{"gene":"HSPA5","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":1999,"finding":"BiP/GRP78 binds newly-synthesized proteins as they are translocated into the ER lumen, maintaining them in a folding-competent state; it is an essential component of the ER translocation machinery and plays a role in retrograde transport (ERAD) of aberrant proteins destined for proteasomal degradation.","method":"Review synthesizing genetic and biochemical studies in yeast and mammalian cells","journal":"Seminars in cell & developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — foundational findings replicated across multiple labs and organisms, multiple orthogonal methods (genetic, biochemical, cell biology)","pmids":["10597629"],"is_preprint":false},{"year":1992,"finding":"Purified yeast BiP/Kar2 (ortholog of HSPA5) is active as a homodimer and exhibits intrinsic ATPase activity; the ADP-bound form is more protease-resistant than the ATP-bound form, indicating ATP-dependent conformational changes.","method":"Protein purification, ATPase assay, protease susceptibility assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical reconstitution of purified protein with enzymatic assay and conformational analysis","pmids":["1325440"],"is_preprint":false},{"year":1998,"finding":"BiP/GRP78 co-precipitates with amyloid precursor protein (APP) in the ER, transiently interacting with it; expression of an ATPase-dead mutant (T37G) of GRP78 nearly completely blocks APP maturation and reduces secretion of APPs, Aβ40, and Aβ42, demonstrating that GRP78 ATPase activity is required for APP folding and processing.","method":"Metabolic labeling, co-immunoprecipitation, ATPase mutant overexpression in HEK293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — co-IP plus active-site mutagenesis in a single rigorous study","pmids":["9748217"],"is_preprint":false},{"year":2000,"finding":"Murine BiP/GRP78 physically interacts with the lumenal J domain of the transmembrane protein MTJ1; this interaction stimulates BiP ATPase activity at stoichiometric concentrations and is abolished by the conserved HPD→HPQ substitution in MTJ1, demonstrating MTJ1 is a functional DnaJ co-chaperone for BiP.","method":"In vitro ATPase assay, binding studies, site-directed mutagenesis of HPD motif","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, single lab but multiple orthogonal methods","pmids":["10777498"],"is_preprint":false},{"year":2002,"finding":"BiP/GRP78 binds to ATF6 and retains it in the ER; dissociation of BiP from ATF6 upon ER stress allows ATF6 to translocate to the Golgi for proteolytic activation, identifying BiP as the key sensor that couples ER folding capacity to ATF6 activation.","method":"Genetic and biochemical analysis (reviewed mechanistic study)","journal":"Developmental cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic summary of co-IP and functional data from primary studies; review commentary citing the primary experiment","pmids":["12110159"],"is_preprint":false},{"year":2005,"finding":"GRP78/BiP controls the activation of the three transmembrane ER stress sensors (IRE1, PERK, ATF6) through a binding-release mechanism: under non-stress conditions BiP keeps sensors inactive; accumulation of unfolded proteins titrates BiP away, freeing sensors to activate the UPR.","method":"Promoter assays, mRNA/protein quantification, established mechanistic framework","journal":"Methods (San Diego, Calif.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanism replicated across multiple independent labs using reciprocal co-IP and loss-of-function approaches","pmids":["15804610"],"is_preprint":false},{"year":2006,"finding":"MDA-7/IL-24 physically interacts with BiP/GRP78 through its C and F helices; the complex localizes in the ER and activates p38 MAPK and GADD gene expression, leading to cancer-selective apoptosis.","method":"Deletion and mutational analysis, co-immunoprecipitation, subcellular localization","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — rationally designed mutagenesis plus co-IP in cancer cells, single lab","pmids":["16912197"],"is_preprint":false},{"year":2009,"finding":"Cell-surface GRP78 functions as a signaling receptor: binding of activated α2-macroglobulin activates AKT to suppress apoptosis and upregulates NF-κB; interaction with Cripto nullifies TGF-β/Smad2/3 signaling; interaction with Par-4 or plasminogen kringle 5 promotes apoptosis; association with tissue factor inhibits procoagulant activity.","method":"Cell-surface binding assays, signaling pathway analysis, co-immunoprecipitation","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple binding partners and functional outcomes established by independent labs, though described in a review","pmids":["19331544"],"is_preprint":false},{"year":2009,"finding":"Cab45S specifically binds to the nucleotide-binding domain (NBD) of GRP78/BiP and stabilizes the GRP78-IRE1 interaction, thereby inhibiting ER stress-induced IRE1 activation and downstream JNK phosphorylation and apoptosis.","method":"Co-immunoprecipitation, domain-mapping, siRNA knockdown, functional apoptosis assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP with domain mapping and functional rescue, single lab","pmids":["24810055"],"is_preprint":false},{"year":2015,"finding":"GP78 (E3 ubiquitin ligase) interacts with the C-terminal region of HSPA5 and mediates its polyubiquitination at lysine 447 (K447), targeting HSPA5 for proteasomal degradation; HDAC6 deacetylates HSPA5 at K353, which is required for GP78-mediated ubiquitination at K447.","method":"Co-immunoprecipitation, ubiquitination assays, site-directed mutagenesis (K447, K353), HDAC6 knockdown","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-specific mutagenesis identifying ubiquitination and acetylation sites, co-IP, functional assays in a single rigorous study","pmids":["26119938"],"is_preprint":false},{"year":2016,"finding":"HDAC6 deacetylation of HSPA5 at K633 promotes its secretion into exosomes via the multivesicular body (MVB) pathway; acetylated HSPA5 (mimicked by K633Q mutation) binds VPS34 and prevents MVB sorting, blocking secretion.","method":"HDAC inhibitor treatment, acetylation-mimetic mutagenesis (K633Q), VPS34 co-IP, exosome fractionation","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus co-IP and fractionation, single lab, two orthogonal methods","pmids":["27460191"],"is_preprint":false},{"year":2016,"finding":"FOXM1 directly binds to and transactivates the HSPA5 promoter at a site mapped between −1019 and −1012 bp, upregulating HSPA5 expression; HSPA5 depletion attenuates FOXM1-driven colorectal cancer cell migration and invasion, acting downstream through cell-surface HSPA5 and MMP2/9 activity.","method":"Promoter-binding assay, chromatin immunoprecipitation, luciferase reporter, siRNA knockdown, invasion assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and promoter mapping plus functional knockdown, single lab","pmids":["27034162"],"is_preprint":false},{"year":2016,"finding":"N-terminal arginylation (Nt-arginylation) of HSPA5 by ATE1 arginyltransferase generates R-HSPA5 in the cytosol; R-HSPA5's N-terminal arginine is recognized by the ZZ domain of SQSTM1/p62, inducing SQSTM1 conformational change, self-polymerization, and LC3 interaction, thereby directing misfolded protein cargoes to autophagosomes for lysosomal degradation.","method":"In vitro arginylation, co-immunoprecipitation, autophagy flux assays, domain-specific interaction mapping","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution of arginylation, co-IP showing R-HSPA5/SQSTM1 interaction, functional autophagy assays in a single focused study","pmids":["26797053"],"is_preprint":false},{"year":2017,"finding":"HSPA5 binds directly to GPX4 protein and protects it from degradation; ATF4-induced HSPA5 upregulation stabilizes GPX4 protein levels, thereby inhibiting lipid peroxidation and conferring ferroptosis resistance in pancreatic ductal adenocarcinoma cells.","method":"Co-immunoprecipitation, siRNA/pharmacological inhibition, GPX4 protein stability assays, in vitro and in vivo ferroptosis assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP, loss-of-function, replicated by multiple subsequent studies with orthogonal approaches","pmids":["28130223"],"is_preprint":false},{"year":2017,"finding":"GRP78 localizes to the mitochondria-associated ER membrane (MAM) where it folds steroidogenic acute regulatory protein (StAR); GRP78 knockdown drastically reduces StAR expression and steroidogenic activity, identifying GRP78 as an acute regulator of steroidogenesis at the MAM.","method":"GRP78 knockdown, subcellular fractionation (MAM isolation), StAR activity assays, protein folding experiments","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with defined functional readout and subcellular fractionation, single lab","pmids":["28275724"],"is_preprint":false},{"year":2017,"finding":"GRP78/BiP directly interacts with misfolded PrPSc in vitro; recombinant GRP78 incubated with PrPSc reduces protease-resistant PrPSc in a dose-dependent manner; in cells, BiP expression levels inversely correlate with prion replication; in vivo, reduced GRP78 expression accelerates prion pathogenesis.","method":"In vitro incubation of recombinant GRP78 with PrPSc, cell culture prion replication assay, co-immunoprecipitation, conditional knockout mouse model","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus cell and in vivo loss-of-function, multiple orthogonal methods","pmids":["28333162"],"is_preprint":false},{"year":2018,"finding":"MUL1 (mitochondrial E3 ubiquitin ligase) directly ubiquitinates HSPA5 at lysine 446 (K446) via K48-linked ubiquitin chains, promoting HSPA5 proteasomal degradation; this leads to lysosomal inhibition and cytotoxicity in head and neck cancer cells.","method":"K446 site mutagenesis, ubiquitination assays, CRISPR/Cas9 MUL1 knockout, xenograft model","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-specific mutagenesis, K48-linkage specificity, CRISPR KO validation in a single rigorous study","pmids":["29260979"],"is_preprint":false},{"year":2019,"finding":"The deubiquitylase OTUD3 interacts with GRP78, removes its ubiquitin chains, and stabilizes GRP78 protein; OTUD3 knockdown reduces GRP78 protein levels and suppresses lung cancer cell growth and migration.","method":"Co-immunoprecipitation, deubiquitylation assay, OTUD3 knockdown, mouse lung adenocarcinoma model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP, deubiquitylation assay, and in vivo mouse model, single lab with multiple orthogonal methods","pmids":["31266968"],"is_preprint":false},{"year":2019,"finding":"DHA-induced ER stress activates the PERK→ATF4→HSPA5 pathway in glioma cells; HSPA5 upregulation then increases GPX4 expression and activity, neutralizing lipid peroxidation and protecting cells from ferroptosis via a negative feedback loop.","method":"siRNA knockdown of PERK/ATF4/HSPA5, GPX4 activity assays, ROS/lipid peroxidation measurement, in vitro and in vivo models","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway epistasis via siRNA knockdown with functional readouts, single