Protein kinase A-dependent stimulation of exocytosis in mouse pancreatic beta-cells by glucose-dependent insulinotropic polypeptide
Protein kinase A-dependent stimulation of exocytosis in mouse pancreatic beta-cells by glucose-dependent insulinotropic polypeptide
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DOI：
10.2337/diabetes.46.4.615
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发表时间：
1997-04-01
期刊：
影响因子：
7.7
通讯作者：
Gromada, J
中科院分区：
文献类型：
--
作者：
Ding, WG;Gromada, J
通过对短期培养的小鼠胰岛β细胞的全细胞钙电流、胞浆钙离子浓度和细胞电容的测定，探讨了葡萄糖依赖型促胰岛素多肽(GIP)刺激胰岛素分泌的机制。GIP可使去极化引起的胞吐作用增强4.2倍。胞吐作用的这种刺激与全细胞钙电流的变化无关，胞浆内钙离子浓度[细胞内游离钙离子浓度([Ca~(2+)](I)])仅有轻微的增加(30%)。GIP对胞吐的刺激作用可被特异性蛋白激酶A(PKA)抑制剂RP-8-BR-cAMPS阻断。胰升糖素样多肽-I(7-36)酰胺(GLP-I)在最大浓度(100nmol/L)时刺激胞吐作用(90%)。用Forsklin替代GLP-I对胞吐作用也有类似的刺激作用。GLP-I和Forskolin在GIP存在时的这些作用不涉及全细胞钙电流或[Ca~(2+)](I)的变化。GIP在Forsklin和磷酸二酯酶抑制剂异丁基甲基黄嘌呤(IBMX)的存在下均无效。在相同的实验条件下，蛋白激酶C(PKC)激活佛波醇酯4-佛波酯12-肉豆蔻酸酯(PMA)刺激胞吐(60%)。总之，我们的数据表明，促胰岛素激素GIP通过cAMP/PKA信号通路，通过与[Ca~(2+)](I)升高远端的分泌机制相互作用，刺激胰腺p细胞的胰岛素分泌。
The mechanisms by which glucose-dependent insulinotropic polypeptide (GIP) stimulates insulin secretion were investigated by measurements of whole-cell Ca2+ currents, the cytoplasmic Ca2+ concentration, and cell capacitance as an indicator of exocytosis in individual mouse pancreatic beta-cells maintained in short-term culture. GIP produced a 4.2-fold potentiation of depolarization-induced exocytosis. This stimulation of exocytosis was not associated with a change in the whole-cell Ca2+-current, and there was only a small increase (30%) in the cytoplasmic Ca2+ concentration [intercellular free Ca2+([Ca2+](i))]. The stimulatory effect of GIP on exocytosis was blocked by pretreatment with the specific protein kinase A (PKA) inhibitor Rp-8-Br-cAMPS. Glucagon-like peptide-I (7-36) amide (GLP-I) stimulated exocytosis (90%) in the presence of a maximal GIP concentration (100 nmol/l). Replacement of GLP-I with forskolin produced a similar stimulatory action on exocytosis. These effects of GLP-I and forskolin in the presence of GIP did not involve a change in the whole-cell Ca2+-current or [Ca2+](i). GIP was ineffective in the presence of both forskolin and the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX). Under the same experimental conditions, the protein kinase C (PKC)-activating phorbol ester 4-phorbol 12-myristate 13-acetate (PMA) stimulated exocytosis (60%). Collectively, our data indicate that the insulinotropic hormone GIP stimulates insulin secretion from pancreatic p-cells, through the cAMP/PKA signaling pathway, by interacting with the secretory machinery at a level distal to an elevation in [Ca2+](i).