Fig. 4.

Summary of the mechanisms of cholesterol uptake, synthesis, and storage and the involvement of oxysterols and of cholesterol in cholesterol regulation. The cell can take up cholesterol esters via lipoprotein receptors, or cholesterol can be synthesized via the mevalonate pathway under SREBP-2 regulation. Excess cholesterol can be stored as cholesterol esters in lipid droplets or exported by ABC transporters onto lipoprotein particles. Symbols are as indicated in Figs. 1 and 2. Cell compartments are color coded, endoplasmic reticulum light blue, Golgi light gray, endosome-lysosomal compartment gray, and nucleus pale yellow.