ANGIOTENSIN II AND CARDIAC G PROTEIN COUPLED ION CHANNEL

肌力变力和变时性的细胞机制 血管紧张素Ⅱ在心脏中的作用尚不清楚；然而，离子通道 显然在心输出量的调节中起着关键作用 收缩能力和心率。越来越多的证据表明，Ang II已经 对心脏电生理的急性影响，以及临床 调节肾素-血管紧张素系统的有益效果良好 为人所知。目前还不清楚这两个观察结果之间是如何联系的。这个 这项提案的具体目标是描述以下方面的严重影响 血管紧张素Ⅱ对心肌钙通道和延迟整流钾通道的影响 心脏收缩能力的重要调节剂，并检查 血管紧张素Ⅱ受体利用的受体-G蛋白信号转导通路 心。为了解决这些问题，我们将使用从 通过体外分化小鼠胚胎干细胞。这 与原代培养相比，组织培养模型具有许多优势。 心肌细胞培养。最重要的是，我们已经产生了一组变种人 靶向灭活特定G蛋白α亚基的ES细胞。 一旦电生理反应被表征，Ang II 负责识别每个通道的受体亚型，我们将使用 这些阿尔法亚单位为零的细胞来识别所需的G蛋白 向每个效应器发送信号。这项建议所概述的研究是 了解血管紧张素转换酶II的急性影响的关键第一步 心脏电生理学与正常心脏功能的关系及其如何 系统在病理状态下发生改变。

The cellular mechanisms which underlie the inotropic and chronotropic effects of ANG II in heart are not well understood; however, ion channels clearly play critical roles in the regulation of cardiac output through contractility and heart rate. There is increasing evidence that ANG II has acute effects on the electrophysiology of the heart, and the clinically beneficial effects of modulating the renin-angiotensin system are well known. It is not yet clear how these two observations are related. The specific goals of this proposal are to characterize the acute effects of ANG II on cardiac Ca2+ channels and delayed rectifier K+ channels, two important modulators of cardiac contractility, and to examine the receptor-G protein signaling pathways utilized by ANG II receptors in heart. To address these questions we will use cardiac-like cells derived by in vitro differentiation from mouse embryonic stem (ES) cells. This tissue culture model offers a number of advantages over studies of primary cardiocyte cultures. Most importantly, we have generated a panel of mutant ES cells with targeted inactivation of specific G protein alpha subunits. Once the electrophysiological responses are characterized and the ANG II receptor subtypes responsible for each channel identified, we will use these alpha subunit null cells to identify G proteins required for signaling to each effector. The studies outlined in this proposal are the critical first step in understanding how the acute effects of ANG II on cardiac electrophysiology relate to normal cardiac function and how this system is altered in pathologic states.