Cai Huaqing, Yu Sidney, Menon Shekar, Cai Yiying, Lazarova Darina, Fu Chunmei, Reinisch Karin, Hay Jesse C, Ferro-Novick Susan
Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06519, USA.
Nature. 2007 Feb 22;445(7130):941-4. doi: 10.1038/nature05527. Epub 2007 Feb 7.
The budding of endoplasmic reticulum (ER)-derived vesicles is dependent on the COPII coat complex. Coat assembly is initiated when Sar1-GTP recruits the cargo adaptor complex, Sec23/Sec24, by binding to its GTPase-activating protein (GAP) Sec23 (ref. 2). This leads to the capture of transmembrane cargo by Sec24 (refs 3, 4) before the coat is polymerized by the Sec13/Sec31 complex. The initial interaction of a vesicle with its target membrane is mediated by tethers. We report here that in yeast and mammalian cells the tethering complex TRAPPI (ref. 7) binds to the coat subunit Sec23. This event requires the Bet3 subunit. In vitro studies demonstrate that the interaction between Sec23 and Bet3 targets TRAPPI to COPII vesicles to mediate vesicle tethering. We propose that the binding of TRAPPI to Sec23 marks a coated vesicle for fusion with another COPII vesicle or the Golgi apparatus. An implication of these findings is that the intracellular destination of a transport vesicle may be determined in part by its coat and its associated cargo.
内质网衍生囊泡的出芽依赖于COPII衣被复合体。当Sar1-GTP通过与其GTP酶激活蛋白（GAP）Sec23结合来招募货物适配体复合体Sec23/Sec24时，衣被组装开始（参考文献2）。这导致Sec24捕获跨膜货物（参考文献3、4），然后Sec13/Sec31复合体使衣被聚合。囊泡与其靶膜的初始相互作用由拴系蛋白介导。我们在此报告，在酵母和哺乳动物细胞中，拴系复合体TRAPPI（参考文献7）与衣被亚基Sec23结合。这一事件需要Bet3亚基。体外研究表明，Sec23与Bet3之间的相互作用将TRAPPI靶向COPII囊泡以介导囊泡拴系。我们提出，TRAPPI与Sec23的结合标志着一个有被囊泡可与另一个COPII囊泡或高尔基体融合。这些发现的一个启示是，运输囊泡的细胞内目的地可能部分由其衣被及其相关货物决定。
