{"gene":"HSPA9","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":1994,"finding":"PBP74/HSPA9 is a mitochondrial protein that is imported into the mitochondrial matrix in a membrane potential- and ATP-dependent manner; the N-terminal 46-amino acid presequence is required for mitochondrial targeting, and deletion of this presequence results in cytosolic localization.","method":"Confocal immunofluorescence, epitope-tagging, cell fractionation, in vitro import into isolated yeast mitochondria, mitochondrial subfractionation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biochemical and cell biological methods in one study, including in vitro reconstitution of import and mutagenesis of targeting sequence","pmids":["7865888"],"is_preprint":false},{"year":1998,"finding":"Mot-2 (HSPA9) binds to and inactivates the tumor suppressor p53 by sequestering it in the cytoplasm, preventing its nuclear translocation; mot-2 but not mot-1 represses p53-mediated transactivation and down-regulates p53-responsive genes p21(WAF-1) and mdm-2.","method":"Co-localization by immunofluorescence, p53-responsive reporter assays, Western blot of p53 target genes, GFP-tagged mot-2 nuclear translocation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal functional assays (reporter, target gene expression, localization) replicated across subsequent studies","pmids":["9792667"],"is_preprint":false},{"year":2000,"finding":"MKT-077 binds to mortalin/mot-2 (HSPA9) and abrogates its interaction with p53, releasing cytoplasmically sequestered wild-type p53 and restoring its transcriptional activation function in cancer cells.","method":"Binding assay, co-immunoprecipitation, p53 transcriptional reporter assay, immunofluorescence","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding demonstrated, functional rescue of p53 activity shown, replicated in multiple subsequent studies","pmids":["11156371"],"is_preprint":false},{"year":2000,"finding":"Mortalin/HSPA9 is present not only in mitochondria but also in the endoplasmic reticulum fraction; in certain immortal cell lines it additionally localizes to an extra-organelle cytosolic pool.","method":"Subcellular fractionation, immunofluorescence microscopy","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (fractionation + immunofluorescence), single lab","pmids":["10944461"],"is_preprint":false},{"year":2001,"finding":"The p53-binding domain of mot-2/HSPA9 was mapped in vitro to its N-terminal amino acid residues 253–282; this region overlaps with the MKT-077-binding region, suggesting MKT-077 restores p53 function by competing with p53 for the same binding site on mot-2.","method":"In vitro binding assay with His-tagged deletion mutants, peptide competition assay","journal":"Neoplasia","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with deletion mutants, single lab","pmids":["11420746"],"is_preprint":false},{"year":2001,"finding":"Mortalin/GRP75 (HSPA9) physically interacts with GRP94 (an Hsp90-family ER protein); interacting domains were mapped by mutational analysis using far-Western screening, yeast two-hybrid, and co-immunoprecipitation.","method":"Far-Western screening, in vivo reporter assay, co-immunoprecipitation, mutational analysis","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — three orthogonal methods (far-Western, reporter, CoIP) plus domain mapping, single lab","pmids":["11439088"],"is_preprint":false},{"year":2002,"finding":"The mot-2/HSPA9 binding site on p53 was mapped by in vivo co-immunoprecipitation to the C-terminal residues 312–352, which includes p53's cytoplasmic sequestration domain, demonstrating the mechanism by which mot-2 retains p53 in the cytoplasm.","method":"In vivo co-immunoprecipitation of mot-2 with p53 deletion mutants","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct domain mapping by co-IP with deletion mutants, single lab, consistent with parallel in vitro study","pmids":["11900485"],"is_preprint":false},{"year":2002,"finding":"VDAC1 physically interacts with PBP74/GRP75/HSPA9 in vivo (yeast two-hybrid) and in vitro (overlay assay with recombinant proteins); GRP75 co-localizes with VDAC1 in HeLa cells and modulates VDAC1 electrophysiological properties, drastically reducing its voltage-dependence in planar lipid bilayer experiments.","method":"Sos recruitment system yeast two-hybrid, overlay assay with recombinant proteins, immunofluorescence co-localization, planar lipid bilayer electrophysiology","journal":"The international journal of biochemistry & cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro reconstitution with recombinant proteins plus functional electrophysiology, multiple orthogonal methods","pmids":["12009301"],"is_preprint":false},{"year":1999,"finding":"GRP75/mortalin (HSPA9) is a direct intracellular binding partner of fibroblast growth factor-1 (FGF-1); the interaction was identified by affinity purification, confirmed by co-immunoprecipitation, immunohistochemical co-localization, yeast two-hybrid, and direct in vitro binding with recombinant proteins.","method":"Affinity adsorption/purification, co-immunoprecipitation, immunohistochemical co-localization, yeast two-hybrid, in vitro binding assay with recombinant proteins","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — five orthogonal methods including in vitro reconstitution with recombinant proteins, single lab","pmids":["10510314"],"is_preprint":false},{"year":2005,"finding":"Loss-of-function mutation of HSPA9B within the substrate-binding domain in zebrafish (crimsonless mutant) causes MDS-like ineffective hematopoiesis including anemia, dysplasia, increased apoptosis, and multilineage cytopenia, by compromising mitochondrial function and inducing oxidative stress specifically in blood cells.","method":"Positional cloning, rescue experiment, morpholino knockdown in zebrafish","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — positional cloning plus rescue and morpholino knockdown, three converging genetic approaches in a vertebrate model","pmids":["15650063"],"is_preprint":false},{"year":2005,"finding":"Mortalin/GRP75 binds complement C8 and C9, promotes shedding of membrane vesicles loaded with complement MAC, and protects cells from complement-mediated lysis; anti-mortalin antibodies reduced vesicle release and elevated complement-mediated cell death.","method":"Mass spectrometry identification, Western blot, vesiculation assay, antibody blocking","journal":"International immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional blocking antibody experiments plus vesicle isolation, single lab","pmids":["16091382"],"is_preprint":false},{"year":2010,"finding":"GRP75/HSPA9 is a functional constituent of noncaveolar, membrane raft-associated endocytic vesicles; RNAi-mediated knockdown of GRP75 and GRP75-blocking antibodies inhibit HSPG-mediated macromolecular endocytosis, and this pathway requires the RhoA GTPase family member CDC42.","method":"Antibody-conjugated magnetic nanoparticle vesicle isolation, RNAi knockdown, antibody blocking, co-localization, CDC42 involvement assessed","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional vesicle isolation plus RNAi and antibody blocking, single lab, two orthogonal inhibition approaches","pmids":["20624969"],"is_preprint":false},{"year":2011,"finding":"GRP75/HSPA9 overexpression suppresses apoptosis during glucose deprivation by inhibiting Bax conformational change through activation of AKT via a PI3K-independent, Raf/MEK/ERK-dependent pathway.","method":"Pharmacological inhibitors (LY294002, U0126), Western blot of pAKT and Bax conformational change, PC12 cell glucose deprivation model","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal inhibitor experiments dissecting pathway, single lab, functional readout of Bax conformational change","pmids":["21964438"],"is_preprint":false},{"year":2011,"finding":"HSPA9 knockdown in primary human CD34+ hematopoietic progenitor cells leads to increased TP53 expression and nuclear TP53 accumulation; HSPA9 protein interacts with TP53 in CD34+ cells, and concurrent knockdown of TP53 rescues the increased apoptosis caused by HSPA9 knockdown.","method":"Lentiviral shRNA knockdown, co-immunoprecipitation, nuclear/cytoplasmic fractionation, genetic epistasis (double knockdown rescue)","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus epistasis rescue, two orthogonal methods, functionally links HSPA9-TP53 interaction to apoptosis regulation","pmids":["28178280"],"is_preprint":false},{"year":2013,"finding":"Mortalin/HSPA9 is present in the MEK1/MEK2 proteome and acts as a negative regulator of Raf/MEK/ERK signaling; mortalin depletion increases MEK/ERK activity and MEK/ERK-dependent p21(CIP1) transcription, while mortalin overexpression suppresses B-Raf(V600E)-induced MEK/ERK activation and cell cycle arrest.","method":"Proteomics (MEK1/2 interactome), shRNA depletion, Western blot, reporter assays in multiple cancer cell lines","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics plus functional KD/OE experiments, single lab, multiple cell lines tested","pmids":["23959801"],"is_preprint":false},{"year":2014,"finding":"Mortalin/GRP75 binds complement C9 (and C8) through its N-terminal ATPase domain (not the substrate-binding domain), via an ionic, nucleotide-sensitive interaction; the ATPase domain inhibits zinc-induced C9 polymerization; overexpression of mortalin confers resistance to CDC while knockdown increases sensitivity; cytosolic mortalin (lacking mitochondrial targeting) has reduced protective capacity.","method":"Co-immunoprecipitation, recombinant domain expression (ATPase vs. substrate-binding domain), C9 polymerization inhibition assay, mortalinΔ51-EGFP localization and CDC assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — recombinant domain dissection, in vitro functional assay (C9 polymerization), multiple cell-based functional experiments in one study","pmids":["24719326"],"is_preprint":false},{"year":2015,"finding":"HSPA9 functions in mitochondrial iron-sulfur cluster (ISC) biogenesis; HSPA9 physically interacts with and stabilizes the ISC biogenesis proteins frataxin, Nfs1, ISCU, and Nfu; HSPA9 depletion decreases aconitase activity (ISC-requiring) but not malate dehydrogenase activity, increases IRP1 binding, and inhibits erythroid differentiation by post-transcriptionally reducing Alas2 and FeCH expression through the IRP/IRE pathway.","method":"Co-immunoprecipitation, aconitase activity assay, IRP1 binding assay, RNAi knockdown, erythroid differentiation assay, rescue with Alas2 ORF","journal":"Mitochondrion","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biochemical and genetic approaches in one study, including direct interaction, enzymatic assay, and genetic rescue","pmids":["26702583"],"is_preprint":false},{"year":2015,"finding":"Biallelic mutations in HSPA9 cause EVEN-PLUS syndrome, a human disease featuring epiphyseal, vertebral, ear, nose, and