Calcium channels at ribbon synapses in the retina

描述（由申请人提供）：最近鉴定了引起不完全先天性静止性夜盲症（CSNB 2）的基因，发现其编码视网膜特异性电压激活钙通道α-1F。这种疾病的特征是夜间（或视杆细胞介导的）视力严重下降以及白天（或视锥细胞介导的）视力异常。CSNB 2的电生理和心理物理表型可以通过视网膜内突触传递的缺陷来解释。我们已经发现，α-1F钙通道定位于大鼠和小鼠视网膜中的视杆细胞和视杆双极细胞突触末端，这与CSNB 2相关的夜盲症一致。 电压激活的钙通道对于视网膜中视觉处理的前两个阶段是必不可少的，其发生在光感受器和双极细胞带状突触处。在带状突触处，钙通道将光感受器或双极细胞的分级电响应耦合到兴奋性神经递质谷氨酸的钙依赖性分级释放。我们的数据表明，CSNB 2的症状是由光感受器和双极细胞带状突触的谷氨酸释放阻滞引起的。 α-1F钙通道的详细表征对于理解CSNB 2的复杂表型和视网膜中的正常突触传递是必不可少的。然而，α-1F钙通道的生物物理特性尚不清楚。也不知道α-1F是否存在于视锥光感受器和视锥双极细胞末端，或者是否其他钙通道介导视锥通路中的谷氨酸释放。 拟议的实验将解决这些问题。具体目标是1。详细确定α-1F钙通道亚单位的分布和功能特性。2.识别与alpha-1F相互作用的视网膜蛋白质。3.识别视网膜带状突触中的其他电压激活钙通道。我们将使用涉及分子，生物化学，免疫组织化学和电生理技术的多学科方法来实现这些目标。 这些实验的结果将提供深入了解视网膜带状突触的组成和功能组织，以及与CSNB 2相关的视网膜功能的扰动。

DESCRIPTION (provided by applicant): Recently the gene causing incomplete congenital stationary night blindness (CSNB2) was identified and found to encode a retina-specific, voltage-activated calcium channel, alpha-1F. The disease is characterized by severely reduced nighttime (or rod-mediated) vision as well as abnormalities in daytime (or cone-mediated) vision. The electrophysiological and psychophysical phenotype of CSNB2 can be explained by a defect in synaptic transmission within the retina. We have found that the alpha-1F calcium channel is localized to rod photoreceptor and rod bipolar cell synaptic terminals in the rat and mouse retinas consistent with the night-blindness associated with CSNB2. Voltage-activated calcium channels are essential to the first two stages of visual processing in the retina, which occur at photoreceptor and bipolar cell ribbon synapses. At the ribbon synapse, calcium channels couple the graded electrical responses of the photoreceptor or bipolar cell to calcium-dependent, graded release of the excitatory neurotransmitter, glutamate. Our data suggest that the symptoms of CSNB2 are caused by a block of glutamate release at photoreceptor and bipolar cell ribbon synapses. A detailed characterization of the alpha -1F calcium channel is essential to understanding both the complex phenotype of CSNB2 and normal synaptic transmission in the retina. Yet the biophysical properties of alpha-1F calcium channels are not known. Nor is it known whether alpha-1F is present in cone photoreceptor and cone bipolar cell terminals, or whether other calcium channels mediate glutamate release in the cone pathway. The proposed experiments will address these questions. The Specific Aims are to 1. Determine in detail the distribution and functional properties of the alpha-1F calcium channel subunit. 2. Identify retinal proteins that interact with alpha-1F. 3. Identify other voltage-activated calcium channels at retinal ribbon synapses. We will use a multidisciplinary approach involving molecular, biochemical, immunohistochemical and electrophysiological techniques to achieve these aims. The results of these experiments will provide insight into the composition and functional organization of retinal ribbon synapses and into the perturbation of retinal function associated with CSNB2.