| 1993 |
gp96/GRP94 contains ATP-binding cassettes, binds ATP, and possesses Mg2+-dependent ATPase activity; gp96 preparations also contain tightly bound peptides elutable by acid extraction, consistent with roles in chaperoning antigenic peptides and facilitating MHC class I–peptide assembly in the ER lumen. |
In vitro ATPase assay, ATP-binding cassette identification, acid elution of bound peptides |
The EMBO journal |
High |
8344253
|
| 1994 |
GRP94 resides within cardiac sarcoplasmic reticulum vesicles as a soluble luminal Ca2+-binding protein and is phosphorylated in vitro by casein kinase II at two or more sites near the ends of the molecule. |
Subcellular fractionation, co-sedimentation with SR markers, in vitro kinase assay, cDNA cloning |
The Journal of biological chemistry |
Medium |
8119936
|
| 1995 |
Purified GRP94 (grp94/endoplasmin) autophosphorylates itself on serine and threonine residues; autophosphorylation is activated by micromolar calcium, uses both ATP and GTP, and persists in immunoprecipitates and in renatured SDS-PAGE-purified protein; the N-terminal 85 kDa fragment binds ATP-agarose but does not autophosphorylate. |
In vitro autophosphorylation assay with purified protein, immunoprecipitation, limited proteolysis, ATP-agarose binding |
The Journal of biological chemistry |
High |
7890776
|
| 1996 |
An immunodominant peptide of vesicular stomatitis virus (VSV N52-59) endogenously associates with gp96 in VSV-infected cells, demonstrating that gp96 acts as a peptide carrier in a well-defined viral model system. |
Biochemical purification and mass spectrometric/sequence characterization of gp96-bound peptides from infected cells |
Proceedings of the National Academy of Sciences of the United States of America |
High |
8650232
|
| 1996 |
Purified GRP94 exists as a dimer of noncovalently associated subunits and is a soluble, lumenal protein within the ER; N-linked glycosylation accounts for its molecular weight heterogeneity. |
Protein purification, native PAGE, 2D non-reducing/reducing PAGE, alkali/detergent extraction |
Protein expression and purification |
Medium |
9172775
|
| 1999 |
GRP94 undergoes receptor-mediated endocytosis in macrophages via a cell surface receptor distinct from the mannose/fucose receptor; internalized GRP94 co-localizes predominantly with transferrin-positive early endosomes and is not rapidly trafficked to lysosomes. |
Fluorescent protein uptake assay, subcellular co-localization by confocal microscopy, competitive inhibition with mannan and dimethylamiloride |
Journal of cell science |
Medium |
10362546
|
| 2000 |
CD91 (alpha2-macroglobulin receptor/LRP) is a cell-surface receptor for gp96 on antigen-presenting cells; CD91 binds gp96 directly (not through another ligand), and anti-CD91 antibodies or the CD91 ligand alpha2-macroglobulin inhibit re-presentation of gp96-chaperoned antigenic peptides. |
Direct binding assay, antibody blocking of gp96 uptake and peptide re-presentation, competitive inhibition with alpha2-macroglobulin |
Nature immunology |
High |
11248808
|
| 2000 |
Cell-surface targeting of gp96 on dendritic cells induces their maturation (upregulation of MHC I, MHC II, CD80, CD86, CD40) and secretion of IL-1β, IL-12, and MCP-1; surface-expressed gp96 on tumor cells renders them regressive via a T-lymphocyte-dependent mechanism. |
Genetic targeting of gp96 to cell surface, flow cytometry for DC maturation markers, cytokine ELISA, in vivo tumor regression assay |
Journal of immunology |
Medium |
11739487
|
| 2001 |
GRP94 is released into the extracellular space following virally induced or mechanical (freeze/thaw) cell death but not apoptotic cell death; released GRP94 retains antigenicity and elicits ovalbumin-specific T-cell hybridoma activation in a dose-dependent manner. |
