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Activity-dependent regulation of glutamate receptor localization in Drosophila neuromuscular synapses
Abstracts / Neuroscience Research 58S (2007) S1–S244
S131
9 Analysis of subcellular localization of synapses in C. P2-a0 elgans RIA interneuron
P2-a12 Activity-dependent regulation of glutamate receptor
Tsubasa Kimata, Atsushi Kuhara, Yoshinori Tanizawa, Ikue Mori Nagoya University, Japan
Takako Morimoto-Tanifuji, Kengo Shibuya, Hiroyoshi Miyakawa School of Science, Tokyo University of Pharmacy and Life Sciences, Japan
Neural signal is transmitted via synapses, and thus subcellular localization of synapses is important for neural function. RIA interneuron essential for thermotaxis in C. elegans has a single neurite, but pre- and post-synaptic region are clearly divided within it, which is a suitable model for the analysis of subcellular localization of synapses. We conducted a screen for the mutants defective in localization of synapses in RIA by observing the presynapses using synaptic vesicle protein SNB-1 fused to fluorescent protein. From this screen we isolated seven mutants, although the penetrances of their phenotypes are low. Recently, we reported that ttx7 mutant lacking inositol monophosphatase (IMPase) shows abnormal localization of synaptic proteins in RIA, which leads to thermotaxis defect Tanizawa et al. [1]. We are now attempting to isolate suppressors for ttx-7. The screen has utilized the thermotaxis assay, which enables us to screen more genomes than screen with direct observation of synapses. We will then examine suppressor candidates as to whether the localization defect of synaptic proteins are also suppressed.
It is well known that neural activities can modulate synaptic responses. However, effects of neural activities on localization of neurotransmitter receptors have not been fully understood. Here, we investigated how neural activities modulate the content of two major components of glutamate receptor (GluR), GluRIIA and IIB, in Drosophila larval neuromuscular synapses. In eag-shaker mutants, that display greatly enhanced nerve activity, the content of both GluRIIA and IIB in synapses was enhanced. On the other hand, it was decreased in parats1 mutants if the synaptic activity was prevented at elevated temperatures. These results were a contrast to our previous findings that postsynaptic activation of CaMKII decreased GluRIIA but increased IIB content. Taken together, these results suggest that the neural activity modulates GluR content of synapses through CaMKII-independent way and there are several mechanisms that regulate the localization of GluR in synapses.
localization in Drosophila neuromuscular synapses
Research funds: Narisige Zoological Science Award and KAKENHI
[1] Tanizawa et al. 2006. Genes Dev.
Mechanisms of GABAB receptor-mediated inhibition of P2-a10 burst activities in mouse superior colliculus
Katsuyuki Kaneda 1,2 , Penphimon Phongphanphanee 1,2 , Yuchio Yanagawa 3 , Kunihiko Obata 4 , Tadashi Isa 1,2 1 Department of Development Physiology, National Institute of Physiological Science, Okazaki, Japan; 2 Graduate University for Advanced Studies, Japan; 3 Gunma University Graduate School of Medicine, Maebashi, Japan; 4 RIKEN, BSI, Wako, Japan We examined the role of GABAB receptors (GABAB Rs) for burst activities of neurons in the superior colliculus (SC), which may be related to saccade initiation, using slice preparations obtained from GAD67-GFP knock-in mice. Single electrical stimulation of the superficial gray layer (SGS) evoked burst EPSCs in non-GABAergic intermediate gray layer (SGI) neurons in the presence of a GABAA R antagonist. Addition of GABAB R antagonist CGP52432 (CGP) greatly increased the duration of the burst EPSCs, indicating that synaptically released GABA activates GABAB Rs. Similar effects were observed when CGP was locally applied to the SGS but not to the SGI, suggesting GABAB Rs localization in the SGS. Based on the results from a series of experiments, we concluded that both pre- and postsynaptic GABAB Rs localized in the SGS can be activated by synaptically released GABA during burst activities and limit the duration of burst activities in the SC.
P2-a13 Origins of the spontaneous depolarization wave in the embryonic rat CNS revealed by optical imaging with a voltagesensitive dye Yoko Momose-Sato 1,2 , Katsushige Sato 1 , Masae Kinoshita 1 Department of Physiology, Tokyo Medical & Dental University School of Medicine, Tokyo, Japan; 2 Department of Health & Nutrition, Kanto Gakuin University, College of Human & Environmental Studies, Yokohama, Japan
1
We previously reported that a widely propagating correlated neuronal activity (depolarization wave) is evoked by various sensory inputs in the embryonic CNS. Here, we examined the spontaneous depolarization wave and its origins. In E15-E16 rat embryos, spontaneous signals appeared in association with the rhythmic discharges of cranial MNs, and propagated widely. At E15, the spontaneous wave mostly originated in the cervicalupper lumbar cords. At E16, the wave was predominantly generated in the lumbosacral cord, although a wave associated with the second oscillatory burst was initiated in the rostral cord. At E16, a few waves also originated in the rostral ventrolateral medulla and the dorsomedial pons. When the influence of the caudal cord was removed, the contribution of the medulla and pons became more significant. These results show that the depolarization wave can be triggered by the spontaneous activity of multiple neuronal populations.
