The endoplasmic reticulum-associated protein, OS-9, behaves as a lectin in targeting the immature calcium-sensing receptor
MetadataShow full item record
The mechanisms responsible for the processing and quality control of the calcium-sensing receptor (CaSR) in the endoplasmic reticulum (ER) are largely unknown. In a yeast two-hybrid screen of the CaSR C-terminal tail (residues 865-1078), we identified osteosarcoma-9 (OS-9) protein as a binding partner. OS-9 is an ER-resident lectin that targets misfolded glycoproteins to the ER-associated degradation (ERAD) pathway through recognition of specific N-glycans by its mannose-6-phosphate receptor homology (MRH) domain. We show by confocal microscopy that the CaSR and OS-9 co-localize in the ER in COS-1 cells. In immunoprecipitation studies with co-expressed OS-9 and CaSR, OS-9 specifically bound the immature form of wild-type CaSR in the ER. OS-9 also bound the immature forms of a CaSR C-terminal deletion mutant and a C677A mutant that remains trapped in the ER, although binding to neither mutant was favored over wild-type receptor. OS-9 binding to immature CaSR required the MRH domain of OS-9 indicating that OS-9 acts as a lectin most likely to target misfolded CaSR to ERAD. Our results also identify two distinct binding interactions between OS-9 and the CaSR, one involving both C-terminal domains of the two proteins and the other involving both N-terminal domains. This suggests the possibility of more than one functional interaction between OS-9 and the CaSR. When we investigated the functional consequences of altered OS-9 expression, neither knockdown nor overexpression of OS-9 was found to have a significant effect on CaSR cell surface expression or CaSR-mediated ERK1/2 phosphorylation.
Showing items related by title, author, creator and subject.
Deleo, Domenica (1994)Prior to the commencement of this study in 1990, a number of reports had appeared in the literature describing the importance of insulin action during lactation in mammals (see Chapter 1). These studies investigated the ...
A fluorescent biosensor reveals conformational changes in human immunoglobulin E Fc: Implications for mechanisms of receptor binding, inhibition, and allergen recognitionHunt, J.; Keeble, A.; Dale, R.; Corbett, Melissa; Beavil, R.; Levitt, J.; Swann, M.; Suhling, K.; Ameer-Beg, S.; Sutton, B.; Beavil, A. (2012)IgE binding to its high affinity receptor Fc?RI on mast cells and basophils is a key step in the mechanism of allergic disease and a target for therapeutic intervention. Early indications that IgE adopts a bent structure ...
Gandhi, Neha; Mancera, Ricardo (2012)Heparin is a glycosaminoglycan known to bind bone morphogenetic proteins (BMPs) and the growth and differentiation factors (GDFs) and has strong and variable effects on BMP osteogenic activity. In this paper we report our ...