Oda T, Shearman M S, Nishizuka Y
Department of Biochemistry, Kobe University School of Medicine, Japan.
J Neurochem. 1991 Apr;56(4):1263-9. doi: 10.1111/j.1471-4159.1991.tb11420.x.
The effect of phorbol esters was investigated on the down-regulation of protein kinase C (PKC) and on the release of [3H]norepinephrine (NE) in synaptosomes from the rat cerebrum. Treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) promoted the translocation of PKC activity in a P2 fraction from the cytosol to the membrane fraction and then its down-regulation, in a dose-dependent manner. TPA induced a rapid down-regulation of the type II(beta) and type III(alpha) subspecies, but did not change the activity of the type I(gamma) subspecies in the cytosolic fraction for at least 15 min. The gamma-subspecies was subsequently decreased at a slower rate. In the synaptosomes thus having only the gamma-subspecies, a subsequent dose of TPA could not enhance K(+)-evoked NE release, although, in the original synaptosomes, TPA was able to enhance K(+)-evoked NE release. Pretreatment with TPA did not alter the K(+)-evoked NE release itself. TPA was also found to enhance the K(+)-evoked NE release from synaptosomes prepared from both hippocampus, which express the gamma-subspecies of PKC at a negligible level, and cerebral cortex, which have a significant level of the gamma-subspecies, to the same degree. These results suggest that the gamma-subspecies of PKC does not participate in the TPA-enhanced K(+)-evoked NE release from synaptosomes.
研究了佛波酯对大鼠大脑突触体中蛋白激酶C（PKC）下调及[3H]去甲肾上腺素（NE）释放的影响。用12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）处理可促进PKC活性在P2组分中从胞质溶胶向膜组分的转位，然后呈剂量依赖性地下调。TPA诱导II（β）型和III（α）型亚型快速下调，但在至少15分钟内不会改变胞质溶胶组分中I（γ）型亚型的活性。随后γ亚型以较慢的速率下降。在仅具有γ亚型的突触体中，后续剂量的TPA不能增强K⁺诱发的NE释放，尽管在原始突触体中，TPA能够增强K⁺诱发的NE释放。用TPA预处理不会改变K⁺诱发的NE释放本身。还发现TPA能同等程度地增强从海马体（PKC的γ亚型表达水平可忽略不计）和大脑皮层（γ亚型水平显著）制备的突触体中K⁺诱发的NE释放。这些结果表明，PKC的γ亚型不参与TPA增强的突触体中K⁺诱发的NE释放。
