Modulation of heart function by Muscle LIM protein-mediated mechanotransduction

家族性肥厚型心肌病（HCM）是最常见的遗传性心脏病， 通过编码调节心肌收缩力的肌节蛋白的基因突变。HCM的表现包括 左心室肥大和心力衰竭、心律失常和心源性猝死。力学信号转导机制 一种机制，通过这种机制，失调的肌节力产生被感知并导致病理性重塑 在HCM中仍然知之甚少，从而抑制了新疗法的有效开发。我们的发现 是基于对HCM个体的严重表型和HCM中的第二次遗传改变的见解。 肌节机械感应蛋白我们有效地从患者特异性诱导的心肌细胞中获得心肌细胞。 多能干细胞（iPSC-CM），并通过将iPSC-CM接种到 具有天然心脏纤维排列的激光切割支架，用于研究人类心脏机械生物学， 细胞和组织水平。再加上肌肉收缩和疾病救助的计算建模 通过基因编辑和药理学干预，我们已经确定了一种新的机械转导 在HCM中的路径。心肌肌球蛋白肌节突变导致肌动球蛋白桥形成增强 重链（MYH7）导致增加的力产生，当与较慢的抽搐松弛相结合时， 使肌肉LIM蛋白（MLP）拉伸感应复合物在Z盘处不稳定。随后， 肌节MLP水平引起钙调神经磷酸酶-活化T细胞核因子（NFAT）信号传导的去抑制， 从而促进心脏肥大。通过以下途径减轻增强的肌动球蛋白交联桥的形成 通过遗传或药理学手段，我们减轻了Z盘的压力，防止了肥大的发展。 与肌节突变有关这个建议将剖析收缩期和舒张期Z盘应力的作用 在调节MLP机械感觉复合体中的作用，并阐明介导MLP机械感觉复合体的分子机制。 通过MLP抑制钙调磷酸酶/NFAT以及通过拉伸传感降解MLP蛋白。我们最近 开发了一种新的生物反应器，可以将EHT暴露于精确规定的后负荷，因此我们可以测试 假设在较高的后负荷下，由横桥产生的较高的收缩力使MLP在 在收缩期激活肥大信号。此外，EHT将在以下条件下进行培养 恒定长度或舒张期伸展的条件，以模拟心室充盈。经过反复的拉伸， 将检查肥大信号。我们将解开机械的见解如何saromeric MLP是 在Z盘应力下降解。此外，我们将剖析MLP抑制 钙调神经磷酸酶/NFAT肥大反应。阐明了一种抗肿瘤药物的分子机制 常见的肌节收缩/MLP/钙调神经磷酸酶机械转导通路将有助于设计新的肌节收缩/MLP/钙调神经磷酸酶机械转导通路。 可能通过稳定Z盘MLP机械感觉，为广泛的心力衰竭患者提供策略 复杂.

Familial hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease and is typically caused by mutations in genes encoding sarcomeric proteins that regulate cardiac contractility. HCM manifestations include left ventricular hypertrophy and heart failure, arrythmias, and sudden cardiac death. The mechanotransduction mechanism by which dysregulated sarcomeric force production is sensed and leads to pathological remodeling remains poorly understood in HCM, thereby inhibiting the efficient development of new therapeutics. Our discovery was based on insights from a severe phenotype of an individual with HCM and a second genetic alteration in a sarcomeric mechano-sensing protein. We effectively derived cardiomyocytes from patient-specific induced pluripotent stem cells (iPSC-CMs) and developed robust engineered heart tissues (EHTs) by seeding iPSC-CMs into a laser-cut scaffold possessing native cardiac fiber alignment, for studying human cardiac mechanobiology at both cellular and tissue levels. Coupled with computational modeling for muscle contraction and rescue of disease phenotype via gene editing and pharmacological interventions, we have identified a new mechanotransduction pathway in HCM. Enhanced actomyosin crossbridge formation caused by sarcomeric mutations in cardiac myosin heavy chain (MYH7) led to increased force generation, which when coupled with slower twitch relaxation, destabilized the muscle LIM protein (MLP) stretch-sensing complex at the Z-disc. Subsequent reduction in the sarcomeric MLP level caused disinhibition of calcineurin–nuclear factor of activated T-cells (NFAT) signaling, which promoted cardiac hypertrophy. By mitigating enhanced actomyosin crossbridge formation through either genetic or pharmacological means, we alleviated stress at the Z-disc, preventing the development of hypertrophy associated with sarcomeric mutations. This proposal will dissect the roles of systolic and diastolic Z-disc stress in modulating the MLP mechanosensory complex and elucidate the molecular mechanisms that mediate the repression of calcineurin/NFAT by MLP as well as MLP protein degradation by stretch-sensing. We have recently developed a new bioreactor that can expose EHTs to precisely prescribed afterloads, so we can test the hypothesis that higher systolic forces produced by crossbridges under higher afterloads destabilize MLP at the Z-disc and activate hypertrophic signaling during systole. Additionally, EHTs will be subjected to culture under conditions of either constant length or diastolic stretch to mimic ventricular filling. After repeated stretching, EHTs will be examined for hypertrophic signaling. We will unravel mechanistic insights into how saromeric MLP is degraded in response to Z-disc stress. In addition, we will dissect molecular mechanisms by which MLP inhibits calcineurin/NFAT hypertrophic responses in systole and diastole. Elucidation of the molecular mechanisms of a common sarcomeric contraction/MLP/calcineurin mechanotransduction pathway will help to design novel strategies for a wide spectrum of heart failure patients potentially through stabilizing the Z-disk MLP mechanosensory complex.