| 2008 |
OS-9 is an ER-resident glycoprotein that binds to ERAD substrates (including mutant alpha1-antitrypsin) and, through the SEL1L adaptor, to the ER-membrane-embedded E3 ubiquitin ligase HRD1. The MRH domain of OS-9 is required for interaction with SEL1L but not with substrate. OS-9 also associates with the ER chaperone GRP94, and both HRD1 and SEL1L are required for degradation of mutant alpha1-antitrypsin. |
Co-immunoprecipitation, RNAi knockdown, functional ERAD degradation assays, domain mutagenesis (MRH domain) |
Nature cell biology |
High |
18264092
|
| 2005 |
OS-9 interacts with both HIF-1alpha and HIF-1alpha prolyl hydroxylases (PHDs). OS-9 gain-of-function promotes HIF-1alpha hydroxylation, VHL binding, proteasomal degradation of HIF-1alpha, and inhibition of HIF-1-mediated transcription. OS-9 loss-of-function via RNAi increases HIF-1alpha protein levels and HIF-1-mediated transcription under non-hypoxic conditions. |
Co-immunoprecipitation, RNAi knockdown, reporter assays, HIF-1alpha stability assays |
Molecular cell |
Medium |
15721254
|
| 2011 |
A subsequent study contradicting OS-9/PHD interaction: OS-9 is a luminal ER protein (confirmed by subcellular fractionation and glycosylation tests) while PHD2 is cytoplasmic; FRET analysis showed no significant in vivo physical interaction between PHD2 and OS-9. Neither overexpression nor lentiviral knockdown of OS-9 affected HIF regulation. |
Subcellular fractionation, glycosylation assay, co-immunoprecipitation, FRET, lentiviral knockdown |
PloS one |
Medium |
21559462
|
| 2009 |
The MRH domain of human OS-9 specifically binds N-glycans lacking the terminal mannose from the C branch (i.e., Man7 isomers with trimmed C-arm alpha1,2-mannose) as demonstrated by frontal affinity chromatography. This lectin activity is required for OS-9 to promote ERAD of the glycosylated substrate NHK in vivo. |
Frontal affinity chromatography with recombinant MRH domain, siRNA knockdown, overexpression of mannosidases, in vivo ERAD assays |
The Journal of biological chemistry |
High |
19346256
|
| 2010 |
Crystal structure of the human OS-9 MRH domain complexed with alpha3,alpha6-mannopentaose reveals a flattened beta-barrel structure with P-type lectin fold and distinctive double tryptophan (WW) residues in the oligosaccharide-binding site that recognize Manalpha1,6Manalpha1,6Man residues on the processed C-arm of high-mannose glycans. |
X-ray crystallography, NMR spectroscopy, biochemical binding assays |
Molecular cell |
High |
21172656
|
| 2010 |
Disposal of soluble ERAD-L substrates (ERAD-LS) is strictly dependent on HRD1, SEL1L, and the two interchangeable lectins OS-9 and XTP3-B. Tethering the same substrates to the membrane (ERAD-LM) renders these ERAD factors dispensable, demonstrating that OS-9/XTP3-B function is pathway-selective. |
RNAi knockdown, pulse-chase degradation assays, genetic epistasis using membrane-tethered vs. soluble substrates |
The Journal of cell biology |
High |
20100910
|
| 2008 |
OS-9.1 and OS-9.2 (alternative splice variants) are transcriptionally induced by the IRE1/XBP1 ER-stress pathway. OS-9 variants selectively bind folding-defective proteins but not folding-competent ones, thereby inhibiting secretion of misfolded conformers (retention function) and promoting their ERAD (disposal function). OS-9 also transiently associates with non-glycosylated misfolded proteins but this association is unproductive for ERAD. |
Co-immunoprecipitation, RNAi knockdown, pulse-chase assays, secretion assays, XBP1 reporter/induction |
The Journal of biological chemistry |
Medium |
18417469
|
| 2008 |
OS-9 is upregulated by ER stress and is required for efficient ubiquitination of glycosylated ERAD substrates (demonstrated by RNAi). OS-9 also binds a misfolded non-glycosylated ERAD substrate but is not required for its ubiquitination or degradation, indicating that OS-9's functional requirement is N-glycan-dependent. |
