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Identification on human CD36 of a domain (155-183) implicated in binding oxidized low-density lipoproteins (Ox-LDL)
M D Puente Navazo1, L Daviet, E Ninio
1INSERM Unit 331, Faculté de Medicine René Laënnec, Lyon, France. puente@cimac-res.univ-lyonl.fr
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.
Insights
Researchers identified a key region on the CD36 scavenger receptor (amino acids 155-183) crucial for binding oxidized low-density lipoprotein (oxLDL). This finding advances understanding of atherosclerosis development and highlights differences between human and murine CD36 binding sites.
Area of Science:
- Cardiovascular Biology
- Molecular Cell Biology
- Immunology
Background:
- Macrophage uptake of oxidized low-density lipoprotein (oxLDL) is central to atherosclerotic lesion development.
- CD36 is a primary scavenger receptor mediating oxLDL binding on macrophages.
- The specific CD36 domain responsible for oxLDL interaction requires identification.
Purpose of the Study:
- To pinpoint the functional domain on CD36 involved in oxLDL binding.
- To compare oxLDL binding characteristics between human and murine CD36.
- To elucidate the molecular mechanisms underlying oxLDL-macrophage interactions in atherosclerosis.
Main Methods:
- Utilized COS cells transfected with human CD36 cDNA for binding assays.
- Employed FITC-labeled oxidized human LDL to quantify binding.
- Used anti-CD36 monoclonal antibodies and chimeric CD36 constructs (human/murine domain swaps) to map binding sites.
Main Results:
- Human CD36-transfected cells exhibited dose-dependent, saturable oxLDL binding, inhibited by excess oxLDL.
- Monoclonal antibodies targeting domain 155-183 of human CD36 completely blocked oxLDL binding.
- Chimeric constructs revealed that domain 155-183 is critical for human CD36 oxLDL binding, with differences noted in murine CD36.
Conclusions:
- Domain 155-183 of CD36 is essential for the binding of oxidized LDL.
- The binding site for oxLDL on murine CD36 appears distinct from that of human CD36.
- These findings provide critical insights into CD36-mediated oxLDL uptake and its role in atherosclerosis.