Munehira Youichi, Ohnishi Tomohiro, Kawamoto Shinobu, Furuya Akiko, Shitara Kenya, Imamura Michihiro, Yokota Toshifumi, Takeda Shin'ichi, Amachi Teruo, Matsuo Michinori, Kioka Noriyuki, Ueda Kazumitsu
Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
J Biol Chem. 2004 Apr 9;279(15):15091-5. doi: 10.1074/jbc.M313436200. Epub 2004 Jan 13.
ABCA1 (ATP-binding cassette transporter A1) mediates the release of cellular cholesterol and phospholipid to form high density lipoprotein. Functions of ABCA1 are highly regulated at the transcriptional and post-transcriptional levels, and the synthesized ABCA1 protein turns over rapidly with a half-life of 1-2 h. To examine whether the functions of ABCA1 are modulated by associated proteins, a yeast two-hybrid library was screened with the C-terminal 120 amino acids of ABCA1. Two PDZ (PSD95-Discs large-ZO1) proteins, alpha1-syntrophin and Lin7, were found to interact with ABCA1. Immunoprecipitation revealed that alpha1-syntrophin interacted with ABCA1 strongly and that the interaction was via the C-terminal three amino acids SYV of ABCA1. Co-expression of alpha1-syntrophin in human embryonic kidney 293 cells retarded degradation of ABCA1 and made the half-life of ABCA1 five times longer than in the cells not expressing alpha1-syntrophin. This effect is not common among PDZ-containing proteins interacting with ABCA1, because Lin7, which was also found to interact with the C terminus region of ABCA1, did not have a significant effect on the half-life of ABCA1. Co-expression of alpha1-syntrophin significantly increased the apoA-I-mediated release of cholesterol. ABCA1 was co-immunoprecipitated with alpha1-syntrophin from mouse brain. These results suggest that alpha1-syntrophin is involved in intracellular signaling, which determines the stability of ABCA1 and modulates cellular cholesterol release.
