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.

该建议研究了毒蕈碱受体介导的机制 酶隔离的单个单一的钾通道的激活 牛蛙心房细胞。 ACH诱导的，内部的纠正 钾电流也被激活 在存在耐水性GTP类似物的情况下的方式， 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。 将在实验中检验几个假设 同时使用整个单元格和单个通道贴片夹 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。 这将接近 首先，通过两种方式进行耐水性GTP的实验 类似物（消除G蛋白更新并产生持久性 激活），其次，用扰动的代理的流动性 肌膜。 将要解决的另一个问题是缺乏 尽管没有ACH，但 G蛋白更新的显着速率（0.3 min-1）。 我们将测试 这是否是因为活化的G蛋白的亲和力对 通道很低。 调查的第三个领域是 通过毒蕈碱受体调节G蛋白功能， 专门解决了GDP是否增加的问题 释放率取决于受体类型。 最终假设 要测试的是G蛋白GTP水解速率 可能受到与通道相互作用的影响，因此 渠道自限制自己的激活。 这也将涉及 研究脱敏现象。 这些研究旨在洞悉动力学 受体-G蛋白的机理 - 介导的信号转导。 组件之间相互作用的定量模型 系统对于理解神经递质介导的至关重要 控制心脏的可伸缩性和收缩力，两个关键 正常心脏功能的决定因素。 这些研究也将 为研究其他G蛋白转导的研究提供了有用的模型 系统。