Regulation of Contractility During Ischemia-Reperfusion

心肌梗塞是普遍的，每年诊断出约100万患者。更好地了解 细胞条件导致心肌细胞损伤和死亡，实验模型模拟了 心肌经历的缺血-再灌注（I-R）。I-R引起的ATP减少通常是 被认为是收缩力下降背后的驱动力。然而，最近的研究表明， 收缩丝的内在变化，如蛋白质水解或氧化还原依赖性蛋白 修饰也影响I-R期间的收缩性。本申请中的初步数据表明， 心肌收缩力的下降发生在缺血30分钟时，并在缺血60分钟时大部分逆转。 再灌注收缩力的可逆性下降与ATP的可用性无关，表明 收缩丝的内在变化最好地描述了这种下降。然而，这一时间表是 缺血期间蛋白质水解不足以被缺血期间的蛋白质合成和重新组装所拯救， 再灌注因此，这些收缩性的变化可能反映了可逆的共价修饰， 收缩丝的蛋白质，而不是它们的蛋白水解。根据这一假设，初步 数据表明，在I-R过程中，肌动蛋白发生可逆修饰，影响其与 原肌球蛋白因此，这项拨款申请旨在研究I-R期间的纤维收缩性， 表征可逆的修改蛋白质的收缩丝的基础变化， 收缩性该应用程序将测试缺血再灌注导致可逆的共价结合的假设。 修饰心肌细丝的蛋白质，从而通过 细丝调节蛋白相关性的变化。这一假设将通过以下方式进行检验：i） 确定I-R对心肌纤维收缩性的影响; ii）表征I-R依赖性 肌动蛋白的修饰，并确定I-R是否导致对其他细丝蛋白的共价修饰; iii） 确定肌动蛋白修饰对细丝组装以及肌动蛋白激活的肌球蛋白的影响 ATP酶这些发现将为I-R期间收缩缺陷的性质提供新的见解， 强调心肌细丝蛋白的状态及其对收缩性的影响。

Myocardial infarction is prevalent with -1 million patients diagnosed each year. To better understand the cellular conditions leading to cardiomyocyte damage and death, experimental models have mimicked the ischemia - reperfusion (I-R) experienced by the myocardium. The decrease in ATP with I-R is often considered the driving force behind the contractility decline. However, recent research suggests that changes intrinsic to the contractile filaments, such as protein proteolysis or redox-dependent protein modifications, also influence contractility during I-R. The preliminary data in this application indicate that a decline in cardiac muscle contractility occurs with 30' of ischemia and is largely reversed by 60' of reperfusion. The reversible decline in contractility was independent of ATP availability, suggesting that intrinsic changes to the contractile filaments best described the decline. However, this timeframe is insufficient for protein proteolysis during ischemia to be rescued by protein synthesis and re-assembly during reperfusion. Therefore, these changes in contractility may reflect reversible, covalent modifications to proteins of the contractile filaments rather than their proteolysis. Consistent with this hypothesis, preliminary data demonstrate that a reversible modification of actin occurs during I-R, affecting it's interaction with tropomyosin. Therefore, this grant application aims to investigate fibre contractility during I-R, and characterize the reversible modifications to proteins of the contractile filaments that underlie the changes in contractility. The application will test the hypothesis that ischemia-reperfusion results in reversible, covalent modifications to proteins of the cardiac muscle thin filament, consequently limiting contractility through changes in the association of thin filament regulatory proteins. This hypothesis will be examined by: i) determining the effect of I-R on the contractility of cardiac muscle fibres; ii) characterizing the I-R dependent modification of actin, and determining if I-R results in covalent modifications to other thin filament proteins; iii) determining the effect of modification of actin on thin filament assembly as well as the actin activated myosin ATPase. These findings will provide novel insight into the nature of the contractile deficit during I-R, with emphasis on the state of the cardiac muscle thin filament proteins and their effect on contractility.