Neuron-glia interactions in Drosphila visual neuropiles

描述(申请人提供)：拟议研究的长期目标是揭示视觉系统中神经元-神经胶质细胞相互作用的功能和机制。由于以往对视觉的研究大多集中在视觉转导通路和神经元回路上，我们对神经胶质细胞在视觉信号中的作用的了解仍然非常有限。有趣的是，在哺乳动物和苍蝇的眼睛中，神经胶质细胞都表达视觉中间神经元的神经递质受体。目前还不清楚胶质细胞是否直接与这些神经元进行通讯，以调节视觉信号。在我们对果蝇视觉的初步研究中，我们发现视觉上皮胶质细胞可能在Gnarl集中了一个谷氨酸门控氯离子通道GluCl，Gnarl是一种特殊的神经胶质膜结构，通常位于谷氨酸能神经元间无长突细胞和其突触后伙伴T1细胞之间。当阻断无长突细胞的谷氨酸释放时，光反应结束时感光细胞的复极速度明显减慢。重要的是，这种视觉缺陷是通过下调GluCl在上皮性胶质细胞中的表达而表现出来的，在受损的Gnarl结构的ADAM蛋白突变体中也观察到了这种缺陷。基于这些观察，我们提出了光感受器-无长突细胞-上皮性胶质细胞-光感受器反馈环的存在，它的功能是增强光感受器复极的速度，因此对视觉的时间分辨率是重要的。结合分子和细胞生物学、遗传学、组织学和电生理学的方法，我们建议进一步研究视觉上皮神经胶质细胞的这一新功能。具体地说，我们将1.测试板层上皮胶质细胞通过谷氨酸门控氯离子通道GluCl接受神经元输入的假设；2.测试需要Adam蛋白MMD将GluCl定位在神经元-胶质细胞信号转导的关节结构中的假设；3.确定上皮性胶质细胞介导的光感受器调节的机制。这些研究不仅对视觉生物学很重要，而且还将对我们的 对神经胶质功能的一般理解。 公共卫生相关性：视觉神经胶质细胞对视网膜神经元的发育和保护是必不可少的，并与多种视网膜疾病有关。在这项提议中，我们计划使用果蝇的眼睛作为遗传模型来研究视觉胶质细胞如何直接与神经元相互作用，以及它们如何相互调节彼此的活动。这项研究的发现可能为旨在防止视网膜神经元退化的治疗设计提供有价值的线索。

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to reveal functions and mechanisms of neuron-glia interaction in visual systems. As previous studies on vision have mostly been focused on the visual transduction cascades and the neuronal circuits, our knowledge about the role of glial cells in visual signaling is still very limited. Intriguingly, glial cells express receptors for neurotransmitters of visual interneurons i both mammalian and fly eyes. It is unknown whether glial cells directly communicate with those neurons for regulation of visual signaling. In our preliminary studies on Drosophila vision, we found that the visual epithelial glia may concentrate a glutamate-gated chloride channel GluCl in 'gnarl', a special glial membrane structure that typically interposes between a glutamatergic interneuron amacrine cell and its postsynaptic partner T1 cell. When the glutamate release from amacrine cell was blocked, the speed of photoreceptor repolarization at the end of light response was reduced significantly. Importantly, this visual defect was phenocopied by knocking down the GluCl expression specifically in the epithelial glia, and was also observed in an ADAM protein mutant of impaired gnarl structure. Based on these observations, we propose the existence of a photoreceptor-amacrine cell-epithelial glia-photoreceptor feedback loop, which functions to reinforce the speed of photoreceptor repolarization and is thus important for the temporal resolution of vision. Using a combination of molecular and cell biological, genetic, histological, and electrophysiological approaches, we propose to further investigate this novel function of visual epithelial glia. Specifically, we will 1. Test the hypothesis that laminar epithlial glia receive neuronal input through the glutamate-gated chloride channel GluCl; 2. Test the hypothesis that an ADAM protein MMD is required to localize GluCl in the gnarl structure for the neuron-glia signaling; 3. Identify the mechanism of epithelial glia-mediated photoreceptor regulation. These studies are not only important to visual biology, but will also contribute to our understanding of glial function in general. PUBLIC HEALTH RELEVANCE: Visual glia cells are essential for retinal neuron development and protection, and are implicated in a variety of retinopathies. In this proposal we plan to use the Drosophila eye as a genetic model to study how visual glia interact directly with neurons and how they reciprocally regulate the activity of each other. Findings from this study may provide valuable clues to therapeutic designs directed to prevent degeneration of retinal neurons.