RNAi knockdown, ubiquitination assays, co-immunoprecipitation, Western blot |
Journal of molecular biology |
Medium |
19084021
|
| 2007 |
OS-9 interacts with the cytosolic N-terminal tail of TRPV4 via co-immunoprecipitation. OS-9 preferentially binds TRPV4 monomers and immature ER-localized forms, impedes TRPV4 release from the ER, reduces TRPV4 at the plasma membrane, and attenuates polyubiquitination of TRPV4 subunits, suggesting a role as an auxiliary maturation factor protecting against premature ERAD. |
Co-immunoprecipitation, knockdown, cell-surface biotinylation, in vivo zebrafish expression, polyubiquitination assays |
The Journal of biological chemistry |
Medium |
17932042
|
| 2018 |
Using homozygous deletion cell lines, OS9 and XTP3B were found to redundantly promote glycoprotein degradation and stabilize the SEL1L/HRD1 dislocon complex. OS9 antagonizes XTP3B-mediated inhibition of non-glycosylated protein degradation. The relative expression ratio of OS9 and XTP3B determines the fidelity of glycoprotein triage in the ER. |
CRISPR/Cas9 homozygous deletions, quantitative ERAD assays, co-immunoprecipitation of SEL1L/HRD1 complex, genetic epistasis |
Molecular cell |
High |
29706535
|
| 2015 |
OS9 interacts specifically with the immature form of the renal Na-K-2Cl co-transporter NKCC2 (identified by yeast two-hybrid and confirmed by co-IP), co-localizes with NKCC2 in the ER, and promotes proteasomal degradation of immature NKCC2. Inactivation of the OS9 MRH domain does not affect this activity, but mutation of NKCC2 N-glycosylation sites abolishes OS9-induced degradation, indicating N-glycan-dependent but MRH-independent recognition. |
Yeast two-hybrid, co-immunoprecipitation, immunocytochemistry, pulse-chase and cycloheximide-chase assays, siRNA knockdown, MRH domain mutagenesis, glycosylation site mutagenesis |
The Journal of biological chemistry |
Medium |
26721884
|
| 2014 |
OS-9 facilitates turnover of hyperglycosylated (nonnative) GRP94 via a lysosomal-like, ERAD-independent mechanism. OS-9 binds preferentially to a subpopulation of GRP94 that is hyperglycosylated on cryptic N-linked acceptor sites, and these GRP94 forms have nonnative conformations and are less active. GRP94 is not required for OS-9 folding and does not collaborate with OS-9 in ERAD of misfolded substrates. |
Co-immunoprecipitation, pulse-chase assays, glycosylation analysis, lysosome inhibitor experiments, RNAi |
Molecular biology of the cell |
Medium |
24899641
|
| 2014 |
The C-terminal domain of mammalian OS-9 contains mammalian-specific inserts that are intrinsically disordered and specifically recognized by the middle and C-terminal domains of GRP94. Glycosylation of full-length GRP94 is essential for OS-9 binding, but this requirement is relieved by deletion of the GRP94 N-terminal domain, indicating an allosteric rather than direct glycan-mediated interaction. |
Domain mapping by co-immunoprecipitation, deletion mutagenesis, biochemical binding assays |
Journal of molecular biology |
Medium |
25193139
|
| 2014 |
OS-9 (but not XTP3-B) is required for ERAD of mutant neuroserpin in familial encephalopathy with neuroserpin inclusion bodies. OS-9 binds mutant neuroserpin via glycan recognition; removal of glycosylation sites increases neuroserpin protein load, while OS-9 overexpression decreases it. This was validated in both cell culture and a murine FENIB model. |
Co-immunoprecipitation, RNAi, overexpression, glycosylation site mutagenesis, mouse model analysis |
Neurobiology of aging |
Medium |
24795221
|
| 2014 |
OS-9 is required for ERAD of both glycosylated and non-glycosylated sonic hedgehog (SHH). OS-9 robustly interacts with a non-glycosylated SHH variant (N278A), indicating that the misfolded polypeptide backbone rather than a glycan signature can serve as the predominant recognition signal for OS-9 in certain substrates. |
RNAi knockdown, co-immunoprecipitation, pulse-chase ERAD assays, glycosylation mutant analysis |
