Abstract 14760: Apolipoprotein (apo) Mimetic Peptides ATI-5261 and CS-6253 Induce ABCA1/ABCG1 Mediated HDL Formation and Maturation in a Process Including ABCA1 Oligomerization and LCAT in Way Similar to apoA-I
Two novel (26-AA) apolipoprotein (apo) mimetic peptides ATI-5261 and CS-6253 were studied in vitro for their ability to interact with ABCA1 and ABCG1 and to generate functional HDL-like particles. Cross-linking experiments revealed that ATI-5261 and CS-6253 bind to ABCA1 and induce ABCA1 oligomerization. Binding studies using  I apoA-I showed that ATI-5261 and CS-6253 compete with radiolabeled apoA-I in ABCA1-expressing cells. The IC50 for ATI-5261 and CS-6253 were 0.36±0.17μM and 0.35±0.35μM respectively, representing a ~2 fold lower efficiency on a molar basis than apoA-I to interact with ABCA1 (IC50=0.17±0.17μM). Sucrose gradient ultracentrifugation analysis of plasma membrane (PM) obtained from BHK-ABCA1 cells incubated with peptides and apoA-I respectively for 6h and 12h at equimolar (0.93uM) concentrations showed that cholesterol and phospholipids was desorbed from specific non-raft and raft PM domains. Cholesterol desorption from PM by apoA-I was 26%±0.27, ATI-5261 29%±0.16 and by CS-6253 27%±0.09. ATI-5261 desorbs phospholipids (33.68%±0.80) slightly more than CS-6253 (25.5%±0.62) and less than apoA-I (40%±0.93). The efficiency of cholesterol efflux (Km) on an equimolar basis in BHK-ABCA1 cells was: apoA-I (0.13±0.27), ATI-5261 (0.21±0.25) and CS-6253 (0.18±0.25). Nascent HDL particles (100ug/ml) generated by BHK-ABCA1 cells were used as a substrate for LCAT activity. Measurement of endogenous LCAT fractional esterification rate was (9.32±0.09%/h) for apoA-I, (8.27±1.17%/h) for ATI-5261 and (8.24±0.14%/h) for CS-6253. Importantly, cholesterol efflux to lipidated HDL particles generated by incubating BHK-ABCA1 cells with lipid free ATI-5261 or CS-6253, were efficient acceptors for cholesterol released from BHK-ABCG1 cells in a dose-dependent manner. Moreover, BHK-ABCG1 cells facilitated the efflux of cholesterol from cells to lipidated HDL, but not to lipid free ATI-5261 or CS-6253. Based on these results, ATI-5261 and CS-6253 mimic apoA-I in its ability to bind ABCA1 and form nascent HDL particles that are substrates for LCAT and lead to the formation of cholesterol-enriched HDL via ABCG1.
- © 2013 by American Heart Association, Inc.