Watson Peter, Townley Anna K, Koka Pratyusha, Palmer Krysten J, Stephens David J
Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
Traffic. 2006 Dec;7(12):1678-87. doi: 10.1111/j.1600-0854.2006.00493.x. Epub 2006 Sep 27.
The selective export of proteins and lipids from the endoplasmic reticulum (ER) is mediated by the coat protein complex II (COPII) that assembles onto the ER membrane. In higher eukaryotes, COPII proteins assemble at discrete sites on the membrane known as ER exit sites (ERES). Here, we identify Sec16 as the protein that defines ERES in mammalian cells. Sec16 localizes to ERES independent of Sec23/24 and Sec13/31. Overexpression, and to a lesser extent, small interfering RNA depletion of Sec16, both inhibit ER-to-Golgi transport suggesting that Sec16 is required in stoichiometric amounts. Sar1 activity is required to maintain the localization of Sec16 at discrete locations on the ER membrane, probably through preventing its dissociation. Our data suggest that Sar1-GTP-dependent assembly of Sec16 on the ER membrane forms an organized scaffold defining an ERES.
内质网（ER）中蛋白质和脂质的选择性输出由组装在内质网膜上的II型被膜蛋白复合体（COPII）介导。在高等真核生物中，COPII蛋白在膜上离散的位点组装，这些位点被称为内质网出口位点（ERES）。在这里，我们确定Sec16是在哺乳动物细胞中定义ERES的蛋白质。Sec16定位于ERES，不依赖于Sec23/24和Sec13/31。Sec16的过表达以及程度较轻的小干扰RNA介导的Sec16缺失，均抑制了从内质网到高尔基体的转运，这表明Sec16需要化学计量的量。Sar1活性可能通过防止Sec16解离，来维持其在内质网膜上离散位置的定位。我们的数据表明，Sar1-GTP依赖的Sec16在内质网膜上的组装形成了一个有组织的支架，定义了一个ERES。
