National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PRC.
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PRC; Department of Immunology, Peking University School of Basic Medical Science, Beijing 100191, PRC.
Mol Cell. 2016 Sep 1;63(5):781-95. doi: 10.1016/j.molcel.2016.08.021.
Mutations in the human autophagy gene EPG5 cause the multisystem disorder Vici syndrome. Here we demonstrated that EPG5 is a Rab7 effector that determines the fusion specificity of autophagosomes with late endosomes/lysosomes. EPG5 is recruited to late endosomes/lysosomes by direct interaction with Rab7 and the late endosomal/lysosomal R-SNARE VAMP7/8. EPG5 also binds to LC3/LGG-1 (mammalian and C. elegans Atg8 homolog, respectively) and to assembled STX17-SNAP29 Qabc SNARE complexes on autophagosomes. EPG5 stabilizes and facilitates the assembly of STX17-SNAP29-VAMP7/8 trans-SNARE complexes, and promotes STX17-SNAP29-VAMP7-mediated fusion of reconstituted proteoliposomes. Loss of EPG5 activity causes abnormal fusion of autophagosomes with various endocytic vesicles, in part due to elevated assembly of STX17-SNAP25-VAMP8 complexes. SNAP25 knockdown partially suppresses the autophagy defect caused by EPG5 depletion. Our study reveals that EPG5 is a Rab7 effector involved in autophagosome maturation, providing insight into the molecular mechanism underlying Vici syndrome.
人类自噬基因 EPG5 的突变导致多系统疾病 Vici 综合征。在这里，我们证明 EPG5 是 Rab7 的效应物，决定了自噬体与晚期内体/溶酶体融合的特异性。EPG5 通过与 Rab7 和晚期内体/溶酶体 R-SNARE VAMP7/8 的直接相互作用被招募到晚期内体/溶酶体。EPG5 还与 LC3/LGG-1（哺乳动物和 C. elegans Atg8 同源物）结合，并与自噬体上组装的 STX17-SNAP29 Qabc SNARE 复合物结合。EPG5 稳定并促进 STX17-SNAP29-VAMP7/8 跨 SNARE 复合物的组装，并促进 STX17-SNAP29-VAMP7 介导的重建蛋白脂质体的融合。EPG5 活性丧失导致自噬体与各种内吞囊泡的异常融合，部分原因是 STX17-SNAP25-VAMP8 复合物的组装增加。SNAP25 敲低部分抑制了 EPG5 耗竭引起的自噬缺陷。我们的研究揭示了 EPG5 是一种参与自噬体成熟的 Rab7 效应物，为 Vici 综合征的分子机制提供了新的见解。
