Myosin Isoforms in Relation to Function in Human Heart

肌球蛋白亚型与人类心脏功能的关系

• 批准号: 6786062
• 负责人: Richard L Moss
• 金额: $ 36.38万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6786062
• 关键词: SDS polyacrylamide gel electrophoresis; calcium flux; cardiac myocytes; clinical research; disease /disorder model; gel electrophoresis; heart contraction; heart function; human tissue; immunocytochemistry; laboratory rat; model design /development; monoclonal antibody; muscle function; myocardium; myosins; protein isoforms; protein structure function; thyroid function; tissue /cell culture

DESCRIPTION (provided by applicant): The myosin heavy chain (MHC) isoforms expressed in the left ventricle are primary determinants of the work capacity of mammalian hearts. Until recently, the prevailing view was that adult human ventricles expressed virtually 100% beta MHC (a slow isoform), but contemporary studies have shown that normal human ventricles express small amounts of alpha MHC (a fast isoform) on a predominantly beta MHC background and that failing human ventricles express 100% beta MHC and virtually no alpha MHC. Questions that arise from these results are whether expression of alpha MHC contributes to the rate of rise of pressure in normal human ventricles and whether loss of alpha MHC contributes to the depressed contractile performance of human failing hearts. This project will address these possibilities based on the working hypothesis that expression of small amounts of alpha MHC significantly speeds the kinetics of force development in normal myocardium, and conversely, reduced expression of alpha MHC contributes to depressed kinetics of force (pressure) development in heart failure. The proposed experiments will assess the effects on contractile properties due to altered ratios of alpha and betaa MHC expression in (i) rodent myocardium in which MHC expression is varied by manipulating thyroid status of the animals and (ii) myocardium from normal human hearts (donor hearts not used for transplant) and failing hearts (explanted hearts from transplant recipients). Rate constants of force development and relaxation will be assessed from changes in force following photolysis of caged Ca 2+ chelators. Results will then be used to model the effects of altered myosin isoform expression on twitch kinetics and amplitude in both rat and human myocardium. Additional mechanical experiments will investigate the roles of alpha MHC and beta MHC in determining the power and stretch activation responses of myocardium. Immunohistochemistry using MHC-isoform specific antibodies and SDS-PAGE of muscle samples will quantify MHC isoform expression patterns in regions of the left ventricle to test the idea that MHC expression varies in relation to systolic wall stress. Results from these studies should provide new insights into mechanisms of depressed myocardial function in human heart failure and should also suggest new therapeutic targets for treatment of this disease.

描述（由申请人提供）：左心室中表达的肌球蛋白重链（MHC）亚型是哺乳动物心脏工作能力的主要决定因素。直到最近，普遍的观点是成年人的心室表达几乎 100% 的 β MHC（一种慢异构体），但当代研究表明，正常人的心室在以 β MHC 为主的背景下表达少量的 α MHC（一种快异构体），并且衰竭的人类心室表达 100% β MHC，几乎不表达 α MHC。这些结果引起的问题是，α MHC 的表达是否会导致正常人心室压力上升的速度，以及 α MHC 的缺失是否会导致人类衰竭心脏的收缩性能下降。该项目将基于以下工作假设来解决这些可能性：少量 α MHC 的表达可显着加速正常心肌中力发展的动力学，相反，α MHC 表达的减少会导致心脏中力（压力）发展的动力学降低。失败。拟议的实验将评估由于 (i) 啮齿类动物心肌中 α 和 βa MHC 表达比例的改变对收缩特性的影响，其中 MHC 表达通过操纵动物的甲状腺状态而变化，以及 (ii) 来自正常人类心脏（供体）的心肌未用于移植的心脏）和衰竭的心脏（来自移植受者的移植心脏）。力产生和松弛的速率常数将根据笼中Ca 2+ 螯合剂光解后力的变化来评估。然后，结果将用于模拟改变的肌球蛋白亚型表达对大鼠和人类心肌抽搐动力学和振幅的影响。其他机械实验将研究 α MHC 和 β MHC 在确定心肌的功率和拉伸激活反应中的作用。使用 MHC 同工型特异性抗体和肌肉样本的 SDS-PAGE 进行免疫组织化学，将量化左心室区域中的 MHC 同工型表达模式，以测试 MHC 表达随收缩期壁应力变化的观点。这些研究的结果应该为人类心力衰竭心肌功能抑制的机制提供新的见解，并且还应该为治疗这种疾病提出新的治疗靶点。