Molecular Mechanisms for Atrial Fibrillation in Aging

 描述（由申请人提供）：在临床实践中，房颤（AF）是最常见的心律失常，也是发病率和死亡率的主要原因。房颤的发病率随着年龄的增长而大大增加，考虑到我们总体人口的老龄化，其患病率正以惊人的速度上升。然而，房颤的治疗仍然不足，部分原因是我们对房颤病理电生理学的了解相对不足。在本申请中，我们建议关注衰老介导的AF。目标是调查以前未探索的衰老，氧化应激，乙酰胆碱敏感性内向整流钾电流IKACh和AF之间的直接机制联系。我们将测试以下假设：老年心房中氧化应激增加激活PKC β，从而磷酸化Kir3.1-IKACh的分子相关物，导致毒蕈碱刺激独立的组成性活性IKACh、动作电位持续时间缩短和AF永久化。我们的初步数据支持我们的假设，并表明：1-）衰老促进Kir3.1的磷酸化并导致IKACh的组成性激活，2-）氧化应激激活PKC β，磷酸化Kir3.1，并由于组成性活性IKACh而缩短心房动作电位，并促进负责AF的转子的发育，和3）Kir3.1的-磷酸化引发构象变化，这可以增加通道与其激活剂PIP 2的相互作用，并导致通道的细胞内离子渗透途径的开放。我们将在3个具体目标中测试我们的假设：1-） 通过氧化应激和PKC β介导的Kir3.1磷酸化来研究衰老中导致组成性活性IKACh的分子和信号通路：2-）通过X射线晶体学和分子动力学模拟来确定PKC β磷酸化Kir3.1发生的结构变化;（3）研究增龄、PKC β 2和IKACh活性在心房颤动的诱发和动力学中的作用。 我们将同时使用几种互补的和强大的技术（X射线晶体学，分子建模，分子生物学，单细胞和整个器官电生理学）来测试我们的目标，并从蛋白质结构到多细胞水平研究衰老如何改变离子通道的结构和功能，从而导致心房中的质子电变化的细节。我们推测，所提出的研究将增加我们对AF病理电生理学的理解，并可以指导抗心房颤动通路靶点的识别，以及新型、特异性和有效的抗心房颤动药物的开发。

 DESCRIPTION (provided by applicant): In clinical practice, atrial fibrillation (AF) is the most common heart rhythm disturbance, and a major cause of morbidity and mortality. The incidence of AF increases greatly with age, and given the aging of our overall population, its prevalence is rising at alarming rates. Yet the treatment of AF remains inadequate due in part to our relatively poor understanding of AF pathoelectrophysiology. In this application, we propose to focus on aging mediated AF. The goal is to investigate previously unexplored direct mechanistic links between aging, oxidative stress, the acetylcholine sensitive inward rectifier potassium current IKACh, and AF. We will test the hypothesis that the increased oxidative stress in aged atria activates PKCepsilon, which in turn phosphorylates Kir3.1- a molecular correlate of IKACh, leading to muscarinic stimulation independent constitutively active IKACh, shortening of action potential duration, and AF perpetuation. Our preliminary data support our hypothesis and show that: 1-) aging promotes the phosphorylation of Kir3.1 and leads to the constitutive activation of IKACh, 2-) oxidative stress activates PKCepsilon, phosphorylates Kir3.1, and shortens the atrial action potential due to a constitutively active IKACh, and facilitates the development of rotors responsible for AF, and 3)- phosphorylation of Kir3.1 initiates conformational changes which could increase the channel's interaction with its activator PIP2, and result in the opening of the channel's intracellular ion permeation pathway. We will test our hypothesis in 3 specific aims: 1-) To investigate the molecular and signaling pathways leading to constitutively active IKACh in aging, through oxidative stress and PKCepsilon mediated Kir3.1 phosphorylation; 2-) To determine the structural changes that occur in Kir3.1 phosphorylated by PKCepsilon, with X-ray crystallography and molecular dynamics simulations; and 3-) To study the role of aging, PKCepsilon and constitutively active IKACh in the inducibility and dynamics of atrial fibrillation. We will make simultaneous use of several complementary and powerful techniques (X-ray crystallography, molecular modeling, molecular biology, single cell, and whole organ electrophysiology) to test our aims and to investigate from the protein structure, to the multicellular level, the details of how aging modifies the structure and function of an ion channel leading to proarrhythmic electrical changes in the atria. We postulate that the studies proposed will increase our understanding of AF pathoelectrophysiology, and could direct the identification of antifibrillatory pathway targets, and the development of novel, specific, and effective anti-atral fibrillation agents.