title: Naturally occurring and bioengineered apoA-I mutations that inhibit the conversion of discoidal to spherical HDL: the abnormal HDL phenotypes can be corrected by treatment with LCAT.
abstract: In the present study we have used adenovirus-mediated gene transfer of apoA-I (apolipoprotein A-I) mutants in apoA-I-/- mice to investigate how structural mutations in apoA-I affect the biogenesis and the plasma levels of HDL (high-density lipoprotein). The natural mutants apoA-I(R151C)Paris, apoA-I(R160L)Oslo and the bioengineered mutant apoA-I(R149A) were secreted efficiently from cells in culture. Their capacity to activate LCAT (lecithin:cholesterol acyltransferase) in vitro was greatly reduced, and their ability to promote ABCA1 (ATP-binding cassette transporter A1)-mediated cholesterol efflux was similar to that of WT (wild-type) apoA-I. Gene transfer of the three mutants in apoA-I-/- mice generated aberrant HDL phenotypes. The total plasma cholesterol of mice expressing the apoA-I(R160L)Oslo, apoA-I(R149A) and apoA-I(R151C)Paris mutants was reduced by 78, 59 and 61% and the apoA-I levels were reduced by 68, 64 and 55% respectively, as compared with mice expressing the WT apoA-I. The CE (cholesteryl ester)/TC (total cholesterol) ratio of HDL was decreased and the apoA-I was distributed in the HDL3 region. apoA-I(R160L)Oslo and apoA-I(R149A) promoted the formation of prebeta1 and alpha4-HDL subpopulations and gave a mixture of discoidal and spherical particles. apoA-I(R151C)Paris generated subpopulations of different sizes that migrate between prebeta and alpha-HDL and formed mostly spherical and a few discoidal particles. Simultaneous treatment of mice with adenovirus expressing any of the three mutants and human LCAT normalized plasma apoA-I, HDL cholesterol levels and the CE/TC ratio. It also led to the formation of spherical HDL particles consisting mostly of alpha-HDL subpopulations of larger size. The correction of the aberrant HDL phenotypes by treatment with LCAT suggests a potential therapeutic intervention for HDL abnormalities that result from specific mutations in apoA-I.
authors.affiliation: Molecular Genetics, Departmental of Medicine and Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Georgios
authors.initials: G
authors.lastname: Koukos
authors.forename: Angeliki
authors.initials: A
authors.lastname: Chroni
authors.forename: Adelina
authors.initials: A
authors.lastname: Duka
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.forename: Vassilis I
authors.initials: VI
authors.lastname: Zannis
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000256:Adenoviridae; D000818:Animals; D016632:Apolipoprotein A-I / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D002853:Chromatography, Liquid; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D015316:Genetic Therapy; D006801:Humans; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000737:chemistry / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008099:Liver / Q000378:metabolism; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000235:genetics / Q000378:metabolism*
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D008055:Lipids; D008074:Lipoproteins; D008075:Lipoproteins, HDL; D050505:Mutant Proteins; C034366:discoidal lipoproteins; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase