Study of intracellular modulation mechanisms of cardiac ATP-sensitive K^+ channels and their pathophysiological implications.

心脏 ATP 敏感 K^ 通道的细胞内调节机制及其病理生理学意义的研究。

• 批准号: 07457165
• 负责人: HIRAOKA Masayasu
• 金额: $ 4.54万
• 依托单位: Tokyo Medical and Dental University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07457165/
• 关键词: ATP-sensitive K^+ channel; rundown of the channel activity; intracellular ATP; ADP; actin cytoskeleton; adenosine; protein kinase C; プロティン・カイネース; ATPk感受性Kチャネル; 細胞内活性化因子; チャネル活性の失活(rundown); ATPの加水分解; 再活性化; アクチン細胞骨格

The ATP-sensitive K^+ channels (K_<ATP>) are characterized by a strong inhibition by [ATP]_I but ATP is also necessary for the channels in an operative states. There are numerous factors to modulate the channel functions, which are difficult to attribute to real role for their openings during myocardial ischemia. We previously demonstrated that reactivation of after rundown by MgATP was caused by hydrolysis. Since ATP hydrolysis is also utilized in the process of actin cytoskeletal assembly, we examined the linkage between the K_<ATP> activity and the status of actin polymerization. Application of actin disrupters induced quick rundown. Actin stabilizers restored the channel activity in partially rundown channels, while they were ineffective in complete rundown or fully activated channels. MgATP plus F-actin restored the completely rundown channels. Therefore, the assembly and disassembly of actin cytoskeleton play a modulatory role for K_<ATP> Next, we examined whether or not K_<ATP> … More could be opened in the presence of milimor order of [ATP]_I. Using the trypsin-treated patches which showed least rundown, the presence of ADP plus Mg^<2+>, low pH increased the channel open probability in the presence of 1-2 mM [ATP]_I. From these results, we can conclude that K_<ATP> will be opened during early phase of myocardial ischemia where cellular ATP levels do not drop dramatically. This openings can be achieved with the presence of co-factors such as ADP and low pH,which are associated with ischemia. Another ischemic product, adenosine, is supposed to be an activator of K_<ATP> during myocardial ischemis, but its actual contribution in the whole-cell condition has not been demonstrated. We used a nystatin-perforated method which did not disturb the cellular condition. Using this technique, adenosine was shown to shorten K_<ATP> openings during metabolic inhibition, which was mediated through A2-receptor stimulation. The activation of PKC was also involved the K_<ATP> openings, but adenosine and PKC did not work synergistically as reported by the other groups. The intracellular mechanism between A2-receptor and PKC activation is under the extensive investigation. Less

对ATP敏感的K~+通道(K_&lt；ATP&gt；)具有被[ATP]_i强烈抑制的特点，但对处于工作状态的K~+通道也是必需的。调节通道功能的因素很多，但很难将其在心肌缺血时开放的真正作用归因于这些因素。我们以前曾证明，镁三磷酸腺苷对After Rundown的重新激活是由水解引起的。由于在肌动蛋白细胞骨架组装过程中也利用了ATP水解酶，因此我们研究了K_lt；ATP&>活性和肌动蛋白聚合状态之间的联系。应用肌动蛋白干扰物可导致快速衰弱。肌动蛋白稳定剂在部分收缩通道中恢复通道活动，而在完全收缩或完全激活的通道中无效。镁-三磷酸腺苷加F-肌动蛋白使通道完全恢复。因此，肌动蛋白细胞骨架的组装和拆解对K；…起着调制作用。接下来，我们考察了K；当[ATP]_I浓度为1~2 mM时，胰酶处理的心肌细胞膜片可开放更多的通道，而ADP+Mg~(2+)和低pH值可使通道开放概率增加，说明心肌缺血早期，细胞内ATP水平不会显著下降。这种开放可以在与缺血相关的辅助因素如ADP和低pH值的存在下实现。另一种缺血产物，腺苷，被认为是心肌缺血时K_&lt；ATP和Gt；的激活剂，但其在全细胞条件下的实际作用尚未得到证实。我们使用了制霉菌素穿孔方法，这种方法不会干扰细胞条件。利用这一技术，腺苷被证明在代谢抑制期间缩短K&lt；ATP&Gt；开放，这是通过刺激A2受体介导的。PKC的激活也涉及K_&lt；ATP和PKC的开放，但腺苷和PKC并不像其他组所报道的那样协同作用。A2受体和PKC激活之间的细胞内机制正在进行广泛的研究。较少

项目成果

Hiraoka M,Furukawa T,et al.: "Molecular and Cellular Mechanisms of Cardiovascular Regulation" Regulation of rundown and reactivation of cardiac ATP-sensitive K^+ channels., 83-91 (1996)

Hiraoka M,Furukawa T,et al.:“心血管调节的分子和细胞机制”心脏 ATP 敏感 K^ 通道的衰退和再激活调节。, 83-91 (1996)

Ishihara,K,Hiraoka M.et al.: "The tetravalent organic cation spermine causes the gating of the IRK1channel expressed in marine fibroblast cells." J. Physiol.491. 367-382 (1996)

Ishihara,K,Hiraoka M.等人：“四价有机阳离子精胺导致海洋成纤维细胞中表达的 IRK1 通道的门控。”

平岡 昌和: "細胞膜イオン電流-特にK電流を中心に。頻拍症" 西村書店, 51-66 (1996)

Masakazu Hiraoka：“细胞膜离子电流 - 特别是 K 电流。心动过速” 西村书店，51-66 (1996)

Yamane T,Furukawa T.& Hiraoka M.: "Characterization of 4-aminopyridine block of the noninactivating cloned K^+ channel,K_V1.5,expressed in Xenopus oocytes." Am.J.Physiol.269. H556-H564 (1995)

山根 T、古川 T.

Hiraoka M,Sawanobori T. et al.: "Mechanism of openings and role of the ATP-sensitive K^+ channelsduring myocardial ischemia/reperfusion." pathophysiology of Heart Failure. 427-437 (1996)

Hiraoka M，Sawanobori T.等人：“心肌缺血/再灌注期间ATP敏感K + 通道的开放机制和作用。”