Reversible Ca2+-dependent translocation of protein kinase C and glucose-induced insulin release
Reversible Ca2+-dependent translocation of protein kinase C and glucose-induced insulin release
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DOI：
10.1074/jbc.271.30.18154
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发表时间：
1996-07-26
影响因子：
4.8
通讯作者：
Berggren, PO
中科院分区：
文献类型：
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作者：
Deeney, JT;Cunningham, BA;Berggren, PO
据报道，蛋白激酶 C (PKC) 在 β 细胞刺激-分泌耦合中的多个位点相互作用，然而，关于该酶在葡萄糖诱导的胰岛素释放中的重要性仍存在争议。本研究的目的是澄清葡萄糖是否直接或通过改变细胞质游离 Ca2+ 浓度 [Ca2+](i) 可以促进 PKC 从可溶性到膜区室的易位，而增加 [Ca2+](i) 的葡萄糖并不影响PKC 活性在可溶性组分和膜组分之间的长期分布，这种分布受到提取介质中 Ca2+ 浓度的可逆性严重影响，在 20 nM 佛波酯 12-O-十四烷酰佛波醇-13-乙酸酯 (TPA) 存在的情况下，将 HIT 细胞孵育 10 分钟，将 PKC 转移到膜上，导致葡萄糖诱导的胰岛素释放增加 5 倍，50 nM 浓度可以防止这种情况发生PKC 抑制剂星形孢菌素，前提是细胞在佛波酯之前暴露于抑制剂，用 TPA 预处理的细胞显示出响应葡萄糖的胰岛素分泌增加几个小时，这个时间过程延长到 [H-3] TPA 从细胞中消失，1 小时后完成，PKC 的激活使平均胰岛素释放和振荡幅度增加了一倍，但不影响振荡频率，PKC 活性增加的刺激作用胰岛素释放与 [Ca2+](i) 的变化不匹配。我们认为，用葡萄糖刺激胰腺 β 细胞会促进某些 PKC 亚型从细胞质瞬时易位到质膜，这是 [Ca2+](i) 增加的直接结果。这种易位可能会促进参与调节 β 细胞刺激-分泌耦合的一种或多种蛋白质的磷酸化，这会导致葡萄糖诱导的胰岛素胞吐作用激活增强，而这种作用并非由 [Ca2+](i) 本身的增加介导，因此，在总体 [Ca2+](i) 不发生变化的条件下可以获得脉冲式胰岛素释放，挑战了 [Ca2+](i) 振荡确实驱动振荡的观点在激素释放中。
It has been reported that protein kinase C (PKC) interacts at multiple sites in beta-cell stimulus-secretion coupling, Nevertheless, there is still controversy concerning the importance of this enzyme in glucose-induced insulin release, The present study was undertaken to clarify whether glucose, directly, or through changes in cytoplasmic free Ca2+ concentration, [Ca2+](i), could promote translocation of PKC from the soluble to the membrane compartment, Whereas glucose, which increases [Ca2+](i), did not affect long-term distribution of PKC activity between soluble and membrane fractions, this distribution was reversibly affected acutely by the Ca2+ concentration in the extraction media, Translocation of PKC to the membrane by incubation of HIT cells for 10 min in the presence of 20 nM phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a 5-fold increase in glucose-induced insulin release, This was prevented by 50 nM concentration of the PKC inhibitor staurosporine, provided that the cells were exposed to the inhibitor before the phorbol ester, Cells pretreated with TPA demonstrated increased insulin secretion in response to glucose for several hours, This time course extended beyond the disappearance of [H-3] TPA from the cells, which was complete after 1 h, Activation of PKC increased both average insulin release and the amplitude of oscillations a-fold, but did not affect oscillation frequency, The stimulatory effect of increased PKC activity on insulin release was not matched by changes in [Ca2+](i), We suggest that stimulation of the pancreatic beta-cell with glucose promotes transient translocation of certain PKC isoforms from the cytoplasm to the plasma membrane as a direct consequence of the increase in [Ca2+](i). Such a translocation may promote phosphorylation of one or several proteins involved in the regulation of the beta-cell stimulus-secretion coupling, This results in potentiation of glucose-induced activation of insulin exocytosis, an effect then not mediated by an increase in [Ca2+](i) per se, Hence, pulsatile insulin release can be obtained under conditions where overall [Ca2+](i) does not change, challenging the view that oscillations in [Ca2+](i) are indeed driving the oscillations in hormone release.