Which transporter regulates bile phospholipid transport in hepatocytes?
Phosphatidylcholine supply to bile is governed by canalicular ABC transporter ABCB4, also known as multidrug resistance protein 2 or 3 in rodents and humans. This ATP-driven floppase actively translocates endogenous phosphatidylcholine from inner cytoplasmic leaflet to outer exoplasmic leaflet of hepatocyte canalicular membrane. Bile salts secreted via ABCB11 then extract phospholipid into bile forming mixed micelles that solubilize cholesterol and shield ductal epithelium from detergent toxicity of bile acids. ABCB1 MDR1 contributes to hydrophobic xenobiotic efflux but does not move bulk phos
Ref: Oude Elferink & Paulusma, Pflugers Arch 2007, ABCB4 phosphatidylcholine transport.