School of Natural and Computational Sciences, Massey University, Auckland, New Zealand.
School of Biological Sciences, Seoul National University, Korea.
FEBS Lett. 2021 Jul;595(14):1886-1901. doi: 10.1002/1873-3468.14137. Epub 2021 Jun 28.
Eukaryotes harbour a conserved signalling pathway, called General Amino Acid Control (GAAC) in Saccharomyces cerevisiae, for overcoming amino acid starvation. Upon starvation, the protein kinase Gcn2, which phosphorylates the eukaryotic translation initiation factor eIF2α, becomes stimulated to trigger the GAAC response. Genetic studies suggest that Yih1, which is the yeast homolog of mammalian IMPACT and which binds monomeric actin, inhibits Gcn2 when released from actin. Here, we found that D56A substitution in actin (the act1-9 allele) leads to reduced eIF2α phosphorylation, suggesting that the Asp56 residue is required for full Gcn2 activation. In the act1-9 mutant, Yih1 overexpression further enhanced the sensitivity to amino acid starvation-inducing drugs and further impaired eIF2α phosphorylation, suggesting that Gcn2 inhibition was mediated via Yih1. The D56A substitution may impair the actin-Yih1 interaction, directly or indirectly, thereby increasing the amount of Yih1 available to inhibit Gcn2.
真核生物中存在一种保守的信号通路，称为酿酒酵母中的一般氨基酸控制 (GAAC)，用于克服氨基酸饥饿。在饥饿时，磷酸化真核翻译起始因子 eIF2α 的蛋白激酶 Gcn2 被激活，引发 GAAC 反应。遗传研究表明，Yih1 是哺乳动物 IMPACT 的酵母同源物，与单体肌动蛋白结合，当从肌动蛋白中释放时抑制 Gcn2。在这里，我们发现肌动蛋白中的 D56A 取代（act1-9 等位基因）导致 eIF2α 磷酸化减少，表明 Asp56 残基对于 Gcn2 的完全激活是必需的。在 act1-9 突变体中，Yih1 的过表达进一步增强了对氨基酸饥饿诱导药物的敏感性，并进一步损害了 eIF2α 的磷酸化，表明 Gcn2 的抑制是通过 Yih1 介导的。D56A 取代可能直接或间接地破坏肌动蛋白-Yih1 相互作用，从而增加可用于抑制 Gcn2 的 Yih1 的数量。
