Distinct regulation of p53-mediated apoptosis by protein kinase calpha, delta, epsilon and zeta: evidence in yeast for transcription-dependent and -independent p53 apoptotic mechanisms

The role of individual protein kinase C (PKC) isoforms in the regulation of p53- mediated apoptosis is still uncertain. Using yeast cells co-expressing the human wild-type p53 and a single mammalian PKCa, d, e or z, we showed a differential regulation of p53- mediated apoptosis by these PKC isoforms. Whereas PKCa and z had no effect on p53 activity, PKCd and e stimulated a p53-mediated mitochondria-dependent apoptosis. Moreover, using pifithrin-a and -m, selective inhibitors of p53 transcriptional activity and mitochondrial p53 translocation, respectively, we showed the activation of a transcriptiondependent and -independent p53-mediated apoptosis by PKCd and e. The activation of mitochondrial p53 translocation by PKCd and e was further confirmed by immunofluorescence and Western blot analysis. Together, this work reveals the conservation in yeast of functional transcriptiondependent and -independent p53 apoptotic mechanisms. Furthermore, it gives mechanistic insights about the regulation of p53-mediated apoptosis by PKCd and e through modulation of p53 transcriptional activity and of its translocation to mitochondria. Finally, it underscores a major role of PKCd and e as positive regulators of p53-mediated apoptosis, and therefore as promising therapeutic targets in cancer.REQUIMTE/CEQUP, FCT (I&D No 8/94; PTDC/ SAU-FAR/110848/2009), POCTI (QCA III), FEDER and U.Porto/ Santander Totta. I. Coutinho is recipient of a PhD fellowship from FCT (SFRH/BD/36066/2007). C. Pereira is recipient of a Post-Doctoral fellowship from FCT (SFRH/BPD/44209/2008)