Requirement for the polarisome and formin function in Ssk2p-mediated actin recovery from osmotic stress in Saccharomyces cerevisiae
Requirement for the polarisome and formin function in Ssk2p-mediated actin recovery from osmotic stress in Saccharomyces cerevisiae
复制标题
DOI：
10.1534/genetics.106.063370
复制
发表时间：
2007-04-01
期刊：
影响因子：
3.3
通讯作者：
Amberg, David C.
中科院分区：
文献类型：
--
作者：
Bettinger, Blaine T.;Clark, Michael G.;Amberg, David C.
渗透应激通过一种尚不清楚的机制，在肌动蛋白细胞骨架解体的同时，诱导适应性丝裂原活化蛋白激酶通路的激活。我们以前已经证明，保守的肌动蛋白相互作用的MAP激酶Ssk2p/MEKK4是酿酒酵母高渗透压甘油(HOG)MAPK途径的成员，介导渗透胁迫后肌动蛋白细胞骨架的恢复。在这项研究中，我们使用了体外激酶分析来证明Ssk2p的活性是通过一种非规范的、不依赖于Ssk1p的机制为肌动蛋白恢复途径激活的。我们的工作还表明，Ssk2p需要极化体蛋白Bud6p和Pea2p来促进高效的极化肌动蛋白重组，但Ssk2p的过度表达可以绕过这一要求。Form in(BNI1或BNR1)和原肌球蛋白功能也是肌动蛋白恢复所必需的，但与Bud6p和Pea2p不同的是，Ssk2p的过度表达不能绕过这些要求。这些结果表明，Ssk2p作用于Bud6p和Pea2p的下游和原肌球蛋白的上游，可能是通过上调Forins的肌动蛋白成核活性来推动肌动蛋白的恢复。
Osmotic stress induces activation of an adaptive mitogen-activated protein kinase pathway in concert with disassembly of the actin cytoskeleton by a mechanism that is not understood. We have previously shown that the conserved actin-interacting MAP kinase kinase kinase Ssk2p/MEKK4, a member of the high-osmolarity glycerol (HOG) MAPK pathway of Saccharomyces cerevisiae, mediates recovery of the actin cytoskeleton following osmotic stress. In this study, we have employed in vitro kinase assays to show that Ssk2p kinase activity is activated for the actin recovery pathway via a noncanonical, Ssk1p-independent mechanism. Our work also shows that Ssk2p requires the polarisome proteins Bud6p and Pea2p to promote efficient, polarized actin reassembly but that this requirement can be bypassed by overexpression of Ssk2p. Formin (BNI1 or BNR1) and tropomyosin functions are also required for actin recovery but, unlike for Bud6p and Pea2p, these requirements cannot be bypassed by overexpression of Ssk2p. These results suggest that Ssk2p acts downstream of Bud6p and Pea2p and upstream of tropomyosin to drive actin recovery, possibly by upregulating the actin nucleation activity of the formins.