Molecular basis of cholesterol homeostasis: lessons from Tangier disease and ABCA1.

High-density lipoproteins (HDLs) play a role in transporting cholesterol from peripheral tissues to the liver for elimination from the body. Two hallmarks of cardiovascular disease are the presence of sterol-laden macrophages in the artery wall and reduced plasma HDL levels. A cell-membrane protein called ABCA1 mediates the secretion of excess cholesterol from cells into the HDL metabolic pathway. Mutations in ABCA1 cause Tangier disease, a severe HDL deficiency syndrome characterized by accumulation of cholesterol in tissue macrophages and prevalent atherosclerosis. Because of its ability to deplete macrophages of cholesterol and to raise plasma HDL levels, ABCA1 has become a promising therapeutic target for preventing cardiovascular disease.