| 1998 |
p32/gC1qR contains a 33-amino acid N-terminal presequence that functions as a mitochondrial targeting sequence; a fusion protein of this presequence with GFP translocated to mitochondria of transfected COS-7 cells with proteolytic removal of ~6 kDa, and the mature protein resides in the mitochondrial matrix and/or inner membrane. |
Confocal laser-scanning microscopy, GFP fusion protein transfection, mitoplast fractionation, immunocytochemistry |
Journal of immunology |
High |
9531316
|
| 1996 |
Recombinant gC1qR binds the heparin-binding multimeric form of vitronectin (but not the plasma form) with saturable, high-affinity interaction (KD ~20 nM) inhibitable by glycosaminoglycans; this binding site is distinct from the C1q-binding site, as a truncated gC1qR lacking the N-terminal 22 amino acids lost vitronectin binding but retained C1q binding. |
Recombinant protein expression, affinity chromatography with plasma/serum, solid-phase binding assay, inhibition studies with truncation mutants |
The Journal of biological chemistry |
High |
8900153
|
| 1996 |
gC1qR is a zinc-dependent endothelial cell binding protein for high molecular weight kininogen (HK) and factor XII; these proteins bind to a site on gC1qR distinct from the C1q-binding site, as C1q did not inhibit HK binding and anti-C1q-blocking mAbs did not block HK binding. |
HK-affinity chromatography of HUVEC membrane proteins in presence/absence of ZnCl2, SDS-PAGE, Western blot with anti-gC1qR mAbs, ligand blot, 125I-HK binding inhibition assay |
Proceedings of the National Academy of Sciences |
High |
8710908
|
| 2000 |
gC1q-R/p33 is a direct cellular receptor for InlB, the Listeria monocytogenes invasion protein; InlB binds gC1qR directly (shown by affinity chromatography and ELISA), and transfection of non-permissive cells with human gC1qR promotes entry of InlB-coated beads. gC1qR associates with the adaptor Gab1 upon InlB stimulation and mediates InlB-dependent PI3-kinase membrane recruitment and activation. |
Affinity chromatography, ELISA, transfection of non-permissive GPC16 cells, entry assay with InlB-coated beads, co-immunoprecipitation (gC1qR with Gab1), antibody/C1q inhibition of entry |
The EMBO journal |
High |
10747014
|
| 2000 |
HCV core protein binds gC1qR (identified by yeast two-hybrid screen) and inhibits T-cell proliferation via gC1qR; the core binds the region spanning amino acids 188–259 of gC1qR (distinct from C1q-binding site), and anti-gC1qR antibody reverses core-induced T-cell proliferation inhibition. |
Yeast two-hybrid screen of human T-cell library, biochemical binding analysis with deletion mutants, T-cell proliferation assay with antibody reversal |
The Journal of clinical investigation |
High |
11086025
|
| 2000 |
Staphylococcus aureus protein A directly binds platelet gC1qR/p33; the protein A-binding domain on gC1qR lies outside the N-terminal alpha helix (residues 74–95), distinct from the C1q-binding site. gC1qR capture of S. aureus was inhibited by soluble rgC1qR, anti-gC1qR F(ab')2, and rabbit IgG, and tyrosine inactivation of protein A abrogated gC1qR binding. |
Affinity capture with fixed S. aureus/protein A-agarose, solid-phase ELISA with biotinylated gC1qR, inhibition studies, truncated gC1qR mutant lacking residues 74–95 |
Infection and immunity |
Medium |
10722602
|
| 2001 |
Factor XII binds to a multiprotein receptor complex on endothelial cell membranes comprising gC1qR, urokinase plasminogen activator receptor (uPAR), and cytokeratin 1; antibodies to gC1qR, uPAR, and CK1 each block FXII binding. FXII binds via a region in its fibronectin type II domain (peptide YHK9 from residues 39–47). |
