Johnson J A, Adak S, Mochly-Rosen D
Department of Molecular Pharmacology, Stanford University School of Medicine, CA 94305-5332, USA.
Life Sci. 1995;57(11):1027-38. doi: 10.1016/0024-3205(95)02048-n.
We have determined the effects of chronic exposure to the protein kinase C (PKC) activating drug 4-beta phorbol 12-myristate-13-acetate (PMA) on PKC isozymes and the rate of spontaneous contraction in neonatal rat cardiac myocytes in culture. Western blot analyses revealed that a two day exposure to 0.1-1 nM PMA increased the total amount of delta PKC, whereas, 100 nM PMA concentrations caused a complete down-regulation of the alpha PKC and an 80 kDa zeta PKC-like protein. In addition, 100 nM PMA treatment for 2 days did not result in complete down-regulation of the beta, delta, and epsilon PKC isozymes in Western blot and immunocytochemical studies. We also found a PKC-mediated enhancement of the rate of contraction in these cells following prolonged exposure to PMA (1-100nM). Our studies suggest that this enhancement of contraction rate may be mediated by the beta, delta, or epsilon PKC isozymes. A better understanding of the role(s) of PKC isozymes in the modulation of cardiac functions may reveal selective targets for therapies of cardiac disorders.
我们已经确定了长期暴露于蛋白激酶C（PKC）激活药物4-β佛波醇12-肉豆蔻酸酯-13-乙酸酯（PMA）对培养的新生大鼠心肌细胞中PKC同工酶和自发收缩速率的影响。蛋白质免疫印迹分析显示，暴露于0.1 - 1 nM PMA两天会增加δ-PKC的总量，而100 nM PMA浓度会导致α-PKC和一种80 kDa类ζ-PKC蛋白完全下调。此外，在蛋白质免疫印迹和免疫细胞化学研究中，100 nM PMA处理2天并未导致β、δ和ε-PKC同工酶完全下调。我们还发现，在长时间暴露于PMA（1 - 100 nM）后，这些细胞中PKC介导了收缩速率的增强。我们的研究表明，这种收缩速率的增强可能由β、δ或ε-PKC同工酶介导。更好地理解PKC同工酶在心脏功能调节中的作用可能会揭示心脏疾病治疗的选择性靶点。
