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

嗅觉受体神经元感觉转导中的环 AMP 和 Ca2 信号传导

• 批准号: 10443371
• 负责人: KING-WAI YAU
• 金额: $ 40.94万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-01 至 2027-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10443371
• 关键词: Acetophenones; Address; Adenylate Cyclase; Binding; Biochemical; Cations; Cellular biology; Chemoreceptors; Cilia; Complex; Confusion; Cyclic AMP; Cyclic GMP; Cyclic Nucleotides; Feedback; G Protein-Coupled Receptor Signaling; G-Protein-Coupled Receptors; GTP-Binding Protein alpha Subunits, Gs; GTP-Binding Proteins; Golf; Hand; Laboratories; Lead; Ligands; Light; Mediating; Membrane; Molecular; Molecular Biology; Multienzyme Complexes; Mus; Mutation; Nose; Odorant Receptors; Olfactory Epithelium; Olfactory Receptor Neurons; Pathway interactions; Performance; Phenethylamines; Phototransduction; Probability; Rhodopsin; Rod; Sensory; Signal Transduction; Suction; Suggestion; Surface; Transducin; Uncertainty; Ursidae Family; Vertebrate Photoreceptors; Work; adenylyl cyclase III; density; experimental study; genetic manipulation; insight; mathematical model; phosphoric diester hydrolase; receptor; retinal rods; success

The long-term objective of this proposal is to understand in quantitative detail the cAMP- and Ca2+-signalings in sensory transduction by olfactory receptor neurons (ORNs). We shall focus on the canonical olfactory-transduction mechanism in the vertebrate main olfactory epithelium. This mechanism 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 an inward Ca2+-activated Cl current, as well as olfactory adaptation via multiple Ca2+-activated negative-feedback pathways. Recently, however, the significance and performance of the negative-feedback pathways are thrown into doubt and confusion. In Aim 1, we propose to re-examine this question and to settle it once and for all. Most recently, by using M71-monoclonal-nose mouse ORNs, we have succeeded in quantifying the density of M71-OR molecules on the olfactory cilia membrane. We also found that an M71-OR, when liganded with acetophenone (among the most efficacious odorants for M71-OR), nonetheless still has a very low probability of success (nominally ~10-4) in activating a single downstream Golf/adenylyl cyclase III effector complex. This low probability is very different from the situation in rod phototransduction, about which we recently showed that one photoexcited rhodopsin activates 10-20 rod transducin/cGMP-phosphodiesterase effectors. Thus, a ligand-activated GPCR pathway may be quite different in signal amplification from a light-activated GPCR pathway. In Aims 2, we propose to study another mouse nasal chemoreceptor, TAAR4, which is exceedingly sensitive to 2-phenylethylamine, a predator odorant aversive to mouse. The objective is to compare the findings with those from M71-OR, to figure out whether TAAR4's molecular density on the cilia's surface membrane is very different from that of M71-OR, and to ask whether the amplification at the downstream G-protein/effector enzyme complex activation step is any different from the case of M71-OR. In Aim 3, as another comparison, we shall address the same questions for mOR256-17, an OR with one of the highest abundances known so far in the main olfactory epithelium and with an unusually broad odorant spectrum. Quantitatively elucidating the steps of olfactory transduction will provide great insight into normal olfactory functions, as well as malfunctions arising from genetic defects in the transduction pathway, as amply demonstrated by the huge success as such in the case of visual transduction.

该提案的长期目标是用量化的细节了解嗅觉受体神经元（ORNS）的感觉转导中的营地和Ca2+信号。我们将专注于规范 脊椎动物主嗅觉上皮中的嗅觉转移机制。这种机制涉及 通过环环核苷酸门控（CNG），非选择性阳离子通道导致Na+和Ca2+涌入的cAMP信号级联，从而使ORN的ORN变为射击阈值。 Ca2+涌入导致信号扩增 通过向内CA2+活化的CL电流以及通过多个CA2+激活的负反馈途径的嗅觉适应。但是，最近，负反馈途径的重要性和性能 被怀疑和困惑。在AIM 1中，我们建议重新检查这个问题并解决一次 所有人。 最近，通过使用M71单克荷兰鼠标ORN，我们成功地量化了 嗅觉纤毛膜上M71或分子的密度。我们还发现配体时是M71-or 但是，乙二酮（M71-OR最有效的气味之一）仍然很低 激活单个下游高尔夫/腺苷酸环化酶III效应器的成功概率（名义上〜10-4） 复杂的。这种低概率与Rod Phototransduction的情况大不相同，我们 最近表明，一种光激发的视紫红质激活10-20杆透明蛋白/CGMP-磷酸二酯酶 效应子。因此，在光激活的GPCR途径的信号扩增中，配体激活的GPCR途径可能完全不同。在AIMS 2中，我们建议研究另一种小鼠鼻鼻化学感受器TAAR4，该化学感受器4 对2-苯基乙胺的极敏感，一种捕食者气味对小鼠的反感。目的是 将发现与M71-OR的发现进行比较，以找出taar4的分子密度是否在纤毛上 表面膜与M71-OR的膜大不相同，并询问是否在 下游G蛋白/效应酶复合激活步骤与M71-OR的情况有所不同。在 AIM 3作为另一个比较，我们将解决MOR256-17的相同问题， 到目前为止，在主要嗅觉上皮中已知的最高丰度，并具有异常广泛的气味 光谱。 定量阐明嗅觉转导的步骤将为正常提供充分的洞察力 嗅觉功能以及因转导途径中遗传缺陷引起的故障， 在视觉转导的情况下，以巨大的成功证明。