Trafficking of canalicular ABC transporters in hepatocytes.

ATP-binding cassette (ABC) transporters located in the hepatocyte canalicular membrane of mammalian liver are critical players in bile formation and detoxification. Although ABC transporters have been well characterized functionally, only recently have several canalicular ABC transporters been cloned and their molecular nature revealed. Subsequently, development of specific antibodies has permitted a detailed investigation of ABC transporter intrahepatic distribution under varying physiological conditions. It is now apparent that there is a complex array of ABC transporters in hepatocytes. ABC transporter molecules reside in intrahepatic compartments and are delivered to the canalicular domain following increased physiological demand to secrete bile. Insufficient amounts of ABC transporters in the bile canalicular membrane result in cholestasis (i.e., bile secretory failure). Therefore, elucidation of the intrahepatic pathways and regulation of ABC transporters may help to understand the cause of cholestasis at a molecular level and provide clues for novel therapies.