Khayenko Vladimir, Maric Hans Michael
Institute of Structural Biology, Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany.
Department of Biotechnology and Biophysics, Biocenter, University of Würzburg, Würzburg, Germany.
Front Mol Neurosci. 2019 Jun 26;12:162. doi: 10.3389/fnmol.2019.00162. eCollection 2019.
γ-aminobutyric acid type A receptors (GABARs) are the major mediators of synaptic inhibition in the brain. Aberrant GABAR activity or regulation is observed in various neurodevelopmental disorders, neurodegenerative diseases and mental illnesses, including epilepsy, Alzheimer's and schizophrenia. Benzodiazepines, anesthetics and other pharmaceutics targeting these receptors find broad clinical use, but their inherent lack of receptor subtype specificity causes unavoidable side effects, raising a need for new or adjuvant medications. In this review article, we introduce a new strategy to modulate GABAeric signaling: targeting the intracellular protein interactors of GABARs. Of special interest are scaffolding, anchoring and supporting proteins that display high GABAR subtype specificity. Recent efforts to target gephyrin, the major intracellular integrator of GABAergic signaling, confirm that GABAR-associated proteins can be successfully targeted through diverse molecules, including recombinant proteins, intrabodies, peptide-based probes and small molecules. Small-molecule artemisinins and peptides derived from endogenous interactors, that specifically target the universal receptor binding site of gephyrin, acutely affect synaptic GABAR numbers and clustering, modifying neuronal transmission. Interference with GABAR trafficking provides another way to modulate inhibitory signaling. Peptides blocking the binding site of GABAR to AP2 increase the surface concentration of GABAR clusters and enhance GABAergic signaling. Engineering of gephyrin binding peptides delivered superior means to interrogate neuronal structure and function. Fluorescent peptides, designed from gephyrin binders, enable live neuronal staining and visualization of gephyrin in the post synaptic sites with submicron resolution. We anticipate that in the future, novel fluorescent probes, with improved size and binding efficiency, may find wide application in super resolution microscopy studies, enlightening the nanoscale architecture of the inhibitory synapse. Broader studies on GABAR accessory proteins and the identification of the exact molecular binding interfaces and affinities will advance the development of novel GABAR modulators and following studies will reveal their clinical potential as adjuvant or stand-alone drugs.
γ-氨基丁酸A型受体（GABARs）是大脑中突触抑制的主要介质。在各种神经发育障碍、神经退行性疾病和精神疾病中，包括癫痫、阿尔茨海默病和精神分裂症，都观察到GABAR活性或调节异常。苯二氮䓬类药物、麻醉剂和其他靶向这些受体的药物在临床上有广泛应用，但它们固有的缺乏受体亚型特异性会导致不可避免的副作用，因此需要新的或辅助药物。在这篇综述文章中，我们介绍一种调节GABA能信号传导的新策略：靶向GABARs的细胞内蛋白相互作用分子。特别值得关注的是具有高GABAR亚型特异性的支架蛋白、锚定蛋白和支持蛋白。最近针对GABA能信号传导的主要细胞内整合蛋白gephyrin的研究证实，通过包括重组蛋白、胞内抗体、肽基探针和小分子在内的多种分子，可以成功靶向与GABAR相关的蛋白。小分子青蒿素和源自内源性相互作用分子的肽，特异性靶向gephyrin的通用受体结合位点，可急性影响突触GABAR数量和聚集，改变神经元传递。干扰GABAR转运是调节抑制性信号传导的另一种方式。阻断GABAR与AP2结合位点的肽可增加GABAR簇的表面浓度并增强GABA能信号传导。gephyrin结合肽的工程改造为研究神经元结构和功能提供了更好的手段。由gephyrin结合剂设计的荧光肽能够对活神经元进行染色，并以亚微米分辨率在突触后位点可视化gephyrin。我们预计，未来具有改进尺寸和结合效率的新型荧光探针可能会在超分辨率显微镜研究中得到广泛应用，揭示抑制性突触的纳米级结构。对GABAR辅助蛋白的更广泛研究以及对确切分子结合界面和亲和力的鉴定将推动新型GABAR调节剂的开发，后续研究将揭示它们作为辅助药物或独立药物的临床潜力。
