Sprangers Joep, Rabouille Catherine
*Hubrecht Institute of the KNAW and UMC Utrecht, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
Biochem Soc Trans. 2015 Feb;43(1):97-103. doi: 10.1042/BST20140283.
Protein export from the endoplasmic reticulum (ER), the first step in protein transport through the secretory pathway, is mediated by coatomer protein II (COPII)-coated vesicles at ER exit sites. COPII coat assembly on the ER is well understood and the conserved large hydrophilic protein Sec16 clearly has a role to play in COPII coat dynamics. Sec16 localizes to ER exit sites, its loss of function impairs their functional organization in all species where it has been studied, and it interacts with COPII coat subunits. However, its exact function in COPII dynamics is debated, as Sec16 is proposed to act as a scaffold to recruit COPII components and as a device to regulate the Sar1 activity in uncoating, in such a way that the coat is released only when the vesicle is fully formed and loaded with cargo. Furthermore, Sec16 has been shown to respond to nutrient signalling, thus coupling environmental stimuli to secretory capacity.
从内质网（ER）输出蛋白质是蛋白质通过分泌途径运输的第一步，由内质网出口位点上被II型被膜小泡蛋白（COPII）包被的小泡介导。内质网上COPII被膜的组装已得到充分了解，保守的大型亲水蛋白Sec16显然在COPII被膜动态变化中发挥作用。Sec16定位于内质网出口位点，在所有已研究的物种中，其功能丧失都会损害这些位点的功能组织，并且它与COPII被膜亚基相互作用。然而，关于其在COPII动态变化中的确切功能存在争议，因为有人提出Sec16作为一种支架来募集COPII组分，并作为一种在脱被膜过程中调节Sar1活性的装置，使得只有当小泡完全形成并装载货物时被膜才会释放。此外，Sec16已被证明对营养信号作出反应，从而将环境刺激与分泌能力联系起来。
