College of Life Sciences, Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture and Rural Affairs, Nanjing Agricultural University, Nanjing, China.
Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL.
J Cell Biol. 2019 Jun 3;218(6):1908-1927. doi: 10.1083/jcb.201811173. Epub 2019 Apr 22.
In the conserved autophagy pathway, autophagosomes (APs) engulf cellular components and deliver them to the lysosome for degradation. Before fusing with the lysosome, APs have to close via an unknown mechanism. We have previously shown that the endocytic Rab5-GTPase regulates AP closure. Therefore, we asked whether ESCRT, which catalyzes scission of vesicles into late endosomes, mediates the topologically similar process of AP sealing. Here, we show that depletion of representative subunits from all ESCRT complexes causes late autophagy defects and accumulation of APs. Focusing on two subunits, we show that Snf7 and the Vps4 ATPase localize to APs and their depletion results in accumulation of open APs. Moreover, Snf7 and Vps4 proteins complement their corresponding mutant defects in vivo and in vitro. Finally, a Rab5-controlled Atg17-Snf7 interaction is important for Snf7 localization to APs. Thus, we unravel a mechanism in which a Rab5-dependent Atg17-Snf7 interaction leads to recruitment of ESCRT to open APs where ESCRT catalyzes AP closure.
在保守的自噬途径中，自噬体 (AP) 吞噬细胞成分，并将它们递送至溶酶体进行降解。在与溶酶体融合之前，AP 必须通过未知机制关闭。我们之前已经表明，内吞 Rab5-GTPase 调节 AP 的关闭。因此，我们询问是否 ESCRT（催化晚期内体中囊泡分裂的酶）介导 AP 封闭的拓扑相似过程。在这里，我们表明所有 ESCRT 复合物的代表性亚基的耗竭会导致晚期自噬缺陷和 AP 的积累。我们专注于两个亚基，表明 Snf7 和 Vps4 ATPase 定位于 AP，其耗竭会导致开放 AP 的积累。此外，Snf7 和 Vps4 蛋白在体内和体外补充其相应的突变缺陷。最后，Rab5 控制的 Atg17-Snf7 相互作用对于 Snf7 定位于 AP 很重要。因此，我们揭示了一种机制，其中 Rab5 依赖性 Atg17-Snf7 相互作用导致 ESCRT 募集到开放的 AP，ESCRT 在那里催化 AP 的关闭。
