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8.A.67 The Os-9 Quality Control (ERAD) Protein (Os-9) Family

Os9 is a lectin which functions in endoplasmic reticulum (ER) quality control and ER-associated degradation (ERAD). May bind terminally misfolded non-glycosylated proteins as well as improperly folded glycoproteins, retain them in the ER, and transfer them to the ubiquitination machinery to promote their degradation. Probable transport protein targets include TRPV4.6 (TC# 1.A.4.2.5) (Wang et al. 2007) and KNCC2 (2.A.30.1.1) (Seaayfan et al. 2015).  The Os-9 protein of humans contains a PRKCSH domain which is similar to a region found in the beta-subunit of glucosidase II, which is also known as protein kinase C substrate 80K-H (PRKCSH). The beta subunit is required for the solubility and stability of the heterodimeric enzyme, and is involved in retaining the enzyme within the endoplasmic reticulum. Mutations in the gene coding for PRKCSH have been found to be involved in the development of autosomal dominant polycystic liver disease (ADPLD). This family also includes an ER sensor for misfolded glycoproteins and is therefore likely to be a generic sugar binding domain (25692846).

References associated with 8.A.67 family:

D'Alessio, C. and N.M. Dahms. (2015). Glucosidase II and MRH-domain containing proteins in the secretory pathway. Curr. Protein. Pept. Sci. 16: 31-48. 25692846
Seaayfan, E., N. Defontaine, S. Demaretz, N. Zaarour, and K. Laghmani. (2015). OS9 interacts with NKCC2 and targets its immature form for the endoplasmic-reticulum-associated degradation pathway. J. Biol. Chem. [Epub: Ahead of Print] 26721884
Wang, Y., X. Fu, S. Gaiser, M. Köttgen, A. Kramer-Zucker, G. Walz, and T. Wegierski. (2007). OS-9 regulates the transit and polyubiquitination of TRPV4 in the endoplasmic reticulum. J. Biol. Chem. 282: 36561-36570. 17932042
Wu, X. and T.A. Rapoport. (2018). Mechanistic insights into ER-associated protein degradation. Curr. Opin. Cell Biol. 53: 22-28. [Epub: Ahead of Print] 29719269