Palmitoylation and plasma membrane localization of Ras2p by a nonclassical trafficking pathway in Saccharomyces cerevisiae
Palmitoylation and plasma membrane localization of Ras2p by a nonclassical trafficking pathway in Saccharomyces cerevisiae
复制标题
DOI：
10.1128/mcb.23.18.6574-6584.2003
复制
发表时间：
2003-09-01
影响因子：
5.3
通讯作者：
Deschenes, RJ
中科院分区：
文献类型：
--
作者：
Dong, XW;Mitchell, DA;Deschenes, RJ
Ras 蛋白在质膜上的亚细胞定位部分是通过法尼基部分与保守的 CaaX 盒半胱氨酸的共价连接来实现的。法呢基化将 Ras 靶向内质网 (ER)，在此发生额外的处理步骤，导致 Ras 易位至质膜。发生这种情况的机制尚不清楚。在本报告中，我们表明 Ras2p 在酿酒酵母中的质膜定位不需要经典的分泌途径或功能性高尔基体。然而，当经典分泌途径被破坏时，质膜定位需要 Erf2p，这是一种驻留在 ER 膜上的蛋白质，是 Ras2p 有效棕榈酰化所必需的。 ERF2 的缺失会导致 Ras2p 稳态定位缺陷，当与 sec-ts 突变体或布雷菲德菌素 A 治疗结合使用时，这种缺陷会更加严重。 Ras2p 的 Erf2p 依赖性定位与 Cys-318 的棕榈酰化相关。最近已证明 Erf2p-Erf4p 复合物是 ER 相关的棕榈酰转移酶，其可以棕榈酰化 Ras2p 的 Cys-318 (S. Lobo, W. K. Greentree, M. E. Linder, and R. J. Deschenes, J. Biol. Chem. 277:41268-41273, 2002)。 Erf2 依赖性棕榈酰化以及 Ras2p 的定位需要与 CaaX 框相邻的高变域区域。这些结果为 Ras 蛋白质膜定位的棕榈酰化依赖性非经典内膜运输系统的存在提供了证据。
Subcellular localization of Ras proteins to the plasma membrane is accomplished in part by covalent attachment of a farnesyl moiety to the conserved CaaX box cysteine. Farnesylation targets Ras to the endoplasmic reticulum (ER), where additional processing steps occur, resulting in translocation of Ras to the plasma membrane. The mechanism(s) by which this occurs is not well understood. In this report, we show that plasma membrane localization of Ras2p in Saccharomyces cerevisiae does not require the classical secretory pathway or a functional Golgi apparatus. However, when the classical secretory pathway is disrupted, plasma membrane localization requires Erf2p, a protein that resides in the ER membrane and is required for efficient palmitoylation of Ras2p. Deletion of ERF2 results in a Ras2p steady-state localization defect that is more severe when combined with sec-ts mutants or brefeldin A treatment. The Erf2p-dependent localization of Ras2p correlates with the palmitoylation of Cys-318. An Erf2p-Erf4p complex has recently been shown to be an ER-associated palmitoyltransferase that can palmitoylate Cys-318 of Ras2p (S. Lobo, W. K. Greentree, M. E. Linder, and R. J. Deschenes, J. Biol. Chem. 277:41268-41273, 2002). Erf2-dependent palmitoylation as well as localization of Ras2p requires a region of the hypervariable domain adjacent to the CaaX box. These results provide evidence for the existence of a palmitoylation-dependent, nonclassical endomembrane trafficking system for the plasma membrane localization of Ras proteins.