SAMSN1 restricts Japanese encephalitis virus replication by recruiting TRIM21 to degrade viral proteins and activate the interferon pathway

Abstract Japanese encephalitis virus (JEV), a zoonotic mosquito-transmitted flavivirus, induces human encephalitis and swine reproductive diseases. No antiviral drugs or treatments exist for flavivirus infections, which cause severe symptoms. Even though some host proteins can suppress flavivirus proliferation, the virus can inhibit this antiviral effect. This study identified a host protein SAMSN1 (SAM domain, SH3 domain, and nuclear localization signal 1; also referred to as HACS1, SLY2, and NASH1) having antiviral activity during JEV replication. SAMSN1 was upregulated during JEV infection. The expression of SAMSN1 inhibits JEV replication by binding and degrading JEV-encoded nonstructural proteins (NS1, NS5) through the proteasome and the SAMSN1-TRIM21-p62 autophagy protein degradation pathways. SAMSN1 induced expression of type I interferon through the RIG-I/MyD88-TBK1-IRF3 axis in the JEV infection process. Current findings reveal a novel role of SAMSN1 in inhibiting JEV replication and proliferation, through viral protein degradation and interferon pathway upregulation.