Studies on the interaction between apolipoprotein A-II-enriched HDL3 and cultured bovine aortic endothelial (BAE) cells.

The specific binding of high-density lipoproteins (HDL) to a number of cell and membrane types has been reported. The aim of this study was to investigate the ligand specificity of HDL binding sites on bovine aortic endothelial (BAE) cells and in particular to investigate the role of apo A-II in the interaction. In order to do this we prepared AII-HDL3 particles by incubating HDL3 with apo HDL. These particles were enriched in apo A-II, contained virtually no apo A-I, and were similar to HDL3 in terms of size and lipid composition. As these particles resemble the native HDL3 structure we believe they are probably a more suitable model for investigation of ligand specificity than artificial recombinants. AII-HDL3 particles were shown to bind to cells with similar affinity and capacity as HDL3. Further experiments indicated that HDL3 and AII-HDL3 competed with each other for binding and displayed similar affinities for a common binding site(s). The results suggest that apo A-II, as well as apo A-I, play an important role in the process of HDL recognition by putative HDL receptors on endothelial cells.