CHARACTERIZATION OF THE HUMAN HAIR CELL RECEPTOR ALPHA-9

烟碱型乙酰胆碱受体家族支持整个神经系统的化学突触传递，包括内耳的传出或离心性调节。虽然已经在几种动物模型中研究了内耳的胆碱能神经支配，但我们对人类内耳内胆碱能传递的了解相当有限。在这里，我们建议对人类内耳中一种可能的尼古丁受体α-9进行分子、电生理和组织学研究。这项工作不仅将为人类毛细胞的胆碱能调节提供分子基础，还将为眩晕和耳鸣等疾病建立新的治疗靶点。此外，烟碱受体功能的突变和紊乱也与多种疾病有关，如重症肌无力、夜间额叶癫痫和精神分裂症。因此，目前的工作也可能对理解没有已知病因的耳科疾病，包括自身免疫性内耳疾病或M-Ne综合征具有更广泛的意义。我们实验室最近的工作导致了对人类α-9正畸基因的鉴定，包括对其cDNA和基因组序列的完整阐明。目前的研究计划的目标是全面描述这种新发现的受体，它可能是人类内耳传出胆碱能反应的媒介。在初步鉴定过程中正在进行的工作将包括在人类组织中寻找剪接变体，以及对其调控元件进行进一步的基因组分析。该项目的第二阶段将包括α-9基因产物在手术来源的毛发群体和其他组织类型中的细胞定位。该项目的第三阶段将包括人类α-9的功能表达，以评估其对乙酰胆碱及其拮抗剂的生理反应。该项目的最后阶段将使用同样的技术，努力识别可能参与内耳传出胆碱能传递的其他胆碱能受体类型。

The family of nicotinic acetylcholine receptors supports chemical synaptic transmission throughout the nervous system, including efferent, or centrifugal regulation of the inner ear. While cholinergic innervation of the inner-ear has been studied in several animal models, our understanding of cholinergic transmission within the human inner ear is quite limited. We propose here to undertake molecular, electrophysiological and histological studies of a putative nicotinic receptor, alpha-9, in the human inner ear. This work will provide not only a molecular basis for the cholinergic modulation of human hair cells, but also will establish targets of novel therapies for diseases such as vertigo and tinnitus. Furthermore, mutations and disorders of nicotinic receptor function have been implicated in such diverse diseases as myasthenia gravis, nocturnal frontal lobe epilepsy and schizophrenia. Thus, the present work may also have wider implications for understanding otologic diseases without a known etiology, including autoimmune inner ear disorders or M ni re's syndrome. Recent work in our lab has led to the identification of the human ortholgue of alpha-9, included a complete elucidation of its cDNA and genomic sequence. The goal of the current research proposal is to fully characterize this newly identified receptor, which is a likely mediator of the efferent cholinergic response in the human inner-ear. Ongoing work during the initial characterization will include the search for splice variants within human tissue, as well as further genomic analysis of its regulatory elements. The second phase of the project will include the cellular localization of the alpha-9 gene product within surgically-derived hair populations and other tissue types. The third phase of the project will include functional expression of human alpha-9 to evaluate its physiologic response to acetylcholine and its antagonists. The final phase of the project will employ these same techniques in an effort to identify additional cholinergic receptor types that may be involved in efferent cholinergic transmission within the inner- ear.