title: Membrane localization of all class I PI 3-kinase isoforms suppresses c-Myc-induced apoptosis in Rat1 fibroblasts via Akt.
abstract: Phosphoinositide 3'-kinases (PI3Ks) constitute a family of lipid kinases implicated in signal transduction through tyrosine kinase receptors and heterotrimeric G protein-linked receptors. PI3Ks are heterodimers made up of four different 110-kDa catalytic subunits (p110alpha, p110beta, p110gamma, and p110delta) and a smaller regulatory subunit. Despite a clear implication of PI3Ks in survival signaling, the contribution of the individual PI3K isoforms has not been elucidated. To address this issue, we generated Rat1 fibroblasts that co-express c-Myc and membrane targeted derivates of the different p110 isoforms. Here we present data for the first time showing that activation of PI3-kinase signaling through membrane localization of p110beta, p110gamma, and p110delta protects c-Myc overexpressing Rat1 fibroblasts from apoptosis caused by serum deprivation like it has been described for p110alpha. Expression of each p110 isoform reduces significantly caspase-3 like activity in this apoptosis model. Decreased caspase-3 activity correlates with the increase in Akt phosphorylation in cells that contain one of the myristoylated p110 isoforms. p110 isoform-mediated protection from cell death was abrogated upon expression of a kinase-negative version of Akt.
authors.affiliation: Experimental Therapeutics Program, Centro Nacional de Investigaciones Oncologicas, Melchor Fernandez Almagro, 3, 28029 Madrid, Spain.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Link
authors.forename: Aranzazu
authors.initials: A
authors.lastname: Rosado
authors.forename: Jesus
authors.initials: J
authors.lastname: Fominaya
authors.forename: James E
authors.initials: JE
authors.lastname: Thomas
authors.forename: Amancio
authors.initials: A
authors.lastname: Carnero
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D058534:Class I Phosphatidylinositol 3-Kinases; D003114:Colony-Forming Units Assay; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology*; D007527:Isoenzymes; D019814:Myristic Acid / Q000737:chemistry / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D053148:Caspase 3; D020169:Caspases; D058534:Class I Phosphatidylinositol 3-Kinases; D007527:Isoenzymes; D019814:Myristic Acid; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D016271:Proto-Oncogene Proteins c-myc; C488371:p110delta protein, rat; C494920:Akt1 protein, rat; C505410:Casp3 protein, rat