蛋白激酶C在正常小鼠胰腺β细胞中通过血管加压素和乙酰胆碱受体进行信号转导中的作用。

The role of protein kinase-C in signal transduction through vasopressin and acetylcholine receptors in pancreatic B-cells from normal mouse.

作者信息

Gao Z Y, Gilon P, Henquin J C

机构信息

Unité d'Endocrinologie et Métabolisme, Faculty of Medicine, University of Louvain, Brussels, Belgium.

出版信息

Endocrinology. 1994 Jul;135(1):191-9. doi: 10.1210/endo.135.1.8013353.

DOI:10.1210/endo.135.1.8013353

PMID:8013353

Abstract

The role of protein kinase-C (PKC) in the potentiation of insulin release by arginine vasopressin (AVP) and acetylcholine (ACh) was investigated with normal mouse islets. The islets were submitted to a short term (30-min) or long term (22-h) treatment with phorbol 12-myristate 13-acetate (PMA) to stimulate acutely or down-regulate PKC before being stimulated by AVP or ACh. Control islets were treated with the inactive 4 alpha-phorbol 12,13-didecanoate. In the presence of 15 mM glucose and 2.5 mM Ca2+, AVP and ACh stimulated inositol phosphate (IP) formation, increased cytoplasmic Ca2+ (Cai2+), and potentiated insulin release. These effects were greater with ACh than with AVP, in particular on Cai2+, which was scarcely affected by AVP. In the absence of extracellular Ca2+, only ACh induced a short-lived increase in Cai2+ and insulin. Acute treatment with PMA in the presence of extracellular Ca2+ strongly increased insulin release in spite of a marked lowering of Cai2+. Under these conditions, the effects of AVP and ACh on IP production and Cai2+ were practically abolished, and only ACh transiently increased insulin release. In the absence of Ca2+, the small mobilization of Cai2+ by ACh triggered a peak of insulin, whereas a similar mobilization of Cai2+ by AVP was ineffective on insulin. After long term treatment of the islets with PMA, AVP normally increased IP formation, but did not affect insulin release. The effect of ACh on IP was still inhibited. However, ACh produced a marked transient increase in Cai2+, with a small transient release of insulin. The releasing effect of ACh was also inhibited in the absence of Ca2+. In conclusion, PKC plays a dual role in the B-cell responses to ACh and AVP. Its activation is necessary for the sustained potentiation of insulin release that both agents produce. This effect probably results from a sensitization of the secretory machinery to Cai2+, the triggering signal. PKC also exerts a negative feedback control on the signal transduction mechanisms involving phospholipase-C, but the ACh and AVP responses are not equally affected by this feedback.

摘要

利用正常小鼠胰岛研究了蛋白激酶 C（PKC）在精氨酸加压素（AVP）和乙酰胆碱（ACh）增强胰岛素释放过程中的作用。在用 AVP 或 ACh 刺激之前，将胰岛用佛波醇 12 - 肉豆蔻酸酯 13 - 乙酸酯（PMA）进行短期（30 分钟）或长期（22 小时）处理，以急性刺激或下调 PKC。对照胰岛用无活性的 4α - 佛波醇 12,13 - 二癸酸酯处理。在 15 mM 葡萄糖和 2.5 mM Ca²⁺存在的情况下，AVP 和 ACh 刺激肌醇磷酸（IP）形成，增加细胞质 Ca²⁺（Cai²⁺），并增强胰岛素释放。这些作用 ACh 比 AVP 更强，特别是对 Cai²⁺的影响，AVP 对其影响很小。在无细胞外 Ca²⁺的情况下，只有 ACh 诱导 Cai²⁺和胰岛素短暂增加。在细胞外 Ca²⁺存在的情况下，用 PMA 急性处理尽管 Cai²⁺明显降低，但仍强烈增加胰岛素释放。在这些条件下，AVP 和 ACh 对 IP 产生和 Cai²⁺的作用实际上被消除，只有 ACh 短暂增加胰岛素释放。在无 Ca²⁺的情况下，ACh 引起的 Cai²⁺小幅度动员引发胰岛素峰值，而 AVP 引起的类似 Cai²⁺动员对胰岛素无效。在用 PMA 对胰岛进行长期处理后，AVP 正常增加 IP 形成，但不影响胰岛素释放。ACh 对 IP 的作用仍然受到抑制。然而，ACh 使 Cai²⁺产生明显的短暂增加，并伴有少量胰岛素短暂释放。在无 Ca²⁺的情况下，ACh 的释放作用也受到抑制。总之，PKC 在 B 细胞对 ACh 和 AVP 的反应中起双重作用。其激活对于这两种物质产生的胰岛素释放的持续增强是必要的。这种作用可能是由于分泌机制对触发信号 Cai²⁺的敏感性增加所致。PKC 还对涉及磷脂酶 C 的信号转导机制施加负反馈控制，但 ACh 和 AVP 的反应受该反馈的影响并不相同。