Details of a Researcher - Yuzaki, Michisuke

Papers - Yuzaki, Michisuke

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Efficient Derivation of Multipotent Neural Stem/Progenitor Cells from Non-Human Primate Embryonic Stem Cells

Shimada Hiroko, Okada Yohei, Ibata Keiji, Ebise Hayao, Ota Shin ichi, Tomioka Ikuo, Nomura Toshihiro, Maeda Takuji, Kohda Kazuhisa, Yuzaki Michisuke, Sasaki Erika, Nakamura Masaya, Okano Hideyuki

PLoS ONE 7 ( 11 ) e49469 2012.11

The common marmoset (Callithrix jacchus) is a small New World primate that has been used as a non-human primate model for various biomedical studies. We previously demonstrated that transplantation of neural stem/progenitor cells (NS/PCs) derived from mouse and human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) promote functional locomotor recovery of mouse spinal cord injury models. However, for the clinical application of such a therapeutic approach, we need to evaluate the efficacy and safety of pluripotent stem cell-derived NS/PCs not only by xenotransplantation, but also allotransplantation using non-human primate models to assess immunological rejection and tumorigenicity. In the present study, we established a culture method to efficiently derive NS/PCs as neurospheres from common marmoset ESCs. Marmoset ESC-derived neurospheres could be passaged repeatedly and showed sequential generation of neurons and astrocytes, similar to that of mouse ESC-derived NS/PCs, and gave rise to functional neurons as indicated by calcium imaging. Although marmoset ESC-derived NS/PCs could not differentiate into oligodendrocytes under default culture conditions, these cells could abundantly generate oligodendrocytes by incorporating additional signals that recapitulate in vivo neural development. Moreover, principal component analysis of microarray data demonstrated that marmoset ESC-derived NS/PCs acquired similar gene expression profiles to those of fetal brain-derived NS/PCs by repeated passaging. Therefore, marmoset ESC-derived NS/PCs may be useful not only for accurate evaluation by allotransplantation of NS/PCs into non-human primate models, but are also applicable to analysis of iPSCs established from transgenic disease model marmosets. © 2012 Shimada et al.

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Presynaptically Released Cbln1 Induces Dynamic Axonal Structural Changes by Interacting with GluD2 during Cerebellar Synapse Formation

Ito-Ishida Aya, Miyazaki Taisuke, Miura Eriko, Matsuda Keiko, Watanabe Masahiko, Yuzaki Michisuke, Okabe Shigeo

Neuron 76 ( 3 ) 549 - 564 2012.11

ISSN 0896-6273

Differentiation of pre- and postsynaptic sites is coordinated by reciprocal interaction across synaptic clefts. At parallel fiber (PF)-Purkinje cell (PC) synapses, dendritic spines are autonomously formed without PF influence. However, little is known about how presynaptic structural changes are induced and how they lead to differentiation of mature synapses. Here, we show that Cbln1 released from PFs induces dynamic structural changes in PFs by a mechanism that depends on postsynaptic glutamate receptor delta2 (GluD2) and presynaptic neurexin (Nrx). Time-lapse imaging in organotypic culture and ultrastructural analyses in vivo revealed that Nrx-Cbln1-GluD2 signaling induces PF protrusions that often formed circular structures and encapsulated PC spines. Such structural changes in PFs were associated with the accumulation of synaptic vesicles and GluD2, leading to formation of mature synapses. Thus, PF protrusions triggered by Nrx-Cbln1-GluD2 signaling may promote bidirectional maturation of PF-PC synapses by a positive feedback mechanism

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Characteristics of Gait Ataxia in δ2 Glutamate Receptor Mutant Mice, ho15J

Takeuchi Eri, Sato Yamato, Miura Eriko, Yamaura Hiroshi, Yuzaki Michisuke, Yanagihara Dai

