Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Mol Biol Cell. 2010 Oct 1;21(19):3386-95. doi: 10.1091/mbc.E10-05-0392. Epub 2010 Aug 4.
The Golgi-associated retrograde protein (GARP) complex mediates tethering and fusion of endosome-derived transport carriers to the trans-Golgi network (TGN). In the yeast Saccharomyces cerevisiae, GARP comprises four subunits named Vps51p, Vps52p, Vps53p, and Vps54p. Orthologues of the GARP subunits, except for Vps51p, have been identified in all other eukaryotes. A yeast two-hybrid screen of a human cDNA library yielded a phylogenetically conserved protein, Ang2/Fat-free, which interacts with human Vps52, Vps53 and Vps54. Human Ang2 is larger than yeast Vps51p, but exhibits significant homology in an N-terminal coiled-coil region that mediates assembly with other GARP subunits. Biochemical analyses show that human Ang2, Vps52, Vps53 and Vps54 form an obligatory 1:1:1:1 complex that strongly interacts with the regulatory Habc domain of the TGN SNARE, Syntaxin 6. Depletion of Ang2 or the GARP subunits similarly impairs protein retrieval to the TGN, lysosomal enzyme sorting, endosomal cholesterol traffic¤ and autophagy. These findings indicate that Ang2 is the missing component of the GARP complex in most eukaryotes.
高尔基相关逆行蛋白 (GARP) 复合物介导内体衍生的运输载体与反式高尔基网络 (TGN) 的锚定和融合。在酵母酿酒酵母中，GARP 由四个亚基组成，分别命名为 Vps51p、Vps52p、Vps53p 和 Vps54p。除了 Vps51p 之外，所有其他真核生物中都鉴定出了 GARP 亚基的同源物。用人 cDNA 文库进行酵母双杂交筛选得到了一个系统发育保守的蛋白质 Ang2/Fat-free，它与人类 Vps52、Vps53 和 Vps54 相互作用。人类 Ang2 比酵母 Vps51p 大，但在介导与其他 GARP 亚基组装的 N 端卷曲螺旋区具有显著同源性。生化分析表明，人 Ang2、Vps52、Vps53 和 Vps54 形成必需的 1:1:1:1 复合物，与 TGN SNARE、Syntaxin 6 的调节 Habc 结构域强烈相互作用。Ang2 或 GARP 亚基的耗竭同样会损害蛋白质向 TGN 的回收、溶酶体酶分拣、内体胆固醇运输和自噬。这些发现表明，Ang2 是大多数真核生物中 GARP 复合物的缺失成分。
