The analysis of the transport vesicle tethering mechanism in the Golgi apparatus.

蛋白质在细胞器之间的转运是由转运囊泡介导的。将转运囊泡靶向至正确的膜隔室是由栓系、对接和融合组成的多层过程。高保真的囊泡转移对于细胞器结构的建立和维持以及生物合成的运输都是必不可少的。最近，这一步骤中的许多因素已被确定。作为候选拴系因子提出的蛋白质分为两大类;一类属于长卷曲螺旋蛋白，另一类是多亚基复合物。在高尔基体膜内转运过程中，前者是p115/GM 130/giantin（称为golgins）复合物，后者是保守的寡聚体高尔基体（COG）复合物。p115通过与囊泡上的另外两个高尔基体巨蛋白和高尔基体膜上的GM 130相互作用将COPI囊泡拴系到高尔基体膜。COG复合物包含八个亚基（COG 1-8）。表达突变型COG 1或COG 2的细胞显示异常糖基化。这两组复合物被并行地提出作为候选拴系因素，因此，它仍然是要解决他们是否单独或合作。经酵母双杂交筛选，COG 2为p115结合蛋白。p115和COG 2在体内外均能相互作用，p115缺失的细胞表达COG 2结合结构域p115，导致细胞核周区形成不规则的高尔基体结构，包括聚集的管状结构和泡状结构。这些结果表明p115与COG复合物之间的相互作用是正常高尔基带形成所必需的。

Protein transport between organelle is mediated by transport vesicles. Targeting of transport vesicles to the correct membrane compartment is multi-layered processes consist of tethering, docking and fusion. High fidelity vesicle transfer is essential for the establishment and maintenance of organelle structure and biosynthetic transport.Tethering is the first step of contact between a vesicle and its target membrane prior to fusion. Recently many factors in this step have been identified. Proteins proposed as candidate tethering factors fall into two general classes; one belongs to a class of long coiled-coil proteins, and the other is multi-subunit complexes. In the intra-Golgi membrane transport process, the former is the p 1 15/GM 130/giantin (called golgins) complex and the latter is the conserved oligomeric Golgi (COG) complex. p115 tethers COPI vesicles to the Golgi membrane by interaction with two other golgins giantin on the vesicles and GM130 on the Golgi membrane. The COG complex contains eight subunits (COG 1-8). Cells expressing mutant COG1 or COG2 show abnormal glycosylation. These two sets of complex are proposed in parallel as candidate tethering factors; therefore it is remain to resolve whether they act separately or cooperatively.In this study I have demonstrated two sets of complex interact each other. COG2 was identified as a p 115 binding protein by the yeast two-hybrid screening. The interaction of p 115 and COG2 was showed both in vitro and in vivo.The expression of p115 lacking COG2 binding domain-in p115-depleted cells resulted in the formation of an irregular Golgi structure consist of converged tubular and vesicular structures in the perinuclear area. These results suggest that the interaction between p 115 and the COG complex is Essential for normal Golgi ribbon formation.