MAP4 REGULATION OF CARDIAC MICROTUBULE NETWORK DENSITY

描述（由申请人提供）： 我们已经在离体细胞、离体组织和完整心脏的水平上表明，微管网络密度增加是高室壁应力右室或左室肥厚收缩功能障碍的原因之一。然后，我们发现微管相关蛋白4 [MAP4]对微管的亲和力增加是肥大相关微管网络稳定和致密化的主要决定因素，从而导致收缩功能障碍和基于微管的细胞内运输的相关缺陷，我们也在此背景下进行了描述。MAP4磷酸化状态似乎决定了MAP4对微管的亲和力。因此，本申请旨在表征病理性压力超负荷肥大动物模型中位点特异性MAP 4磷酸化状态的持续变化，同时将生理性容量超负荷肥大的平行模型用作生长本身任何影响的对照。然后，我们将描绘的MAP 4磷酸化的调节，通过检查相关的激酶和磷酸酶。我们相信，拟议研究的成功执行可能会产生重要的新信息，以帮助理解心脏肥厚和衰竭的细胞和分子机制。此外，虽然我们自己感兴趣的终点是微管，但我们的初步数据显示，心脏磷酸酶活性及其调节的持续增加几乎肯定对已建立的肥大和衰竭相关疾病机制具有更普遍的重要性，其中许多涉及肌浆网、肌原纤维、和肌丝外细胞骨架。因此，这项工作可以作为一个例子，以帮助概念化可能的机械收敛的一些迄今为止明显不同的异常肥厚和衰竭的心脏。 公共卫生相关性： 充血性心力衰竭是65岁或以上美国人入院和再入院的主要原因。收缩功能障碍是收缩性心力衰竭的特征，是对几种病理挑战（包括持续的心脏压力超负荷）的适应不良的心肌反应。这项研究将确定在衰竭的心脏中这种功能障碍的一个重要原因的机制：心肌细胞细胞骨架微管网络的改变。

DESCRIPTION (provided by applicant): We have shown at the levels of isolated cell, isolated tissue and the intact heart in vivo that increased microtubule network density is one cause of contractile dysfunction in high wall stress right or left ventricular hypertrophy. We then showed that increased affinity of microtubule-associated protein 4 [MAP4] for microtubules is the primary determinant of hypertrophy-related microtubule network sta- bilization and densification, and is thereby responsible for both the contractile dysfunction and associ- ated defects in microtubule-based intracellular trafficking that we have also described in this setting. MAP4 phosphorylation status appears to determine MAP4 affinity for microtubules. Therefore, this application intends to characterize the persistent changes in site-specific MAP4 phosphorylation status in an animal model of pathological pressure overload hypertrophy, with a parallel model of physiologi- cal volume overload hypertrophy serving as a control for any effects of growth per se. We will then delineate the regulation of MAP4 phosphorylation by examining relevant kinases and phosphatases. We believe that the successful execution of the proposed research will likely generate important new information to help understand the cellular and molecular mechanisms underlying cardiac hypertro- phy and failure. In addition, while our own end point of interest is the microtubule, the persistent increase in cardiac phosphatase activity and its regulation as shown in our preliminary data is almost certainly of more general importance to established hypertrophy- and failure-related disease mecha- nisms, many of which involve phosphorylation-dependent alterations of structural and regulatory pro- teins of the sarcoplasmic reticulum, the myofibril, and the extra-myofilament cytoskeleton. Thus, this work may serve as an example to help conceptualize the likely mechanistic convergence of a number of heretofore apparently disparate abnormalities of the hypertrophied and failing heart. PUBLIC HEALTH RELEVANCE: Congestive heart failure is the leading cause of hospital admission and readmission in Americans aged 65 or greater. The contractile dysfunction that characterizes systolic heart failure is a maladaptive myo- cardial response to several pathological challenges, including sustained cardiac pressure overloading. This study will identify the mechanism underlying one important cause for this dysfunction in the failing heart: alterations in the microtubule network of the cardiac muscle cell cytoskeleton.