lab","pmids":["31519193"],"is_preprint":false},{"year":2019,"finding":"BiP/GRP78 overexpression strengthens circadian rhythm oscillation amplitude; adequate BiP levels preemptively prevent ER stress in collagen-synthesizing fibroblasts, thereby preventing UPR activation and maintaining circadian gene expression.","method":"BiP overexpression, chemical chaperone treatment, circadian reporter assays in fibroblasts and tendon tissue","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression gain-of-function with defined phenotypic (circadian) readout, single lab","pmids":["30888851"],"is_preprint":false},{"year":2019,"finding":"Inadequate BiP availability is the defining molecular event of proteostatic ER stress: conditions that prevent restoration of excess BiP over unfolded substrate (μs heavy chain) — including abrogation of HRD1-mediated ERAD or the ATF6α branch of UPR — lead to proteotoxicity; removal of the BiP-sequestering CH1 domain from µs tolerates the same conditions without toxicity.","method":"Inducible expression of secretory IgM heavy chain, genetic ablation of ERAD (HRD1 KO) and UPR branches, electron microscopy","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with multiple UPR/ERAD branch knockouts and substrate engineering, multiple orthogonal approaches","pmids":["30869076"],"is_preprint":false},{"year":2019,"finding":"Cell-surface GRP78 (csGRP78) interacts with integrin β1 on kidney mesangial cells under high-glucose conditions, activating focal adhesion kinase and downstream PI3K/AKT signaling, which drives extracellular matrix protein synthesis; both N- and C-termini of csGRP78 are required for this profibrotic response.","method":"Cell-surface biotinylation, co-immunoprecipitation of csGRP78 with integrin β1, siRNA knockdown, signaling assays, diabetic mouse models","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP, domain mutagenesis, in vivo diabetic model, multiple orthogonal methods in one study","pmids":["30914477"],"is_preprint":false},{"year":2019,"finding":"Intracellular (not cell-surface) BiP/GRP78 mediates thrombin-induced Ca2+ signaling and endothelial permeability, as well as NF-κB-dependent upregulation of VCAM-1, ICAM-1, IL-6, and IL-8; specific inactivation of intracellular BiP by the protease SubAB or a dominant-negative mutant abolishes these responses in vitro and reduces LPS-induced lung injury in vivo.","method":"SubAB-mediated selective BiP cleavage, dominant-negative BiP gene transfer, LPS-inhalation mouse model, Ca2+ imaging, permeability assays","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific enzymatic inactivation tool (SubAB), DN mutant, and in vivo model; multiple orthogonal approaches distinguishing intra- vs. surface pools","pmids":["30765717"],"is_preprint":false},{"year":2020,"finding":"ATE1-mediated arginylation of HSPA5 (generating R-HSPA5) is induced by ROS upon proteasome inhibition; R-HSPA5 binds K48-linked polyubiquitinated AKT (sequentially ubiquitinated at K284 then K214 by MUL1) and escorts it to the autophagy-lysosome pathway for degradation; USP7 antagonizes this by deubiquitinating AKT.","method":"Co-immunoprecipitation, ubiquitin linkage analysis, ATE1 overexpression, MUL1 knockout cells, autophagy flux inhibitors","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP, KO cell validation, linkage-specific ubiquitin analysis, and autophagy inhibitors; multiple orthogonal methods in single lab","pmids":["32164484"],"is_preprint":false},{"year":2020,"finding":"HSPA5 interacts with negatively charged phospholipids (POPS, cardiolipin) via both its N- and C-terminal domains; membrane binding promotes HSPA5 oligomerization through intermolecular disulfide bonds, with the N-terminal domain playing a critical role in this process.","method":"Liposome binding assays with purified full-length and truncated HSPA5, disulfide bond analysis","journal":"Cell stress & chaperones","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein and defined lipid compositions, single lab","pmids":["32725381"],"is_preprint":false},{"year":2021,"finding":"HSPA5/GRP78 mediates Pneumocystis carinii binding and colonization of lung epithelial cells; affinity chromatography identified HSPA5 as the receptor, and CHO cells overexpressing HSPA5 bound Pc organisms more than parental cells, confirming direct Pc-HSPA5 protein interaction.","method":"Affinity chromatography, overexpression binding assay in CHO cells, primary rat airway epithelial cells","journal":"Journal of medical microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — affinity chromatography plus receptor overexpression binding confirmation, single lab","pmids":["30328808"],"is_preprint":false},{"year":2020,"finding":"NLRP6 binds to GRP78 through its Pyrin domain (interaction mediated via the SBD domain of GRP78), promotes GRP78 polyubiquitination, and thereby suppresses gastric cancer cell proliferation, cell cycle progression, migration, and tumorigenesis.","method":"Flag-tagged immunoprecipitation, LC/MS proteomics, ubiquitination assays, domain mapping, overexpression/knockdown, xenograft model","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain mapping, ubiquitination assay, and in vivo model, single lab","pmids":["32682010"],"is_preprint":false},{"year":2021,"finding":"HSPA5/GRP78 is required for KrasG12D-driven lung adenocarcinoma initiation and progression; GRP78 haploinsufficiency in floxed mouse models suppresses KrasG12D-mediated lung tumor progression, prolongs survival, and GRP78 knockdown in human lung cancer cells (KrasG12D/+) activates UPR and apoptotic markers.","method":"Conditional knockout mouse model (floxed Grp78 × KrasLSL-G12D), siRNA knockdown in human lung cancer cells, tumor histology, survival analysis","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional in vivo knockout with genetic epistasis to KrasG12D plus human cell knockdown; multiple orthogonal methods","pmids":["33931739"],"is_preprint":false},{"year":2021,"finding":"GRP78 knockdown in macrophages promotes M1 differentiation and suppresses M2 polarization via the JAK/STAT pathway; GRP78 regulates IGF-1 secretion by macrophages and, in response to IGF-1, GRP78 translocates to the plasma membrane and associates with the IGF-1 receptor to promote M2 polarization.","method":"GRP78 knockdown, cytokine secretion assay, JAK/STAT pathway analysis, IGF-1 neutralization, subcellular fractionation, co-immunoprecipitation, conditioned medium experiments","journal":"Cellular and molecular life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown, co-IP, and neutralization experiments in vitro and in vivo, single lab","pmids":["34713304"],"is_preprint":false},{"year":2021,"finding":"SARS-CoV-2 spike protein physically interacts with cell-surface GRP78, promoting binding and accumulation in ACE2-expressing cells; GRP78 expression in adipose tissue is upregulated by hyperinsulinemia partly through the XBP-1s transcription factor.","method":"Co-immunoprecipitation of spike protein with GRP78, cell binding assays, gene expression analysis in adipocytes","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP of spike-GRP78 plus mechanistic XBP-1s pathway, single lab","pmids":["34615619"],"is_preprint":false},{"year":2021,"finding":"HYPE/FicD AMPylates BiP/GRP78 at Thr518 (structurally preferred) and Thr366; AMPylation at Thr366 vs. Thr518 differentially affects BiP ATPase activity; HYPE preferentially de-AMPylates wild-type adenylylated BiP; HYPE does not adenylylate UPR accessory proteins like ERdJ6.","method":"In vitro AMPylation kinetic assays, molecular docking, ATPase activity assays, binding efficiency measurements","journal":"Cell stress & chaperones","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with site mutagenesis, kinetic analysis, and structural docking in a single rigorous study","pmids":["33942205"],"is_preprint":false},{"year":2022,"finding":"HspA5/GRP78 directly binds the RNA-recognition motif (RRM) domain of TDP-43 in a pulldown assay using recombinant proteins; overexpression of HspA5 in a Drosophila TDP-43 toxicity model rescues TDP-43-induced lethality, indicating HspA5 mitigates TDP-43 proteotoxicity.","method":"BioID proximity labeling, recombinant protein pulldown, Drosophila overexpression rescue assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — recombinant protein interaction plus in vivo Drosophila rescue, single lab","pmids":["35581326"],"is_preprint":false},{"year":2022,"finding":"GRP94 acts upstream of BiP in ER protein remodeling under strong denaturing conditions: Grp94 binds misfolded proteins in an ATP-independent manner to prevent aggregation, then releases them via ATP binding (without hydrolysis) for subsequent refolding by the BiP system; direct Grp94-BiP interaction is not required for client transfer.","method":"In vitro refolding assays with purified proteins, ATP binding/hydrolysis mutants, aggregation prevention assays","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with defined ATP mutants and ordered epistasis, single lab but rigorous biochemistry","pmids":["35905823"],"is_preprint":false},{"year":2023,"finding":"Nuclear GRP78 regulates gene expression by interacting with and inhibiting the transcriptional repressor ID2, promoting expression of genes involved in cell migration and invasion; a nuclear localization signal in GRP78 is critical for its stress-induced translocation to the nucleus.","method":"NLS mutagenesis, nuclear fractionation, co-immunoprecipitation of GRP78-ID2, gene expression profiling, cancer cell migration assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — NLS mutagenesis, co-IP, nuclear fractionation, and functional migration assays with multiple orthogonal methods in a single rigorous study","pmids":["37487081"],"is_preprint":false},{"year":2023,"finding":"EP300 acetyltransferase acetylates HSPA5 at K353, causing loss of its ability to inhibit lipid peroxidation and ferroptotic cell death in pancreatic cancer cells; HDAC6 opposes this by deacetylating HSPA5, limiting ferroptosis sensitivity.","method":"In vitro acetylation assay, K353 site mutagenesis, EP300 and HDAC6 genetic/pharmacological manipulation, ferroptosis assays (lipid ROS, cell death)","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — site-specific mutagenesis and enzymatic acetylation assay, single lab","pmids":["37696842"],"is_preprint":false},{"year":2024,"finding":"ZDHHC9 palmitoylates GRP78/BiP at cysteine 420 (Cys420), enhancing BiP protein stability and maintaining its ER localization; this palmitoylation inhibits the unfolded protein response and promotes bladder cancer progression and chemoresistance.","method":"Co-immunoprecipitation of ZDHHC9-Bip, palmitoylation assay at Cys420, ZDHHC9 knockdown, UPR marker analysis, subcellular localization","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, site-specific palmitoylation at Cys420, functional UPR and localization assays, single lab","pmids":["39002690"],"is_preprint":false},{"year":2009,"finding":"HDAC1 binds to the Grp78 promoter under non-stress conditions (demonstrated by ChIP) and represses its transcription; ER stress causes HDAC1 dissociation from the promoter, allowing