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pubmed:abstractText |
The focus of this research was to investigate the role of protein kinase C-iota (PKC-?) in regulation of Bad, a pro-apoptotic BH3-only molecule of the Bcl-2 family in glioblastoma. Robust expression of PKC-? 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-? co-localized and directly associated with Bad, as shown by immunofluorescence, immunoprecipitation, and Western blotting. Furthermore, in-vitro kinase activity assay showed that PKC-? 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-? by siRNA exhibited a corresponding reduction in Bad phosphorylation suggesting that PKC-? may be a Bad kinase. PKC-? knockdown also induced apoptosis in both the cell lines. Since, PKC-? 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-?/Bad pathway. Treatment with PI (3)-kinase inhibitors Wortmannin and LY294002, as well as PDK1 siRNA, inhibited PKC-? activity and subsequent phosphorylation of Bad suggesting that PKC-? 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-?/BAD mediated pathway.
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