シンポジウム

シンポジウム Understanding neural functions and diseases from brain-derived neurotrophic factor

3S2-1 Regulation of BDNF gene expression and its possible role in neural functions and diseases Fukuchi Mamoru，Tabuchi Akiko，Tsuda Masaaki Dept. Biol Chem., Grad. Sch. of Med. ＆ Pharm. Sci., Univ. of Toyama It has been widely accepted that the expression of BDNF gene is controlled in a neuronal activity-dependent manner. We have investigated molecular mechanisms underlying the activity-dependent expression of Bdnf. Here we especially focused on the regulation of Bdnf expression by stimulation of G protein-coupled receptor（GPCR）, which is a major receptor for neuromodulators such as monoamines and neuropeptides. Using primary culture of cortical cells, we found that the stimulation of PAC1, a Gs/q-coupled GPCR, with pituitary adenylate cyclase-activating polypeptide（PACAP）selectively activated NMDA receptor（NMDAR）-calcineurin pathway, resulting in the induction of Bdnf expression through CREB and its co-activator, CREB-regulated transcriptional co-activator 1（CRTC1）. Interestingly, this induction of Bdnf was similarly observed when the cells were treated with other Gs- or Gq-coupled GPCR agonists such as SKF38393, isoproterenol, corticotropin-releasing factor（CRF）, and neurotensin. These results suggest that the selective activation of the NMDAR-calcineurin pathway is generally induced by the stimulation of Gs/q-coupled GPCR in neurons. It is well known that CREB, CRTC1, and BDNF contribute to expressing long-lasting changes in neural functions such as learning and memory. Moreover, dysregulation of neuromodulatory systems, such as dopaminergic and serotonergic signaling, is suggested to be related to neural and psychiatric disorders including depression and schizophrenia. Taken together, the GPCR-mediated Bdnf expression through the NMDAR-calcineurin-CRTC1-CREB pathway would contribute to plasticity-related phenomena and the disruption of this regulation may be related to pathogenesis of psychiatric disorders.		3S2-2 CAPS2-The positive regulation factor of BDNF secretion and the candidate gene for autism Shinoda Yo^1,2，Sadakata Tetsushi³，Hirase Hajime²，Furuichi Teiichi^1,2 ¹Fac of Sci and Tech, Tokyo Univ of Sci，²RIKEN BSI，³Adv Sci Res Leaders Develop Unit, Gumma Univ Calcium-dependent activator protein for secretion 2（CAPS2）plays a role in regulation of dense-core vesicle secretion and is associated with autism susceptibility. In this study, we analyzed CAPS2-mediated secretion of brain-derived neurotrophic factor（BDNF）and cellular and behavioral phenotypes of CAPS2 knockout（KO）mice. CAPS2 KO mice had significant reduction in BDNF levels in the hippocampus compared to their wild type（WT）littermates. Time-lapse live cell imaging showed that overexpression of exogenous CAPS2 enhanced quantity and kinetics of activity-dependent BDNF-pHluorin release from cultured hippocampal neurons of CAPS2 KO mice. KO mouse hippocampus also showed decreased number of GABAergic neurons, decreased synaptic vesicle density of inhibitory synapses and decreased frequency and amplitude of mIPSCs. Theta-burst induced long-term potentiation（LTP）at CA3-CA1 synapses was normally induced in KO mice but was reduced in the maintenance phase compared to the WT. The LTP maintenance, however, became indistinguishable between KO and WT in the presence of GABA-A receptor antagonist picrotoxin. In addition, KO mice exhibited augmented autistic and anxiety-like behavior which may be associated with impaired GABAergic transmission. Taken together, our study suggests that CAPS2 is an important regulator of BDNF secretion and thereby influences development of GABAergic inhibitory synapse networks.

3S2-3 New insight in transport and secretion of BDNF：Implications in brain-related diseases Adachi Naoki^1,2，Numakawa Tadahiro^1,3，Nakajima Shingo^1,4，ODAKA HARUKI^1,5，Yoshimura Aya^1,6，Kunugi Hiroshi¹ ¹Dept. of Mental Disorder Research, National Institute of Neuroscience, NCNP，²Department of Bioscience, Kwansei Gakuin University，³Department of Cell Modulation, Institute of Molecular Embryology and Genetics, Kumamoto University，⁴Faculty of Health Science, Hokkaido University，⁵Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University，⁶Division of Laboratory Animals Resources, National Institute of Neuroscience, NCNP Brain-derived neurotrophic factor（BDNF）is an essential factor for survival, differentiation, and functions of neurons in the central nervous system（CNS）. BDNF protein is needed to be transported from the cell body to the secretion sites by secretory vesicles to exert its biological functions. Dysfunctions of the transport have been suggested in several psychiatric and neurodegenerative diseases such as Huntington’s disease. We examined the impact of a stress-related hormone, glucocorticoid, on BDNF-containing vesicle transport in neurite of cortical neurons. Glucocorticoid treatment enhanced the microtubule-based BDNF vesicle transport and the effect was dependent on increased expression of huntingtin protein. We will discuss the importance of transport and secretion steps in BDNF function, focusing on the interaction between BDNF, huntingtin and glucocorticoids.		3S2-4 Biological roles of the BDNF pro-peptide Mizui Toshiyuki¹，Ishikawa Yasuyuki²，Kumanogoh Haruko¹，Kojima Masami¹ ¹Molecular and Cellular Pathology Research Team, Biomedical Research Inst., AIST，²Department of Systems Life Engineering Maebashi Institute of Technology Most growth factors are initially synthesized as precursor proteins and subsequently processed into their mature form by proteolytic cleavage, resulting in simultaneous removal of a pro-peptide. However, as compared to that of mature form, the biological role of the pro-peptide is poorly understood. Here, we investigated the biological role of the pro-peptide of brain-derived neurotrophic factor（BDNF）and first showed that the pro-peptide is expressed and secreted in hippocampal tissues and cultures, respectively. Interestingly, we found that the BDNF pro-peptide directly facilitates hippocampal long-term depression（LTD）, requiring the activation of GluN2B-containing N-methyl-D-aspartate（NMDA）receptors and the pan-neurotrophin receptor p75NTR. The BDNF pro-peptide also enhances NMDA-induced alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor endocytosis, a mechanism crucial for LTD expression. Thus, the BDNF pro-peptide is involved in synaptic plasticity that regulates a mechanism responsible for promoting LTD. The well-known BDNF polymorphism Val66Met affects human memory function. Here, the BDNF pro-peptide with Met mutation completely inhibits hippocampal LTD. These findings demonstrate functional roles for the BDNF pro-peptide and a naturally occurring human BDNF polymorphism in hippocampal synaptic depression.