title: ApoA-I enhances generation of HDL-like lipoproteins through interaction between ABCA1 and phospholipase Cγ in rat astrocytes.
abstract: In the previous paper, we reported that apolipoprotein (apo) A-I enhances generation of HDL-like lipoproteins in rat astrocytes to be accompanied with both increase in tyrosine phosphorylation of phospholipase Cγ (PL-Cγ) and PL-Cγ translocation to cytosolic lipid-protein particles (CLPP) fraction. In this paper, we studied the interaction between apoA-I and ATP-binding cassette transporter A1 (ABCA1) to relate with PL-Cγ function for generation of HDL-like lipoproteins in the apoA-I-stimulated astrocytes. ABCA1 co-migrated with exogenous apoA-I with apparent molecular weight over 260kDa on SDS-PAGE when rat astrocytes were treated with apoA-I and then with a cross-linker, BS3. The solubilized ABCA1 of rat astrocytes was associated with the apoA-I-immobilized Affi-Gel 15. An LXR agonist, To901317, increased the cellular level of ABCA1, association of apoA-I with ABCA1 and apoA-I-mediated lipid release in rat astrocytoma GA-1/Mock cells where ABCA1 expression at baseline is very low. PL-Cγ was co-isolated by apoA-I-immobilized Affi-Gel 15 and co-immunoprecipitated by anti-ABCA1 antibody along with ABCA1 from the solubilized membrane fraction of rat astrocytes. The SiRNA of ABCA1 suppressed not only the PL-Cγ binding to ABCA1 but also the tyrosine phosphorylation of PL-Cγ. A PL-C inhibitor, U73122, prevented generation of apoA-I-mediated HDL-like lipoproteins in rat astrocytes. To901317 increased the association of PL-Cγ with ABCA1 in GA-1/Mock cells dependently on the increase of cellular level of ABCA1 without changing that of PL-Cγ. These findings suggest that the exogenous apoA-I augments the interaction between PL-Cγ and ABCA1 to stimulate tyrosine phosphorylation and activation of PL-Cγ for generation of HDL-like lipoproteins in astrocytes.
authors: Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. jitoh@@med.nagoya-cu.ac.jp
authors: Jin-ichi
authors: J
authors: Ito
authors: Yuko
authors: Y
authors: Nagayasu
authors: Alireza
authors: A
authors: Kheirollah
authors: Sumiko
authors: S
authors: Abe-Dohmae
authors: Shinji
authors: S
authors: Yokoyama
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism / Q000494:pharmacology; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004963:Estrenes / Q000494:pharmacology; D005333:Fetus; D020868:Gene Silencing; D055767:Immobilized Proteins / Q000737:chemistry / Q000378:metabolism; D047468:Immunoprecipitation; D008075:Lipoproteins, HDL / Q000096:biosynthesis*; D051379:Mice; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport / Q000187:drug effects; D011760:Pyrrolidinones / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D003432:Cross-Linking Reagents; D004963:Estrenes; D055767:Immobilized Proteins; D008075:Lipoproteins, HDL; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D034741:RNA, Small Interfering; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D051966:Phospholipase C gamma