Signaling Mechanisms Governing Cardiac Hypertrophy

描述（由申请人提供）：本授权的中心假设是蛋白激酶，糖原合成酶激酶-3b（GSK-3b）是心脏肥大性生长的负调节因子。在过去的几年里，我们提出了支持这一假设的证据。然而，几乎所有在这一领域的工作都依赖于GSK-3b的过表达，这可能导致虚假的结果。由于GSK-3b基因缺失导致的胚胎致死性，这种对过表达策略的依赖是必要的。在此，我们建议明确确定这种激酶及其亚型GSK-3a在肥大反应中的作用，使用遗传功能丧失的方法。由于我们的长期合作者James Woodgett博士最近创造了一种小鼠，其中GSK-3b或GSK-3a可以在心脏中选择性地有条件地删除。因此，我们建议确定GSK-3b在对三种临床相关模型的肥大反应中的作用：1）主动脉的带状，模仿主动脉瓣疾病，2）心肌梗死，和3）全身性高血压的“两肾一夹”模型。我们还将确定GSK-3a在肥大反应中所起的作用（如果有的话）-据我们所知，这是一个完全未知的领域。最后，我们将利用我们最近创建的小鼠，该小鼠有条件地表达淋巴细胞增强因子-1（Lef-1）的抑制性突变体，Lef-1是一种转录因子，是b-连环蛋白的专性伴侣，b-连环蛋白是我们最近发现调节肥大反应的GSK-3b的关键下游靶标。我们将利用这只小鼠来尝试鉴定在压力超负荷后表达的β-连环蛋白的新靶点，因此，这可能在肥大所必需的遗传重编程中发挥作用。我们相信本文概述的研究可以确定新的靶点，抑制这些靶点可以延缓或逆转肥大的过程，肥大是心力衰竭、中风和心肌梗死的主要危险因素。

DESCRIPTION (provided by applicant): It is the central hypothesis of this grant that the protein kinase, glycogen synthase kinase-3b (GSK-3b) is a negative regulator of hypertrophic growth of the heart. Over the past several years we have presented evidence to support that hypothesis. However, virtually all of the work in this area has relied upon over-expression of GSK-3b, and this can cause spurious results. This reliance on over-expression strategies has been necessitated by the embryonic lethality caused by deletion of the GSK-3b gene. Herein, we propose to definitively determine the role of this kinase and its isoform, GSK-3a, in the hypertrophic response using genetic loss of function approaches. This is now possible due to the recent creation by our long-time collaborator, Dr. James Woodgett, of mice in which either GSK-3b or GSK-3a can be conditionally deleted, selectively in the heart. Thus we propose to determine the role of GSK-3b in the hypertrophic response to three clinically relevant models: 1) banding of the aorta, mimicking aortic valve disease, 2) myocardial infarction, and 3) the "two-kidney one clip" model of systemic hypertension. We will also determine what role, if any, GSK-3a plays in hypertrophic responses- an area that is, to our knowledge, totally unexplored. Finally, we will make use of a mouse we have recently created that conditionally expresses an inhibitory mutant of lymphocyte enhancer factor-1 (Lef-1), a transcription factor that is an obligate partner of b-catenin, a key downstream target of GSK-3b that we have recently found regulates the hypertrophic response. We will employ this mouse to attempt to identify novel targets of b-catenin that are expressed following pressure overload and that, therefore, might play a role in the genetic re-programming that is necessary for hypertrophy. We believe the studies outlined herein could identify novel targets, inhibition of which could retard or reverse the process of hypertrophy, a major risk factor for heart failure, stroke, and myocardial infarction.