公募シンポジウム

公募シンポジウム8【マルチスケールアプローチによるカルシウムシグナル動態の制御機構と機能的役割の解明】

2021/9/30　17:00～19:00　ZOOM C会場 S8-1 分子動力学計算と生理実験によるリアノジン受容体のカルシウム放出機構の解析 Analysis of Ca2+ release mechanism of ryanodine receptor by molecular dynamics simulation and physiological experiments ^○山澤德志子東京慈恵会医科大学分子生理学講座 ^○Toshiko Yamazawa Jikei Univ. Sch. Med., Tokyo, Japan Ca²⁺-induced Ca²⁺ release (CICR) is mediated by ryanodine receptors (RyRs), a Ca²⁺ release channel in the sarcoplasmic/endoplasmic reticulum, and plays an important role in various tissues including neurons and muscles. Abnormalities of CICR cause various muscle and arrhythmogenic heart diseases. Recent near-atomic structures of RyRs by cryo-EM enable us to understand the molecular mechanism of CICR. We combined functional studies and molecular dynamics (MD) simulation of type 1 ryanodine receptor (RyR1) bearing disease-associated mutations at the N-terminal region. When expressed in HEK293 cells, the mutant RyR1 caused abnormalities in Ca²⁺ homeostasis. MD simulation of the mutant RyR1 revealed that alterations of hydrogen bonds/salt bridges between N-terminal domains, consisting of A, B and C sub-domains, strongly correlate with the channel function of RyR1. In the neurons, we found that nitric oxide (NO) directly activates RyRs, which induce Ca²⁺ release from intracellular stores (NO-induced Ca²⁺ release; NICR), and NICR is involved in NO-induced neuronal cell death. These findings suggest that NICR-mediated Ca²⁺ signaling plays important roles in pathophysiological functions in the brain and is a potential therapeutic target for the treatment of ischemic brain disease. Next, we have recently identified that heat directly activates RyR1, which induce Ca²⁺ release from intracellular stores (heat-induced Ca²⁺ release; HICR). In this symposium, I would also like to introduce the functional role of HICR.		2021/9/30　17:00～19:00　ZOOM C会場 S8-2 リアノジン受容体のレドックス修飾の運動学習と脳機能老化への関与 Involvement of redox modification of ryanodine receptor in motor learning and brain aging ^○柿澤昌京都大学大学院薬学研究科生体分子認識学 ^○Sho Kakizawa Dept Biol Chem, Grad Sch Pharmaceu Sci, Kyoto Univ Ca²⁺ signal is involved in various biological events, including synaptic plasticity underlying higher brain functions. Intracellular Ca²⁺ levels are affected by influx from extracellular fluid and release from intracellular Ca²⁺ store. However, the regulatory mechanism and functional role of Ca²⁺ release in neuronal cells have not been fully understood.We recently identified a novel type of intracellular Ca²⁺ release, nitric oxide-induced Ca²⁺ release (NICR) in cerebellar Purkinje cells (PC). NICR is induced by redox modification, S-nitrosylation by nitric oxide (NO), of type 1 ryanodine receptor (RyR1), a Ca²⁺ release channels. To examine functional role of RyR1 nitrosylation, we generated knock-in (KI) mice which express RyR1 lacking the S-nitrosylation cite. In KI cerebellum, NICR and long-term potentiation at parallel fiber (PF) – PC synapse (PF-LTP) were impaired. Furthermore, extinction phase of eyeblink conditioning was also inhibited. These observations indicate essential role of RyR1 nitrosylation on motor learning.PF-LTP is also inhibited in aged mice (> 20 months old). Because oxidation of functional molecules is accumulated in aged brain, we examined possible involvement of reactive oxygen species (ROS) in PF-LTP inhibition. Pretreatment of cerebellar slices with ROS impaired PF-LTP, NICR and S-nitrosylation of RyR1. These observations were reproduced in aged cerebellum, the results indicating involvement of ROS in age-dependent decline in brain functions through inhibition of S-nitrosylation-mediated signaling.

