Non-structural protein 4A (Hepatitis C virus) (NS4A)

Non-structural protein 4A (NS4A) is a small, 54-amino acid transmembrane protein encoded by the Hepatitis C virus (HCV) that acts as an essential cofactor for the NS3 serine protease [2, 3]. The formation of the NS3/4A complex is critical for viral maturation, as it catalyzes the proteolytic cleavage of the HCV polyprotein at four specific sites to generate mature NS3, NS4A, NS4B, NS5A, and NS5B proteins [4, 12]. Beyond its structural and catalytic role, NS4A anchors the protease complex to the endoplasmic reticulum membrane and facilitates the cleavage of host cell adaptor proteins such as MAVS (IPS-1) and TRIF, effectively dismantling the host's innate antiviral interferon response [5, 6]. Because of its absolute requirement for viral replication and immune evasion, the NS3/4A complex is a primary target for direct-acting antivirals (DAAs) [7, 10]. Modern NS3/4A protease inhibitors, such as glecaprevir and voxilaprevir, occupy the substrate-binding groove formed by the complex, leading to high cure rates in chronic hepatitis C patients, though the development of resistance-associated substitutions remains a clinical challenge [4, 8].

Other names

HCV NS4ANS4A cofactorp54 proteinNon-structural protein 4A

Binding and inhibition of the NS3/4A serine protease complex, preventing the cleavage of the viral polyprotein into functional units and blocking the degradation of host innate immune signaling proteins.