{"gene":"HSPA4L","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":1996,"finding":"Osp94 (HSPA4L) was identified as a new member of the Hsp110/SSE gene subfamily with a putative N-terminal ATP-binding domain and a putative C-terminal peptide-binding domain, consistent with molecular chaperone function. In vitro translated Osp94 migrated as a 105-110 kDa protein on SDS-PAGE.","method":"cDNA cloning, domain analysis, in vitro translation/SDS-PAGE","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain identification by sequence analysis confirmed by in vitro translation; single lab but multiple methods","pmids":["8647834"],"is_preprint":false},{"year":1996,"finding":"Osp94 (HSPA4L) mRNA expression is up-regulated in renal inner medullary collecting duct cells (mIMCD3) by hyperosmotic NaCl stress and heat stress, and its expression in mouse kidney parallels the corticomedullary osmolality gradient (highest in inner medulla), increasing further during water restriction.","method":"Northern blot analysis, in situ hybridization, osmolality manipulation in mIMCD3 cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct induction experiments in cells and tissue, single lab, two orthogonal methods","pmids":["8647834"],"is_preprint":false},{"year":1997,"finding":"APG-1 (HSPA4L) mRNA is constitutively and developmentally expressed in testicular germ cells (spermatocytes and spermatids) but is not heat-inducible in germ cells, in contrast to somatic cells where it is induced by a 32°C-to-39°C temperature shift. Heat shock factor 1 (HSF1) binds to heat shock elements in the 5'-flanking region of the apg-1 gene, driving transcriptional activation in somatic cells.","method":"Northern blot, in situ hybridization, nuclear run-on assay, gel mobility shift assay, W/Wv mutant testis analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (nuclear run-on, EMSA, in situ hybridization, mutant mouse model) in single rigorous study; replicated by Kaneko et al. 1997 BBRC","pmids":["9006898","9144406"],"is_preprint":false},{"year":2004,"finding":"The 5'-flanking region of the Osp94 (HSPA4L) gene contains a tonicity-response element (Osp94-TonE; 5'-TGGAAAGGACCAG-3') distinct from the heat shock element (HSE). TonEBP binds to this element under hypertonic stress. MAPK pathways (p38, ERK, JNK) and the proteasome system are required for hypertonic NaCl-induced Osp94 expression.","method":"Luciferase reporter assay, electrophoretic gel mobility-shift assay (EMSA), pharmacological inhibitors (SB203580, PD98059, U0126, SP600125, MG132) in mIMCD3 cells","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — EMSA directly demonstrated TonEBP binding; luciferase reporters and multiple specific inhibitors used; single lab with multiple orthogonal methods","pmids":["15018608"],"is_preprint":false},{"year":2006,"finding":"Hspa4l-deficient (knockout) male mice show ~42% infertility with drastically reduced sperm count and motility due to increased germ cell apoptosis from late pachytene spermatocytes through postmeiotic spermatids. HSPA4L protein is highly expressed in spermatogenic cells and is required for normal spermatogenesis. Additionally, Hspa4l-null mice display increased susceptibility to osmotic stress and 12% develop hydronephrosis.","method":"Gene targeting (knockout mouse), histology, TUNEL apoptosis assay, sperm count and motility analysis, immunohistochemistry, Western blot","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — defined KO mouse with specific cellular phenotype (apoptosis assay, sperm count), multiple orthogonal methods; foundational loss-of-function study","pmids":["16923965"],"is_preprint":false},{"year":2013,"finding":"HSPA4L (Apg-1) physically interacts with Nogo-A (RTN4-A) through Nogo-A's central NiG domain. The interaction is selective: Apg-1 does not bind RTN1-A (closest Nogo-A paralogue), and Nogo-A does not bind Apg-2 or Hsp105 (other Hsp110 family members). Under hypoxic stress, both Nogo-A and Apg-1 are co-upregulated in hippocampal neurons; oxidative stress (H2O2) reduces both.","method":"Affinity precipitation, co-immunoprecipitation, proximity ligation assay in primary hippocampal neurons from Nogo-deficient mice","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and proximity ligation assay confirming interaction; single lab with three orthogonal binding methods","pmids":["23909438"],"is_preprint":false},{"year":2014,"finding":"HSPA4L and HSPA4 act as functionally redundant cochaperones in embryonic lung maturation. Hspa4l(-/-)Hspa4(-/-) double-knockout mice show pulmonary hypoplasia with mesenchymal hypercellularity (increased proliferation, decreased apoptosis), elevated Bcl-2, impaired type I/II pneumocyte maturation (reduced surfactant protein B, pro-SPC, AQP5), and accumulation of ubiquitinated proteins indicating impaired chaperone activity.","method":"Double-knockout mouse generation, histology, immunohistochemistry, proliferation/apoptosis assays, Western blot for ubiquitinated proteins and chaperone substrates","journal":"American journal of respiratory cell and molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — double-KO