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Study on multimolecular modulations of ATP-sensitive K^+ channels in pancreatic β-cells and their disharmony in diabetes.

胰腺β细胞ATP敏感K^+通道的多分子调节及其在糖尿病中的不和谐研究。

基本信息

批准号：
14571083
负责人：
KAKEI Masafumi
金额：
$ 2.5万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14571083/
关键词：
insulin secretion K-ATP channels sulfonylureas membrane phospholipid β-cells receptor operation ATP diabetes mellitus

项目摘要

ATP-sensitive K^+ (KATP) channels, composed of heteromultimers of sulfonylurea-receptor unit and a pore unit of inwardly rectifying K^+ channels, were studied with respect to effects of intracellular Ca^<2+> activity of the channels. It was found that elevation of intracellular Ca^<2+> conferred inhibition of functional transduction between binding of sulfonylureas to their receptors and closure of channels. Exposure of membrane patches to PIP_2 increased activity of KATP channels in association with reduction of ATP sensitivity of the channels. When measured membrane PIP_2 concentration by means of GFP (green fluorescent protein) labeled PH-domain contained probe, membrane fraction of GFP intensity decreased on exposure of β-cells to acetylcholine. The ATP sensitivity of the channel recorded in the presence of acetylcholine in the pipette in inside-out mode was increased as compared to that in control pipette solution. Acetylcholine, when it was applied to β-cell during cell-attached patch experiments, induced action currents. In whole-cell current recorded by nystatin-perforated mode, acetylcholine decreased the KATP channel currents at the glucose concentration of 2.8 mM. From these results, it is suggested that receptor-stimulation of pancreatic β-cells produces reduction of activity of the KATP channels associated with depolarization of membrane and an increase in output of insulin secretion around threshold concentrations of glucose. It is needed to further explore whether β-cells from diabetic animals have the inability of acetylcholine to depolarize the membrane and resultant perturbation of insulin secretion during parasympathetic neural stimulation.

研究了由磺酰脲受体单元的异多聚体和内向整流K^+通道的孔单元组成的ATP敏感性K^+(KATP)通道对通道的细胞内Ca^2+活性的影响。发现细胞内Ca 2+ 的升高抑制了磺酰脲类与其受体结合和通道关闭之间的功能转导。将膜片暴露于 PIP_2 会增加 KATP 通道的活性，同时降低通道的 ATP 敏感性。当通过 GFP（绿色荧光蛋白）标记的包含 PH 结构域的探针测量膜 PIP_2 浓度时，当 β 细胞暴露于乙酰胆碱时，GFP 强度的膜部分降低。与对照移液管溶液相比，在移液管中存在乙酰胆碱的情况下以由内向外模式记录的通道的 ATP 敏感性增加。在细胞贴附贴片实验中将乙酰胆碱应用于 β 细胞时，会诱导动作电流。在制霉菌素穿孔模式记录的全细胞电流中，乙酰胆碱在葡萄糖浓度为 2.8 mM 时降低了 KATP 通道电流。从这些结果表明，胰腺β细胞的受体刺激导致与膜去极化相关的KATP通道活性降低，并在葡萄糖阈值浓度附近增加胰岛素分泌的输出。需要进一步探讨糖尿病动物的β细胞是否无法接受乙酰胆碱使细胞膜去极化，从而在副交感神经刺激过程中扰乱胰岛素分泌。