抄録
The A subclass of the ATP-binding cassette (ABC) transporter superfamily has a structural feature that distinguishes it from other ABC transporters, and is proposed to be involved in transmembrane transport of endogenous lipids. Here we cloned the full-length cDNA of a novel ABC transporter ABCA14, which belongs to the A subclass. Mouse ABCA14 is a protein of 1,733 amino acid residues, and is most homologous to the mouse ABCA3 and sea urchin ABCA (suABCA), with amino acid identity of 55.2% and 35.4%, respectively. RNA blot and quantitative real-time PCR analyses showed that ABCA14 mRNA is exclusively expressed in the testis. Examination of testis by in situ hybridization determined that ABCA14 mRNA is expressed in germ cells including spermatogonia and spermatocytes in the seminiferous tubule. Immunoblot analysis using a specific antibody showed that ABCA14 is a protein of 200kDa, and immunohistochemical analysis showed that the protein is detected in the region of anterior head of sperm and elongated spermatids. Since the removal of cholesterol from the sperm plasma membrane is thought to be critical during capacitation, ABCA14 may play a pivotal role in the efflux of endogenous cholesterol during sperm capacitation. [Jpn J Physiol 54 Suppl:S89 (2004)]
