The roles and functions of olfactory transduction channels in the odorant response

摘要 我们的感官将环境刺激转换成电信号，最终由大脑解释 来指导我们的行为决定。刺激的转换依赖于感觉中表达的离子通道 细胞及其属性因此决定了我们如何感知我们的环境。嗅觉感觉神经元 鼻腔(Orns)识别气味，与其他感觉神经元不同，如光感受器和 毛细胞，与外部环境直接接触，只有一层薄薄的粘液层保护。嗅觉 纤毛，含有传递气味的机械的细胞室，必须在这种环境中生存。 在保持功能性的同时，增加了对膜完整性和功能的额外要求。 气味分子与睫状膜中的气味感受器结合的初始事件通过 激活腺苷环化酶，打开嗅觉环核苷酸门控(CNG)通道，从而允许 钙离子内流，进而激活兴奋性的钙激活的氯离子通道，进一步去极化神经元。 这种基于一个阳离子和一个阴离子通道的两级感觉转导机制是独一无二的 并在所有脊椎动物中高度保守。奥恩斯之所以使用这种两级离子通道 以及为什么特别使用阳离子和阴离子电导的组合来感知 气味还不清楚，钙激活的氯通道的作用也是不清楚的。 直到2009年，嗅觉钙激活的氯离子通道的分子同一性才被确定为 Anoctamin 2(ANO2)，尽管有可用的基因敲除模型，但Anno2的作用，因此也是 CNG频道，仍不清楚。我们建议使用一只ANO2基因敲除小鼠，电生理和 分子方法来定义这两个离子通道如何塑造气味诱导的反应。我们会 描述响应的哪些特定方面(适应、响应可靠性、动作电位编码、 等)由单个离子通道或由两者共同决定。另外，因为这两个渠道必须 在睫状膜功能的制约下，我们将探讨该通道如何依赖于睫状膜 它们的功能成分，以及膜的改变如何导致有害的嗅觉功能。 通过研究阳离子和阴离子的两层感觉转导机制 通道作为双组件系统无缝运行，我们将解决嗅觉中的基本问题 这些问题在过去的25年里一直没有得到回应。 这项提案的长期目标是确定On如何总体上使用它们的信号转导和 他们的离子通道特别是可靠地编码气味刺激，转导如何在 纤毛膜的限制，以及这最终如何决定气味如何被感知。

Summary Our senses convert environmental stimuli into electrical signals that are ultimately interpreted by the brain to guide our behavioral decisions. The conversion of stimuli relies on the ion channels expressed in sensory cells, and their properties thus determine how we perceive our environment. Olfactory receptor neurons (ORNs) in the nasal cavity recognize odorants and, unlike other sensory neurons such as photoreceptors and hair cells, are in direct contact with the external environment, protected only by a thin mucus layer. Olfactory cilia, the cellular compartment that contains the machinery that transduces odorants, must survive in this environment while remaining functional, adding extra demands on membrane integrity and function. The initial event of an odor molecule binding to an odorant receptor in the ciliary membrane leads, via activation of adenylyl cyclase, to opening of the olfactory cyclic-nucleotide gated (CNG) channel that allows Ca2+ influx, which in turn activates an excitatory Ca2+-activated Cl- channel, further depolarizing the neuron. This two-tiered sensory transduction mechanism based on one cationic and one anionic channels, is unique to ORNs and highly conserved across all vertebrates. Both the reason why ORNs use this two-stage ion channel system in general and why a combination of cation and anion conductances in particular is used to perceive odorants are unclear, as is the role of the Ca2+-activated Cl- channel. Only in 2009 was the molecular identity of the olfactory Ca2+-activated Cl- channel determined to be anoctamin 2 (Ano2), and despite a knockout model being available, the roles of Ano2, and therefore also of the CNG channel, remain unclear. We propose to use an Ano2-knockout mouse, electrophysiological and molecular approaches to define how these two ion channels shape the odorant-induced response. We will characterize which specific aspects of the response (adaptation, response reliability, action potential coding, etc.) are determined by a single ion channel or jointly by both. In addition, because the two channels must function in the constraints of the ciliary membrane, we will investigate how the channels rely on membrane constituents for their function and how altered membranes leads to detrimental olfactory function. By examining how the two-tiered sensory transduction mechanism of a cationic and an anionic ion channel operates seamlessly as a dual-component system, we will address fundamental questions in olfaction that have remained unanswered for the past 25 years. The long-term goal of this proposal is to establish how ORNs use their signal transduction in general and their ion channels in particular to reliably encode odorant stimuli, how transduction functions within the constraints of the ciliary membrane, and how this ultimately determines how odorants are perceived.