Abstract
The A subclass of the ATP-binding cassette (ABC) transporter superfamily possesses a structural feature that distinguishes it from other ABC transporters, and is proposed to be involved in transmembrane transport of endogenous lipids. We previously cloned the full-length cDNA of mouse ABCA17, a novel ABC transporter belonging to the A subclass, and found that the protein is localized in the anterior head of sperm and elongated spermatids. However, the functional significance of ABCA17 is unknown. To determine if ABCA17 is involved in regulation of lipid metabolism, we performed metabolic labeling analysis in HEK293 cells using [C14]-labeled acetate. When expressed in HEK293 cells, ABCA17 protein was localized to the ER. Analysis revealed that intracellular esterified lipids including cholesteryl esters, fatty acid esters, and triacylglycerols were significantly decreased in HEK293 cells stably expressing ABCA17 compared to those in untransfected cells. These results suggest that ABCA17 may be involved in sorting esterified neutral lipids from the ER to other intracellular compartments. Since a decrease in cholesterol is critical during capacitation, ABCA17 may well play an important role in sperm capacitation. [Jpn J Physiol 55 Suppl:S83 (2005)]