PLoS ONE 7 ( 10 ) 2012.10

The cerebellum plays a fundamental, but as yet poorly understood, role in the control of locomotion. Recently, mice with gene mutations or knockouts have been used to investigate various aspects of cerebellar function with regard to locomotion. Although many of the mutant mice exhibit severe gait ataxia, kinematic analyses of limb movements have been performed in only a few cases. Here, we investigated locomotion in ho15J mice that have a mutation of the δ2 glutamate receptor. The cerebellum of ho15J mice shows a severe reduction in the number of parallel fiber-Purkinje synapses compared with wild-type mice. Analysis of hindlimb kinematics during treadmill locomotion showed abnormal hindlimb movements characterized by excessive toe elevation during the swing phase, and by severe hyperflexion of the ankles in ho15J mice. The great trochanter heights in ho15J mice were lower than in wild-type mice throughout the step cycle. However, there were no significant differences in various temporal parameters between ho15J and wild-type mice. We suggest that dysfunction of the cerebellar neuronal circuits underlies the observed characteristic kinematic abnormality of hindlimb movements during locomotion of ho15J mice. © 2012 Takeuchi et al.

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Selective and regulated gene expression in murine Purkinje cells by in utero electroporation

Nishiyama Jun, Hayashi Yukari, Nomura Toshihiro, Miura Eriko, Kakegawa Wataru, Yuzaki Michisuke

European Journal of Neuroscience 36 ( 7 ) 2867 - 2876 2012.10

ISSN 0953-816X

Cerebellar Purkinje cells, which convey the only output from the cerebellar cortex, play an essential role in cerebellar functions, such as motor coordination and motor learning. To understand how Purkinje cells develop and function in the mature cerebellum, an efficient method for molecularly perturbing them is needed. Here we demonstrate that Purkinje cell progenitors at embryonic day (E)11.5 could be efficiently and preferentially transfected by spatially directed in utero electroporation (IUE) with an optimized arrangement of electrodes. Electrophysiological analyses indicated that the electroporated Purkinje cells maintained normal membrane properties, synaptic responses and synaptic plasticity at postnatal days 25-28. By combining the L7 promoter and inducible Cre/loxP system with IUE, transgenes were expressed even more specifically in Purkinje cells and in a temporally controlled manner. We also show that three different fluorescent proteins could be simultaneously expressed, and that Bassoon, a large synaptic protein, could be expressed in the electroporated Purkinje cells. Moreover, phenotypes of staggerer mutant mice, which have a deletion in the gene encoding retinoid-related orphan receptor α (RORα1), were recapitulated by electroporating a dominant-negative form of RORα1 into Purkinje cells at E11.5. Together, these results indicate that this new IUE protocol, which allows the selective, effective and temporally regulated expression of multiple foreign genes transfected into Purkinje cell progenitors in vivo, without changing the cells' physiological characteristics, is a powerful tool for elucidating the molecular mechanisms underlying early Purkinje cell developmental events, such as dendritogenesis and migration, and synaptic plasticity in mature Purkinje cells. A new in utero electroporation (IUE) protocol has been developed to deliver genes preferentially into cerebellar Purkinje cells. IUE did not alter the physiological characteristics or normal synaptic plasticity of Purkinje cells. IUE allowed selective, effective, and temporally regulated expression of multiple foreign genes in Purkinje cells in vivo. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

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THE INS and OUTS of GluD2-why and how purkinje cells use the special glutamate receptor

Yuzaki Michisuke

Cerebellum 11 ( 2 ) 438 - 439 2012.06

ISSN 1473-4222

The δ2 glutamate receptor (GluD2) is predominantly expressed in cerebellar Purkinje cells and plays crucial roles in cerebellar functions. Indeed, the number of synapses between parallel fibers (PFs) and Purkinje cells is specifically and severely reduced in GluD2-null cerebellum. In addition, long-term depression (LTD) at PF-Purkinje cell synapses is impaired in these mice. Nevertheless, the mechanism by which GluD2 regulate these two functions-morphological and functional synaptic plasticity at PF synapses-has remained unclear. Recently, we found that Cbln1, a glycoprotein released from granule cells, was bound to the N-terminal domain of GluD2 and regulated formation and maintenance of PF-Purkinje cell synapses. Furthermore, we found that D-Ser released from Bergmann glia bound the ligand-binding domain of GluD2 and mediated LTD in a manner dependent on the C-terminus. These findings indicate how GluD2 is activated and regulates functions at PF-Purkinje cell synapses. A hypothesis about why GluD2 is employed by PF synapses is also discussed. ©Springer Science+Business Media, LLC 2011.

