CAA: Molecular Basis for the Cholinergic Modulation of Auditory Hair Cell Properties

在哺乳动物的内耳中，感觉细胞的一个亚群接受来自大脑的抑制性输入。像这样从大脑到感觉器官的神经元反馈通路被称为传出通路或下行通路。类似的神经反馈也能调节鱼的侧线以及爬行动物、两栖动物和鸟类的内耳的感觉知觉。事实上，这种传出抑制在动物类中一直是保守的，这表明了这一过程的根本重要性。这种听觉传出通路通过调节感觉细胞的兴奋性，使我们的听觉具有高度的灵敏度和频率选择性。然而，这种调节反馈的机制在分子水平上尚不清楚。已知乙酰胆碱受体α 9和α 10以及小电导Ca2+激活钾通道SK2通常与钙源共定位，是哺乳动物听觉感觉细胞中必需的分子成分。该项目应用分子生物学策略来识别参与这些离子通道之间的选择性定位、聚类和功能关联的蛋白质。此外，已经构建了SK2和α 9/ α 10受体的荧光标记嵌合体，以应用最先进的光学技术来研究它们功能相互作用的生化基础。这些发现将促进我们对包括离子通道之间蛋白质-蛋白质相互作用在内的感官知觉的生化原理的理解。在完成本项目的同时，将培养研究生和博士后利用强大的电生理和光学研究技术以及生化和分子技术。这些是神经科学和其他生物研究前沿的基本技术，对可兴奋细胞中含有离子通道的大分子复合物的详细了解是基础。

In the mammalian inner ear a subpopulation of the sensory cells receive inhibitory inputs from the brain. Neuronal feedback pathways such as this one, from the brain to the sensory organ are called efferent or descending pathways. Similar neural feedback modulates sensory perception also in the lateral lines of fish and in the inner ears of reptiles, amphibians, and birds. The fact that this efferent inhibition has been conserved across animal classes suggests the fundamental importance of this process. This auditory efferent pathway contributes to the exquisite sensitivity and frequency selectivity of our sense of hearing by modulating the excitability of the sensory cells. However, the mechanisms underlying this modulatory feedback are not understood at the molecular level. It is known that the acetylcholine receptors alpha 9 and alpha 10 and the small conductance Ca2+-activated potassium channels SK2, which are often co-localized with calcium sources are required molecular components in the mammalian auditory sensory cells. This project applies a molecular biology strategy to identify proteins involved in the selective localization, clustering, and functional associations between these ion channels. Additionally, fluorescently tagged chimeras of the SK2 and of the alpha 9/ alpha 10 receptors have been constructed to apply state-of-the-art optical techniques to the investigation of the biochemical basis of their functional interactions. The findings will advance our understanding of the biochemical principles underlying sensory perception including protein-protein interactions between the ion channels involved. While completing this project graduate students and post-doctoral fellows will be trained to utilize powerful electrophysiological and optical research techniques as well as biochemical and molecular techniques. These are essential techniques in neuroscience and other biological research frontiers for which a detailed understanding of macromolecular complexes harboring ion channels in excitable cells is fundamental.