Structural Basis of Signal Instigation Through Metabotropic Glutamate Receptors

 描述(申请人提供)：代谢性谷氨酸受体(MGluRs)属于G蛋白偶联受体(GPCRs)C家族，通过识别氨基酸和兴奋性神经递质谷氨酸，关键地调节神经元的兴奋性、突触传递和可塑性。许多中枢神经系统的紊乱都与谷氨酸能系统引起的神经元兴奋性改变有关。因此，mGluRs一直是一项巨大的药物发现努力的主题，因为它们代表着治疗许多生理功能障碍以及神经退行性和神经精神疾病的主要治疗靶点。除了典型的七跨膜螺旋(7TM)结构域，mGluRs还包括一个大的细胞外金蝇捕蝇器(VFT)结构域(构成谷氨酸结合部位)和一个连接VFT和7TM的半胱氨酸富集区(CRD)。谷氨酸与胞外VFT结构域的结合触发了VFT结构域从开放构象到闭合构象的大范围构象变化。胞外区的这种蛤壳状闭合导致跨膜区细胞内侧的受体结合和G-蛋白的激活。然后，受体激活的G蛋白作用于增强或抑制二级信使信号级联。尽管进行了大量的研究，但由于缺乏关于全长蛋白质的结构信息，mGluRs跨细胞膜的变构通讯机制仍然是个谜。在这里，我们建议应用单粒子冷冻电子显微镜(Cryo-EM)可视化来表征mGluR5和mGluR2在激活和失活状态下的结构，以及与其同源G蛋白形成的复合体的结构。所获得的结构将用于分子动力学模拟，旨在揭示与信号激发或沉默耦合的构象转变的分子基础。鉴于mGluRs是帕金森氏病、脆性X综合征/自闭症谱系障碍、精神分裂症、认知、成瘾、抑郁、焦虑和疼痛等多种中枢神经系统疾病的重要药物靶点，所获得的结果将具有深远的生物医学兴趣，并将成为设计针对神经疾病的新治疗策略的基础。

 DESCRIPTION (provided by applicant): Metabotropic Glutamate receptors (mGluRs) belong to the Family C of G-protein coupled receptors (GPCRs) and critically regulates neuronal excitability, synaptic transmission and plasticity through recognition of the amino acid and excitatory neurotransmitter glutamate. Many disorders of the CNS have been linked to alterations in neuronal excitability via the glutamatergic system. Accordingly, mGluRs have been the subject of an enormous drug discovery effort as they represent major therapeutic targets for treating numerous physiological dysfunctions and for neurodegenerative and neuropsychiatric conditions. Apart from the prototypical seven transmembrane helix (7TM) domain, mGluRs also include a large extracellular venus fly trap' (VFT) domain that constitutes the glutamate binding site and a cysteine rich domain (CRD) that links the VFT to the 7TM. Binding of glutamate to the extracellular VFT domain triggers a large conformational change in the VFT domains from an open to a closed conformation. This clam-shell like closure of the extracellular domain results in receptor engagement and activation of G-proteins on the intracellular side of the transmembrane domain. Receptor activated G proteins then act to either enhance or repress secondary messenger signaling cascades. Despite intensive efforts, the mechanism of allosteric communication across the cell membrane by the mGluRs remains enigmatic due to the lack of structural information on full- length proteins. Here we propose to apply single-particle cryo-electron microscopy (cryo-EM) visualization in order to characterize the structure of mGluR5 and mGluR2 in activated and inactivated states and also in complex with their cognate G-proteins. The obtained structures will be used for molecular dynamics simulations aiming to unravel the molecular basis for conformational transitions coupled to signal instigation or silencing. Given that mGluRs are important drug targets for several CNS conditions including Parkinson's disease, Fragile X syndrome/autism spectrum disorders, schizophrenia, cognition, addiction, depression, anxiety and pain, the results obtained will have profound biomedical interest and will form the basis for the design of novel therapeutic strategies against neurological disorders.