Structure and physiological role of ATP-sensitive potassium channel

ATP敏感性K^+（K_<ATP>）通道是连接细胞代谢状态与膜电位的关键分子。我们已经确定胰腺β细胞K_<ATP>通道由内向整流Kir6.2亚基和磺脲类受体SUR 1亚基组成。结果如下：#我们通过免疫组织化学研究发现，SUR 1不仅在胰腺β细胞中表达，而且在胰高血糖素阳性、生长激素抑制素阳性或胰腺多肽阳性细胞中也表达。虽然K_<ATP>通道在这些细胞中的生理作用尚不清楚，但这些结果表明磺酰脲类药物可能通过SUR 1对这些细胞产生一些影响。我们已经开发了一种方法，通过使用D-葡萄糖的荧光衍生物2-NBDG来测量单个活的胰腺β细胞中葡萄糖转运及其对各种细胞内功能的影响。通过使用这种新的方法，我们揭示了葡萄糖代谢以及葡萄糖摄取在葡萄糖诱导的胰腺β细胞胰岛素分泌中是关键的，从而证实了K_<ATP>通道在胰岛素分泌中的重要性。黑质网状部（substantia nigra pars reticulata，SNr）是脑内钾通道表达最高的区域<ATP>，在癫痫发作的控制中起着关键作用。我们发现K_通道Kir6.2亚基缺失的突变小鼠<ATP>（KO小鼠）在短暂缺氧后易发生全身性癫痫发作。在正常小鼠中，SNr神经元的活性在缺氧时由于突触后K_通道的开放而失活<ATP>，而在KO小鼠中，这些神经元的活性增强。这些结果提示，K_<ATP>通道通过开放对缺氧时SNr神经元的活动具有抑制作用，并参与黑质对全身性癫痫发作的保护机制。

ATP-sensitive K^+ (K_<ATP>) channels are key molecules which link the cell's metabolic status to its membrane potential. We have determined that pancreatic β -cell K_<ATP> channel comprises the inward rectifier Kir6.2 and the sulfonylurea receptor SUR1 subunits. Our results are as follows.# We have revealed by immunohistochmical study that SUR1 is expressed not only in pancreatic β -cells but also in glucagon-positive, somatostatin-positive, or pancreatic polypeptide-positive cells. Although the physiological role of the K_<ATP> channels in these cells is unknown, these results suggest that sulfonylureas may exert some effects on these cells through SUR1.# We have developed the method to measure both glucose transport and its effect on the various intracellular functions in single, living pancreatic β -cells, by using a fluorescent derivative of D-glucose, 2-NBDG. By using this novel method, we have revealed that glucose metabolism as well as glucose uptake is critical in glucoseinduced insulin secretion from pancreatic β -cells, verifying the importance of K_<ATP> channels in insulin secretion.# The substantia nigra pars reticulata (SNr), tjae area with the highest expression of K_<ATP> channels in the brain, plays a pivotal role in the control of seizures. We have shown that mutant mice lacking the Kir6.2 subunit of K_<ATP> channels (KO mice) are susceptible to generalized seizures after brief hypoxia. In normal mice, SNr neuron activity was inactivated during hypoxia by the opening of the post-synaptic K_<ATP> channels, while in KO mice the activity of these neurons was enhanced. These results suggest that K_<ATP> channels exert a depressant effect on SNr neuronal activity during hypoxia by an opening of the channels, and is involved in the nigral protection mechanism against generalized seizures.