ortholog Hsc70Cb is required for spermatogonia survival and sperm individualisation. Introduction of human HSPA4 cDNA into Hsc70Cb-deficient flies partially rescued germ cell survival to the spermatocyte stage, demonstrating functional conservation between Drosophila Hsc70Cb and human HSPA4 in spermatogenesis.\",\n      \"method\": \"RNAi-mediated knockdown using Nanos-Gal4; human HSPA4 cDNA rescue experiment in Drosophila; testis histology\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic rescue with human HSPA4 cDNA in Drosophila model, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"HSPA4 is a member of the HSP110 family that functions as a nucleotide exchange factor (NEF) for HSP70 chaperones in protein quality control; it is required for spermatogenesis (meiotic prophase I completion), cardiac proteostasis (preventing accumulation of misfolded/polyubiquitinated proteins and hypertrophic signaling), and embryonic lung maturation (redundantly with HSPA4L); it is deacetylated by SIRT1 at K305/K351/K605, promoting its nuclear translocation to repress neuroinflammation; it interacts with transferrin to restrain iron import and attenuate ferroptosis in dopaminergic neurons; at the plasma membrane it acts as a glycosylated antigen whose ligation by IgG activates ITGB5/Src/NF-κB to drive tumor metastasis; and it promotes viral clathrin-mediated endocytosis by activating PI3K-Akt/CHC and increasing HSC70 ATPase activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HSPA4 is an HSP110-family nucleotide exchange factor for HSP70 chaperones that supports protein quality control across multiple tissues, with loss-of-function phenotypes converging on accumulation of polyubiquitinated/misfolded proteins [#0, #1]. Genetic ablation in mice arrests pachytene spermatocytes in meiotic prophase I and triggers their apoptosis, establishing an essential role in spermatogenesis [#0], a function conserved through the Drosophila ortholog Hsc70Cb, which human HSPA4 cDNA partially rescues [#12]. In the heart, HSPA4 loss causes accumulation of polyubiquitinated proteins and drives hypertrophy and fibrosis through gp130-STAT3, CaMKII, and calcineurin-NFAT signaling [#1], and together with its redundant paralog HSPA4L it is required for embryonic lung maturation, with double-knockout mice showing pulmonary hypoplasia and accumulated ubiquitinated proteins [#2]. Beyond chaperone-associated proteostasis, HSPA4 is subject to regulation and moonlighting roles: SIRT1 deacetylates it at K305/K351/K605 to drive nuclear translocation that represses proinflammatory cytokine expression in glia [#5], and cytoplasmic HSPA4 binds transferrin to limit iron uptake and attenuate ferroptosis in dopaminergic neurons [#9]. In cancer, membrane-displayed glycosylated HSPA4 binds ITGB5 and, when ligated by tumor-educated B-cell IgG, activates Src/NF-\\u03baB signaling to promote lymph-node metastasis [#4], while intracellular HSPA4 stabilizes the m6A demethylase ALKBH5 to suppress CD58 and impair CD8+ T-cell cytotoxicity [#7]. HSPA4 also promotes clathrin-mediated viral endocytosis by activating PI3K-Akt to upregulate clathrin heavy chain and by increasing HSC70 ATPase activity [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Whether HSPA4 contributes to stress-protective adaptation was unknown; this work showed it mediates a cytoprotective radioadaptive response.\",\n      \"evidence\": \"Hspa4 transgenic mice with low-dose pre-irradiation followed by high-dose challenge and cell-death assays in splenocytes\",\n      \"pmids\": [\"12005543\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking HSPA4 levels to survival not defined\", \"No molecular targets identified\", \"Effect on intact tissue/organism survival not assessed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"The physiological requirement for HSPA4 as an HSP70 nucleotide exchange factor was unestablished; knockout revealed an essential role in completing meiotic prophase I during spermatogenesis.\",\n      \"evidence\": \"Hspa4 knockout mouse with histology, TUNEL, and spermatocyte transcript profiling\",\n      \"pmids\": [\"21487003\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific client proteins protected during meiosis not identified\", \"Whether NEF activity per se is the rescuing function not directly tested\", \"Mechanism of pachytene-stage specificity unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Whether HSPA4 could be co-opted to promote malignant behavior was unknown; an NBS1-HSF4b-HSPA4 transcriptional axis was shown to drive migration, invasion, and anchorage-independent growth.\",\n      \"evidence\": \"RT-PCR, Western blot, siRNA knockdown, migration/invasion and soft-agar assays in H1299 cells\",\n      \"pmids\": [\"21208456\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effectors of HSPA4 in this context undefined\", \"In vivo metastasis not tested\", \"Direct vs. indirect transcriptional control by HSF4b not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The role of HSPA4 in maintaining proteostasis in a post-mitotic tissue was unknown; knockout established it is required for cardiac protein quality control and restrains hypertrophic signaling.\",\n      \"evidence\": \"Hspa4 knockout mice with pressure-overload model, polyubiquitin/hypertrophic-marker blots, echocardiography, and neonatal cardiomyocyte culture\",\n      \"pmids\": [\"22884543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cardiac client proteins not identified\", \"Causal order between aggregate accumulation and signaling activation unresolved\", \"Whether NEF activity mediates the cardioprotection not directly shown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Whether HSPA4 acts alone was unclear; double-knockout epistasis demonstrated functional redundancy with HSPA4L in embryonic lung maturation.