other malformations, establishing HSPA9 as essential for mitochondrial protein import/folding and human embryonic morphogenesis.","method":"Whole-exome/genome sequencing in affected families, genetic analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — human genetics (biallelic mutations) in two families, no in vitro functional reconstitution but strong genetic evidence","pmids":["26598328"],"is_preprint":false},{"year":2015,"finding":"Mutations in HSPA9 (a mitochondrial HSP70 involved in mitochondrial Fe-S cluster biogenesis) cause congenital sideroblastic anemia inherited as an autosomal recessive trait; haploinsufficiency can be expressed clinically when a common hypomorphic SNP is present in trans.","method":"Genetic sequencing of affected families, functional genetic analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — human genetics with functional pathway context (Fe-S biogenesis), replicated across multiple families","pmids":["26491070"],"is_preprint":false},{"year":2017,"finding":"Mortalin/HSPA9 facilitates PP1α-mediated dephosphorylation of MEK1/2 by promoting the PP1α-MEK1/2 physical interaction in an ATP-sensitive manner; the region Val482–Glu491 in mortalin's substrate-binding cavity and substrate lid is required for these interactions, consistent with canonical HSP70-client interaction mechanisms.","method":"Co-immunoprecipitation, in vitro binding assay, PP1α inhibitor experiments, mortalin domain mutant analysis, Western blot of phospho-MEK1/2","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding with domain mapping plus cell-based epistasis, multiple orthogonal methods in one study","pmids":["28674184"],"is_preprint":false},{"year":2018,"finding":"TG2 (transglutaminase type 2) interacts with GRP75/HSPA9 at mitochondria-associated membranes (MAMs); absence of the TG2-GRP75 interaction increases IP3R-3–GRP75 interaction, decreases ER-mitochondria contact sites, impairs ER-to-mitochondria Ca2+ flux, and alters the MAM proteome.","method":"Co-immunoprecipitation (TG2 interactome), proximity ligation assay, TEM quantification of ER-mitochondria contacts, Ca2+ flux measurement, MAM proteomics","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (CoIP, PLA, TEM, Ca2+ flux, proteomics) in one study establishing GRP75 role at MAMs","pmids":["30590033"],"is_preprint":false},{"year":2019,"finding":"GRP75/HSPA9 directly interacts with frataxin both in vivo in mouse cortex and in vitro in cortical neurons; GRP75 overexpression increases frataxin levels and stabilizes clinically relevant missense frataxin variants; clinical GRP75 variants (R126W, A476T, P509S) impair GRP75-frataxin binding; GRP75 physically interacts with mitochondrial processing peptidase (MPP), potentially facilitating frataxin processing.","method":"Co-immunoprecipitation in vivo and in vitro, GRP75 overexpression/variant rescue experiments in FRDA patient-derived cells, mitochondrial network and ATP level assays","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding in vivo and in vitro, mutagenesis of clinical variants, functional rescue, multiple orthogonal methods","pmids":["30590615"],"is_preprint":false},{"year":2020,"finding":"Mortalin/HSPA9 identifies adenine nucleotide translocase 3 (ANT3) as a substrate; mortalin inhibits ANT3-CypD interaction to reduce mitochondrial membrane permeability; in BRAF(V600E) cells, mortalin depletion increases mitochondrial permeability (via ANT3-CypD interaction) to a lethal extent, while MEK-ERK activity opposes mortalin by promoting ANT3-CypD interaction.","method":"Proteomics screening, co-immunoprecipitation, ANT3/CypD/MCU knockdown and inhibitor rescue, mitochondrial membrane permeability assay, xenograft in vivo model","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomics identification of substrate, multiple genetic/pharmacological epistasis experiments, in vivo validation","pmids":["32156782"],"is_preprint":false},{"year":2020,"finding":"Mortalin/HSPA9 depletion selectively kills KRAS-mutant cells through a mitochondria-originated death mechanism involving ANT, CypD, and MCU; this cell death occurs independently of TP53 and p21CIP1 and is phenocopied by HSP70 inhibitor JG-98.","method":"Genetic knockdown, ANT/CypD/MCU inhibitor/knockdown rescue, xenograft in vivo model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic epistasis, in vivo validation, single lab","pmids":["32291414"],"is_preprint":false},{"year":2021,"finding":"GRP75/HSPA9 forms the IP3R-GRP75-VDAC1 complex that mediates Ca2+ transfer from the ER to mitochondria; α-synuclein overexpression impairs the GRP75-IP3R interaction (but not VDAC1-GRP75 interaction) at MAMs, reducing ER-mitochondria contact sites and mitochondrial Ca2+ buffering.","method":"Co-immunoprecipitation, proximity ligation assay, mitochondrial Ca2+ imaging, ER-mitochondria contact site quantification","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus PLA plus Ca2+ imaging, single lab","pmids":["34510532"],"is_preprint":false},{"year":2021,"finding":"GRP75/HSPA9 serves as a scaffold to recruit deubiquitinating enzyme USP1 to inhibit K48-linked polyubiquitination of SIX1, thereby stabilizing SIX1 protein; the C-terminal peptide-binding domain of GRP75 (residues 433–679) is required for GRP75-USP1-SIX1 complex formation.","method":"Co-immunoprecipitation, ubiquitination assay, GRP75 domain deletion analysis, xenograft mouse model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus ubiquitination assay plus domain mapping, single lab, in vivo validation","pmids":["34079090"],"is_preprint":false},{"year":2021,"finding":"GRP75/HSPA9 palmitate-induced increase in pancreatic β-cells increases ER-mitochondria physical coupling and mitochondrial Ca2+ transfer leading to apoptosis; GRP75 overexpression alone is sufficient to impair mitochondrial membrane potential, increase mitochondrial Ca2+, and induce apoptosis; GRP75 inhibition prevents palmitate-induced aberrations.","method":"GRP75 overexpression/knockdown, mitochondrial Ca2+ measurement, mitochondrial membrane potential assay, ROS assay, TEM for ER-mitochondria contacts, in vivo palmitate injection model","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with multiple orthogonal readouts, in vivo confirmation, single lab","pmids":["34756890"],"is_preprint":false},{"year":2021,"finding":"HSPA9/mortalin down-regulation induces mitochondrial fragmentation and axonal damage in primary neurons, while overexpression confers protection against rotenone-induced axonal degeneration; mortalin modulates mitochondrial morphology by acting on DRP1 phosphorylation.","method":"Lentiviral over-expression and knockdown, microfluidic-based axonal compartment cultures, mitochondrial morphology quantification, DRP1 phosphorylation Western blot","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with specific molecular readout (DRP1 phosphorylation), single lab","pmids":["34489498"],"is_preprint":false},{"year":2022,"finding":"GRP75/HSPA9 regulates mitochondrial supercomplex assembly and stabilization to modulate insulin sensitivity; GRP75 induction prevents high-fat diet-induced obesity and insulin resistance in mice; GRP75 knockdown increases mitochondrial fragmentation, triggers cytosolic mtDNA release, and activates the cGAS/STING-dependent proinflammatory response.","method":"In vivo GRP75 induction mouse model (HFD), GRP75 knockdown, mitochondrial supercomplex analysis, respiratory chain complex activity assay, cGAS/STING activation assay","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro gain/loss-of-function with mechanistic readouts, single lab","pmids":["34810178"],"is_preprint":false},{"year":2022,"finding":"The IP3R1-GRP75-VDAC1 complex mediates ER stress-mitochondrial oxidative stress and Ca2+ transfer in diabetic atrial remodeling; GRP75 conditional cardiac knockout impairs calcium transport from ER to mitochondria and attenuates atrial remodeling and AF progression.","method":"siRNA silencing, conditional knockout mouse (Myh6-Cre+/Hspa9flox/flox), proximity ligation assay, Ca2+ imaging, in situ PLA","journal":"Redox biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic conditional KO plus siRNA plus PLA and Ca2+ flux measurements, multiple orthogonal approaches, in vivo validation","pmids":["35344886"],"is_preprint":false},{"year":2011,"finding":"DNLZ/HEP stimulates HSPA9 ATPase activity through a conserved histidine (H107) residue; DNLZ-H107A fails to stimulate HSPA9 catalytic activity even at concentrations 10-fold above the half-maximal effective concentration, while retaining reduced binding to nucleotide-free HSPA9.","method":"Alanine mutagenesis scan, ATPase activity measurement, tryptophan fluorescence binding assay, E. coli co-expression solubility assay","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with in vitro enzymatic assay, specific critical residue identified","pmids":["21530495"],"is_preprint":false},{"year":2011,"finding":"Nuclear GRP75/HSPA9 physically interacts with retinoic acid receptors RARα and RXRα in neuroblastoma cells upon RA treatment; GRP75 is required for RARα/RXRα-mediated transcriptional regulation and reduces proteasome-mediated degradation of RARα/RXRα in a RA-dependent manner.","method":"Co-immunoprecipitation, transcriptional reporter assay, proteasome inhibitor experiments, immunofluorescence nuclear localization, in vivo xenograft","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus functional reporter and degradation assays, single lab","pmids":["22022577"],"is_preprint":false},{"year":2016,"finding":"Complement activation triggers redistribution of mortalin/GRP75 from mitochondria to the plasma membrane within minutes; cytoplasmic mortalin levels increase in complement-treated cells, as shown by immunoblotting and STED nanoscopy showing juxtaposition of mortalin and C5b-9 at the plasma membrane.","method":"STED super-resolution microscopy, immunoblotting of cytoplasmic fraction, complement treatment kinetics","journal":"Immunobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — STED nanoscopy plus biochemical fractionation, single lab, two orthogonal methods","pmids":["27475989"],"is_preprint":false},{"year":2016,"finding":"GRP75/HSPA9 upregulates clathrin-independent endocytosis (CIE) and inhibits clathrin-mediated endocytosis (CME) through its mitochondria-localized ATPase domain; this regulation is mediated by concurrent activation of Cdc42 and RhoA, inducing stress fibers and filopodia; silencing either Cdc42 or RhoA impairs GRP75-driven CIE enhancement.","method":"Mitochondrial signal peptide-directed expression constructs, endocytosis functional assays (transferrin/CTB uptake), Rho GTPase activity assay, siRNA silencing of Cdc42/RhoA, actin cytoskeleton imaging","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain targeting experiments plus genetic epistasis (Cdc42/RhoA silencing), single lab, multiple orthogonal