Molecular mechanisms of vestibular hair cell exocytosis

描述（由申请人提供）：前庭系统中的机械感觉毛细胞将有关头部位置和运动的信息转化为神经元信号。本应用程序的目的是阐明从前庭毛细胞到传入纤维的突触传递的分子机制。毛细胞传入突触表现出解剖（突触体或带状）和功能（对逐渐去极化的反应）特化，使它们与神经系统中的其他突触区别开来。我们在此建议研究在常规突触中重要的蛋白质和蛋白质相互作用对毛细胞突触传递是重要的。此外，前庭生理学缺乏对I型和II型毛细胞功能差异的理解。仅在羊膜中发现的I型毛细胞被传入神经吞没，这表明突触生理学存在差异。因此，本实验旨在进一步了解前庭I型毛细胞和II型毛细胞在神经递质释放方面的分子和功能差异。这些实验将进一步加深我们对前庭和听觉系统中第一突触的分子和生物物理理解。

DESCRIPTION (provided by applicant): Mechanosensory hair cells in the vestibular system transduce information about head position and movement into neuronal signals. The aim of this application is to elucidate the molecular mechanisms underlying synaptic transmission from vestibular hair cells to afferent fibers. The hair cells afferent synapse exhibits anatomical (synaptic bodies or ribbons) and functional (responding to graded depolarizations) specializations that distinguish them from other synapses in the nervous system. We here propose to investigate which proteins and protein-interactions important at conventional synapses are important for hair cell synaptic transmission. Furthermore, vestibular physiology lacks an understanding of the functional difference between type I and type II hair cells. Type I hair cells, found only in amniotes, are engulfed by the afferent nerve, suggesting differences in synaptic physiology. The proposed experiments are therefore further aimed at understanding the molecular and functional difference in neurotransmitter release between vestibular type I and type II hair cells. These experiments will further our molecular and biophysical understanding of the first synapse in the vestibular and auditory system. Hair cells release neurotransmitter from the basolateral end of the cell body, offering relatively easy access to synaptic areas for the introduction of toxins and peptides to acutely perturb protein function. Exocytosis will be monitored directly by measuring the increase in cell membrane area that occurs when vesicles fuse with the plasma membrane. Specific Aim 1 tests the hypothesis that exocytosis is regulated by a specific subset of SNARE proteins. Specific Aim 2 addresses whether vesicle recycling is limiting for exocytosis. In Specific Aim 3 the hypothesis is tested that glutamate acts in a positive feedback loop to enhance release especially in type I hair cells. A detailed understanding of the proteins and mechanisms of release at this initial sensory synapse aid in identifying novel therapeutic approaches targeting vestibular dysfunction.