CETP binds preferentially to the edge of nascent discoidal HDL particles, with affinity boosted 3- to 10-fold by cholesteryl ester or cholesterol content (J Biol Chem 1995)

Original title: Molecular determinants of plasma cholesteryl ester transfer protein binding to high density lipoproteins

J Biol Chem · 12 May 1995 · 9

Bruce C, Davidson WS, Kussie P, Lund-Katz S, Phillips MC, Ghosh R, Tall AR

To understand how CETP interacts with HDL, the binding of pure recombinant CETP to POPC/apoA-I discoidal particles was studied. CETP-disc complexes (10-nm discs) migrated at 12-16 nm diameter versus about 7.5 nm for CETP alone, with CETP binding as monomers without displacing apoA-I, localizing to the disc edge by electron microscopy. Discs made with apoA-I or apoA-II had a similar dissociation constant (Kd = 120 nM), while including cholesteryl oleate, cholesterol, or phosphatidylinositol increased CETP binding affinity 3- to 10-fold (Kd = 20-30 nM); plasma HDL3 had a Kd of about 450 nM. Larger 10-nm discs bound CETP with much higher affinity than smaller 7.8-nm discs (Kd = 1-2 microM), while spherical particles containing core neutral lipid bound CETP even more tightly (Kd = 50-100 nM). CETP binds preferentially to nascent, cholesterol-rich HDL particles over mature HDL.

Original abstract

The plasma cholesteryl ester transfer protein (CETP) mediates the transfer of neutral lipids between lipoproteins and is associated with high density lipoproteins (HDL). To understand the mechanism of interaction of CETP with HDL, we studied the binding of pure recombinant CETP to 1-palmitoyl-2-oleoylphosphatidylcholine (POPC)/apoA-I discoidal particles. Separating bound from free CETP using native gradient gel electrophoresis, complexes of CETP with 10-nm hydrodynamic diameter discoidal particles migrated with a diameter of 12-16 nm, compared with approximately 7.5 nm for CETP. At lower ratios of CETP to discs, CETP bound to discs without displacement of apoA-I. CETP alone was unable to generate discoidal complexes. Cross-linking and fluorescence resonance energy transfer experiments indicated that CETP bound to discs as monomers. Cross-linking of CETP to apoA-I in discs suggested proximity of apoA-I and CETP. By negative-stain electron microscopy, discoidal complexes containing CETP and CETP monoclonal antibody showed localization of antibody molecules to the disc edge, suggesting that CETP was bound to the disc edge. The binding of CETP to discs of different composition or size was studied. Discs (10-nm Stokes diameter) prepared with either apoA-I or apoA-II had a similar Kd (120 nM). Inclusion of 1 mol % cholesteryl oleate, 5 mol % cholesterol, or 6 mol % phosphatidylinositol increased the binding affinity of CETP 3-10 times (20-30 nM). In comparison, plasma HDL3 had a Kd of approximately 450 nM. For POPC/apoA-I discs, 10-nm discs bound CETP with much higher affinity than smaller 7.8-nm discs (Kd = 1-2 microM). 7.7-nm hydrodynamic diameter POPC/apoA-I spherical particles containing either triolein or cholesteryl oleate in their core bound CETP with higher affinity (Kd = 50-100 nM) than 7.8-nm POPC/apoA-I discs. Thus, CETP appears to bind to the perimeter of discoidal particles, possibly in a process in which flexible segments in apoA-I or apoA-II accommodate CETP at the disc edge. The binding of CETP to HDL is markedly influenced by overall particle size and shape and by lipid composition, and the increased binding affinity for cholesterol- and cholesteryl ester-containing discs suggests a higher affinity of CETP for nascent than mature HDL.

Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 19 August 2026. Methods.