2021/9/30　17:00～19:00　ZOOM C会場 S8-3 神経科学におけるメレオロジカルな誤謬を避けるためのマルチスケール・マルチモーダルCa²⁺ イメージング Multiscale and multimodal Ca2+ imaging to avoid mereological fallacy in neuroscience ^○小山内実大阪大学大学院医学系研究科 ^○Makoto Osanai Osaka University Graduate School of Medicine “Mereological fallacy is the fallacy of ascribing psychological attributes to parts of an animal that can only intelligibly be ascribed to the animal as a whole.” (Smit & Hacker, 2014). Many scientists warn of the state of neuroscience in recent years. “Mereology” is the logic of part/whole relations. The mereological fallacy is ascribed from the idea that the whole can be represented by a set of parts. The nervous system has a hierarchical organization from neurons to a huge complex network and processes information through complex interactions within and between each level of the hierarchy. Thus, a set of information from parts cannot explain the brain functions as a whole. It is necessary to understand the bidirectionality of the parts and the whole and their interactions to reveal the mechanisms of brain function avoiding the mereological fallacy. Along with the above idea, we are developing the multiscale-multimodal Ca²⁺ imaging methods that enable the multi-scale analysis of the brain functions. For in vivo whole-brain activity analysis, we selected the quantitative activation-induced manganese-enhanced MRI (qAIM-MRI) method. qAIM-MRI is based on the use of Mn²⁺ as a surrogate marker of Ca²⁺ influx. Mn²⁺ shortens the longitudinal relaxation time (T1) of H+. Therefore, qAIM-MRI can measure the history of the neuronal activities non-invasively. For in vivo local circuit imaging, we are developing the ultra-thin fluorescence endoscope imaging system (U-FEIS). U-FEIS can record the multicellular neuronal activities from the deep brain region. To reveal the cellular and molecular mechanisms for exhibiting brain function, in vitro experiment is needed. Thus, we conduct a fluorescent imaging study on brain slice preparations. These three imaging methods can be applied to the same animal and can be combined with behavioral and biochemical studies. This experimental strategy may provide a research foundation for understanding the relationship between parts and the whole brain, avoiding mereological fallacies in neuroscience.		2021/9/30　17:00～19:00　ZOOM C会場 S8-4 カルシウムシグナルを介した認知・精神機能調節 Regulation of cognitive/mental function via calcium signal ^○森口茂樹東北大学大学院薬学研究科・医薬品開発研究センター ^○Shigeki Moriguchi Research Center for Pharmaceutical development, Graduate School of Pharmaceutical Sciences, Tohoku University Calcium signal is essential for regulation of cognitive/mental function in CNS. We previously reported calcium/calmodulin-dependent protein kinases (CaMKs) are critical for cognitive/mental function in hippocampus. In this symposium, we present the role of CaMKs relative to receptor, channel or transporter in hippocampus. We first report the changes of glucose concentration enhances long-term potentiation and calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation in hippocampus. This result indicated that ATP production from mitochondria is associated with cognitive function in hippocampus. Here we next report that a novel target of Alzheimer’s disease (AD) existing drug memantine, ATP-sensitive K⁺ (K_ATP) channels are implicated in improvement of cognitive and mental disorders. We observed that inhibition of Kir6.2 channel by memantine improves both memory impairment and perturbed NMDAR-dependent LTP in APP23 mouse hippocampus. In addition, we also confirmed that Kir6.2 heterozygous mutant mice exhibit severe memory deficits and hippocampal LTP impairment that could not be rescued by memantine administration. By contrast, we show that memantine enhances adult neurogenesis in the subgranular zone of the hippocampal dentate gyrus (DG) and improves depressive-like behaviors via inhibition of Kir6.1 channel in olfactory bulbectomized (OBX) mice. Taken together, we propose a novel strategy that memantine inhibits K_ATP channel activities, thereby improving cognitive/mental disorders in AD patients.