ABCG8 Background Information The ABCG (White) subfamily of ABC transporters, which includes ABCG1, ABCG5 and ABCG8, are critically involved in the regulation of lipid-trafficking mechanisms in macrophages, hepatocyes and intestinal mucosa cells. ABCG8 (also designated Sterolin-2) is expressed in the liver, small intestine and colon. ABCG8 normally cooperates with ABCG5 to limit intestinal absorption and to promote biliary excretion of sterols, whereas mutated forms of ABCG8 and ABCG5 cause sterol accumulation and atherosclerosis. ABCG8 and ABCG5 genes are also distinct targets of the LXRa and LXRb oxysterol receptors, which serve as sterol sensors to coordinately regulate sterol catabolism, storage, efflux and elimination. Mutations in either ABCG8 or ABCG5 lead to sitosterolemia, a rare autosomal recessive disorder characterized by hyper-absorption of all sterols, including cholesterol and plant and shellfish sterols. Patients with this disease are hypercholesterolemic and frequently develop xanthomas, accelerated atherosclerosis and premature coronary artery disease.