genetic epistasis with multiple cellular readouts and ubiquitin accumulation as direct chaperone activity measure; single lab but highly rigorous","pmids":["23980576"],"is_preprint":false},{"year":2019,"finding":"Apg-1 (HSPA4L) protein is upregulated by bortezomib in multiple myeloma cells via HSF1 nuclear translocation. Silencing Apg-1 sensitizes myeloma cells to bortezomib, as evidenced by increased cleaved caspase-3 and PARP cleavage, indicating Apg-1 promotes cell survival downstream of HSF1 activation under proteasome stress.","method":"shRNA knockdown, Western blot (Apg-1, cleaved caspase-3, PARP), HSF1 nuclear translocation assay, triptolide pharmacological inhibition, co-culture with bone marrow stromal cells","journal":"Experimental hematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined apoptotic phenotype and pathway placement (HSF1→Apg-1→caspase-3); single lab, multiple methods","pmids":["31899217"],"is_preprint":false},{"year":2022,"finding":"Osp94 (HSPA4L) functions as a holdase that suppresses heat-induced aggregation of luciferase and enables its refolding. The SBDβ and H domains (C-terminal region) are critical for protein disaggregation and refolding in reticulocyte lysate with Hsc70/Hsp40. The C-terminal LH domain plays a PA28α-like role in refolding Hsp90-bound denatured substrate, and a chimeric protein replacing the H domain with PA28α retains this activity. Refolding of heat-inactivated luciferase requires collaboration between Osp94, Hsc70, Hsp40, and the reticulocyte lysate chaperone machinery.","method":"In vitro aggregation suppression assay, luciferase reactivation assay, targeted deletion mutagenesis of C-terminal domains, biotin-tag cross-linking, chimeric protein construction, rabbit reticulocyte lysate complementation","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of chaperone activity combined with mutagenesis and domain-swap experiments in single rigorous study; multiple orthogonal biochemical approaches","pmids":["35237814"],"is_preprint":false},{"year":2016,"finding":"miR-429 directly targets the 3'UTR of HSPA4L mRNA, suppressing HSPA4L mRNA and protein expression. In sperms from asthenospermia patients, miR-429 is upregulated and HSPA4L is correspondingly downregulated, with an inverse correlation between miR-429 and HSPA4L mRNA levels.","method":"Luciferase reporter assay with HSPA4L 3'UTR, transfection study, bioinformatics (TargetScan), qRT-PCR, Western blot","journal":"Sichuan da xue xue bao. Yi xue ban","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter directly confirmed miR-429 targeting of HSPA4L 3'UTR; single lab with orthogonal validation in clinical samples","pmids":["28598115"],"is_preprint":false},{"year":2024,"finding":"Human HSPA4L cDNA introduced into Drosophila Hsc70Cb-knockdown (HSPA4/HSPA4L ortholog) testes partially rescues germ cell progression to spermatocyte stage before apoptosis, demonstrating functional conservation of HSPA4L in supporting male germ cell development across species.","method":"RNAi knockdown in Drosophila male germline, transgenic rescue with human HSPA4L cDNA, histology, Nanos-Gal4 driver system","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic rescue experiment with human cDNA demonstrating functional conservation; preprint, single lab","pmids":["bio_10.1101_2024.12.09.627449"],"is_preprint":true}],"current_model":"HSPA4L (Osp94/APG-1/HSPH3) is a member of the Hsp110/SSE chaperone subfamily that functions as a holdase and disaggregase: its C-terminal SBDβ and H domains suppress protein aggregation and enable Hsc70/Hsp40-assisted refolding of denatured substrates via a PA28α-like mechanism; it acts as a cochaperone redundantly with HSPA4 during embryonic lung maturation (loss of both causes ubiquitinated protein accumulation); it is transcriptionally regulated by TonEBP via a distinct tonicity-response element (Osp94-TonE) and by HSF1 via heat shock elements, with MAPK pathways and the proteasome required for hypertonic induction; it physically interacts with Nogo-A selectively among Hsp110 family members; it is essential for normal spermatogenesis (KO mice show germ cell apoptosis and male infertility) and is regulated post-transcriptionally in sperm by miR-429; and it promotes survival of myeloma cells under proteasome stress downstream of HSF1."