Investigation of Molecular Diversity of ATP-Sensitive K^+ Channels.

ATP 敏感 K^ 通道的分子多样性研究。

基本信息

批准号：
09670716
负责人：
INANOBE Atsushi
金额：
$ 2.05万
依托单位：
Osaka University Faculty of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

ATP-sensitive K^+ (K_<ATP>) channels, which represent a family of K^+ channels inhibited by intracellular ATP, have been found in a variety of tissues including heart, pancreatic beta-cells, skeletal muscle, smooth muscle, and the central nervous system.These K_<ATP> channels are closely related to diverse cellular functions, such as shortening of action potential duration and cellular loss of K^+ ions that occur during metabolic inhibition in heart, insulin secretion from pancreatic beta-cells, smooth muscle relaxation, regulation of skeletal muscle excitability, and neurotransmitter release.Furthermore, other diverse factors such as NDP, pH, Mg^<2+>, polyamine, PIP_2, G proteins, K^+ channel openers and sulfonylurea also modulate the activity of K_<ATP> channels.K_<ATP> channel is composed of two kinds of membrane proteins Kir6.x and SURx.We characterized K_<ATP> channels reconstituted with various combination of subunits expressed in mammalian cell line with patch clamp techniques.The result runs as follows ; 1) The activity of K_<ATP> channel with Kir6.2 and SUR2A is almost same as that of cardiac K_<ATP> channel.2) Spontaneous openings and unitary conductances of Kir6.1 and Kir6.2 are determined with a part of each N- and C-terminus and extracellular linker domain between the two putative membrane-spanning regions, respectively.3) Splicing isoforms of SUR2A and SUR2B which are divergent at C terminus have different sensitivities to both K^+ channel openers and sulfonylurea.4) Although SUR subunits contain the critical binding sites for K^+ channel openers and intracellular nucleotides, the Kir subunits seem to influence the way in which the entire SUR/Kir functional channel complex reacts to these compounds.

ATP 敏感 K^+ (K_<ATP>) 通道代表受细胞内 ATP 抑制的 K^+ 通道家族，已在多种组织中发现，包括心脏、胰腺 β 细胞、骨骼肌、平滑肌、这些 K_<ATP> 通道与多种细胞功能密切相关，例如心脏代谢抑制期间发生的动作电位持续时间缩短和 K^+ 离子的细胞损失、胰腺 β 细胞分泌胰岛素, 平滑肌松弛、骨骼肌兴奋性调节和神经递质释放。此外，其他多种因素如 NDP、pH、Mg^<2+>、多胺、PIP_2、G 蛋白、K^+ 通道开放剂和磺酰脲类也调节 K_ 的活性<ATP> 通道。K_<ATP> 通道由两种膜蛋白 Kir6.x 和 SURx 组成。我们表征了用各种组合重组的 K_<ATP> 通道采用膜片钳技术在哺乳动物细胞系中表达亚基。结果如下： 1) Kir6.2 和 SUR2A 的 K_<ATP> 通道活性与心脏 K_<ATP> 通道的活性几乎相同。2) Kir6.1 和 Kir6.2 的自发开口和酉电导由部分确定分别是两个假定的跨膜区域之间的每个 N 端和 C 端以及胞外连接结构域。 3) SUR2A 和 SUR2B 的剪接亚型C 末端的分歧对 K^+ 通道开放剂和磺酰脲具有不同的敏感性。4) 尽管 SUR 亚基包含 K^+ 通道开放剂和细胞内核苷酸的关键结合位点，但 Kir 亚基似乎影响整个 SUR 的方式/Kir 功能通道复合物与这些化合物发生反应。