興奮性とシナプス機能の分子制御機構 Molecular control of excitability and synapse function
O1-7-1-1 恒温動物の神経興奮を規定する分子基盤；温度センサーTRPV4による脳内温度の感知 TRPV4 is a critical determinant for neuronal excitability through its converter function from temperature to electrical activity in mammalian brain ○柴崎貢志1, 山田勝也2, 三輪秀樹1, 富永真琴3, 石崎泰樹1 ○Koji Shibasaki1, Katsuya Yamada2, Hideki Miwa1, Makoto Tominaga3, Yasuki Ishizaki1 群馬大院・医・分子細胞1, 弘前大院・医・統合生理2, 岡崎統合バイオ・細胞生理3 Dept Cell Neurobiol, Gunma Univ Grad Sch of Medicine1, Hirosaki Univ Grad Sch of Medicine2, Okazaki Instit for Integrative Biosci3 Physiological brain temperature is an important determinant of brain functions, and it is well established that changes in brain temperature dynamically influence hippocampal neuronal activity. We previously revealed that the thermo-sensor TRPV4 (activated above 34°C) is activated by physiological brain temperature in hippocampal neurons and thereby controls their excitability in vitro (J. Neurosci. 2007, Shibasaki et al.). Here, we examined whether TRPV4 regulates neuronal excitability through its activation by brain temperature in vivo. We developed an original device for cooling of local brain temperature to inactivate TRPV4. The cooling treatment clearly demonstrated that constitutive TRPV4 activation was occurred in mouse brain in vivo, and we found that hippocampal theta-frequency electroencephalogram (EEG) activities in TRPV4KO mice during wake periods were significantly reduced compared with those in WT mice. Furthermore, slice patch clamp recordings from dentate gyrus of hippocampus revealed that the resting membrane potentials of WT neurons were further depolarized compared with those of TRPV4KO neurons at 35°C. Depending on the differences of the resting membrane potentials, WT neurons had significantly smaller fEPSPs and higher firing patterns than KO neurons at 35°C (above TRPV4 activation), however, the differences were abolished at 30°C through the inactivation of TRPV4 in WT neurons. Taken together, for the first time we reveal that TRPV4 is an important transducer that converts brain temperature into neuronal electrical excitability in mammals in vivo.	O1-7-1-2 アクティブゾーン蛋白質CASTのリン酸化によるシナプス短期可塑性の制御 CAST Phosphorylation Mediates Short-term Synaptic Depression ○大塚稔久1, 飛田耶馬人1, 馬歓2, 谷藤章太2, 北島勲3, 持田澄子2 ○Toshihisa Ohtsuka1, Yamato Hida1, Huan Ma2, Shota Tanifuji2, Isao Kitajima3, Sumiko Mochida2 山梨大・大学院医学工学総合研究部・生化学第一1, 東京医科大・細胞生理学2, 富山大・大学院医学薬学研究部・臨床分子病態検査学3 Dept Biochem, Graduate School of Medicine/Faculty of Medicine,Univ of Yamanashi, Yamanashi1, Dept Physiol, Tokyo Medical University, Tokyo2, Dept Clinical and Molecular Psthol, University of Toyama, Toyama3 Although active zone (AZ) proteins control synaptic efficacy, how the functions of these proteins are coupled to neuronal activity is largely unknown. Here, we show that phosphorylation of CAST, a protein associated with the AZ cytomatrix, controls synaptic efficacy in sympathetic neurons. An N-terminal region of CAST is phosphorylated in vitro by a presynaptic kinase SAD-B. CAST phosphorylation occurred upon membrane depolarization. Moreover, expression of pseudophosphorylated CAST reduced presynaptic readily-releasable vesicle (RRP) pool size and delays reloading of the RRP after repetitive activity. In contrast, a non-phosphorylatable form of CAST accelerated RRP reloading. Finally, the former decreased synaptic depression, while the latter increased depression. These results suggest that activity-dependent phosphorylation of CAST controls synaptic depression by regulating the reloading of synaptic vesicles into the RRP.
