Apolipoprotein B and E basic amino acid clusters influence low-density lipoprotein association with lipoprotein...

Lipoprotein accumulation in the subendothelial matrix is an important step in atherogenesis. We have previously shown that addition of lipoprotein lipase (LPL) markedly increased binding of apolipoprotein B (apoB)-containing lipoproteins to an endothelial cell-derived matrix, and this enhanced lipoprotein binding was inhibited by apoE. In the present studies we examined the role of various regions of apoB in the binding of LDL to LPL-containing endothelial cell matrix and the ability of various apoE domains to decrease lipoprotein retention. We studied three apoB epitope-specific monoclonal antibodies for their ability to block the binding of 125I-LDL to LPL-containing matrix. Of these, monoclonal antibody 4G3, which recognizes an arginine-containing epitope in apoB, was the most effective in reducing LDL binding. Chemical modification of LDL apoB lysines or arginines markedly reduced the ability of the lipoprotein to block the binding of 125I-LDL to LPL-containing matrix, suggesting that apoB positively charged amino acids are involved in the interaction. Furthermore, polyarginine or polylysine markedly decreased 125I-LDL binding to LPL-containing matrix, whereas polyleucine was ineffective. These data suggest that apoB positively charged regions are important in LDL binding. To explore the role of charge modifications on apoE by single arginine-cysteine interchanges, we examined the effects of the three major human apoE isoforms (apoE2, apoE3, and apoE4). ApoE3 was the most effective in decreasing 125I-LDL retention, followed by apoE4; apoE2 was the least effective. Similarly, apoE2-containing HDL was much less effective than apoE3-containing HDL in decreasing 125I-LDL retention.(ABSTRACT TRUNCATED AT 250 WORDS)