The function of AKAP-dependent protein-protein interactions in the regulation of vasopressin-mediated water reabsorption and cardiac myocyte contractility

A-激酶锚定蛋白(AKAPs)是一类以蛋白激酶A(PKA)和其他信号蛋白为靶标的细胞内定位蛋白，从而将相关蛋白的活性限制在细胞内特定的区域。精氨酸加压素(AVP)诱导的水通道蛋白-2(AQP2)从细胞内小泡重新分布到肾主细胞质膜上，构成了AVP介导的水重吸收的分子基础。这一过程依赖于AKAP与PKA的相互作用。依赖AKAP的蛋白质-蛋白质相互作用也促进了肾上腺素能受体诱导的心肌细胞收缩能力的增加。这些过程的失调与疾病有关，包括肾源性尿崩症和慢性心力衰竭。我们已经证实了AKAP18AVP与δ、磷酸二酯酶4D3和磷蛋白的直接相互作用，并表明它们在调节AVP介导的水重吸收和β-肾上腺素能受体引起的心肌细胞收缩能力增加中起关键作用。此外，我们还鉴定了其他新的AKAP18PKA相互作用蛋白，并发现了破坏AKAP-δ相互作用的小分子。通过使用这些分子，我们揭示了一个依赖于AKAP-PKA相互作用的负反馈回路，并终止了β-肾上腺素受体诱导的心肌细胞内cAMP的合成。然而，控制AVP介导的水重吸收和心肌细胞收缩的AKAP信号的分子细节在很大程度上是未知的。该项目的目的是从机制上深入了解AVP介导的水重吸收和心肌细胞收缩的分子机制。为了实现这一目标，我们将定义新的AKAP18δ蛋白质相互作用的功能，并确定和表征新的AKAP及其相互作用在这两个过程中的作用。此外，我们的目的是阐明负反馈调节限制肾上腺素能受体诱导的心肌细胞cAMP合成的分子机制。该项目的一个重要目标是通过对已有的和新的小分子进行药物干扰来确定新的依赖AKAP的蛋白质-蛋白质相互作用的功能。调节AKAP功能的化合物和改变分隔的细胞信号可能为治疗疾病(如肾脏疾病和慢性心力衰竭)开辟新的途径。

A-kinase anchoring proteins (AKAPs) comprise a family of scaffolding proteins that target protein kinase A (PKA) and other signaling proteins to cellular compartments and thereby confine the activities of the associated proteins to defined regions within cells. The arginine-vasopressin (AVP)-induced redistribution of aquaporin-2 (AQP2) from intracellular vesicles into the plasma membrane of renal principal cells constitutes the molecular basis of AVP-mediated water reabsorption. The process depends on interactions of AKAPs with PKA. AKAP-dependent protein-protein interactions also facilitate ß-adrenoceptor-induced increases in cardiac myocyte contractility. Dysregulation of these processes is associated with diseases, including nephrogenic diabetes insipidus and chronic heart failure. We have identified direct interactions of AKAP18δ with PKA, phosphodiesterase (PDE)4D3 and phospholamban (PLB) and have shown that they play key roles in the regulation of AVP-mediated water reabsorption and ß-adrenoceptor-induced increases in cardiac myocyte contractility. In addition, we have identified other new AKAP18δ interacting proteins, and discovered small molecules disrupting AKAP-PKA interactions. By using these molecules we have revealed a negative feedback loop which depends on AKAP-PKA interactions and terminates ß-adrenoceptor-induced cAMP synthesis in cardiac myocytes. However, the molecular details underlying AKAP-based compartmentalized signaling which controls AVP-mediated water reabsorption and cardiac myocyte contractility are largely unknown. The aim of the proposed project is to gain mechanistic insight into the molecular mechanisms controlling AVP-mediated water reabsorption and cardiac myocyte contractility. To achieve this goal, we will define the functions of the new AKAP18δ protein interactions, and we will identify and characterize the roles of new AKAPs and their interactions in the two processes. In addition, we aim to elucidate the molecular mechanisms underlying the negative feedback regulation limiting ß-adrenoceptor-induced cAMP synthesis in cardiac myocytes. An important goal of the project is to define the functions of the new AKAP-dependent protein-protein interactions by pharmacological interference with already available and novel small molecules. Chemical compounds modulating AKAP functions and altering compartmentalized cellular signaling may open new avenues for the treatment of diseases (e.g. renal diseases and chronic heart failure).