Hepatitis C virus nonstructural protein 3-4A protease (NS3-4A) (NS3-4A)

The Hepatitis C virus (HCV) nonstructural protein 3-4A (NS3-4A) protease is a vital enzyme complex required for the viral life cycle [patsnap.com, nih.gov]. It consists of the NS3 protein, which possesses both serine protease and RNA helicase/NTPase activities, and the NS4A cofactor, which stabilizes the protease domain and anchors it to the intracellular membrane [nih.gov, mdpi.com]. The primary function of the NS3-4A protease is to cleave the viral polyprotein at four specific junctions to release mature nonstructural proteins (NS4A, NS4B, NS5A, and NS5B) necessary for RNA replication [mdpi.com, nih.gov]. Beyond its role in replication, the protease also cleaves host cell signaling proteins, such as MAVS and TRIF, to suppress the host's innate immune response and promote viral persistence [nih.gov, asm.org]. Due to its essentiality, the NS3-4A protease is a major target for direct-acting antiviral (DAA) drugs, which have significantly improved cure rates for chronic hepatitis C [patsnap.com, nih.gov]. However, the high mutation rate of HCV can lead to the development of resistance-associated substitutions (RAS) that reduce the efficacy of certain protease inhibitors [plos.org, nih.gov].

Other names

NS3/4A serine proteaseNS3 proteaseHCV NS3-4A complexNS3-4A serine proteinaseNonstructural protein 3-4A

NS3-4A protease inhibitors are direct-acting antivirals (DAAs) that bind to the active site of the serine protease domain, preventing the cleavage of the viral polyprotein into mature nonstructural proteins essential for viral replication [patsnap.com, nih.gov]. This inhibition halts the assembly of the viral replication complex and can also restore host innate immune signaling by preventing the cleavage of host adaptor proteins like MAVS and TRIF [asm.org, mdpi.com].