GRP78 induction; overexpression of GRP78 confers resistance to HDAC inhibitor-induced apoptosis, while GRP78 knockdown sensitizes cancer cells.","method":"Chromatin immunoprecipitation (ChIP), promoter mutational analysis, HDAC1 overexpression/siRNA knockdown, apoptosis assays","journal":"Molecular cancer therapeutics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP identifying direct promoter occupancy, mutagenesis, and functional gain/loss-of-function in single study","pmids":["19417144"],"is_preprint":false},{"year":2011,"finding":"GRP78 promotes PI3K/AKT/mTOR oncogenic signaling in the hematopoietic system; heterozygous knockout of GRP78 in PTEN-null mice restores the hematopoietic stem cell population, suppresses leukemic blast expansion, and potently inhibits AKT/mTOR activation in PTEN-null BM cells.","method":"Biallelic conditional knockout mouse model (GRP78 × PTEN), flow cytometry, AKT/mTOR phosphorylation assays, GRP78 knockdown in leukemia cell lines","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional KO genetic epistasis replicated in cell lines, multiple methods","pmids":["21937694"],"is_preprint":false},{"year":2012,"finding":"IGF-1 receptor signaling regulates GRP78 expression via the PI3K/AKT/mTORC1 axis (independently of FOXO1 and the canonical UPR); IGF-1 receptor-null MEFs express 80% less GRP78 but remain capable of activating the UPR when needed.","method":"IGF-1R knockout and overexpression MEFs, mTORC1 and PI3K inhibitors, FOXO1 knockdown, calorie restriction in mice","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO/OE plus pharmacological inhibitors with defined pathway exclusion, single lab","pmids":["22422508"],"is_preprint":false},{"year":1999,"finding":"BiP/GRP78 co-immunoprecipitates with AMPA receptor subunits (GluR1, GluR2/3, GluR4) from rat forebrain membranes; both BiP and calnexin are detected in dendrites of hippocampal pyramidal neurons co-localizing with AMPA receptor subunits, consistent with an ER chaperone role in AMPA receptor assembly.","method":"Co-immunoprecipitation from native brain membranes, western blotting, immunocytochemistry","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP from native tissue plus anatomical co-localization, single lab","pmids":["10461883"],"is_preprint":false},{"year":2014,"finding":"Hspa5/GRP78 is essential for pronephros (kidney) formation in Xenopus; knockdown with morpholino antisense oligonucleotides inhibits pronephric marker gene expression (lhx1, pax2, atp1b1) by attenuating retinoic acid (RA) signaling and reducing Lhx1 expression; co-injection of lhx1 mRNA partially rescues the phenotype.","method":"Morpholino knockdown in Xenopus embryos, animal cap explant assay, rescue by mRNA injection, retinoic acid-responsive gene expression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino knockdown with mRNA rescue and epistasis to RA-Lhx1 pathway, single lab","pmids":["25398881"],"is_preprint":false},{"year":2015,"finding":"BiP/GRP78 is critical for myelinating cell survival; conditional knockout of BiP in oligodendrocytes causes tremors, ataxia, and premature death in developing mice, and triggers oligodendrocyte loss and myelin abnormalities; adult knockout produces severe neurological symptoms; BiP haploinsufficiency exacerbates EAE-induced oligodendrocyte loss.","method":"Oligodendrocyte-specific conditional BiP knockout mouse, Schwann cell-specific conditional BiP knockout, EAE model, neuropathology","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional KO in multiple cell types with replicated severe phenotypes and disease model epistasis","pmids":["26631473"],"is_preprint":false},{"year":2015,"finding":"Increased BiP expression in Alzheimer's disease model (Tg2576) brains induces tau hyperphosphorylation by activating GSK-3β and increasing the association of tau with GSK-3β; SIL1 (BiP co-chaperone) deficiency is observed in Tg2576 brains and under ER stress, and SIL1 overexpression reduces BiP-induced tau hyperphosphorylation and GSK-3β activation.","method":"Bip-EGFP transfection in HEK293/tau cells, co-immunoprecipitation of tau-GSK3β, SIL1 overexpression, transgenic mouse brain analysis","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and overexpression studies with defined kinase activation readout, single lab","pmids":["25575678"],"is_preprint":false},{"year":2013,"finding":"GRP78/BiP is recruited into androgen receptor (AR) inclusions in embryonic stem cells (ESCs) upon androgen stimulation; GRP78 dissociates from ATF6 and instead acts as an AR-interacting protein; GRP78 overexpression suppresses AR aggregate ubiquitination and ameliorates misfolded AR-mediated cytopathology, while GRP78 knockdown increases AR aggregates and caspase-3 activity.","method":"Co-immunoprecipitation of GRP78-AR, immunofluorescence co-localization, GRP78 overexpression/knockdown, ubiquitination assay, caspase-3 activity","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus gain/loss-of-function with functional readouts, single lab","pmids":["23618905"],"is_preprint":false}],"current_model":"HSPA5/GRP78/BiP is an ER-luminal HSP70-family chaperone with intrinsic ATPase activity that, via ATP-driven conformational cycling stimulated by DnaJ-type co-chaperones (e.g., MTJ1), binds and folds nascent secretory proteins during translocation, retains misfolded proteins for ERAD, and sequesters the three UPR transmembrane sensors (IRE1, PERK, ATF6) in their inactive states until titrated away by unfolded protein load; under chronic or severe ER stress, HSPA5 is subject to multiple post-translational modifications—AMPylation at Thr518/Thr366 by HYPE/FicD, ubiquitination at K447 by GP78/NLRP6-promoted pathways (opposed by OTUD3 deubiquitylase), and acetylation at K353 by EP300 (opposed by HDAC6) or at K633 (controlling exosomal secretion)—that regulate its activity, stability, and trafficking; additionally, HSPA5 is arginylated at its N-terminus by ATE1 upon cytosolic relocalization, enabling it to activate SQSTM1/p62-dependent selective autophagy of misfolded proteins; beyond the ER, HSPA5 translocates to the mitochondria-associated membrane to fold StAR and regulate steroidogenesis, to the cell surface where it acts as a receptor for diverse ligands (α2-macroglobulin, Cripto, integrin β1, viral proteins) and activates PI3K/AKT and JAK/STAT signaling, and to the nucleus where it binds and inhibits the transcriptional repressor ID2 to promote an invasive gene expression program, collectively making HSPA5 a multifunctional stress-response hub whose inhibition suppresses ferroptosis resistance (via GPX4 stabilization), oncogenic AKT/mTOR signaling, and tumor progression."},"narrative":{"mechanistic_narrative":"HSPA5 (BiP/GRP78) is the principal ER-luminal HSP70-family chaperone that couples protein folding capacity to cellular stress responses [PMID:10597629, PMID:15804610]. It is an ATP-driven machine that binds nascent and unfolded secretory proteins, maintaining them in a folding-competent state during ER translocation and triaging aberrant proteins to ERAD [PMID:10597629]; its intrinsic ATPase activity drives conformational cycling between protease-resistant ADP-bound and ATP-bound states [PMID:1325440], and this cycle is stimulated by DnaJ-type co-chaperones such as the transmembrane protein MTJ1 [PMID:10777498], with GRP94 acting upstream to hand off misfolded clients to the BiP system [PMID:35905823]. ATPase-competent HSPA5 is required for folding and maturation of specific clients including APP [PMID:9748217], and inadequate BiP availability relative to unfolded substrate is the defining molecular trigger of proteotoxic ER stress [PMID:30869076]. Centrally, HSPA5 governs the unfolded protein response by binding and sequestering the three transmembrane sensors IRE1, PERK, and ATF6 in their inactive states until accumulating unfolded protein titrates it away, releasing the sensors and coupling folding capacity to ATF6, PERK, and IRE1 activation [PMID:12110159, PMID:15804610]. HSPA5 abundance and activity are tuned by an extensive post-translational regulatory network: AMPylation at Thr518/Thr366 by HYPE/FicD modulates its ATPase activity [PMID:33942205]; ubiquitination at K447/K446 by GP78, MUL1, and NLRP6-promoted pathways drives proteasomal degradation [PMID:26119938, PMID:29260979, PMID:32682010], opposed by the deubiquitylase OTUD3 [PMID:31266968]; acetylation at K353 by EP300 and at K633, controlled by HDAC6, regulates ferroptosis sensitivity and exosomal secretion [PMID:26119938, PMID:27460191, PMID:37696842]; and palmitoylation at Cys420 by ZDHHC9 stabilizes the protein and its ER localization [PMID:39002690]. Beyond the ER, HSPA5 acquires distinct functions through relocalization: cytosolic N-terminal arginylation by ATE1 generates R-HSPA5, which engages the SQSTM1/p62 ZZ domain to direct misfolded cargoes—and ubiquitinated AKT—to selective autophagy [PMID:26797053, PMID:32164484]; it localizes to the mitochondria-associated membrane to fold StAR and support steroidogenesis [PMID:28275724]; it functions at the cell surface as a signaling receptor for ligands including integrin β1, IGF-1R, α2-macroglobulin, and viral spike proteins, activating PI3K/AKT and JAK/STAT pathways [PMID:19331544, PMID:30914477, PMID:34713304, PMID:34615619]; and it translocates to the nucleus to bind and inhibit the transcriptional repressor ID2, driving an invasive gene expression program [PMID:37487081]. These activities make HSPA5 an oncogenic dependency that stabilizes GPX4 to confer ferroptosis resistance [PMID:28130223, PMID:31519193], promotes PI3K/AKT/mTOR signaling and Kras-driven tumorigenesis [PMID:33931739, PMID:21937694], and is essential for myelinating cell survival and tissue development [PMID:26631473].","teleology":[{"year":1992,"claim":"Established that the BiP ortholog is an autonomous ATPase whose nucleotide state drives conformational change, the biochemical basis for chaperone cycling.","evidence":"Purification of yeast Kar2 with ATPase and protease-susceptibility assays","pmids":["1325440"],"confidence":"High","gaps":["Did not define how ATP cycling couples to client binding in the mammalian protein","Co-chaperone requirements unresolved"]},{"year":1999,"claim":"Defined the core chaperone role: BiP binds nascent proteins entering the ER and triages aberrant ones for ERAD, framing it as essential to ER proteostasis.","evidence":"Synthesis of genetic and biochemical studies in yeast and mammalian cells; co-IP with AMPA receptor subunits from brain","pmids":["10597629","10461883"],"confidence":"High","gaps":["Did not establish substrate specificity rules","Native client repertoire only partially defined"]},{"year":1998,"claim":"Demonstrated that BiP ATPase activity is functionally required for folding of a specific client, linking the enzymatic cycle to physiological maturation.","evidence":"ATPase-dead T37G mutant overexpression and co-IP with APP in HEK293 cells","pmids":["9748217"],"confidence":"High","gaps":["Single client; generality to other secretory proteins not tested here"]},{"year":2000,"claim":"Identified MTJ1 as a functional DnaJ co-chaperone that stimulates BiP ATPase, explaining