BETA ADRENERGIC SIGNALING IN NEONATAL AND ADULT MYOCYTES

我们实验室最近的研究发现，以前没有人认识到 心脏β-肾上腺素能受体亚型信号转导的复杂性 深刻的发育变化效应器的β/2受体激活 机械装置。至少有两个方面的β受体亚型信号可以 不能在受体的传统概念的背景下解释- 激活的信号通路：[1]β/2受体的观察 仅在新生(成人)心肌细胞中增加cAMP积聚。 [2]新生儿个体β受体亚型的观察 心肌细胞对抑制物表现出不同的敏感性 M胆碱能激动剂的作用。为了试图理解 在测试版中，这些耐人寻味的复杂性背后的机制- 受体亚型信号传递，该项目更新中的研究将 应用与组分的分子非均质性相关的新概念 β受体亚型信号级联(G蛋白亚基，腺苷 环化酶同工酶和PKA酶的组成)以及概念 第二信使分子到小窝的区隔 (作为‘信号处理’的专门的膜亚域 中心‘)用于促进和/或限制受体信号传递事件。 前两个特定目标将阐明分子和/或细胞 β-肾上腺素能受体亚型信号转导差异的基础 新生儿和成人的心肌细胞。第三个具体目标将建立 根据我们最近令人兴奋的观察，β/2受体影响 成人心肌细胞通过cAMP非依赖性信号途径收缩 导致依赖于HCO/3的细胞内碱化的途径 研究β受体亚型对pH/I的调节作用。第四个具体问题 Aim将检验交感神经影响 β/2受体作用。这些研究将结合广泛的 生化/分子技术，离子荧光显微镜- 灵敏的探头和空载电池缩短的测量；这 允许分析细胞内信号的功能作用 β受体亚型反应性的中间体。通过考虑 调节心肌细胞自主神经的新信号转导机制 在正常生长、发育和/或同情的背景下的反应 脑室的神经支配，该项目的研究将有助于 该计划的长期目标是了解结构， 分子、生化和/或离子决定因素导致不同的 大鼠儿茶酚胺依赖的电生理和收缩反应 新生儿和成人心脏。

Recent studies from our laboratory identify previously unappreciated complexities in cardiac beta-adrenergic receptor subtype signaling, with profound developmental changes beta/2-receptor activation of effector mechanisms. At least two aspects of beta-receptor subtype signaling can not be explained in the context of traditional concepts of receptor- activated signaling pathways: [1] The observation that beta/2-receptors increase cAMP accumulation only in neonatal (not in adult) cardiomyocytes. [2] The observation that individual beta-receptor subtypes in neonatal cardiomyocytes display differential susceptibility to the inhibitory effects of muscarinic cholinergic agonists. In an attempt to understand the mechanisms that underlie these intriguing complexities in beta- receptor subtype signaling, studies in the renewal of this Project will apply newer concepts related to molecular heterogeneity of components of beta-receptor subtype signaling cascades (G protein subunits, adenylyl cyclase isoforms, and components of the PKA enzyme) as well as the concept that compartmentalization of second messenger molecules to caveolae (specialized membrane subdomains that serve as 'signaling processing center') serves to facilitate and/or restrict receptor signaling events. The first two Specific Aim will elucidate the molecular and/or cellular basis for differences in beta-adrenergic receptor subtype signaling in neonatal and adult ventricular myocytes. The third Specific Aim will build upon our exciting recent observation that beta/2-receptors influence contraction in adult ventricular myocytes via a cAMP-independent signaling pathway leading to HCO/3-dependent intracellular alkalinization to investigate pH/i-regulation by beta-receptor subtypes. The fourth Specific Aim will test the hypothesis that sympathetic innervation influence beta/2-receptor action. These studies will combine a broad range of biochemical/molecular techniques, fluorescence microscopy with ion- sensitive probes, and measurements of unloaded cell shortening; this permits an analysis of the functional role of intracellular signaling intermediates in beta-receptor subtype responsiveness. By considering novel signal transduction mechanisms that regulate cardiomyocyte autonomic responses in the context of normal growth, development, and/or sympathetic innervation of the ventricle, studies in this Project will contribute to the Program's long-range goal, which is to understand the structural, molecular, biochemical, and/or ionic determinants that lead to distinct catecholamine-dependent electrophysiologic and contractile responses in newborn and adult hearts.