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。 该项目的长期目标是从数量上了解 在分子细节的层面上，这些调控过程是如何运作的， 特别强调了最近发现的鸟嘌呤的作用 受体效应偶联中的核苷酸结合蛋白(G蛋白) 进程。具体地说，毒扁豆碱激活了内向整流 钾通道K+(M)在分离的心脏心房肌细胞中的研究 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.关键步骤的确定 参与体内的偶联过程及其建模 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.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。结果是 将仔细地与在单通道级别上看到的 切除补片，以确保这两种不同的技术 一致且生理上相关的结论。3.努力将是疯狂的 重建脂双层膜上K(M)通道的控制 G-蛋白和受体，最终目的是阐明其结构 对功能健全的监管系统的要求。这个项目很可能会 进一步加深我们对正常和正常的神经激素调节的理解 心脏功能异常。此外，由于G-蛋白已被发现 将受体与几乎所有细胞类型的效应器偶联，结果是 必然对CEL的控制具有更广泛的意义 通过细胞外信号发挥作用。

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 an 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 yiel consistent and physiologically relevant conclusions. 3. Efforts will be mad to reconstitute the control of K(m) channels in lipid bilayer membranes by G-protein and receptor, with the ultimate goal of elucidating the structura 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 cel function by extracellular signals.