Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p.
Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p.
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DOI：
10.1091/mbc.e02-11-0747
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发表时间：
2003-04
影响因子：
3.3
通讯作者：
T. Yuzyuk;David C. Amberg
中科院分区：
文献类型：
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作者：
T. Yuzyuk;David C. Amberg
渗透胁迫导致肌动蛋白细胞骨架分解、细胞周期阻滞和高渗透压生长丝裂原激活蛋白激酶途径的激活。先前的研究表明，Ssk2p是一种高渗透压生长途径的丝裂原激活蛋白激酶激酶，可促进肌动蛋白细胞骨架恢复到细胞周期晚期，渗透胁迫酵母细胞的颈部。本文提供的数据检验了Ssk2p在细胞周期早期肌动蛋白恢复中的作用。我们发现在细胞周期的所有阶段肌动蛋白的恢复都不受Ssk2p的已知激活因子Ssk1p的控制，而是需要Ssk2p的极化分布以及它的肌动蛋白相互作用和激酶活性。应力诱导的Ssk2p定位到颈部需要septin Shs1p，而定位到芽皮质依赖于极性支架蛋白Spa2p。sp2delta细胞和ssk2delta细胞一样，在渗透胁迫下肌动蛋白恢复有缺陷。这些spa2delta缺陷可以通过过表达具有催化活性的Ssk2p来抑制。此外，GST-Ssk2p可以从渗透胁迫细胞的提取物中析出Spa2p。Ssk2p介导的肌动蛋白恢复途径似乎是保守的；MTK1是一种p38应激反应通路和Ssk2p同源物的人丝裂原激活蛋白激酶激酶，也能够定位于极化生长位点，与肌动蛋白和Spa2p形成复合物，并在渗透应激的ssk2delta和spa2delta酵母细胞中补充肌动蛋白恢复缺陷。我们假设渗透应力诱导的肌动蛋白分解导致Ssk2p-肌动蛋白复合物的形成和Ssk2p的极化定位。极化Ssk2p与芽中的支架蛋白Spa2p和颈中的支架蛋白Shs1p结合，允许Ssk2p调节参与极化肌动蛋白组装的底物。
Osmotic stress causes actin cytoskeleton disassembly, a cell cycle arrest, and activation of the high osmolarity growth mitogen-activated protein kinase pathway. A previous study showed that Ssk2p, a mitogen-activated protein kinase kinase kinase of the high osmolarity growth pathway, promotes actin cytoskeleton recovery to the neck of late cell cycle, osmotically stressed yeast cells. Data presented herein examined the role of Ssk2p in actin recovery early in the cell cycle. We found that actin recovery at all stages of the cell cycle is not controlled by Ssk1p, the known activator of Ssk2p, but required a polarized distribution of Ssk2p as well as its actin-interacting and kinase activity. Stress-induced localization of Ssk2p to the neck required the septin Shs1p, whereas localization to the bud cortex depended on the polarity scaffold protein Spa2p. spa2delta cells, like ssk2delta cells, were defective for actin recovery from osmotic stress. These spa2delta defects could be suppressed by overexpression of catalytically active Ssk2p. Furthermore, Spa2p could be precipitated by GST-Ssk2p from extracts of osmotically stressed cells. The Ssk2p mediated actin recovery pathway seems to be conserved; MTK1, a human mitogen-activated protein kinase kinase kinase of the p38 stress response pathway and Ssk2p homolog, was also able to localize at polarized growth sites, form a complex with actin and Spa2p, and complement actin recovery defects in osmotically stressed ssk2delta and spa2delta yeast cells. We hypothesize that osmotic stress-induced actin disassembly leads to the formation of an Ssk2p-actin complex and the polarized localization of Ssk2p. Polarized Ssk2p associates with the scaffold protein Spa2p in the bud and Shs1p in the neck, allowing Ssk2p to regulate substrates involved in polarized actin assembly.