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

 描述（由申请人提供）：本提案的长期目标是定量详细了解嗅觉受体神经元（ORN）感觉转导中的cAMP-和Ca 2 +-信号传导。我们将集中在脊椎动物的主要嗅觉上皮的ORN的典型嗅觉转导机制的问题。主要嗅觉上皮的ORN中的主要化学转导机制涉及cAMP信号级联，导致Na+和Ca 2+通过环状核苷酸门控（CNG）、非选择性阳离子通道流入，以将ORN降低到放电阈值。Ca 2+内流导致通过Ca 2+激活的Cl通道的信号放大，以及通过多个Ca 2+激活的负反馈途径的嗅觉适应。最近，这些放大和负反馈途径的重要性仍然受到怀疑和混淆。我们建议完善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，我们将表征来自M71-单克隆鼻小鼠系的ORN，目的是将其用作本提案中许多实验的共同遗传背景。这种基因型提供了一个独特的优势，在主要的嗅觉上皮中有一个接近同质的ORN群体，使实验研究更有效，在某些情况下，完全可能。在目标2中，目标是进行详细的解剖， 的振幅和时间，整体ORN嗅觉响应到其CNG和Cl-电流分量，以确定其在振幅和动力学的相关性。在目标3中，我们的目标是重新检查的假设，通过Ca 2+激活的Cl-电流的Ca 2+介导的信号放大支配的刺激阈值的气味检测。在目标4中，我们的目标是解决嗅觉转导中Ca 2+介导的负反馈相关性的谜团/困惑。阐明嗅觉传导的步骤将提供对由传导途径中的遗传缺陷引起的嗅觉功能障碍的深入了解，正如视觉方面的巨大成功所充分证明的那样。

 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.