Hepatitis C virus NS3-4A serine protease (NS3-4A)

The Hepatitis C virus NS3-4A serine protease is a membrane-associated, multifunctional viral enzyme composed of the N-terminal protease domain of NS3 and its essential cofactor, NS4A. The NS3-4A complex is crucial for the proteolytic processing of the HCV polyprotein at four specific junctions (NS3-NS4A, NS4A-NS4B, NS4B-NS5A, NS5A-NS5B), liberating nonstructural proteins required for viral RNA replication. The NS3 region also possesses an RNA helicase domain required for unwinding viral RNA. NS4A serves both as a membrane anchor and as a structural cofactor that activates and stabilizes the serine protease domain. These activities are essential for HCV replication and allow the virus to subvert innate host immune responses, for example by proteolytically degrading host factors such as TRIF involved in interferon signaling pathways. NS3-4A serine protease is a clinically validated drug target, and several direct-acting antiviral inhibitors targeting this enzyme have transformed HCV therapy. Resistance can arise through point mutations in the protease active site or inhibitor-binding regions.

Other names

NS3/4A proteaseHCV NS3-4A proteaseNS3-4A proteinaseHepatitis C virus nonstructural protein 3-4A protease

Direct inhibition of protease activity, leading to interruption of viral polyprotein processing and HCV replication; Prevention of cleavage of host immune factors (e.g., TRIF), restoring host immune responses