Cell death assays, ELISA/immunoblot for released GRP94, T-cell hybridoma activation assay |
The Journal of biological chemistry |
Medium |
11279246
|
| 2002 |
Receptor-internalized GRP94 is trafficked to a Rab5a/CD1/transferrin-negative, Fc receptor- and MHC class I-positive endocytic compartment (not the ER); peptide transfer from GRP94 to MHC class I occurs at a post-ER compartment accessed by mature MHC class I molecules. |
Receptor-mediated endocytosis trafficking assay, immunofluorescence co-localization, kinetic peptide re-presentation assay with 25-D1.16 antibody under conditions of inhibited MHC I synthesis |
Traffic |
Medium |
11967129
|
| 2002 |
CD91 is not the primary receptor mediating GRP94 cell-surface binding, receptor-mediated endocytosis, or peptide re-presentation in APCs; excess activated alpha2-macroglobulin or receptor-associated protein (pan-CD91 antagonist) did not affect GRP94 uptake or cross-presentation, identifying a CD91-independent pathway. |
Competitive binding with alpha2-macroglobulin and receptor-associated protein, GRP94 uptake and peptide re-presentation assays in macrophages/dendritic cells |
Journal of immunology |
Medium |
11970968
|
| 2003 |
Scavenger receptor class-A (SR-A) serves as a primary receptor for gp96 (and calreticulin) recognition and internalization on macrophages and dendritic cells; gp96 internalization and peptide re-presentation are inhibited by the SR-A inhibitor fucoidan, and macrophages from SR-A−/− mice are substantially impaired in gp96 binding and uptake; ectopic SR-A expression in HEK293 cells confers gp96 recognition and uptake activity. |
Fucoidan inhibition assay, SR-A knockout macrophages, ectopic SR-A expression in HEK293 cells, gp96 uptake and peptide re-presentation assays |
The EMBO journal |
High |
14609958
|
| 2003 |
Low-endotoxin GRP94/gp96 binds endotoxin in a high-affinity, saturable, and specific manner but does not activate macrophage NF-κB signaling, nitric oxide production, or p38/JNK pathways; low-endotoxin GRP94 does, however, elicit ERK phosphorylation in macrophages at low concentrations. |
Endotoxin depletion/depyrogenation, binding assays, NF-κB luciferase reporter, nitric oxide assay, Western blot for MAP kinase phosphorylation |
The Journal of biological chemistry |
High |
12805368
|
| 2004 |
Apo-GRP94 undergoes a time- and temperature-dependent tertiary conformational change that exposes a site of protein-protein interaction; ATP, ADP, and radicicol suppress this conformational change and GRP94 homo-oligomerization; ATP/ADP do not release GRP94 from immunoglobulin heavy chain folding intermediates, indicating that structural maturation of client protein (rather than nucleotide binding/hydrolysis) drives dissociation of GRP94-client complexes. |
Biochemical conformational change assays, native gel analysis of oligomerization, immunoprecipitation of GRP94-Ig heavy chain complexes with ATP/ADP treatment |
Biochemistry |
High |
15236592
|
| 2000 |
GRP94 undergoes hyperglycosylation in Sf21 insect cells and is phosphorylated on CK2-sensitive serine/threonine sites in intact cells; only the highest-molecular-weight (most extensively glycosylated) form of GRP94 is phosphorylated in vivo, suggesting compartmentalized regulation. |
Metabolic 32P labeling, tunicamycin treatment, phosphopeptide mapping, in vitro CK2 phosphorylation |
Biochimica et biophysica acta |
Medium |
10771098
|
| 2005 |
Listeria monocytogenes virulence factor Vip (an LPXTG surface protein) binds the ER-resident chaperone Gp96 as its cellular receptor; the Vip-Gp96 interaction is critical for bacterial entry into some mammalian cell types. |
Ligand overlay (far-Western) assay, co-immunoprecipitation, infection assays with vip mutant bacteria, mouse infection models |
