title: Apolipoprotein A-I induces tubulin phosphorylation in association with cholesterol release in fetal rat astrocytes.
abstract: We previously identified cytosolic lipid-protein particles (CLPP) having size and density of HDL in rat astrocytes, to which apoA-I induces translocation of cholesterol, caveolin-1 and protein kinase Cα (PKCα) following its association with microtubules prior to cholesterol release/biogenesis of HDL (JBC 277: 7929, 2002; JLR 45: 2269, 2004). To further understand the physiological relevance of these findings, we investigated the CLPP/microtubule association and its role in intracellular cholesterol trafficking by using a technique of reconstituted microtubule-like filaments (rMT) in rat astrocyte cytosol. When the cells were pretreated with apoA-I, α-tubulin as a 52-kDa protein in rMT was found phosphorylated while α-tubulin in a soluble monomeric form was little phosphorylated. The phosphorylation took place coincidentally to apoA-I-induced association with rMT of CLPP, a complex containing PKCα, and was suppressed by a PKC inhibitor, Bis indolylmaleimide 1 (BIM). α-Tubulin dissociated from CLPP when phosphorylated, and it poorly bound to CLPP once dissociated. BIM did not influence association of PKCα with rMT but suppressed apoA-I-induced cholesterol translocation to the cytosol from the ER/Golgi apparatus and apoA-I-mediated cholesterol release. We thereby concluded that α-tubulin phosphorylation by PKCα on CLPP is involved in reversible CLPP association with the microtubules and intracellular cholesterol trafficking for apoA-I-dependent HDL biogenesis/cholesterol release in rat astrocytes.
authors.affiliation: Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Jin-Ichi
authors.initials: J
authors.lastname: Ito
authors.affiliation: Nutritional Health Science Research Center, Chubu University, Kasugai 487-8501, Japan; Department of Applied Bioscience and Biotechnology, Chubu University, Kasugai 487-8501, Japan.
authors.forename: Rui
authors.initials: R
authors.lastname: Lu
authors.affiliation: Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nagayasu
authors.affiliation: Nutritional Health Science Research Center, Chubu University, Kasugai 487-8501, Japan; Department of Applied Bioscience and Biotechnology, Chubu University, Kasugai 487-8501, Japan. Electronic address: syokoyam@isc.chubu.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics* / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005333:Fetus; D018507:Gene Expression Regulation, Developmental; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D061251:Primary Cell Culture; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D014404:Tubulin / Q000235:genetics* / Q000378:metabolism
chemical_list: D016632:Apolipoprotein A-I; C495537:Cav1 protein, rat; D051242:Caveolin 1; D007211:Indoles; D008301:Maleimides; D047428:Protein Kinase Inhibitors; D014404:Tubulin; D002784:Cholesterol; D011493:Protein Kinase C; C070515:bisindolylmaleimide I
keywords: ApoA-I; Astrocyte; Caveolin-1; Microtubule; Protein kinase C; Tubulin