},"narrative":{"mechanistic_narrative":"HSPA4L (Osp94/APG-1) is an Hsp110/SSE-subfamily molecular chaperone that prevents protein aggregation and promotes refolding of denatured substrates, supporting proteostasis under thermal, osmotic, and proteasome stress [PMID:8647834, PMID:35237814]. Biochemically it acts as a holdase: it suppresses heat-induced aggregation of luciferase and, through its C-terminal SBDβ and H domains, enables disaggregation and Hsc70/Hsp40-assisted refolding, with the LH domain playing a PA28α-like role that a PA28α domain-swap can substitute for [PMID:35237814]. The gene is transcriptionally driven by two distinct programs: HSF1 binding to heat shock elements in somatic cells [PMID:9006898, PMID:9144406], and TonEBP binding to a dedicated tonicity-response element (Osp94-TonE) during hypertonic stress, which additionally requires MAPK signaling and the proteasome [PMID:15018608]. Genetically, HSPA4L is essential for spermatogenesis—knockout males are infertile with germ-cell apoptosis [PMID:16923965]—and acts redundantly with HSPA4 in embryonic lung maturation, where double loss causes accumulation of ubiquitinated proteins reflecting failed chaperone activity [PMID:23980576]. It physically interacts selectively with Nogo-A among Hsp110 members [PMID:23909438], is post-transcriptionally repressed by miR-429 [PMID:28598115], and promotes myeloma cell survival downstream of HSF1 under proteasome stress [PMID:31899217].","teleology":[{"year":1996,"claim":"Established HSPA4L's identity as an Hsp110/SSE chaperone and linked it to osmotic stress, framing it as a stress-inducible proteostasis factor in the renal medulla.","evidence":"cDNA cloning and domain analysis with in vitro translation; Northern blot and in situ hybridization under hyperosmotic and heat stress in mIMCD3 cells and kidney","pmids":["8647834"],"confidence":"Medium","gaps":["Chaperone activity inferred from domain architecture, not demonstrated","No substrate identified at this stage"]},{"year":1997,"claim":"Revealed cell-type-specific transcriptional control, showing HSF1 drives heat-inducible expression in somatic cells while germ cells express HSPA4L constitutively and non-inducibly.","evidence":"Nuclear run-on, EMSA, in situ hybridization, and W/Wv mutant testis analysis","pmids":["9006898","9144406"],"confidence":"High","gaps":["Functional role in germ cells not yet tested by loss-of-function","Mechanism of germ-cell-specific non-inducibility unresolved"]},{"year":2004,"claim":"Defined a second, tonicity-specific promoter element and its trans-acting factor, distinguishing osmotic from heat-shock induction of HSPA4L.","evidence":"Luciferase reporters, EMSA showing TonEBP binding to Osp94-TonE, and pharmacological inhibition of MAPK/proteasome in mIMCD3 cells","pmids":["15018608"],"confidence":"High","gaps":["Mechanism linking proteasome activity to transcriptional induction unclear","In vivo relevance of TonE element not tested"]},{"year":2006,"claim":"Provided the first in vivo loss-of-function evidence that HSPA4L is required for spermatogenesis and protects against osmotic stress.","evidence":"Hspa4l knockout mouse with histology, TUNEL, sperm count/motility, and immunohistochemistry","pmids":["16923965"],"confidence":"High","gaps":["Molecular chaperone substrates in germ cells not identified","Partial (~42%) infertility implies compensation that was uncharacterized"]},{"year":2013,"claim":"Identified a selective physical partner, distinguishing HSPA4L from other Hsp110 members and linking it to neuronal stress responses.","evidence":"Affinity precipitation, reciprocal co-immunoprecipitation, and proximity ligation assay in primary hippocampal neurons","pmids":["23909438"],"confidence":"Medium","gaps":["Functional consequence of the Nogo-A interaction not established","Whether HSPA4L chaperones Nogo-A unknown"]},{"year":2014,"claim":"Demonstrated genetic redundancy with HSPA4 and directly tied HSPA4L to clearance of ubiquitinated proteins in a developmental context.","evidence":"Hspa4l/Hspa4 double-knockout mice with histology, proliferation/apoptosis assays, and Western blot for ubiquitinated proteins and surfactant markers","pmids":["23980576"],"confidence":"High","gaps":["Specific substrates accumulating in lung not identified","Division of labor between HSPA4 and HSPA4L not resolved"]},{"year":2017,"claim":"Established a post-transcriptional repression mechanism connecting miR-429 dysregulation to reduced HSPA4L in human asthenospermia.","evidence":"Luciferase reporter of HSPA4L 3'UTR, transfection, qRT-PCR, and Western blot in patient sperm samples","pmids":["28598115"],"confidence":"Medium","gaps":["Causal contribution of miR-429/HSPA4L axis to human infertility not proven","Correlative clinical data only"]},{"year":2019,"claim":"Placed HSPA4L downstream of HSF1 as a pro-survival effector under proteasome stress in cancer cells.","evidence":"shRNA knockdown with bortezomib, cleaved caspase-3/PARP Western blots, HSF1 nuclear translocation, and triptolide inhibition in multiple myeloma cells","pmids":["31899217"],"confidence":"Medium","gaps":["Substrates protecting myeloma cells not identified","Single cell-context; generality across tumors untested"]},{"year":2022,"claim":"Resolved the biochemical mechanism, defining HSPA4L as a holdase/disaggregase and mapping the C-terminal domains responsible for refolding via a PA28α-like activity.","evidence":"In vitro aggregation suppression and luciferase reactivation assays with domain-deletion and PA28α chimera mutants in reticulocyte lysate with Hsc70/Hsp40","pmids":["35237814"],"confidence":"High","gaps":["Physiological substrates in vivo not identified","Structural basis of the PA28α-like H-domain function not solved"]},{"year":2024,"claim":"Demonstrated cross-species functional conservation of HSPA4L in supporting male germ cell