Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA.
Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA
J Cell Sci. 2020 Apr 14;133(7):jcs241513. doi: 10.1242/jcs.241513.
All cells establish and maintain an axis of polarity that is critical for cell shape and progression through the cell cycle. A well-studied example of polarity establishment is bud emergence in the yeast , which is controlled by the Rho GTPase Cdc42p. The prevailing view of bud emergence does not account for regulation by extrinsic cues. Here, we show that the filamentous growth mitogen activated protein kinase (fMAPK) pathway regulates bud emergence under nutrient-limiting conditions. The fMAPK pathway regulated the expression of polarity targets including the gene encoding a direct effector of Cdc42p, Gic2p. The fMAPK pathway also stimulated GTP-Cdc42p levels, which is a critical determinant of polarity establishment. The fMAPK pathway activity was spatially restricted to bud sites and active during the period of the cell cycle leading up to bud emergence. Time-lapse fluorescence microscopy showed that the fMAPK pathway stimulated the rate of bud emergence during filamentous growth. Unregulated activation of the fMAPK pathway induced multiple rounds of symmetry breaking inside the growing bud. Collectively, our findings identify a new regulatory aspect of bud emergence that sensitizes this essential cellular process to external cues.
所有细胞都建立并维持极性轴，这对于细胞的形状和细胞周期的进程至关重要。极性建立的一个很好的研究例子是酵母中的芽出现，它由 Rho GTPase Cdc42p 控制。芽出现的主流观点没有考虑到外部线索的调节。在这里，我们表明丝状生长有丝分裂原激活的蛋白激酶（fMAPK）途径在营养限制条件下调节芽出现。fMAPK 途径调节极性靶标包括编码 Cdc42p 直接效应物的基因 Gic2p 的表达。fMAPK 途径还刺激了 GTP-Cdc42p 水平，这是极性建立的关键决定因素。fMAPK 途径的活性在芽位点受到空间限制，并在导致芽出现的细胞周期期间活跃。延时荧光显微镜显示，fMAPK 途径在丝状生长过程中刺激了芽出现的速度。fMAPK 途径的不受调节的激活诱导了生长芽内的多次对称破坏。总的来说，我们的发现确定了芽出现的一个新的调节方面，使这个基本的细胞过程对外部线索敏感。
