The cannabinoid receptor interacting protein CRIP1 binds to glutamate receptors in the CNS: Molecular mechanisms and functional implications

大麻素受体相互作用蛋白 CRIP1 与 CNS 中的谷氨酸受体结合：分子机制和功能意义

• 批准号: 240914721
• 负责人: Professor Dr. Ralf Enz
• 金额: --
• 依托单位: Professur für Biochemie und Medizinische Molekularbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/240914721?language=en
• 关键词: cannabinoid; receptor; interacting; protein; CRIP1

Glutamate is the most important excitatory neurotransmitter in the central nervous system (CNS) and activates G-protein coupled (metabotropic) glutamate receptors (mGluR1-mGluR8). Also endocannabinoids regulate G-protein coupled receptors (CB1 and CB2) that regulate neuronal activity and are responsible for psychotic effects of marijuana. Photoreceptors of the mammalian retina co-express pre-synaptically mGluR8 and CB1 that are both part of negative feedback loops regulating glutamate release from photoreceptor terminals. In this way, mGluR8 and CB1 participate in adaptive mechanisms that regulate the sensitivity of the retina over a large range of illumination.Crosstalk between different neurotransmitter receptor classes represents a key mechanism to coordinate signal pathways in neurons. Functional interactions between CB1 and mGluR types were reported. In addition, receptors for adenosine and serotonin form heterodimers with CB1 or mGluR2, and the formation of heterotrimeric receptor complexes composed of adenosine, dopamine, glutamate and endocannabinoid receptors in different combinations was demonstrated. In addition, intracellular scaffold proteins can physically link functionally connected receptor types.Recently, we identified the cannabinoid receptor interacting protein 1a CRIP1a as a new binding partner of the mGluR8a isoform. Therefore, we suggest a functional/physical interaction between mGluR8a and CB1 via CRIP1. This hypothesis is based on (i) the identification of CRIP1a as a mGluR8a interactor, (ii) the co-expression of CRIP1a, CB1 and mGluR8a in pre-synaptic photoreceptor terminals, (iii) similar physiological functions of CB1 and mGluR8a (inhibition of the pre-synaptic glutamate release), (iv) a high homology between the mapped 9 amino acid long CRIP1a binding sequence in the CB1 C-terminus and a linear stretch of 6 amino acids in the mGluR8a C-terminus and (v) finally on the known biological principle that receptor crosstalk can occur via intracellular proteins.We plan to characterise molecular mechanisms that mediate the identified mGluR8a/CRIP1a interaction, as well as to elucidate a suggested physical/functional crosstalk between mGluR8a and CB1 in the CNS. Our working programme will first analyse molecular mechanisms of the binding between mGluR8a, CB1 and CRIP1a, thereby providing molecular tools and mechanistic knowledge for successive functional studies. These data will be complemented by anatomical co-localization experiments. Thereafter, we plan to investigate functional consequences of the newly identified protein interactions, first using recombinantly expressed proteins in HEK-293 cells and thereafter in photoreceptors.Our studies are designed to describe new principles of neurotransmitter receptor function in the CNS and will specifically elucidate molecular mechanisms that regulate signalling at the first visual synapse in the mammalian retina.

谷氨酸是中枢神经系统(CNS)中最重要的兴奋性神经递质，激活G蛋白偶联(代谢型)谷氨酸受体(mGluR1-mGluR8)。此外，内源性大麻素调节G蛋白偶联受体(CB1和CB2)，而G蛋白偶联受体调节神经元活动，并与大麻的精神效应有关。哺乳动物视网膜的光感受器在突触前共表达mGluR8和CB1，它们都是调节光感受器终末释放谷氨酸的负反馈环的一部分。通过这种方式，mGluR8和CB1参与了适应机制，在大范围的光照下调节视网膜的敏感性。不同神经递质受体类之间的交叉作用是协调神经元中信号通路的关键机制。报道了CB1和mGluR类型之间的功能相互作用。此外，腺苷和5-羟色胺的受体与CB1或mGluR2形成异二聚体，并证明在不同的组合中形成由腺苷、多巴胺、谷氨酸和内源性大麻素受体组成的异三聚体受体复合体。最近，我们发现大麻素受体相互作用蛋白1a CRIP1a是mGluR8a亚型的一个新的结合伙伴。因此，我们认为mGluR8a与CB1之间存在通过CRIP1的功能/物理相互作用。这一假说是基于(I)CRIP1a是mGluR8a相互作用因子，(Ii)CRIP1a，CB1和mGluR8a在突触前光感受器终末共表达，(Iii)CB1和mGluR8a相似的生理功能(抑制突触前谷氨酸释放)，(Iv)CB1C末端的9个氨基酸长CRIP1a结合序列与mGluR8a C末端的6个氨基酸的线性延伸之间的高度同源性，以及(V)已知的生物学原理，即受体交叉可以通过细胞内蛋白发生。我们计划描述介导所识别的mGluR8a/CR1a相互作用的分子机制，以及阐明中枢神经系统中mGluR8a和CB1之间可能存在的物理/功能串扰。我们的工作计划将首先分析mGluR8a、CB1和CRIP1a之间结合的分子机制，从而为后续的功能研究提供分子工具和机制知识。这些数据将由解剖学共同定位实验来补充。此后，我们计划研究新发现的蛋白质相互作用的功能后果，首先使用在HEK-293细胞中重组表达的蛋白质，然后在光接收器中。我们的研究旨在描述中枢神经系统神经递质受体功能的新原理，并将专门阐明调控哺乳动物视网膜第一视觉突触信号的分子机制。