Processes Promoting Efflux of Cholesterol from Cells to HDL Particles Extracellular space Cholesterol deficient, phospholipid depleted apo A-1 Discoidal HDL LCAT Small spherical HDL LCAT ABCA1 Diffusion SR-B1 Diffusion SR-B1 ABCG1 Cell membrane FC FC FC Larger spherical HDL Diffusion SR-B1 ABCG1 FC Adapted from Barter P, Rye KA. High density lipoprotein cholesterol: the new target. A handbook for clinicians. 3rd ed. Birmingham, UK: Sherbourne Gibbs, 2007:31. Rosen R et al. Circulation. 2012.