Interaction of plasma high density lipoprotein HDL2b (d 1.063–1.100 g/ml) with single‐bilayer liposomes of dimyristoylphosphatidylcholine

Abstract

AbstractIncubation of a major subfraction, HDL2b (d 1.063–1.100 g/ml), of human plasma high density lipoproteins, HDL (d 1.063–1.21 g/ml), with single‐bilayer liposomes of dimyristoylphosphatidylcholine (DMPC) resulted in uptake of DMPC by the HDL2b and dissociation of lipid‐free apolipoprotein A‐I (apoA‐I). In the presence of excess DMPC, the dissociated apoA‐I was also incorporated with DMPC into discoidal complexes. Preliminary studies with model apoA‐I‐DMPC complexes indicated that they also can interact with native HDL2b with the resultant transfer of their DMPC to HDL2b and the concomitant release of their apoA‐I. After interaction of HDL2b with DMPC liposomes, the DMPC‐enriched HDL2b product showed a lower hydrated density and a larger particle size than the control HDL2b. The molecular properties of the lipoprotein product suggest that stabilization of the apoA‐I‐depleted HDL2b probably occurred via substitution of DMPC for the apoA‐I at the HDL2b surface rather than by fusion of the apoA‐I‐depleted HDL2b. The above interactions of HDL2b with single‐bilayer liposomes and discoidal complexes indicate pathways of phospholipid transfer relevant to the possible role of HDL in the metabolism of lipoprotein surface components in vivo.