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Cbln1 and the delta2 glutamate receptor - An orphan ligand and an orphan receptor find their partners

Matsuda Keiko, Yuzaki Michisuke

Cerebellum 11 ( 1 ) 78 - 84 2012.03

ISSN 1473-4222

Cerebellin was originally discovered as a Purkinje cell-specific peptide more than two decades ago. Later, its precursor protein precerebellin (Cbln1) was found to be produced in cerebellar granule cells. It has become increasingly clear that although the cerebellin peptide may have certain functions, Cbln1 is an actual signaling molecule that belongs to the C1q family. However, the precise function of Cbln1 has been unresolved. Cbln1 is released from granule cells, and disruption of the cbln1 gene in mice causes a severe reduction in the number of synapses between Purkinje cells and parallel fibers (PFs; axons of granule cells) and results in cerebellar ataxia. The glutamate receptor δ2 (GluD2) is highly expressed on Purkinje cells' dendritic spines which make synapses with PFs. Although GluD2 was identified as a member of the ionotropic glutamate receptors more than 15 years ago, it has been referred to as an orphan receptor because its endogenous ligands are unclear. Interestingly, GluD2-null mice phenocopy cbln1-null mice precisely. Cbln1 and GluD2 have therefore been thought to participate in a common signaling pathway that is required for the formation of PF synapses. We recently established a direct ligand-receptor relationship between Cbln1 and GluD2. The Cbln1-GluD2 complex is located at the cleft of PF-Purkinje cell synapses and bidirectionally regulates both presynaptic and postsynaptic differentiation. © 2010 Springer Science+Business Media, LLC.

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Cerebellar long-term depression requires dephosphorylation of TARP in Purkinje cells

Nomura Toshihiro, Kakegawa Wataru, Matsuda Shinji, Kohda Kazuhisa, Nishiyama Jun, Takahashi Takao, Yuzaki Michisuke

European Journal of Neuroscience 35 ( 3 ) 402 - 410 2012.02

ISSN 0953-816X

Cerebellar long-term depression (LTD) at parallel fiber (PF)-Purkinje cell synapses is thought to play an essential role in certain forms of motor learning. Like hippocampal LTD, cerebellar LTD is mediated by the endocytosis of AMPA (α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate) receptors at postsynaptic sites. However, similar sets of kinases and phosphatases have opposite regulatory effects on hippocampal and cerebellar LTD, although the mechanisms responsible for this difference remain largely unclear. Activity-dependent dephosphorylation of stargazin (an AMPA receptor auxiliary protein) by calcineurin regulates hippocampal LTD, but whether and how stargazin is involved in cerebellar LTD is unknown. In this study, we showed that stargazin is highly phosphorylated at basal states and is dephosphorylated by the application of high KCl plus glutamate (K-glu) or of a metabotropic glutamate receptor agonist, (S)-3,5-dihydroxyphenylglycine (DHPG), both of which chemically induced LTD in cerebellar slices. This chemically induced dephosphorylation of stargazin was specifically blocked by a calcineurin inhibitor. Indeed, inclusion of the calcineurin auto-inhibitory peptide in the patch pipette solution completely inhibited the LTD induced by the conjunctive stimulation of PFs and Purkinje cells. Furthermore, in Purkinje cells expressing stargazin-9D, in which all nine serine residues are mutated to aspartate, neither conjunctive stimulus nor DHPG treatment induced LTD. Finally, immunohistochemical analyses revealed that neither K-glu nor DHPG induced the endocytosis of AMPA receptors in Purkinje cells expressing stargazin-9D. Together, these results indicate that hippocampal and cerebellar LTD share a common pathway, namely dephosphorylation of stargazin by calcineurin. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

