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改变在肥厚心肌的收缩功能障碍中是否起作用。重要的成就是1）从肥厚和失败的RV和LV中的心细胞中基于微管的收缩功能障碍的证明持续增加，5）证明微管是如此受影响的唯一主要的细胞外细胞骨骼蛋白，6）发现这种现象既基于微管蛋白，因此是基于微管的增加，也是基于曾经形成的微管的稳定性，7） 主要心脏微管稳定蛋白在压力超负荷中明显上调 肥大和8）发现在肥大期间，两个次要β-纤维蛋白同工型的转录上调上调，我们发现这些基因的发育调节是β-微管蛋白的增加。提出的工作的第一个目标是使用具有心脏限制性突变β-微管蛋白表达的转基因小鼠，从而导致微管稳定性降低或提高，以直接测试增强的微管网络稳定性的假设，从而导致收缩性功能障碍时，当这些心脏微管发生这些变化时，会导致微管的肌肉无磷酸化。第一个目标本身将直接关注微管稳定性，而没有肥厚性心脏环境的许多随之复杂性。第二个目标是在压力超负荷肥大的手术模型中，在具有MAP4的心脏限制表达的转基因小鼠中 在具有腺病毒介导的MAP4表达的孤立心细胞中 微管网络的稳定性和密度就MAP4的微管亲和力增加而言，MAP4是心脏的主要微管相关蛋白。由于我们发现肥大中的MAP4表达增加，并且我们刚刚发现该MAP4被脱磷酸化，从而增加了MAP4-微管亲和力，因此第二个目标将集中在肥厚的MAP4去磷酸化机制上。