Heidelberg University Biochemistry Center (BZH), University of Heidelberg, INF 364, 69120 Heidelberg, Germany.
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
J Biol Chem. 2011 Oct 14;286(41):35634-35642. doi: 10.1074/jbc.M111.261800. Epub 2011 Aug 15.
Newly synthesized proteins and lipids are transported in vesicular carriers along the secretory pathway. Arfs (ADP-ribosylation factors), a family of highly conserved GTPases within the Ras superfamily, control recruitment of molecular coats to membranes, the initial step of coated vesicle biogenesis. Arf1 and coatomer constitute the minimal cytosolic machinery leading to COPI vesicle formation from Golgi membranes. Although some functional redundancies have been suggested, other Arf isoforms have been poorly analyzed in this context. In this study, we found that Arf1, Arf4, and Arf5, but not Arf3 and Arf6, associate with COPI vesicles generated in vitro from Golgi membranes and purified cytosol. Using recombinant myristoylated proteins, we show that Arf1, Arf4, and Arf5 each support COPI vesicle formation individually. Unexpectedly, we found that Arf3 could also mediate vesicle biogenesis. However, Arf3 was excluded from the vesicle fraction in the presence of the other isoforms, highlighting a functional competition between the different Arf members.
新合成的蛋白质和脂质沿着分泌途径在囊泡载体中运输。Arfs（ADP-核糖基化因子）是 Ras 超家族中高度保守的 GTPase 家族，控制着分子外套在膜上的募集，这是有被膜囊泡生物发生的初始步骤。Arf1 和衣被蛋白复合物构成了最小的细胞质机制，导致从高尔基体膜形成 COPI 囊泡。尽管已经提出了一些功能冗余，但在这种情况下，其他 Arf 同工型的分析还不够完善。在这项研究中，我们发现 Arf1、Arf4 和 Arf5，但不是 Arf3 和 Arf6，与从高尔基体膜和纯化的细胞质中体外生成的 COPI 囊泡结合。使用重组的豆蔻酰化蛋白，我们表明 Arf1、Arf4 和 Arf5 各自都能单独支持 COPI 囊泡的形成。出乎意料的是，我们发现 Arf3 也可以介导囊泡的生物发生。然而，在存在其他同工型的情况下，Arf3 被排除在囊泡部分之外，这突出了不同 Arf 成员之间的功能竞争。
