Calcium channels at ribbon synapses in the retina

描述(由申请人提供)：最近，导致不完全性先天性静止性夜盲(CSNB2)的基因被发现并编码视网膜特异的电压激活的钙通道，α-1F。该病的特点是夜间(或视杆调节)视力严重降低，白天(或视锥调节)视力异常。CSNB2的电生理和心理物理表型可以用视网膜内突触传递的缺陷来解释。我们发现α-1F钙通道定位于大鼠和小鼠视网膜的视杆感光细胞和视杆双极细胞突触终末，与CSNB2相关的夜盲一致。 电压激活的钙通道是视网膜视觉处理的前两个阶段所必需的，这两个阶段发生在光感受器和双极细胞带状突触。在带状突触，钙通道耦合光感受器或双极细胞对钙依赖的兴奋性神经递质谷氨酸的分级释放的分级电反应。我们的数据表明，CSNB2的症状是由光感受器和双极细胞带状突触的谷氨酸释放受阻引起的。 对α-1F钙通道的详细描述对于理解CSNB2的复杂表型和视网膜中正常的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是否存在于视锥感光细胞和视锥双极细胞终末，也不知道其他钙通道是否介导了视锥通路中谷氨酸的释放。 拟议的实验将解决这些问题。具体目的是：1.详细测定α-1F钙通道亚基的分布和功能特性。2.确定与α-1F相互作用的视网膜蛋白。3.识别视网膜带突触的其他电压激活的钙通道。我们将使用涉及分子、生化、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。 这些实验的结果将为深入了解视网膜带状突触的组成和功能组织以及与CSNB2相关的视网膜功能的扰动提供依据。

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.