Research funds: KAKENHI 18200027, 18021039, HFSP
P2-a11 Involvement of Homer1a in the regulation of distribution of postsynaptic proteins Yuriko Inoue 1 , Hiroshi Udo 1 , Kaoru Inokuchi 2 , Hiroyuki Sugiyama 1 1 Graduate School of Systems, Life Ssciences, University of Kyushu, Fukuoka, Japan; 2 Mitsubishi-Kagaku Institute of Life Sciences, Tokyo, Japan Homer1a is induced by neural activities such as LTP or seizure. In cultured rat hippocampal neurons, we examined the changes in the distribution of synaptic proteins such as PSD95, Homer1c, or F-actin, after neuronal stimulations. When the cells were stimulated with glutamate, the numbers of the clusters of these proteins in dendrites decreased transiently for 1 h, then recovered, and several hours later reached the levels higher than the initial level before stimulation. The time courses of the biphasic changes in the distribution of these proteins are indistinguishable from each other. These changes were suppressed when the cellular Homer1a was knocked down by RNAi before the stimulation. It is suggested that the distribution changes may represent remodeling of the synapses through biphasic de-clustering and re-formation processes, and that Homer1a may play important roles in these processes.
P2-a14 An F-BAR/EFC protein rapostlin regulates dendritic spine development Tetsuhiro Kakimoto, Hironori Katoh, Manabu Negishi Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan Dendritic spines are tiny protrusions that receive most excitatory synaptic inputs. Dendritic spines show structural plasticity during development and in response to synaptic activity. However, the regulation mechanism of membrane trafficking for spine formation is poorly understood. Here we studied neuronal function of rapostlin that has an F-BAR/EFC domain with a membrane invaginating property. Rapostlin is strongly expressed in developing brain including hippocampus and cerebral cortex in late developmental stages. Knockdown of rapostlin by siRNA in primary cultured rat hippocampal neurons reduces spine density and size. These results suggest the implication of rapostlin in spine development through the regulation of membrane trafficking. We are now further dissecting the detailed function of rapostlin in spine formation. Research fund: KAKENHI (17079003)
S131
9 Analysis of subcellular localization of synapses in C. P2-a0 elgans RIA interneuron
P2-a12 Activity-dependent regulation of glutamate receptor
Tsubasa Kimata, Atsushi Kuhara, Yoshinori Tanizawa, Ikue Mori Nagoya University, Japan
Takako Morimoto-Tanifuji, Kengo Shibuya, Hiroyoshi Miyakawa School of Science, Tokyo University of Pharmacy and Life Sciences, Japan
Neural signal is transmitted via synapses, and thus subcellular localization of synapses is important for neural function. RIA interneuron essential for thermotaxis in C. elegans has a single neurite, but pre- and post-synaptic region are clearly divided within it, which is a suitable model for the analysis of subcellular localization of synapses. We conducted a screen for the mutants defective in localization of synapses in RIA by observing the presynapses using synaptic vesicle protein SNB-1 fused to fluorescent protein. From this screen we isolated seven mutants, although the penetrances of their phenotypes are low. Recently, we reported that ttx7 mutant lacking inositol monophosphatase (IMPase) shows abnormal localization of synaptic proteins in RIA, which leads to thermotaxis defect Tanizawa et al. [1]. We are now attempting to isolate suppressors for ttx-7. The screen has utilized the thermotaxis assay, which enables us to screen more genomes than screen with direct observation of synapses. We will then examine suppressor candidates as to whether the localization defect of synaptic proteins are also suppressed.
It is well known that neural activities can modulate synaptic responses. However, effects of neural activities on localization of neurotransmitter receptors have not been fully understood. Here, we investigated how neural activities modulate the content of two major components of glutamate receptor (GluR), GluRIIA and IIB, in Drosophila larval neuromuscular synapses. In eag-shaker mutants, that display greatly enhanced nerve activity, the content of both GluRIIA and IIB in synapses was enhanced. On the other hand, it was decreased in parats1 mutants if the synaptic activity was prevented at elevated temperatures. These results were a contrast to our previous findings that postsynaptic activation of CaMKII decreased GluRIIA but increased IIB content. Taken together, these results suggest that the neural activity modulates GluR content of synapses through CaMKII-independent way and there are several mechanisms that regulate the localization of GluR in synapses.
localization in Drosophila neuromuscular synapses
Research funds: Narisige Zoological Science Award and KAKENHI
[1] Tanizawa et al. 2006. Genes Dev.
