C. Elegans and Mitochondrial K+ Channels

描述(申请人提供)：急性心肌梗塞是世界上主要的死亡原因，而中风是美国的第三大主要死亡原因。与这些情况相关的缺血-再灌注损伤可导致永久性组织损伤或神经功能障碍。然而，众所周知，短时间的非致命性缺血暴露会引起一种促适应性反应，在被称为预适应的过程中保护细胞免受随后的缺血损伤。线粒体是缺血-灌流损伤发病机制的核心，被认为是预适应的主要靶点。特别是，线粒体内膜上的离子通道(KATP和KCA通道)被认为可以减弱预适应后线粒体细胞的死亡反应。这些通道的分子同一性存在争议。这个建议的主要目标是明确地识别线粒体KATP和KCA通道，第二个目标是识别调节线粒体通道活动的信号过程，以响应预适应。为实现这些目标而设计的实验将在线虫体内进行。最近的研究表明，预适应可以保护这种遗传模式生物免受缺氧性损伤和死亡。此外，我们还发现线虫在其线粒体中表达功能性的KATP和KCA通道。我们建议结合两位研究人员的优势，一位在线粒体生物能量学和心血管生理学方面有丰富经验，另一位在线虫离子通道生理学方面有丰富经验，以检验KATP和KCA通道调节是一种进化保守的机制，有助于线虫的预适应。我们将利用线虫现有的大量遗传资源来筛选含有候选基因突变的菌株，用于纯化线粒体的通道活性，通过保守的信号通路进行通道调节，以及它们的预适应能力。这些实验的结果将提高我们开发针对通道或上游调节器的保护性疗法的能力，并旨在模拟哺乳动物的预适应效果。 与公共卫生相关：氧气供应减少会导致细胞损伤和死亡，特别是神经元(通过中风)或心肌细胞(通过心脏病发作)。然而，短暂的亚致命性低氧暴露可能会导致促进适应的机制，以防止随后的氧气减少。这一过程被称为“预适应”，在迄今研究过的所有细胞类型和生物体中，起着进化保守的早期预警系统的作用。我们建议通过线粒体中的功能来确定参与这种促适应条件作用的膜离子转运体的分子身份，并使用遗传模型生物秀丽线虫来研究它们的调控。这些分子的识别将有助于开发心脏病发作和中风的新疗法。

DESCRIPTION (provided by applicant): Acute myocardial infarction is a leading cause of death throughout the world, while stroke is the third leading cause of death in the United States. Ischemia-reperfusion injury associated with these conditions can lead to permanent tissue damage or neurologic deficits. It is well recognized that non-lethal exposure to ischemia for short periods of time however, elicits a proadaptive response that protects cells from subsequent ischemic injury in a process referred to as preconditioning. Mitochondria are central to the pathogenesis of ischemia- perfusion injury and are believed to be a major target for preconditioning. In particular, ion channels in the inner mitochondrial membrane that transport potassium (KATP and KCa channels) are believed to attenuate the mitochondrial cell death response following preconditioning. The molecular identity of these channels is controversial. The major goal of this proposal is to unambiguously identify the mitochondrial KATP and KCa channels, and a second goal is to identify signaling processes that regulate channel activity in the mitochondria in response to preconditioning. The experiments designed to meet these goals will be carried out in the nematode C. elegans. It has recently been shown that preconditioning can protect this genetic model organism from hypoxic injury and death. Moreover, we have found that C. elegans express functional KATP and KCa channels in their mitochondria. We propose to combine the strengths of two investigators, one with extensive experience in mitochondrial bioenergetics and cardiovascular physiology, and the other in nematode ion channel physiology, to test the hypothesis that KATP and KCa channel regulation is an evolutionarily conserved mechanism that contributes to preconditioning in C. elegans. We will utilize the vast array of genetic resources available in C. elegans to screen strains containing mutations in candidate genes for channel activity in purified mitochondria, for channel regulation via conserved signaling pathways, and for their ability to be preconditioned. The results from these experiments will improve our ability to develop protective therapeutics targeted at channels or upstream regulators and designed to mimic the effects of preconditioning in mammals. PUBLIC HEALTH RELEVANCE: Reduced oxygen availability causes cellular damage and death, particularly in neurons (via stroke) or cardiac myocytes (via heart attack). However, brief sub-lethal exposure to low oxygen can lead to proadaptive mechanisms that protect against subsequent decreases in oxygen. This process is called "preconditioning" and acts as an evolutionarily conserved early warning system in all cell types and organisms examined so far. We propose to determine the molecular identity of membrane ion transporters that have been implicated in this proadaptive conditioning via their function in the mitochondria and to study their regulation using the genetic model organism C. elegans. The identification of these molecules will help in the development of new therapies for heart attack and stroke.