OMP: Role in Olfactory Signal Detection and Transduction

描述（由申请人提供）：钙在嗅觉受体神经元（ORN）的信号转导级联中起许多作用。Ca 2+通过cAMP门控通道进入，响应G蛋白介导的腺苷酸环化酶活性增加的气味配体受体激活。Ca 2+内流是哺乳动物嗅觉化学感受性转导的关键步骤，并刺激Ca 2+激活的氯离子通道以放大转导电流。ca 2+是 也是适应、脱敏、恢复和转导-翻译偶联的调节剂。许多努力已被导向了解这些事件在ORN。很少有人关注下游事件，保持稳定的细胞内Ca 2+水平的ORN。我们对嗅觉标记蛋白（OMP）缺失小鼠表型的表征 使用电生理学、生物化学和行为学的方法，我们推测OMP-无效表型是由于调节细胞内Ca 2+水平的缺陷。具体而言，我们假设OMP参与调节ORN中Ca 2+挤出过程的活性。OMP在成熟ORN中表达的特异性，其在所有脊椎动物中的序列保守性，以及OMP缺失小鼠表型， 提示OMP对嗅觉功能有重要作用。我们最近观察到一个显着的改变，钙动力学ORIN树突状球在OMP-null小鼠刺激后。几个基因参与Ca 2+排出，包括Na+/Ca 2+交换器（NCX）和Na+/Ca 2 +-K+交换器（NCKX）。三个基因代表了这些和许多mRNA剪接变异体中的每一个，这些mRNA剪接变异体以细胞和组织特异性模式表达。免疫细胞化学和电生理学的报告表明，这些交换器是重要的，在维持细胞内的ORN水平。这些报告，再加上我们的新数据，OMP调制Ca 2+的挤出进一步支持我们的假设和表征的分子和生化基础的Ca 2+的挤出过程中ORN的重要性。这是我们的知识中的一个重大空白，本提案解决了这个问题。 我们将（1）-表征NCX和NCKX基因在嗅觉组织中的表达，特别是在ORN中，在发育过程中和对病变的反应中;（2）-鉴定参与OMP介导的Ca水平调节的特定NCX或NCKX蛋白的部分;（3）-确定该过程中其他参与者的性质和功能，例如最近发现的与OMP结合的Bex蛋白。这些研究将为阐明其作用机制提供新的见解 通过其在ORN中调节细胞内Ca 2+水平，并且可以产生用于治疗厌食症或嗅觉障碍的化疗机会。

DESCRIPTION (provided by applicant): Calcium plays many roles in the signal-transduction cascade in olfactory receptor neurons (ORNs). Ca2+ enters through cAMP-gated channels in response to odor-ligand receptor activation of G-protein-mediated increases in adenylyl cyclase activity. Ca2+ entry is a key step in mammalian olfactory chemosensory transduction and stimulates a Ca2+-activated chloride channel to amplify the transduction current. Ca2+ is also a regulator of adaptation, desensitization, recovery and transduction-translation coupling. Much effort has been directed towards understanding these events in the ORN. Much less attention has been paid to downstream events that maintain stable intracellular Ca2+ levels in ORNs. Our characterization of the olfactory marker protein (OMP)-null mouse phenotype using electrophysiological, biochemical and behavioral measures in the previous funding cycle have led us to hypothesize that the OMP-null phenotype is due to a defect in regulating intracellular Ca2+ levels. Specifically, we hypothesize that OMP participates in regulating the activity of Ca2+ extrusion processes in ORNs. The specificity of OMP expression in mature ORNs, its sequence conservation across all vertebrates, and the OMP-null mouse phenotype all indicate OMP is important to olfactory function. We recently observed a significant alteration in Ca2+ kinetics in ORIN dendritic knobs in OMP-null mice following stimulation. Several genes participate in Ca2+ extrusion including the Na+/Ca2+ exchangers (NCX), and the Na+/Ca2+-K+ exchangers (NCKX). Three genes represent each of these and numerous mRNA splice variants expressed in cell- and tissue-specific patterns. Immunocytochemical and electrophysiological reports suggest that these exchangers are important in maintaining intracellular ORN levels. These reports, coupled with our new data that OMP modulates Ca2+ extrusion further supports our hypothesis and the importance of characterizing the molecular and biochemical bases of Ca2+ extrusion processes in ORNs. This is a significant gap in our knowledge that this proposal addresses. We will (1)-characterize NCX and NCKX gene expression in olfactory tissue, and especially in ORNs, during development and in response to lesions; (2)-identify that part of the specific NCX or NCKX protein that participates in the OMP-mediated regulation of Ca levels; (3)-determine the nature and function of other participants in this process e.g. the recently discovered Bex proteins that bind to OMP. These studies will provide novel insights to the mechanisms by which intracellular Ca2+ levels are regulated in ORNs and may generate chemotherapeutic opportunities for treatment of anosmias or dysosmias.