Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
J Mol Cell Cardiol. 2012 Jan;52(1):154-64. doi: 10.1016/j.yjmcc.2011.09.011. Epub 2011 Sep 19.
Cardiac myosin binding protein-C (cMyBP-C) is a thick filament assembly protein that stabilizes sarcomeric structure and regulates cardiac function; however, the profile of cMyBP-C degradation after myocardial infarction (MI) is unknown. We hypothesized that cMyBP-C is sensitive to proteolysis and is specifically increased in the bloodstream post-MI in rats and humans. Under these circumstances, elevated levels of degraded cMyBP-C could be used as a diagnostic tool to confirm MI. To test this hypothesis, we first established that cMyBP-C dephosphorylation is directly associated with increased degradation of this myofilament protein, leading to its release in vitro. Using neonatal rat ventricular cardiomyocytes in vitro, we were able to correlate the induction of hypoxic stress with increased cMyBP-C dephosphorylation, degradation, and the specific release of N'-fragments. Next, to define the proteolytic pattern of cMyBP-C post-MI, the left anterior descending coronary artery was ligated in adult male rats. Degradation of cMyBP-C was confirmed by a reduction in total cMyBP-C and the presence of degradation products in the infarct tissue. Phosphorylation levels of cMyBP-C were greatly reduced in ischemic areas of the MI heart compared to non-ischemic regions and sham control hearts. Post-MI plasma samples from these rats, as well as humans, were assayed for cMyBP-C and its fragments by sandwich ELISA and immunoprecipitation analyses. Results showed significantly elevated levels of cMyBP-C in the plasma of all post-MI samples. Overall, this study suggests that cMyBP-C is an easily releasable myofilament protein that is dephosphorylated, degraded and released into the circulation post-MI. The presence of elevated levels of cMyBP-C in the blood provides a promising novel biomarker able to accurately rule in MI, thus aiding in the further assessment of ischemic heart disease.
心肌肌球蛋白结合蛋白 C（cMyBP-C）是一种粗肌丝组装蛋白，可稳定肌节结构并调节心脏功能；然而，心肌梗死后 cMyBP-C 的降解情况尚不清楚。我们假设 cMyBP-C 易受蛋白水解作用的影响，并且在大鼠和人类心肌梗死后特别增加，在血液中循环。在这种情况下，升高的降解 cMyBP-C 水平可作为一种诊断工具用于确认心肌梗死。为了验证这一假设，我们首先确定 cMyBP-C 的去磷酸化与这种肌丝蛋白的降解增加直接相关，导致其在体外释放。通过在体外使用新生大鼠心室肌细胞，我们能够将缺氧应激的诱导与 cMyBP-C 的去磷酸化、降解和 N'-片段的特异性释放相关联。接下来，为了定义心肌梗死后 cMyBP-C 的蛋白水解模式，结扎成年雄性大鼠的左前降支冠状动脉。通过总 cMyBP-C 的减少和梗死组织中降解产物的存在来确认 cMyBP-C 的降解。与非缺血区和假手术对照心脏相比，缺血区 MI 心脏中 cMyBP-C 的磷酸化水平大大降低。来自这些大鼠以及人类的 MI 后血浆样本通过夹心 ELISA 和免疫沉淀分析检测 cMyBP-C 及其片段。结果表明，所有 MI 后样本的血浆中 cMyBP-C 水平显著升高。总体而言，这项研究表明 cMyBP-C 是一种易释放的肌丝蛋白，在心肌梗死后会去磷酸化、降解并释放到循环中。血液中 cMyBP-C 水平升高表明存在 MI，提供了一种有前途的新型生物标志物，可准确诊断 MI，从而有助于进一步评估缺血性心脏病。
