The acidic domain of GPIHBP1 and the heparin-binding domain of apoAV are
required for the binding of apoAV to GPIHBP1. CHO pgsA-745 cells were
transiently transfected with different GPIHBP1 constructs, and the expression
of GPIHBP1 was assessed by immunofluorescence microscopy with an antibody
against GPIHBP1 (green); binding of apoAV·DMPC disks to cells
was detected with an antibody against apoAV (red). Rows 1-3,
immunofluorescence microscopy showing that the binding of apoAV·DMPC
disks to cells expressing wild-type GPIHBP1 was eliminated by poly(D) (200
μg/ml). Row 4, immunofluorescence microscopy showing that
apoAV·DMPC disks do not bind to cells expressing D,E(38-48)A GPIHBP1.
Row 5, immunofluorescence microscopy examining the binding of mutant
apoAV·DMPC disks to cells expressing wild-type GPIHBP1. In the mutant
apoAV, four of the positively charged residues in the principal
heparin-binding domain were replaced with other amino acids (R210E, K211Q,
K215Q, K217E).