TY - JOUR T1 - Hydrophobic Amino Acids in the Hinge Region of the 5A Apolipoprotein Mimetic Peptide are Essential for Promoting Cholesterol Efflux by the ABCA1 Transporter JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther DO - 10.1124/jpet.112.198143 SP - jpet.112.198143 AU - Denis O Sviridov AU - Alexander M Andrianov AU - Ivan V Anishchenko AU - John A Stonik AU - Marcelo J. A. Amar AU - Scott Turner AU - Alan T Remaley Y1 - 2012/01/01 UR - http://jpet.aspetjournals.org/content/early/2012/10/05/jpet.112.198143.abstract N2 - 5A is a bi-helical apolipoprotein mimetic peptide that effluxes cholesterol from cells and reduces inflammation and atherosclerosis in animal models. We investigated how hydrophobic residues in the hinge region between the two helices are important in the structure and function of this peptide. By Simulated Annealing Analysis and Molecular Dynamics modeling, two hydrophobic amino acids, F-18 and W-21, in the hinge region, were predicted to be relatively surface exposed and to interact with the aqueous solvent. Using a series of 5A peptide analogues in which F-18 or W-21 were changed to either F, W, A or E, only peptides with hydrophobic amino acids in these two positions were able to readily bind and solubilize phospholipid vesicles. Compared to active peptides containing F or W, peptides containing E in either of these 2 positions were more than 10-fold less effective in effluxing cholesterol by the ABCA1 transporter. Intravenous injection of 5A in C57BL/6 mice increased plasma free cholesterol (5A: 89.9±13.6 mg/dL; control: 38.7±4.3 mg/dL, mean ± SD, P<0.05) and triglycerides (5A: 887.0±172.0 mg/dL; control: 108.9±9.9 mg/dL, P<0.05), whereas the EE peptide containing E in both positions had no effect. Finally, 5A increased approximately 2.5-fold cholesterol efflux in vivo from radiolabeled macrophages, whereas the EE peptide was inactive. These results provide a rationale for future design of therapeutic apolipoprotein mimetic peptides and also provide new insights into the interaction of hydrophobic residues on apolipoproteins with phospholipids in the lipid microdomain created by the ABCA1 transporter, during the cholesterol efflux process. ER -