CYTOSKELETON AND CONTRACTILE DYSFUNCTION IN HYPERTROPHY

肥大症中的细胞骨架和收缩功能障碍

• 批准号: 6808267
• 负责人: GEORGE COOPER
• 金额: $ 16.55万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6808267
• 关键词: Adenoviridae; G protein; beta adrenergic receptor; beta adrenergic receptor kinase; cats; cell growth regulation; cellular pathology; gene expression; genetically modified animals; heart cell; heart enlargement; heart function; intracardiac pressure; laboratory mouse; microtubule associated protein; microtubules; myocardium; pathologic process; phosphoprotein phosphatase; receptor binding; sarcomeres; transfection; tubulin; ventricular hypertrophy

The initial goal of this project was to determine whether cytoskeletal alterations have any role in the contractile dysfunction of hypertrophied myocardium. Important accomplishments have been 1) the demonstration of microtubule-based contractile dysfunction in cardiocytes from the hypertrophied and failing RV and LV, 2) extension of these findings to isolated tissue and to the intact heart, 3) biophysical characterization of the etiology of microtubule-based contractile dysfunction, 4) the finding that this mechanism is tightly restricted to pressure overload hypertrophy in which wall stress is persistently increased, 5) the demonstration that microtubules are the only major extra-myofilament cytoskeletal protein so affected, 6) the finding that this phenomenon is based both on increased tubulin, and thus microtubules, and on increased stability of the microtubules once formed, 7) the finding that MAP4, the major cardiac microtubule-stabilizing protein, is markedly upregulated in pressure overload hypertrophy, and 8) the finding that transcriptional upregulation of two minor beta -tubulin isoforms during hypertrophy, which we found to mimic the developmental regulation of these genes, accounts for the increase in beta-tubulin. The first goal for the work proposed is to use transgenic mice having cardiac-restricted expression of mutant beta-tubulins that cause reduced or increased microtubule stability in order to directly test the hypothesis that enhanced microtubule network stability and thus density cause contractile dysfunction when these alterations of cardiocyte microtubules occur in hypertrophied myocardium. This first goal will focus directly on microtubule stability per se, absent the many attendant complexities of the hypertrophic cardiac environment. The second goal is to seek in surgical models of pressure overload hypertrophy, in transgenic mice having cardiac-restricted expression of MAP4, and in isolated cardiocytes with adenovirus-mediated expression of MAP4 the basis for increased microtubule network stability and density in terms of increased microtubule affinity of MAP4, the major microtubule-associated protein of the heart. Since we have found increased MAP4 expression in hypertrophy, and we have just discovered that this MAP4 is dephosphorylated, thus increasing MAP4 -microtubule affinity, this second goal will focus on the mechanisms of hypertrophic MAP4 dephosphorylation.

该项目的最初目标是确定细胞骨架的改变是否在肥厚心肌的收缩功能障碍中发挥作用。重要的成就是 1) 证明了肥厚和衰竭的右心室和左心室心肌细胞中基于微管的收缩功能障碍，2) 将这些发现扩展到分离的组织和完整的心脏，3) 基于微管的收缩功能障碍的病因学的生物物理特征，4) 发现这种机制严格限于压力超负荷肥大，其中壁应力是 持续增加，5）证明微管是唯一受到如此影响的主要肌丝外细胞骨架蛋白，6）发现这种现象既基于微管蛋白的增加，因此微管，也基于微管一旦形成的稳定性增加，7）发现MAP4， 主要的心脏微管稳定蛋白，在压力超负荷时显着上调 8）发现肥大期间两种次要β-微管蛋白亚型的转录上调，我们发现这模仿了这些基因的发育调节，解释了β-微管蛋白的增加。这项工作的第一个目标是使用具有心脏限制性表达的突变型β-微管蛋白的转基因小鼠，这些突变型β-微管蛋白会导致微管稳定性降低或增加，以便直接测试这样的假设：当心肌细胞微管的这些改变发生在肥厚的心肌中时，增强的微管网络稳定性和密度会导致收缩功能障碍。第一个目标将直接关注微管稳定性本身，而不考虑肥厚心脏环境的许多随之而来的复杂性。第二个目标是在心脏 MAP4 表达受限的转基因小鼠中寻找压力超负荷肥大的手术模型，以及 在分离的心肌细胞中，腺病毒介导的 MAP4 表达增加 微管网络的稳定性和密度，即增加 MAP4（心脏的主要微管相关蛋白）的微管亲和力。由于我们发现肥大中 MAP4 表达增加，并且我们刚刚发现该 MAP4 被去磷酸化，从而增加了 MAP4 微管亲和力，因此第二个目标将集中于肥大 MAP4 去磷酸化的机制。