readouts","pmids":["27090015"],"is_preprint":false},{"year":2018,"finding":"GRP75/HSPA9 is associated with proto-Dbl inside cells and promotes proto-Dbl degradation through the CHIP-mediated ubiquitin-proteasome pathway, acting as a cooperator with CHIP and competitor to Hsc70/Hsp90 in the chaperone-assisted degradation machinery.","method":"Co-immunoprecipitation, endocytosis assays (macropinocytosis, CME, CIE), siRNA knockdown, GRP75 inhibitor MKT-077, Rho GTPase activation assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus functional endocytosis and degradation assays, single lab","pmids":["30250167"],"is_preprint":false},{"year":2018,"finding":"Hsp90 directly binds mortalin/GRP75; geldanamycin-mediated Hsp90 inhibition failed to sensitize cells with knocked-down mortalin to complement-dependent cytotoxicity, establishing mortalin as epistatic to Hsp90 in CDC resistance.","method":"Co-immunoprecipitation of Hsp90 with mortalin in cell extracts and with purified recombinant proteins, genetic epistasis (Hsp90 inhibitor in mortalin-KD cells), CDC assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding with recombinant proteins plus genetic epistasis, single lab","pmids":["29396434"],"is_preprint":false},{"year":2020,"finding":"Grp75/HSPA9 mediates mitochondrial import of DJ-1; resveratrol enhances Grp75-DJ-1 interaction and promotes DJ-1 translocation to mitochondria; Grp75 knockdown abolishes resveratrol-induced DJ-1 mitochondrial translocation and prevents subsequent preservation of mitochondrial complex I activity.","method":"Co-immunoprecipitation, siRNA knockdown, mitochondrial fractionation, complex I activity assay, ROS measurement","journal":"Journal of cardiovascular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus genetic knockdown epistasis and functional enzymatic readout, single lab","pmids":["32040033"],"is_preprint":false},{"year":2024,"finding":"OMA1 competitively binds HSPA9 to induce mitophagy and GBM immune escape; OMA1-HSPA9 interaction (identified by Co-IP and mass spectrometry) promotes mitochondrial DNA release, activates cGAS-STING, and upregulates PD-L1 transcription.","method":"Co-immunoprecipitation, mass spectrometry, siRNA knockdown, immunofluorescence, immunohistochemistry, Western blot","journal":"Journal for immunotherapy of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus MS plus functional pathway analysis, single lab","pmids":["38604814"],"is_preprint":false},{"year":2024,"finding":"MUL1 SUMOylates HSPA9 at K612, causing HSPA9 export from mitochondria and nuclear interaction with SUZ12 and EZH2; HSPA9 nuclear translocation leads to ubiquitination-mediated degradation of SUZ12 and EZH2 and downstream STAT3 pathway inhibition; mutation of K612 blocks HSPA9 translocation and abolishes MUL1-mediated tumor suppression.","method":"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis (K612), SUMOylation assay, immunofluorescence localization, in vitro and in vivo functional assays","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis plus CoIP and functional rescue, single lab, multiple orthogonal methods","pmids":["39113711"],"is_preprint":false},{"year":2024,"finding":"Under ferroptotic conditions, lipid peroxidation activates cAMP-dependent PKA anchored by AKAP1 at the outer mitochondrial membrane, which phosphorylates GRP75 at S148; phosphorylated GRP75 translocates from mitochondria to MAMs/cytosol, where it competes with Nrf2 for Keap1 binding through a conserved ETGE motif, stabilizing and activating Nrf2 to transcribe antiferroptotic genes.","method":"PKA phosphorylation assay, GRP75 S148A mutagenesis, Keap1 co-immunoprecipitation, Nrf2 target gene reporter, in vivo xenograft ferroptosis model","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-directed mutagenesis plus direct binding assay plus transcriptional reporter plus in vivo validation, multiple orthogonal methods","pmids":["39537840"],"is_preprint":false},{"year":2024,"finding":"Tumor-derived GRP75 binds adenine nucleotide translocase 2 (ANT2) to form a GRP75-ANT2 complex; stabilized ANT2 enhances its interaction with uncoupling protein 1 (UCP1), promoting white adipose tissue browning and cancer-associated cachexia.","method":"Co-immunoprecipitation, GRP75 inhibitor (withanone) treatment, in vivo mouse cachexia models","journal":"Signal transduction and targeted therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus in vivo functional model with inhibitor, single lab","pmids":["39327432"],"is_preprint":false},{"year":2025,"finding":"HSPA9 serves as a scaffold to strengthen the USP14-SLC7A11 interaction, promoting USP14-mediated SLC7A11 deubiquitination and thereby suppressing ferroptosis in multiple myeloma; inhibition of USP14 enhances SLC7A11 ubiquitination and degradation, promoting ferroptosis.","method":"Proteomics screening, co-immunoprecipitation, ubiquitination assay, USP14 inhibitor IU1, xenograft mouse model","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics plus CoIP plus ubiquitination assay and in vivo model, single lab","pmids":["40372919"],"is_preprint":false},{"year":2010,"finding":"Ca2+-induced release of mitochondrial outer membrane-bound m-calpain large subunit requires free calpain small subunit (located in the IMS), Grp75, ATP, and Ca2+; the OM-bound m-calpain large subunit is not associated with the small subunit or Grp75 prior to activation.","method":"DEAE-Sepharose column chromatography of solubilized OM proteins, calpain activity assay, co-immunoprecipitation, immunoblot","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical reconstitution-like fractionation plus co-IP, single lab","pmids":["21145877"],"is_preprint":false},{"year":2022,"finding":"GRP75/HSPA9 mediates ER-mitochondria Ca2+ transfer via the IP3R1-GRP75-VDAC1 axis in retinal vascular endothelial cells under diabetic conditions; elevated mitochondrial Ca2+ leads to increased ROS, decreased mitochondrial membrane potential, cytochrome c release, and caspase-3 activation leading to apoptosis.","method":"siRNA knockdown, proximity ligation assay, Ca2+ imaging, mitochondrial membrane potential assay, ROS assay, in vivo STZ-induced DR rat model","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA loss-of-function with multiple mechanistic readouts plus in vivo validation, single lab","pmids":["36551205"],"is_preprint":false},{"year":2022,"finding":"DAB2IP competitively binds GRP75 through its Ras-GAP domain, reducing GRP75-driven p53 ubiquitination and proteasomal degradation; mass spectrometry identified GRP75 as an interaction partner of both DAB2IP and p53 in this ubiquitin-related complex.","method":"Mass spectrometry profiling, co-immunoprecipitation, ubiquitination assay, DAB2IP domain mapping, in vivo tumor model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS plus CoIP plus ubiquitination assay, single lab","pmids":["35150809"],"is_preprint":false},{"year":2024,"finding":"METTL3-mediated m6A methylation at the HSPA9 mRNA 3'UTR increases mortalin mRNA stability and translation efficiency in cervical cancer cells; exosomal mortalin suppresses cellular senescence and promotes malignant transformation by blocking nuclear transport of p53 and preventing the p53-Gadd45A interaction.","method":"m6A methylation assay (3'UTR), mRNA stability assay, exosome isolation, co-immunoprecipitation (mortalin-p53), p53 nuclear/cytoplasmic fractionation, in vivo xenograft","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m6A biochemistry plus CoIP plus localization, single lab, in vivo validation","pmids":["38253218"],"is_preprint":false},{"year":2021,"finding":"GRP75/HSPA9 inhibits ubiquitination-mediated HMGA1 degradation by directly binding to HMGA1, causing HMGA1 upregulation and activation of JNK/c-JUN signaling in lung adenocarcinoma.","method":"Co-immunoprecipitation, ubiquitination assay, mRNA sequencing, in vitro and in vivo KD/OE experiments","journal":"Thoracic cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP plus ubiquitination assay plus downstream signaling analysis, single lab","pmids":["33755320"],"is_preprint":false}],"current_model":"HSPA9/mortalin/GRP75 is a mitochondrial matrix HSP70 chaperone imported via an N-terminal targeting sequence in a membrane-potential- and ATP-dependent manner; it directly binds and cytoplasmic-sequesters p53 (through p53 residues 312–352 engaging mortalin residues 253–282) to inactivate tumor-suppressive p53 activity, an interaction disrupted by MKT-077; it serves as the central tether of the IP3R-GRP75-VDAC1 complex at mitochondria-associated ER membranes (MAMs) to regulate ER-to-mitochondria Ca2+ transfer and mitochondrial bioenergetics; it supports mitochondrial iron-sulfur cluster biogenesis by stabilizing frataxin, Nfs1, ISCU, and Nfu; it regulates MEK/ERK signaling by facilitating PP1α-mediated MEK1/2 dephosphorylation; it suppresses ANT3-CypD-dependent mitochondrial permeability transition to promote survival in BRAF/KRAS-mutant tumor cells; it scaffolds USP-dependent deubiquitination complexes (e.g., USP1-SIX1, USP14-SLC7A11) to stabilize client proteins; it facilitates mitochondrial import of client proteins such as DJ-1; and under ferroptotic stress it is phosphorylated at S148 by AKAP1-anchored PKA and translocates to MAMs/cytosol to compete with Nrf2 for Keap1 binding, activating antioxidant gene transcription."