CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Virol Sin. 2018 Oct;33(5):440-448. doi: 10.1007/s12250-018-0058-6. Epub 2018 Oct 16.
Cyclophilin A (CypA) is a peptidyl-prolyl cis/trans isomerase that interacts with the matrix protein (M1) of influenza A virus (IAV) and restricts virus replication by regulating the ubiquitin-proteasome-mediated degradation of M1. However, the mechanism by which CypA regulates M1 ubiquitination remains unknown. In this study, we reported that E3 ubiquitin ligase AIP4 promoted K48-linked ubiquitination of M1 at K102 and K104, and accelerated ubiquitin-proteasome-mediated degradation of M1. The recombinant IAV with mutant M1 (K102R/K104R) could not be rescued, suggesting that the ubiquitination of M1 at K102/K104 was essential for IAV replication. Furthermore, CypA inhibited AIP4-mediated M1 ubiquitination by impairing the interaction between AIP4 and M1. More importantly, both the mutations of M1 (K102R/K104R) and CypA inhibited the nuclear export of M1, indicating that CypA regulates the cellular localization of M1 via inhibition of AIP4-mediated M1 ubiquitination at K102 and K104, which results in the reduced replication of IAV. Collectively, our findings reveal a novel ubiquitination-based mechanism by which CypA regulates the replication of IAV.
亲环蛋白 A（CypA）是一种肽基脯氨酰顺/反异构酶，它与甲型流感病毒（IAV）的基质蛋白（M1）相互作用，通过调节 M1 的泛素-蛋白酶体介导的降解来限制病毒复制。然而，CypA 调节 M1 泛素化的机制尚不清楚。在这项研究中，我们报告了 E3 泛素连接酶 AIP4 促进了 M1 在 K102 和 K104 处的 K48 连接泛素化，并加速了 M1 的泛素-蛋白酶体介导的降解。具有突变 M1（K102R/K104R）的重组 IAV 无法被拯救，这表明 M1 在 K102/K104 处的泛素化对于 IAV 复制是必不可少的。此外，CypA 通过损害 AIP4 与 M1 之间的相互作用，抑制了 AIP4 介导的 M1 泛素化。更重要的是，M1 的突变（K102R/K104R）和 CypA 都抑制了 M1 的核输出，这表明 CypA 通过抑制 AIP4 介导的 M1 在 K102 和 K104 处的泛素化来调节 M1 的细胞定位，从而导致 IAV 复制减少。总之，我们的研究结果揭示了 CypA 调节 IAV 复制的一种新的基于泛素化的机制。