how BiP activity is spatially and substrate-directed.","evidence":"In vitro ATPase and binding assays with HPD-motif mutagenesis","pmids":["10777498"],"confidence":"High","gaps":["Full set of ER J-proteins coordinating BiP not enumerated","Nucleotide exchange factor role separate"]},{"year":2005,"claim":"Consolidated the binding-release model in which BiP sequesters IRE1, PERK, and ATF6 and is titrated away by unfolded load, establishing BiP as the master UPR sensor.","evidence":"Co-IP, loss-of-function, and promoter/expression assays across labs; ATF6 retention/dissociation mechanism","pmids":["15804610","12110159"],"confidence":"High","gaps":["Whether sensor regulation is purely competitive or allosteric not fully resolved","Stoichiometry of BiP across the three sensors unclear"]},{"year":2009,"claim":"Revealed that cell-surface GRP78 acts as a multifunctional signaling receptor and that its promoter is repressed by HDAC1, expanding GRP78 beyond an ER chaperone.","evidence":"Cell-surface binding/signaling assays with multiple ligands; ChIP of HDAC1 on the Grp78 promoter; Cab45S domain-mapping co-IP","pmids":["19331544","19417144","24810055"],"confidence":"Medium","gaps":["Mechanism of GRP78 surface translocation not defined","Many receptor functions described in review without unified structural model"]},{"year":2015,"claim":"Showed HSPA5 stability is set by competing ubiquitin ligases and deacetylation, establishing post-translational control of chaperone levels.","evidence":"Site-specific mutagenesis (K447, K353), GP78 ubiquitination assays, HDAC6 knockdown","pmids":["26119938"],"confidence":"High","gaps":["Physiological triggers selecting degradation vs. stabilization unclear","Crosstalk between K353 acetylation and other modifications not mapped"]},{"year":2016,"claim":"Defined acetylation-controlled exosomal secretion and FOXM1-driven transcriptional and cytosolic arginylation routes, broadening HSPA5 output to autophagy and intercellular signaling.","evidence":"K633Q mimetic mutagenesis with VPS34 co-IP and exosome fractionation; ChIP and promoter mapping of FOXM1; in vitro arginylation and SQSTM1 ZZ-domain interaction with autophagy flux","pmids":["27460191","27034162","26797053"],"confidence":"High","gaps":["How cytosolic relocalization is triggered remains partially defined","In vivo relevance of exosomal HSPA5 not established here"]},{"year":2017,"claim":"Connected HSPA5 to ferroptosis resistance and to extra-ER folding roles, establishing it as a stabilizer of GPX4 and a MAM steroidogenic factor.","evidence":"Co-IP and GPX4 stability assays in PDAC; MAM fractionation and StAR folding with knockdown; in vitro and in vivo PrPSc clearance","pmids":["28130223","28275724","28333162"],"confidence":"High","gaps":["Mechanism by which HSPA5 protects GPX4 from degradation not structurally defined","MAM targeting signal unknown"]},{"year":2019,"claim":"Demonstrated genetic and physiological consequences of BiP availability across ferroptosis feedback, fibrosis, vascular permeability, circadian rhythm, and the central requirement of excess BiP to avoid proteotoxicity.","evidence":"PERK→ATF4→HSPA5→GPX4 epistasis; csGRP78–integrin β1 co-IP and diabetic models; SubAB selective cleavage and LPS lung injury; BiP overexpression circadian assays; IgM heavy-chain proteostasis with HRD1/ATF6 ablation","pmids":["31519193","30914477","30765717","30888851","30869076"],"confidence":"High","gaps":["Distinct intracellular vs. surface pools incompletely separated mechanistically","How BiP excess is sensed quantitatively not defined"]},{"year":2020,"claim":"Resolved AMPylation and arginylation as conditional activity switches and added membrane-lipid binding and chaperone hierarchy, refining how HSPA5 is reprogrammed under stress.","evidence":"In vitro AMPylation kinetics at Thr518/Thr366 by HYPE; R-HSPA5 escorting ubiquitinated AKT to autophagy in MUL1-KO cells; liposome binding/oligomerization assays; GRP94→BiP client-transfer epistasis; NLRP6 domain-mapped ubiquitination","pmids":["33942205","32164484","32725381","35905823","32682010"],"confidence":"High","gaps":["In vivo significance of AMPylation site selectivity unclear","Lipid-binding role in surface translocation not directly linked"]},{"year":2021,"claim":"Established HSPA5 as an oncogenic dependency and immune/viral interaction node, showing genetic requirement for Kras-driven tumors, macrophage polarization, and SARS-CoV-2 spike binding.","evidence":"Conditional Grp78 KO × KrasLSL-G12D models with human cell knockdown; macrophage knockdown with JAK/STAT and IGF-1R co-IP; spike–GRP78 co-IP","pmids":["33931739","34713304","34615619"],"confidence":"High","gaps":["Whether tumor dependency reflects ER chaperone or surface/signaling functions not separated","Spike–GRP78 contribution to infection in vivo not quantified"]},{"year":2023,"claim":"Identified nuclear GRP78 as a direct regulator of transcription via ID2 inhibition and refined acetylation control of ferroptosis, completing a picture of compartment-specific functions.","evidence":"NLS mutagenesis, nuclear fractionation, GRP78–ID2 co-IP, migration assays; EP300/HDAC6 acetylation at K353 with ferroptosis readouts","pmids":["37487081","37696842"],"confidence":"High","gaps":["Signal triggering nuclear translocation incompletely defined","Direct DNA-binding vs. cofactor-only role of nuclear GRP78 unresolved"]},{"year":2024,"claim":"Added palmitoylation as a stability/localization switch, showing ZDHHC9 modification retains BiP in the ER and suppresses UPR to promote cancer chemoresistance.","evidence":"ZDHHC9–BiP co-IP, Cys420 palmitoylation assay, knockdown, UPR and localization analysis","pmids":["39002690"],"confidence":"Medium","gaps":["Single lab; depalmitoylase counter-enzyme not identified","Interplay with ubiquitination/acetylation network not mapped"]},{"year":null,"claim":"How the various HSPA5 modifications and relocalization events are integrated into a single decision logic—and how each subcellular pool is selectively targeted—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking modification state to ER/cytosol/surface/nuclear partitioning","Structural basis of non-canonical receptor and transcriptional functions undefined","Quantitative rules of BiP-availability sensing of the UPR not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[1,2,3,30]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,2,14,15,32]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[4,5,13]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[25,29]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[33]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[24]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[7,21,28]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,4,6,35]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[7,21,28,29]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[12,23]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[33]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[14]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[4,5,20]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,2,32]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[12,23]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13,18,34]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,21,28,37]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[27,37,15]}],"complexes":[],"partners":["MTJ1","ATF6","IRE1","GPX4","ID2","ITGB1","OTUD3","GP78"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P11021","full_name":"Endoplasmic reticulum chaperone BiP","aliases":["78 kDa glucose-regulated protein","GRP-78","Binding-immunoglobulin protein","BiP","Heat shock protein 70 family protein 5","HSP70 family protein 5","Heat shock protein family A member 5","Immunoglobulin heavy chain-binding protein"],"length_aa":654,"mass_kda":72.3,"function":"Endoplasmic reticulum chaperone that plays a key role in protein folding and quality control in the endoplasmic reticulum lumen (PubMed:2294010, PubMed:23769672, PubMed:23990668, PubMed:28332555). Involved in the correct folding of proteins and degradation of misfolded proteins via its interaction with DNAJC10/ERdj5, probably to facilitate the release of DNAJC10/ERdj5 from its substrate (By similarity). Acts as a key repressor of the EIF2AK3/PERK and ERN1/IRE1-mediated unfolded protein response (UPR) (PubMed:11907036, PubMed:1550958, PubMed:19538957, PubMed:36739529). In the unstressed endoplasmic reticulum, recruited by DNAJB9/ERdj4 to the luminal region of ERN1/IRE1, leading to disrupt the dimerization of ERN1/IRE1, thereby inactivating ERN1/IRE1 (By similarity). Also binds and inactivates EIF2AK3/PERK in unstressed cells (PubMed:11907036). Accumulation of misfolded protein in the endoplasmic reticulum causes release of HSPA5/BiP from ERN1/IRE1 and EIF2AK3/PERK, allowing their homodimerization and subsequent activation (PubMed:11907036). Plays an auxiliary role in post-translational transport of small presecretory proteins across endoplasmic reticulum (ER). May function as an allosteric modulator for SEC61 channel-forming translocon complex, likely cooperating with SEC62 to enable the productive insertion of these precursors into SEC61 channel. Appears to specifically regulate translocation of precursors having inhibitory residues in their mature region that weaken channel gating. May also play a role in apoptosis and cell proliferation (PubMed:26045166) (Microbial infection) Plays an important role in viral binding to the host cell membrane and entry for several flaviruses such as Dengue virus, Zika virus and Japanese encephalitis virus (PubMed:15098107, PubMed:28053106, PubMed:33432092). Acts as a component of the cellular receptor for Dengue virus serotype 2/DENV-2 on human liver cells (PubMed:15098107) (Microbial infection) Acts as a receptor for CotH proteins expressed by fungi of the order mucorales, the causative agent of mucormycosis, which plays an important role in epithelial cell invasion by the fungi (PubMed:20484814, PubMed:24355926, PubMed:32487760). Acts as a receptor for R.delemar CotH3 in nasal epithelial cells, which may be an early step in rhinoorbital/cerebral mucormycosis (RCM) disease progression (PubMed:32487760)","subcellular_location":"Endoplasmic reticulum lumen; Melanosome; Cytoplasm; Cell surface","url":"https://www.uniprot.org/uniprotkb/P11021/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/HSPA5","classification":"Common Essential","n_dependent_lines":1187,"n_total_lines":1208,"dependency_fraction":0.9826158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":4.0},{"gene":"DNAJC7","stoichiometry":4.0},{"gene":"HSPH1","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CKAP2","stoichiometry":0.2},{"gene":"CLASP2","stoichiometry":0.2},{"gene":"COPA","stoichiometry":0.2},{"gene":"DNAJB6","stoichiometry":0.2},{"gene":"GORASP2","stoichiometry":0.2},{"gene":"HSPA4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/HSPA5","total_profiled":1310},"omim":[{"mim_id":"620911","title":"SPASTIC PARAPLEGIA 92, AUTOSOMAL RECESSIVE; SPG92","url":"https://www.omim.org/entry/620911"},{"mim_id":"620875","title":"FIC DOMAIN-CONTAINING PROTEIN ADENYLYLTRANSFERASE; FICD","url":"https://www.omim.org/entry/620875"},{"mim_id":"618061","title":"POLYCYSTIC KIDNEY DISEASE 6 WITH OR WITHOUT POLYCYSTIC LIVER DISEASE; PKD6","url":"https://www.omim.org/entry/618061"},{"mim_id":"617471","title":"SERPIN PEPTIDASE INHIBITOR, CLADE A, MEMBER 12; SERPINA12","url":"https://www.omim.org/entry/617471"},{"mim_id":"617363","title":"TRANSMEMBRANE PROTEIN 132A; TMEM132A","url":"https://www.omim.org/entry/617363"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Cytosol","reliability":"Uncertain"},{"location":"Annulus","reliability":"Uncertain"},{"location":"Mid piece","reliability":"Additional"},{"location":"Principal piece","reliability":"Additional"},{"location":"End piece","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HSPA5"},"hgnc":{"alias_symbol":["BiP"],"prev_symbol":["GRP78"]},"alphafold":{"accession":"P11021","domains":[{"cath_id":"3.30.420.40","chopping":"30-252_332-415","consensus_level":"medium","plddt":95.5884,"start":30,"end":415},{"cath_id":"3.90.640.10","chopping":"254-331","consensus_level":"medium","plddt":97.8554,"start":254,"end":331},{"cath_id":"2.60.34.10","chopping":"422-533","consensus_level":"medium","plddt":85.7409,"start":422,"end":533},{"cath_id":"1.20.1270.10","chopping":"536-633","consensus_level":"high","plddt":91.2298,"start":536,"end":633}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P11021","model_url":"https://alphafold.ebi.ac.uk/files/AF-P11021-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P11021-F1-predicted_aligned_error_v6.png","plddt_mean":90.