Cell surface expression of functional hepatitis C virus E1 and E2 glycoproteins.

Hepatitis C virus (HCV) glycoproteins E1 and E2 are believed to be retained in the endoplasmic reticulum (ER) or cis-Golgi compartment via retention signals located in their transmembrane domains. Here we describe the detection of E1 and E2 at the surface of transiently transfected HEK 293T and Huh7 cells. Surface-localized E1E2 heterodimers presented exclusively as non-covalently associated complexes. Surface-expressed E2 contained trans-Golgi modified complex/hybrid type carbohydrate and migrated diffusely between 70 and 90 kDa while intracellular E1 and E2 existed as high mannose 35 kDa and 70 kDa precursors, respectively. In addition, surface-localized E1E2 heterodimers were incorporated into E1E2-pseudotyped HIV-1 particles that were competent for entry into Huh7 cells. These studies suggest that functional HCV glycoproteins are not retained exclusively in the ER and transit through the secretory pathway.