Protein kinase Cε modulates apoptosis induced by β-adrenergic stimulation in adult rat ventricular myocytes via extracellular signal-regulated kinase (ERK) activity

beta -Adrenergic stimulation of ventricular myocytes has been shown to induce apoptosis: however, the cellular mechanisms involved in this pathway have not been completely characterized. This study examines the role of protein kinase C (PKC) in the signaling cascade that mediates beta -adrenergic stimulation-induced apoptosis. Stimulation of beta -adrenergic receptors using isoproterenol (ISO, 1-10 muM. 24 h) induced apoptosis in cultured adult rat ventricular myocytes (ARVM) in a dose-dependent manner, Treatment with ISO significantly resulted in the membrane translocation of PKC epsilon, but not of PKC alpha or delta in ARVM. The activation of PKC epsilon by ISO was confirmed using an immune complex kinase assay. To address whether PKC epsilon is involved in the mechanism of ISO-induced apoptosis. we used the PKC epsilon -specific translocation inhibitor peptide. epsilon V1-2. Peptide epsilon V1-2 significantly blocked the translocation of PKC epsilon, as well as the enzymatic action of PKC epsilon, resulting from ISO stimulation. The inhibition of PKC epsilon attenuated ISO-induced apoptosis as measured by terminal deoxynucleotidyltransferase nick-end labeling (TUNEL) assay (18.2 +/- 3.8% v 49.0 +/- 2.4%; P<0.05), while a PKC-specific peptide translocation inhibitor ((delta V1-1) failed to do so (39.8 +/- 7.8%). In the presence of ISO, PKC epsilon inhibition by epsilon V1-2 was found to significantly enhance activity of ERK, but not that of Akt/PKB. Inhibition of ERK activation by PD 98059 (10-50 muM) attenuated the epsilon V1-2 peptide-mediated anti-apoptotic effect, thus suggesting that ERK activation is involved in this anti-apoptotic effect. Therefore, our results suggest that activation of PKC epsilon downstream of beta -adrenergic stimulation promotes apoptosis largely via inhibition of an ERK activation-dependent anti-apoptotic effect. (C) 2001 Academic Press.