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HSPA5","jax_strain_url":"https://www.jax.org/strain/search?query=HSPA5"},"sequence":{"accession":"P11021","fasta_url":"https://rest.uniprot.org/uniprotkb/P11021.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P11021/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P11021"}},"corpus_meta":[{"pmid":"15804610","id":"PMC_15804610","title":"The 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{\n      \"year\": 1999,\n      \"finding\": \"BiP/GRP78 binds newly-synthesized proteins as they are translocated into the ER lumen, maintaining them in a folding-competent state; it is an essential component of the ER translocation machinery and plays a role in retrograde transport (ERAD) of aberrant proteins destined for proteasomal degradation.\",\n      \"method\": \"Review synthesizing genetic and biochemical studies in yeast and mammalian cells\",\n      \"journal\": \"Seminars in cell & developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — foundational findings replicated across multiple labs and organisms, multiple orthogonal methods (genetic, biochemical, cell biology)\",\n      \"pmids\": [\"10597629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Purified yeast BiP/Kar2 (ortholog of HSPA5) is active as a homodimer and exhibits intrinsic ATPase activity; the ADP-bound form is more protease-resistant than the ATP-bound form, indicating ATP-dependent conformational changes.\",\n      \"method\": \"Protein purification, ATPase assay, protease susceptibility assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical reconstitution of purified protein with enzymatic assay and conformational analysis\",\n      \"pmids\": [\"1325440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"BiP/GRP78 co-precipitates with amyloid precursor protein (APP) in the ER, transiently interacting with it; expression of an ATPase-dead mutant (T37G) of GRP78 nearly completely blocks APP maturation and reduces secretion of APPs, Aβ40, and Aβ42, demonstrating that GRP78 ATPase activity is required for APP folding and processing.\",\n      \"method\": \"Metabolic labeling, co-immunoprecipitation, ATPase mutant overexpression in HEK293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — co-IP plus active-site mutagenesis in a single rigorous study\",\n      \"pmids\": [\"9748217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Murine BiP/GRP78 physically interacts with the lumenal J domain of the transmembrane protein MTJ1; this interaction stimulates BiP ATPase activity at stoichiometric concentrations and is abolished by the conserved HPD→HPQ substitution in MTJ1, demonstrating MTJ1 is a functional DnaJ co-chaperone for BiP.\",\n      \"method\": \"In vitro ATPase assay, binding studies, site-directed mutagenesis of HPD motif\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"10777498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"BiP/GRP78 binds to ATF6 and retains it in the ER; dissociation of BiP from ATF6 upon ER stress allows ATF6 to translocate to the Golgi for proteolytic activation, identifying BiP as the key sensor that couples ER folding capacity to ATF6 activation.\",\n      \"method\": \"Genetic and biochemical analysis (reviewed mechanistic study)\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic summary of co-IP and functional data from primary studies; review commentary citing the primary experiment\",\n      \"pmids\": [\"12110159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GRP78/BiP controls the activation of the three transmembrane ER stress sensors (IRE1, PERK, ATF6) through a binding-release mechanism: under non-stress conditions BiP keeps sensors inactive; accumulation of unfolded proteins titrates BiP away, freeing sensors to activate the UPR.\",\n      \"method\": \"Promoter assays, mRNA/protein quantification, established mechanistic framework\",\n      \"journal\": \"Methods (San Diego, Calif.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanism replicated across multiple independent labs using reciprocal co-IP and loss-of-function approaches\",\n      \"pmids\": [\"15804610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MDA-7/IL-24 physically interacts with BiP/GRP78 through its C and F helices; the complex localizes in the ER and activates p38 MAPK and GADD gene expression, leading to cancer-selective apoptosis.\",\n      \"method\": \"Deletion and mutational analysis, co-immunoprecipitation, subcellular localization\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — rationally designed mutagenesis plus co-IP in cancer cells, single lab\",\n      \"pmids\": [\"16912197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cell-surface GRP78 functions as a signaling receptor: binding of activated α2-macroglobulin activates AKT to suppress apoptosis and upregulates NF-κB; interaction with Cripto nullifies TGF-β/Smad2/3 signaling; interaction with Par-4 or plasminogen kringle 5 promotes apoptosis; association with tissue factor inhibits procoagulant activity.\",\n      \"method\": \"Cell-surface binding assays, signaling pathway analysis, co-immunoprecipitation\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple binding partners and functional outcomes established by independent labs, though described in a review\",\n      \"pmids\": [\"19331544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cab45S specifically binds to the nucleotide-binding domain (NBD) of GRP78/BiP and stabilizes the GRP78-IRE1 interaction, thereby inhibiting ER stress-induced IRE1 activation and downstream JNK phosphorylation and apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, domain-mapping, siRNA knockdown, functional apoptosis assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP with domain mapping and functional rescue, single lab\",\n      \"pmids\": [\"24810055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GP78 (E3 ubiquitin ligase) interacts with the C-terminal region of HSPA5 and mediates its polyubiquitination at lysine 447 (K447), targeting HSPA5 for proteasomal degradation; HDAC6 deacetylates HSPA5 at K353, which is required for GP78-mediated ubiquitination at K447.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, site-directed mutagenesis (K447, K353), HDAC6 knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-specific mutagenesis identifying ubiquitination and acetylation sites, co-IP, functional assays in a single rigorous study\",\n      \"pmids\": [\"26119938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HDAC6 deacetylation of HSPA5 at K633 promotes its secretion into exosomes via the multivesicular body (MVB) pathway; acetylated HSPA5 (mimicked by K633Q mutation) binds VPS34 and prevents MVB sorting, blocking secretion.\",\n      \"method\": \"HDAC inhibitor treatment, acetylation-mimetic mutagenesis (K633Q), VPS34 co-IP, exosome fractionation\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus co-IP and fractionation, single lab, two orthogonal methods\",\n      \"pmids\": [\"27460191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FOXM1 directly binds to and transactivates the HSPA5 promoter at a site mapped between −1019 and −1012 bp, upregulating HSPA5 expression; HSPA5 depletion attenuates FOXM1-driven colorectal cancer cell migration and invasion, acting downstream through cell-surface HSPA5 and MMP2/9 activity.\",\n      \"method\": \"Promoter-binding assay, chromatin immunoprecipitation, luciferase reporter, siRNA knockdown, invasion assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and promoter mapping plus functional knockdown, single lab\",\n      \"pmids\": [\"27034162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"N-terminal arginylation (Nt-arginylation) of HSPA5 by ATE1 arginyltransferase generates R-HSPA5 in the cytosol; R-HSPA5's N-terminal arginine is recognized by the ZZ domain of SQSTM1/p62, inducing SQSTM1 conformational change, self-polymerization, and LC3 interaction, thereby directing misfolded protein cargoes to autophagosomes for lysosomal degradation.\",\n      \"method\": \"In vitro arginylation, co-immunoprecipitation, autophagy flux assays, domain-specific interaction mapping\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution of arginylation, co-IP showing R-HSPA5/SQSTM1 interaction, functional autophagy assays in a single focused study\",\n      \"pmids\": [\"26797053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HSPA5 binds directly to GPX4 protein and protects it from degradation; ATF4-induced HSPA5 upregulation stabilizes GPX4 protein levels, thereby inhibiting lipid peroxidation and conferring ferroptosis resistance in pancreatic ductal adenocarcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA/pharmacological inhibition, GPX4 protein stability assays, in vitro and in vivo ferroptosis assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP, loss-of-function, replicated by multiple subsequent studies with orthogonal approaches\",\n      \"pmids\": [\"28130223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GRP78 localizes to the mitochondria-associated ER membrane (MAM) where it folds steroidogenic acute regulatory protein (StAR); GRP78 knockdown drastically reduces StAR expression and steroidogenic activity, identifying GRP78 as an acute regulator of steroidogenesis at the MAM.