Wang Huamin, Jiang Yu
Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
Mol Cell Biol. 2003 May;23(9):3116-25. doi: 10.1128/MCB.23.9.3116-3125.2003.
In Saccharomyces cerevisiae, the Tor proteins mediate a wide spectrum of growth-related cellular processes in response to nutrients. The pleiotropic role of the Tor proteins is mediated, at least in part, by type 2A protein phosphatases (PP2A) and 2A-like protein phosphatases. Tor-mediated signaling activity promotes the interaction of phosphatase-interacting protein Tap42 with PP2A and 2A-like protein phosphatases. The distinct complexes formed between Tap42 and different phosphatases mediate various cellular events and modulate phosphorylation levels of many downstream factors in the Tor pathway in a Tor-dependent and rapamycin-sensitive manner. In this study, we demonstrate that the interaction between Tap42 and the catalytic subunits of PP2A (PP2Ac) is required for cell cycle-dependent distribution of actin. We show that mutations in PP2Ac and Tap42 that perturb the interaction cause random distribution of actin during the cell cycle and that overexpression of the Rho2 GTPase suppresses the actin defects associated with the mutants. Our findings suggest that the Tap42-PP2Ac complex regulates the actin cytoskeleton via a Rho GTPase-dependent mechanism. In addition, we provide evidence that PP2A activity plays a negative role in controlling the actin cytoskeleton and, possibly, in regulation of the G(2)/M transition of the cell cycle.
在酿酒酵母中,Tor蛋白介导多种与生长相关的细胞过程以响应营养物质。Tor蛋白的多效性作用至少部分是由2A型蛋白磷酸酶(PP2A)和2A样蛋白磷酸酶介导的。Tor介导的信号活性促进磷酸酶相互作用蛋白Tap42与PP2A和2A样蛋白磷酸酶的相互作用。Tap42与不同磷酸酶之间形成的独特复合物介导各种细胞事件,并以Tor依赖性和雷帕霉素敏感性方式调节Tor途径中许多下游因子的磷酸化水平。在本研究中,我们证明Tap42与PP2A催化亚基(PP2Ac)之间的相互作用是肌动蛋白细胞周期依赖性分布所必需的。我们表明,扰乱这种相互作用的PP2Ac和Tap42突变会导致细胞周期中肌动蛋白的随机分布,并且Rho2 GTP酶的过表达会抑制与突变体相关的肌动蛋白缺陷。我们的研究结果表明,Tap42-PP2Ac复合物通过Rho GTP酶依赖性机制调节肌动蛋白细胞骨架。此外,我们提供证据表明PP2A活性在控制肌动蛋白细胞骨架以及可能在调节细胞周期的G(2)/M转变中起负作用。