G PROTEIN-MEDIATED K+ CHANNEL ACTIVATION IN HEART

G 蛋白介导的心脏 K 通道激活

• 批准号: 3359880
• 负责人: GERDA E BREITWIESER
• 金额: $ 10.36万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-12-01 至 1993-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3359880
• 关键词: Anura; G protein; acetylcholine; biological signal transduction; guanosine triphosphate; heart; heart contraction; hydrolysis; muscarinic receptor; myocardium; neurotransmitter receptor; physical chemical interaction; potassium channel; voltage /patch clamp

This proposal studies the mechanism of muscarinic receptor-mediated activation of potassium channels in enzymatically isolated, single bullfrog atrial cells. The ACh-induced, inwardly rectifying potassium current is also activated in a receptor-independent manner in the presence of hydrolysis-resistant GTP analogs, and thus the activation mechanism must include an understanding of GTP binding protein (G protein)-channel interactions, as well as the effect of muscarinic receptor stimulation on G protein function. Several hypotheses will be tested, in experiments which will utilize both the whole cell and single channel patch clamp techniques. A key question is whether any of the characteristic kinetic properties ascribed to the potassium channel itself are the result of G protein)-channel interactions. This will be approached experimentally in two ways, first, with hydrolysis-resistant GTP analogs (which eliminate G protein turnover, and produce persistent activation), and second, with agents that perturb the fluidity of the sarcolemma. Another issue which will be addressed is the lack of potassium channel activation in the absence of ACh, despite significant rates of G protein turnover (0.3 min-1). We will test whether this is because the affinity of the activated G protein for the channel is low. The third area of investigation is the modulation of G protein function by muscarinic receptor, specifically addressing the question of whether the increase in GDP release rate is dependent on receptor type. The final hypothesis to be tested is that the rate of GTP hydrolysis by the G protein may be influenced by interaction with the channel, and thus the channel self-limits its own activation. This will also involve an investigation of the phenomenon of desensitization. These studies are designed to produce insight into the kinetic mechanism of receptor-G protein - mediated signal transduction. A quantitative model of the interactions among components of the system is crucial to an understanding of neurotransmitter-mediated control of cardiac exitability and contractility, two key determinants of normal cardiac function. These studies will also provide a useful model for the study of other G protein-transduced systems.

该提案研究毒蕈碱受体介导的机制 酶法分离的钾通道的激活，单一 牛蛙心房细胞。 乙酰胆碱诱导的内向矫正 钾电流也在不依赖受体的情况下被激活 在抗水解 GTP 类似物存在下的方式，以及 因此激活机制必须包括对 GTP 的理解 结合蛋白（G 蛋白）通道相互作用，以及 毒蕈碱受体刺激对G蛋白功能的影响。 将在实验中测试几个假设 利用全细胞和单通道膜片钳 技术。 一个关键问题是是否有任何特征 归因于钾通道本身的动力学特性是 G 蛋白）通道相互作用的结果。 这将被接近 实验有两种方式，第一，使用抗水解GTP 类似物（消除 G 蛋白周转，并产生持久的 激活），第二，使用扰乱流动性的试剂 肌膜。 另一个需要解决的问题是缺乏 尽管在缺乏乙酰胆碱的情况下钾通道的激活 G 蛋白周转率显着（0.3 min-1）。 我们将测试 这是否是因为活化的 G 蛋白的亲和力 频道低。 第三个调查领域是 通过毒蕈碱受体调节G蛋白功能， 专门解决GDP是否增长的问题 释放速率取决于受体类型。 最终假设 待测试的是G蛋白水解GTP的速率 可能会受到与渠道互动的影响，因此 通道自我限制其自身的激活。 这还将涉及一个 脱敏现象的调查。 这些研究旨在深入了解动力学 受体-G蛋白介导的信号转导机制。 组成部分之间相互作用的定量模型 系统对于理解神经递质介导的过程至关重要 控制心脏的退出性和收缩性，两个关键 正常心脏功能的决定因素。 这些研究也将 为其他G蛋白转导的研究提供有用的模型 系统。