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

3.5 Discussion.
107
We have demonstrated that expression of SR-BI in a CHO cell background
permits the examination of HCV glycoprotein-SR-BI interactions in isolation
from other receptors such as human CD81. This is consistent with reported
findings (274). Using a panel of anti-E2 mAbs specific for non-overlapping,
consecutive epitopes we were able to determine epitope availability on
glycoprotein bound to SR-BI. mAb 9/75 recognised sE2 bound to SR-BI with
the highest signal, however mAbs 3/11, 11/20 and 6/1a also detected
glycoprotein (Figure 3-3). Interestingly, the epitopes recognised by three of
these antibodies (9/75, 3/11 and 11/20) are critical for E2-CD81 interactions
(81, 99, 237), suggesting that interaction of E2 with SR-BI may not preclude
CD81 engagement.
SR-BI mediated lipoprotein metabolism has been implicated in HCV
attachment and entry (25, 210, 324, 326). We therefore investigated the
binding of sE2 to a panel of SR-BI mutants, some of which are unable to
mediate cholesterol exchange with HDL. sE2 binding to these mutants was
proportional to their cell surface expression, indicating that SR-BI-E2
interactions were unaltered (Figure 3-6 and 3-7) mAbs 3D5 and C11 have
previously been shown to inhibit HCVcc infection and SR-BI mediated
cholesterol exchange with HDL (60). We attempted to map amino acid
residues that are important for mAb binding by monitoring their binding to the
panel of SR-BI mutants. Again, binding was proportional to surface
expression, suggesting that the mutations did not modulate antibody binding
(Figure 3-7 & Table 3-2).