MUSCARINIC AND ADENOSINE RECEPTOR SIGNAL TRANSDUCTION

描述：（改编自研究者摘要）心脏组织 从副交感神经释放的乙酰胆碱通过M2受体起作用 减慢心脏（负变时性）并减少心脏的力量。 收缩（负性肌力）。 腺苷，在心脏局部产生 对缺血的反应，通过A1受体产生类似于 方面的影响. 这些受体可以激活多种不同的百日咳毒素 敏感G蛋白直接和间接（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 渠道）。 尽管在信号转导级联中有一些特异性， 虽然已经定义，但这些亚型的确切作用尚不清楚。 G蛋白 据报道，在心力衰竭中，这些通路中的 百日咳毒素敏感途径在肾上腺素能减少中发挥作用 响应能力。 为了将生理功能与 激活通路的功能，靶向破坏α亚单位 小鼠和胚胎干细胞中的基因（α-i2，α-i3，α-o） 被执行。 每个α亚基的失活具有特定的 一些信号通路的中断，而不是其他。 α-O失活 影响L型钙电流和负性变时性，而α-i1和 α-I3破坏乙酰胆碱激活钾的激活 频道 本申请建议定义这些 心脏内的细胞内信号级联。 离子通道， 腺苷和氨甲酰胆碱的变时和变力反应 将在敲除小鼠和敲除细胞中进一步定义刺激 线 这些影响的机制将通过表征 受体数量和亲和力，其他G蛋白的表达和活化 第二信使cAMP。 G蛋白特异性的结构基础 将通过产生突变的α-O 分子和测试它们的能力，以恢复功能耦合的 效应器到受体。 这些实验将提供重要的 G蛋白信号转导特异性的信息， 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.