Steegmaier M, Klumperman J, Foletti D L, Yoo J S, Scheller R H
Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305-5345, USA.
Mol Biol Cell. 1999 Jun;10(6):1957-72. doi: 10.1091/mbc.10.6.1957.
The trans-Golgi network (TGN) plays a pivotal role in directing proteins in the secretory pathway to the appropriate cellular destination. VAMP4, a recently discovered member of the vesicle-associated membrane protein (VAMP) family of trafficking proteins, has been suggested to play a role in mediating TGN trafficking. To better understand the function of VAMP4, we examined its precise subcellular distribution. Indirect immunofluorescence and electron microscopy revealed that the majority of VAMP4 localized to tubular and vesicular membranes of the TGN, which were in part coated with clathrin. In these compartments, VAMP4 was found to colocalize with the putative TGN-trafficking protein syntaxin 6. Additional labeling was also present on clathrin-coated and noncoated vesicles, on endosomes and the medial and trans side of the Golgi complex, as well as on immature secretory granules in PC12 cells. Immunoprecipitation of VAMP4 from rat brain detergent extracts revealed that VAMP4 exists in a complex containing syntaxin 6. Converging lines of evidence implicate a role for VAMP4 in TGN-to-endosome transport.
反式高尔基体网络（TGN）在将分泌途径中的蛋白质导向适当的细胞目的地方面起着关键作用。VAMP4是囊泡相关膜蛋白（VAMP）家族中最近发现的一种运输蛋白，有人认为它在介导TGN运输中发挥作用。为了更好地理解VAMP4的功能，我们研究了其精确的亚细胞分布。间接免疫荧光和电子显微镜显示，大多数VAMP4定位于TGN的管状和囊泡膜上，这些膜部分被网格蛋白包被。在这些区室中，发现VAMP4与假定的TGN运输蛋白Syntaxin 6共定位。在网格蛋白包被和未包被的囊泡、内体以及高尔基体复合体的中间和反面，以及PC12细胞中的未成熟分泌颗粒上也有额外的标记。从大鼠脑去污剂提取物中免疫沉淀VAMP4表明，VAMP4存在于一个包含Syntaxin 6的复合物中。越来越多的证据表明VAMP4在TGN到内体的运输中起作用。