Flow cytometry binding assays with FITC/biotin-FXII, confocal and electron microscopy co-localization, antibody blocking assays, recombinant receptor inhibition |
Blood |
High |
11986212
|
| 2001 |
Factor XII, prekallikrein, and HK activation (conversion of prekallikrein to kallikrein) is catalyzed by gC1qR and cytokeratin 1 in a zinc-dependent, Factor XII-dependent manner; normal plasma activation on endothelial cells is inhibited by antibodies to gC1qR and cytokeratin 1. |
Purified protein contact activation assay, plasma activation assay on endothelial cells, antibody inhibition |
Thrombosis and haemostasis |
Medium |
11204562
|
| 1999 |
gC1qR binds the light chain of HK (zinc-dependent) while cytokeratin 1 binds the heavy-chain domain 3 of HK; anti-gC1qR antibody inhibits HK binding to endothelial cells by 72% and combined anti-gC1qR + anti-CK1 inhibits by 86%. |
Affinity chromatography of HUVEC membranes with HK or domain 3 peptide columns, zinc-dependent elution, Western blot, antibody inhibition of 125I-HK binding |
Clinical immunology |
Medium |
10479529
|
| 1997 |
cC1qR (calreticulin) and gC1qR form a complex; biotinylated cC1qR binds recombinant and native gC1qR with binding sites at N-terminal residues 76–93 and 204–218. Anti-gC1qR mAbs 60.11, 46.23, and 74.5.2 inhibit this interaction, and co-immunoprecipitation of Raji cell membranes with anti-gC1qR mAbs co-precipitates cC1qR. |
Solid-phase ELISA with biotinylated cC1qR and recombinant gC1qR, antibody inhibition, co-immunoprecipitation from cell membranes |
Journal of immunology |
Medium |
9233640
|
| 1999 |
gC1qR binds the C-terminal cytoplasmic domain of the alpha1B-adrenergic receptor (residues 344–516, specifically the arginine-rich residues 369–378) as identified by yeast two-hybrid; co-expression of gC1qR with the receptor causes redistribution of the receptor from plasma membrane to intracellular locations and receptor downregulation. |
Yeast two-hybrid screen of rat liver cDNA library, co-immunoprecipitation from COS-7 cells, confocal co-localization, deletion mutant mapping |
The Journal of biological chemistry |
Medium |
10409668
|
| 2002 |
HABP1/C1QBP is an endogenous substrate for MAP kinase (ERK); in vitro kinase assay demonstrates ERK phosphorylates HABP1, and HABP1 co-immunoprecipitates with activated ERK in cells. Upon PMA stimulation, HABP1 translocates from cytoplasm to nucleus in an ERK-dependent manner (blocked by PD98059). |
In vitro kinase assay, co-immunoprecipitation with activated ERK, subcellular fractionation/immunofluorescence after PMA treatment, ERK inhibitor PD98059 |
Biochemical and biophysical research communications |
Medium |
11866440
|
| 2004 |
Direct binding of HCV core protein to gC1qR on T cells impairs Lck and Akt activation; this binding is inhibitable by anti-gC1qR antibody or soluble gC1qR, is reduced by gC1qR siRNA knockdown, and enhanced by gC1qR transfection. BIAcore analysis gives binding affinity constant of 3.8×10−7 M. |
BIAcore surface plasmon resonance, flow cytometry binding, siRNA knockdown of gC1qR, transfection of guinea pig cells with human gC1qR, Western blot for Lck/ZAP-70/Akt phosphorylation |
Journal of virology |
High |
15163734
|
| 2003 |
HCV core binding to gC1qR on T cells induces G0/G1 cell cycle arrest by stabilizing the CDK inhibitor p27Kip1, thereby preventing CDK2/4 and cyclin E/D expression, pRb phosphorylation, and G1→S transition; arrest is reversible by anti-gC1qR antibody. |
T-cell proliferation assay, flow cytometry cell cycle analysis, Western blot for CDK2/4, cyclin E/D, pRb, p27Kip1, antibody rescue experiment |