\",\n      \"evidence\": \"Hspa4l/Hspa4 double-knockout mice with histology, surfactant-protein immunofluorescence, and ubiquitin/Bcl-2 blots\",\n      \"pmids\": [\"23980576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific contribution of each paralog not dissected\", \"Pneumocyte client proteins unidentified\", \"Mechanism of redundancy at the molecular level unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"An extracellular/moonlighting role was undescribed; membrane-glycosylated HSPA4 was shown to bind ITGB5 and transduce tumor-IgG signals into Src/NF-\\u03baB-driven lymph-node metastasis.\",\n      \"evidence\": \"Spontaneous metastasis mouse model, B-cell depletion, IgG transfer, reciprocal HSPA4-ITGB5 binding assays, and human serum ELISA\",\n      \"pmids\": [\"30643287\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How chaperone HSPA4 reaches and is glycosylated at the plasma membrane unknown\", \"Structural basis of HSPA4-ITGB5 interaction not resolved\", \"Relationship to its intracellular NEF function unaddressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Post-translational control of HSPA4 localization and immune function was unknown; SIRT1-mediated deacetylation at K305/K351/K605 was shown to drive nuclear translocation and anti-inflammatory activity.\",\n      \"evidence\": \"Co-IP, K-to-R site-directed mutagenesis, subcellular fractionation, and SIRT1 transgenic mice in an MPTP PD model\",\n      \"pmids\": [\"35158021\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nuclear targets/mechanism of cytokine repression undefined\", \"Which residue dominates the localization switch unclear\", \"Connection to chaperone activity in the nucleus unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Whether HSPA4 modulates anti-tumor immunity was unknown; it was shown to stabilize ALKBH5 and suppress CD58 via m6A regulation, enabling immune evasion in gastric cancer.\",\n      \"evidence\": \"Co-IP, meRIP, CD8+ T-cell co-culture cytotoxicity assays, and HSPA4 gain/loss of function\",\n      \"pmids\": [\"38589927\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ALKBH5 stabilization reflects classic chaperone activity unclear\", \"Direct vs. indirect CD58 regulation not fully resolved\", \"In vivo immune-evasion contribution not quantified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A role in pathogen entry was untested; HSPA4 was shown to promote clathrin-mediated endocytosis and viral entry via PI3K-Akt/clathrin upregulation and increased HSC70 ATPase activity.\",\n      \"evidence\": \"HSPA4 knockdown/overexpression, viral titer/copy assays, IFA, PI3K-Akt inhibition, and ATPase activity assays in BRSV infection\",\n      \"pmids\": [\"39599898\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link from HSPA4 to PI3K-Akt activation undefined\", \"Whether HSPA4 acts as NEF for HSC70 in this setting not shown\", \"Generality across other viruses unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Upstream regulation of HSPA4 in stem-cell differentiation was unknown; it was placed as the functional effector of a LINC01089/miR-1287-5p axis controlling osteogenesis.\",\n      \"evidence\": \"Dual-luciferase reporter, RIP, RT-qPCR/Western blot, and ALP/alizarin-red osteogenesis assays with knockdown\",\n      \"pmids\": [\"39679709\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which HSPA4 promotes osteogenic differentiation undefined\", \"In vivo bone phenotype not assessed\", \"Whether chaperone function is involved unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The evolutionary conservation of HSPA4's spermatogenic function was unconfirmed; human HSPA4 partially rescued germ-cell loss in Drosophila Hsc70Cb mutants.\",\n      \"evidence\": \"Nanos-Gal4 RNAi knockdown and human HSPA4 cDNA cross-species rescue in Drosophila testis (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Rescue is only partial; full functional equivalence not established\", \"Conserved client proteins not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Whether HSPA4 influences metal homeostasis and cell death was unknown; cytoplasmic HSPA4 was shown to bind transferrin, restrict iron uptake, and attenuate ferroptosis in dopaminergic neurons.\",\n      \"evidence\": \"Co-IP, HSPA4 gain/loss of function in SH-SY5Y and primary neurons, MPTP PD model, ferroptosis assays, and behavioral testing\",\n      \"pmids\": [\"41068261\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of HSPA4-transferrin interaction unresolved\", \"Whether the effect depends on chaperone/NEF activity unknown\", \"Reciprocal validation of the interaction limited\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HSPA4's core HSP70 nucleotide-exchange activity mechanistically connects to its diverse moonlighting roles (membrane antigen, transferrin binding, ALKBH5 stabilization, nuclear cytokine repression) and which specific client proteins it protects in each tissue remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No tissue-specific HSPA4 client/substrate catalog\", \"No structural model linking NEF activity to non-canonical interactions\", \"Mechanism of plasma-membrane and nuclear targeting undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 9]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HSPA4L\", \"ITGB5\", \"SIRT1\", \"TF\", \"ALKBH5\", \"DNAJC12\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":4,"faith_total":6,"faith_pct":66.66666666666667}}