Deciphering the role of Lmod2 in thin filament length regulation and dilated cardiomyopathy

解读 Lmod2 在细丝长度调节和扩张型心肌病中的作用

• 批准号: 9039137
• 负责人: Carol C Gregorio
• 金额: $ 44.24万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9039137
• 关键词: Actin-Binding Protein; Actins; Architecture; Biological Markers; Birth; Cardiac; Cardiac Myocytes; Cardiac development; Cardiomyopathies; Complex; Data; Defect; Dilated Cardiomyopathy; Disease; Disease Progression; Early Diagnosis; Elongation Factor; Exhibits; Family member; Filament; Functional disorder; Genetic Models; Goals; Health; Heart; Heart Abnormalities; Human; Knock-out; Knockout Mice; Laboratories; Lead; Length; Link; Mammalian Cell; Mammals; Measures; Microfilaments; Minus End of the Actin Filament; Mus; Muscle; Muscle Cells; Muscle Development; Muscle function; Myocardium; Phosphorylation; Play; Protein Array; Proteins; Regulation; Role; Sampling; Striated Muscles; Structural defect; Structure; Thick Filament; Thin Filament; Tissues; Transduction Gene; Transgenic Mice; Transgenic Organisms; Ventricular Dysfunction; Viral; Work; combinatorial; genetic regulatory protein; heart function; human tissue; improved; in vivo; insight; interdisciplinary approach; knock-down; mouse model; multidisciplinary; muscle LIM protein; new therapeutic target; novel; novel therapeutics; overexpression; pre-clinical; protein function; research study; single molecule; therapeutic target

 DESCRIPTION (provided by applicant): The mechanism whereby cardiomyocytes precisely regulate the assembly of their actin-containing thin filaments at the level of single molecules is still largely unknown. We have discovered that Leiomodin 2 (Lmod2), a striated muscle specific actin-binding protein, functions as the first described actin filament pointed- end elongation factor in mammals. Little is known, however, regarding the function of Lmod2 in the heart. Preliminary analysis of our unique Lmod2 knockout (KO) mice reveal that they die ~3 weeks following birth, with hearts displaying severe contractile dysfunction and ventricular chamber enlargement, consistent with dilated cardiomyopathy (DCM). Strikingly, Lmod2 KO hearts have shorter thin filaments. When we analyzed human heart samples with DCM and hearts from multiple mouse models of DCM we discovered that they too have shorter thin filaments. Remarkably, when DCM was "rescued" in the hearts of a well-studied mouse model of DCM (muscle LIM protein (MLP) knockout mice), proper thin filament lengths were restored. We hypothesize that thin filament length changes are a general mechanism of the complex remodeling that occurs in DCM. The long-term goal of the proposed work is to discover common pathophysiologies of dilated hearts that can be used as therapeutic targets for the treatment of DCM. The immediate goals of this proposal are to determine mechanisms by which actin-thin filament architecture is regulated in cardiac muscle, the role Lmod2 plays in this regulation, and how defects in this regulation contribute to DCM. Using novel transgenic mice (with either abnormally long or short thin filaments), human muscle samples and primary cardiomyocytes, we will take a multidisciplinary approach to accomplish three Specific Aims focused on determining: 1) the effect loss of Lmod2 has on cardiac development and function; 2) the mechanism by which Lmod2 functions to elongate thin filaments; and 3) the role thin filament length dysregulation plays in cardiomyopathies, and whether heart function and remodeling can be rescued if thin filament regulation is restored in a dilated heart in vivo. We predict that completion of this project will result in the discovery of one critical general mechanism and a novel structural biomarker (i.e., thin filament length dysregulation) of the complex remodeling seen in DCM. These discoveries will potentially facilitate early detection of DCM and lead to new therapeutic options.

 描述（由申请人提供）：心肌细胞在单分子水平上精确调节其含有肌动蛋白的细丝的组装的机制仍然很大程度上未知。我们发现 Leiomodin 2 (Lmod2) 是一种横纹肌特异性肌动蛋白结合蛋白，在哺乳动物中充当第一个描述的肌动蛋白丝尖端伸长因子。然而，人们对 Lmod2 在心脏中的功能知之甚少。对我们独特的 Lmod2 敲除 (KO) 小鼠的初步分析表明，它们在出生后约 3 周死亡，心脏表现出严重的收缩功能障碍和心室扩大，与扩张型心肌病 (DCM) 一致。引人注目的是，Lmod2 KO 心脏的细丝更短。当我们分析具有 DCM 的人类心脏样本和来自多个 DCM 小鼠模型的心脏时，我们发现它们也具有较短的细丝。值得注意的是，当 DCM 在经过充分研究的 DCM 小鼠模型（肌肉 LIM 蛋白 (MLP) 敲除小鼠）的心脏中得到“拯救”时，适当的细丝长度得到了恢复。我们假设细丝长度变化是 DCM 中发生的复杂重塑的一般机制。 这项工作的长期目标是发现扩张心脏的常见病理生理学，这些病理生理学可用作 DCM 的治疗靶点。该提案的直接目标是确定心肌中肌动蛋白细丝结构的调节机制、Lmod2 在这种调节中发挥的作用，以及这种调节的缺陷如何导致 DCM。使用新型转基因小鼠（具有异常长或短的细丝）、人类肌肉样本和原代心肌细胞，我们将采取多学科方法来实现三个具体目标，重点是确定：1​​）Lmod2 缺失对心脏发育和功能的影响； 2) Lmod2 延长细丝的机制； 3）细丝长度失调在心肌病中所起的作用，以及如果在体内扩张的心脏中恢复细丝调节是否可以挽救心脏功能和重塑。 我们预测，该项目的完成将导致发现 DCM 中复杂重塑的一个关键的一般机制和一个新的结构生物标志物（即细丝长度失调）。这些发现将有可能促进 DCM 的早期检测并带来新的治疗选择。