},"narrative":{"mechanistic_narrative":"HSPA9 (mortalin/GRP75) is a HSP70-family chaperone that is imported into the mitochondrial matrix via a cleavable N-terminal presequence in a membrane-potential- and ATP-dependent manner, with its ATPase cycle stimulated by the co-chaperone DNLZ acting through a conserved histidine [PMID:7865888, PMID:21530495]. Within mitochondria it supports iron-sulfur cluster biogenesis by physically binding and stabilizing frataxin, Nfs1, ISCU, and Nfu, such that its loss reduces aconitase activity and perturbs erythroid heme synthesis through the IRP/IRE axis [PMID:26702583, PMID:30590615]. As a canonical HSP70, it engages client proteins through its substrate-binding cavity to control their stability, signaling, and localization: it facilitates PP1α-mediated dephosphorylation of MEK1/2 to negatively regulate Raf/MEK/ERK signaling [PMID:23959801, PMID:28674184], and it acts on adenine nucleotide translocases—inhibiting ANT3-CypD interaction to suppress mitochondrial permeability transition and promote survival of BRAF- and KRAS-mutant tumor cells [PMID:32156782, PMID:32291414]. A central, well-characterized role is as the tether of the IP3R-GRP75-VDAC1 complex at mitochondria-associated ER membranes (MAMs), where it bridges ER and mitochondria to govern Ca2+ transfer and downstream bioenergetics, oxidative stress, and apoptosis [PMID:12009301, PMID:30590033, PMID:35344886]. Independently of its mitochondrial function, a cytoplasmic pool of mortalin binds the C-terminal cytoplasmic-sequestration domain of p53 (residues 312–352) through mortalin residues 253–282, retaining p53 in the cytoplasm to repress its transcriptional and apoptotic activity; the small molecule MKT-077 competes for this site to release and reactivate p53 [PMID:9792667, PMID:11156371, PMID:11420746, PMID:11900485, PMID:28178280]. Mortalin further serves as a scaffold for deubiquitination complexes (USP1-SIX1, USP14-SLC7A11) and stabilizes diverse clients against ubiquitin-proteasome degradation [PMID:34079090, PMID:40372919]. Under ferroptotic stress, PKA anchored by AKAP1 phosphorylates GRP75 at S148, driving its translocation to MAMs/cytosol where it competes with Nrf2 for Keap1 binding to activate antioxidant transcription [PMID:39537840]. Biallelic HSPA9 mutations cause EVEN-PLUS syndrome and autosomal-recessive congenital sideroblastic anemia, consistent with its essential roles in mitochondrial protein folding and Fe-S cluster biogenesis [PMID:26598328, PMID:26491070].","teleology":[{"year":1994,"claim":"Established where HSPA9 acts and how it gets there, defining it as a mitochondrial matrix protein dependent on an N-terminal targeting sequence.","evidence":"Epitope-tagging, cell fractionation, and in vitro import into isolated mitochondria with presequence deletion","pmids":["7865888"],"confidence":"High","gaps":["Did not address extra-mitochondrial pools later observed","Chaperone substrates within the matrix not yet defined"]},{"year":1998,"claim":"Revealed a non-canonical cytoplasmic function: HSPA9 sequesters p53 to block its nuclear activity, linking the chaperone to tumor suppression control.","evidence":"Immunofluorescence colocalization, p53 reporter assays, and target-gene Western blotting comparing mot-1 vs mot-2","pmids":["9792667"],"confidence":"High","gaps":["Binding interface not mapped at this stage","Mechanism by which a matrix chaperone reaches cytoplasmic p53 unresolved"]},{"year":2001,"claim":"Mapped the p53-binding region on mortalin and showed it overlaps the MKT-077 site, providing a structural rationale for pharmacological p53 reactivation.","evidence":"In vitro binding with His-tagged deletion mutants and peptide competition; MKT-077 binding/rescue assays","pmids":["11420746","11156371"],"confidence":"Medium","gaps":["In vitro mapping only","Single lab"]},{"year":2002,"claim":"Defined both sides of the mortalin-p53 interaction and identified VDAC1 as a direct partner, foreshadowing the MAM tethering role.","evidence":"Co-IP with p53 deletion mutants; yeast two-hybrid, recombinant overlay, and planar lipid bilayer electrophysiology for VDAC1","pmids":["11900485","12009301"],"confidence":"High","gaps":["Functional consequence of VDAC1 modulation in cells not yet established","Link to ER-mitochondria contact sites not yet drawn"]},{"year":2005,"claim":"Connected HSPA9 loss to a vertebrate disease phenotype, implicating mitochondrial dysfunction and oxidative stress in ineffective hematopoiesis.","evidence":"Positional cloning, rescue, and morpholino knockdown in the zebrafish crimsonless mutant","pmids":["15650063"],"confidence":"High","gaps":["Molecular substrate driving the hematopoietic defect not identified at the time","Domain-specific mechanism unresolved"]},{"year":2015,"claim":"Defined a core matrix function in Fe-S cluster biogenesis and tied HSPA9 mutations directly to human Mendelian disease.","evidence":"Co-IP and stabilization of frataxin/Nfs1/ISCU/Nfu plus aconitase and IRP1 assays; exome/genome sequencing of EVEN-PLUS and sideroblastic anemia families","pmids":["26702583","26598328","26491070"],"confidence":"High","gaps":["Genetic disease studies lacked in vitro functional reconstitution","Hierarchy of client stabilization within the ISC machinery not resolved"]},{"year":2017,"claim":"Provided a chaperone-mechanistic basis for MEK/ERK regulation, mapping the substrate-binding region required for facilitating PP1α-MEK1/2 dephosphorylation.","evidence":"Co-IP, in vitro binding, domain-mutant analysis, and PP1α inhibitor experiments","pmids":["28674184","23959801"],"confidence":"High","gaps":["Whether PP1α recruitment occurs at a specific subcellular site not defined","Single lab for the interactome mapping"]},{"year":2020,"claim":"Identified ANT3 as a client and showed mortalin gates mitochondrial permeability transition, explaining a survival dependency in oncogene-mutant tumors.","evidence":"Proteomic substrate screening, ANT3/CypD/MCU knockdown and inhibitor epistasis, permeability assays, and xenografts","pmids":["32156782","32291414"],"confidence":"High","gaps":["Direct structural mode of ANT3 engagement not resolved","Generality across non-BRAF/KRAS contexts unclear"]},{"year":2021,"claim":"Consolidated the IP3R-GRP75-VDAC1 tether as the operative MAM Ca2+ transfer machine and showed disease-relevant regulators perturb it.","evidence":"Co-IP, proximity ligation, Ca2+ imaging, and TEM in TG2-, alpha-synuclein-, and palmitate-context models","pmids":["30590033","34510532","34756890"],"confidence":"High","gaps":["Stoichiometry and dynamics of the tripartite complex not resolved","How GRP75 distinguishes IP3R isoforms unclear"]},{"year":2021,"claim":"Demonstrated a scaffolding role in deubiquitination, mapping the C-terminal peptide-binding domain as required for recruiting USP1 to stabilize clients.","evidence":"Co-IP, ubiquitination assays, GRP75 domain deletions, and xenografts for the GRP75-USP1-SIX1 axis","pmids":["34079090"],"confidence":"Medium","gaps":["Single lab","Whether scaffolding occurs at mitochondria or cytosol not defined"]},{"year":2024,"claim":"Established stress-induced relocalization and post-translational control as switches that redirect HSPA9 from mitochondrial chaperone to nuclear/cytosolic signaling roles.","evidence":"MUL1-mediated K612 SUMOylation with mutagenesis driving nuclear SUZ12/EZH2 degradation; OMA1 competitive binding driving cGAS-STING/PD-L1","pmids":["39113711","38604814"],"confidence":"Medium","gaps":["Single-lab observations","Quantitative fraction of relocalized protein not established"]},{"year":2024,"claim":"Defined a phosphorylation-gated antiferroptotic axis: PKA-mediated S148 phosphorylation redirects GRP75 to compete with Nrf2 for Keap1, activating antioxidant transcription.","evidence":"PKA phosphorylation and S148A mutagenesis, Keap1 co-IP, Nrf2 reporter, and in vivo ferroptosis xenografts","pmids":["39537840","40372919"],"confidence":"High","gaps":["Structural basis of the ETGE-motif competition not resolved","Interplay with mitochondrial functions during ferroptosis unclear"]},{"year":null,"claim":"How a single matrix-imported chaperone is partitioned among its mitochondrial, MAM, cytoplasmic, and nuclear pools to execute distinct functions remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking import, retention, and stress-induced export","Quantitative regulation of pool distribution unknown","Structural understanding of client selectivity lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0,30]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[16,21,19]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[7,20,25,41]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,14,39]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,16,27]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,3,32]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[3,20]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[31,38]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[16,28]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,16,21]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[22,23,39,41]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[14,19,39]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[17,18,9]}],"complexes":["IP3R-GRP75-VDAC1 (MAM Ca2+ transfer complex)"],"partners":["TP53","VDAC1","ITPR1","FXN","MEK1/2","ANT3","KEAP1","USP14"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P38646","full_name":"Stress-70 protein, mitochondrial","aliases":["75 kDa glucose-regulated protein","GRP-75","Heat shock 70 kDa protein 9","Heat shock protein family A member 9","Mortalin","MOT","Peptide-binding protein 74","PBP74"],"length_aa":679,"mass_kda":73.7,"function":"Mitochondrial chaperone that plays a key role in mitochondrial protein import, folding, and assembly. Plays an essential role in the protein quality control system, the correct folding of proteins, the re-folding of misfolded proteins, and the targeting of proteins for subsequent degradation. These processes are achieved through cycles of ATP binding, ATP hydrolysis, and ADP release, mediated by co-chaperones (PubMed:18632665, PubMed:25615450, PubMed:28848044, PubMed:30933555, PubMed:31177526). In mitochondria, it associates with the TIM (translocase of the inner membrane) protein complex to assist in the import and folding of mitochondrial proteins (By similarity). Plays an important role in mitochondrial iron-sulfur cluster (ISC) biogenesis, interacts with and stabilizes ISC cluster assembly proteins FXN, NFU1, NFS1 and ISCU (PubMed:26702583). Regulates erythropoiesis via stabilization of ISC assembly (PubMed:21123823, PubMed:26702583). Regulates mitochondrial calcium-dependent apoptosis by coupling two calcium channels, ITPR1 and VDAC1, at the mitochondria-associated endoplasmic reticulum (ER) membrane to facilitate calcium transport from the ER lumen to the mitochondria intermembrane space, providing calcium for the downstream calcium channel MCU, which releases it into the mitochondrial matrix (By similarity). Although primarily located in the mitochondria, it is also found in other cellular compartments. In the cytosol, it associates with proteins involved in signaling, apoptosis, or senescence. It may play a role in cell cycle regulation via its interaction with and promotion of degradation of TP53 (PubMed:24625977, PubMed:26634371). May play a role in the control of cell proliferation and cellular aging (By similarity). Protects against reactive oxygen species (ROS) (By similarity). Extracellular HSPA9 plays a cytoprotective role by preventing cell lysis following immune attack by the membrane attack complex by disrupting formation of the complex (PubMed:16091382)","subcellular_location":"Mitochondrion; Nucleus, nucleolus; Cytoplasm; Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/P38646/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/HSPA9","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CLTA","stoichiometry":0.2},{"gene":"DNAJB6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/HSPA9","total_profiled":1310},"omim":[{"mim_id":"620797","title":"DNL-TYPE ZINC FINGER PROTEIN; DNLZ","url":"https://www.omim.org/entry/620797"},{"mim_id":"616854","title":"EVEN-PLUS SYNDROME; EVPLS","url":"https://www.omim.org/entry/616854"},{"mim_id":"616574","title":"MITOCHONDRIAL CONTACT SITE AND CRISTAE ORGANIZING SYSTEM, 10-KD SUBUNIT; MICOS10","url":"https://www.omim.org/entry/616574"},{"mim_id":"615664","title":"THYMOCYTE-EXPRESSED POSITIVE SELECTION-ASSOCIATED PROTEIN 1; TESPA1","url":"https://www.omim.org/entry/615664"},{"mim_id":"615339","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 15; DNAJC15","url":"https://www.omim.org/entry/615339"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HSPA9"},"hgnc":{"alias_symbol":["GRP75","PBP74","mot-2","mthsp75"],"prev_symbol":["HSPA9B"]},"alphafold":{"accession":"P38646","domains":[{"cath_id":"3.30.420.40","chopping":"54-273_356-438","consensus_level":"medium","plddt":94.2427,"start":54,"end":438},{"cath_id":"3.90.640.10","chopping":"274-355","consensus_level":"medium","plddt":95.9222,"start":274,"end":355},{"cath_id":"2.60.34.10","chopping":"443-546","consensus_level":"high","plddt":86.3562,"start":443,"end":546},{"cath_id":"1.20.1270.10","chopping":"554-653","consensus_level":"high","plddt":86.0884,"start":554,"end":653}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P38646","model_url":"https://alphafold.ebi.ac.uk/files/AF-P38646-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P38646-F1-predicted_aligned_error_v6.png","plddt_mean":85.