Mechanisms of GABAB receptor-mediated inhibition of P2-a10 burst activities in mouse superior colliculus
Katsuyuki Kaneda 1,2 , Penphimon Phongphanphanee 1,2 , Yuchio Yanagawa 3 , Kunihiko Obata 4 , Tadashi Isa 1,2 1 Department of Development Physiology, National Institute of Physiological Science, Okazaki, Japan; 2 Graduate University for Advanced Studies, Japan; 3 Gunma University Graduate School of Medicine, Maebashi, Japan; 4 RIKEN, BSI, Wako, Japan We examined the role of GABAB receptors (GABAB Rs) for burst activities of neurons in the superior colliculus (SC), which may be related to saccade initiation, using slice preparations obtained from GAD67-GFP knock-in mice. Single electrical stimulation of the superficial gray layer (SGS) evoked burst EPSCs in non-GABAergic intermediate gray layer (SGI) neurons in the presence of a GABAA R antagonist. Addition of GABAB R antagonist CGP52432 (CGP) greatly increased the duration of the burst EPSCs, indicating that synaptically released GABA activates GABAB Rs. Similar effects were observed when CGP was locally applied to the SGS but not to the SGI, suggesting GABAB Rs localization in the SGS. Based on the results from a series of experiments, we concluded that both pre- and postsynaptic GABAB Rs localized in the SGS can be activated by synaptically released GABA during burst activities and limit the duration of burst activities in the SC.
P2-a13 Origins of the spontaneous depolarization wave in the embryonic rat CNS revealed by optical imaging with a voltagesensitive dye Yoko Momose-Sato 1,2 , Katsushige Sato 1 , Masae Kinoshita 1 Department of Physiology, Tokyo Medical & Dental University School of Medicine, Tokyo, Japan; 2 Department of Health & Nutrition, Kanto Gakuin University, College of Human & Environmental Studies, Yokohama, Japan
1
We previously reported that a widely propagating correlated neuronal activity (depolarization wave) is evoked by various sensory inputs in the embryonic CNS. Here, we examined the spontaneous depolarization wave and its origins. In E15-E16 rat embryos, spontaneous signals appeared in association with the rhythmic discharges of cranial MNs, and propagated widely. At E15, the spontaneous wave mostly originated in the cervicalupper lumbar cords. At E16, the wave was predominantly generated in the lumbosacral cord, although a wave associated with the second oscillatory burst was initiated in the rostral cord. At E16, a few waves also originated in the rostral ventrolateral medulla and the dorsomedial pons. When the influence of the caudal cord was removed, the contribution of the medulla and pons became more significant. These results show that the depolarization wave can be triggered by the spontaneous activity of multiple neuronal populations.
Research funds: KAKENHI 18200027, 18021039, HFSP
P2-a11 Involvement of Homer1a in the regulation of distribution of postsynaptic proteins Yuriko Inoue 1 , Hiroshi Udo 1 , Kaoru Inokuchi 2 , Hiroyuki Sugiyama 1 1 Graduate School of Systems, Life Ssciences, University of Kyushu, Fukuoka, Japan; 2 Mitsubishi-Kagaku Institute of Life Sciences, Tokyo, Japan Homer1a is induced by neural activities such as LTP or seizure. In cultured rat hippocampal neurons, we examined the changes in the distribution of synaptic proteins such as PSD95, Homer1c, or F-actin, after neuronal stimulations. When the cells were stimulated with glutamate, the numbers of the clusters of these proteins in dendrites decreased transiently for 1 h, then recovered, and several hours later reached the levels higher than the initial level before stimulation. The time courses of the biphasic changes in the distribution of these proteins are indistinguishable from each other. These changes were suppressed when the cellular Homer1a was knocked down by RNAi before the stimulation. It is suggested that the distribution changes may represent remodeling of the synapses through biphasic de-clustering and re-formation processes, and that Homer1a may play important roles in these processes.
P2-a14 An F-BAR/EFC protein rapostlin regulates dendritic spine development Tetsuhiro Kakimoto, Hironori Katoh, Manabu Negishi Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan Dendritic spines are tiny protrusions that receive most excitatory synaptic inputs. Dendritic spines show structural plasticity during development and in response to synaptic activity. However, the regulation mechanism of membrane trafficking for spine formation is poorly understood. Here we studied neuronal function of rapostlin that has an F-BAR/EFC domain with a membrane invaginating property. Rapostlin is strongly expressed in developing brain including hippocampus and cerebral cortex in late developmental stages. Knockdown of rapostlin by siRNA in primary cultured rat hippocampal neurons reduces spine density and size. These results suggest the implication of rapostlin in spine development through the regulation of membrane trafficking. We are now further dissecting the detailed function of rapostlin in spine formation. Research fund: KAKENHI (17079003)