Monier Solange, Jollivet Florence, Janoueix-Lerosey Isabelle, Johannes Ludger, Goud Bruno
Laboratories Molecular mechanisms of intracellular transport, Institut Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
Traffic. 2002 Apr;3(4):289-97. doi: 10.1034/j.1600-0854.2002.030406.x.
Rab6 GTPase regulates intracellular transport at the level of the Golgi complex. Using the yeast two-hybrid screen, we have isolated two clones that specifically interact with the three isoforms of Rab6 present in mammalian cells (Rab6A, A' and B). The cDNAs encode two proteins of 976 and 1120 amino acids (calculated molecular mass of 112 and 128 kDa, respectively) that we named Rab6IP2A and Rab6IP2B (for Rab6 Interacting Protein 2). The two proteins likely correspond to spliced variants of the same gene. Rab6IP2s have no significant homology with other known proteins, including Rab effectors or partners. They are ubiquitously expressed, mostly cytosolic and found in high molecular mass complexes in brain cytosol. We show that Rab6IP2s can be recruited on Golgi membranes in a Rab6:GTP-dependent manner. The overexpression of any form of Rab6IP2 has no detectable effect on the secretory pathway. In contrast, the retrograde transport of the Shiga toxin B subunit between the plasma membrane and the Golgi complex is partly inhibited in cells overexpressing the Rab6-binding domain of Rab6IP2. Our data suggest that Rab6IP2s is involved in the pathway regulated by Rab6A'.
Rab6 GTP酶在高尔基体复合体水平调节细胞内运输。利用酵母双杂交筛选，我们分离出了两个与哺乳动物细胞中存在的三种Rab6同工型（Rab6A、A'和B）特异性相互作用的克隆。这些cDNA编码两种分别含有976和1120个氨基酸的蛋白质（计算分子量分别为112和128 kDa），我们将其命名为Rab6IP2A和Rab6IP2B（Rab6相互作用蛋白2）。这两种蛋白质可能对应于同一基因的剪接变体。Rab6IP2与其他已知蛋白质（包括Rab效应器或伴侣）没有明显的同源性。它们广泛表达，主要存在于细胞质中，并在脑细胞质的高分子量复合物中发现。我们发现Rab6IP2可以以Rab6:GTP依赖的方式被募集到高尔基体膜上。任何形式的Rab6IP2的过表达对分泌途径都没有可检测到的影响。相反，在过表达Rab6IP2的Rab6结合结构域的细胞中，志贺毒素B亚基在质膜和高尔基体复合体之间的逆行运输受到部分抑制。我们的数据表明Rab6IP2参与了由Rab6A'调节的途径。
