title: Molecular mechanism of the blockade of plasma cholesteryl ester transfer protein by its physiological inhibitor apolipoprotein CI.
abstract: Genetically engineered mice demonstrated that apolipoprotein (apo) CI is a potent, physiological inhibitor of plasma cholesteryl ester transfer protein (CETP) activity. The goal of this study was to determine the molecular mechanism of the apoCI-mediated blockade of CETP activity. Kinetic analyses revealed that the inhibitory property of apoCI is independent of the amount of active CETP, but it is tightly dependent on the amount of high density lipoproteins (HDL) in the incubation mixtures. The electrostatic charge of HDL, i.e. the main carrier of apoCI in human plasma, is gradually modified with increasing amounts of apoCI, and the neutralization of apoCI lysine residues by acetylation produces a marked reduction in its inhibitory potential. The inhibitory property of full-length apoCI is shared by its C-terminal alpha-helix with significant electrostratic properties, whereas its N-terminal alpha-helix with no CETP inhibitory property has no effect on HDL electronegativity. Finally, binding experiments demonstrated that apoCI and to a lower extent its C-terminal alpha-helix are able to disrupt CETP-lipoprotein complexes in a concentration-dependent manner. It was concluded that the inhibition of CETP activity by apoCI is in direct link with its specific electrostatic properties, and the apoCI-mediated reduction in the binding properties of lipoproteins results in weaker CETP-HDL interactions and fewer cholesteryl ester transfers.
authors.affiliation: Laboratoire de Biochimie des Lipoprotéines, INSERM U498, Faculté deMédecine, Dijon, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Dumont
authors.forename: Thomas
authors.initials: T
authors.lastname: Gautier
authors.forename: Jean-Paul Pais
authors.initials: JP
authors.lastname: de Barros
authors.forename: Hélène
authors.initials: H
authors.lastname: Laplanche
authors.forename: Denis
authors.initials: D
authors.lastname: Blache
authors.forename: Patrick
authors.initials: P
authors.lastname: Ducoroy
authors.forename: Jamila
authors.initials: J
authors.lastname: Fruchart
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Fruchart
authors.forename: Philippe
authors.initials: P
authors.lastname: Gambert
authors.forename: David
authors.initials: D
authors.lastname: Masson
authors.forename: Laurent
authors.initials: L
authors.lastname: Lagrost
mesh_terms: D000107:Acetylation; D053302:Apolipoprotein C-I; D001056:Apolipoproteins C / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000097:blood / Q000378:metabolism*; D053480:Cholesterol Ester Transfer Proteins; D006023:Glycoproteins / Q000037:antagonists & inhibitors* / Q000097:blood / Q000378:metabolism*; D006801:Humans
chemical_list: D053302:Apolipoprotein C-I; D001056:Apolipoproteins C; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D006023:Glycoproteins