MUSCARINIC AND ADENOSINE RECEPTOR SIGNAL TRANSDUCTION

描述：心脏组织中的(改编自《调查者摘要》) 从副交感神经释放的乙酰胆碱通过m2受体起作用 使心跳减慢(负性变时性)并降低 收缩(负性变力)。腺苷，在心脏局部产生 作为对缺血的反应，通过A1受体产生类似的 效果。这些受体可以激活许多不同的百日咳毒素。 敏感的G蛋白直接或间接(通过第二信使) 调节离子通道(内向整流钾通道、乙酰胆碱 激活的钾通道、L型钙通道和起搏器 频道)。尽管在信号转导级联中有一些特异性 这些亚型的确切作用尚不清楚。G蛋白 在这些通路中，已有报道在心力衰竭和 百日咳毒素敏感通路在肾上腺素能降低中的作用 响应性。为了将生理功能和 激活的、靶向破坏α亚基的通路的功能 小鼠和胚胎干细胞中的基因(α-I2，α-I3，α-O)具有 已经完成了。每个阿尔法亚基的失活都有一个特定的 一些信号通路中断，但其他信号通路不中断。α-o灭活 影响L型钙电流和负性变时性，而α-I1和 α-I3阻断乙酰胆碱激活钾的激活 频道。此应用程序建议定义这些组件的特定角色 细胞内信号在心脏中级联。离子通道， 腺苷和氨基甲胆碱的变时性和变力性反应 将在基因敲除小鼠和基因敲除细胞中进一步定义刺激 台词。这些效应的机制将通过以下特征来探索 受体数量和亲和力、其他G蛋白的表达和激活 第二个信使营地。G蛋白特异性的结构基础 效应器的耦合将通过产生突变的α-o来研究。 并测试它们恢复细胞功能偶联的能力 从效应器到感受器。这些实验应该提供重要的 G蛋白信号转导的特异性研究进展 心。

DESCRIPTION: (Adapted from the Investigator's Abstract) In cardiac tissue acetylcholine liberated from parasympathetic nerves acts via the m2 receptor to slow the heart (negative chronotropy) and decrease the force of contraction (negative inotropy). Adenosine, produced locally in the heart in response to ischemia, acts through A1 receptors to produce similar effects. These receptors can activate a number of different pertussis toxin sensitive G-proteins to directly and indirectly (via second messengers) regulate ion channels (inwardly rectifying potassium channels, acetylcholine activated potassium channels, L-type calcium channels, and pacemaker channels). Although some specificity in the signal transduction cascade has been defined, the exact role of these subtypes is unclear. The G-proteins in these pathways have been reported to be up-regulated in heart failure and pertussis toxin sensitive pathways play a role in decreased adrenergic responsiveness. In order to correlate physiological function and the function of the pathways activated, targeted disruption of alpha subunit genes (alpha-i2, alpha-i3, alpha-o) in mice and in embryonic stems cell has been performed. Inactivation of each alpha subunit has a specific disruption of some signaling pathways but not others. Alpha-o inactivation affects L-type Ca current and negative chronotropy whereas alpha-i1 and alpha-i3 disrupt activation of the acetylcholine activated potassium channel. This application proposes to define the specific role of these intracellular signaling cascades in the heart. The ionic channel, chronotropic and inotropic responses ro A1 adenosine and carbachol stimulation will be further defined in knockout mice and knockout cell lines. The mechanisms for these effects will be explored by characterizing receptor number and affinity, expression of other G proteins, and activation of second messenger cAMP. The structural basis for G-protein specificity in effector coupling will be studied by the production of mutant alpha-o molecules and testing their ability to restore functional coupling of effectors to receptors. These experiments should provide important information on the specificity of signal transduction by G proteins in heart.