The EMBO journal |
High |
16015374
|
| 2008 |
OS-9, an ER-resident glycoprotein containing a mannose-6-phosphate receptor homology (MRH) domain, associates with the ER chaperone GRP94; together with Hrd1 and SEL1L, GRP94 is required for ERAD of mutant alpha1-antitrypsin. |
Co-immunoprecipitation, siRNA knockdown of GRP94 with ERAD substrate degradation assay |
Nature cell biology |
High |
18264092
|
| 2008 |
In B cells, HSP90B1 (gp96/GRP94) is required for proper compartmentalization of B cells via selective integrins and for TLR-stimulated antibody production, but is not required for immunoglobulin assembly, class switching, germinal center formation, or memory antibody responses. |
B-cell-specific HSP90B1-null mice (conditional knockout), flow cytometry for integrin expression, in vivo immunization/antibody assays, plasma cell differentiation analysis |
Blood |
High |
18509083
|
| 2009 |
Gp96 (GRP94) is an obligate chaperone for the GPIX subunit of the platelet GPIb-IX-V complex; gp96/grp94 deletion in the murine hematopoietic system leads to thrombocytopenia, prolonged bleeding time, and giant platelets (Bernard-Soulier phenotype); gp96 binds selectively to the GPIX subunit but not to GPIbα or GPIbβ. |
Hematopoietic-specific gp96 conditional KO, flow cytometry for GPIb-IX complex expression, ERAD assay, co-immunoprecipitation of gp96 with GPIX |
Blood |
High |
21576699
|
| 2009 |
Gp96 (GRP94) associates with pro-ADAMTS9 in the ER (identified by cross-linking and mass spectrometry) and is required for cell-surface trafficking and furin-mediated processing of pro-ADAMTS9; gp96 siRNA reduces cell-surface pro-ADAMTS9 levels; geldanamycin treatment impairs furin processing of pro-ADAMTS9. |
Chemical cross-linking, mass spectrometry, co-immunoprecipitation, siRNA knockdown, cell-surface biotinylation assay |
The Journal of biological chemistry |
High |
19875450
|
| 2009 |
Drosophila gp93 is a functional ortholog of mammalian gp96 and can chaperone murine gp96 clients including integrins α4, αL, β2, TLR2, and TLR9; intermolecular disulfide bond formation via Cys138 of gp96 is not required for chaperone function, implicating non-disulfide-bond-mediated N-terminal dimerization as critical for client protein folding. |
Ectopic expression of Drosophila gp93 in gp96-deficient mouse cells, flow cytometry for client protein expression, site-directed mutagenesis (C138A) |
Journal of immunology |
High |
19786753
|
| 2010 |
Complete knockout of GRP94 in embryonic stem cells causes compensatory upregulation of ER chaperones GRP78, calnexin, and calreticulin (but not PDI), and significantly decreases the ER-stress-induced spliced XBP-1 (IRE1 pathway); homozygous GRP94 KO leads to embryonic lethality. |
Conditional knockout mouse model, GRP94-null embryonic stem cells, Western blot for chaperone levels, XBP-1 splicing assay |
PloS one |
Medium |
20520781
|
| 2011 |
Oocyte-specific deletion of Hsp90b1 causes failure of first mitosis in mouse zygotes, with abnormal mitotic spindle formation or G2/M block; this is associated with defective organization of the cytoplasmic region surrounding the zygotic spindle; HSPA5 (BiP), although overexpressed, does not compensate for HSP90B1 deficiency in zygotes. |
ZP3-Cre oocyte-specific conditional KO, time-lapse microscopy, immunofluorescence of mitotic spindle and ER markers |
PloS one |
Medium |
21358806
|
| 2012 |
Pharmacologic inhibition of gp96 (with a selective inhibitor) inhibits TLR9 proteolytic processing and increases TLR9 sensitivity to proteolytic degradation; TLR9 remains associated with gp96 during intracellular trafficking beyond the ER, suggesting gp96 is required both for TLR9 ER egress and for conformational stability in endosomal compartments. |
