title: PKC-ι promotes glioblastoma cell survival by phosphorylating and inhibiting BAD through a phosphatidylinositol 3-kinase pathway.
abstract: The focus of this research was to investigate the role of protein kinase C-iota (PKC-ι) in regulation of Bad, a pro-apoptotic BH3-only molecule of the Bcl-2 family in glioblastoma. Robust expression of PKC-ι is a hallmark of human glioma and benign and malignant meningiomas. The results were obtained from the two human glial tumor derived cell lines, T98G and U87MG. In these cells, PKC-ι co-localized and directly associated with Bad, as shown by immunofluorescence, immunoprecipitation, and Western blotting. Furthermore, in-vitro kinase activity assay showed that PKC-ι directly phosphorylated Bad at phospho specific residues, Ser-112, Ser-136 and Ser-155 which in turn induced inactivation of Bad and disruption of Bad/Bcl-XL dimer. Knockdown of PKC-ι by siRNA exhibited a corresponding reduction in Bad phosphorylation suggesting that PKC-ι may be a Bad kinase. PKC-ι knockdown also induced apoptosis in both the cell lines. Since, PKC-ι is an essential downstream mediator of the PI (3)-kinase, we hypothesize that glioma cell survival is mediated via a PI (3)-kinase/PDK1/PKC-ι/Bad pathway. Treatment with PI (3)-kinase inhibitors Wortmannin and LY294002, as well as PDK1 siRNA, inhibited PKC-ι activity and subsequent phosphorylation of Bad suggesting that PKC-ι regulates the activity of Bad in a PI (3)-kinase dependent manner. Thus, our data suggest that glioma cell survival occurs through a novel PI (3)-kinase/PDK1/PKC-ι/BAD mediated pathway.
authors.affiliation: James A. Haley Veteran's Hospital, Tampa, FL 33612, USA.
authors.forename: S
authors.initials: S
authors.lastname: Desai
authors.forename: P
authors.initials: P
authors.lastname: Pillai
authors.forename: H
authors.initials: H
authors.lastname: Win-Piazza
authors.forename: M
authors.initials: M
authors.lastname: Acevedo-Duncan
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006801:Humans; D047468:Immunoprecipitation; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D034622:RNA Interference; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D000077191:Wortmannin; D051025:bcl-Associated Death Protein / Q000737:chemistry / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism; D000099293:Protein Kinase C-lambda
chemical_list: D048948:14-3-3 Proteins; D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D012694:Serine; D000077191:Wortmannin; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D000099293:Protein Kinase C-lambda; C494819:BAD protein, human; C000631429:PDK1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one