Lipid binding and lipid uptake of lipoprotein receptors participate in HCV entry.

Schematics were shown for the SR-B1, LDLR and VLDLR mutants (upper panels of A and B, and left panel of C). (A) S112F- and T175A-SR-B1 were generated to examine the significance of lipid binding ability. (B) Seven or eight repeats in the ligand binding domains of LDLR (left) and VLDLR (right) were deleted (ΔLBD). (C) An asparagine residue in the repeat 5 and in the repeats 2 to 7 of LDLR was substituted with tyrosine (mut5 and mut2-7). The wild-type and mutants of SR-B1, LDLR and VLDLR were expressed in SR/LD-DKO Huh7 cells by lentiviral vectors. Expressions of these receptors were detected by immunoblotting (middle panels in A and B, right upper panel in C). These cells were infected with HCVcc at an MOI of 1, and intracellular HCV RNA levels at 24 h post-infection were determined by qRT-PCR (lower panels in A and B, right lower panel in C). (D) HCVpp were inoculated into parental, SR/LD-DKO expressing either SR-B1, LDLR or VLDLR and CD81-KO Huh7 cells, and luciferase activities were determined at 48 h post-infection by using a luciferase assay system. In all cases, asterisks indicate significant differences (*P<0.05; **P<0.01) versus the results for cells expressing wild-type receptors.