Calcium influx activates adenylyl cyclase 8 for sustained insulin secretion in rat pancreatic beta cells
Calcium influx activates adenylyl cyclase 8 for sustained insulin secretion in rat pancreatic beta cells
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钙流入激活腺苷酸环化酶 8，维持大鼠胰腺 β 细胞持续分泌胰岛素
DOI：
10.1007/s00125-014-3437-z
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发表时间：
2015-02-01
期刊：
影响因子：
8.2
通讯作者：
Zhou, Zhuan
中科院分区：
文献类型：
--
作者：
Dou, Haiqiang;Wang, Changhe;Zhou, Zhuan
目的/假设胰岛素是健康和糖尿病的关键代谢调节剂。在胰腺 β 细胞中，胰岛素释放受主要第二信使 Ca2+ 和 cAMP 调节：胞吐作用由 Ca2+ 触发并由 cAMP/蛋白激酶 A (PKA) 信号通路介导。然而，原代β细胞中这两个过程之间的因果关系仍未明确。方法进行荧光共振能量转移信号的时间分辨共聚焦成像以可视化PKA活性，并使用组合膜电容记录来监测膜片钳大鼠β细胞的胰岛素分泌。结果膜去极化诱导的Ca2+流入通过激活Ca2+敏感的腺苷酸环化酶8（ADCY8）导致胞质PKA活性增加子池。葡萄糖刺激触发耦合 Ca2+ 振荡和 PKA 激活。 ADCY8 敲低显着降低了去极化诱发的 PKA 激活水平，并损害了易于释放的囊泡库的补充。两种抑制剂对 PKA 的药理学抑制可在相似程度上减少去极化诱导的 PKA 激活，并降低持续囊泡胞吐作用和胰岛素释放的能力。结论/解释我们的研究结果表明，去极化诱导的 Ca2+ 内流通过触发囊泡融合和补充囊泡池以支持持续的胰岛素释放，在调节大鼠胰腺 β 细胞的胞吐作用中发挥双重作用。因此，Ca2+流入可能对葡萄糖刺激的胰岛素分泌很重要。
Aims/hypothesisInsulin is a key metabolic regulator in health and diabetes. In pancreatic beta cells, insulin release is regulated by the major second messengers Ca2+and cAMP: exocytosis is triggered by Ca2+and mediated by the cAMP/protein kinase A (PKA) signalling pathway. However, the causal link between these two processes in primary beta cells remains undefined.MethodsTime-resolved confocal imaging of fluorescence resonance energy transfer signals was performed to visualise PKA activity, and combined membrane capacitance recordings were used to monitor insulin secretion from patch-clamped rat beta cells.ResultsMembrane depolarisation-induced Ca2+influx caused an increase in cytosolic PKA activity via activating a Ca2+-sensitive adenylyl cyclase 8 (ADCY8) subpool. Glucose stimulation triggered coupled Ca2+oscillations and PKA activation. ADCY8 knockdown significantly reduced the level of depolarisation-evoked PKA activation and impaired replenishment of the readily releasable vesicle pool. Pharmacological inhibition of PKA by two inhibitors reduced depolarisation-induced PKA activation to a similar extent and reduced the capacity for sustained vesicle exocytosis and insulin release.Conclusions/interpretationOur findings suggest that depolarisation-induced Ca2+influx plays dual roles in regulating exocytosis in rat pancreatic beta cells by triggering vesicle fusion and replenishing the vesicle pool to support sustained insulin release. Therefore, Ca2+influx may be important for glucose-stimulated insulin secretion.