Pharmacological gp96 inhibition, co-immunoprecipitation of gp96-TLR9 during trafficking, protease-sensitivity assay, TLR9 signaling assay |
Biochemical and biophysical research communications |
Medium |
22554506
|
| 2012 |
A structure-based Grp94-selective inhibitor (compound 2) prevents intracellular trafficking of a TLR (Toll receptor), inhibits secretion of IGF-II, affects the conformation of Grp94, and suppresses Drosophila larval growth (all Grp94-dependent processes), while having no effect on cytosolic Hsp90α/β clients at similar concentrations. |
Structure-based inhibitor design, cell-based trafficking assay, IGF-II secretion ELISA, Drosophila growth assay, cell viability assay for selectivity |
Journal of the American Chemical Society |
High |
22642269
|
| 2014 |
In vitro kinetics studies show that Grp94 recognizes on-pathway aggregates (not unfolded monomers) of myocilin olfactomedin domain (myoc-OLF), co-precipitates with myoc-OLF aggregates, and accelerates their aggregation rate; Grp94 inhibition reduces levels of mutant and forced-misfolded wild-type myocilin and rescues toxicity in primary trabecular meshwork cells. |
In vitro aggregation kinetics, co-precipitation assay, selective Grp94 inhibitor in cell-based rescue assay |
Human molecular genetics |
High |
25027323
|
| 2015 |
GP96 is an essential chaperone for the cell-surface protein GARP (glycoprotein A repetitions predominant), which is a docking receptor for latent membrane-associated TGF-β; loss of GP96 in Tregs eliminates GARP and integrin surface expression, prevents mLTGF-β expression, impairs active TGF-β production, and destabilizes FOXP3 expression resulting in systemic IFN-γ/IL-17 accumulation. |
Murine Treg-specific GP96 conditional KO, flow cytometry for GARP and integrin expression, FOXP3 intracellular staining, TGF-β activation assay, in vivo adoptive transfer |
The Journal of clinical investigation |
High |
25607841
|
| 2015 |
Cell membrane gp96 (mgp96) interacts directly with HER2 at the cell surface via its C-terminal domain, facilitates HER2 dimerization, and promotes cell proliferation; mgp96 levels correlate with HER2 phosphorylation in primary breast tumors; targeting mgp96 with monoclonal antibody decreases cell growth and increases apoptosis. |
Co-immunoprecipitation, domain-mapping, flow cytometry for HER2 dimerization (FRET/proximity), tumor xenograft assay |
International journal of cancer |
Medium |
25546612
|
| 2015 |
Cell membrane gp96 (mgp96) C-terminal domain directly interacts with ER-α36 (estrogen receptor variant) on the cell membrane, stabilizing ER-α36 protein and increasing its downstream signaling to promote tumor cell growth and invasion; siRNA or monoclonal antibody targeting mgp96 blocks this interaction and inhibits breast cancer growth in vitro and in vivo. |
Co-immunoprecipitation with domain mapping, siRNA knockdown, antibody blocking, in vitro/in vivo tumor assays |
Oncotarget |
Medium |
26396174
|
| 2016 |
Gp96 interacts with non-muscle myosin heavy chain IIA (NMHCIIA), controls its activity and remodeling, and is required for appropriate coordination of plasma membrane bleb formation and retraction in response to pore-forming toxins; Gp96 and NMHCIIA are recruited to PM blebs and protect cells against listeriolysin O during L. monocytogenes infection; this association also affects cytoskeletal organization and cell migration. |
Co-immunoprecipitation, live-cell imaging of bleb dynamics, siRNA knockdown, in vivo Zebrafish infection model, proximity ligation assay |
EMBO reports |
High |
28039206
|
| 2019 |