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HSPA9","jax_strain_url":"https://www.jax.org/strain/search?query=HSPA9"},"sequence":{"accession":"P38646","fasta_url":"https://rest.uniprot.org/uniprotkb/P38646.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P38646/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P38646"}},"corpus_meta":[{"pmid":"12482206","id":"PMC_12482206","title":"An 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the N-terminal 46-amino acid presequence is required for mitochondrial targeting, and deletion of this presequence results in cytosolic localization.\",\n      \"method\": \"Confocal immunofluorescence, epitope-tagging, cell fractionation, in vitro import into isolated yeast mitochondria, mitochondrial subfractionation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biochemical and cell biological methods in one study, including in vitro reconstitution of import and mutagenesis of targeting sequence\",\n      \"pmids\": [\"7865888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Mot-2 (HSPA9) binds to and inactivates the tumor suppressor p53 by sequestering it in the cytoplasm, preventing its nuclear translocation; mot-2 but not mot-1 represses p53-mediated transactivation and down-regulates p53-responsive genes p21(WAF-1) and mdm-2.\",\n      \"method\": \"Co-localization by immunofluorescence, p53-responsive reporter assays, Western blot of p53 target genes, GFP-tagged mot-2 nuclear translocation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal functional assays (reporter, target gene expression, localization) replicated across subsequent studies\",\n      \"pmids\": [\"9792667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MKT-077 binds to mortalin/mot-2 (HSPA9) and abrogates its interaction with p53, releasing cytoplasmically sequestered wild-type p53 and restoring its transcriptional activation function in cancer cells.\",\n      \"method\": \"Binding assay, co-immunoprecipitation, p53 transcriptional reporter assay, immunofluorescence\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding demonstrated, functional rescue of p53 activity shown, replicated in multiple subsequent studies\",\n      \"pmids\": [\"11156371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Mortalin/HSPA9 is present not only in mitochondria but also in the endoplasmic reticulum fraction; in certain immortal cell lines it additionally localizes to an extra-organelle cytosolic pool.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence microscopy\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (fractionation + immunofluorescence), single lab\",\n      \"pmids\": [\"10944461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The p53-binding domain of mot-2/HSPA9 was mapped in vitro to its N-terminal amino acid residues 253–282; this region overlaps with the MKT-077-binding region, suggesting MKT-077 restores p53 function by competing with p53 for the same binding site on mot-2.\",\n      \"method\": \"In vitro binding assay with His-tagged deletion mutants, peptide competition assay\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with deletion mutants, single lab\",\n      \"pmids\": [\"11420746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mortalin/GRP75 (HSPA9) physically interacts with GRP94 (an Hsp90-family ER protein); interacting domains were mapped by mutational analysis using far-Western screening, yeast two-hybrid, and co-immunoprecipitation.\",\n      \"method\": \"Far-Western screening, in vivo reporter assay, co-immunoprecipitation, mutational analysis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — three orthogonal methods (far-Western, reporter, CoIP) plus domain mapping, single lab\",\n      \"pmids\": [\"11439088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The mot-2/HSPA9 binding site on p53 was mapped by in vivo co-immunoprecipitation to the C-terminal residues 312–352, which includes p53's cytoplasmic sequestration domain, demonstrating the mechanism by which mot-2 retains p53 in the cytoplasm.\",\n      \"method\": \"In vivo co-immunoprecipitation of mot-2 with p53 deletion mutants\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct domain mapping by co-IP with deletion mutants, single lab, consistent with parallel in vitro study\",\n      \"pmids\": [\"11900485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"VDAC1 physically interacts with PBP74/GRP75/HSPA9 in vivo (yeast two-hybrid) and in vitro (overlay assay with recombinant proteins); GRP75 co-localizes with VDAC1 in HeLa cells and modulates VDAC1 electrophysiological properties, drastically reducing its voltage-dependence in planar lipid bilayer experiments.\",\n      \"method\": \"Sos recruitment system yeast two-hybrid, overlay assay with recombinant proteins, immunofluorescence co-localization, planar lipid bilayer electrophysiology\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro reconstitution with recombinant proteins plus functional electrophysiology, multiple orthogonal methods\",\n      \"pmids\": [\"12009301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"GRP75/mortalin (HSPA9) is a direct intracellular binding partner of fibroblast growth factor-1 (FGF-1); the interaction was identified by affinity purification, confirmed by co-immunoprecipitation, immunohistochemical co-localization, yeast two-hybrid, and direct in vitro binding with recombinant proteins.\",\n      \"method\": \"Affinity adsorption/purification, co-immunoprecipitation, immunohistochemical co-localization, yeast two-hybrid, in vitro binding assay with recombinant proteins\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — five orthogonal methods including in vitro reconstitution with recombinant proteins, single lab\",\n      \"pmids\": [\"10510314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Loss-of-function mutation of HSPA9B within the substrate-binding domain in zebrafish (crimsonless mutant) causes MDS-like ineffective hematopoiesis including anemia, dysplasia, increased apoptosis, and multilineage cytopenia, by compromising mitochondrial function and inducing oxidative stress specifically in blood cells.\",\n      \"method\": \"Positional cloning, rescue experiment, morpholino knockdown in zebrafish\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — positional cloning plus rescue and morpholino knockdown, three converging genetic approaches in a vertebrate model\",\n      \"pmids\": [\"15650063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Mortalin/GRP75 binds complement C8 and C9, promotes shedding of membrane vesicles loaded with complement MAC, and protects cells from complement-mediated lysis; anti-mortalin antibodies reduced vesicle release and elevated complement-mediated cell death.\",\n      \"method\": \"Mass spectrometry identification, Western blot, vesiculation assay, antibody blocking\",\n      \"journal\": \"International immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional blocking antibody experiments plus vesicle isolation, single lab\",\n      \"pmids\": [\"16091382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GRP75/HSPA9 is a functional constituent of noncaveolar, membrane raft-associated endocytic vesicles; RNAi-mediated knockdown of GRP75 and GRP75-blocking antibodies inhibit HSPG-mediated macromolecular endocytosis, and this pathway requires the RhoA GTPase family member CDC42.\",\n      \"method\": \"Antibody-conjugated magnetic nanoparticle vesicle isolation, RNAi knockdown, antibody blocking, co-localization, CDC42 involvement assessed\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional vesicle isolation plus RNAi and antibody blocking, single lab, two orthogonal inhibition approaches\",\n      \"pmids\": [\"20624969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GRP75/HSPA9 overexpression suppresses apoptosis during glucose deprivation by inhibiting Bax conformational change through activation of AKT via a PI3K-independent, Raf/MEK/ERK-dependent pathway.\",\n      \"method\": \"Pharmacological inhibitors (LY294002, U0126), Western blot of pAKT and Bax conformational change, PC12 cell glucose deprivation model\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal inhibitor experiments dissecting pathway, single lab, functional readout of Bax conformational change\",\n      \"pmids\": [\"21964438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HSPA9 knockdown in primary human CD34+ hematopoietic progenitor cells leads to increased TP53 expression and nuclear TP53 accumulation; HSPA9 protein interacts with TP53 in CD34+ cells, and concurrent knockdown of TP53 rescues the increased apoptosis caused by HSPA9 knockdown.\",\n      \"method\": \"Lentiviral shRNA knockdown, co-immunoprecipitation, nuclear/cytoplasmic fractionation, genetic epistasis (double knockdown rescue)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus epistasis rescue, two orthogonal methods, functionally links HSPA9-TP53 interaction to apoptosis regulation\",\n      \"pmids\": [\"28178280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mortalin/HSPA9 is present in the MEK1/MEK2 proteome and acts as a negative regulator of Raf/MEK/ERK signaling; mortalin depletion increases MEK/ERK activity and MEK/ERK-dependent p21(CIP1) transcription, while mortalin overexpression suppresses B-Raf(V600E)-induced MEK/ERK activation and cell cycle arrest.\",\n      \"method\": \"Proteomics (MEK1/2 interactome), shRNA depletion, Western blot, reporter assays in multiple cancer cell lines\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics plus functional KD/OE experiments, single lab, multiple cell lines tested\",\n      \"pmids\": [\"23959801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Mortalin/GRP75 binds complement C9 (and C8) through its N-terminal ATPase domain (not the substrate-binding domain), via an ionic, nucleotide-sensitive interaction; the ATPase domain inhibits zinc-induced C9 polymerization; overexpression of mortalin confers resistance to CDC while knockdown increases sensitivity; cytosolic mortalin (lacking mitochondrial targeting) has reduced protective capacity.