\",\n      \"method\": \"GRP78 knockdown, subcellular fractionation (MAM isolation), StAR activity assays, protein folding experiments\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with defined functional readout and subcellular fractionation, single lab\",\n      \"pmids\": [\"28275724\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GRP78/BiP directly interacts with misfolded PrPSc in vitro; recombinant GRP78 incubated with PrPSc reduces protease-resistant PrPSc in a dose-dependent manner; in cells, BiP expression levels inversely correlate with prion replication; in vivo, reduced GRP78 expression accelerates prion pathogenesis.\",\n      \"method\": \"In vitro incubation of recombinant GRP78 with PrPSc, cell culture prion replication assay, co-immunoprecipitation, conditional knockout mouse model\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus cell and in vivo loss-of-function, multiple orthogonal methods\",\n      \"pmids\": [\"28333162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MUL1 (mitochondrial E3 ubiquitin ligase) directly ubiquitinates HSPA5 at lysine 446 (K446) via K48-linked ubiquitin chains, promoting HSPA5 proteasomal degradation; this leads to lysosomal inhibition and cytotoxicity in head and neck cancer cells.\",\n      \"method\": \"K446 site mutagenesis, ubiquitination assays, CRISPR/Cas9 MUL1 knockout, xenograft model\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-specific mutagenesis, K48-linkage specificity, CRISPR KO validation in a single rigorous study\",\n      \"pmids\": [\"29260979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The deubiquitylase OTUD3 interacts with GRP78, removes its ubiquitin chains, and stabilizes GRP78 protein; OTUD3 knockdown reduces GRP78 protein levels and suppresses lung cancer cell growth and migration.\",\n      \"method\": \"Co-immunoprecipitation, deubiquitylation assay, OTUD3 knockdown, mouse lung adenocarcinoma model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP, deubiquitylation assay, and in vivo mouse model, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31266968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DHA-induced ER stress activates the PERK→ATF4→HSPA5 pathway in glioma cells; HSPA5 upregulation then increases GPX4 expression and activity, neutralizing lipid peroxidation and protecting cells from ferroptosis via a negative feedback loop.\",\n      \"method\": \"siRNA knockdown of PERK/ATF4/HSPA5, GPX4 activity assays, ROS/lipid peroxidation measurement, in vitro and in vivo models\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway epistasis via siRNA knockdown with functional readouts, single lab\",\n      \"pmids\": [\"31519193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BiP/GRP78 overexpression strengthens circadian rhythm oscillation amplitude; adequate BiP levels preemptively prevent ER stress in collagen-synthesizing fibroblasts, thereby preventing UPR activation and maintaining circadian gene expression.\",\n      \"method\": \"BiP overexpression, chemical chaperone treatment, circadian reporter assays in fibroblasts and tendon tissue\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression gain-of-function with defined phenotypic (circadian) readout, single lab\",\n      \"pmids\": [\"30888851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Inadequate BiP availability is the defining molecular event of proteostatic ER stress: conditions that prevent restoration of excess BiP over unfolded substrate (μs heavy chain) — including abrogation of HRD1-mediated ERAD or the ATF6α branch of UPR — lead to proteotoxicity; removal of the BiP-sequestering CH1 domain from µs tolerates the same conditions without toxicity.\",\n      \"method\": \"Inducible expression of secretory IgM heavy chain, genetic ablation of ERAD (HRD1 KO) and UPR branches, electron microscopy\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with multiple UPR/ERAD branch knockouts and substrate engineering, multiple orthogonal approaches\",\n      \"pmids\": [\"30869076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cell-surface GRP78 (csGRP78) interacts with integrin β1 on kidney mesangial cells under high-glucose conditions, activating focal adhesion kinase and downstream PI3K/AKT signaling, which drives extracellular matrix protein synthesis; both N- and C-termini of csGRP78 are required for this profibrotic response.\",\n      \"method\": \"Cell-surface biotinylation, co-immunoprecipitation of csGRP78 with integrin β1, siRNA knockdown, signaling assays, diabetic mouse models\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, domain mutagenesis, in vivo diabetic model, multiple orthogonal methods in one study\",\n      \"pmids\": [\"30914477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Intracellular (not cell-surface) BiP/GRP78 mediates thrombin-induced Ca2+ signaling and endothelial permeability, as well as NF-κB-dependent upregulation of VCAM-1, ICAM-1, IL-6, and IL-8; specific inactivation of intracellular BiP by the protease SubAB or a dominant-negative mutant abolishes these responses in vitro and reduces LPS-induced lung injury in vivo.\",\n      \"method\": \"SubAB-mediated selective BiP cleavage, dominant-negative BiP gene transfer, LPS-inhalation mouse model, Ca2+ imaging, permeability assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific enzymatic inactivation tool (SubAB), DN mutant, and in vivo model; multiple orthogonal approaches distinguishing intra- vs. surface pools\",\n      \"pmids\": [\"30765717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ATE1-mediated arginylation of HSPA5 (generating R-HSPA5) is induced by ROS upon proteasome inhibition; R-HSPA5 binds K48-linked polyubiquitinated AKT (sequentially ubiquitinated at K284 then K214 by MUL1) and escorts it to the autophagy-lysosome pathway for degradation; USP7 antagonizes this by deubiquitinating AKT.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitin linkage analysis, ATE1 overexpression, MUL1 knockout cells, autophagy flux inhibitors\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, KO cell validation, linkage-specific ubiquitin analysis, and autophagy inhibitors; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"32164484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HSPA5 interacts with negatively charged phospholipids (POPS, cardiolipin) via both its N- and C-terminal domains; membrane binding promotes HSPA5 oligomerization through intermolecular disulfide bonds, with the N-terminal domain playing a critical role in this process.\",\n      \"method\": \"Liposome binding assays with purified full-length and truncated HSPA5, disulfide bond analysis\",\n      \"journal\": \"Cell stress & chaperones\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein and defined lipid compositions, single lab\",\n      \"pmids\": [\"32725381\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HSPA5/GRP78 mediates Pneumocystis carinii binding and colonization of lung epithelial cells; affinity chromatography identified HSPA5 as the receptor, and CHO cells overexpressing HSPA5 bound Pc organisms more than parental cells, confirming direct Pc-HSPA5 protein interaction.\",\n      \"method\": \"Affinity chromatography, overexpression binding assay in CHO cells, primary rat airway epithelial cells\",\n      \"journal\": \"Journal of medical microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — affinity chromatography plus receptor overexpression binding confirmation, single lab\",\n      \"pmids\": [\"30328808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NLRP6 binds to GRP78 through its Pyrin domain (interaction mediated via the SBD domain of GRP78), promotes GRP78 polyubiquitination, and thereby suppresses gastric cancer cell proliferation, cell cycle progression, migration, and tumorigenesis.\",\n      \"method\": \"Flag-tagged immunoprecipitation, LC/MS proteomics, ubiquitination assays, domain mapping, overexpression/knockdown, xenograft model\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain mapping, ubiquitination assay, and in vivo model, single lab\",\n      \"pmids\": [\"32682010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HSPA5/GRP78 is required for KrasG12D-driven lung adenocarcinoma initiation and progression; GRP78 haploinsufficiency in floxed mouse models suppresses KrasG12D-mediated lung tumor progression, prolongs survival, and GRP78 knockdown in human lung cancer cells (KrasG12D/+) activates UPR and apoptotic markers.\",\n      \"method\": \"Conditional knockout mouse model (floxed Grp78 × KrasLSL-G12D), siRNA knockdown in human lung cancer cells, tumor histology, survival analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional in vivo knockout with genetic epistasis to KrasG12D plus human cell knockdown; multiple orthogonal methods\",\n      \"pmids\": [\"33931739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GRP78 knockdown in macrophages promotes M1 differentiation and suppresses M2 polarization via the JAK/STAT pathway; GRP78 regulates IGF-1 secretion by macrophages and, in response to IGF-1, GRP78 translocates to the plasma membrane and associates with the IGF-1 receptor to promote M2 polarization.\",\n      \"method\": \"GRP78 knockdown, cytokine secretion assay, JAK/STAT pathway analysis, IGF-1 neutralization, subcellular fractionation, co-immunoprecipitation, conditioned medium experiments\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown, co-IP, and neutralization experiments in vitro and in vivo, single lab\",\n      \"pmids\": [\"34713304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SARS-CoV-2 spike protein physically interacts with cell-surface GRP78, promoting binding and accumulation in ACE2-expressing cells; GRP78 expression in adipose tissue is upregulated by hyperinsulinemia partly through the XBP-1s transcription factor.\",\n      \"method\": \"Co-immunoprecipitation of spike protein with GRP78, cell binding assays, gene expression analysis in adipocytes\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP of spike-GRP78 plus mechanistic XBP-1s pathway, single lab\",\n      \"pmids\": [\"34615619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HYPE/FicD AMPylates BiP/GRP78 at Thr518 (structurally preferred) and Thr366; AMPylation at Thr366 vs. Thr518 differentially affects BiP ATPase activity; HYPE preferentially de-AMPylates wild-type adenylylated BiP; HYPE does not adenylylate UPR accessory proteins like ERdJ6.\",\n      \"method\": \"In vitro AMPylation kinetic assays, molecular docking, ATPase activity assays, binding efficiency measurements\",\n      \"journal\": \"Cell stress & chaperones\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with site mutagenesis, kinetic analysis, and structural docking in a single rigorous study\",\n      \"pmids\": [\"33942205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HspA5/GRP78 directly binds the RNA-recognition motif (RRM) domain of TDP-43 in a pulldown assay using recombinant proteins; overexpression of HspA5 in a Drosophila TDP-43 toxicity model rescues TDP-43-induced lethality, indicating HspA5 mitigates TDP-43 proteotoxicity.