GRP94 interacts with PI3K-interacting protein 1 (Pik3ip1) as determined by co-immunoprecipitation and proximity ligation assay; GRP94 promotes muscle differentiation by inhibiting the PI3K/AKT/mTOR signaling pathway in a Pik3ip1-dependent manner, and regulates Pik3ip1 expression. |
Co-immunoprecipitation, proximity ligation assay, siRNA knockdown of Pik3ip1, in vitro and in vivo muscle differentiation assays |
Journal of cellular physiology |
Medium |
31025379
|
| 2020 |
Cell-surface gp96 interacts with viral glycoprotein Q1 (gQ1) of human herpesviruses HHV-6A and HHV-6B during virus entry; gp96 surface expression levels correlate with HHV-6 entry efficiency; loss-of-function and gain-of-function experiments confirm gp96 is required for HHV-6 infection. |
Co-immunoprecipitation of gp96 with gQ1, gp96 overexpression/knockdown, virus entry assay |
Journal of virology |
Medium |
32295911
|
| 2021 |
FBXL2 targets EGFR for proteasome-mediated degradation; Grp94 protects EGFR from degradation by blocking FBXL2 binding to EGFR, thereby stabilizing EGFR and promoting NSCLC growth; pharmacologic Grp94 inhibition or FBXL2 upregulation destabilizes EGFR including TKI-resistant mutants. |
Co-immunoprecipitation, siRNA knockdown, overexpression, ubiquitination assay, tumor xenograft assay |
Nature communications |
High |
34635651
|
| 2021 |
IAV-infected human epithelial cells display surface GP96 via GP96 chaperone activity; extracellular surface GP96 binds pneumococcal oligopeptide permease components and, together with integrin αV, mediates efficient pneumococcal adherence; GP96 chemical inhibition or genetic knockout reduces pneumococcal adherence and enhances bacterial clearance in infected mice. |
Immunofluorescence for surface GP96 expression, co-immunoprecipitation of GP96 with pneumococcal proteins, GP96 inhibition/KO infection assays, in vivo mouse pneumonia model |
mBio |
High |
34061598
|
| 2022 |
BiP (the ER Hsp70) acts as a cochaperone that accelerates Grp94 closure; the BiP nucleotide-binding domain interacts with the Grp94 middle domain; client binding to BiP causes a conformational change that enables BiP to bind Grp94 and accelerate its ATP-dependent closure; single-molecule FRET shows BiP stabilizes a high-energy conformational intermediate of Grp94; together, BiP and ATP push Grp94 into the active closed conformation; nucleotide binding reduces Grp94's affinity for clients. |
Single-molecule FRET, ATPase activity assay, co-chaperone binding assay, domain mutant analysis, reconstituted in vitro system |
Proceedings of the National Academy of Sciences of the United States of America |
High |
35078937
|
| 2023 |
HSP90B1 interacts with c-Myc as demonstrated by co-immunoprecipitation; reducing HSP90B1 level reverses p21 overexpression caused by c-Myc overexpression, indicating that HSP90B1/c-Myc interaction regulates the p21 signaling pathway and affects cisplatin chemosensitivity by modulating bladder cancer cell senescence. |
Co-immunoprecipitation, Western blot for p21, siRNA knockdown, senescence-associated β-galactosidase staining, cisplatin sensitivity assay |
Aging |
Medium |
37433010
|
| 2024 |
Grp94's pre-N domain suppresses ATP hydrolysis and conformational transitions to the active chaperone conformation; DnaJB11 (BiP co-chaperone) promotes BiP-Grp94 interaction and relieves pre-N domain suppression of Grp94 ATPase activity; ATP binding alters the ATP lid conformation of Grp94; BiP binding stabilizes a partially closed Grp94 intermediate; nucleotide binding reduces Grp94 affinity for clients; folding of some Grp94 clients does not require direct Grp94-BiP interactions in vivo. |
In vitro ATPase assay, structural studies (conformation assays), in vivo client folding assay, domain deletion mutants, protein interaction assays |
Proceedings of the National Academy of Sciences of the United States of America |
High |
38483986
|