GBF1 recruits ARF:GDP to the ERGIC

GBF1 recruits inactive ARF:GDP complexes to the ERGIC (Monetta et al, 2007). There are 5 known ADP-ribosylation factor proteins (ARFs) in the human cell. Class I members ARF1 and ARF 3 are expressed at high levels and broadly distributed through the secretory system, while Class II members ARF4 and ARF5 are expressed at lower levels, with ARF4 showing the most specific localization to the ERGIC compartment. ARF6, the single Class III ARF, appears to function more specifically in endocytosis and actin dynamics (Chun et al, 2008; reviewed in D'Souza-Schorey and Chavrier, 2006; Szul and Sztul, 2011). There is conflicting evidence regarding what ARF(s) is required at the ERGIC membrane. GBF1 has been shown to activate ARF1, 4, and 5, but not ARF3, while single and pairwise knockdown of ARF1, 3, 4 and 5 suggests that although no single ARF is responsible for any given step in the secretory pathway, ARF1 and ARF3 contribute most specifically to the ERGIC-Golgi step (Manolea et al, 2010; Volpicelli-Daley et al, 2005). Recruitment of ARF at may also be facilitated by interaction with p24 family members (Gommel et al, 2001; reviewed in Schuiki and Volchuk, 2012).

GBF1招募非活性ARF:GDP复合物至ERGIC（Monetta等，2007年）。人类细胞中共有五种已知的ADP核糖基化因子蛋白（ARFs）。I类成员ARF1和ARF3表达水平较高，广泛分布于分泌系统中，而II类成员ARF4和ARF5表达水平较低，其中ARF4在ERGIC区室的定位最为特异。ARF6，作为唯一的III类ARF，似乎在胞吞作用和细胞骨架动态中发挥更为特异的作用（Chun等，2008年；参见D'Souza-Schorey和Chavrier，2006年综述；Szul和Sztul，2011年）。关于在ERGIC膜上需要哪些ARF存在争议。研究表明，GBF1可激活ARF1、4和5，但非ARF3，而ARF1、3、4和5的单个和成对敲低实验表明，尽管没有单个ARF对分泌途径的每一步负责，ARF1和ARF3对ERGIC-高尔基复合物的步骤贡献最为显著（Manolea等，2010年；Volpicelli-Daley等，2005年）。ARF的招募也可能通过与其24家族成员的相互作用而得以促进（Gommel等，2001年；参见Schuiki和Volchuk，2012年综述）。