Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA, USA.
Department of Pediatrics, Division of Pediatric Hematology and Oncology, Pennsylvania State University College of Medicine, Hershey, PA, USA.
Nat Commun. 2023 Sep 7;14(1):5503. doi: 10.1038/s41467-023-41243-4.
Autophagosome formation, a crucial step in macroautophagy (autophagy), requires the covalent conjugation of LC3 proteins to the amino headgroup of phosphatidylethanolamine (PE) lipids. Atg3, an E2-like enzyme, catalyzes the transfer of LC3 from LC3-Atg3 to PEs in targeted membranes. Here we show that the catalytically important C-terminal regions of human Atg3 (hAtg3) are conformationally dynamic and directly interact with the membrane, in collaboration with its N-terminal membrane curvature-sensitive helix. The functional relevance of these interactions was confirmed by in vitro conjugation and in vivo cellular assays. Therefore, highly curved phagophoric rims not only serve as a geometric cue for hAtg3 recruitment, but also their interaction with hAtg3 promotes LC3-PE conjugation by targeting its catalytic center to the membrane surface and bringing substrates into proximity. Our studies advance the notion that autophagosome biogenesis is directly guided by the spatial interactions of Atg3 with highly curved phagophoric rims.
自噬体的形成是巨自噬（自噬）的一个关键步骤，需要 LC3 蛋白与磷脂酰乙醇胺（PE）脂质的氨基头基发生共价连接。Atg3 是一种 E2 样酶，可催化 LC3-Atg3 从 LC3 转移到靶向膜中的 PEs。在这里，我们发现人 Atg3（hAtg3）的催化重要 C 端区域具有构象动态性，并与膜直接相互作用，与 N 端的膜曲率敏感螺旋协同作用。这些相互作用的功能相关性通过体外缀合和体内细胞测定得到了证实。因此，高度弯曲的吞噬前体边缘不仅作为 hAtg3 募集的几何线索，而且它们与 hAtg3 的相互作用通过将其催化中心靶向到膜表面并使底物接近来促进 LC3-PE 缀合。我们的研究推进了这样一种观点，即自噬体生物发生直接由 Atg3 与高度弯曲的吞噬前体边缘的空间相互作用指导。
