REGULATION OF G PROTEIN COUPLED K+ CHANNEL FUNCTION

G 蛋白偶联 K 通道功能的调节

• 批准号: 6030711
• 负责人: Donghee Kim
• 金额: $ 18.59万
• 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 2001-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6030711
• 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）：心脏毒蕈碱 K+（KACH）电流在副交感神经调节中起重要作用 心率。 目前，通常认为 KACH电流取决于G蛋白刺激的程度 乙酰胆碱，导致通道开口频率的变化。 但是，申请人在切除的膜贴片中的最新研究 表示两个细胞内分子（ATP和一个未识别的胞质 因子）在开放概率上产生的变化多达10倍 由于G蛋白激活的Kach通道，由于其对 通道开放状态的持续时间。 ATP延长和胞质因子 缩短开放时间持续时间。 这些发现强烈表明 ACH在生理条件下通过ACH激活心房KACH电流 也可能涉及两个胞质分子介导的效果。 这 本申请中提出的研究旨在了解角色 ATP和KACH电流激活中未知的胞质因子 脱敏以及这些过程中涉及的机制。 现在， 关于ATP是否对活动有任何影响，存在争议 G蛋白激活的KACH通道。 因此，第一个特定目标 是要明确定义ATP在KACH电流激活中的作用， 特别是在更迅速和短暂的生理条件下 （毫秒）ACH的应用。 第二个具体目的是净化 心房的胞质因子均质并识别它。 这将有助于 揭示胞质因子的作用的细胞机理以及 Kach频道上的ATP。 第三个具体目的是检查 在缺乏卵母细胞中表达的Kach通道的行为（GIRK1/CIR） 心房胞质因子的活性。 使用此表达系统， 申请人将测试GIRK1/CIR的动力学行为是否一致 ATP的假设作用和心房胞质因子在 Kach电流（GIRK1/CIR）的激活和快速脱敏。