National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, P.R. China.
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P.R. China.
Dev Cell. 2021 Feb 22;56(4):427-442.e5. doi: 10.1016/j.devcel.2020.12.010. Epub 2020 Dec 16.
Autophagy acts as a cellular surveillance mechanism to combat invading pathogens. Viruses have evolved various strategies to block autophagy and even subvert it for their replication and release. Here, we demonstrated that ORF3a of the COVID-19 virus SARS-CoV-2 inhibits autophagy activity by blocking fusion of autophagosomes/amphisomes with lysosomes. The late endosome-localized ORF3a directly interacts with and sequestrates the homotypic fusion and protein sorting (HOPS) component VPS39, thereby preventing HOPS complex from interacting with the autophagosomal SNARE protein STX17. This blocks assembly of the STX17-SNAP29-VAMP8 SNARE complex, which mediates autophagosome/amphisome fusion with lysosomes. Expression of ORF3a also damages lysosomes and impairs their function. SARS-CoV-2 virus infection blocks autophagy, resulting in accumulation of autophagosomes/amphisomes, and causes late endosomal sequestration of VPS39. Surprisingly, ORF3a from the SARS virus SARS-CoV fails to interact with HOPS or block autophagy. Our study reveals a mechanism by which SARS-CoV-2 evades lysosomal destruction and provides insights for developing new strategies to treat COVID-19.
自噬作为一种细胞监视机制，可抵御入侵的病原体。病毒已经进化出各种策略来阻断自噬，甚至将其颠覆以实现自身的复制和释放。在这里，我们证明了 COVID-19 病毒 SARS-CoV-2 的 ORF3a 通过阻断自噬体/内体与溶酶体的融合来抑制自噬活性。定位于晚期内体的 ORF3a 直接与同源融合和蛋白分选（HOPS）成分 VPS39 相互作用并将其隔离，从而阻止 HOPS 复合物与自噬体 SNARE 蛋白 STX17 相互作用。这阻止了 STX17-SNAP29-VAMP8 SNARE 复合物的组装，该复合物介导自噬体/内体与溶酶体融合。ORF3a 的表达也会损伤溶酶体并损害其功能。SARS-CoV-2 病毒感染会阻断自噬，导致自噬体/内体的积累，并导致晚期内体中 VPS39 的隔离。令人惊讶的是，SARS 病毒 SARS-CoV 的 ORF3a 无法与 HOPS 相互作用或阻断自噬。我们的研究揭示了 SARS-CoV-2 逃避溶酶体破坏的机制，并为开发治疗 COVID-19 的新策略提供了思路。