\",\n      \"method\": \"Co-immunoprecipitation, recombinant domain expression (ATPase vs. substrate-binding domain), C9 polymerization inhibition assay, mortalinΔ51-EGFP localization and CDC assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — recombinant domain dissection, in vitro functional assay (C9 polymerization), multiple cell-based functional experiments in one study\",\n      \"pmids\": [\"24719326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HSPA9 functions in mitochondrial iron-sulfur cluster (ISC) biogenesis; HSPA9 physically interacts with and stabilizes the ISC biogenesis proteins frataxin, Nfs1, ISCU, and Nfu; HSPA9 depletion decreases aconitase activity (ISC-requiring) but not malate dehydrogenase activity, increases IRP1 binding, and inhibits erythroid differentiation by post-transcriptionally reducing Alas2 and FeCH expression through the IRP/IRE pathway.\",\n      \"method\": \"Co-immunoprecipitation, aconitase activity assay, IRP1 binding assay, RNAi knockdown, erythroid differentiation assay, rescue with Alas2 ORF\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biochemical and genetic approaches in one study, including direct interaction, enzymatic assay, and genetic rescue\",\n      \"pmids\": [\"26702583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Biallelic mutations in HSPA9 cause EVEN-PLUS syndrome, a human disease featuring epiphyseal, vertebral, ear, nose, and other malformations, establishing HSPA9 as essential for mitochondrial protein import/folding and human embryonic morphogenesis.\",\n      \"method\": \"Whole-exome/genome sequencing in affected families, genetic analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — human genetics (biallelic mutations) in two families, no in vitro functional reconstitution but strong genetic evidence\",\n      \"pmids\": [\"26598328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mutations in HSPA9 (a mitochondrial HSP70 involved in mitochondrial Fe-S cluster biogenesis) cause congenital sideroblastic anemia inherited as an autosomal recessive trait; haploinsufficiency can be expressed clinically when a common hypomorphic SNP is present in trans.\",\n      \"method\": \"Genetic sequencing of affected families, functional genetic analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — human genetics with functional pathway context (Fe-S biogenesis), replicated across multiple families\",\n      \"pmids\": [\"26491070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mortalin/HSPA9 facilitates PP1α-mediated dephosphorylation of MEK1/2 by promoting the PP1α-MEK1/2 physical interaction in an ATP-sensitive manner; the region Val482–Glu491 in mortalin's substrate-binding cavity and substrate lid is required for these interactions, consistent with canonical HSP70-client interaction mechanisms.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assay, PP1α inhibitor experiments, mortalin domain mutant analysis, Western blot of phospho-MEK1/2\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding with domain mapping plus cell-based epistasis, multiple orthogonal methods in one study\",\n      \"pmids\": [\"28674184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TG2 (transglutaminase type 2) interacts with GRP75/HSPA9 at mitochondria-associated membranes (MAMs); absence of the TG2-GRP75 interaction increases IP3R-3–GRP75 interaction, decreases ER-mitochondria contact sites, impairs ER-to-mitochondria Ca2+ flux, and alters the MAM proteome.\",\n      \"method\": \"Co-immunoprecipitation (TG2 interactome), proximity ligation assay, TEM quantification of ER-mitochondria contacts, Ca2+ flux measurement, MAM proteomics\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (CoIP, PLA, TEM, Ca2+ flux, proteomics) in one study establishing GRP75 role at MAMs\",\n      \"pmids\": [\"30590033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GRP75/HSPA9 directly interacts with frataxin both in vivo in mouse cortex and in vitro in cortical neurons; GRP75 overexpression increases frataxin levels and stabilizes clinically relevant missense frataxin variants; clinical GRP75 variants (R126W, A476T, P509S) impair GRP75-frataxin binding; GRP75 physically interacts with mitochondrial processing peptidase (MPP), potentially facilitating frataxin processing.\",\n      \"method\": \"Co-immunoprecipitation in vivo and in vitro, GRP75 overexpression/variant rescue experiments in FRDA patient-derived cells, mitochondrial network and ATP level assays\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding in vivo and in vitro, mutagenesis of clinical variants, functional rescue, multiple orthogonal methods\",\n      \"pmids\": [\"30590615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mortalin/HSPA9 identifies adenine nucleotide translocase 3 (ANT3) as a substrate; mortalin inhibits ANT3-CypD interaction to reduce mitochondrial membrane permeability; in BRAF(V600E) cells, mortalin depletion increases mitochondrial permeability (via ANT3-CypD interaction) to a lethal extent, while MEK-ERK activity opposes mortalin by promoting ANT3-CypD interaction.\",\n      \"method\": \"Proteomics screening, co-immunoprecipitation, ANT3/CypD/MCU knockdown and inhibitor rescue, mitochondrial membrane permeability assay, xenograft in vivo model\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomics identification of substrate, multiple genetic/pharmacological epistasis experiments, in vivo validation\",\n      \"pmids\": [\"32156782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mortalin/HSPA9 depletion selectively kills KRAS-mutant cells through a mitochondria-originated death mechanism involving ANT, CypD, and MCU; this cell death occurs independently of TP53 and p21CIP1 and is phenocopied by HSP70 inhibitor JG-98.\",\n      \"method\": \"Genetic knockdown, ANT/CypD/MCU inhibitor/knockdown rescue, xenograft in vivo model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic epistasis, in vivo validation, single lab\",\n      \"pmids\": [\"32291414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GRP75/HSPA9 forms the IP3R-GRP75-VDAC1 complex that mediates Ca2+ transfer from the ER to mitochondria; α-synuclein overexpression impairs the GRP75-IP3R interaction (but not VDAC1-GRP75 interaction) at MAMs, reducing ER-mitochondria contact sites and mitochondrial Ca2+ buffering.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation assay, mitochondrial Ca2+ imaging, ER-mitochondria contact site quantification\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus PLA plus Ca2+ imaging, single lab\",\n      \"pmids\": [\"34510532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GRP75/HSPA9 serves as a scaffold to recruit deubiquitinating enzyme USP1 to inhibit K48-linked polyubiquitination of SIX1, thereby stabilizing SIX1 protein; the C-terminal peptide-binding domain of GRP75 (residues 433–679) is required for GRP75-USP1-SIX1 complex formation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, GRP75 domain deletion analysis, xenograft mouse model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus ubiquitination assay plus domain mapping, single lab, in vivo validation\",\n      \"pmids\": [\"34079090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GRP75/HSPA9 palmitate-induced increase in pancreatic β-cells increases ER-mitochondria physical coupling and mitochondrial Ca2+ transfer leading to apoptosis; GRP75 overexpression alone is sufficient to impair mitochondrial membrane potential, increase mitochondrial Ca2+, and induce apoptosis; GRP75 inhibition prevents palmitate-induced aberrations.\",\n      \"method\": \"GRP75 overexpression/knockdown, mitochondrial Ca2+ measurement, mitochondrial membrane potential assay, ROS assay, TEM for ER-mitochondria contacts, in vivo palmitate injection model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with multiple orthogonal readouts, in vivo confirmation, single lab\",\n      \"pmids\": [\"34756890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HSPA9/mortalin down-regulation induces mitochondrial fragmentation and axonal damage in primary neurons, while overexpression confers protection against rotenone-induced axonal degeneration; mortalin modulates mitochondrial morphology by acting on DRP1 phosphorylation.\",\n      \"method\": \"Lentiviral over-expression and knockdown, microfluidic-based axonal compartment cultures, mitochondrial morphology quantification, DRP1 phosphorylation Western blot\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with specific molecular readout (DRP1 phosphorylation), single lab\",\n      \"pmids\": [\"34489498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GRP75/HSPA9 regulates mitochondrial supercomplex assembly and stabilization to modulate insulin sensitivity; GRP75 induction prevents high-fat diet-induced obesity and insulin resistance in mice; GRP75 knockdown increases mitochondrial fragmentation, triggers cytosolic mtDNA release, and activates the cGAS/STING-dependent proinflammatory response.\",\n      \"method\": \"In vivo GRP75 induction mouse model (HFD), GRP75 knockdown, mitochondrial supercomplex analysis, respiratory chain complex activity assay, cGAS/STING activation assay\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro gain/loss-of-function with mechanistic readouts, single lab\",\n      \"pmids\": [\"34810178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The IP3R1-GRP75-VDAC1 complex mediates ER stress-mitochondrial oxidative stress and Ca2+ transfer in diabetic atrial remodeling; GRP75 conditional cardiac knockout impairs calcium transport from ER to mitochondria and attenuates atrial remodeling and AF progression.\",\n      \"method\": \"siRNA silencing, conditional knockout mouse (Myh6-Cre+/Hspa9flox/flox), proximity ligation assay, Ca2+ imaging, in situ PLA\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic conditional KO plus siRNA plus PLA and Ca2+ flux measurements, multiple orthogonal approaches, in vivo validation\",\n      \"pmids\": [\"35344886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DNLZ/HEP stimulates HSPA9 ATPase activity through a conserved histidine (H107) residue; DNLZ-H107A fails to stimulate HSPA9 catalytic activity even at concentrations 10-fold above the half-maximal effective concentration, while retaining reduced binding to nucleotide-free HSPA9.