Study on simultaneous yet independent regulation of actin cytoskeletal organization and translation initiation by environmental stress

在酿酒酵母中，急性葡萄糖剥夺迅速但短暂地使肌动蛋白细胞骨架去极化并抑制翻译起始。快速肌动蛋白去极化和葡萄糖去除时的翻译抑制都不会发生在reg1破坏物中，reg1在葡萄糖抑制中存在缺陷，或者在tpk1^w突变体中，cAPK活性较弱。在没有额外葡萄糖的情况下，肌动蛋白极化或翻译起始的恢复依赖于呼吸作用、Snf1p蛋白激酶和转录因子Msn2p和Msn4p。葡萄糖对葡萄糖饥饿细胞的读取导致肌动蛋白极化的快速恢复以及没有呼吸的翻译起始。这些结果表明，肌动蛋白极化和翻译起始的同时调控可分为三个反应：(1)葡萄糖去除后依赖Reg1p和cAPK的快速关闭反应，(2)无葡萄糖时依赖Snf1p和Msn2p/4p的缓慢适应反应，以及(3)葡萄糖补充后的快速恢复反应。去除葡萄糖后，rom2干扰物会迅速抑制翻译起始，该干扰物在肌动蛋白快速去极化方面存在缺陷，而pop2/caf1干扰物会发生肌动蛋白快速去极化，该干扰物在快速抑制翻译起始方面存在缺陷。因此，翻译起始和肌动蛋白极化似乎同时但独立地受到葡萄糖剥夺的调节。

Acute glucose deprivation rapidly but transiently depolarizes the actin cytoskeleton and inhibits translation initiation in Saccharomyces cerevisiae. Neither rapid actin depolarization nor translation inhibition upon glucose removal occurs in a reg1 disruptant, which is defective in glucose repression, or in the tpk1^w mutant, which has weak cAPK activity. In the absence of additional glucose, recovery of either actin polarization or translation initiation relies upon respiration, the Snf1p protein kinase, and the transcription factors Msn2p and Msn4p. The readdition of glucose to glucose-starved cells causes a rapid recovery of actin polarization as well as translation initiation without respiration. These results indicate that the simultaneous regulation of actin polarization and translation initiation is divided into three reactions : (1)rapid shutdown depending on Reg1p and cAPK after glucose removal, (2)slow adaptation depending on Snf1p and Msn2p/4p in the absence of glucose, and (3)rapid recovery upon readdition of glucose. Upon glucose removal, translation initiation is rapidly inhibited in a rom2 disruptant, which is defective in rapid actin depolarization, whereas rapid actin depolarization occurs in a pop2/caf1 disruptant, which is defective in rapid inhibition of translation initiation. Thus, translation initiation and actin polarization appear to be simultaneously but independently regulated by glucose deprivation.