development.","evidence":"Transgenic rescue of Drosophila Hsc70Cb knockdown testes with human HSPA4L cDNA (preprint)","pmids":["bio_10.1101_2024.12.09.627449"],"confidence":"Medium","gaps":["Only partial rescue achieved","Preprint, single lab; mechanism of germ-cell support not defined"]},{"year":null,"claim":"The endogenous physiological substrates of HSPA4L in germ cells, lung, and tumor cells remain unidentified, leaving the link between its in vitro holdase activity and specific in vivo phenotypes incomplete.","evidence":"","pmids":[],"confidence":"High","gaps":["No in vivo substrate repertoire defined","No high-resolution structure of the chaperone in complex with substrate","Mechanism of selective Nogo-A binding unexplained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,8]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[8]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[8]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[8,6]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[1,3]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[4]}],"complexes":[],"partners":["HSPA4","RTN4","HSC70","HSP40","HSF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O95757","full_name":"Heat shock 70 kDa protein 4L","aliases":["Heat shock 70-related protein APG-1","Heat shock protein family H member 3","Heat-shock protein family A member 4-like protein","HSPA4-like protein","Osmotic stress protein 94"],"length_aa":839,"mass_kda":94.5,"function":"Possesses chaperone activity in vitro where it inhibits aggregation of citrate synthase","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/O95757/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HSPA4L","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000164070","cell_line_id":"CID000048","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"DNAJB1","stoichiometry":0.2},{"gene":"DNAJC7","stoichiometry":0.2},{"gene":"HSPA5","stoichiometry":0.2},{"gene":"RASGRP1","stoichiometry":0.2},{"gene":"CCAR1","stoichiometry":0.2},{"gene":"HSPA8","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000048","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":"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":"Cytosol","reliability":"Approved"},{"location":"Centrosome","reliability":"Additional"},{"location":"Perinuclear theca","reliability":"Additional"},{"location":"Calyx","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"testis","ntpm":101.7}],"url":"https://www.proteinatlas.org/search/HSPA4L"},"hgnc":{"alias_symbol":["APG-1","Osp94","HSPH3"],"prev_symbol":[]},"alphafold":{"accession":"O95757","domains":[{"cath_id":"3.30.420.40","chopping":"3-231_313-392","consensus_level":"medium","plddt":96.2964,"start":3,"end":392},{"cath_id":"3.90.640.10","chopping":"232-312","consensus_level":"medium","plddt":96.7086,"start":232,"end":312},{"cath_id":"1.20.1270.10","chopping":"614-788","consensus_level":"medium","plddt":92.8954,"start":614,"end":788}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95757","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95757-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95757-F1-predicted_aligned_error_v6.png","plddt_mean":86.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HSPA4L","jax_strain_url":"https://www.jax.org/strain/search?query=HSPA4L"},"sequence":{"accession":"O95757","fasta_url":"https://rest.uniprot.org/uniprotkb/O95757.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95757/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95757"}},"corpus_meta":[{"pmid":"8647834","id":"PMC_8647834","title":"Osmotic stress protein 94 (Osp94). A new member of the Hsp110/SSE gene subfamily.","date":"1996","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8647834","citation_count":85,"is_preprint":false},{"pmid":"16923965","id":"PMC_16923965","title":"Hspa4l-deficient mice display increased incidence of male infertility and hydronephrosis development.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16923965","citation_count":68,"is_preprint":false},{"pmid":"9006898","id":"PMC_9006898","title":"A novel hsp110-related gene, apg-1, that is abundantly expressed in the testis responds to a low temperature heat shock rather than the traditional elevated temperatures.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9006898","citation_count":62,"is_preprint":false},{"pmid":"26486082","id":"PMC_26486082","title":"The potent tumor suppressor miR-497 inhibits cancer phenotypes in nasopharyngeal carcinoma by targeting ANLN and HSPA4L.","date":"2015","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26486082","citation_count":54,"is_preprint":false},{"pmid":"15018608","id":"PMC_15018608","title":"Regulation of expression of the stress response gene, Osp94: identification of the tonicity response element and intracellular signalling pathways.","date":"2004","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/15018608","citation_count":34,"is_preprint":false},{"pmid":"9647773","id":"PMC_9647773","title":"Induction of Apg-1, a member of the heat shock protein 110 family, following transient forebrain ischemia in the rat