Ogiwara T, Negishi T, Chik C L, Ho A K
Department of Physiology, Faculty of Medicine, University of Alberta, Edmonton, Canada.
J Neurochem. 1998 Oct;71(4):1405-12. doi: 10.1046/j.1471-4159.1998.71041405.x.
In rat pinealocytes, protein kinase C (PKC) is involved in the alpha1-adrenergic-mediated potentiation of beta-adrenergic-stimulated cyclic nucleotide responses; however, the specific PKC isozyme(s) involved in the potentiation mechanism remain unknown. In the present study, we compared the effects of two PKC inhibitors, calphostin C, a specific inhibitor of PKC, and Gö6976, a selective inhibitor of PKC alpha and PKC beta1, on the adrenergic-stimulated cyclic nucleotide accumulation in rat pinealocytes. Surprisingly, Gö6976 was found to have an enhancing effect on basal cyclic GMP and isoproterenol-stimulated cyclic AMP and cyclic GMP accumulation, an effect not shared by calphostin C. Gö6976 also increased the norepinephrine- and ionomycin-induced potentiation of isoproterenol-stimulated cyclic AMP and cyclic GMP accumulation, whereas the effect of calphostin C was inhibitory. The enhancing effect of Gö6976 was abolished in the presence of isobutylmethylxanthine or zaprinast, but not rolipram, suggesting that this effect of Gö6976 may be mediated through type V or the retinal type of phosphodiesterase. Based on these observations, we propose that some of the PKC isozyme(s) inhibited by calphostin C are involved in the potentiation of beta-adrenergic-stimulated cyclic nucleotide responses and that they act by enhancing synthesis. However, PKC isozymes inhibited by Gö6976 appear to be basally active and tonically inhibit cyclic nucleotide accumulation through their stimulatory action on phosphodiesterase.
在大鼠松果体细胞中，蛋白激酶C（PKC）参与α1 - 肾上腺素能介导的β - 肾上腺素能刺激的环核苷酸反应增强；然而，参与该增强机制的具体PKC同工酶仍不清楚。在本研究中，我们比较了两种PKC抑制剂，PKC的特异性抑制剂钙泊三醇C和PKCα及PKCβ1的选择性抑制剂Gö6976，对大鼠松果体细胞中肾上腺素能刺激的环核苷酸积累的影响。令人惊讶的是，发现Gö6976对基础环鸟苷酸以及异丙肾上腺素刺激的环腺苷酸和环鸟苷酸积累有增强作用，而钙泊三醇C没有这种作用。Gö6976还增加了去甲肾上腺素和离子霉素诱导的异丙肾上腺素刺激的环腺苷酸和环鸟苷酸积累的增强作用，而钙泊三醇C的作用是抑制性的。在存在异丁基甲基黄嘌呤或扎普司特但不存在咯利普兰的情况下，Gö6976的增强作用被消除，这表明Gö6976的这种作用可能是通过V型或视网膜型磷酸二酯酶介导的。基于这些观察结果，我们提出钙泊三醇C抑制的一些PKC同工酶参与了β - 肾上腺素能刺激的环核苷酸反应的增强，并且它们通过增强合成起作用。然而，Gö6976抑制的PKC同工酶似乎具有基础活性，并通过其对磷酸二酯酶的刺激作用来持续抑制环核苷酸积累。
