mAKAP-orchestrated phosphorylation events: regulation of PDE4D3

描述（由申请人提供）：cAMP是调节心脏收缩、代谢和基因转录等多种生理事件的重要第二信使。最近的几项研究表明，磷酸二酯酶（PDE）不仅在控制心脏基础cAMP水平方面具有重要作用，而且由于PDE的细胞定位而调节cAMP的局部变化。因此，确定控制PDE定位和活性的分子决定因素，以及归因于每个PDE的生物过程，将进一步加深我们对心脏cAMP信号传导的了解。我们之前已经描述了一种支架蛋白，它将磷酸二酯酶PDE4D3分离到分化的心肌细胞的核包膜上。a激酶锚定蛋白mAKAP维持着一个由camp依赖性蛋白激酶PDE4D3、Map激酶ERK5、鸟嘌呤核苷酸交换因子Epac、蛋白磷酸酶2A和Ryanodine受体组成的复合物。先前的数据显示，mAKAP协调了ERK5和PKA对PDE4D3的调控。这些磷酸化诱导的PDE4D3活性变化反过来会调节复合物周围cAMP的浓度，最终调节复合物中所有cAMP效应物，即PKA、PDE4D3和Epac。本提案的三个具体目标将试图：1)阐明调节PDE4D3磷酸化的生理事件，调节cAMP浓度和Ryanodine受体的磷酸化状态2)确定PDE4D3磷酸化对epac介导的ERK5活性和ERK5介导的心脏肥大的功能后果，以及3)确定控制PDE去磷酸化的复合物中的磷酸酶。心脏病是美国的头号死因。心脏肥厚是心脏对持续增加的心输出量的需求作出反应的主要代偿机制。最终，心脏肥厚导致心脏疾病的发展和心力衰竭。然而，一些研究表明，抑制心脏肥厚可降低死亡和进展为心力衰竭的风险。这项研究将进一步加深我们对心肌肥厚分子机制的理解，并有助于确定药物设计的新靶点，以帮助治疗肥厚。

DESCRIPTION (provided by applicant): cAMP is an important second messenger that regulates several physiological events in the heart including contraction, metabolism and gene transcription. Several recent studies have illustrated not only the importance of phosphodiesterases (PDE) for the control of basal cAMP levels in the heart, but also in the regulation of localized changes of cAMP due to the cellular location of PDEs. Therefore, identifying the molecular determinants governing PDE localization and activity, as well as the biological processes attributed to each PDE, will further our knowledge of cAMP signaling in the heart. We have previously described a scaffolding protein that sequesters the phosphodiesterase PDE4D3 to the nuclear envelope in differentiated cardiac myocytes. The A-Kinase Anchoring Protein mAKAP maintains a complex consisting of the cAMP-dependent protein kinase, PDE4D3, the Map Kinase ERK5, the guanine nucleotide exchange factor Epac, the protein phosphatase 2A, and the Ryanodine Receptor. Previous data has shown mAKAP orchestrated both ERK5 and PKA regulation of PDE4D3. These phosphorylation-induced changes in PDE4D3 activity will in turn modulate the concentration of cAMP surrounding the complex, ultimately regulating all cAMP effectors in the complex, namely PKA, PDE4D3 and Epac. The three Specific Aims of this proposal will try to 1) elucidate the physiological events that regulate PDE4D3 phosphorylation regulate cAMP concentration and the phosphorylation state of the Ryanodine Receptor 2) determine the functional consequence of PDE4D3 phosphorylation on Epac-mediated ERK5 activity and ERK5-mediated cardiac hypertrophy, and 3) identify the phosphatase in the complex that governs dephosphorylation of the PDE. Heart disease is the number one cause of death in the United States. Cardiac hypertrophy is the major compensatory mechanism by which the heart responds to a continued, increased demand for cardiac output. Ultimately, cardiac hypertrophy leads to progression into cardiac disease and to heart failure. However, several studies have shown that inhibition of cardiac hypertrophy lowers the risk of death and progression into heart failure. This study will further our understanding of the molecular mechanism of cardiac hypertrophy and help to identify novel targets for drug design to aid in the treatment of hypertrophy.