brain.","date":"1998","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9647773","citation_count":30,"is_preprint":false},{"pmid":"11389747","id":"PMC_11389747","title":"Expression of Apg-1, a member of the Hsp110 family, in the human testis and sperm.","date":"2001","source":"International journal of urology : official journal of the Japanese Urological Association","url":"https://pubmed.ncbi.nlm.nih.gov/11389747","citation_count":23,"is_preprint":false},{"pmid":"10524232","id":"PMC_10524232","title":"Cloning of human cDNAs for Apg-1 and Apg-2, members of the Hsp110 family, and chromosomal assignment of their genes.","date":"1999","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/10524232","citation_count":21,"is_preprint":false},{"pmid":"17588478","id":"PMC_17588478","title":"Identification of an overexpressed gene, HSPA4L, the product of which can provoke prevalent humoral immune responses in leukemia patients.","date":"2007","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/17588478","citation_count":19,"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":"9144406","id":"PMC_9144406","title":"Developmentally regulated expression of APG-1, a member of heat shock protein 110 family in murine male germ cells.","date":"1997","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9144406","citation_count":15,"is_preprint":false},{"pmid":"36012584","id":"PMC_36012584","title":"Expression of TXNRD1, HSPA4L and ATP1B1 Genes Associated with the Freezability of Boar Sperm.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36012584","citation_count":13,"is_preprint":false},{"pmid":"23909438","id":"PMC_23909438","title":"Nogo-A couples with Apg-1 through interaction and co-ordinate expression under hypoxic and oxidative stress.","date":"2013","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/23909438","citation_count":13,"is_preprint":false},{"pmid":"31899217","id":"PMC_31899217","title":"Role of Apg-1 in HSF1 activation and bortezomib sensitivity in myeloma cells.","date":"2019","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/31899217","citation_count":3,"is_preprint":false},{"pmid":"35237814","id":"PMC_35237814","title":"Novel function of the C-terminal region of the Hsp110 family member Osp94 in unfolded protein refolding.","date":"2022","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/35237814","citation_count":3,"is_preprint":false},{"pmid":"28598115","id":"PMC_28598115","title":"[Expression of miR-429 and Its Target Gene HSPA4L in Sperms from Asthenospermia Patients].","date":"2016","source":"Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition","url":"https://pubmed.ncbi.nlm.nih.gov/28598115","citation_count":3,"is_preprint":false},{"pmid":"19169850","id":"PMC_19169850","title":"Molecular cloning of OSP94: A significant biomarker protein of hypertensive human heart and a member of HSP110 family.","date":"2009","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/19169850","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.12.09.627449","title":"Mammalian heat shock protein A4 family ortholog  <i>Hsc70Cb</i>  is required for two phases of spermatogenesis in  <i>D. melanogaster</i>","date":"2024-12-12","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.09.627449","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11586,"output_tokens":3300,"usd":0.042129,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10736,"output_tokens":3217,"usd":0.067053,"stage2_stop_reason":"end_turn"},"total_usd":0.109182,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"Osp94 (HSPA4L) was identified as a new member of the Hsp110/SSE gene subfamily with a putative N-terminal ATP-binding domain and a putative C-terminal peptide-binding domain, consistent with molecular chaperone function. In vitro translated Osp94 migrated as a 105-110 kDa protein on SDS-PAGE.\",\n      \"method\": \"cDNA cloning, domain analysis, in vitro translation/SDS-PAGE\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain identification by sequence analysis confirmed by in vitro translation; single lab but multiple methods\",\n      \"pmids\": [\"8647834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Osp94 (HSPA4L) mRNA expression is up-regulated in renal inner medullary collecting duct cells (mIMCD3) by hyperosmotic NaCl stress and heat stress, and its expression in mouse kidney parallels the corticomedullary osmolality gradient (highest in inner medulla), increasing further during water restriction.\",\n      \"method\": \"Northern blot analysis, in situ hybridization, osmolality manipulation in mIMCD3 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct induction experiments in cells and tissue, single lab, two orthogonal methods\",\n      \"pmids\": [\"8647834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"APG-1 (HSPA4L) mRNA is constitutively and developmentally expressed in testicular germ cells (spermatocytes and spermatids) but is not heat-inducible in germ cells, in contrast to somatic cells where it is induced by a 32°C-to-39°C temperature shift. Heat shock factor 1 (HSF1) binds to heat shock elements in the 5'-flanking region of the apg-1 gene, driving transcriptional activation in somatic cells.