NLRC5 Restricts Dengue Virus Infection by Promoting the Autophagic Degradation of Viral NS3 through E3 Ligase CUL2 (cullin 2)

NLRC5 has been reported to be involved in antiviral immunity; however, the underlying mechanism remains poorly understood. Here, we investigated the functional role of NLRC5 in the infection of a flavivirus, dengue virus (DENV). We found that expression of NLRC5 was strongly induced by virus infection and IFNB or IFNG stimulation in different cell lines. Overexpression of NLRC5 remarkably suppressed DENV infection, whereas knockout of <i>NLRC5</i> led to a significant increase in DENV infection. Mechanistic study revealed that NLRC5 interacted with the viral nonstructural protein 3 (NS3) protease domain and mediated degradation of NS3 through a ubiquitin-dependent selective macroautophagy/autophagy pathway. We demonstrated that NLRC5 recruited the E3 ubiquitin ligase CUL2 (cullin 2) to catalyze K48-linked poly-ubiquitination of the NS3 protease domain, which subsequently served as a recognition signal for cargo receptor TOLLIP-mediated selective autophagic degradation. Together, we have demonstrated that NLRC5 exerted an antiviral effect by mediating the degradation of a multifunctional protein of DENV, providing a novel antiviral signal axis of NLRC5-CUL2-NS3-TOLLIP. This study expands our understanding of the regulatory network of NLRC5 in the host defense against virus infection.

已有研究报道NLRC5参与抗病毒免疫过程，但其潜在分子机制仍未得到充分阐明。本研究针对NLRC5在黄病毒属（flavivirus）登革病毒（DENV）感染中的功能作用展开探究。研究发现，在不同细胞系中，NLRC5的表达可被病毒感染以及干扰素β（IFNB）、干扰素γ（IFNG）刺激显著诱导。过表达NLRC5可显著抑制登革病毒感染，而敲除NLRC5则会导致登革病毒感染水平显著升高。机制研究显示，NLRC5可与病毒非结构蛋白3（NS3）蛋白酶结构域相互作用，并通过依赖泛素的选择性巨自噬/自噬通路介导NS3的降解。本研究证实，NLRC5可招募E3泛素连接酶CUL2（cullin 2），催化NS3蛋白酶结构域发生K48连接型多泛素化修饰，该修饰随后可作为识别信号，介导货物受体TOLLIP依赖的选择性自噬降解。综上，本研究证明NLRC5可通过介导登革病毒多功能蛋白的降解发挥抗病毒作用，揭示了一条全新的NLRC5-CUL2-NS3-TOLLIP抗病毒信号轴。本研究拓展了我们对NLRC5在宿主抗病毒感染防御中的调控网络的认知。