REGULATORY MECHANISMS OF K+ CHANNEL FUNCTION IN HEART

受体调节的离子通道在神经内分泌中起主要作用 心功能的调节。因此，例如，胆碱能激活 心肌M受体的表达可能影响心肌细胞的启动和增殖 通过打开心肌肌膜上的钾通道来抑制心脏跳动。 这个项目的长期目标是定量地了解 在分子细节层面上，这些调控过程是如何 操作，特别强调最近发现的角色 受体效应器中的鸟嘌呤核苷酸结合蛋白(G蛋白) 耦合过程。具体地说，M胆碱能激活体内的 整流钾通道K+(M)的研究将在离体心内进行 心房肌细胞。 使用这一定义明确的制度应有助于实现 以下是三个主要目标。1.关键问题的识别 体内偶联过程中涉及的步骤及其建模 明确定义的化学动力学过程。全细胞千兆记录 将被用来跟踪K+(M)1的演化。 以适当的方式激活受体或G蛋白 揭示了受体-通道偶联所涉及的特定动力学步骤。 结果将被用来构建一个要测试的数学模型和 通过将其预测与实验进行比较而得到提炼。2.身份识别 激活体内K+(M)的G蛋白(S)的类型和部分 细胞内注射高纯度药物的效果特征 心肌细胞离子电流上的G蛋白成分。这个 结果将与在单通道级别上看到的结果密切相关 切除补片以确保这两种不同的技术 得出一致的和生理上相关的结论。3.努力 将重建脂双层中K(M)通道的控制 G蛋白和受体的细胞膜，最终目的是阐明 功能监管体系的结构要求。这 该项目可能会进一步加深我们对神经激素的理解 心功能正常和异常的调节。此外，由于 已发现G蛋白可将受体与效应器偶联。 所有的细胞类型，结果必然具有更普遍的意义 关于细胞外信号对细胞功能的控制。

Receptor-modulated ion channels play a primary role in the neuroendocrine regulation of cardiac function. Thus, for example, cholinergic activation of cardiac muscarinic receptors may affect the initiation and propagation of the heart beat by opening potassium channels in the cardiac sarcolemma. The long-range objective of this project is to understand quantitatively and at the level of molecular detail, how these regulatory processes operate, with particular emphasis on the recently discovered role of guanine nucleotide binding proteins (G-proteins) in the receptor effector coupling process. Specifically, muscarinic activation of the inwardly rectifying potassium channel K+(m) will be studied in isolated cardiac atrial myocytes. Use of this well defined system should facilitate the attainment of the following three primary objectives. 1. Identification of the critical steps involved in the coupling process in vivo and its modeling in terms of clearly defined chemical kinetic processes. Whole-cell gigaseal recording will be used to follow the evolution of K+(m) 1. in response to manipulations activating receptor or G-protein in a manner appropriate for revealing the specific kinetic steps involved in receptor-channel coupling. The results will be used to construct a mathematical model to be tested and refined by comparing its predictions with experiment. 2. Identification of the type and moiety of G-protein(s) that activate K+(m) in vivo by characterizing the effects of intracellularly injected, highly purifiid G-protein components on the ionic currents of cardiac myocytes. The results will be carefully related to those seen at the single-channel level with excised patches in order to insure that these two different techniques yield consistent and physiologically relevant conclusions. 3. Efforts will be made to reconstitute the control of K(m) channels in lipid bilayer membranes by G-protein and receptor, with the ultimate goal of elucidating the structural requirements for a functional regulatory system. This project is likely to further our understanding of the neurohormonal regulation of normal and abnormal cardiac function. Moreover, since G-proteins have been found to couple receptors to effectors in virtually all cell types, the results are bound to be of more general significance with respect to the control of cell function by extracellular signals.