Autophagy is a cellular process that degrades cytoplasmic cargo by engulfing it in a double membrane vesicle, known as the autophagosome, and delivering it to the lysosome. The ATG12-5-16L1 complex is responsible for conjugating members of the ubiquitin-like ATG8 protein family to phosphatidylethanolamine in the growing autophagosomal membrane, known as the phagophore. ATG12-5-16L1 is recruited to the phagophore by a subset of the phosphatidylinositol 3-phosphate-binding seven bladed â-propeller WIPI proteins. We determined the crystal structure of WIPI2d in complex with the WIPI2 interacting region (W2IR) of ATG16L1 comprising residues 207-230 at 1.85 Å resolution. The structure shows that the ATG16L1 W2IR adopts an alpha helical conformation and binds in an electropositive and hydrophobic groove between WIPI2 â-propeller blades 2 and 3. Mutation of residues at the interface reduces or blocks the recruitment of ATG12-5-16L1 and the conjugation of the ATG8 protein LC3B to synthetic membranes. Interface mutants show a decrease in starvation-induced autophagy. Comparisons across the four human WIPIs suggest that WIPI1 and 2 belong to a W2IR-binding subclass responsible for localizing ATG12-5-16L1 and driving ATG8 lipidation, whilst WIPI3 and 4 belong to a second W34IR-binding subclass responsible for localizing ATG2, and so directing lipid supply to the nascent phagophore. The structure provides a framework for understanding the regulatory node connecting two central events in autophagy initiation, the action of the autophagic PI 3-kinase complex on the one hand, and ATG8 lipidation on the other.

中文翻译：

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WIPI2在自噬中膜募集ATG16L1的结构基础

自噬是一种细胞过程，它通过将细胞质货物吞噬在称为自噬体的双膜囊泡中并将其递送至溶酶体来降解细胞质货物。ATG12-5-16L1 复合物负责将泛素样 ATG8 蛋白家族的成员与生长的自噬体膜（称为吞噬细胞）中的磷脂酰乙醇胺结合。ATG12-5-16L1 被磷脂酰肌醇 3-磷酸结合七刀片 α-螺旋桨 WIPI 蛋白的一个子集募集到吞噬细胞中。我们确定了与 ATG16L1 的 WIPI2 相互作用区域 (W2IR) 复合的 WIPI2d 的晶体结构，该区域包含 1.85 Å 分辨率的残基 207-230。结构表明，ATG16L1 W2IR 采用 α 螺旋构象，结合在 WIPI2 α-螺旋桨叶片 2 和 3 之间的正电疏水槽中。界面处残基的突变减少或阻止了 ATG12-5-16L1 的募集和 ATG8 蛋白 LC3B 与合成膜的结合。界面突变体显示饥饿诱导的自噬减少。四个人类 WIPI 的比较表明，WIPI1 和 2 属于 W2IR 结合亚类，负责定位 ATG12-5-16L1 并驱动 ATG8 脂化，而 WIPI3 和 4 属于第二个 W34IR 结合亚类，负责定位 ATG2，因此指导新生吞噬细胞的脂质供应。该结构为理解连接自噬启动中的两个中心事件的调节节点提供了一个框架，一方面是自噬 PI 3-激酶复合物的作用，另一方面是 ATG8 脂化。