Revilla-Guarinos M Teresa, Martín-García Rebeca, Villar-Tajadura M Antonia, Estravís Miguel, Coll Pedro M, Pérez Pilar
Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Departamento de Microbiología y Genética, Universidad de Salamanca. Salamanca, Spain.
Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC) / Departamento de Microbiología y Genética, Universidad de Salamanca. Salamanca, Spain
Mol Biol Cell. 2016 Mar 9;27(9):1524-35. doi: 10.1091/mbc.E15-12-0818.
Active Cdc42 is essential for the establishment of polarized growth. This GTPase is negatively regulated by the GTPase-activating proteins (GAPs), which are important for the spatial specificity of Cdc42 function. Rga4 is the only GAP described as negative regulator of fission yeast Cdc42. We report here that Rga6 is another fission yeast Cdc42 GAP which shares some functions with Rga4. Cells lacking Rga6 are viable but slightly shorter and broader than wild type, and cells lacking Rga6 and Rga4 simultaneously are rounded. In these cells, active Cdc42 is observed all around the membrane. These additive effects indicate that both GAPs collaborate in the spatial regulation of active Cdc42. Rga6 localizes to the plasma membrane forming clusters different from those formed by Rga4. A polybasic region at the Rga6 C-terminus is responsible for its membrane localization. Rga6-GFP fluorescence decreases considerably at the growing tips, and this decrease is dependent on the actin cables. Notably, in the absence of Rga6 the amplitude of active Cdc42 oscillations at the tips decreases, and less GTP-Cdc42 accumulates at the new end of the cells. We propose here that Rga6 collaborates with Rga4 to spatially restrict active Cdc42 at the cell tips and maintain cell dimensions.
活性Cdc42对于极化生长的建立至关重要。这种GTP酶受GTP酶激活蛋白（GAPs）的负调控，而GAPs对Cdc42功能的空间特异性很重要。Rga4是唯一被描述为裂殖酵母Cdc42负调控因子的GAP。我们在此报告，Rga6是另一种裂殖酵母Cdc42 GAP，与Rga4具有一些共同功能。缺乏Rga6的细胞是存活的，但比野生型略短且宽，同时缺乏Rga6和Rga4的细胞呈圆形。在这些细胞中，在细胞膜周围均可观察到活性Cdc42。这些累加效应表明，两种GAP在活性Cdc42的空间调节中协同作用。Rga6定位于质膜，形成与Rga4形成的簇不同的簇。Rga6 C末端的一个多碱性区域负责其膜定位。Rga6-GFP荧光在生长尖端显著降低，这种降低依赖于肌动蛋白电缆。值得注意的是，在没有Rga6的情况下，尖端活性Cdc42振荡的幅度降低，并且在细胞的新末端积累的GTP-Cdc42减少。我们在此提出，Rga6与Rga4协同作用，在细胞尖端在空间上限制活性Cdc42并维持细胞尺寸。
