一般口演（Oral）

Oral Neuronal Circuit Plasticity 一般口演神経回路可塑性

7月28日（日）11:50～12:05　第9会場（朱鷺メッセ　3F　306+307） 4O-09a2-1 AMPA Receptor Ubiquitination-deficient Knock-in Mice Display Enhanced Spatial Learning Sumasri Guntupalli（Guntupalli Sumasri）¹，Mei Zhou（Zhou Mei）^1,2，Mitchell Ringuet（Ringuet Mitchell）^1,2，Dianel Blackmore（Blackmore Dianel）^1,2，Frank Koentgen（Koentgen Frank）³，Dhanisha Jhaveri（Jhaveri Dhanisha）^1,4，Jocelyn Widagdo（Widagdo Jocelyn）^1,2，Victor Anggono（Anggono Victor）^1,2 ¹Queensland Brain Institute ²Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia. ³Ozgene Pty Ltd., Bentley, Western Australia, Australia. ⁴. Mater Research Institute, The University of Queensland, Brisbane, Queensland, Australia. AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors (AMPARs) are the principal receptors that mediate fast excitatory neurotransmission in the brain. Dynamic modulation of the number of AMPARs at synapses underlies activity-dependent regulation of synaptic strength, an essential process in synaptic plasticity, learning and memory. All AMPAR subunits, GluA1-4, undergo post-translational ubiquitination following ligand binding, which act as a signal that directs the intracellular sorting of AMPARs toward late endosomes for degradation. Previously, we have mapped the GluA1 and GluA2 binding sites to the lysine residues in their carboxyl-terminal domains. In order to understand the functional role of AMPAR ubiquitination in vivo, we generated the GluA1 K868R and GluA2 K870/882R knock in mice, where the major ubiquitination sites in the GluA1 and GluA2 subunits were mutated to arginine residues. These mice showed normal gross brain cytoarchitecture and bred normally. Behaviourally, these mice performed significantly better than their wild-type littermates in an active-place avoidance task, a hippocampal-dependent spatial learning and memory test in rodents. No obvious differences in locomotor activity or anxiety were observed in the open-field test and elevated plus maze task, respectively. Our results support our overall hypothesis that stabilisation of AMPARs by inhibiting GluA1 and GluA2 ubiquitination, can enhance cognitive function in vivo.		7月28日（日）12:05～12:20　第9会場（朱鷺メッセ　3F　306+307） 4O-09a2-2 活性酸素 - 8-ニトロ-cGMPシグナルの小脳長期抑圧への関与 Sho Kakizawa（柿澤昌）¹，Shogo Endo（遠藤昌吾）² ¹京都大院薬生体分子認識 ²都健康長寿医療セ記憶神経科学 Long-term depression (LTD) at parallel fiber to Purkinje cell synapse in the cerebellum is the cellular basis for cerebellar-dependent motor learning. Although several types of signaling molecules, such as type 1 metabotropic glutamate receptor (mGluR1) and phospholipase C beta (PLC beta) for example, are indicated to be essential for the induction of cerebellar LTD, the molecular mechanism for long-term memory has yet to be determined. 8-nitro-cGMP is an intracellular signaling molecule, produced by enzymatic activity of guanylyl cyclase in the presence of nitric oxide and reactive oxygen species (ROS). In contrast to cGMP, 8-nitro-cGMP is a long-life molecule and possibly activate protein kinase G (PKG) for a long time, due to its resistance to PDE-dependent catalysis. Therefore, we hypothesized that 8-nitro-cGMP is a key molecule for long-term memory and is involved in cerebellar LTD. In the present study, we examined possible involvement of 8-nitro-cGMP in cerebellar LTD using pharmacological approach. Application of 8-nitro-cGMPS, an analog for 8-nitro-cGMP, to cerebellar Purkinje cells significantly inhibited the induction of cerebellar LTD in acute cerebellar slices from young-adult mice. Combinational application of superoxide dismutase (SOD) with catalase, which catalyze superoxide and hydrogen peroxide, respectively, also impaired cerebellar LTD. Furthermore, treatment of the cerebellar slice with apocynin, a broad antagonist of NADPH oxidase (Nox) which produce ROS, abolished the LTD induction. These results strongly indicate that 8-nitro-GMP is essential for the induction of cerebellar LTD. Our observations also suggest that ROS has physiological function in brain systems, and is involved in learning and memory.