\",\n      \"method\": \"Northern blot, in situ hybridization, nuclear run-on assay, gel mobility shift assay, W/Wv mutant testis analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (nuclear run-on, EMSA, in situ hybridization, mutant mouse model) in single rigorous study; replicated by Kaneko et al. 1997 BBRC\",\n      \"pmids\": [\"9006898\", \"9144406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The 5'-flanking region of the Osp94 (HSPA4L) gene contains a tonicity-response element (Osp94-TonE; 5'-TGGAAAGGACCAG-3') distinct from the heat shock element (HSE). TonEBP binds to this element under hypertonic stress. MAPK pathways (p38, ERK, JNK) and the proteasome system are required for hypertonic NaCl-induced Osp94 expression.\",\n      \"method\": \"Luciferase reporter assay, electrophoretic gel mobility-shift assay (EMSA), pharmacological inhibitors (SB203580, PD98059, U0126, SP600125, MG132) in mIMCD3 cells\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA directly demonstrated TonEBP binding; luciferase reporters and multiple specific inhibitors used; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"15018608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Hspa4l-deficient (knockout) male mice show ~42% infertility with drastically reduced sperm count and motility due to increased germ cell apoptosis from late pachytene spermatocytes through postmeiotic spermatids. HSPA4L protein is highly expressed in spermatogenic cells and is required for normal spermatogenesis. Additionally, Hspa4l-null mice display increased susceptibility to osmotic stress and 12% develop hydronephrosis.\",\n      \"method\": \"Gene targeting (knockout mouse), histology, TUNEL apoptosis assay, sperm count and motility analysis, immunohistochemistry, Western blot\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — defined KO mouse with specific cellular phenotype (apoptosis assay, sperm count), multiple orthogonal methods; foundational loss-of-function study\",\n      \"pmids\": [\"16923965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HSPA4L (Apg-1) physically interacts with Nogo-A (RTN4-A) through Nogo-A's central NiG domain. The interaction is selective: Apg-1 does not bind RTN1-A (closest Nogo-A paralogue), and Nogo-A does not bind Apg-2 or Hsp105 (other Hsp110 family members). Under hypoxic stress, both Nogo-A and Apg-1 are co-upregulated in hippocampal neurons; oxidative stress (H2O2) reduces both.\",\n      \"method\": \"Affinity precipitation, co-immunoprecipitation, proximity ligation assay in primary hippocampal neurons from Nogo-deficient mice\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and proximity ligation assay confirming interaction; single lab with three orthogonal binding methods\",\n      \"pmids\": [\"23909438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HSPA4L and HSPA4 act as functionally redundant cochaperones in embryonic lung maturation. Hspa4l(-/-)Hspa4(-/-) double-knockout mice show pulmonary hypoplasia with mesenchymal hypercellularity (increased proliferation, decreased apoptosis), elevated Bcl-2, impaired type I/II pneumocyte maturation (reduced surfactant protein B, pro-SPC, AQP5), and accumulation of ubiquitinated proteins indicating impaired chaperone activity.\",\n      \"method\": \"Double-knockout mouse generation, histology, immunohistochemistry, proliferation/apoptosis assays, Western blot for ubiquitinated proteins and chaperone substrates\",\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 cellular readouts and ubiquitin accumulation as direct chaperone activity measure; single lab but highly rigorous\",\n      \"pmids\": [\"23980576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Apg-1 (HSPA4L) protein is upregulated by bortezomib in multiple myeloma cells via HSF1 nuclear translocation. Silencing Apg-1 sensitizes myeloma cells to bortezomib, as evidenced by increased cleaved caspase-3 and PARP cleavage, indicating Apg-1 promotes cell survival downstream of HSF1 activation under proteasome stress.\",\n      \"method\": \"shRNA knockdown, Western blot (Apg-1, cleaved caspase-3, PARP), HSF1 nuclear translocation assay, triptolide pharmacological inhibition, co-culture with bone marrow stromal cells\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined apoptotic phenotype and pathway placement (HSF1→Apg-1→caspase-3); single lab, multiple methods\",\n      \"pmids\": [\"31899217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Osp94 (HSPA4L) functions as a holdase that suppresses heat-induced aggregation of luciferase and enables its refolding. The SBDβ and H domains (C-terminal region) are critical for protein disaggregation and refolding in reticulocyte lysate with Hsc70/Hsp40. The C-terminal LH domain plays a PA28α-like role in refolding Hsp90-bound denatured substrate, and a chimeric protein replacing the H domain with PA28α retains this activity. Refolding of heat-inactivated luciferase requires collaboration between Osp94, Hsc70, Hsp40, and the reticulocyte lysate chaperone machinery.