Autophagy-related Protein 8 (Atg8) Family Interacting Motif in Atg3 Mediates the Atg3-Atg8 Interaction and Is Crucial for the Cytoplasm-to-Vacuole Targeting Pathway
Autophagy-related Protein 8 (Atg8) Family Interacting Motif in Atg3 Mediates the Atg3-Atg8 Interaction and Is Crucial for the Cytoplasm-to-Vacuole Targeting Pathway
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DOI：
10.1074/jbc.m110.113670
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发表时间：
2010-09-17
影响因子：
4.8
通讯作者：
Inagaki, Fuyuhiko
中科院分区：
文献类型：
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作者：
Yamaguchi, Masaya;Noda, Nobuo N.;Inagaki, Fuyuhiko
自噬相关蛋白8 （Atg8）偶联系统对于自噬过程中称为自噬体的双膜囊泡的形成至关重要，自噬是一个在大多数真核生物中保守的整体降解过程。在酵母中，通过受体蛋白Atg19在细胞质-液泡靶向（Cvt）途径中识别目标液泡酶也很重要，这是一种选择性自噬。Atg3是一种类似e2的酶，可将at8与磷脂酰乙醇胺结合。在这里，我们发现Atg3通过WEDL序列直接与Atg8相互作用，这与E2与泛素样修饰剂之间的典型相互作用不同。此外，核磁共振实验表明，Atg8与Atg3的相互作用模式与Atg8/LC3与自噬受体（如Atg19和p62）中保守的Atg8家族相互作用基序（AIM）的相互作用模式非常相似。因此，Atg3中的WEDL序列是一个典型的AIM。体外分析表明，Atg3 AIM对Atg8从类似Atg3硫酯的Atg8转移到磷脂酰乙醇胺起关键作用，但对中间体的形成不起作用。有趣的是，体内实验表明，它是Cvt途径所必需的，而不是饥饿诱导的自噬。Atg3 AIM在体外可减弱Atg19对Atg8脂化的抑制作用，提示Atg3 AIM可能在Cvt途径中对Atg19结合的Atg8脂化起重要作用。
The autophagy-related protein 8 (Atg8) conjugation system is essential for the formation of double-membrane vesicles called autophagosomes during autophagy, a bulk degradation process conserved among most eukaryotes. It is also important in yeast for recognizing target vacuolar enzymes through the receptor protein Atg19 during the cytoplasm-to-vacuole targeting (Cvt) pathway, a selective type of autophagy. Atg3 is an E2-like enzyme that conjugates Atg8 with phosphatidylethanolamine. Here, we show that Atg3 directly interacts with Atg8 through the WEDL sequence, which is distinct from canonical interaction between E2 and ubiquitin-like modifiers. Moreover, NMR experiments suggest that the mode of interaction between Atg8 and Atg3 is quite similar to that between Atg8/LC3 and the Atg8 family interacting motif (AIM) conserved in autophagic receptors, such as Atg19 and p62. Thus, the WEDL sequence in Atg3 is a canonical AIM. In vitro analyses showed that Atg3 AIM is crucial for the transfer of Atg8 from the Atg8 similar to Atg3 thioester intermediate to phosphatidylethanolamine but not for the formation of the intermediate. Intriguingly, in vivo experiments showed that it is necessary for the Cvt pathway but not for starvation-induced autophagy. Atg3 AIM attenuated the inhibitory effect of Atg19 on Atg8 lipidation in vitro, suggesting that Atg3 AIM may be important for the lipidation of Atg19-bound Atg8 during the Cvt pathway.