Insulin activates ATP-sensitive K+ channels in pancreatic β-cells through a phosphatidylinositol 3-kinase-dependent pathway
Insulin activates ATP-sensitive K+ channels in pancreatic β-cells through a phosphatidylinositol 3-kinase-dependent pathway
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DOI：
10.2337/diabetes.50.10.2192
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发表时间：
2001-10-01
期刊：
影响因子：
7.7
通讯作者：
Satin, LS
中科院分区：
文献类型：
--
作者：
Khan, FA;Goforth, PB;Satin, LS
已知胰岛素通过激活细胞表面胰岛素受体、胰岛素受体底物(IRS)-1和-2的磷酸化以及磷脂酰肌醇（PI） 3-激酶的激活来调节胰腺β细胞的功能。然而，胰岛素在调节β细胞电活动及其潜在离子电流中的急性作用尚未报道。使用穿孔膜片钳技术，我们发现胰岛素（1-600 nmol/l）而不是IGF-1 （100 nmol/l）可逆地超极化单个小鼠β细胞并抑制其电活动。胰岛素的剂量-反应关系显示，膜电位的最大变化（平均+/- SE）为-13.6 +/- 2.0 mV (P < 0.001)， 50%有效剂量为25.9 +/- 0.1 nmol/l （n = 63）。将完整胰岛内的补丁β细胞暴露于200 nmol/l胰岛素中也产生了类似的结果，胰岛从-47.7 +/- 3.3到-65.6 +/- 3.7 mV的超极化（P < 0.0001, n = 11）。在单个细胞中，胰岛素诱导的超极化与全细胞电导从0.6 +/- 0.1到1.7 +/- 0.2 nS增加三倍（P < 0.001, n = 10）以及电流逆转电位从-25.7 +/- 2.5到-63.7 +/- 1.0 mV的变化相关（与对照组相比，P < 0.001, n = 9；计算的K+平衡电位= -90 mV）。甲磺丁胺可逆转胰岛素的作用，使细胞电导降低至0.5 0.1 nS，电流逆转电位为-25.2 +/- 2.3 mV。在暴露于10 mmol/l葡萄糖的胰岛中，胰岛素诱导的p细胞超极化足以消除细胞内钙浓度（[Ca2+](i)）振荡。应用100 nmol/l wortmannin灭活胰岛素信号传导关键酶PI 3-激酶，可以逆转100 nmol/l胰岛素的作用。在细胞贴片中，单个ait敏感的K+ (K- atp)通道被沐浴胰岛素激活，随后被wortmannin抑制。因此，我们的数据表明，胰岛素激活单个小鼠胰腺β细胞和胰岛的K-ATP通道，导致膜超极化，抑制电活动，并消除[Ca2+](i)振荡。因此，我们提出在生理条件下，局部释放的胰岛素可能作为胰岛内的负反馈信号。
Insulin is known to regulate pancreatic beta -cell function through the activation of cell surface insulin receptors, phosphorylation of insulin receptor substrate (IRS)-1 and -2, and activation of phosphatidylinositol (PI) 3-kinase. However, an acute effect of insulin in modulating beta -cell electrical activity and its underlying ionic currents has not been reported. Using the perforated patch clamp technique, we found that insulin (1-600 nmol/l) but not IGF-1 (100 nmol/l) reversibly hyperpolarized single mouse beta -cells and inhibited their electrical activity. The dose-response relationship for insulin yielded a maximal change (mean +/- SE) in membrane potential of -13.6 +/- 2.0 mV (P < 0.001) and a 50% effective dose of 25.9 +/- 0.1 nmol/l (n = 63). Exposing patched beta -cells within intact islets to 200 nmol/l insulin produced similar results, hyperpolarizing islets from -47.7 +/- 3.3 to -65.6 +/- 3.7 mV (P < 0.0001, n = 11). In single cells, insulin-induced hyperpolarization was associated with a threefold increase in whole-cell conductance from 0.6 +/- 0.1 to 1.7 +/- 0.2 nS (P < 0.001, n = 10) and a shift in the current reversal potential from -25.7 +/- 2.5 to -63.7 +/- 1.0 mV (P < 0.001 vs. control, n = 9; calculated K+ equilibrium potential = -90 mV). The effects of insulin were reversed by tolbutamide, which decreased cell conductance to 0.5 0.1 nS and shifted the current reversal potential to -25.2 +/- 2.3 mV. Insulin-induced P-cell hyperpolarization was sufficient to abolish intracellular calcium concentration ([Ca2+](i)) oscillations measured in pancreatic islets exposed to 10 mmol/l glucose. The application of 100 nmol/l wortmannin to inactivate PI 3-kinase, a key enzyme in insulin signaling, was found to reverse the effects of 100 nmol/l insulin. In cell-attached patches, single AIT-sensitive K+ (K-ATP) channels were activated by bath-applied insulin and subsequently inhibited by wortmannin. Our data thus demonstrate that insulin activates the K-ATP channels of single mouse pancreatic beta -cells and islets, resulting in membrane hyperpolarization, an inhibition of electrical activity, and the abolition of [Ca2+](i) oscillations . We thus propose that locally released insulin might serve as a negative feedback signal within the islet under physiological conditions.