Physiological pH and acidic phospholipids contribute to substrate specificity in lipidation of Atg8
Physiological pH and acidic phospholipids contribute to substrate specificity in lipidation of Atg8
复制标题
DOI：
10.1074/jbc.m801836200
复制
发表时间：
2008-08-08
影响因子：
4.8
通讯作者：
Ohsumi, Yoshinori
中科院分区：
文献类型：
--
作者：
Oh-oka, Kyoko;Nakatogawa, Hitoshi;Ohsumi, Yoshinori
酵母 Atg8 及其哺乳动物同源物 LC3 是参与自噬的类泛素蛋白，自噬是液泡/溶酶体中胞质成分降解的主要途径。虽然脂质磷脂酰乙醇胺 (PE) 被确定为其缀合反应的唯一体内靶标，但体外研究表明，相同的系统可以像 PE 一样有效地介导这些蛋白质与磷脂酰丝氨酸的缀合。在这里，我们发现，与 PE 缀合相反，Atg8 的体外磷脂酰丝氨酸缀合在生理 pH 下受到显着抑制。此外，向脂质体添加酸性磷脂也导致Atg8-PE缀合物的优先形成。我们已经成功捕获了真正的硫酯中间体，使我们能够阐明缀合反应中的哪一步受到 pH 值和膜脂组成变化的影响。我们认为这些因素有助于细胞中 Atg8-PE 的选择性形成。
Yeast Atg8 and its mammalian homolog LC3 are ubiquitin-like proteins involved in autophagy, a primary pathway for degradation of cytosolic constituents in vacuoles/lysosomes. Whereas the lipid phosphatidylethanolamine (PE) was identified as the sole in vivo target of their conjugation reactions, in vitro studies showed that the same system can mediate the conjugation of these proteins with phosphatidylserine as efficiently as with PE. Here, we show that, in contrast to PE conjugation, the in vitro phosphatidylserine conjugation of Atg8 is markedly suppressed at physiological pH. Furthermore, the addition of acidic phospholipids to liposomes also results in the preferential formation of the Atg8-PE conjugate. We have successfully captured authentic thioester intermediates, allowing us to elucidate which step in the conjugation reaction is affected by these changes in pH and membrane lipid composition. We propose that these factors contribute to the selective formation of Atg8-PE in the cell.