Liang Yongheng, Morozova Nadya, Tokarev Andrei A, Mulholland Jonathan W, Segev Nava
Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois, Chicago, IL 60607, USA.
Mol Biol Cell. 2007 Jul;18(7):2533-41. doi: 10.1091/mbc.e07-03-0221. Epub 2007 May 2.
The conserved modular complex TRAPP is a guanine nucleotide exchanger (GEF) for the yeast Golgi Ypt-GTPase gatekeepers. TRAPP I and TRAPP II share seven subunits and act as GEFs for Ypt1 and Ypt31/32, respectively, which in turn regulate transport into and out of the Golgi. Trs65/Kre11 is one of three TRAPP II-specific subunits. Unlike the other two subunits, Trs120 and Trs130, Trs65 is not essential for viability, is conserved only among some fungi, and its contribution to TRAPP II function is unclear. Here, we provide genetic, biochemical, and cellular evidence for the role of Trs65 in TRAPP II function. First, like Trs130, Trs65 localizes to the trans-Golgi. Second, TRS65 interacts genetically with TRS120 and TRS130. Third, Trs65 interacts physically with Trs120 and Trs130. Finally, trs65 mutant cells have low levels of Trs130 protein, and they are defective in the GEF activity of TRAPP II and the intracellular distribution of Ypt1 and Ypt31/32. Together, these results show that Trs65 plays a role in the Ypt GEF activity of TRAPP II in concert with the two other TRAPP II-specific subunits. Elucidation of the role played by Trs65 in intracellular trafficking is important for understanding how this process is coordinated with two other processes in which Trs65 is implicated: cell wall biogenesis and stress response.
保守的模块化复合物TRAPP是酵母高尔基体Ypt - GTP酶守门蛋白的鸟嘌呤核苷酸交换因子（GEF）。TRAPP I和TRAPP II共有七个亚基，分别作为Ypt1和Ypt31/32的GEF，进而调节进出高尔基体的转运。Trs65/Kre11是TRAPP II特异性的三个亚基之一。与其他两个亚基Trs120和Trs130不同，Trs65对细胞活力不是必需的，仅在某些真菌中保守，其对TRAPP II功能的贡献尚不清楚。在此，我们提供了关于Trs65在TRAPP II功能中作用的遗传学、生物化学和细胞证据。首先，与Trs130一样，Trs65定位于反式高尔基体。其次，TRS65与TRS120和TRS130发生遗传相互作用。第三，Trs65与Trs120和Trs130发生物理相互作用。最后，trs65突变细胞中Trs130蛋白水平较低，并且它们在TRAPP II的GEF活性以及Ypt1和Ypt31/32的细胞内分布方面存在缺陷。总之，这些结果表明Trs65与TRAPP II的另外两个特异性亚基协同作用，在TRAPP II的Ypt GEF活性中发挥作用。阐明Trs65在细胞内运输中的作用对于理解该过程如何与Trs65涉及的其他两个过程协调至关重要：细胞壁生物合成和应激反应。