Virology |
Medium |
14517080
|
| 2005 |
HCV core/gC1qR ligation on T cells induces SOCS1 and SOCS3 expression, which disrupts STAT phosphorylation and inhibits IFN-γ production; siRNA silencing of either SOCS1 or SOCS3 abrogates the inhibitory effect of core on T-cell IFN-γ production. |
T-cell functional assay, Western blot for SOCS1/3 and p-STAT, siRNA knockdown of SOCS1 and SOCS3, IFN-γ ELISA |
Journal of virology |
Medium |
16306613
|
| 2009 |
gC1qR inhibits RIG-I- and MDA5-dependent antiviral signaling by translocating to the mitochondrial outer membrane upon dsRNA/virus stimulation and interacting with the adaptor VISA/MAVS/IPS-1/Cardif, thereby disrupting RIG-I/MDA5 signaling and promoting virus replication. Knockdown of gC1qR enhances RIG-I-dependent antiviral signaling. |
Co-immunoprecipitation (gC1qR with MAVS), siRNA knockdown, subcellular fractionation showing translocation, viral replication assays |
Proceedings of the National Academy of Sciences |
High |
19164550
|
| 2001 |
MT1-MMP cleaves gC1qR proteolytically at Gly79↓Gln80 in vitro and in cell culture; the hemopexin-like domain of MT1-MMP is required for proteolysis. A catalytically inactive MT1-MMP retains gC1qR binding ability and acts as a cell-surface receptor for gC1qR. |
In vitro proteolysis assay with recombinant proteins, cell culture experiments, MT1-MMP domain deletion constructs, hydroxamate inhibitor studies, co-precipitation |
The Journal of biological chemistry |
Medium |
11773076
|
| 2012 |
p32/gC1qR is required for mitochondrial translation; p32-knockout mice show mid-gestation lethality and severe respiratory chain dysfunction. Recombinant p32 binds mitochondrial mRNA (not DNA), endogenous p32 associates with all mitochondrial mRNA species in vivo, and co-immunoprecipitation shows p32 associates with the mitoribosome. |
p32-knockout mouse generation, primary embryonic fibroblast analysis, in vitro RNA-binding assay, co-immunoprecipitation with mitoribosome, mitochondrial respiratory chain assays |
Nucleic acids research |
High |
22904065
|
| 2007 |
Plasmodium falciparum-infected red blood cells use gC1qR/HABP1/p32 as a receptor to bind to human brain microvascular endothelial cells and to platelets for clumping, as demonstrated by in vitro cytoadherence assays. |
In vitro cytoadherence assay on cells expressing gC1qR, blocking with anti-gC1qR antibodies and recombinant gC1qR |
PLoS pathogens |
Medium |
17907801
|
| 2011 |
Cell-surface gC1qR is required for growth factor-induced lamellipodia formation and cell migration; gC1qR is concentrated in lamellipodia with CD44, monosialoganglioside, actin, and phospho-FAK, and gC1qR depletion reduces FAK activation, receptor tyrosine kinase activation, lamellipodia formation, cell migration, and in vivo metastasis. |
siRNA knockdown, immunofluorescence co-localization in lamellipodia, Western blot for FAK/RTK phosphorylation, migration assay, xenograft mouse model |
The Journal of biological chemistry |
Medium |
21536672
|
| 2013 |
Soluble gC1qR binds to endothelial cells via residues 174–180, with binding mediated through surface-bound fibrinogen; this binding induces upregulation of bradykinin receptor B1R expression, an effect diminished by gC1qR lacking residues 174–180 and 154–162 and inhibited by anti-fibrinogen antibody. |
Solid-phase binding assay, deconvolution fluorescence microscopy, flow cytometry for B1R expression, deletion mutant analysis, antibody inhibition |
Journal of immunology |
Medium |
24319267
|
| 2001 |
