HDL biology
Cholesteryl ester diffusion and self-association within the HDL phospholipid bilayer set the pace of CETP-mediated lipid transfer (Arch Biochem Biophys 2014)
Original title: Cholesteryl ester diffusion, location and self-association constraints determine CETP activity with discoidal HDL: excimer probe study
Using excimer fluorescent probes to study cholesteryl ester transfer by recombinant cholesteryl ester transfer protein (CETP) between reconstituted discoidal HDL particles containing either unsaturated POPC or saturated DPPC phospholipids, cholesteryl ester exchange followed heterogeneous kinetics, with a much larger fast-exchanging probe pool in POPC than DPPC complexes, and probe accessibility to CETP increased with temperature. Acceptor particles produced noncompetitive inhibition of probe transfer. The maximal velocity (0.063 microM/min) and catalytic rate constant (0.42/s), together with similar Michaelis constant (0.9 microM) and inhibition constant (2.8 microM) values for POPC-containing particles, indicate efficient cholesteryl ester transfer between nascent HDL with unsaturated phosphatidylcholine in vivo. The phospholipid matrix of discoidal HDL likely governs CETP activity through the self-association, diffusivity, and location of cholesteryl ester within the bilayer.
Original abstract
The transfer of cholesteryl ester by recombinant cholesteryl ester transfer protein (CETP) between reconstituted discoidal high-density lipoprotein (rHDL) was studied. Particles contained apolipoprotein A-I, unsaturated POPC or saturated DPPC and cholesteryl ester as cholesteryl 1-pyrenedecanoate (CPD) or cholesteryl laurate (CL) in donor and acceptor rHDL, respectively. Probe dynamics fulfilled the quenching sphere-of-action model. The cholesteryl ester exchange between donor and acceptor particles was characterized by a heterogeneous kinetics; the fast exchanging CPD pool was much higher in a case of POPC compared to DPPC complexes. Probe fraction accessible to CETP increased with temperature, suggesting a more homogeneous probe distribution. Noncompetitive inhibition of probe transfer by acceptor particles was observed. The values of Vmax (0.063μMmin(-1)) and catalytic rate constant kcat (0.42s(-1)) together with a similarity of Km (0.9μM CPD) and KI (2.8μM CL) values for POPC-containing rHDL suggest the efficient cholesteryl ester transfer between nascent HDL with unsaturated phosphatidylcholine in vivo. The phospholipid matrix in discoidal HDL may underlie CETP activity through the self-association, diffusivity and location of cholesteryl ester in the bilayer, the accessibility of cholesteryl ester to cholesterol-binding site in apoA-I structure and the binding of cholesteryl ester, positionable by apoA-I, to CETP.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 19 August 2026. Methods.