Figure 1.

Modes of lipoprotein-mediated cargo transfer to/from cells. (a) Aqueous diffusion transfers cholesterol from lipoprotein particles to membranes in close proximity by passing the aqueous layer between the lipid membranes. (b) Fusion of lipoprotein particles yields transfer of all components of the lipoprotein particle. (c) Tethering function of receptors or the glycocalyx mediates aqueous diffusion. (d) Receptor-mediated endocytosis occurs by specific binding of certain apolipoproteins by their respective receptors and subsequent endocytosis. (e) Cholesterol efflux via ABC cholesterol transporters removes excess cholesterol from the cell to cholesterol-poor HDL particles.