MOLECULAR MECHANISMS OF SIGNAL TRANSDUCTION IN RETINA

描述(摘自申请者的摘要)：在视网膜中，特化的 突触传递光刺激诱导的渐进性超极化 二阶神经元的光感受器，即双极和水平 细胞。在这些带状突触中，神经递质谷氨酸 在黑暗中释放，刺激突触后细胞上的谷氨酸受体 (水平和非双极细胞上的AMPA/海人酸型受体；mGluR6打开 双极细胞)。代谢性谷氨酸受体mGluR8，我们最近 克隆的，存在于光感受器末端。我们假设，在那里， 在海马体和嗅觉系统中，它可能提供一种 谷氨酸释放的负反馈调节。我们最近生成了 MGluR8已被同源基因灭活的转基因小鼠 重组。我们将使用这些动物以及表达基因的细胞系 MGluR8或突变体mGluR8以解决以下特定目标：(1)是否 光感受器突触和视网膜发育因缺乏 缺乏这种受体的转基因动物中的mGluR8；(2)什么信号 转导通路将mGluR8的激活与一种 细胞内钙水平和可能的谷氨酸释放；(3)什么 控制mG1uR8对轴突终末的本地化；以及(4)如何 MGluR8对光感受器谷氨酸的负反馈调节 释放塑造双极细胞的光反应。这一目标将在#年实现 与罗兰·泰勒(约翰·科廷医学院)合作 是目前唯一能够进行这样的实验的。拟议的法规 MGluR8在光感受器带突触上的突触传递 可能对视觉很重要，因为在这个突触，膜电位 由光传导产生的变化被转化为对 神经递质释放。

DESCRIPTION (Adapted from applicant's abstract): In the retina, specialized synapses transmit the graded hyperpolarization induced by light stimuli in photoreceptors to the second order neurons, i.e., and bipolar and horizontal cells. At these ribbon synapses, the neurotransmitter glutamate is continuously released in the dark and stimulates glutamate receptors on postsynaptic cells (AMPA/kainate-type receptors on horizontal and OFF-bipolar cells; mGluR6 on ON bipolar cells). The metabotropic glutamate receptor mGluR8, which we recently cloned, is present in the photoreceptor terminal. We hypothesize that there, as in the hippocampus and olfactory system, it may be providing a negative-feedback regulation of glutamate release. We recently generated transgenic mice in which mGluR8 has been inactivated by homologous recombination. We will use these animals, as well as cell lines that express mGluR8 or mutant mGluR8 to address the following specific aims: (1) whether photoreceptor synapses and retinal development are altered by the absence of mGluR8 in transgenic animals lacking this receptor; (2) what the signal transduction pathway is linking mGluR8 activation to a modulation of intracellular calcium level and, presumably, glutamate release; (3) what controls the localization of mG1uR8 to axon terminals; and (4) how this proposed negative-feedback regulation of mGluR8 on photoreceptor glutamate release shapes the light responses of bipolar cells. This aim will be done in collaboration with Rowland Taylor (John Curtin School of Medical Research) who is currently uniquely able to perform such experiments. The proposed regulation of synaptic transmission by mGluR8 at the photoreceptor ribbon synapse is likely to be important for vision since at this synapse, the membrane potential changes produced by phototransduction are converted into a modulation of neurotransmitter release.