Structural landscape of photoreceptor synapses

项目摘要 视杆和视锥光感受器对我们的视觉是不可或缺的。他们的死亡或功能障碍是潜在的 导致绝大多数致盲性视网膜疾病。光感受器功能的关键是传递光的能力。 它们响应于光而产生的信号传递到视网膜中的其他神经元以处理视觉信号， 他们与大脑的交流。为了做到这一点，光感受器形成了精细的突触， 下游神经元，双极细胞（BC）。光感受器和神经元之间突触通讯的缺陷 已知双极细胞会导致人类先天性静止性失明，各种形式的视杆/视锥细胞 营养不良以及与许多其它眼部病症的频繁共病。我们合作的长期目标 该计划是为了获得原子水平的机械，使突触的分子组织的看法 光感受器的通信，希望更好地了解致盲条件和设计 他们的治疗策略。 我们的实验室和其他人最近的研究已经确定了几种关键的分子， 光感受器的突触通讯。我们进一步发现，这些组件中有许多是 支架形成跨越突触间隙的大分子组装体，并在物理上整合突触前 BC中的光感受器元件与突触后感受器。具体来说，我们发现突触后 BC上的受体：mGluR 6与光感受器中的两种细胞粘附分子相互作用：ELFN 1和ELFN 2。 此外，响应于突触光感受器输入而驱动BC兴奋的机制是 与孤儿受体GPR 179相关，后者又与突触前细胞粘附样蛋白整合。 分子pikachurin（鼠兔）在光感受器。我们还记录了失去这个组织 突触传递导致夜盲症然而，目前我们对 这些跨突触复合物的结构基础。 拟议的研究旨在通过确定关键跨突触的原子结构来填补这一空白。 支架：ELFN 1-mGluR 6和Pika-GPR 179复合物，并探索其生化机制。这将 通过高度协同的国际合作，利用生物化学和细胞生物学方面的专业知识， 光感受器突触蛋白的研究进展及高分辨率低温电子显微镜的最新进展 （CryoEM）以获得复合物的高分辨率分子结构，从而探测它们在 非常精确的水平。这个建议的前提是，了解突触组织的 光感受器将导致改善失明的新的治疗策略。

PROJECT SUMMARY Rod and cone photoreceptors are indispensable for our vision. Their death or dysfunction is an underlying cause for a vast majority of blinding retina conditions. Key to photoreceptor function is the ability to transmit the signal that they generate in response to light to other neurons in the retina for processing of visual signals and their communication to the brain. For this to occur, photoreceptors form elaborate synapses with the downstream neurons, the bipolar cells (BC). Deficits in synaptic communication between photoreceptors and bipolar cells are known to cause congenital stationary blindness in humans, various forms of rod/cone dystrophies and frequent co-morbidity with many other ocular conditions. The long term goal of our collaborative program is to obtain atomic level view of molecular organization of machinery that enable synaptic communication of the photoreceptors with the hope to better understand blinding conditions and devising strategies for their treatment. Recent research from our laboratories and others have identified several molecules critical for the synaptic communication of photoreceptors. We have further discovered that many of these components are scaffolded into macromolecular assemblies that span the synaptic cleft and physically integrate pre-synaptic elements of photoreceptors with post-synaptic receptors in BC. Specifically, we found that the postsynaptic receptor on BC: mGluR6 interacts with two cell-adhesion molecules in photoreceptors: ELFN1 and ELFN2. Furthermore, the machinery that drives excitation of BC in response to synaptic photoreceptor inputs is associated with an orphan receptor GPR179 which in turn is integrated with pre-synaptic cell adhesion-like molecule pikachurin (Pika) in photoreceptors. We also documented that loss of this organization abolishes synaptic transmission leading to night blindness. However, at the moment we know absolutely nothing about structural basis of these trans-synaptic complexes. Proposed studies aim to fill this gap by determining the atomic structures of the key trans-synaptic scaffolds: ELFN1-mGluR6 and Pika-GPR179 complexes and probing their biochemical mechanisms. This will be achieved by highly synergistic international collaboration leveraging expertise in biochemistry and cell biology of photoreceptor synaptic proteins and recent advances in high resolution cryogenic electron microscopy (CryoEM) to obtain high resolution molecular structures of the complexes probing their mechanisms at exceedingly precise level. The premise of this proposal is that understanding synaptic organization of photoreceptors would lead to novel therapeutic strategies for ameliorating blindness.