REGULATION OF G PROTEIN COUPLED K+ CHANNEL FUNCTION

G 蛋白偶联 K 通道功能的调节

• 批准号: 2735282
• 负责人: Donghee Kim
• 金额: $ 18.07万
• 依托单位: ROSALIND FRANKLIN UNIV OF MEDICINE & SCI
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-07-01 至 2000-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2735282
• 关键词: G protein; Xenopus oocyte; acetylcholine; adenosine triphosphate; cell communication molecule; electrophysiology; heart conduction system; heart rhythm; muscarinic receptor; potassium channel; receptor coupling; tissue /cell culture

DESCRIPTION (adapted from the applicant's abstract): The cardiac muscarinic K+ (KACh) current plays an important role in the parasympathetic regulation of heart rate. At present, it is generally believed that the magnitude of the KACh current is determined by the degree of G protein stimulation by acetylcholine, resulting in changes in the frequency of channel opening. However, recent studies by the applicant in excised membrane patches indicate that two intracellular molecules (ATP and an unidentified cytosolic factor) can produce as much as a 10 fold change on the open probability of the KACh channels activated by G protein, due to their marked effects on the duration of the channel open state. ATP prolongs and the cytosolic factor shortens the open time duration. These findings strongly suggest that activation of the atrial KACh current by ACh under physiological conditions may also involve such effects mediated by the two cytosolic molecules. The studies proposed in this application seek to gain understanding of the roles of ATP and the unknown cytosolic factor in KACh current activation and fast desensitization, and the mechanisms involved in these process. At present, there is a controversy as to whether ATP has any effect on the activity of the KACh channel activated by G protein. Therefore, the first specific aim is to clearly define the role of ATP in KACh current activation, particularly under more physiological conditions using rapid and short (millisecond) applications of ACh. The second specific aim is to purify the atrial cytosolic factor to homogeneity and identify it. This will help to reveal the cellular mechanism of action of the cytosolic factor as well as that of ATP on the KACh channel. The third specific aim is to examine the behavior of the KACh channel (GIRK1/CIR) expressed in oocytes which lack the activity of the atrial cytosolic factor. Using this expression system, the applicant will test whether the kinetic behavior of GIRK1/CIR is consistent with the hypothesized roles of ATP and the atrial cytosolic factor in the activation and fast desensitization of the KACh current (GIRK1/CIR).

描述（改编自申请人的摘要）：强心毒蕈碱 K+ (KACh) 电流在副交感神经调节中发挥重要作用 心率。 目前普遍认为，其规模 KACh 电流由 G 蛋白刺激程度决定 乙酰胆碱，导致通道开放频率的变化。 然而，申请人最近对切除膜贴片的研究 表明两个细胞内分子（ATP 和一个未识别的细胞质 因素）可以使开放概率产生多达 10 倍的变化 KACh 通道被 G 蛋白激活，因为它们对 通道打开状态的持续时间。 ATP延长和胞质因子 缩短开放时间。 这些发现强烈表明 生理条件下ACh激活心房KACh电流 也可能涉及由两种胞质分子介导的此类效应。 这 本申请中提出的研究旨在了解这些角色 ATP 和未知胞质因子在 KACh 电流激活和快速 脱敏，以及这些过程中涉及的机制。 现在， 关于 ATP 是否对 ATP 的活性有影响，目前存在争议。 G蛋白激活的KACh通道。 因此，第一个具体目标 是为了明确定义 ATP 在 KACh 电流激活中的作用， 特别是在更多的生理条件下使用快速和短时间 （毫秒）ACh 的应用。 第二个具体目标是净化 心房胞质因子的同质性并对其进行识别。 这将有助于 揭示胞质因子的细胞作用机制以及 KACh 通道上的 ATP 的值。 第三个具体目标是检查 缺乏 KACh 通道 (GIRK1/CIR) 的卵母细胞中表达的行为 心房胞质因子的活性。 使用该表达系统， 申请人将测试GIRK1/CIR的动力学行为是否一致 ATP 和心房胞质因子在 KACh 电流 (GIRK1/CIR) 的激活和快速脱敏。