The Atg12-Atg5 conjugate has a novel E3-like activity for protein lipidation in autophagy
The Atg12-Atg5 conjugate has a novel E3-like activity for protein lipidation in autophagy
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DOI：
10.1074/jbc.c700195200
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发表时间：
2007-12-28
影响因子：
4.8
通讯作者：
Ohsumi, Yoshinori
中科院分区：
文献类型：
--
作者：
Hanada, Takao;Noda, Nobuo N.;Ohsumi, Yoshinori
自噬是真核细胞中的大量降解过程;自噬体包围细胞质组分以在溶酶体/液泡中降解。自噬体的形成需要两个泛素样结合系统，Atg 12和Atg 8系统，这与自噬体膜的扩张密切相关。以前的研究表明，这些系统之间有一个层次结构; Atg 12系统位于上游的Atg 8系统的背景下，Atg蛋白的组织。然而，具体的分子关系尚不清楚。在这里，我们显示使用体外Atg 8缀合系统，Atg 12-Atg 5缀合物，而不是未缀合的Atg 12或Atg 5，强烈增强了另一种缀合物Atg 8-PE的形成。Atg 12-Atg 5缀合物通过刺激Atg 3的活性促进Atg 8从Atg 3转移到底物磷脂酰乙醇胺（PE）。我们还表明，Atg 12-Atg 5缀合物与Atg 3和含PE的脂质体相互作用。这些结果表明，Atg 12-Atg 5缀合物是用于Atg 8-PE缀合反应的泛素-蛋白质连接酶（E3）样酶，显著促进蛋白质-脂质缀合。
Autophagy is a bulk degradation process in eukaryotic cells; autophagosomes enclose cytoplasmic components for degradation in the lysosome/vacuole. Autophagosome formation requires two ubiquitin-like conjugation systems, the Atg12 and Atg8 systems, which are tightly associated with expansion of autophagosomal membrane. Previous studies have suggested that there is a hierarchy between these systems; the Atg12 system is located upstream of the Atg8 system in the context of Atg protein organization. However, the concrete molecular relationship is unclear. Here, we show using an in vitro Atg8 conjugation system that the Atg12-Atg5 conjugate, but not unconjugated Atg12 or Atg5, strongly enhances the formation of the other conjugate, Atg8-PE. The Atg12-Atg5 conjugate promotes the transfer of Atg8 from Atg3 to the substrate, phosphatidylethanolamine ( PE), by stimulating the activity of Atg3. We also show that the Atg12-Atg5 conjugate interacts with both Atg3 and PE-containing liposomes. These results indicate that the Atg12-Atg5 conjugate is a ubiquitin-protein ligase (E3)-like enzyme for Atg8-PE conjugation reaction, distinctively promoting protein-lipid conjugation.