Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, 08003 Barcelona, Spain.
Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas, Universidad de Salamanca, 37007 Salamanca, Spain.
Cell Rep. 2021 Nov 2;37(5):109951. doi: 10.1016/j.celrep.2021.109951.
Cdc42 GTPase rules cell polarity and growth in fission yeast. It is negatively and positively regulated by GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs), respectively. Active Cdc42-GTP localizes to the poles, where it associates with numerous proteins constituting the polarity module. However, little is known about its downregulation. We describe here that oxidative stress causes Sty1-kinase-dependent Cdc42 inactivation at cell poles. Both the amount of active Cdc42 at tips and cell length inversely correlate with Sty1 activity, explaining the elongated morphology of Δsty1 cells. We have created stress-blinded cell poles either by eliminating two Cdc42 GAPs or through the constitutive tethering of Gef1 to cell tips, and we biochemically demonstrate that the GAPs Rga3/6 and the GEF Gef1 are direct substrates of Sty1. We propose that phosphorylation of Rga3/6 and Gef1 mediates the Sty1-dependent inhibition of Cdc42 at cell tips, halting polarized growth during stress adaptation.
Cdc42 GTP 酶调控着裂殖酵母的细胞极性和生长。它分别被 GTP 酶激活蛋白 (GAPs) 和鸟嘌呤核苷酸交换因子 (GEFs) 负向和正向调控。活性 Cdc42-GTP 定位于两极，与构成极性模块的众多蛋白质结合。然而，关于其下调机制知之甚少。我们在这里描述了氧化应激导致 Sty1-激酶依赖性 Cdc42 在细胞两极失活。尖端的活性 Cdc42 量和细胞长度呈反比，与 Sty1 活性相关，这解释了Δsty1 细胞的伸长形态。我们通过消除两个 Cdc42 GAP 或通过 Gef1 组成型固定在细胞尖端，创造了应激致盲的细胞两极，并通过生物化学手段证明了 GAPs Rga3/6 和 GEF Gef1 是 Sty1 的直接底物。我们提出，Rga3/6 和 Gef1 的磷酸化介导了 Sty1 依赖性的 Cdc42 在细胞尖端的抑制，从而在应激适应过程中停止极化生长。
