A protein conjugation system essential for autophagy
A protein conjugation system essential for autophagy
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DOI：
10.1038/26506
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发表时间：
1998-09-24
期刊：
影响因子：
64.8
通讯作者：
Ohsumi, Y
中科院分区：
文献类型：
--
作者：
Mizushima, N;Noda, T;Ohsumi, Y
自噬是蛋白质大量降解的过程，其中细胞的细胞质组分被称为自噬体的双膜结构包围，用于递送到溶酶体或空泡进行降解（1-4）。这个过程对于饥饿和细胞分化期间的生存至关重要。在高等真核生物中还没有鉴定出参与自噬的分子。我们已经分离了14个酿酒酵母的自噬缺陷（apg）突变体（5），并在分子水平上研究了自噬过程（6-9）。我们在这里表明，一个独特的共价修饰系统是必不可少的自噬发生。Apg 12（一种186个氨基酸的蛋白质）的羧基末端甘氨酸残基与Apg 5（一种294个氨基酸的蛋白质）的残基149处的赖氨酸缀合。在apg突变体中，我们发现apg 7和apg 10不能形成Apg 5/Apg 12缀合物。通过对APG 7基因的克隆，我们发现APG 7是一种泛素-E1样酶。这种结合可以在体外重建，并依赖于ATP。据我们所知，这是第一个报告的蛋白质无关的泛素，使用泛素样共轭系统。此外，Apg 5和Apg 12具有哺乳动物同源物，表明这种新的修饰系统从酵母到哺乳动物细胞是保守的。
Autophagy is a process for the bulk degradation of proteins, in which cytoplasmic components of the cell are enclosed by double-membrane structures known as autophagosomes for delivery to lysosomes or vacuoles for degradation(1-4). This process is crucial for survival during starvation and cell differentiation. No molecules have been identified that are involved in autophagy in higher eukaryotes. We have isolated 14 autophagy-defective (apg) mutants of the yeast Saccharomyces cerevisiae(5) and examined the autophagic process at the molecular level(6-9). We show here that a unique covalent-modification system is essential for autophagy to occur. The carboxy-terminal glycine residue of Apg12, a 186-amino-acid protein, is conjugated to a lysine at residue 149 of Apg5, a 294-amino-acid protein. Of the apg mutants, we found that apg7 and apg10 were unable to form an Apg5/Apg12 conjugate. By cloning APG7, we discovered that Apg7 is a ubiquitin-E1-like enzyme. This conjugation can be reconstituted in vitro and depends on ATP. To our knowledge, this is the first report of a protein unrelated to ubiquitin that uses a ubiquitination-like conjugation system. Furthermore, Apg5 and Apg12, have mammalian homologues, suggesting that this new modification system is conserved from yeast to mammalian cells.