Exploration of the topological requirements of ERAD identifies Yos9p as a lectin sensor of misfolded glycoproteins in the ER lumen
Exploration of the topological requirements of ERAD identifies Yos9p as a lectin sensor of misfolded glycoproteins in the ER lumen
复制标题
DOI：
10.1016/j.molcel.2005.07.027
复制
发表时间：
2005-09-16
期刊：
影响因子：
16
通讯作者：
Weissman, JS
中科院分区：
文献类型：
--
作者：
Bhamidipati, A;Denic, V;Weissman, JS
糖蛋白的内质网相关降解（ERAD）依赖于对蛋白质错误折叠的双重识别以及底物N -连接聚糖的重塑。识别之后，底物被逆向转运到细胞质中进行蛋白酶体降解。为了探究这一过程的方向性，我们在酵母中将一种高度稳定的蛋白质二氢叶酸还原酶（DHFR）融合到可溶性内质网相关降解底物羧肽酶Y*（CPY*）的N端或C端。C端CPY* - DHFR融合蛋白的降解明显减慢，并且伴随着二氢叶酸还原酶（DHFR）在内质网腔中的释放。因此，折叠的内质网腔结构域能够阻碍蛋白质的逆向转运。内质网腔蛋白Yos9p对于二氢叶酸还原酶（DHFR）的释放以及多种内质网相关降解底物的降解都是必需的。Yos9p与底物形成复合物，并且具有一个对其内质网相关降解功能至关重要的糖结合口袋。尽管如此，即使糖结合位点发生突变或者CPY*未糖基化，底物识别仍然存在。这些以及其他方面的考虑表明，Yos9p在对末端错误折叠的糖蛋白的双重识别中起着关键作用。
ER-associated degradation (ERAD) of glycoproteins depends on dual recognition of protein misfolding and remodeling of the substrate's N-linked glycans. After recognition, substrates are retrotranslocated to the cytosol for proteasomal degradation. To explore the directionality of this process, we fused a highly stable protein, DHFR, to the N or C terminus of the soluble ERAD substrate CPY* in yeast. Degradation of the C-terminal CPY*-DHFR fusion is markedly slowed and is accompanied by DHFR release in the ER lumen. Thus, folded lumenal domains can impede protein retrotranslocation. The ER lumenal protein Yos9p is required for both release of DHFR and degradation of multiple ERAD substrates. Yos9p forms a complex with substrates and has a sugar binding pocket that is essential for its ERAD function. Nonetheless, substrate recognition persists even when the sugar binding site is mutated or CPY* is unglycosylated. These and other considerations suggest that Yos9p plays a critical role in the bipartite recognition of terminally misfolded glycoproteins.