Nuclear receptor 4 group A member 1 determines hepatitis C virus entry efficiency through the regulation of cellular receptor and apolipoprotein E expression.

Orphan nuclear receptor subfamily 4 group A member 1 (NR4A1) is a transcription factor stimulated by many factors and plays pivotal roles in metabolism, proliferation and apoptosis. In this study, the expression of NR4A1 in Huh7.5.1 cells was significantly upregulated by hepatitis C virus (HCV) infection. The silencing of NR4A1 inhibited the entry of HCV and reduced the specific infectivity of secreted HCV particles but had only minor or no effect on the genome replication and translation, virion assembly and virus release steps of the virus life cycle. Further experiments demonstrated that the silencing of NR4A1 affected virus entry through pan-downregulation of the expression of HCV receptors scavenger receptor BI, occludin, claudin-1 and epidermal growth factor receptor but not CD81. The reduced specific infectivity of HCV in the knockdown cells was due to decreased apolipoprotein E (ApoE) expression. These results explain the delayed spread of HCV in NR4A1 knockdown Huh7.5.1 cells. Thus, NR4A1 plays a role in HCV replication through regulating the expression of HCV receptors and ApoE, and facilitates HCV entry and spread.