REGULATORY MECHANISMS OF K+ CHANNEL FUNCTION IN HEART

受体调节的离子通道在神经内分泌系统中起主要作用， 调节心脏功能。 例如，胆碱能激活 心肌毒蕈碱受体的表达可能影响心肌细胞的启动和增殖， 通过打开心脏肌膜中的钾离子通道来控制心脏跳动。 这个项目的长期目标是定量地了解 在分子细节的层面上，这些调控过程 特别强调最近发现的 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，毒蕈碱激活了 整流钾通道K+（m）将在离体心脏中进行研究 心房肌细胞 使用这一明确界定的制度应有助于实现 三个主要目标。 1. 识别关键 体内偶联过程中涉及的步骤及其在 明确定义的化学动力学过程。 全细胞千兆密封记录 将用于跟踪K+（m）1的演变。 响应于 以适合的方式激活受体或G蛋白的操作， 揭示了受体-通道偶联中涉及的特定动力学步骤。 结果将用于构建待测试的数学模型， 通过将其预测与实验进行比较来改进。 2. 识别 通过以下方式在体内激活K+（m）的G蛋白的类型和部分 表征细胞内注射的高纯度的 G蛋白成分对心肌细胞离子电流的影响。 的 结果将与单通道水平上观察到的结果密切相关 为了确保这两种不同的技术 得出一致的生理相关结论。 3. 努力 将重建的控制K（m）通道的脂质双层 膜的G蛋白和受体，最终目的是阐明 功能性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， 调节正常和异常的心脏功能。 而且由于 已经发现G蛋白在实际中将受体与效应物偶联。 所有细胞类型，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.