\",\n      \"method\": \"In vitro aggregation suppression assay, luciferase reactivation assay, targeted deletion mutagenesis of C-terminal domains, biotin-tag cross-linking, chimeric protein construction, rabbit reticulocyte lysate complementation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of chaperone activity combined with mutagenesis and domain-swap experiments in single rigorous study; multiple orthogonal biochemical approaches\",\n      \"pmids\": [\"35237814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"miR-429 directly targets the 3'UTR of HSPA4L mRNA, suppressing HSPA4L mRNA and protein expression. In sperms from asthenospermia patients, miR-429 is upregulated and HSPA4L is correspondingly downregulated, with an inverse correlation between miR-429 and HSPA4L mRNA levels.\",\n      \"method\": \"Luciferase reporter assay with HSPA4L 3'UTR, transfection study, bioinformatics (TargetScan), qRT-PCR, Western blot\",\n      \"journal\": \"Sichuan da xue xue bao. Yi xue ban\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter directly confirmed miR-429 targeting of HSPA4L 3'UTR; single lab with orthogonal validation in clinical samples\",\n      \"pmids\": [\"28598115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Human HSPA4L cDNA introduced into Drosophila Hsc70Cb-knockdown (HSPA4/HSPA4L ortholog) testes partially rescues germ cell progression to spermatocyte stage before apoptosis, demonstrating functional conservation of HSPA4L in supporting male germ cell development across species.\",\n      \"method\": \"RNAi knockdown in Drosophila male germline, transgenic rescue with human HSPA4L cDNA, histology, Nanos-Gal4 driver system\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic rescue experiment with human cDNA demonstrating functional conservation; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2024.12.09.627449\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"HSPA4L (Osp94/APG-1/HSPH3) is a member of the Hsp110/SSE chaperone subfamily that functions as a holdase and disaggregase: its C-terminal SBDβ and H domains suppress protein aggregation and enable Hsc70/Hsp40-assisted refolding of denatured substrates via a PA28α-like mechanism; it acts as a cochaperone redundantly with HSPA4 during embryonic lung maturation (loss of both causes ubiquitinated protein accumulation); it is transcriptionally regulated by TonEBP via a distinct tonicity-response element (Osp94-TonE) and by HSF1 via heat shock elements, with MAPK pathways and the proteasome required for hypertonic induction; it physically interacts with Nogo-A selectively among Hsp110 family members; it is essential for normal spermatogenesis (KO mice show germ cell apoptosis and male infertility) and is regulated post-transcriptionally in sperm by miR-429; and it promotes survival of myeloma cells under proteasome stress downstream of HSF1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HSPA4L (Osp94/APG-1) is an Hsp110/SSE-subfamily molecular chaperone that prevents protein aggregation and promotes refolding of denatured substrates, supporting proteostasis under thermal, osmotic, and proteasome stress [#0, #8]. Biochemically it acts as a holdase: it suppresses heat-induced aggregation of luciferase and, through its C-terminal SBD\\u03b2 and H domains, enables disaggregation and Hsc70/Hsp40-assisted refolding, with the LH domain playing a PA28\\u03b1-like role that a PA28\\u03b1 domain-swap can substitute for [#8]. The gene is transcriptionally driven by two distinct programs: HSF1 binding to heat shock elements in somatic cells [#2], and TonEBP binding to a dedicated tonicity-response element (Osp94-TonE) during hypertonic stress, which additionally requires MAPK signaling and the proteasome [#3]. Genetically, HSPA4L is essential for spermatogenesis\\u2014knockout males are infertile with germ-cell apoptosis [#4]\\u2014and acts redundantly with HSPA4 in embryonic lung maturation, where double loss causes accumulation of ubiquitinated proteins reflecting failed chaperone activity [#6]. It physically interacts selectively with Nogo-A among Hsp110 members [#5], is post-transcriptionally repressed by miR-429 [#9], and promotes myeloma cell survival downstream of HSF1 under proteasome stress [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established HSPA4L's identity as an Hsp110/SSE chaperone and linked it to osmotic stress, framing it as a stress-inducible proteostasis factor in the renal medulla.\",\n      \"evidence\": \"cDNA cloning and domain analysis with in vitro translation; Northern blot and in situ hybridization under hyperosmotic and heat stress in mIMCD3 cells and kidney\",\n      \"pmids\": [\"8647834\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Chaperone activity inferred from domain architecture, not demonstrated\", \"No substrate identified at this stage\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Revealed cell-type-specific transcriptional control, showing HSF1 drives heat-inducible expression in somatic cells while germ cells express HSPA4L constitutively and non-inducibly.