title: Asymmetry in the lipid affinity of bihelical amphipathic peptides. A structural determinant for the specificity of ABCA1-dependent cholesterol efflux by peptides.
abstract: ApoA-I contains a tandem array of amphipathic helices with varying lipid affinity, which are critical in its ability to bind and remove lipids from cells by the ABCA1 transporter. In this study, the effect of asymmetry in the lipid affinity of amphipathic helices in a bihelical apoA-I mimetic peptide, 37pA, on lipid efflux by the ABCA1 transporter was examined. Seven peptide variants of 37pA were produced by substituting a varying number of hydrophobic amino acids for alanine on either one or both helices. The 5A peptide with five alanine substitutions in the second helix had decreased helical content compared with 37pA (5A, 12+/-1% helicity; 37pA, 28+/-2% helicity) and showed less self-association but, similar to the parent peptide, was able to readily solubilize phospholipid vesicles. Furthermore, 5A, unlike the parent peptide 37pA, was not hemolytic (37pA, 27+/-2% RBC lysis, 2 h, 18 microm). Finally, the 5A peptide stimulated cholesterol and phospholipid efflux by the ABCA1 transporter with higher specificity (ABCA1-transfected versus untransfected cells) than 37pA (5A, 9.7+/-0.77%, 18 h, 18 microm versus 1.5+/-0.27%, 18 h, 18 microm (p<0.0001); 37pA, 7.4+/-0.85%, 18 h, 18 microm versus 5.8+/-0.20%, 18 h, 18 microm (p=0.03)). In summary, we describe a novel bihelical peptide with asymmetry in the lipid affinity of its helices and properties similar to apoA-I in terms of specificity for cholesterol efflux by the ABCA1 transporter and low cytotoxicity.
authors.affiliation: Lipoprotein Metabolism Section, Pulmonary and Vascular Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1508, USA.
authors.forename: Amar A
authors.initials: AA
authors.lastname: Sethi
authors.forename: John A
authors.initials: JA
authors.lastname: Stonik
authors.forename: Fairwell
authors.initials: F
authors.lastname: Thomas
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Demosky
authors.forename: Marcelo
authors.initials: M
authors.lastname: Amar
authors.forename: Edward
authors.initials: E
authors.lastname: Neufeld
authors.forename: H Bryan
authors.initials: HB
authors.lastname: Brewer
authors.forename: W Sean
authors.initials: WS
authors.lastname: Davidson
authors.forename: Wilissa
authors.initials: W
authors.lastname: D'Souza
authors.forename: Dmitri
authors.initials: D
authors.lastname: Sviridov
authors.forename: Alan T
authors.initials: AT
authors.lastname: Remaley
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry*; D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D001692:Biological Transport; D002784:Cholesterol / Q000378:metabolism*; D002942:Circular Dichroism; D004912:Erythrocytes / Q000166:cytology; D019791:Guanidine / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D011487:Protein Conformation; D013997:Time Factors
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008055:Lipids; D010455:Peptides; D010743:Phospholipids; D002784:Cholesterol; D019791:Guanidine; D000409:Alanine