Role of the giant protein titin in cardiac health and disease

总结 这项提案的重点是肌联蛋白，已知的最大的蛋白质，在心脏功能和疾病。提坦写了一部小说， 横纹肌肌节中的多功能肌丝具有重要作用，包括调节 心脏舒张期僵硬最近的突破性研究表明，肌联蛋白是高临床重要性， 射血分数保留的心力衰竭（HFpEF）和射血分数降低的心力衰竭 （HFrEF）。虽然在理解肌联蛋白的基础生物学方面已经取得了重大进展，但在 我们的理解仍然存在，包括对肌联蛋白如何引起/促进心脏的机制的理解。 疾病这项建议的一个重要重点是肌联蛋白在舒张功能障碍中的作用，其动机是最近的研究。 对HFpEF患者的研究显示肌联蛋白分子弹簧元件的磷酸化紊乱， 舒张期硬化将研究HFpEF中发生的全谱翻译后修饰， 高分辨率的时间分辨光谱技术将集中在揭示铁蛋白的结构变化 翻译后修饰触发的弹簧元件。药物筛选将侧重于识别化合物 模拟或阻止这些结构变化和功能研究将测试是否新发现的， 候选药物改善HFpEF中基于肌联蛋白的舒张硬化。转录后机制将是 利用我们最近的工作表明，肌联蛋白的剪接可以被操纵， 以上调肌联蛋白亚型并恢复舒张功能。确定的功能有效性 这些化合物将在工程心脏组织和动物模型上进行测试。第二大焦点 该提案将在HFrEF中涉及肌联蛋白。最近几项对大群患者进行的测序研究显示， 肌联蛋白基因（TTN）突变是约20%研究的扩张型心肌病（DCM）患者的病因。 许多突变是截短突变（TTNtv），它们在A带中具有优先位置 肌联蛋白片段。A带片段是肌联蛋白研究最少的部分，也是我们研究的一个重要目标 是严格检查肌节这一区域肌联蛋白的生物学， 突出。这些研究包括关注肌联蛋白在与cMyBP-C（心肌肌球蛋白结合蛋白）相互作用中的作用。 蛋白C，一种临床上重要的粗丝蛋白）。将研究动物模型，其中TTNtv具有 在肌联蛋白A带片段的不同区域引入。突变的影响将在 基线条件下，当压力，并与其他基因突变的组合发生时。 重要的是，我们还将测试切除突变的肌联蛋白外显子是否改善肌联蛋白为基础的DCM。在 总结，利用我超过20年的创新titin研究记录，并利用我们的团队， 经验丰富的科学家和有才华的受训人员，这一建议设定了雄心勃勃的目标，预计将进一步 加速了解肌联蛋白的生物学，它在心脏病中的作用，以及肌联蛋白作为一种 治疗靶点

Summary This proposal focuses on titin, the largest protein known, in heart function and disease. Titin forms a novel and multifunctional myofilament in the striated-muscle sarcomere with important roles that include regulating the diastolic stiffness of the heart. Recent breakthrough studies revealed that titin is of high clinical importance in both heart failure with preserved ejection fraction (HFpEF), and heart failure with reduced ejection fraction (HFrEF). Although significant progress has been made in understanding the basic biology of titin, major gaps in our understanding still remain, including a mechanistic understanding of how titin causes/contributes to heart disease. An important focus of this proposal will be on titin’s role in diastolic dysfunction, motivated by recent studies on patients with HFpEF that revealed deranged phosphorylation of titin’s molecular spring elements and diastolic stiffening. The full spectrum of posttranslational modifications that occur in HFpEF will be studied and high-resolution time-resolved spectroscopic techniques will focus on uncovering the structural changes in titin’s spring elements triggered by posttranslational modification. Drug screens will focus on identifying compounds that mimic or block these structural changes and functional studies will test whether newly discovered and candidate drugs ameliorate titin-based diastolic stiffening in HFpEF. Post-transcriptional mechanisms will be investigated as well, taking advantage of our recent work that has shown that splicing of titin can be manipulated to upregulate complaint titin isoforms and restore diastolic function. The functional efficacy of identified compounds will be tested on engineered heart tissues as well as on animal models. The second major focus of this proposal will be on titin in HFrEF. Several recent sequencing studies in large groups of patients revealed that mutations in the titin gene (TTN) are causative in ~20% of studied dilated cardiomyopathy (DCM) patients. Many of the mutations are truncation mutations (TTNtv) and they have a preferential location in the A-band segment of titin. The A-band segment is the least well-studied part of titin and an important goal of our research is to critically examine the biology of titin in this region of the sarcomere where disease-causing mutations are prominent. These studies include a focus on the role of titin in interacting with cMyBP-C (cardiac myosin-binding protein C, a clinically important thick filament protein). Animal models will be investigated in which TTNtv have been introduced in different regions of titin’s A-band segment. The effects of the mutations will be studied under baseline conditions, when stressed, and when occurring in combination with mutations in other genes. Importantly, we will also test whether excision of the mutated titin exons ameliorates titin-based DCM. In summary, capitalizing on my >20-year track record of innovative titin research, and utilizing our team of experienced scientists and talented trainees, this proposal sets ambitious goals that are expected to further accelerate understanding of the biology of titin, its role in heart disease and titin’s potential to function as a therapeutic target.