Myocardial Adenosine Receptors

说明(申请人提供)：已知心肌中的腺苷受体在正常心脏和疾病心脏的心功能中发挥重要作用。该实验室以前的研究主要集中在刺激这些受体时所引起的细胞反应。此外，已经开始研究受体信号如何在心脏中转化为细胞反应。然而，关于诱发反应和心脏腺苷受体之间的交叉调节的详细机制，人们知之甚少。我们和其他人已经报道，腺苷A1受体(A1R)、腺苷A2a受体(A2AR)和β1肾上腺素能受体(？1R)的刺激在心室肌细胞中产生一系列的效应。A1R具有重要的抗肾上腺素能作用，A2AR引起正性变力反应。此外，A2AR共同减弱A1-R介导的抗肾上腺素能作用。然而，有关腺苷受体信号转导机制以及A1R和A2AR相互作用的分子事件，包括腺苷A3受体(A3R)，目前知之甚少。因此，本项目的目标将是确定A1R、A2AR和A3R介导的心脏活动中涉及蛋白激酶和磷酸酶的分子信号转导机制。此外，还将确定这些腺苷受体在调节心脏机械和代谢功能中的作用。利用大鼠和A1R、A2AR和双(A1R A2AR)基因敲除小鼠的心室肌细胞、心肌细胞膜和灌流心脏，拟议的研究将揭示：1)A1R刺激是否导致蛋白激酶C亚型移位并与心肌肌膜的RAK(受体激活的C激酶)蛋白结合。此外，还将探讨p38-MAPK(丝裂原激活蛋白激酶)是否参与A1 R介导的抗肾上腺素能作用，2)A3R刺激引起的抗肾上腺素能作用的重要性以及PKC亚型是否参与，3)A2AR抑制A1R介导的心脏抗肾上腺素能作用的方式，4)蛋白磷酸酶在A1R、A2AR和A3R刺激产生的心脏效应中的作用和重要性，以及5)心肌缺氧和/或缺血如何改变A1 R、A2AR和/或A3R的功能，从而增加或减少它们在调节心功能中的作用。这些研究的结果将提供有关心肌中腺苷受体分子功能的新信息。此外，这些发现将大大有助于我们了解G蛋白偶联受体在正常和疾病心脏中运行的分子机制。这些信息应该有助于开发新的治疗方法和药物来缓解心脏功能障碍。

DESCRIPTION (provided by applicant): Adenosine receptors in the myocardium are known to play an important role in cardiac function in both the normal and diseased heart. Prior studies in this laboratory have focused on the cellular responses elicited upon stimulation of these receptors. In addition studies have been initiated to investigate how the receptor signals are translated into cellular responses in the heart. However, little is known regarding the details of the mechanisms involved in the elicited responses and the cross-regulation between cardiac adenosine receptors. We and others have reported that adenosine A1 receptor (A1R), adenosine A2A receptor (A2AR) and ?1 adrenergic receptor (?1 R) stimulation results in a number of effects in ventricular myocytes. The A1R serves an important antiadrenergic action, and the A2AR causes a positive inotropic response. Furthermore, together, the A2AR attenuates the A1 R-mediated antiadrenergic actions. However, little is known about the molecular events involved in adenosine receptor signal transduction mechanisms and interaction of the A1R and A2AR including the adenosine A3 receptor (A3R). Thus, the objective of this project will be to determine the molecular signal transduction mechanisms involving protein kinases and phosphatases in the A1R-, A2AR- and A3R-mediated actions in the heart. In addition the operation of these adenosine receptors in regulating cardiac mechanical and metabolic function will be determined. Using rat and A1 R, A2AR and double (A1R+A2AR) knockout mice ventricular myocytes, myocyte membranes and perfused hearts, the proposed studies should reveal: 1) Whether A1R stimulation causes protein kinase C isoforms to translocate and bind to RACK (receptor activated C kinase) proteins of the myocardial sarcolemma. Also the involvement of p38-MAPK (mitogen activated protein kinase) in the A1 R-mediated antiadrenergic action will be investigated, 2) The importance of the antiadrenergic action resulting from A3R stimulation and whether PKC isoforms are involved, 3) The way in which A2AR inhibits A1R mediated cardiac antiadrenergic actions, 4) The effect and importance of protein phosphatases in the cardiac effects produced by A1R, A2AR and A3R stimulation, and 5) How myocardial hypoxia and/or ischemia modifies the function of A1 R, A2AR and/or A3R, thereby increasing or reducing their roles in modulating heart function. The results obtained from these studies will provide new information regarding the molecular functioning of adenosine receptors in the myocardium. Additionally, the findings should significantly contribute to our knowledge of the molecular mechanisms of G- protein coupled receptor operation in the normal and diseased heart. Such information should be instrumental for the development of new therapies and agents to alleviate cardiac dysfunction.