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NMDA Receptor-Mediated PIP5K Activation to Produce PI(4,5)P ₂ Is Essential for AMPA Receptor Endocytosis during LTD

Unoki Takamitsu, Matsuda Shinji, Kakegawa Wataru, Van Ngo Thai Bich, Kohda Kazuhisa, Suzuki Atsushi, Funakoshi Yuji, Hasegawa Hiroshi, Yuzaki Michisuke, Kanaho Yasunori

Neuron 73 ( 1 ) 135 - 148 2012.01

ISSN 0896-6273

NMDA receptor activation leads to clathrin-dependent endocytosis of postsynaptic AMPA receptors. Although this process controls long-term depression (LTD) induction in the hippocampus, how it is regulated by neuronal activities is not completely clear. Here, we show that Ca ²⁺ influx through the NMDA receptor activates calcineurin and protein phosphatase 1 to dephosphorylate phosphatidylinositol 4-phosphate 5-kinaseγ661 (PIP5Kγ661), the major phosphatidylinositol 4,5-bisphosphate (PI(4,5)P ₂)-producing enzyme in the brain. Bimolecular fluorescence complementation analysis revealed that the dephosphorylated PIP5Kγ661 became associated with the clathrin adaptor protein complex AP-2 atpostsynapses insitu. NMDA-induced AMPA receptor endocytosis and low-frequency stimulation-induced LTD were completely blocked by inhibiting the association between dephosphorylated PIP5Kγ661 and AP-2 and by overexpression ofa kinase-dead PIP5Kγ661 mutant in hippocampal neurons. Furthermore, knockdown of PIP5Kγ661 inhibited the NMDA-induced AMPA receptor endocytosis. Therefore, NMDA receptor activation controls AMPA receptor endocytosis during hippocampal LTD by regulating PIP5Kγ661 activity at postsynapses. AMPA receptor endocytosis is essential for LTD induction, but it is not clear how this process is controlled. Unoki etal. find that NMDA receptor activation controls AMPA receptor endocytosis during hippocampal LTD by regulating the activity of the enzyme PIP5Kγ661. © 2012 Elsevier Inc.

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A new rapid protocol for eyeblink conditioning to assess cerebellar motor learning

Emi Kyoichi, Kohda Kazuhisa, Kakegawa Wataru, Narumi Sakae, Yuzaki Michisuke

Neurochemical Research 36 ( 7 ) 1314 - 1322 2011.07

ISSN 0364-3190

Mice with spontaneous and induced mutations causing cerebellar phenotypes have provided key insights into how motor-related memories are stored in cerebellar circuits. Delayed eyeblink conditioning is a form of associative motor learning that depends on the cerebellum. However, neurochemical investigation of the underlying mechanisms has been hampered by the long training period (usually several days) required to establish conditioning. Here, we report a new rapid-training protocol that reliably induced delayed eyeblink conditioning within a single day. The associative memory formation depended on the expression of the δ2 glutamate receptor (GluD2) in cerebellar Purkinje cells. It lasted for several weeks, but could be erased by extinction sessions in a single day. In addition, using the rapid protocol, we found that eyeblink conditioning could be induced in juvenile mice at postnatal day 21, and that the Sindbis-virus-mediated expression of GluD2 could rescue the impaired eyeblink conditioning in GluD2-null mice in vivo. © 2011 Springer Science+Business Media, LLC.

