Multidrug resistance protein 3 (ATP-binding cassette sub-family B member 4, ABCB4 aka MDR3) mediates the ATP-dependent export of organic anions and drugs from hepatocytes into the canalicular lumen in the presence of bile salts. ABCB4 is especially important for the export of phospholipids such as phosphatidylcholine (PC) from the plasma membrane of hepatocytes (Morita et al. 2007). Biliary phospholipids associate with bile salts and cholesterol in mixed micelles, thereby reducing the detergent activity and cytotoxicity of bile salts and preventing cholesterol crystallisation. Thus, ABCB4 plays a crucial role in bile formation and lipid homeostasis (Morita & Terada 2014).
phospholipid transporter activity of ABCB4 [plasma membrane]