Submitted to: Molecular Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2005
Publication Date: 2/16/2006
Citation: Stewart, B.W., Nagarajan, S. 2006. Recombinant CD36 inhibits oxLDD-induced ICAM-1-dependent monocyte adhesion. Molecular Immunology. 43(3):255-267.
Interpretive Summary: In atherosclerosis, bad cholesterol deposits on blood vessels. This causes circulating blood cells to stick to blood vessels. The attachment results in the formation of foam cells. The foam cell formation is controlled by a protein called CD36. In this study, we created a soluble CD36 protein. The soluble protein showed it blocked the sticking of blood cells to blood vessel cells. Future studies will be designed to create genetically modified edible vegetables or fruits to produce this protein.
Technical Abstract: A key event in atherosclerosis is the interaction between monocytes and endothelial cells. Binding of oxidized low-density lipoprotein (oxLDL) to CD36 on endothelial cells results in activation and subsequent monocyte adhesion. In this study, a recombinant soluble CD36 molecule was expressed to delineate its ability to block the adhesion of monocytes. To construct soluble CD36, the extra-cellular domain of CD36 was fused to the Fc domain of human IgG1. The N-terminal sequence of CD36 was replaced with N-terminal signal peptide sequence of CD59, a type I membrane protein. The resulting chimeric sCD36-Ig cDNA (sCD36-Ig) was transfected into COS-7 and CHOK1 cells and supernatants were analyzed for secretion of this molecule. Sandwich ELISA and oxLDL binding analyses showed that recombinant sCD36-Ig is secreted in a functionally active form. Western blot analysis of the purified sCD36-Ig using three different anti-CD36 monoclonal antibodies and anti-human IgG showed that the chimeric sCD36-Ig is a dimer of 220 kDa. Further, the sCD36-Ig inhibited the adhesion of monocytes to oxLDL. Interestingly, sCD36-Ig blocked the oxLDL-induced adhesion of monocytes to the endothelial cell specific protein, ICAM-1. Our results indicate that the chimeric sCD36-Ig protein is folded correctly and can effectively compete for the binding of oxLDL to membrane-expressed CD36. These results suggest that oxLDL-induced monocyte adhesion can be blocked using sCD36-Ig, and this may be useful in blocking the cell–cell interaction leading to atherogenesis.