Knop M, Hauser N, Wolf D H
Institut fuer Biochemie, Universitaet Stuttgart, Germany.
Yeast. 1996 Sep 30;12(12):1229-38. doi: 10.1002/(sici)1097-0061(19960930)12:12<1229::aid-yea15>3.0.co;2-h.
The endoplasmic reticulum (ER) of eukaryotic cells contains a quality control system, that is required for the proteolytic removal of aberrantly folded proteins that accumulate in this organelle. We used genetic and biochemical methods to analyse the involvement of N-glycosylation in the degradation of a mutant derivative of carboxypeptidase yscY in the ER of the yeast Saccharomyces cerevisiae. Our results demonstrate that N-glycosylation of this protein is required for its degradation since an unglycosylated species is retained stably in the ER. Cells that were devoid of the ER-processing alpha 1,2-mannosidase showed reduced degradation of the glycosylated substrate protein. Disruption of CNE1, a gene encoding a putative yeast homologue for calnexin, did not exhibit any effects on the degradation of this substrate protein in vivo. Also, the alpha 1,2-mannosidase-dependent reduction in the degradation rate did not show any correlation with the function of the CNE1 gene product. Our results suggest that the ER of yeast contains a glycosylation-dependent quality control system, as has been shown for higher eukaryotic cells.
真核细胞的内质网（ER）含有一个质量控制系统，该系统对于蛋白水解去除在这个细胞器中积累的异常折叠蛋白是必需的。我们使用遗传学和生物化学方法来分析N-糖基化在酿酒酵母内质网中羧肽酶yscY突变衍生物降解过程中的作用。我们的结果表明，该蛋白的N-糖基化对于其降解是必需的，因为未糖基化的物种稳定地保留在内质网中。缺乏内质网加工α1,2-甘露糖苷酶的细胞显示糖基化底物蛋白的降解减少。编码假定的酵母钙连蛋白同源物的基因CNE1的破坏在体内对该底物蛋白的降解没有表现出任何影响。此外，α1,2-甘露糖苷酶依赖性的降解速率降低与CNE1基因产物的功能没有任何相关性。我们的结果表明，酵母的内质网含有一个糖基化依赖性质量控制系统，这已在高等真核细胞中得到证实。