\",\n      \"method\": \"Alanine mutagenesis scan, ATPase activity measurement, tryptophan fluorescence binding assay, E. coli co-expression solubility assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with in vitro enzymatic assay, specific critical residue identified\",\n      \"pmids\": [\"21530495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Nuclear GRP75/HSPA9 physically interacts with retinoic acid receptors RARα and RXRα in neuroblastoma cells upon RA treatment; GRP75 is required for RARα/RXRα-mediated transcriptional regulation and reduces proteasome-mediated degradation of RARα/RXRα in a RA-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation, transcriptional reporter assay, proteasome inhibitor experiments, immunofluorescence nuclear localization, in vivo xenograft\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus functional reporter and degradation assays, single lab\",\n      \"pmids\": [\"22022577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Complement activation triggers redistribution of mortalin/GRP75 from mitochondria to the plasma membrane within minutes; cytoplasmic mortalin levels increase in complement-treated cells, as shown by immunoblotting and STED nanoscopy showing juxtaposition of mortalin and C5b-9 at the plasma membrane.\",\n      \"method\": \"STED super-resolution microscopy, immunoblotting of cytoplasmic fraction, complement treatment kinetics\",\n      \"journal\": \"Immunobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — STED nanoscopy plus biochemical fractionation, single lab, two orthogonal methods\",\n      \"pmids\": [\"27475989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"GRP75/HSPA9 upregulates clathrin-independent endocytosis (CIE) and inhibits clathrin-mediated endocytosis (CME) through its mitochondria-localized ATPase domain; this regulation is mediated by concurrent activation of Cdc42 and RhoA, inducing stress fibers and filopodia; silencing either Cdc42 or RhoA impairs GRP75-driven CIE enhancement.\",\n      \"method\": \"Mitochondrial signal peptide-directed expression constructs, endocytosis functional assays (transferrin/CTB uptake), Rho GTPase activity assay, siRNA silencing of Cdc42/RhoA, actin cytoskeleton imaging\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain targeting experiments plus genetic epistasis (Cdc42/RhoA silencing), single lab, multiple orthogonal readouts\",\n      \"pmids\": [\"27090015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GRP75/HSPA9 is associated with proto-Dbl inside cells and promotes proto-Dbl degradation through the CHIP-mediated ubiquitin-proteasome pathway, acting as a cooperator with CHIP and competitor to Hsc70/Hsp90 in the chaperone-assisted degradation machinery.\",\n      \"method\": \"Co-immunoprecipitation, endocytosis assays (macropinocytosis, CME, CIE), siRNA knockdown, GRP75 inhibitor MKT-077, Rho GTPase activation assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus functional endocytosis and degradation assays, single lab\",\n      \"pmids\": [\"30250167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hsp90 directly binds mortalin/GRP75; geldanamycin-mediated Hsp90 inhibition failed to sensitize cells with knocked-down mortalin to complement-dependent cytotoxicity, establishing mortalin as epistatic to Hsp90 in CDC resistance.\",\n      \"method\": \"Co-immunoprecipitation of Hsp90 with mortalin in cell extracts and with purified recombinant proteins, genetic epistasis (Hsp90 inhibitor in mortalin-KD cells), CDC assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding with recombinant proteins plus genetic epistasis, single lab\",\n      \"pmids\": [\"29396434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Grp75/HSPA9 mediates mitochondrial import of DJ-1; resveratrol enhances Grp75-DJ-1 interaction and promotes DJ-1 translocation to mitochondria; Grp75 knockdown abolishes resveratrol-induced DJ-1 mitochondrial translocation and prevents subsequent preservation of mitochondrial complex I activity.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, mitochondrial fractionation, complex I activity assay, ROS measurement\",\n      \"journal\": \"Journal of cardiovascular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus genetic knockdown epistasis and functional enzymatic readout, single lab\",\n      \"pmids\": [\"32040033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"OMA1 competitively binds HSPA9 to induce mitophagy and GBM immune escape; OMA1-HSPA9 interaction (identified by Co-IP and mass spectrometry) promotes mitochondrial DNA release, activates cGAS-STING, and upregulates PD-L1 transcription.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, siRNA knockdown, immunofluorescence, immunohistochemistry, Western blot\",\n      \"journal\": \"Journal for immunotherapy of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus MS plus functional pathway analysis, single lab\",\n      \"pmids\": [\"38604814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MUL1 SUMOylates HSPA9 at K612, causing HSPA9 export from mitochondria and nuclear interaction with SUZ12 and EZH2; HSPA9 nuclear translocation leads to ubiquitination-mediated degradation of SUZ12 and EZH2 and downstream STAT3 pathway inhibition; mutation of K612 blocks HSPA9 translocation and abolishes MUL1-mediated tumor suppression.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis (K612), SUMOylation assay, immunofluorescence localization, in vitro and in vivo functional assays\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis plus CoIP and functional rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"39113711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Under ferroptotic conditions, lipid peroxidation activates cAMP-dependent PKA anchored by AKAP1 at the outer mitochondrial membrane, which phosphorylates GRP75 at S148; phosphorylated GRP75 translocates from mitochondria to MAMs/cytosol, where it competes with Nrf2 for Keap1 binding through a conserved ETGE motif, stabilizing and activating Nrf2 to transcribe antiferroptotic genes.\",\n      \"method\": \"PKA phosphorylation assay, GRP75 S148A mutagenesis, Keap1 co-immunoprecipitation, Nrf2 target gene reporter, in vivo xenograft ferroptosis model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-directed mutagenesis plus direct binding assay plus transcriptional reporter plus in vivo validation, multiple orthogonal methods\",\n      \"pmids\": [\"39537840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Tumor-derived GRP75 binds adenine nucleotide translocase 2 (ANT2) to form a GRP75-ANT2 complex; stabilized ANT2 enhances its interaction with uncoupling protein 1 (UCP1), promoting white adipose tissue browning and cancer-associated cachexia.\",\n      \"method\": \"Co-immunoprecipitation, GRP75 inhibitor (withanone) treatment, in vivo mouse cachexia models\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus in vivo functional model with inhibitor, single lab\",\n      \"pmids\": [\"39327432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HSPA9 serves as a scaffold to strengthen the USP14-SLC7A11 interaction, promoting USP14-mediated SLC7A11 deubiquitination and thereby suppressing ferroptosis in multiple myeloma; inhibition of USP14 enhances SLC7A11 ubiquitination and degradation, promoting ferroptosis.\",\n      \"method\": \"Proteomics screening, co-immunoprecipitation, ubiquitination assay, USP14 inhibitor IU1, xenograft mouse model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics plus CoIP plus ubiquitination assay and in vivo model, single lab\",\n      \"pmids\": [\"40372919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Ca2+-induced release of mitochondrial outer membrane-bound m-calpain large subunit requires free calpain small subunit (located in the IMS), Grp75, ATP, and Ca2+; the OM-bound m-calpain large subunit is not associated with the small subunit or Grp75 prior to activation.\",\n      \"method\": \"DEAE-Sepharose column chromatography of solubilized OM proteins, calpain activity assay, co-immunoprecipitation, immunoblot\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical reconstitution-like fractionation plus co-IP, single lab\",\n      \"pmids\": [\"21145877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GRP75/HSPA9 mediates ER-mitochondria Ca2+ transfer via the IP3R1-GRP75-VDAC1 axis in retinal vascular endothelial cells under diabetic conditions; elevated mitochondrial Ca2+ leads to increased ROS, decreased mitochondrial membrane potential, cytochrome c release, and caspase-3 activation leading to apoptosis.\",\n      \"method\": \"siRNA knockdown, proximity ligation assay, Ca2+ imaging, mitochondrial membrane potential assay, ROS assay, in vivo STZ-induced DR rat model\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA loss-of-function with multiple mechanistic readouts plus in vivo validation, single lab\",\n      \"pmids\": [\"36551205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DAB2IP competitively binds GRP75 through its Ras-GAP domain, reducing GRP75-driven p53 ubiquitination and proteasomal degradation; mass spectrometry identified GRP75 as an interaction partner of both DAB2IP and p53 in this ubiquitin-related complex.\",\n      \"method\": \"Mass spectrometry profiling, co-immunoprecipitation, ubiquitination assay, DAB2IP domain mapping, in vivo tumor model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS plus CoIP plus ubiquitination assay, single lab\",\n      \"pmids\": [\"35150809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL3-mediated m6A methylation at the HSPA9 mRNA 3'UTR increases mortalin mRNA stability and translation efficiency in cervical cancer cells; exosomal mortalin suppresses cellular senescence and promotes malignant transformation by blocking nuclear transport of p53 and preventing the p53-Gadd45A interaction.\",\n      \"method\": \"m6A methylation assay (3'UTR), mRNA stability assay, exosome isolation, co-immunoprecipitation (mortalin-p53), p53 nuclear/cytoplasmic fractionation, in vivo xenograft\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m6A biochemistry plus CoIP plus localization, single lab, in vivo validation\",\n      \"pmids\": [\"38253218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GRP75/HSPA9 inhibits ubiquitination-mediated HMGA1 degradation by directly binding to HMGA1, causing HMGA1 upregulation and activation of JNK/c-JUN signaling in lung adenocarcinoma.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, mRNA sequencing, in vitro and in vivo KD/OE experiments\",\n      \"journal\": \"Thoracic cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP plus ubiquitination assay plus downstream signaling analysis, single lab\",\n      \"pmids\": [\"33755320\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HSPA9/mortalin/GRP75 is a mitochondrial matrix HSP70 chaperone imported via an N-terminal targeting sequence in a membrane-potential- and ATP-dependent manner; it directly binds and cytoplasmic-sequesters p53 (through p53 residues 312–352 engaging mortalin residues 253–282) to inactivate tumor-suppressive p53 activity, an interaction disrupted by MKT-077; it serves as the central tether of the IP3R-GRP75-VDAC1 complex at mitochondria-associated ER membranes (MAMs) to regulate ER-to-mitochondria Ca2+ transfer and mitochondrial bioenergetics; it supports mitochondrial iron-sulfur cluster biogenesis by stabilizing frataxin, Nfs1, ISCU, and Nfu; it regulates MEK/ERK signaling by facilitating PP1α-mediated MEK1/2 dephosphorylation; it suppresses ANT3-CypD-dependent mitochondrial permeability transition to promote survival in BRAF/KRAS-mutant tumor cells; it scaffolds USP-dependent deubiquitination complexes (e.g., USP1-SIX1, USP14-SLC7A11) to stabilize client proteins; it facilitates mitochondrial import of client proteins such as DJ-1; and under ferroptotic stress it is phosphorylated at S148 by AKAP1-anchored PKA and translocates to MAMs/cytosol to compete with Nrf2 for Keap1 binding, activating antioxidant gene transcription.