Molecular Mechanisms for Atrial Fibrillation in Aging

 描述(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，鉴于我们整个人口的老龄化，其患病率正在以惊人的速度上升。然而，房颤的治疗仍然不够充分，部分原因是我们对房颤的病理电生理学了解相对较少。在本应用中，我们建议重点研究衰老介导的房颤。其目的是研究衰老、氧化应激、乙酰胆碱敏感的内向整流钾电流IKACh和房颤之间先前未被探索的直接机制联系。我们将测试这一假设，即老年心房中增加的氧化应激激活PKCepsilon，而PKCepsilon反过来磷酸化Kir3.1-IKACh的一个分子相关的分子，导致毒碱刺激独立于成分活性的IKACh，动作电位时程缩短，以及房颤持续。我们的初步数据支持我们的假设：1)衰老促进了Kir3.1的磷酸化并导致IKACh的结构性激活，2)氧化应激激活了PKCepsilon，使Kir3.1磷酸化，并由于IKACh的结构性活性而缩短了心房动作电位，促进了负责房颤的转子的发育，以及3)Kir3.1的磷酸化启动了构象变化，从而增加了通道与其激活剂PIP2的相互作用，并导致通道内离子通透途径的开放。我们将在3个具体目标上验证我们的假设：1-) 通过氧化应激和PKCepsilon介导的Kir3.1磷酸化，研究在衰老过程中导致结构性活性IKACh的分子和信号通路；2)通过X射线结晶学和分子动力学模拟，确定被PKCepsilon磷酸化的Kir3.1的结构变化；以及3-)研究衰老、PKCepsilon和结构性活性IKACh在心房颤动的诱导性和动力学中的作用。 我们将同时利用几种互补而强大的技术(X射线结晶学、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，从而导致心房的心律失常电变化。我们推测，这些研究将增加我们对房颤病理电生理学的了解，并可能指导抗纤颤通路靶点的识别和新型、特异、有效的抗房颤药物的开发。

 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.