Cyclic AMP- and Ca2+-Signaling in Sensory Transduction by Olfactory Receptor Neurons

 描述(申请人提供)：本提案的长期目标是定量详细地了解嗅觉感受器神经元(ON)在感觉转导中的cAMP和钙信号。我们将集中于脊椎动物主嗅觉上皮角的典型嗅觉传导机制的问题。主要嗅觉上皮神经元的主要化学转导机制涉及cAMP信号级联，导致Na+和Ca~(2+)通过环核苷酸门控(CNG)的非选择性阳离子通道内流，使ORN去极化到放电阈值。钙离子内流通过钙离子激活的氯通道导致信号放大，并通过多条钙离子激活的负反馈通路导致嗅觉适应。最近，这些放大和负反馈途径的意义仍然受到质疑和困惑。我们建议改进和量化我们对转导过程的理解，并解决围绕信号放大和负反馈的混乱。在目标1中，我们将描述M71-单克隆鼻小鼠品系的Ons的特征，目的是将其用作本提案中许多实验的共同遗传背景。这种基因有一个明显的优势，那就是在主要的嗅觉上皮中有一个近乎同质的Ons种群，这使得实验研究变得更加有效，在某些情况下，完全可能。在目标2中，目标是在两种情况下进行详细的解剖 将总的ORN嗅觉反应的幅度和时间转化为CNG和Cl-电流成分，以确定它们在幅度和动力学上的相关性。在目标3中，我们的目标是重新检验这一假设，即通过钙激活的氯离子电流进行的钙离子介导的信号放大决定了气味检测的刺激阈值。在目标4中，我们的目标是解开关于钙离子介导的负反馈在嗅觉传导中的相关性的谜团/困惑。阐明嗅觉转导的步骤将为深入了解由转导通路中的遗传缺陷引起的嗅觉障碍提供很好的见解，在视觉方面的巨大成功充分证明了这一点。

 DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand in quantitative detail the cAMP- and Ca2+-signaling in sensory transduction by olfactory receptor neurons (ORNs). We shall focus on the question of canonical olfactory-transduction mechanism in ORNs of the vertebrate main olfactory epithelium. The major chemo-transduction mechanism in ORNs of the main olfactory epithelium involves a cAMP-signaling cascade, leading to Na+ and Ca2+ influxes through a cyclic-nucleotide-gated (CNG), non-selective cation channel to depolarize the ORN to firing threshold. The Ca2+ influx leads to signal amplification via a Ca2+-activated Cl channel, as well as olfactory adaptation via multiple Ca2+-activated negative-feedback pathways. Recently, the significance of these amplification and negative-feedback pathways is nonetheless thrown into doubt and confusion. We propose to refine and quantify our understanding of the transduction process and to resolve the confusion surrounding the signal amplification and negative feedbacks. In Aim 1, we shall characterize the ORNs from the M71-monoclonal-nose mouse line, with the objective of using it as the common genetic background for many of the experiments in this proposal. This genotype offers the distinct advantage of having a near-homogeneous population of ORNs in the main olfactory epithelium, making experimental investigations much more efficient, and, in some cases, exclusively possible. In Aim 2, the objective is to carry out a detailed dissection, in both amplitude and time, of the overall ORN olfactory response into its CNG and Cl- current components for determining their correlations in amplitude and kinetics. In Aim 3, our goal is to re-examine the hypothesis that the Ca2+-mediated signal amplification via the Ca2+-activated Cl- current dictates the stimulus threshold for odorant detection. In Aim 4, our objective is to resolve the mystery/confusion about the relevance of the Ca2+-mediated negative feedbacks in olfactory transduction. Elucidating the steps of olfactory transduction will provide great insight into olfactory malfunctions arising from genetic defects in the transduction pathway, as amply demonstrated by the huge success in the case of vision.