Effects of increasing hydrophobicity on the physical-chemical and biological properties of a class A amphipathic helical peptide

Geeta Datta,Manjula Chaddha,Susan Hama,Mohamad Navab,Alan M Fogelman,David W Garber,Vinod K Mishra,Richard M Epand,Raquel F Epand,Sissel Lund-Katz,Michael C Phillips,Jere P Segrest,G.M Anantharamaiah

doi:10.1016/s0022-2275(20)31599-6

Abstract

We have recently shown that a class A amphipathic peptide 5F with increased amphipathicity protected mice from diet-induced atherosclerosis (Garber et al. J. Lipid Res. 2001. 42: 545–552). We have now examined the effects of increasing the hydrophobicity of a series of homologous class A amphipathic peptides, including 5F, on physical and functional properties related to atherosclerosis inhibition by systematically replacing existing nonpolar amino acids with phenylalanine. The peptides, based on the sequence Ac-D-W-L-K-A-F-Y-D-K-V-A-E-K-L-K-E-A-F-NH2 (Ac-18A-NH2 or 2F) were: 3F3(Ac-F318A-NH2), 3F14(Ac-F1418A-NH2), 4F(Ac-F3,1418A-NH2), 5F(Ac-F11,14,17 18A-NH2), 6F(Ac-F10,11,14,17 18A-NH2), and 7F(Ac-F3,10,11,14,17 18A-NH2). Measurements of aqueous solubility, HPLC retention time, exclusion pressure for penetration into an egg phosphatidylcholine (EPC) monolayer, and rates of EPC solubilization revealed an abrupt increase in the hydrophobicity between peptides 4F and 5F; this was accompanied by increased ability to associate with phospholipids. The peptides 6F and 7F were less effective, indicating a limit to increased hydrophobicity for promoting lipid interaction in these peptides. Despite this marked increase in lipid affinity, these peptides were less effective than apoA-I in activating the plasma enzyme, lecithin:cholesterol acyltransferase, with 5F activating LCAT the best (80% of apoA-I). Peptides 4F, 5F, and 6F were equally potent in inhibiting LDL-induced monocyte chemotactic activity.These studies suggest that an appropriate balance between peptide-peptide and peptide-lipid interactions is required for optimal biological activity of amphipathic peptides. These studies provide a rationale for the design of small apoA-I-mimetics with increased potency for atherosclerosis inhibition.—Datta, G., M. Chaddha, S. Hama, M. Navab, A. M. Fogelman, D. W. Garber, V. K. Mishra, R. M. Epand, R. F. Epand, S. Lund-Katz, M. C. Phillips, J. P. Segrest, and G. M. Anantharamaiah. Effects of increasing hydrophobicity on the physical-chemical and biological properties of a class A amphipathic helical peptide. J. Lipid Res. 2001. 42: 1096–1104.

Highlights

We have recently shown that a class A amphipathic peptide 5F with increased amphipathicity protected mice from diet-induced atherosclerosis
The calculated hydrophobicity per residue [according to modified GES scale [44]] on the nonpolar face increased as the number of Phe residues increased
A gradual increase in ⌳ was again observed after 5F in the values for 6F and 7F (Table 1). This is due to the substitution of Leu at positions 3 and 14 in Ac-18A-NH2 with Phe, which results in a slight increase in the hydrophobicity of the nonpolar face and a slight increase in ⌳ values for the two 3F analogs and 4F

Summary

Introduction

We have recently shown that a class A amphipathic peptide 5F with increased amphipathicity protected mice from diet-induced atherosclerosis Our earlier studies [7, 24] have shown that an increase in the hydrophobicity of this peptide increases its lipid affinity and apoA-I-mimicking properties.

Results

Conclusion