Nguyen Thanh Ngoc, Padman Benjamin Scott, Usher Joanne, Oorschot Viola, Ramm Georg, Lazarou Michael
Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800, Australia.
Monash Ramaciotti Centre for Cryo Electron Microscopy, Monash University, Melbourne, Victoria 3800, Australia.
J Cell Biol. 2016 Dec 19;215(6):857-874. doi: 10.1083/jcb.201607039. Epub 2016 Nov 18.
Members of the Atg8 family of proteins are conjugated to autophagosomal membranes, where they have been proposed to drive autophagosome formation and selective sequestration of cargo. In mammals, the Atg8 family consists of six members divided into the LC3 and GABARAP subfamilies. To define Atg8 function, we used genome editing to generate knockouts of the LC3 and GABARAP subfamilies as well as all six Atg8 family members in HeLa cells. We show that Atg8s are dispensable for autophagosome formation and selective engulfment of mitochondria, but essential for autophagosome-lysosome fusion. We find that the GABARAP subfamily promotes PLEKHM1 recruitment and governs autophagosome-lysosome fusion, whereas the LC3 subfamily plays a less prominent role in these processes. Although neither GABARAPs nor LC3s are required for autophagosome biogenesis, loss of all Atg8s yields smaller autophagosomes and a slowed initial rate of autophagosome formation. Our results clarify the essential function of the Atg8 family and identify GABARAP subfamily members as primary contributors to PINK1/Parkin mitophagy and starvation autophagy.
Atg8蛋白家族的成员与自噬体膜结合，有人认为它们在自噬体形成和货物的选择性隔离过程中发挥作用。在哺乳动物中，Atg8家族由六个成员组成，分为LC3和GABARAP亚家族。为了确定Atg8的功能，我们利用基因组编辑技术在HeLa细胞中敲除了LC3和GABARAP亚家族以及所有六个Atg8家族成员。我们发现，Atg8对于自噬体的形成和线粒体的选择性吞噬并非必需，但对自噬体-溶酶体融合至关重要。我们发现，GABARAP亚家族促进PLEKHM1的募集并控制自噬体-溶酶体融合，而LC3亚家族在这些过程中发挥的作用较小。尽管自噬体生物发生既不需要GABARAP也不需要LC3，但所有Atg8的缺失会产生较小的自噬体，并减缓自噬体形成的初始速率。我们的结果阐明了Atg8家族的基本功能，并确定GABARAP亚家族成员是PINK1/帕金介导的线粒体自噬和饥饿自噬的主要贡献者。
