Neuronal and Developmental Regulation of Pacemaker Channels

起搏器通道的神经元和发育调节

• 批准号: 6740406
• 负责人: Richard Robinson
• 金额: $ 17.92万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6740406
• 关键词: G protein; action potentials; age difference; angiotensin II; biological signal transduction; biophysics; cardiac myocytes; cardiogenesis; genetic transcription; heart electrical activity; heart innervation; heart pacemaker tissue; heart rhythm; heart ventricle; laboratory mouse; laboratory rat; membrane channels; neurohormones; neuropeptide Y; neuroregulation; newborn animals; norepinephrine; posttranslational modifications; protein isoforms; sympathetic nervous system; tissue /cell culture; voltage /patch clamp

The onset of cardiac sympathetic innervation is accompanied by developmental changes in cardiac ion channel function. Of particular importance is the evolution of a negative shift in activation voltage of the ventricular pacemaker current, I-f, identified in a previous collaborative study by Projects 8 and 9. I-f is of interest (1) because of its central role in the control of heart rate, which is rapid at birth and slows to less than half its original rate by adolescence, and (2) because it plays a role in rate and rhythm control in instances where disease induces a positive shift in activation of the current. The proposed aims of Project 9 derive from our earlier studies of developmental changes in I-f, as well as three observations made during the current funding period: 1) The developmental shift in I-f is partly reproduced by culturing neonatal ventricular cells with sympathetic nerves or in the sustained presence of neuropeptide Y (NPY) and norepinephrine. 2) I-f activates at less negative voltages in adult ventricular myocytes from mice lacking NPY than in cells from wild type, supporting a developmental role for NPY. 3) Over-expressed HCN2, a molecular correlate of I-f, activates at less negative voltages in neonatal than in adult rat ventricular myocytes, suggesting the existence of an age-specific factor influencing the gating of individual HCN isoforms. In this renewal application, Project 9 has four specific aims, targeted to the following questions: 1) What are the components of the NPY-dependent signaling cascade regulating I-f developmentally? 2) What additional signaling cascade(s) contributes to I-f maturation? 3) What is the molecular basis for the maturational change in I-f? 4) What are the functional consequences of HCN over-expression? We will employ single cells and cell cultures of neonatal and adult ventricular myocytes of rat and mouse, the latter to take advantage of knockout animals to elucidate the relevant signaling cascades. Both native I-f and over-expressed HCN currents will be studied. These studies are relevant to both regulation of normal cardiac developmental by sympathetic innervation and disease states involving abnormal innervation and associated arrhythmias. Further, by studying over-expression of pacemaker channel genes in myocytes rather than heterologous systems, Project 9 provides an innovative approach that uses the power of molecular biology while preserving the physiologic context essential to the ultimate elucidation of how these channels function, and can be controlled, in vivo.

心脏交感神经支配的开始伴随着心脏离子通道功能的发育性变化。特别重要的是在项目8和9之前的一项合作研究中发现的心室起搏器电流激活电压i-f的负移的演变。i-f令人感兴趣的是(1)因为它在心率控制中的中心作用，心率在出生时很快，到青春期时减慢到不到原始心率的一半；(2)因为在疾病引起电流激活正向移位的情况下，它在心率和节律控制中发挥作用。项目9的拟议目标来自我们先前对i-f发育变化的研究，以及在本资助期间的三个观察结果：1)i-f的发育变化部分是通过培养新生儿的脑室来复制的。 有交感神经的细胞或神经肽Y(NPY)和去甲肾上腺素持续存在的细胞。2)与野生型相比，缺乏NPY的成年小鼠心室肌细胞在负电压下激活的i-f较少，支持NPY的发育作用。3)在新生大鼠心肌细胞中，与i-f相关的高表达HCN_2在较低的负电压下被激活，提示存在影响单个HCN亚型门控的年龄特异性因素。在这一更新申请中，项目9有四个具体目标，针对以下问题：1)依赖NPY的信号级联在发育过程中调节I-F的组件是什么？2)哪些额外的信号 级联(S)有助于I-f成熟？3)I-f成熟变化的分子基础是什么？4)HCN过度表达有什么功能后果？我们将采用单个细胞和成年大鼠和成年大鼠的心肌细胞培养，后者利用基因敲除动物来阐明相关的信号级联反应。我们将研究天然的i-f电流和过度表达的hcn电流。这些研究既与交感神经对心脏正常发育的调节有关，也与涉及异常神经和相关心律失常的疾病状态有关。此外，通过研究起搏器通道基因在心肌细胞中的过度表达，而不是异源系统，项目9提供了一种创新的方法，它利用分子生物学的力量，同时 保存对最终阐明这些通道如何发挥作用以及在体内如何控制至关重要的生理学背景。