Which ABC transporter plays a role in cholesterol and phospholipid transport in hepatocytes?
Row labeled Q30 appears truncated but query addresses which ABC transporter handles cholesterol and phospholipid transport in hepatocytes. In canalicular membrane ABCB4 MDR3 is established phosphatidylcholine floppase essential for biliary phospholipid secretion, pairing with bile salt export via ABCB11 and cholesterol export via ABCG5/G8. Its ATP-driven flipping of phosphatidylcholine to outer leaflet allows bile acids to extract lipid into mixed micelles that solubilize cholesterol and buffer bile acid detergent toxicity. At sinusoidal membrane, ABCA1 effluxes cholesterol and phospholipid to apolipoprotein A1 forming nascent HDL, contributing to reverse cholesterol transport. ABCB1 MDR1 exports amphipathic drugs xenobiotics rather than bulk biliary lipids, while SGLT1 and SGLT2 are sodium-glucose cotransporters secondary active members of SLC5 family irrelevant to lipid secretion. Clinically ABCB4 defects produce low-phospholipid bile, cholestasis, cholelithiasis and progressive liver injury, highlighting distinct partitioning of lipid transport functions among hepatic ABC proteins for bile formation and systemic lipoprotein metabolism. Such detailed mechanistic insight is frequently examined in competitive tests including NEET, CUET, CSIR-NET and GATE where transporter classification, energetics and disease linkage are integrated into problem-solving questions.
Ref: Borst et al., Annu Rev Biochem 2000, ABC transporters in lipid transport; Alberts, Chapter 11.