title: Antiapoptotic activity of Akt is down-regulated by Ca2+ in myocardiac H9c2 cells. Evidence of Ca(2+)-dependent regulation of protein phosphatase 2Ac.
abstract: Cell survival signaling of the Akt/protein kinase B pathway was influenced by a change in the cytoplasmic free calcium concentration ([Ca2+]i) for over 2 h via the regulation of a Ser/Thr phosphatase, protein phosphatase 2Ac (PP2Ac), in rat myocardiac H9c2 cells. Akt was down-regulated when [Ca2+]i was elevated by thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, but was up-regulated when it was suppressed by 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester (BAPTA-AM), a cell permeable Ca2+ chelator. The inactivation of Akt was well correlated with the susceptibility to oxidant-induced apoptosis in H9c2 cells. To investigate the mechanism of the Ca(2+)-dependent regulation of Akt via the regulation of PP2A, we examined the transcriptional regulation of PP2Acalpha in H9c2 cells with Ca2+ modulators. Transcription of the PP2Acalpha gene was increased by thapsigargin but decreased by BAPTA-AM. The promoter activity was examined and the cAMP response element (CRE) was found responsible for the Ca(2+)-dependent regulation of PP2Acalpha. Furthermore, phosphorylation of CRE-binding protein increased with thapsigargin but decreased with BAPTA-AM. A long term change of [Ca2+]i regulates PP2Acalpha gene transcription via CRE, resulting in a change in the activation status of Akt leading to an altered susceptibility to apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology in Disease, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Medicine, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Yasuoka
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Ihara
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ikeda
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Miyahara
authors.forename: Takahito
authors.initials: T
authors.lastname: Kondo
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kohno
mesh_terms: D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D015536:Down-Regulation; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009206:Myocardium / Q000166:cytology*; D019319:Okadaic Acid / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000737:chemistry*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D019319:Okadaic Acid; D004533:Egtazic Acid; D019284:Thapsigargin; D004247:DNA; D006861:Hydrogen Peroxide; D007770:L-Lactate Dehydrogenase; D008156:Luciferases; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010749:Phosphoprotein Phosphatases; D002118:Calcium