Role of ABCG1 and other ABCG family members in lipid metabolism

The molecular cloning and identification of mutations in ATP-binding casset te transporters in hereditary diseases have greatly expanded our knowledge of the normal physiology of intracellular lipid transport processes. In add ition to the well-known ATP-binding cassette transporter A1 (ABCA1) molecul e, ABC transporters belonging to the ABCG (NVhite) subfamily (ABCG1, ABCG5, and ABCG8) have been shown to be critically involved in the regulation of lipid-trafficking mechanisms in macrophages, hepatocytes, and intestinal mu cosa cells. ABCG1, the product of a sterol-induced gene, participates in ch olesterol and phospholipid efflux. The ABCG5 and ABCG8 transporters, defect ive in beta -sitosterolemia, are also now considered interesting targets in the control and influence of total body sterol homeostasis. In this review , advances referring to the regulation and function of ABCG half-size trans porters are summarized and discussed. In addition, new implications for the transcriptional control, as well as the intracellular routing and localiza tion, of these proteins are presented.