Importance of carbohydrate positioning in the recognition of mutated CPY for ER-associated degradation
Importance of carbohydrate positioning in the recognition of mutated CPY for ER-associated degradation
复制标题
DOI：
10.1242/jcs.01740
复制
发表时间：
2005-04-01
影响因子：
4
通讯作者：
Wolf, DH
中科院分区：
文献类型：
--
作者：
Kostova, Z;Wolf, DH
在内质网(ER)中，N-连接的多糖(N-Glycan)作为信号征募参与蛋白质折叠、质量控制和内质网相关降解的凝集素伴侣。我们对突变的羧肽酶yscY(cpy*)的四个N-糖链进行了系统的研究，以确定在内质网相关的降解过程中，这些糖链之间是否存在位置差异。我们构建了含有不同组合的一个、两个或三个N-糖聚糖的低糖基化的cpy*变体，并研究了它们的降解动力学。我们发现CPY*上的四条碳水化合物链在信号功能上并不相等：Asn368连接的糖链的存在是CPY*有效降解的必要条件和充分条件。我们还分析了ER凝集素、Htm1p和Cne1p(酵母钙粘连蛋白)在基于糖链的识别过程中关于N-糖链的数量和位置的参与。我们观察到，Htm1p的功能一般依赖于N-糖链的存在，但对特定的糖链没有位置偏好。然而，Cne1p对底物是有选择性的，只参与一些低糖基化变异体的质量控制。在两种凝集素都参与的情况下，Cne1p和Htm1p在靶向底物降解方面扮演着相互竞争的角色：Cne1p的丢失加速了底物的降解，而Htm1p的丢失则稳定了底物。
In the endoplasmic reticulum (ER), N-linked glycans (N-glycans) function as signals to recruit the lectin chaperones involved in protein folding, quality control and ERassociated degradation. We undertook a systematic study of the four N-glycans of mutated carboxypeptidase yscY (CPY*) to determine whether there are positional differences between the glycans in ER-associated degradation. We constructed hypoglycosylated CPY* variants containing one, two or three N-glycans in various combinations and studied their degradation kinetics. We found that the four carbohydrate chains on CPY* are not equal in their signaling function: presence of the Asn368-linked glycan is necessary and sufficient for efficient degradation of CPY*. We also analysed the involvement of the ER lectins; Htm1p and Cne1p (yeast calnexin) in the glycan-based recognition process with respect to number and position of N-glycans. We observed that Htm1p function depends on the presence of N-glycans in general but that there is no positional preference for a particular glycan. Cne1p, however, is selective with respect to substrate, and participates in the quality control only of some underglycosylated variants. For cases in which both lectins are involved, Cne1p and Htm1p play competing roles in targeting the substrate for degradation: loss of Cne1p accelerates degradation, whereas loss of Htm1p stabilizes the substrate.