Identification on Human CD36 of a Domain (155-183) Implicated in Binding Oxidized Low-Density Lipoproteins (Ox-LDL)

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Abstract
Uptake of oxidized LDL (oxLDL) by macrophages is one of the key events implicated in the initiation and perpetuation of atherosclerotic lesions. One of the major scavenging receptors, which binds modified LDL, on macrophages is CD36. The domain on CD36 implicated in the binding of oxLDL remains to be elucidated. In this study, COS cells transfected with human CD36 cDNA bound FITC-oxidized human LDL in a dose-dependent, saturable manner. This binding was inhibited by an excess of oxLDL but not by native LDL. Anti-CD36 monoclonal antibodies (mAbs) 10/5, FA6-152, and 8A6 (directed against domain 155-183), but not mAb 13/10 (directed against domain 30-76), completely inhibited oxLDL binding to human CD36-transfected COS cells. Cells transfected with a chimeric human CD36 construct (hmh 155-183), resulting from the swapping of human domain 155-183 with its murine counterpart, resulted in low binding of oxLDL. In contrast, cells transfected with a chimeric murine CD36 construct (mhm 155-183), resulting from the swapping of murine domain 155-183 with its human counterpart, resulted in high binding of oxidized human LDL. Binding of oxLDL to cells transfected by chimeric construct mhm 155-183 were only partially blocked by mAbs 10/5, FA6-152, and 8A6. In the present study we have identified, for the first time, an important functional domain (encompassing amino acids 155-183) on CD36 involved in the binding of oxLDL. In addition, the binding site for oxidized human LDL on murine CD36 seems to differ from its human counterpart.