gC1q-R/GABA(A) receptor beta subunit interaction: gC1qR co-purifies with immunopurified GABA(A) receptors and exhibits reciprocal co-immunoprecipitation from rat brain membranes. Yeast two-hybrid showed all beta subunits (but not alpha1 or gamma2) interact with gC1qR via a 15-amino-acid stretch (residues 399–413) containing 7 positively charged residues. |
Immunopurification from bovine brain, mass spectrometric identification, reciprocal Co-IP from rat brain membranes, yeast two-hybrid with deletion mutants |
The Journal of biological chemistry |
Medium |
11350968
|
| 2017 |
Biallelic loss-of-function mutations in C1QBP cause combined respiratory-chain enzyme deficiency of complexes I, III, and IV; complementation of C1qbp−/− MEFs with wild-type but not mutagenized C1qbp restores OXPHOS protein levels and mitochondrial enzyme activities, establishing C1QBP as essential for mitochondrial energy metabolism. |
Patient genetics, C1qbp−/− MEF complementation assay (wild-type vs. mutant), respiratory chain enzyme activity assays, OXPHOS complex protein levels |
American journal of human genetics |
High |
28942965
|
| 2017 |
Cardiomyocyte-specific deletion of p32/C1qbp causes contractile dysfunction, cardiac dilatation, fibrosis, decreased COX1 expression, reduced oxygen consumption, and increased oxidative stress. p32-deficient hearts show constitutive AMPK phosphorylation, reduced mTOR signaling, increased FGF21/integrated stress response, and impaired urea cycle, with median lifespan ~14 months. |
Cre-loxP cardiac-specific knockout, echocardiography, electron microscopy of mitochondria, Western blot for AMPK/mTOR/signaling proteins, metabolic analysis, Seahorse respirometry |
Cardiovascular research |
High |
28498888
|
| 2018 |
p32/C1qbp interacts with the E2 component of the pyruvate dehydrogenase (PDH) complex (dihydrolipoamide S-acetyltransferase, DLAT) and positively regulates PDH activity; p32-deficient DCs show impaired LPS-induced citrate increase, and PDH inhibitor reproduces the p32-null phenotype of decreased DC maturation in vivo. |
Co-immunoprecipitation of p32 with DLAT, PDH activity assay in p32-deficient DCs, metabolic analysis, PDH inhibitor in vivo study in p32-null mice |
Cell reports |
High |
30428349
|
| 2016 |
Subcellular fractionation combined with Co-IP-MS identified DLAT (dihydrolipoyllysine-residue acetyltransferase, E2 subunit of PDH complex) as a novel mitochondrial interacting partner of C1QBP; PDH activity is affected by C1QBP expression level. |
Subcellular fractionation coupled with Co-IP and mass spectrometry, validation by Co-IP/Western blot, PDH activity assay |
Analytical and bioanalytical chemistry |
Medium |
26753982
|
| 2019 |
C1QBP forms a complex (MRC) with MRE11 and RAD50 that stabilizes MRE11/RAD50 but inhibits MRE11 nuclease activity by preventing DNA/chromatin binding. Upon DNA double-strand breaks, ATM phosphorylates MRE11 at S676/S678, dissociating the MRC and allowing MRN complex assembly and recruitment to DSBs; either excess or insufficient C1QBP impairs DSB repair. |
Co-immunoprecipitation, MRE11 nuclease activity assay, chromatin fractionation, ATM kinase assay, phosphorylation site mutagenesis, C1QBP knockdown/overexpression with DSB response readouts |
Molecular cell |
High |
31353207
|
| 2014 |
C1QBP interacts with YBX1 and negatively regulates YBX1 activation; C1QBP knockdown enhances YBX1 phosphorylation and nuclear translocation in renal cell carcinoma. |
Co-immunoprecipitation followed by mass spectrometry, validation by IP/Western blot, siRNA knockdown of C1QBP, nuclear fractionation |
Journal of proteome research |
Medium |
25497084
|
| 2017 |
