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，通常由 通过编码肌节蛋白的基因突变来调节心脏收缩能力。HCM的表现包括 左心室肥厚和心力衰竭、心律失常和心脏性猝死。机械转导 感知肌节作用力异常并导致病理性重塑的机制 在肥厚型心肌病中仍然知之甚少，从而抑制了新疗法的有效开发。我们的发现 是基于对一名肥厚型心肌炎患者的严重表型和第二次基因改变的洞察 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了 多能干细胞(IPSC-CMS)和通过种植IPSC-CMS发展成强大的工程心脏组织(EHTS 一种具有天然心脏纤维排列的激光切割支架，用于在两边研究人类心脏力学生物学 细胞和组织水平。与肌肉收缩和疾病救援的计算建模相结合 通过基因编辑和药物干预，我们已经确定了一种新的机械转导 HCM中的通路。肌球蛋白肌瘤突变引起的肌动球蛋白交叉桥形成增强 重链(MYH7)导致了更多的力量产生，当再加上较慢的抽搐放松时， 破坏了Z盘处的肌肉LIM蛋白(MLP)拉伸传感复合体的稳定性。随后减少了 肌瘤MLP水平可解除钙调神经磷酸酶激活T细胞核因子(NFAT)信号的抑制， 促进了心肌肥大。通过以下两种途径之一减轻肌动球蛋白交叉桥的形成 通过遗传或药物手段，我们缓解了Z盘应力，防止了肥大的发展 与肉瘤突变有关。这项建议将剖析收缩和舒张期Z盘应力的作用 在调节MLP机械感觉复合体方面并阐明介导MLP的分子机制 MLP对钙调神经磷酸酶/NFAT的抑制以及拉伸传感对MLP蛋白的降解。我们最近做了 开发了一种新的生物反应器，可以将EHTS暴露在精确的规定后负载中，所以我们可以测试 假设在较高的后载下，交叉桥产生的较高的收缩力会破坏MLP在 Z-Disc和激活收缩期间的肥大信号。此外，EHTS将在以下条件下接受文化 恒定长度或舒张期拉伸以模拟脑室充盈的状态。经过反复拉伸，EHTS 将接受肥大信号检查。我们将揭开MLP的机械性洞察力 在Z-Disc压力下退化。此外，我们还将剖析MLP抑制的分子机制 钙调神经磷酸酶/NFAT在收缩和舒张期的肥大反应。A的分子机制的阐明 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 通过稳定Z-Disk MLP机械感觉对广泛心力衰竭患者的潜在策略 很复杂。

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.