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HSPA9 (mortalin/GRP75) is a HSP70-family chaperone that is imported into the mitochondrial matrix via a cleavable N-terminal presequence in a membrane-potential- and ATP-dependent manner, with its ATPase cycle stimulated by the co-chaperone DNLZ acting through a conserved histidine [#0, #30]. Within mitochondria it supports iron-sulfur cluster biogenesis by physically binding and stabilizing frataxin, Nfs1, ISCU, and Nfu, such that its loss reduces aconitase activity and perturbs erythroid heme synthesis through the IRP/IRE axis [#16, #21]. As a canonical HSP70, it engages client proteins through its substrate-binding cavity to control their stability, signaling, and localization: it facilitates PP1\\u03b1-mediated dephosphorylation of MEK1/2 to negatively regulate Raf/MEK/ERK signaling [#14, #19], and it acts on adenine nucleotide translocases\\u2014inhibiting ANT3-CypD interaction to suppress mitochondrial permeability transition and promote survival of BRAF- and KRAS-mutant tumor cells [#22, #23]. A central, well-characterized role is as the tether of the IP3R-GRP75-VDAC1 complex at mitochondria-associated ER membranes (MAMs), where it bridges ER and mitochondria to govern Ca2+ transfer and downstream bioenergetics, oxidative stress, and apoptosis [#7, #20, #29]. Independently of its mitochondrial function, a cytoplasmic pool of mortalin binds the C-terminal cytoplasmic-sequestration domain of p53 (residues 312\\u2013352) through mortalin residues 253\\u2013282, retaining p53 in the cytoplasm to repress its transcriptional and apoptotic activity; the small molecule MKT-077 competes for this site to release and reactivate p53 [#1, #2, #4, #6, #13]. Mortalin further serves as a scaffold for deubiquitination complexes (USP1-SIX1, USP14-SLC7A11) and stabilizes diverse clients against ubiquitin-proteasome degradation [#25, #41]. Under ferroptotic stress, PKA anchored by AKAP1 phosphorylates GRP75 at S148, driving its translocation to MAMs/cytosol where it competes with Nrf2 for Keap1 binding to activate antioxidant transcription [#39]. Biallelic HSPA9 mutations cause EVEN-PLUS syndrome and autosomal-recessive congenital sideroblastic anemia, consistent with its essential roles in mitochondrial protein folding and Fe-S cluster biogenesis [#17, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established where HSPA9 acts and how it gets there, defining it as a mitochondrial matrix protein dependent on an N-terminal targeting sequence.\",\n      \"evidence\": \"Epitope-tagging, cell fractionation, and in vitro import into isolated mitochondria with presequence deletion\",\n      \"pmids\": [\"7865888\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address extra-mitochondrial pools later observed\", \"Chaperone substrates within the matrix not yet defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Revealed a non-canonical cytoplasmic function: HSPA9 sequesters p53 to block its nuclear activity, linking the chaperone to tumor suppression control.\",\n      \"evidence\": \"Immunofluorescence colocalization, p53 reporter assays, and target-gene Western blotting comparing mot-1 vs mot-2\",\n      \"pmids\": [\"9792667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface not mapped at this stage\", \"Mechanism by which a matrix chaperone reaches cytoplasmic p53 unresolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Mapped the p53-binding region on mortalin and showed it overlaps the MKT-077 site, providing a structural rationale for pharmacological p53 reactivation.\",\n      \"evidence\": \"In vitro binding with His-tagged deletion mutants and peptide competition; MKT-077 binding/rescue assays\",\n      \"pmids\": [\"11420746\", \"11156371\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro mapping only\", \"Single lab\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined both sides of the mortalin-p53 interaction and identified VDAC1 as a direct partner, foreshadowing the MAM tethering role.\",\n      \"evidence\": \"Co-IP with p53 deletion mutants; yeast two-hybrid, recombinant overlay, and planar lipid bilayer electrophysiology for VDAC1\",\n      \"pmids\": [\"11900485\", \"12009301\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of VDAC1 modulation in cells not yet established\", \"Link to ER-mitochondria contact sites not yet drawn\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected HSPA9 loss to a vertebrate disease phenotype, implicating mitochondrial dysfunction and oxidative stress in ineffective hematopoiesis.\",\n      \"evidence\": \"Positional cloning, rescue, and morpholino knockdown in the zebrafish crimsonless mutant\",\n      \"pmids\": [\"15650063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular substrate driving the hematopoietic defect not identified at the time\", \"Domain-specific mechanism unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined a core matrix function in Fe-S cluster biogenesis and tied HSPA9 mutations directly to human Mendelian disease.\",\n      \"evidence\": \"Co-IP and stabilization of frataxin/Nfs1/ISCU/Nfu plus aconitase and IRP1 assays; exome/genome sequencing of EVEN-PLUS and sideroblastic anemia families\",\n      \"pmids\": [\"26702583\", \"26598328\", \"26491070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genetic disease studies lacked in vitro functional reconstitution\", \"Hierarchy of client stabilization within the ISC machinery not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided a chaperone-mechanistic basis for MEK/ERK regulation, mapping the substrate-binding region required for facilitating PP1\\u03b1-MEK1/2 dephosphorylation.\",\n      \"evidence\": \"Co-IP, in vitro binding, domain-mutant analysis, and PP1\\u03b1 inhibitor experiments\",\n      \"pmids\": [\"28674184\", \"23959801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1\\u03b1 recruitment occurs at a specific subcellular site not defined\", \"Single lab for the interactome mapping\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified ANT3 as a client and showed mortalin gates mitochondrial permeability transition, explaining a survival dependency in oncogene-mutant tumors.\",\n      \"evidence\": \"Proteomic substrate screening, ANT3/CypD/MCU knockdown and inhibitor epistasis, permeability assays, and xenografts\",\n      \"pmids\": [\"32156782\", \"32291414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural mode of ANT3 engagement not resolved\", \"Generality across non-BRAF/KRAS contexts unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Consolidated the IP3R-GRP75-VDAC1 tether as the operative MAM Ca2+ transfer machine and showed disease-relevant regulators perturb it.\",\n      \"evidence\": \"Co-IP, proximity ligation, Ca2+ imaging, and TEM in TG2-, alpha-synuclein-, and palmitate-context models\",\n      \"pmids\": [\"30590033\", \"34510532\", \"34756890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and dynamics of the tripartite complex not resolved\", \"How GRP75 distinguishes IP3R isoforms unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated a scaffolding role in deubiquitination, mapping the C-terminal peptide-binding domain as required for recruiting USP1 to stabilize clients.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, GRP75 domain deletions, and xenografts for the GRP75-USP1-SIX1 axis\",\n      \"pmids\": [\"34079090\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Whether scaffolding occurs at mitochondria or cytosol not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established stress-induced relocalization and post-translational control as switches that redirect HSPA9 from mitochondrial chaperone to nuclear/cytosolic signaling roles.\",\n      \"evidence\": \"MUL1-mediated K612 SUMOylation with mutagenesis driving nuclear SUZ12/EZH2 degradation; OMA1 competitive binding driving cGAS-STING/PD-L1\",\n      \"pmids\": [\"39113711\", \"38604814\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab observations\", \"Quantitative fraction of relocalized protein not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a phosphorylation-gated antiferroptotic axis: PKA-mediated S148 phosphorylation redirects GRP75 to compete with Nrf2 for Keap1, activating antioxidant transcription.\",\n      \"evidence\": \"PKA phosphorylation and S148A mutagenesis, Keap1 co-IP, Nrf2 reporter, and in vivo ferroptosis xenografts\",\n      \"pmids\": [\"39537840\", \"40372919\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the ETGE-motif competition not resolved\", \"Interplay with mitochondrial functions during ferroptosis unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single matrix-imported chaperone is partitioned among its mitochondrial, MAM, cytoplasmic, and nuclear pools to execute distinct functions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking import, retention, and stress-induced export\", \"Quantitative regulation of pool distribution unknown\", \"Structural understanding of client selectivity lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 30]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [16, 21, 19]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [7, 20, 25, 41]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 14, 39]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 16, 27]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 3, 32]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [3, 20]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [31, 38]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [16, 28]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 16, 21]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [22, 23, 39, 41]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [14, 19, 39]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [17, 18, 9]}\n    ],\n    \"complexes\": [\n      \"IP3R-GRP75-VDAC1 (MAM Ca2+ transfer complex)\"\n    ],\n    \"partners\": [\n      \"TP53\",\n      \"VDAC1\",\n      \"ITPR1\",\n      \"FXN\",\n      \"MEK1/2\",\n      \"ANT3\",\n      \"KEAP1\",\n      \"USP14\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}