title: Role of the hydrophobic and charged residues in the 218-226 region of apoA-I in the biogenesis of HDL.
abstract: We investigated the significance of hydrophobic and charged residues 218-226 on the structure and functions of apoA-I and their contribution to the biogenesis of HDL. Adenovirus-mediated gene transfer of apoA-I[L218A/L219A/V221A/L222A] in apoA-I⁻/⁻ mice decreased plasma cholesterol and apoA-I levels to 15% of wild-type (WT) control mice and generated pre-β- and α4-HDL particles. In apoA-I⁻/⁻ × apoE⁻/⁻ mice, the same mutant formed few discoidal and pre-β-HDL particles that could not be converted to mature α-HDL particles by excess LCAT. Expression of the apoA-I[E223A/K226A] mutant in apoA-I⁻/⁻ mice caused lesser but discrete alterations in the HDL phenotype. The apoA-I[218-222] and apoA-I[E223A/K226A] mutants had 20% and normal capacity, respectively, to promote ABCA1-mediated cholesterol efflux. Both mutants had ∼65% of normal capacity to activate LCAT in vitro. Biophysical analyses suggested that both mutants affected in a distinct manner the structural integrity and plasticity of apoA-I that is necessary for normal functions. We conclude that the alteration of the hydrophobic 218-222 residues of apoA-I disrupts apoA-I/ABCA1 interactions and promotes the generation of defective pre-β particles that fail to mature into α-HDL subpopulations, thus resulting in low plasma apoA-I and HDL. Alterations of the charged 223, 226 residues caused milder but discrete changes in HDL phenotype.
authors.affiliation: Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Fotakis
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Kateifides
authors.forename: Christina
authors.initials: C
authors.lastname: Gkolfinopoulou
authors.forename: Dimitra
authors.initials: D
authors.lastname: Georgiadou
authors.forename: Melissa
authors.initials: M
authors.lastname: Beck
authors.forename: Katharina
authors.initials: K
authors.lastname: Gründler
authors.forename: Angeliki
authors.initials: A
authors.lastname: Chroni
authors.forename: Efstratios
authors.initials: E
authors.lastname: Stratikos
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.forename: Vassilis I
authors.initials: VI
authors.lastname: Zannis
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D016632:Apolipoprotein A-I / Q000097:blood / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008075:Lipoproteins, HDL / Q000096:biosynthesis* / Q000097:blood; D051379:Mice; D009154:Mutation; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D013696:Temperature; D019076:Transgenes / Q000235:genetics
chemical_list: D016632:Apolipoprotein A-I; D008075:Lipoproteins, HDL
keywords: LCAT; apolipoprotein A-I mutations; dyslipidemia; pre-β and α-HDL particles