PloS one |
Medium |
24910992
|
| 2002 |
OS-9 interacts specifically with the cytoplasmic intracellular region of the membrane proteinase meprin beta. OS-9 is associated with ER membranes and exposed to the cytoplasm. OS-9 associates transiently with meprin beta coinciding with ER-to-Golgi transport of meprin beta. Only the non-spliced form of OS-9 binds meprin beta, implicating the alternatively spliced segment in binding specificity. |
Yeast two-hybrid, co-immunoprecipitation, subcellular fractionation, deletion mutagenesis, pulse-chase assays |
The Journal of biological chemistry |
Medium |
12093806
|
| 2009 |
The OS-9 MRH domain binds N-glycans containing terminal alpha1,6-linked mannose in the Manalpha1,6(Manalpha1,3)Manalpha1,6(Manalpha1,3)Man structure (Ka ~10^4 M^-1), as determined by frontal affinity chromatography with 92 oligosaccharides. Trimming of either an alpha1,6-linked mannose from the C-arm or an alpha1,3-linked mannose from the B-arm abolishes OS-9 MRH binding. The alpha1-antitrypsin NHK variant (but not wild-type) interacts with OS-9 in cells in a sugar-dependent manner. |
Frontal affinity chromatography (92 glycan panel), tetramer binding assay, site-directed mutagenesis of MRH residues, co-immunoprecipitation |
Glycobiology |
High |
19914915
|
| 2008 |
OS9 physically interacts with DC-STAMP and both proteins co-localize in the ER. Upon TLR-induced DC maturation, DC-STAMP translocates from the ER to the Golgi while OS9 localization is unchanged. The DC-STAMP/OS9 interaction is involved in this ER-to-Golgi translocation process. |
Yeast two-hybrid, co-immunoprecipitation, confocal co-localization, TLR stimulation experiments in CHO cells and dendritic cells |
Molecular immunology |
Low |
18952287
|
| 1999 |
OS-9 interacts with N-copine (a two-C2-domain protein) via the second C2 domain of N-copine and the carboxy-terminal region of OS-9. This interaction is Ca2+-dependent as shown by in vitro binding assays and co-immunoprecipitation. |
Yeast two-hybrid, co-immunoprecipitation, in vitro Ca2+-dependent binding assay |
FEBS letters |
Low |
10403379
|
| 2016 |
Meprin beta (but not meprin A) cleaves OS-9 in vitro and in vivo during ischemia/reperfusion-induced renal injury. Fragmentation of OS-9 by meprin beta was observed in WT mice subjected to IR but not in meprin αβKO mice. Transfection with meprin beta cDNA prevented accumulation of OS-9 under hypoxia mimic conditions. |
In vitro protease assay with purified proteins, meprin knockout mouse model, IR injury model, Western blot, cell transfection |
International journal of nephrology |
Medium |
27478637
|
| 2017 |
OS-9 interacts with the immature form of the calcium-sensing receptor (CaSR) in the ER (identified by yeast two-hybrid and co-IP). OS-9 binding to CaSR requires the MRH domain. Two distinct binding interactions were identified: one involving both C-terminal domains and another involving both N-terminal domains of OS-9 and CaSR. However, OS-9 knockdown or overexpression did not significantly affect CaSR cell surface expression or CaSR-mediated ERK1/2 phosphorylation (negative functional result). |
Yeast two-hybrid, co-immunoprecipitation, confocal co-localization, MRH domain mutagenesis, siRNA knockdown, ERK phosphorylation assay |
Journal of cellular physiology |
Low |
28419469
|
| 2025 |
Cryo-EM structure of the core mammalian ERAD complex comprising OS9, SEL1L, and HRD1 reveals a dimeric assembly where SEL1L and OS9 form a claw-like configuration in the ER lumen for substrate engagement while HRD1 dimerizes in the membrane for substrate translocation. Pathogenic SEL1L mutations at the SEL1L-OS9 interface (Gly585Asp) disrupt complex formation and impair ERAD activity, validated by mutagenesis and crosslinking assays. |
Cryo-EM structure determination, site-directed mutagenesis, crosslinking assays, ERAD functional assays |
Nature communications |
High |
40661598 41593065
|