title: Alpha1-syntrophin modulates turnover of ABCA1.
abstract: 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.
authors.affiliation: Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Youichi
authors.initials: Y
authors.lastname: Munehira
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Shinobu
authors.initials: S
authors.lastname: Kawamoto
authors.forename: Akiko
authors.initials: A
authors.lastname: Furuya
authors.forename: Kenya
authors.initials: K
authors.lastname: Shitara
authors.forename: Michihiro
authors.initials: M
authors.lastname: Imamura
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Yokota
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Takeda
authors.forename: Teruo
authors.initials: T
authors.lastname: Amachi
authors.forename: Michinori
authors.initials: M
authors.lastname: Matsuo
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kioka
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Ueda
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001921:Brain / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000378:metabolism / Q000502:physiology*; D010743:Phospholipids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012323:RNA Processing, Post-Transcriptional; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C119588:LIN-7 protein, mammalian; C486532:LIN7A protein, human; C486531:LIN7C protein, human; D008565:Membrane Proteins; D009124:Muscle Proteins; D010743:Phospholipids; D033921:Vesicular Transport Proteins; C091825:syntrophin alpha1; D002784:Cholesterol