Du Fei, Edwards Kimberly, Shen Zhouxin, Sun Binggang, De Lozanne Arturo, Briggs Steven, Firtel Richard A
Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0380, USA.
EMBO J. 2008 Aug 6;27(15):2064-76. doi: 10.1038/emboj.2008.131. Epub 2008 Jul 17.
The contractile vacuole (CV) system is the osmoregulatory organelle required for survival for many free-living cells under hypotonic conditions. We identified a new CV regulator, Disgorgin, a TBC-domain-containing protein, which translocates to the CV membrane at the late stage of CV charging and regulates CV-plasma membrane fusion and discharging. disgorgin(-) cells produce large CVs due to impaired CV-plasma membrane fusion. Disgorgin is a specific GAP for Rab8A-GTP, which also localizes to the CV and whose hydrolysis is required for discharging. We demonstrate that Drainin, a previously identified TBC-domain-containing protein, lies upstream from Disgorgin in this pathway. Unlike Disgorgin, Drainin lacks GAP activity but functions as a Rab11A effector. The BEACH family proteins LvsA and LvsD were identified in a suppressor/enhancer screen of the disgorgin(-) large CV phenotype and demonstrated to have distinct functions in regulating CV formation. Our studies help define the pathways controlling CV function.
收缩泡（CV）系统是许多自由生活细胞在低渗条件下生存所必需的渗透调节细胞器。我们鉴定出一种新的CV调节因子Disgorgin，一种含TBC结构域的蛋白质，它在CV充水后期转运至CV膜，并调节CV与质膜的融合及排空。由于CV与质膜融合受损，disgorgin（-）细胞产生大型CV。Disgorgin是Rab8A-GTP的特异性GAP，它也定位于CV，其水解对于排空是必需的。我们证明，先前鉴定的含TBC结构域的蛋白质Drainin在此途径中位于Disgorgin的上游。与Disgorgin不同，Drainin缺乏GAP活性，但作为Rab11A效应器发挥作用。在对disgorgin（-）大型CV表型的抑制/增强筛选中鉴定出BEACH家族蛋白LvsA和LvsD，并证明它们在调节CV形成中具有不同的功能。我们的研究有助于确定控制CV功能的途径。