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D-Serine regulates cerebellar LTD and motor coordination through the δ glutamate receptor

Kakegawa Wataru, Miyoshi Yurika, Hamase Kenji, Matsuda Shinji, Matsuda Keiko, Kohda Kazuhisa, Emi Kyoichi, Motohashi Junko, Konno Ryuichi, Zaitsu Kiyoshi, Yuzaki Michisuke

Nature Neuroscience 14 ( 5 ) 603 - 613 2011.05

ISSN 1097-6256

D-Serine (D-Ser) is an endogenous co-agonist for NMDA receptors and regulates neurotransmission and synaptic plasticity in the forebrain. D-Ser is also found in the cerebellum during the early postnatal period. Although D-Ser binds to the δ glutamate receptor (GluD2, Grid2) in vitro, its physiological significance has remained unclear. Here we show that D-Ser serves as an endogenous ligand for GluD2 to regulate long-term depression (LTD) at synapses between parallel fibers and Purkinje cells in the immature cerebellum. D-Ser was released mainly from Bergmann glia after the burst stimulation of parallel fibers in immature, but not mature, cerebellum. D-Ser rapidly induced endocytosis of AMPA receptors and mutually occluded LTD in wild-type, but not Grid2-null, Purkinje cells. Moreover, mice expressing mutant GluD2 in which the binding site for D-Ser was disrupted showed impaired LTD and motor dyscoordination during development. These results indicate that glial D-Ser regulates synaptic plasticity and cerebellar functions by interacting with GluD2. © 2011 Nature America, Inc. All rights reserved.

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Cbln family proteins promote synapse formation by regulating distinct neurexin signaling pathways in various brain regions

Matsuda Keiko, Yuzaki Michisuke

European Journal of Neuroscience 33 ( 8 ) 1447 - 1461 2011.04

ISSN 0953-816X

Cbln1 (a.k.a. precerebellin) is a unique bidirectional synaptic organizer that plays an essential role in the formation and maintenance of excitatory synapses between granule cells and Purkinje cells in the mouse cerebellum. Cbln1 secreted from cerebellar granule cells directly induces presynaptic differentiation and indirectly serves as a postsynaptic organizer by binding to its receptor, the δ2 glutamate receptor. However, it remains unclear how Cbln1 binds to the presynaptic sites and interacts with other synaptic organizers. Furthermore, although Cbln1 and its family members Cbln2 and Cbln4 are expressed in brain regions other than the cerebellum, it is unknown whether they regulate synapse formation in these brain regions. In this study, we showed that Cbln1 and Cbln2, but not Cbln4, specifically bound to its presynaptic receptor -α and β isoforms of neurexin carrying the splice site 4 insert [NRXs(S4+)] - and induced synaptogenesis in cerebellar, hippocampal and cortical neurons in vitro. Cbln1 competed with synaptogenesis mediated by neuroligin 1, which lacks the splice sites A and B, but not leucine-rich repeat transmembrane protein 2, possibly by sharing the presynaptic receptor NRXs(S4+). However, unlike neurexins/neuroligins or neurexins/leucine-rich repeat transmembrane proteins, the interaction between NRX1β(S4+) and Cbln1 was insensitive to extracellular Ca²⁺ concentrations. These findings revealed the unique and general roles of Cbln family proteins in mediating the formation and maintenance of synapses not only in the cerebellum but also in various other brain regions. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

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Cbln1 and its family proteins in synapse formation and maintenance

Yuzaki Michisuke

Current Opinion in Neurobiology 21 ( 2 ) 215 - 220 2011.04

ISSN 0959-4388

Cbln1 is a newly identified synaptic organizer belonging to the C1q family. Unlike other synaptic organizers, a deficiency in Cbln1 is sufficient to cause a severe reduction in the number of synapses between cerebellar Purkinje cells and parallel fibers (PFs). Furthermore, Cbln1 can rapidly induce synaptogenesis and is necessary for maintaining normal synapses in the mature cerebellum in vivo. Cbln1 was recently identified as the missing ligand for the orphan glutamate receptor δ2 (GluD2), which is expressed in Purkinje cells. Furthermore, Cbln1 released from PFs binds to neurexin (NRX) expressed on the presynaptic PFs and GluD2 at the postsynaptic site. The NRX/Cbln1/GluD2 tripartite complex is resistant to low extracellular Ca²⁺ levels and serves as a unique bidirectional synaptic organizer. © 2011 Elsevier Ltd.

