抄録
Among the ABCA subclass of ATP-binding cassette (ABC) transporters, ABCA1 and ABCA4 are transmembrane transporters of intracellular lipids, and mutations of these genes cause Tangier disease accompanying high density lipoprotein deficiency and Stargardt's macular dystrophy in human, respectively. We cloned ABCA3 from human lung, and found that ABCA3 is expressed predominantly at the limiting membrane of the lamellar bodies of alveolar type II cells in lung. Recently, various mutations in the ABCA3 gene have been reported in newborns with fatal surfactant deficiency. As pulmonary surfactant is composed mainly of phospholipids and specific surfactant proteins, ABCA3 may well function as a transmembrane transporter of the lipid components of pulmonary surfactant. We recently cloned a novel, mouse sperm-specific ABCA17 that is most homologous to ABCA3. Metabolic labeling analysis revealed that intracellular esterified lipids including cholesteryl esters were significantly decreased in HEK293 cells stably expressing ABCA17. A decrease in cholesterol is critical during capacitation, suggesting that ABCA17 plays a role in sperm capacitation. In this symposium, I will present recent findings focusing on ABCA3 and ABCA17, and discuss the functional implications for ABCA transporters in lipid transport and metabolism. [Jpn J Physiol 55 Suppl:S31 (2005)]
