Abstract: Mitochondrial antiviral signaling protein (MAVS) is an important adaptor protein in the host innate immunity pathway in response to RNA viruses, playing important regulatory roles in innate immune and inflammatory responses. The expression and the function of MAVS are regulated by two mechanisms, namely transcription and post-translational modification, and phosphorylation and ubiquitination play important roles in regulating the transport, function and stability of MAVS. In order to further investigate the effect of MAVS phosphorylation on the levels of IFN-β and TNF-α production in cells, seven previously unreported MAVS phosphorylation sites, including pS193, pS226, pS238, pS246, pS249, pT252, and pT370, were identified by tandem mass spectrometry. Subsequently, the above phosphorylation sites were mutated into alanine (A) to construct a phosphorylation-deficient mutant. It was found that MAVS T370A mutation could significantly inhibit the transcriptional activity of IFN-β and NF-κB reporter genes downstream of the MAVS signaling pathway, and then down-regulate the expression of IFN-β and TNF-α, and inhibit the antiviral response of cells. These results suggested that T370, as an unreported phosphorylation site of MAVS, played an important role in the host innate immune signaling pathway. Further elucidation of kinases mediating phosphorylation at T370 will be of great significance for revealing the molecular mechanism of innate immune homeostasis maintenance and host antiviral activity.

Key words: MAVS, innate immunity, inflammatory response, IFN-β, NF-κB, phosphorylation