HCMV-pUS2 Disrupts cGAS-STING Signaling through LMAN2L Degradation.

Human cytomegalovirus (HCMV) has evolved diverse strategies for immune evasion. In this study, we identified HCMV-pUS2 as an indirect antagonist of the cGAS-STING pathway by promoting the degradation of lectin mannose-binding 2-like protein (LMAN2L), an unrecognized host factor involved in STING pathway. First, we discovered that HCMV, but not other DNA viruses such as HSV-1 and VACV, induces proteasomal degradation of LMAN2L during the immediate-early stage of infection. We then demonstrated that HCMV-pUS2 mediates LMAN2L degradation by recruiting the host E3 ubiquitin ligase RNF139 and E2 ubiquitin-conjugating enzyme UBE2G2, directing LMAN2L to the endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway. LMAN2L knockout diminishes HCMV-induced expression of type I interferons and interferon-stimulated genes. Furthermore, LMAN2L co-localizes and interacts with STING. Though it does not affect STING dimerization or TBK1 recruitment, it is essential for STING translocation from the ER to the Golgi. Our findings uncover LMAN2L as a novel host regulator of the STING pathway and identify pUS2-mediated ERAD as a previously unrecognized viral immune evasion strategy.