7月28日（日）12:20～12:35　第9会場（朱鷺メッセ　3F　306+307） 4O-09a2-3 環境刺激による新生児脳RNAスプライシングの制御 Fuminori Tsuruta（鶴田文憲）¹，Jeahyun Kim（金材炫）¹，Takumi Taketomi（武富巧）²，Tomoki Chiba（千葉智樹）¹ ¹筑波大院　生命環境科学 ²筑波大　生命環境 In mammals, a wide variety of environmental stimuli play important roles in establishing the functions of the postnatal brain. During postnatal stages, these stimuli enforce the diversity and complexity of synaptic connectivity and neuronal circuit, resulting in affecting various critical periods. Recently, it has been reported that RNA splicing has effects on the brain function a time- and region-dependent manner, regulating synaptic connectivity and neuronal circuit. However, it has not been elucidated the molecular mechanisms linking environmental stimuli to the neuronal function involved in RNA splicing after birth. Here, we report that ubiquitin specific peptidase 15 (USP15) is accumulated in the nucleus after visual stimulation. Previously we found that USP15 deubiquitinates Terminal Uridylyl Transferase 1 (TUT1), contributing U6-snRNA stabilization and proper RNA splicing. In the brain, USP15 exists in both nucleus and cytoplasm in layer 5 cortical neurons. On the other hand, USP15 is not accumulated in the nucleus in the absence of light exposure under the dark condition. Using the microarray analysis, we identified that a mutant of Hevin, which is a secreted protein and accelerate the synaptic formation, is one of the splicing targets influenced by USP15 deficiency. This mutant lacks a calcium binding domain, EF-hand at the C-terminal region. We also found that this mutant hampers the trafficking pathway and is accumulated in the endoplasmic reticulum. Taken together, our results suggest that visual stimulation during postnatal stages promotes USP15 accumulation in the nucleus in layer 5 cortical neurons, followed by controlling the proper RNA splicing in the nucleus. A defect in this machinery produce multiple splicing mutants like Hevin and causes neuronal dysfunctions. These finding may provide the possibility that USP15 act as a key mediator that link environmental stimuli to the establishment of the proper neuronal circuit.		7月28日（日）12:35～12:50　第9会場（朱鷺メッセ　3F　306+307） 4O-09a2-4 Mechanism of local protein synthesis at the synapse by miRNA decay and its implications in synaptic plasticity Sourav Banerjee（Banerjee Sourav），Sarbani Samaddar（Samaddar Sarbani），Balakumar Srinivasan（Srinivasan Balakumar） National Brain Research Centre Long-term adaptive changes at the synapse via local protein synthesis fine-tune neural circuit function involved in complex cognitive function, such as memory formation. Among various regulatory switches, microRNA (miRNA) mediated control of protein synthesis at the activated synapse provide the template for neuronal adaptability to extracellular signals. However, how miRNAs are dynamically regulated in response to neuronal activity and influence protein synthesis at the activated synapses to make adaptive modifications is poorly understood. To address these pressing questions, we have analyzed miRNA activity influenced by glutamate stimulation of isolated synaptic compartment from hippocampus. We observed that subset of miRNAs are selectively degraded via NMDA receptor activation as detected by miRNA array analysis. Furthermore, contextual fear conditioning of mice also showed degradation of similar set of miRNAs including miR-9, miR23b and miR-138 in hippocampal synapses. Our sensor assay has determined that these miRNAs are significantly degraded within ~10 minute after photo-uncaging of glutamate. This observation indicates that time scale of rapid miRNA decay coincide with time window required for protein synthesis-dependent form of synaptic plasticity. Our data showed that RNA binding protein, HuR regulates the selective degradation of miRNAs at the synapses. To obtain a mechanistic insight into de novo protein synthesis by miRNA decay at the synapse, we have identified targets of miR-9 and miR-23b by reporter assay as well as analyzing expression of endogenous target by western blot after inhibition of these miRNAs. We have confirmed synaptic localization of miRNAs and their respective target by in situ hybridization. Our translation reporter assay using mDendra fused to 3'UTRs of target transcript containing miRNA binding sites and photo uncaging of glutamate showed that rapid degradation of miR-9 and miR-23b leads to de novo protein synthesis from their respective target transcripts within ~15 minute. We also observed that this localized translation induced by miRNA decay is prevented by HuR knockdown. Currently, we are analyzing how localized protein synthesis by miRNA decay modulates synaptic response using whole cell patch clamp recording. Taken together, our data provide a significant insight into causal relationship between miRNA decay and its impact on memory formation through translational control point at the synapse.