MODULATION OF CARDIAC L TYPE CALCIUM CHANNELS

心脏 L 型钙通道的调节

基本信息

批准号：
6302144
负责人：
ROBERT L ROSENBERG
金额：
$ 23.45万
依托单位：
UNIV OF NORTH CAROLINA CHAPEL HILL
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-04-01 至 2000-11-30
项目状态：
已结题

项目摘要

L-type Ca channels serve many vital functions in the heart. They sustain the plateau of the action potential and help set action potential duration and refractoriness. The influx of Ca2+ through L-type Ca channels triggers Ca2+ release from the sarcoplasmic reticulum, establishing the link between electrical activity at the cell surface and the contraction of cardiac myoctes. L-type Ca channels in nodal cells contribute to pacemaker activity and to the speed of conduction in those cells. Their activity may also play an important role in the generation of very slow conduction in ischemic myocardium, and especially at the border between normal and ischemic regions. In order to understand the basis of electrical re-entry that can occur at the ischemic border zone to trigger dangerous ventricular arrhythmias, it is crucial to understand factors that modulate Ca channels. The long-term goal of this project is to characterize the molecular mechanisms responsible for the modulation of cardiac L-type Ca channels, with special attention to the conditions that exist at the ischemic border zone. Because ischemic myocardium has a depolarized resting potential, high intracellular Ca2+, and low border zone. Because ischemic myocardium has a depolarized resting potential, high intracellular Ca2+, and low intracellular and extracellular pH, and because cardiac ischemia produces large beta-adrenergic stimulation, Specific Aim 1 focuses on the regulation of L-type Ca channels by protein kinase A under depolarized, Elevated Ca2+, and acidic pH conditions. We hypothesize that PKA stimulation sustains the activity of Ca channels the might otherwise become inactivated, leading to a abnormal slow conduction. Because beta- adrenergic release of norepinephrine is accompanied by a release of ATP, Specific Aim 2 focuses on some new observations of the effects of extracellular ATP on L-type Ca channels. Lipid metabolism is affected by ischemia, so Specific Aim 3 focuses on the regulation of L-type Ca channels by lysolipids and metabolites of arachidonic acid. Finally, Specific Aim 4 focuses on the regulation of Ca channels by nitric oxide and S-nitrosothiols. The experimental approach is to characterize the regulation of single L-type Ca channels incorporated from cardiac sarcolemma into planar lipid bilayers. We will record single channel activity of the reconstituted Ca channels, and evaluate channel conductance and unitary gating events. We control the extracellular and intracellular ionic conditions on both sides of the channels, the activity of endogenous regulatory enzymes like kinases and phosphatases, and the membrane environment. Thus, we will create conditions that mimic the ischemic border zone, and make a detailed characterization of the modulation of Ca channels there.

L型CA通道在心脏中起许多重要的功能。他们维持行动潜力的高原并帮助设定行动潜力持续时间和磨性。 Ca2+通过L型Ca通道的涌入触发Ca2+从肌质网释放，建立细胞表面的电活动与收缩之间的联系心脏肌肉。淋巴结细胞中的L型Ca通道有助于起搏器活性和这些细胞的传导速度。他们的活动在非常慢的一代中也可能发挥重要作用缺血性心肌，尤其是在正常和缺血区域。为了了解可以在缺血边界区域发生的电气再进入以触发危险的心室心律不齐，了解因素至关重要调节CA通道。该项目的长期目标是表征分子负责调节心脏L型CA通道的机制，特别关注缺血边界存在的条件区。因为缺血性心肌具有去极化的静息潜力，所以高细胞内Ca2+和低边界区域。因为缺血性心肌具有去极化的静息电势，高细胞内Ca2+，低细胞内和细胞外pH，并且由于心脏缺血会产生大型β-肾上腺素能刺激，特定目标1专注于通过蛋白激酶A的蛋白激酶A调节L型Ca通道， Ca2+升高和酸性pH条件。我们假设PKA 刺激维持CA通道的活性可能灭活，导致异常的缓慢传导。因为beta- 去甲肾上腺素的肾上腺素释放伴随着ATP的释放具体目标2重点介绍了一些新的观察结果 L型Ca通道上的细胞外ATP。脂质代谢受到影响缺血，因此特定的目标3着重于L型CA的调节溶酶体和花生四烯酸代谢产物的通道。最后，特定的目标4专注于一氧化氮对CA通道的调节和S-硝基硫醇。实验方法是表征单一调节从心脏肌膜中纳入的L型CA通道中的脂质双层。我们将记录重组CA的单个通道活动渠道，评估渠道电导和统一的门控事件。我们控制两侧的细胞外离子条件在通道中，内源性调节酶的活性激酶和磷酸酶以及膜环境。因此，我们会的创建模仿缺血边界区域的条件，并详细在那里的CA通道调制的表征。