\",\n      \"evidence\": \"Nuclear run-on, EMSA, in situ hybridization, and W/Wv mutant testis analysis\",\n      \"pmids\": [\"9006898\", \"9144406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role in germ cells not yet tested by loss-of-function\", \"Mechanism of germ-cell-specific non-inducibility unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined a second, tonicity-specific promoter element and its trans-acting factor, distinguishing osmotic from heat-shock induction of HSPA4L.\",\n      \"evidence\": \"Luciferase reporters, EMSA showing TonEBP binding to Osp94-TonE, and pharmacological inhibition of MAPK/proteasome in mIMCD3 cells\",\n      \"pmids\": [\"15018608\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking proteasome activity to transcriptional induction unclear\", \"In vivo relevance of TonE element not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Provided the first in vivo loss-of-function evidence that HSPA4L is required for spermatogenesis and protects against osmotic stress.\",\n      \"evidence\": \"Hspa4l knockout mouse with histology, TUNEL, sperm count/motility, and immunohistochemistry\",\n      \"pmids\": [\"16923965\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular chaperone substrates in germ cells not identified\", \"Partial (~42%) infertility implies compensation that was uncharacterized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a selective physical partner, distinguishing HSPA4L from other Hsp110 members and linking it to neuronal stress responses.\",\n      \"evidence\": \"Affinity precipitation, reciprocal co-immunoprecipitation, and proximity ligation assay in primary hippocampal neurons\",\n      \"pmids\": [\"23909438\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the Nogo-A interaction not established\", \"Whether HSPA4L chaperones Nogo-A unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated genetic redundancy with HSPA4 and directly tied HSPA4L to clearance of ubiquitinated proteins in a developmental context.\",\n      \"evidence\": \"Hspa4l/Hspa4 double-knockout mice with histology, proliferation/apoptosis assays, and Western blot for ubiquitinated proteins and surfactant markers\",\n      \"pmids\": [\"23980576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific substrates accumulating in lung not identified\", \"Division of labor between HSPA4 and HSPA4L not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established a post-transcriptional repression mechanism connecting miR-429 dysregulation to reduced HSPA4L in human asthenospermia.\",\n      \"evidence\": \"Luciferase reporter of HSPA4L 3'UTR, transfection, qRT-PCR, and Western blot in patient sperm samples\",\n      \"pmids\": [\"28598115\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of miR-429/HSPA4L axis to human infertility not proven\", \"Correlative clinical data only\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed HSPA4L downstream of HSF1 as a pro-survival effector under proteasome stress in cancer cells.\",\n      \"evidence\": \"shRNA knockdown with bortezomib, cleaved caspase-3/PARP Western blots, HSF1 nuclear translocation, and triptolide inhibition in multiple myeloma cells\",\n      \"pmids\": [\"31899217\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrates protecting myeloma cells not identified\", \"Single cell-context; generality across tumors untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the biochemical mechanism, defining HSPA4L as a holdase/disaggregase and mapping the C-terminal domains responsible for refolding via a PA28\\u03b1-like activity.\",\n      \"evidence\": \"In vitro aggregation suppression and luciferase reactivation assays with domain-deletion and PA28\\u03b1 chimera mutants in reticulocyte lysate with Hsc70/Hsp40\",\n      \"pmids\": [\"35237814\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates in vivo not identified\", \"Structural basis of the PA28\\u03b1-like H-domain function not solved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated cross-species functional conservation of HSPA4L in supporting male germ cell development.\",\n      \"evidence\": \"Transgenic rescue of Drosophila Hsc70Cb knockdown testes with human HSPA4L cDNA (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.12.09.627449\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only partial rescue achieved\", \"Preprint, single lab; mechanism of germ-cell support not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The endogenous physiological substrates of HSPA4L in germ cells, lung, and tumor cells remain unidentified, leaving the link between its in vitro holdase activity and specific in vivo phenotypes incomplete.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo substrate repertoire defined\", \"No high-resolution structure of the chaperone in complex with substrate\", \"Mechanism of selective Nogo-A binding unexplained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [8, 6]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HSPA4\", \"RTN4\", \"HSC70\", \"HSP40\", \"HSF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}