Effect of PKCα expression on Bcl-2 phosphorylation and cell death by hypericin
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In order to explain the contribution of the protein kinase Cα (PKCα) in apoptosis induced by photo-activation of hypericin (Hyp), a small interfering RNA was used for post-transcriptional silencing of pkcα gene expression. We have evaluated the influence of Hyp photo-activation on cell death in non-transfected and transfected (PKCα−) human glioma cells (U-87 MG). No significant differences were detected in cell survival between non-transfected and transfected PKCα− cells. However, the type of cell death was notably affected by silencing the pkcα gene. Photo-activation of Hyp strongly induced apoptosis in non-transfected cells, but the level of necrotic cells in transfected PKCα− cells increased significantly. The differences in cell death after Hyp photo-activation are demonstrated by changes in: (i) reactive oxygen species production, (ii) Bcl-2 phosphorylation on Ser70 (pBcl-2(Ser70)), (iii) cellular distributions of pBcl-2(Ser70) and (iv) cellular distribution of endogenous anti-oxidant glutathione and its co-localization with mitochondria. In summary, we suggest that post-transcriptional silencing of the pkcα gene and the related decrease of PKCα level considerably affects the anti-apoptotic function and the anti-oxidant function of Bcl-2. This implies that PKCα, as Bcl-2 kinase, indirectly protects U-87 MG cells against oxidative stress and subsequent cell death.
KeywordsHypericin PKCα Bcl-2 Apoptosis Necrosis Mitochondria ROS GSH
This work was supported by: the FP7 EU project CELIM 316310, the project of the Slovak Res. and Dev. Agency APVV-0242-11, the project of the Agency of the Ministry of Education of Slovak (Republic for the Structural funds of the European Union: Doktorand (ITMS code: 26110230013) and KVARK (ITMS code: 26110230084) and by the International Program for Scientific Cooperation (PICS N°5398) from the CNRS. This work forms a part of the co-tutoring doctoral study of J. J. (P. J. Safarik University and UPMC).
Conflict of interest
The authors declare that they have no conflict of interest.
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