Szathmary Reka, Bielmann Regula, Nita-Lazar Mihai, Burda Patricie, Jakob Claude A
Institute of Microbiology, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
Mol Cell. 2005 Sep 16;19(6):765-75. doi: 10.1016/j.molcel.2005.08.015.
The Htm1/EDEM protein has been proposed to act as a "degradation lectin" for endoplasmic reticulum-associated degradation (ERAD) of misfolded glycoproteins. In this study, we provide genetic and biochemical evidence that Yos9 protein in Saccharomyces cerevisiae is essential for efficient degradation of mutant glycoproteins. Yos9 is a member of the OS-9 protein family, which is conserved among eukaryotes and shows similarities with mannose-6-phosphate receptors (MPRs). We found that amino acids conserved among OS-9 family members and MPRs were essential for Yos9 protein function. Immunoprecipitation showed that Yos9 specifically associated with misfolded carboxypeptidase Y (CPY*), an ERAD substrate, but only when it carried Man8GlcNAc2 or Man5GlcNAc2 N-glycans. Our experiments further suggested that Yos9 acts in the same pathway as Htm1/EDEM. Yos9 protein is important for glycoprotein degradation and may act via its MRH domain as a degradation lectin-like protein in the glycoprotein degradation pathway.
Htm1/EDEM蛋白被认为可作为内质网相关降解（ERAD）途径中错误折叠糖蛋白的“降解凝集素”。在本研究中，我们提供了遗传学和生物化学证据，证明酿酒酵母中的Yos9蛋白对于突变糖蛋白的有效降解至关重要。Yos9是OS-9蛋白家族的成员，该家族在真核生物中保守，并且与甘露糖-6-磷酸受体（MPR）具有相似性。我们发现OS-9家族成员和MPR中保守的氨基酸对于Yos9蛋白功能至关重要。免疫沉淀显示，Yos9特异性地与错误折叠的羧肽酶Y（CPY*）（一种ERAD底物）结合，但仅当其携带Man8GlcNAc2或Man5GlcNAc2 N-聚糖时才会结合。我们的实验进一步表明，Yos9与Htm1/EDEM作用于相同的途径。Yos9蛋白对于糖蛋白降解很重要，并且可能通过其MRH结构域作为糖蛋白降解途径中类似降解凝集素的蛋白发挥作用。
