HEPATOCELLULAR TRANSPORT - ROLE OF ATP-BINDING CASSETTE PROTEINS

The interest of mammalian biologists in ATP-binding cassette (ABC) pro teins is relatively recent. However, ABC proteins are widespread in di stribution and have long been known to play an important transport rol e in prokaryotes. This review includes a brief overview of the structu re, regulation, and varied functions of ABC proteins in different cell types as well as a synopsis of the emerging role of ABC proteins in h uman biology and disease. The review then focuses on the established ( canalicular secretion of organic cations by the multidrug resistance, or MDR 1, gene product; ductular secretion of fluid and electrolytes m ediated by CFTR), probable (biliary phospholipid secretion by the MDR 2 gene product; secretion of non bile acid organic anions by the multi drug resistance protein, or MRP) and possible (bile acid secretion; bi liary secretion of the signaling molecule, ATP; hormone transport) rol es of known and novel ABC proteins in hepatobiliary secretion.