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Serotonin Mediates Cross-Modal Reorganization of Cortical Circuits

Jitsuki Susumu, Takemoto Kiwamu, Kawasaki Taisuke, Tada Hirobumi, Takahashi Aoi, Becamel Carine, Sano Akane, Yuzaki Michisuke, Zukin R. Suzanne, Ziff Edward B., Kessels Helmut W., Takahashi Takuya

Neuron 69 ( 4 ) 780 - 792 2011.02

ISSN 0896-6273

Loss of one type of sensory input can cause improved functionality of other sensory systems. Whereas this form of plasticity, cross-modal plasticity, is well established, the molecular and cellular mechanisms underlying it are still unclear. Here, we show that visual deprivation (VD) increases extracellular serotonin in the juvenile rat barrel cortex. This increase in serotonin levels facilitates synaptic strengthening at layer 4 to layer 2/3 synapses within the barrel cortex. Upon VD, whisker experience leads to trafficking of the AMPA-type glutamate receptors (AMPARs) into these synapses through the activation of ERK and increased phosphorylation of AMPAR subunit GluR1 at the juvenile age when natural whisker experience no longer induces synaptic GluR1 delivery. VD thereby leads to sharpening of the functional whisker-barrel map at layer 2/3. Thus, sensory deprivation of one modality leads to serotonin release in remaining modalities, facilitates GluR1-dependent synaptic strengthening, and refines cortical organization. © 2011 Elsevier Inc.

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Snapin snaps into the dynein complex for late endosome-lysosome trafficking and autophagy

Yuzaki Michisuke

Neuron 68 ( 1 ) 4 - 6 2010.10

ISSN 0896-6273

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Therapeutic potential of appropriately evaluated safe-induced pluripotent stem cells for spinal cord injury

Tsuji Osahiko, Miura Kyoko, Okada Yohei, Fujiyoshi Kanehiro, Mukaino Masahiko, Nagoshi Narihito, Kitamura Kazuya, Kumagai Gentaro, Nishino Makoto, Tomisato Shuta, Higashi Hisanobu, Nagai Toshihiro, Katoh Hiroyuki, Kohda Kazuhisa, Matsuzaki Yumi, Yuzaki Michisuke, Ikeda Eiji, Toyama Yoshiaki, Nakamura Masaya, Yamanaka Shinya, Okano Hideyuki

Proceedings of the National Academy of Sciences of the United States of America 107 ( 28 ) 12704 - 12709 2010.07

ISSN 0027-8424

Various types of induced pluripotent stem (iPS) cells have been established by different methods, and each type exhibits different biological properties. Before iPS cell-based clinical applications can be initiated, detailed evaluations of the cells, including their differentiation potentials and tumorigenic activities in different contexts, should be investigated to establish their safety and effectiveness for cell transplantation therapies. Here we show the directed neural differentiation of murine iPS cells and examine their therapeutic potential in amouse spinal cord injury (SCI)model. "Safe" iPS-derived neurospheres, which had been pre-evaluated as nontumorigenic by their transplantation into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse brain, produced electrophysiologically functional neurons, astrocytes, and oligodendrocytes in vitro. Furthermore, when the safe iPS-derived neurospheres were transplanted into the spinal cord 9 d after contusive injury, they differentiated into all three neural lineages without forming teratomas or other tumors. They also participated in remyelination and induced the axonal regrowth of host 5HT⁺ serotonergic fibers, promoting locomotor function recovery. However, the transplantation of iPSderived neurospheres pre-evaluated as "unsafe" showed robust teratoma formation and sudden locomotor functional loss after functional recovery in the SCI model. These findings suggest that preevaluated safe iPS clone-derived neural stem/progenitor cells may be a promising cell source for transplantation therapy for SCI.

