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

总结 我们的感官将环境刺激转化为电信号，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神经元中表达的离子通道。 细胞及其特性决定了我们如何感知环境。嗅觉受体神经元 鼻腔中的ORN（ORN）识别气味，并且与其他感觉神经元（如光感受器和 毛细胞与外部环境直接接触，仅由薄粘液层保护。嗅觉 纤毛，细胞间室，包含机器，转导气味，必须生存在这一点上， 环境，同时保持功能，增加了对膜完整性和功能的额外要求。 气味分子与睫状体膜中的气味受体结合的初始事件导致， 腺苷酸环化酶的激活，打开嗅觉环核苷酸门控（CNG）通道， Ca 2+内流，这又激活兴奋性Ca 2+激活的Cl-通道，进一步使神经元去极化。 这种基于一个阳离子通道和一个阴离子通道的双层感觉转导机制是独特的， 在所有脊椎动物中高度保守。ORN使用这种两级离子通道的原因 以及为什么特别使用阳离子和阴离子电导的组合来感知 气味剂尚不清楚，Ca 2+激活的Cl-通道的作用也不清楚。 直到2009年，嗅觉Ca 2+激活的Cl-通道的分子身份才被确定为 Anoctamin 2（Ano 2），尽管敲除模型可用，Ano 2的作用，因此也是Ano 2的作用。 CNG通道，仍不清楚。我们建议使用Ano 2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形成气味诱导的反应。我们将 表征反应的哪些具体方面（适应性，反应可靠性，动作电位编码， 等等）。由单个离子通道或两者共同决定。此外，由于这两个渠道必须 在睫状膜的约束下，我们将研究通道如何依赖于膜 它们的功能和改变的膜如何导致有害的嗅觉功能。 通过研究阳离子和阴离子的双层感觉传导机制 通道作为一个双组分系统无缝运行，我们将解决嗅觉的基本问题 过去25年来一直没有答案 这项建议的长期目标是建立一般情况下ORN如何使用它们的信号转导， 它们的离子通道，特别是可靠地编码气味刺激，如何转导功能内 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.