C1QBP interacts with YBX1 and suppresses YBX1 activation by altering YBX1 phosphorylation and nuclear translocation in RCC cells; this suppresses AR-modulated MMP9 signaling to inhibit cell invasion, confirmed in orthotopic in vivo mouse model. |
Co-immunoprecipitation, Western blot for YBX1 phosphorylation and nuclear translocation, siRNA/overexpression functional assays, orthotopic mouse model |
Neoplasia |
Medium |
28107702
|
| 2015 |
ZNF32 transcriptionally activates C1QBP expression; C1QBP is a direct target gene of ZNF32 that inactivates the p38 MAPK pathway to protect against oxidative stress-induced apoptosis. ZNF32-deficient cells show reduced C1QBP and increased p38 MAPK activation. |
Chromatin immunoprecipitation (ZNF32 binding to C1QBP promoter), ZNF32 knockdown/overexpression with C1QBP and p38 MAPK readouts, luciferase promoter assay |
Oncotarget |
Medium |
26497555
|
| 2020 |
The FXII fibronectin type II (FnII) domain binds gC1qR in a Zn2+-dependent, asymmetric fashion on the gC1qR trimer; crystal structure of the FXIIFnII–gC1qR complex reveals Arg36 and Arg65 of FXII contact two distinct negatively charged pockets of gC1qR. gC1qR residues Asp185 and His187 coordinate Zn2+ adjacent to the FXII-binding site; binding induces allosteric ordering of the anionic G1-loop. HK domain 5 (HKD5) binds only one high-affinity site per gC1qR trimer via a central G3-loop (steric occlusion mechanism). gC1qR clusters FXII and HK into a ~500 kDa ternary complex and stimulates coagulation in a FXII-dependent manner. |
Crystal structure determination, SPR with mutagenesis, gel filtration for ternary complex, plasma-based FXII-dependent coagulation assay |
Blood |
High |
32559765
|
| 2021 |
C1qbp is intrinsically required for effector CD8+ T cell differentiation; C1qbp-deficient CD8+ T cells fail to increase mitochondrial respiratory capacity upon activation, resulting in diminished acetyl-CoA and elevated fumarate and 2-hydroxyglutarate, leading to H3K27 hypoacetylation and hypermethylation and transcriptional silencing of effector genes. Fumarate supplementation or HDAC inhibitor + acetate reversed the differentiation defect. |
Conditional C1qbp knockout in CD8+ T cells, metabolomics, histone modification analysis (ChIP), Seahorse respirometry, viral infection models, pharmacological rescue |
Science advances |
High |
34860557
|
| 2020 |
Active caspase-1 cleaves gC1qR at two caspase-1 cleavage sites, preventing mitochondrial import of gC1qR; this results in aerobic glycolysis (Warburg effect) and enhanced cell proliferation. Non-mitochondrial gC1qR localization correlated with caspase-1 activation and tumor grade in colorectal carcinoma patients. |
Caspase-1 cleavage assay in vitro, mitochondrial import assay, metabolic profiling of glycolysis/OXPHOS, cell proliferation assay, immunohistochemistry correlation in patient tumors |
Frontiers in oncology |
Medium |
33102234
|
| 1999 |
gC1qR binds directly to the D domain of fibrinogen/fibrin (specifically the C-terminal segment of the fibrinogen gamma chain in fragment D-100, lost upon further plasmin digestion to D-60) and inhibits fibrin polymerization in a dose-dependent manner; at 2:1 molar ratio (gC1qR:fibrinogen), fibrin clot formation is completely inhibited. |
Solid-phase ELISA with biotinylated gC1qR, fibrin polymerization turbidity assay, binding to fibrinogen degradation fragments |
Clinical immunology |
Medium |
10075865
|
| 1998 |
Soluble recombinant gC1qR (rgC1qR) enhances blood coagulation: it dose-dependently shortens prothrombin time and plasma recalcification time, with procoagulant activity measurable in factor XII- or factor XI-deficient plasma, suggesting activity not exclusively through the contact system. |