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Recent excitements about excitatory synapses

Scheiffele Peter, Yuzaki Michizuke

European Journal of Neuroscience 32 ( 2 ) 179 - 180 2010.07

ISSN 0953-816X

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Synapse formation and maintenance by C1q family proteins

Yuzaki Michisuke

European Journal of Neuroscience 32 ( 2 ) 191 - 197 2010.07

ISSN 0953-816X

Several C1q family members, especially the Cbln and C1q-like subfamilies, are highly and predominantly expressed in the central nervous system. Cbln1, a member of the Cbln subfamily, plays two unique roles at parallel ber (PF)-Purkinje cell synapses in the cerebellum: the formation and stabilization of synaptic contact, and the control of functional synaptic plasticity by regulating the postsynaptic endocytotic pathway. The delta2 glutamate receptor (GluD2), which is predominantly expressed in Purkinje cells, plays similar critical roles in the cerebellum. In addition, viral expression of GluD2 or the application of recombinant Cbln1 induces PF- Purkinje cell synaptogenesis in vitro and in vivo. Antigen-unmasking methods were necessary to reveal the immunoreactivities for endogenous Cbln1 and GluD2 at the synaptic junction of PF synapses. We propose that Cbln1 and GluD2 are located at the synaptic cleft, where various proteins undergo intricate molecular interactions with each other, and serve as a bidirectional synaptic organizer. © The Author (2010). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

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A response to Dr. Yue's commentary

Yuzaki Michisuke, Nishiyama Jun

Autophagy 6 ( 4 ) 573 2010.05

ISSN 1554-8627

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Excitotoxicity and autophagy

Nishiyama Jun, Yuzaki Michisuke

Autophagy 6 ( 4 ) 568 - 570 2010.05

ISSN 1554-8627

The role of autophagy in excitotoxic cell death caused by excessive activation of glutamate receptors has been a contentious issue. Lurcher (Lc) mutant mice, in which a mutant glutamate receptor causes continuous ion flow and kills cerebellar Purkinje cells, have been cited as a model of cell death resulting from autophagy, or "autophagic cell death," in vivo. Here, we reinvestigated Lc-mediated cell death in heterologous cells and cultured neurons as well as in Lc mice in vivo. We show that Lc-mediated cell death is likely not caused by autophagy, but rather by necrosis with autophagic features. Constitutive ion flux per se causes reduction of intracellular ATP levels, which activates the autophagic pathways. Therefore, activation of autophagy might have a homeostatic protective role to maintain intracellular ATP in the Lc model of excitotoxicity. © 2010 Landes Bioscience.

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Cbln1 is a ligand for an orphan glutamate receptor δ2, a bidirectional synapse organizer

Matsuda Keiko, Miura Eriko, Miyazaki Taisuke, Kakegawa Wataru, Emi Kyoichi, Narumi Sakae, Fukazawa Yugo, Ito-lshida Aya, Kondo Tetsuro, Shigemoto Ryuichi, Watanabe Masahiko, Yuzaki Michisuke

Science 328 ( 5976 ) 363 - 368 2010.04

ISSN 0036-8075

Cbln1, secreted from cerebellar granule cells, and the orphan glutamate receptor 52 (GluD2), expressed by Purkinje cells, are essential for synapse integrity between these neurons in adult mice. Nevertheless, no endogenous binding partners for these molecules have been identified. We found that Cblnl binds directly to the N-terminal domain of GluD2. GluD2 expression by postsynaptic cells, combined with exogenously applied Cbln1, was necessary and sufficient to induce new synapses in vitro and in the adult cerebellum in vivo. Further, beads coated with recombinant Cbln1 directly induced presynaptic differentiation and indirectly caused clustering of postsynaptic molecules via GluD2. These results indicate that the Cbln1-GluD2 complex is a unique synapse organizer that acts bidirectionally on both pre- and postsynaptic components.

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