title: Alteration of negatively charged residues in the 89 to 99 domain of apoA-I affects lipid homeostasis and maturation of HDL.
abstract: In this study, we investigated the role of positively and negatively charged amino acids within the 89-99 region of apolipoprotein A-I (apoA-I), which are highly conserved in mammals, on plasma lipid homeostasis and the biogenesis of HDL. We previously showed that deletion of the 89-99 region of apoA-I increased plasma cholesterol and phospholipids, but it did not affect plasma triglycerides. Functional studies using adenovirus-mediated gene transfer of two apoA-I mutants in apoA-I-deficient mice showed that apoA-I[D89A/E91A/E92A] increased plasma cholesterol and caused severe hypertriglyceridemia. HDL levels were reduced, and approximately 40% of the apoA-I was distributed in VLDL/IDL. The HDL consisted of mostly spherical and a few discoidal particles and contained preβ1 and α4-HDL subpopulations. The lipid, lipoprotein, and HDL profiles generated by the apoA-I[K94A/K96A] mutant were similar to those of wild-type (WT) apoA-I. Coexpression of apoA-I[D89A/E91A/E92A] and human lipoprotein lipase abolished hypertriglyceridemia, restored in part the α1,2,3,4 HDL subpopulations, and redistributed apoA-I in the HDL2/HDL3 regions, but it did not prevent the formation of discoidal HDL particles. Physicochemical studies showed that the apoA-I[D89A/E91A/E92A] mutant had reduced α-helical content and effective enthalpy of thermal denaturation, increased exposure of hydrophobic surfaces, and increased affinity for triglyceride-rich emulsions. We conclude that residues D89, E91, and E92 of apoA-I are important for plasma cholesterol and triglyceride homeostasis as well as for the maturation of HDL.
authors.affiliation: Molecular Genetics, Boston University School of Medicine, Boston, MA. USA.
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Kateifides
authors.forename: Irina N
authors.initials: IN
authors.lastname: Gorshkova
authors.forename: Adelina
authors.initials: A
authors.lastname: Duka
authors.forename: Angeliki
authors.initials: A
authors.lastname: Chroni
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.forename: Vassilis I
authors.initials: VI
authors.lastname: Zannis
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D000818:Animals; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D017124:Conserved Sequence; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D004655:Emulsions; D005786:Gene Expression Regulation; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016296:Mutagenesis; D009154:Mutation; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D014280:Triglycerides / Q000097:blood / Q000378:metabolism*
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D016632:Apolipoprotein A-I; D004655:Emulsions; D008075:Lipoproteins, HDL; D014280:Triglycerides; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine