The role of scavenger receptor BI in hepatitis - eTheses Repository ...

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3.3 The interaction of sE2 with a panel of SR-BI mutants.
Lipoproteins are heavily implicated in HCV-SR-BI interactions; native HCV
has been proposed to interact with SR-BI via associated apoproteins (190)
and HDL enhances HCV infection in a process requiring selective cholesterol
uptake by SR-BI (25, 79, 324). We were therefore interested to investigate
whether mutations that perturb SR-BI interactions with lipoproteins affect
envelope protein binding. We used a panel of 6 SR-BI mutants expressed in
CHO cells, provided by our collaborator Thierry Huby at INSERM in Paris. Of
the 6 mutants, 2 are unable to mediate cholesterol transfer (121), 1 bears a
common human polymorphism linked to alterations in plasma lipid levels (1)
and 3 carry mutations in alpha-helical domains believed to be important for
SR-BI conformation (Figure 3-5 and Table 3-1).
We hypothesised that one or more of the mutations would modulate the
binding of HCV sE2 and that this may correlate with the mutant’s ability to
exchange cholesterol with HDL. To test this we performed SR-BI staining and
sE2 binding assays in parallel. A saturating concentration of sE2 was used to
ensure detection of any changes in glycoprotein binding to the mutants. We
observed variation in the cell surface expression of the mutants, in each case
sE2 binding was proportional to surface SR-BI levels, this suggests that the
mutations do not modulate sE2 interaction (Figure 3-6).
Anti-SR-BI mAbs 3D5 and C11 have been previously shown to inhibit HCVcc
infection, sE2 binding to CHO-SR-BI cells and SR-BI mediated cholesterol