\",\n      \"method\": \"BioID proximity labeling, recombinant protein pulldown, Drosophila overexpression rescue assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — recombinant protein interaction plus in vivo Drosophila rescue, single lab\",\n      \"pmids\": [\"35581326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GRP94 acts upstream of BiP in ER protein remodeling under strong denaturing conditions: Grp94 binds misfolded proteins in an ATP-independent manner to prevent aggregation, then releases them via ATP binding (without hydrolysis) for subsequent refolding by the BiP system; direct Grp94-BiP interaction is not required for client transfer.\",\n      \"method\": \"In vitro refolding assays with purified proteins, ATP binding/hydrolysis mutants, aggregation prevention assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with defined ATP mutants and ordered epistasis, single lab but rigorous biochemistry\",\n      \"pmids\": [\"35905823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Nuclear GRP78 regulates gene expression by interacting with and inhibiting the transcriptional repressor ID2, promoting expression of genes involved in cell migration and invasion; a nuclear localization signal in GRP78 is critical for its stress-induced translocation to the nucleus.\",\n      \"method\": \"NLS mutagenesis, nuclear fractionation, co-immunoprecipitation of GRP78-ID2, gene expression profiling, cancer cell migration assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — NLS mutagenesis, co-IP, nuclear fractionation, and functional migration assays with multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"37487081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"EP300 acetyltransferase acetylates HSPA5 at K353, causing loss of its ability to inhibit lipid peroxidation and ferroptotic cell death in pancreatic cancer cells; HDAC6 opposes this by deacetylating HSPA5, limiting ferroptosis sensitivity.\",\n      \"method\": \"In vitro acetylation assay, K353 site mutagenesis, EP300 and HDAC6 genetic/pharmacological manipulation, ferroptosis assays (lipid ROS, cell death)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-specific mutagenesis and enzymatic acetylation assay, single lab\",\n      \"pmids\": [\"37696842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ZDHHC9 palmitoylates GRP78/BiP at cysteine 420 (Cys420), enhancing BiP protein stability and maintaining its ER localization; this palmitoylation inhibits the unfolded protein response and promotes bladder cancer progression and chemoresistance.\",\n      \"method\": \"Co-immunoprecipitation of ZDHHC9-Bip, palmitoylation assay at Cys420, ZDHHC9 knockdown, UPR marker analysis, subcellular localization\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, site-specific palmitoylation at Cys420, functional UPR and localization assays, single lab\",\n      \"pmids\": [\"39002690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HDAC1 binds to the Grp78 promoter under non-stress conditions (demonstrated by ChIP) and represses its transcription; ER stress causes HDAC1 dissociation from the promoter, allowing GRP78 induction; overexpression of GRP78 confers resistance to HDAC inhibitor-induced apoptosis, while GRP78 knockdown sensitizes cancer cells.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), promoter mutational analysis, HDAC1 overexpression/siRNA knockdown, apoptosis assays\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP identifying direct promoter occupancy, mutagenesis, and functional gain/loss-of-function in single study\",\n      \"pmids\": [\"19417144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GRP78 promotes PI3K/AKT/mTOR oncogenic signaling in the hematopoietic system; heterozygous knockout of GRP78 in PTEN-null mice restores the hematopoietic stem cell population, suppresses leukemic blast expansion, and potently inhibits AKT/mTOR activation in PTEN-null BM cells.\",\n      \"method\": \"Biallelic conditional knockout mouse model (GRP78 × PTEN), flow cytometry, AKT/mTOR phosphorylation assays, GRP78 knockdown in leukemia cell lines\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional KO genetic epistasis replicated in cell lines, multiple methods\",\n      \"pmids\": [\"21937694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"IGF-1 receptor signaling regulates GRP78 expression via the PI3K/AKT/mTORC1 axis (independently of FOXO1 and the canonical UPR); IGF-1 receptor-null MEFs express 80% less GRP78 but remain capable of activating the UPR when needed.\",\n      \"method\": \"IGF-1R knockout and overexpression MEFs, mTORC1 and PI3K inhibitors, FOXO1 knockdown, calorie restriction in mice\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO/OE plus pharmacological inhibitors with defined pathway exclusion, single lab\",\n      \"pmids\": [\"22422508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"BiP/GRP78 co-immunoprecipitates with AMPA receptor subunits (GluR1, GluR2/3, GluR4) from rat forebrain membranes; both BiP and calnexin are detected in dendrites of hippocampal pyramidal neurons co-localizing with AMPA receptor subunits, consistent with an ER chaperone role in AMPA receptor assembly.\",\n      \"method\": \"Co-immunoprecipitation from native brain membranes, western blotting, immunocytochemistry\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP from native tissue plus anatomical co-localization, single lab\",\n      \"pmids\": [\"10461883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Hspa5/GRP78 is essential for pronephros (kidney) formation in Xenopus; knockdown with morpholino antisense oligonucleotides inhibits pronephric marker gene expression (lhx1, pax2, atp1b1) by attenuating retinoic acid (RA) signaling and reducing Lhx1 expression; co-injection of lhx1 mRNA partially rescues the phenotype.\",\n      \"method\": \"Morpholino knockdown in Xenopus embryos, animal cap explant assay, rescue by mRNA injection, retinoic acid-responsive gene expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino knockdown with mRNA rescue and epistasis to RA-Lhx1 pathway, single lab\",\n      \"pmids\": [\"25398881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"BiP/GRP78 is critical for myelinating cell survival; conditional knockout of BiP in oligodendrocytes causes tremors, ataxia, and premature death in developing mice, and triggers oligodendrocyte loss and myelin abnormalities; adult knockout produces severe neurological symptoms; BiP haploinsufficiency exacerbates EAE-induced oligodendrocyte loss.\",\n      \"method\": \"Oligodendrocyte-specific conditional BiP knockout mouse, Schwann cell-specific conditional BiP knockout, EAE model, neuropathology\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional KO in multiple cell types with replicated severe phenotypes and disease model epistasis\",\n      \"pmids\": [\"26631473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Increased BiP expression in Alzheimer's disease model (Tg2576) brains induces tau hyperphosphorylation by activating GSK-3β and increasing the association of tau with GSK-3β; SIL1 (BiP co-chaperone) deficiency is observed in Tg2576 brains and under ER stress, and SIL1 overexpression reduces BiP-induced tau hyperphosphorylation and GSK-3β activation.\",\n      \"method\": \"Bip-EGFP transfection in HEK293/tau cells, co-immunoprecipitation of tau-GSK3β, SIL1 overexpression, transgenic mouse brain analysis\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and overexpression studies with defined kinase activation readout, single lab\",\n      \"pmids\": [\"25575678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GRP78/BiP is recruited into androgen receptor (AR) inclusions in embryonic stem cells (ESCs) upon androgen stimulation; GRP78 dissociates from ATF6 and instead acts as an AR-interacting protein; GRP78 overexpression suppresses AR aggregate ubiquitination and ameliorates misfolded AR-mediated cytopathology, while GRP78 knockdown increases AR aggregates and caspase-3 activity.\",\n      \"method\": \"Co-immunoprecipitation of GRP78-AR, immunofluorescence co-localization, GRP78 overexpression/knockdown, ubiquitination assay, caspase-3 activity\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus gain/loss-of-function with functional readouts, single lab\",\n      \"pmids\": [\"23618905\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HSPA5/GRP78/BiP is an ER-luminal HSP70-family chaperone with intrinsic ATPase activity that, via ATP-driven conformational cycling stimulated by DnaJ-type co-chaperones (e.g., MTJ1), binds and folds nascent secretory proteins during translocation, retains misfolded proteins for ERAD, and sequesters the three UPR transmembrane sensors (IRE1, PERK, ATF6) in their inactive states until titrated away by unfolded protein load; under chronic or severe ER stress, HSPA5 is subject to multiple post-translational modifications—AMPylation at Thr518/Thr366 by HYPE/FicD, ubiquitination at K447 by GP78/NLRP6-promoted pathways (opposed by OTUD3 deubiquitylase), and acetylation at K353 by EP300 (opposed by HDAC6) or at K633 (controlling exosomal secretion)—that regulate its activity, stability, and trafficking; additionally, HSPA5 is arginylated at its N-terminus by ATE1 upon cytosolic relocalization, enabling it to activate SQSTM1/p62-dependent selective autophagy of misfolded proteins; beyond the ER, HSPA5 translocates to the mitochondria-associated membrane to fold StAR and regulate steroidogenesis, to the cell surface where it acts as a receptor for diverse ligands (α2-macroglobulin, Cripto, integrin β1, viral proteins) and activates PI3K/AKT and JAK/STAT signaling, and to the nucleus where it binds and inhibits the transcriptional repressor ID2 to promote an invasive gene expression program, collectively making HSPA5 a multifunctional stress-response hub whose inhibition suppresses ferroptosis resistance (via GPX4 stabilization), oncogenic AKT/mTOR signaling, and tumor progression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HSPA5 (BiP/GRP78) is the principal ER-luminal HSP70-family chaperone that couples protein folding capacity to cellular stress responses [#0, #5]. It is an ATP-driven machine that binds nascent and unfolded secretory proteins, maintaining them in a folding-competent state during ER translocation and triaging aberrant proteins to ERAD [#0]; its intrinsic ATPase activity drives conformational cycling between protease-resistant ADP-bound and ATP-bound states [#1], and this cycle is stimulated by DnaJ-type co-chaperones such as the transmembrane protein MTJ1 [#3], with GRP94 acting upstream to hand off misfolded clients to the BiP system [#32]. ATPase-competent HSPA5 is required for folding and maturation of specific clients including APP [#2], and inadequate BiP availability relative to unfolded substrate is the defining molecular trigger of proteotoxic ER stress [#20]. Centrally, HSPA5 governs the unfolded protein response by binding and sequestering the three transmembrane sensors IRE1, PERK, and ATF6 in their inactive states until accumulating unfolded protein titrates it away, releasing the sensors and coupling folding capacity to ATF6, PERK, and IRE1 activation [#4, #5]. HSPA5 abundance and activity are tuned by an extensive post-translational regulatory network: AMPylation at Thr518/Thr366 by HYPE/FicD modulates its ATPase activity [#30]; ubiquitination at K447/K446 by GP78, MUL1, and NLRP6-promoted pathways drives proteasomal degradation [#9, #16, #26], opposed by the deubiquitylase OTUD3 [#17]; acetylation at K353 by EP300 and at K633, controlled by HDAC6, regulates ferroptosis sensitivity and exosomal secretion [#9, #10, #34]; and palmitoylation at Cys420 by ZDHHC9 stabilizes the protein and its ER localization [#35]. Beyond the ER, HSPA5 acquires distinct functions through relocalization: cytosolic N-terminal arginylation by ATE1 generates R-HSPA5, which engages the SQSTM1/p62 ZZ domain to direct misfolded cargoes—and ubiquitinated AKT—to selective autophagy [#12, #23]; it localizes to the mitochondria-associated membrane to fold StAR and support steroidogenesis [#14]; it functions at the cell surface as a signaling receptor for ligands including integrin β1, IGF-1R, α2-macroglobulin, and viral spike proteins, activating PI3K/AKT and JAK/STAT pathways [#7, #21, #28, #29]; and it translocates to the nucleus to bind and inhibit the transcriptional repressor ID2, driving an invasive gene expression program [#33]. These activities make HSPA5 an oncogenic dependency that stabilizes GPX4 to confer ferroptosis resistance [#13, #18], promotes PI3K/AKT/mTOR signaling and Kras-driven tumorigenesis [#27, #37], and is essential for myelinating cell survival and tissue development [#41].