Signaling Mechanisms Governing Cardiac Hypertrophy

描述（由申请人提供）：本资助的中心假设是，蛋白激酶，糖原合成酶激酶3b （GSK-3b）是心脏肥厚生长的负调节因子。在过去的几年里，我们提出了支持这一假设的证据。然而，该领域几乎所有的工作都依赖于GSK-3b的过表达，这可能导致虚假的结果。GSK-3b基因缺失导致的胚胎致死性使得这种对过表达策略的依赖成为必要。在此，我们建议使用基因功能丧失方法明确确定该激酶及其异构体GSK-3a在肥厚反应中的作用。由于我们的长期合作伙伴James Woodgett博士最近创造了GSK-3b或GSK-3a可以选择性地在心脏中有条件地删除的小鼠，这现在成为可能。因此，我们建议确定GSK-3b在三种临床相关模型中的肥厚反应中的作用：1)主动脉束带，模拟主动脉瓣疾病，2)心肌梗死，3)全身性高血压的“两肾一夹”模型。我们还将确定GSK-3a在肥厚反应中扮演什么角色，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造的有条件表达淋巴细胞增强因子-1 （left -1）的抑制性突变的小鼠，这是一种转录因子，是b-连环蛋白的专性伴侣，是GSK-3b的一个关键下游靶点，我们最近发现它调节了肥壮反应。我们将利用这只小鼠来尝试确定压力过载后表达的b-连环蛋白的新靶点，因此，可能在肥壮所必需的基因重编程中发挥作用。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厚的过程，肥厚是心力衰竭、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.