Prothrombin time assay in human plasma, plasma recalcification time assay, factor-deficient plasma studies, chromogenic substrate assays for thrombin and factor Xa |
Blood coagulation & fibrinolysis |
Medium |
9607116
|
| 2021 |
Exosomal CD44v6/C1QBP complex from pancreatic cancer cells is delivered to the plasma membrane of hepatic stellate cells (HSCs), leading to phosphorylation of IGF-1 signaling molecules, HSC activation, and liver fibrosis promoting metastasis. C1QBP knockdown suppresses this effect in vitro and in vivo. |
Exosome isolation, stable lentiviral knockdown/overexpression, mouse liver metastasis models, Western blot for IGF-1R phosphorylation, HSC activation markers |
Gut |
Medium |
33827783
|
| 2017 |
C1QBP in lipid rafts is required for IGF-1-induced hepatic metastasis of pancreatic cancer; IGF-1 triggers translocation of C1QBP from cytoplasm to lipid rafts and formation of a CD44v6/C1QBP complex, which promotes IGF-1R phosphorylation and downstream PI3K/MAPK signaling. C1QBP knockdown suppresses hepatic metastasis in nude mice. |
Lipid raft fractionation, Co-IP of CD44v6 and C1QBP, Western blot for IGF-1R/PI3K/MAPK phosphorylation, siRNA knockdown, hepatic metastasis mouse model |
International journal of cancer |
Medium |
28608366
|
| 2002 |
HABP1/gC1qR forms a noncovalently associated homotrimer in equilibrium with a covalently linked hexamer (dimer of trimers) through disulfide bonds at Cys186; the hexameric form shows enhanced affinity for hyaluronan, gC1q, and mannosylated BSA compared with the trimer. |
Size-exclusion chromatography, glutaraldehyde cross-linking, fluorescence spectroscopy with Hg2+, Cys186 chemical modification, ligand-binding assays comparing trimer vs. hexamer |
European journal of biochemistry |
Medium |
11784324
|
| 2012 |
DC-SIGN, C1q, and gC1qR form a trimolecular receptor complex on immature dendritic cells; DC-SIGN binds directly to C1q (and its globular domain) in a Ca2+-dependent manner at its mannose-binding pocket, and C1q/gC1qR associate with DC-SIGN on blood DC precursors and immature DCs by immunofluorescence and antigen-capture ELISA. |
ELISA, flow cytometry, immunoprecipitation, surface plasmon resonance, immunofluorescence microscopy, mannan competition, calcium chelation |
Blood |
Medium |
22700724
|
| 2022 |
C1QBP directly interacts with the C9-ALS-associated proline-arginine dipeptide repeat protein (PR50); C1QBP knockdown in HMC3 microglial cells induces NLRP3 inflammasome activation similar to PR50 expression. The compound syringin blocks the PR50-C1QBP interaction and reduces PR50-induced NLRP3 inflammasome activation. |
Co-immunoprecipitation, siRNA knockdown of C1QBP, NLRP3 inflammasome activity assay, syringin treatment/competitive inhibition |
Cells |
Low |
36231090
|
| 2005 |
HABP1/gC1qR localizes to the Golgi apparatus and disperses throughout the cell during mitosis, resembling the distribution dynamics of its ligand hyaluronan. |
Indirect immunofluorescence with Golgi and mitochondrial markers across cell cycle stages |
Cell research |
Low |
15780180
|
| 2016 |
Mutational analysis of C1q globular head modules revealed that Arg162 of the ghA module is central to C1q-gC1qR interaction, while an Arg114Glu substitution in ghB enhanced binding; ghA, ghB, and ghC each independently bind gC1qR and attenuate PHA-stimulated PBMC proliferation. |
Recombinant globular head module expression, substitution mutagenesis, ELISA binding assays, cell proliferation assay |
Frontiers in immunology |
Medium |
28018340
|