公募シンポジウム

公募シンポジウム9【アストロサイトによるシナプス再編と脳機能】

2021/10/1　10:00～12:00　ZOOM A会場 S9-1 近位依存性ビオチン標識法Split-TurboID により解き明かす三者間シナプスの分子機構 Department of Neurophysiology, Keio University School of Medicine ^○髙野哲也慶應義塾大学医学部生理学 ^○Tetsuya Takano Department of Neurophysiology, Keio University School of Medicine Neuronal synapses are intimately ensheathed by abundant astrocytic perisynaptic processes, which are critical for synapse formation and function. In contrast to well-studied neuronal synaptic compartments, however, the molecular mechanisms of how astrocytic perisynaptic structures govern neuronal synapses remain ill-defined. Here, we develop a new in vivo chemico-genetic approach, Split-TurboID, that uses a cell surface fragment complementation strategy combined with informatics to identify the molecules at astrocyte-synapse junctions in vivo. We identify more than 100 proteins enriched at astrocyte-neuronal junctions. We find novel adhesion molecules highly expressed in cortical astrocytes whose deletion dramatically alters inhibitory synaptic formation and functions. Using Split-TurboID we thus establish a new mechanism by which astrocytes coordinate GABAergic synapse formation and functions via a chemo-affinity code of the tripartite synapse.		2021/10/1　10:00～12:00　ZOOM A会場 S9-2 プルキンエ細胞のDSCAM はバーグマングリアのGLAST のシナプス局在と小脳シナプス発生を制御する Purkinje cell DSCAM regulates Bergmann glial GLAST localization near synaptic cleft and cerebellar synapse development ^○有村奈利子国立精神・神経医療研究センター神経研究所病態生化学研究部 ^○Nariko Arimura Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry Glutamate uptake is essential for maintaining resting extracellular glutamate concentrations below levels that activate glutamate receptors. It is mediated by membrane glycoproteins called glutamate transporters. Glutamate transporters constitute a gene family, the EAAT family including GLAST and GLT-1, the members of which have distinct distributions in the brain. GLAST and GLT-1 are localized in astroglial cells and distributed throughout the brain, but at different relative concentrations in different regions. Astrocytic membranes facing capillaries, pia, or stem dendrites were lower in glutamate transporters than those facing nerve terminals, axons, and spines (Chaudhry et al., Neuron, 15(3), 1995). This localization of glutamate transporters appears to be carefully regulated; however, its regulatory mechanism has been still unrevealed. We now report that down syndrome cell adhesion molecule (DSCAM) in Purkinje cells (PC) regulates the peri-synaptic localization of GLAST in Bergmann glia (BG), the cerebellar astrocytes that thoroughly enwrap PC synapses, and that its regulation is critical for the climbing fiber (CF)-translocation and synapse formation in the developmental cerebellum. Impaired glutamate clearance in the -Dscam-deficient cerebellum was confirmed by electrophysiological analyses. DSCAM is essential for CF-synapse function to mediate normal motor learning, but not for gross motor performance or coordination. Our findings demonstrate the intercellular role of neural synaptic proteins in regulating glutamate clearance by modulating the localization of astrocytic glutamate transporters near the synaptic cleft. These results suggest that the Neuronal and astrocytic protein interactions are critical for synapse construction and function in the cerebellum.

2021/10/1　10:00～12:00　ZOOM A会場 S9-3 発達期シナプス刈り込みのアストロサイト活動依存性とメカニズム Astrocyte activity dependence and mechanisms of developmental synapse elimination ^○上阪直史東京医科歯科大学大学院医歯学総合研究科 ^○Naofumi Uesaka Dept Cognitive Neurobiology, Grad Sch Medi & Dent Sci, Tokyo Medical and Dental University, Tokyo Japan In the developing nervous system, synapse elimination in which some synapses are selectively strengthened and the other synapses are eliminated is a fundamental process for the completion of a functional neural circuit. In the neonatal cerebellum, multiple climbing fibers (CFs) innervate and form synapses on the soma of Purkinje cells (PCs). One CF is then selectively strengthened and translocated to the dendrites of the PC, and the other CFs remaining on the soma of the PC are eliminated. Bergmann glia, a unipolar astrocyte in the cerebellar cortex, is closely associated with PCs and has been shown to be involved in the maintenance of CF synapses. However, it is unclear whether and how Bergmann glia contributes to developmental CF synapse elimination. We have tested the hypothesis that Ca²⁺+ activity in Bergmann glia contributes to synapse elimination in the developing cerebellum. We found that there is spontaneous Ca²⁺+ activity in Bergmann glia during the process of CF synapse elimination. Analysis of synapse elimination in mice in which Ca²⁺+ activity in Bergmann glia was manipulated revealed that Ca²⁺+ activity in Bergmann glia functions to eliminate CF synapses remaining on the PC soma. In addition, morphological analysis confirmed that the elimination of CF terminals from the PC soma was impaired in mice in which Ca²⁺+ activity of Bergmann glia was manipulated. In this symposium, we would like to present our data on how Ca²⁺+ activity of Bergmann glia eliminated CFs and discuss the mechanism.		2021/10/1　10:00～12:00　ZOOM A会場 S9-4 アストロサイトによるシナプス再編と神経障害性疼痛 Astrocyte-mediated synapse remodeling in neuropathic pain ^○小泉修一山梨大学大学院総合研究部医学域薬理学 , 山梨GLIA センター ^○Schuichi Koizumi １.Dept Neuropharmacol, Interdiscipl Grad Sch Med, Univ Yamanashi, Yamanashi Japan ,２.Yamanashi GLIA Center After partial sciatic nerve ligation, astrocytes in the primary somatosensory (S1) cortex become reactive and cause mechanical allodynia via excess synapse remodeling, which is thought to involve metabotropic glutamate receptor 5 (mGluR5). We generated astrocyte-specific mGluR5 knockout mice and showed that the re-emergence of mGluR5 in S1 astrocytes was essential for a series of pain responses. mGluR5 was almost absent in adult healthy astrocytes, but re-emerged transiently in S1 astrocytes after partial sciatic nerve ligation. In this limited spatiotemporal timeframe, astrocytic mGluR5 caused Ca²⁺ excitation, the expression of multiple synaptogenic molecules, excess excitatory synaptogenesis, and persistent misconnected S1 networks, leading to mechanical allodynia. All these events were abolished by the astrocyte-specific deletion of mGluR5. In summary, astrocytes control dynamic synaptic plasticity, even in the adult brain, by turning a single molecule, mGluR5, on and off, which has a significant effect on subsequent brain functions.