Hepatitis C virus non-structural protein 4 (NS4) (NS4)

Hepatitis C virus non-structural protein 4 (NS4) is a critical component of the HCV replication machinery, synthesized as part of a large polyprotein that is subsequently cleaved into two functional subunits: NS4A and NS4B (UniProt P26664). NS4A is a small 54-amino acid protein that serves as an essential cofactor for the NS3 serine protease; it stabilizes NS3 and anchors the complex to the endoplasmic reticulum membrane, which is necessary for the processing of the viral polyprotein (Moradpour et al., 2007, Nature Reviews Microbiology). NS4B is a 27-kDa integral membrane protein responsible for inducing the "membranous web," a specialized cellular environment that protects the viral RNA and concentrates the replication machinery (Gouttenoire et al., 2010, Journal of General Virology). Therapeutically, NS4 is primarily targeted through the inhibition of the NS3/4A protease complex by direct-acting antivirals (DAAs) such as glecaprevir and grazoprevir, which prevent viral maturation (FDA Mavyret Label). Experimental strategies also target NS4B to disrupt the formation of the replication complex, offering a potential pathway to overcome resistance to existing therapies (Einav et al., 2008, Nature Medicine). The successful targeting of the NS4-associated protease complex has revolutionized the treatment of chronic hepatitis C, leading to cure rates exceeding 95% across most genotypes (AASLD/IDSA Guidelines).

Other names

HCV NS4Non-structural protein 4A (NS4A)Non-structural protein 4B (NS4B)p8p27

Inhibition of the NS3/4A serine protease complex by blocking the NS4A cofactor-dependent proteolytic activity, or inhibition of NS4B-mediated membranous web formation to prevent viral RNA replication.