O1-7-1-3 細胞極性の制御因子群がシナプスに於いて果たす役割 Roles of Cell Polarity Regulators at Mammalian Synapses ○岸将史1, 永岡唯宏1, 上村駿1, 犬束歩1, 渡辺愛1, 酒井清子2, 藤澤信義2, 横山峯介2, 田渕克彦3, 重本隆一3五十嵐道弘5 ○Masashi Kishi1, Tadahiro Nagaoka1, Shun Uemura1, Ayumu Inutsuka1, Ai Watanabe1, Seiko Sakai2, Nobuyoshi Fujisawa2, Minesuke Yokoyama2, Katsuhiko Tabuchi3, Ryuichi Shigemoto3, Joshua Sanes4, Michihiro Igarashi55 新潟大院・医歯学系・分子ニューロ1, 新潟大・脳研・動物資源2, 生理研・大脳皮質・脳形態3, ハーバード・MBC4, 新潟大・医歯学系・分子細胞機能5 Lab Mol Neuroimag, Niigata U, Niigata1, Brain Inst, Niigata U, Niigata2, Div Cereb Struct, Natl Inst Physiol Sci, Okazaki3, Harvard MBC, Boston, USA4, Div Mol Cell Biol, Niigata U, Niigata5 It has been revealed that neuronal polarization, which is represented by differentiation of axons and dendrites, is regulated by molecular signaling that determines the apico-basal polarity of the epithelia. Although these polarity proteins are highly expressed in the mammalian adult brains, their roles on the neural circuits remain to be elucidated. During the immunological screen utilizing mature cultures of rat hippocampal neurons, we found that some of the polarity proteins are enriched at the synapses. Data obtained from siRNA-mediated gene silencing indicated that they are required for normal differentiation of synaptic structures. We are currently analyzing how these polarity regulators are required for synapses. Results on our cell biological analysis and biochemical assays will be presented.	O1-7-1-4 Elfn1のソマトスタチン陽性細胞を含む海馬の抑制性神経回路における役割 Role of Elfn1 in hippocampal inhibitory neural circuits containing somatostatin-positive neurons ○富岡直子1, 宮本浩行2,3, 畑山実1, 守村直子1, 松本圭史1, 鈴木俊光4, 小田川摩耶1, 小高由梨1, 岩山佳美5, 山田一之6, 吉川武男5, 山川和弘4, 有賀純1 ○Naoko H. Tomioka1, Hiroyuki Miyamoto2,3, Minoru Hatayama1, Naoko Morimura1, Yoshifumi Matsumoto1, Toshimitsu Suzuki4, Maya O. Odagawa1, Yuri S. Odaka1, Yoshimi Iwayama5, Kazuyuki Yamada6, Takeo Yoshikawa5, Kazuhiro Yamakawa44, Jun Aruga1 理研BSI行動発達障害1, 理研BSIシナプス分子機構2, 科学技術振興機構さきがけ3, 理研BSI神経遺伝4, 理研BSI分子精神科学5, 理研BSI動物資源開発6 Lab. Behav. Dev. Disord., RIKEN BSI, Saitama, Japan1, Lab. Neurobiol. Synapse, RIKEN BSI, Saitama, Japan2, PRESTO, JST, Satiama, Japan3, Lab. Neurogenet., RIKEN BSI, Saitama, Japan4, Lab. Molecular Psychiatry, RIKEN BSI, Saitama, Japan5, RRC, RIKEN BSI, Saitama, Japan6 GABAergic interneurons are highly heterogeneous, and much is unknown about specification and functional roles of their neural circuits. We show here that the transmembrane protein Elfn1 (extracellular-leucine-rich repeat fibronectin domain1) in somatostatin-containing interneurons (SOM-INs) in the hippocampus is a critical postsynaptic component that induces mGluR7-positive presynaptic structures in excitatory neurons. Elfn1 protein increased during postnatal development and localized to postsynaptic sites of SOM-INs in the hippocampal CA1 stratum oriens and dentate gyrus hilus. Elfn1 KO mice have deficits in mGluR7 recruitment to synaptic sites with SOM-INs, and show abnormal spiking in electroencephalogram recordings accompanied by touch-sensitive seizures, hyperactivity and attention deficits. In patients with epilepsy and ADHD, we found damaging missense mutations that are clustered in the C-terminal region required for recruitment of the mGluR7. These results reveal a novel mechanism for interneuron subtype-specific neural circuit formation and define a common basis bridging the neurological disorders like epilepsy and ADHD.

上部に戻る

前に戻る