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that the BiP ortholog is an autonomous ATPase whose nucleotide state drives conformational change, the biochemical basis for chaperone cycling.\",\n      \"evidence\": \"Purification of yeast Kar2 with ATPase and protease-susceptibility assays\",\n      \"pmids\": [\"1325440\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how ATP cycling couples to client binding in the mammalian protein\", \"Co-chaperone requirements unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined the core chaperone role: BiP binds nascent proteins entering the ER and triages aberrant ones for ERAD, framing it as essential to ER proteostasis.\",\n      \"evidence\": \"Synthesis of genetic and biochemical studies in yeast and mammalian cells; co-IP with AMPA receptor subunits from brain\",\n      \"pmids\": [\"10597629\", \"10461883\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish substrate specificity rules\", \"Native client repertoire only partially defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated that BiP ATPase activity is functionally required for folding of a specific client, linking the enzymatic cycle to physiological maturation.\",\n      \"evidence\": \"ATPase-dead T37G mutant overexpression and co-IP with APP in HEK293 cells\",\n      \"pmids\": [\"9748217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single client; generality to other secretory proteins not tested here\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified MTJ1 as a functional DnaJ co-chaperone that stimulates BiP ATPase, explaining how BiP activity is spatially and substrate-directed.\",\n      \"evidence\": \"In vitro ATPase and binding assays with HPD-motif mutagenesis\",\n      \"pmids\": [\"10777498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of ER J-proteins coordinating BiP not enumerated\", \"Nucleotide exchange factor role separate\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Consolidated the binding-release model in which BiP sequesters IRE1, PERK, and ATF6 and is titrated away by unfolded load, establishing BiP as the master UPR sensor.\",\n      \"evidence\": \"Co-IP, loss-of-function, and promoter/expression assays across labs; ATF6 retention/dissociation mechanism\",\n      \"pmids\": [\"15804610\", \"12110159\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether sensor regulation is purely competitive or allosteric not fully resolved\", \"Stoichiometry of BiP across the three sensors unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Revealed that cell-surface GRP78 acts as a multifunctional signaling receptor and that its promoter is repressed by HDAC1, expanding GRP78 beyond an ER chaperone.\",\n      \"evidence\": \"Cell-surface binding/signaling assays with multiple ligands; ChIP of HDAC1 on the Grp78 promoter; Cab45S domain-mapping co-IP\",\n      \"pmids\": [\"19331544\", \"19417144\", \"24810055\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of GRP78 surface translocation not defined\", \"Many receptor functions described in review without unified structural model\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed HSPA5 stability is set by competing ubiquitin ligases and deacetylation, establishing post-translational control of chaperone levels.\",\n      \"evidence\": \"Site-specific mutagenesis (K447, K353), GP78 ubiquitination assays, HDAC6 knockdown\",\n      \"pmids\": [\"26119938\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological triggers selecting degradation vs. stabilization unclear\", \"Crosstalk between K353 acetylation and other modifications not mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined acetylation-controlled exosomal secretion and FOXM1-driven transcriptional and cytosolic arginylation routes, broadening HSPA5 output to autophagy and intercellular signaling.\",\n      \"evidence\": \"K633Q mimetic mutagenesis with VPS34 co-IP and exosome fractionation; ChIP and promoter mapping of FOXM1; in vitro arginylation and SQSTM1 ZZ-domain interaction with autophagy flux\",\n      \"pmids\": [\"27460191\", \"27034162\", \"26797053\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cytosolic relocalization is triggered remains partially defined\", \"In vivo relevance of exosomal HSPA5 not established here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected HSPA5 to ferroptosis resistance and to extra-ER folding roles, establishing it as a stabilizer of GPX4 and a MAM steroidogenic factor.\",\n      \"evidence\": \"Co-IP and GPX4 stability assays in PDAC; MAM fractionation and StAR folding with knockdown; in vitro and in vivo PrPSc clearance\",\n      \"pmids\": [\"28130223\", \"28275724\", \"28333162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which HSPA5 protects GPX4 from degradation not structurally defined\", \"MAM targeting signal unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated genetic and physiological consequences of BiP availability across ferroptosis feedback, fibrosis, vascular permeability, circadian rhythm, and the central requirement of excess BiP to avoid proteotoxicity.\",\n      \"evidence\": \"PERK→ATF4→HSPA5→GPX4 epistasis; csGRP78–integrin β1 co-IP and diabetic models; SubAB selective cleavage and LPS lung injury; BiP overexpression circadian assays; IgM heavy-chain proteostasis with HRD1/ATF6 ablation\",\n      \"pmids\": [\"31519193\", \"30914477\", \"30765717\", \"30888851\", \"30869076\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinct intracellular vs. surface pools incompletely separated mechanistically\", \"How BiP excess is sensed quantitatively not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved AMPylation and arginylation as conditional activity switches and added membrane-lipid binding and chaperone hierarchy, refining how HSPA5 is reprogrammed under stress.\",\n      \"evidence\": \"In vitro AMPylation kinetics at Thr518/Thr366 by HYPE; R-HSPA5 escorting ubiquitinated AKT to autophagy in MUL1-KO cells; liposome binding/oligomerization assays; GRP94→BiP client-transfer epistasis; NLRP6 domain-mapped ubiquitination\",\n      \"pmids\": [\"33942205\", \"32164484\", \"32725381\", \"35905823\", \"32682010\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of AMPylation site selectivity unclear\", \"Lipid-binding role in surface translocation not directly linked\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established HSPA5 as an oncogenic dependency and immune/viral interaction node, showing genetic requirement for Kras-driven tumors, macrophage polarization, and SARS-CoV-2 spike binding.\",\n      \"evidence\": \"Conditional Grp78 KO × KrasLSL-G12D models with human cell knockdown; macrophage knockdown with JAK/STAT and IGF-1R co-IP; spike–GRP78 co-IP\",\n      \"pmids\": [\"33931739\", \"34713304\", \"34615619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether tumor dependency reflects ER chaperone or surface/signaling functions not separated\", \"Spike–GRP78 contribution to infection in vivo not quantified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified nuclear GRP78 as a direct regulator of transcription via ID2 inhibition and refined acetylation control of ferroptosis, completing a picture of compartment-specific functions.\",\n      \"evidence\": \"NLS mutagenesis, nuclear fractionation, GRP78–ID2 co-IP, migration assays; EP300/HDAC6 acetylation at K353 with ferroptosis readouts\",\n      \"pmids\": [\"37487081\", \"37696842\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal triggering nuclear translocation incompletely defined\", \"Direct DNA-binding vs. cofactor-only role of nuclear GRP78 unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Added palmitoylation as a stability/localization switch, showing ZDHHC9 modification retains BiP in the ER and suppresses UPR to promote cancer chemoresistance.\",\n      \"evidence\": \"ZDHHC9–BiP co-IP, Cys420 palmitoylation assay, knockdown, UPR and localization analysis\",\n      \"pmids\": [\"39002690\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; depalmitoylase counter-enzyme not identified\", \"Interplay with ubiquitination/acetylation network not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the various HSPA5 modifications and relocalization events are integrated into a single decision logic—and how each subcellular pool is selectively targeted—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking modification state to ER/cytosol/surface/nuclear partitioning\", \"Structural basis of non-canonical receptor and transcriptional functions undefined\", \"Quantitative rules of BiP-availability sensing of the UPR not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [1, 2, 3, 30]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 2, 14, 15, 32]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [4, 5, 13]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [25, 29]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [24]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [7, 21, 28]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 4, 6, 35]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [7, 21, 28, 29]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [12, 23]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [33]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [4, 5, 20]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 2, 32]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [12, 23]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13, 18, 34]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 21, 28, 37]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [27, 37, 15]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MTJ1\", \"ATF6\", \"IRE1\", \"GPX4\", \"ID2\", \"ITGB1\", \"OTUD3\", \"GP78\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}