Details of a Researcher - Yuzaki, Michisuke

Papers - Yuzaki, Michisuke

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A novel non-canonical Notch signaling regulates expression of synaptic vesicle proteins in excitatory neurons.

Hayashi Y, Nishimune H, Hozumi K, Saga Y, Harada A, Yuzaki M, Iwatsubo T, Kopan R, Tomita T

Scientific reports 6 23969 2016.04

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A Computational Model for the AMPA Receptor Phosphorylation Master Switch Regulating Cerebellar Long-Term Depression.

Gallimore AR, Aricescu AR, Yuzaki M, Calinescu R

PLoS computational biology 12 ( 1 ) e1004664 2016.01

ISSN 1553-734X

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Controlling the Regional Identity of hPSC-Derived Neurons to Uncover Neuronal Subtype Specificity of Neurological Disease Phenotypes

Imaizumi, Kent, Sone, Takefumi, Ibata, Keiji, Fujimori, Koki, Yuzaki, Michisuke, Akamatsu, Wado, Okano, Hideyuki

STEM CELL REPORTS 5 ( 6 ) 1010 - 1022 2015.12

Research paper (scientific journal), ISSN 2213-6711

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Rorα regulates multiple aspects of dendrite development in cerebellar purkinje cells in vivo

Takeo Yukari H., Kakegawa Wataru, Miura Eriko, Yuzaki Michisuke

Journal of Neuroscience 35 ( 36 ) 12518 - 12534 2015.09

ISSN 0270-6474

The establishment of cell-type-specific dendritic arbors is fundamental for proper neural circuit formation. Here, using temporal- and cell-specific knock-down, knock-out, and overexpression approaches, we show that multiple aspects of the dendritic organization of cerebellar Purkinje cells (PCs) are controlled by a single transcriptional factor, retinoic acid-related orphan receptor-alpha (RORα), a gene defective in staggerer mutant mice. As reported earlier, RORawas required for regression of primitive dendrites before postnatal day 4 (P4). RORα was also necessary for PCs to form a single Purkinje layer from P0 to P4. The knock-down of RORafrom P4 impaired the elimination of perisomatic dendrites and maturation of single stem dendrites in PCs at P8. Filopodia and spines were also absent in these PCs. The knock-down of RORα from P8 impaired the formation and maintenance of terminal dendritic branches of PCs at P14. Finally, even after dendrite formation was completed at P21,RORα was required for PCs to maintain dendritic complexity and functional synapses, but their mature innervation pattern by single climbing fibers was unaffected. Interestingly, overexpression of RORain PCs at various developmental stages did not facilitate dendrite development, but had specific detrimental effects on PCs. Because RORα deficiency during development is closely related to the severity of spinocerebellar ataxia type 1, delineating the specific roles of RORain PCs in vivo at different time windows during development and throughout adulthood would facilitate our understanding of the pathogenesis of cerebellar disorders.

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Anterograde C1ql1 signaling is required in order to determine and maintain a single-winner climbing fiber in the mouse cerebellum

Kakegawa Wataru, Mitakidis Nikolaos, Miura Eriko, Abe Manabu, Matsuda Keiko, Takeo Yukari H., Kohda Kazuhisa, Motohashi Junko, Takahashi Akiyo, Nagao Soichi, Muramatsu Shin ichi, Watanabe Masahiko, Sakimura Kenji, Aricescu A. Radu, Yuzaki Michisuke

Neuron 85 ( 2 ) 316 - 330 2015.01

ISSN 0896-6273

Neuronal networks are dynamically modified by selective synapse pruning during development and adulthood. However, how certain connections win the competition with others and are subsequently maintained is not fully understood. Here, we show that C1ql1, a member of the C1q family of proteins, is provided by climbing fibers (CFs) and serves as acrucial anterograde signal to determine and maintain the single-winner CF in the mouse cerebellum throughout development and adulthood. C1ql1 specifically binds to the brain-specific angiogenesis inhibitor 3 (Bai3), which is a member of the cell-adhesionG-protein-coupled receptor family and expressed on postsynaptic Purkinje cells. C1ql1-Bai3 signaling is required for motor learning but not for gross motor performance or coordination. Because related family members of C1ql1 and Bai3 are expressed in various brain regions, the mechanism described here likely applies to synapse formation, maintenance, and function in multiple neuronal circuits essential for important brain functions.

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Optogenetic control of the function of the Golgi apparatus in neurons

Endo, Junnosuke, Takeo, Yukari, Matsuda, Shinji, Yuzaki, Michisuke

GLYCOBIOLOGY 24 ( 11 ) 1201 - 1201 2014.11

Research paper (scientific journal), ISSN 0959-6658

Axonal localization of Ca²⁺-dependent activator protein for secretion 2 is critical for subcellular locality of brain-derived neurotrophic factor and neurotrophin-3 release affecting proper development of postnatal mouse cerebellum

Sadakata Tetsushi, Kakegawa Wataru, Shinoda Yo, Hosono Mayu, Katoh-Semba Ritsuko, Sekine Yukiko, Sato Yumi, Saruta Chihiro, Ishizaki Yasuki, Yuzaki Michisuke, Kojima Masami, Furuichi Teiichi

PLoS ONE 9 ( 6 ) e99524 2014.06

Ca²⁺-dependent activator protein for secretion 2 (CAPS2) is a protein that is essential for enhanced release of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) from cerebellar granule cells. We previously identified dex3, a rare alternative splice variant of CAPS2, which is overrepresented in patients with autism and is missing an exon 3 critical for axonal localization. We recently reported that a mouse model CAPS2 ^Δx3/Δex3 expressing dex3 showed autistic-like behavioral phenotypes including impaired social interaction and cognition and increased anxiety in an unfamiliar environment. Here, we verified impairment in axonal, but not somato-dendritic, localization of dex3 protein in cerebellar granule cells and demonstrated cellular and physiological phenotypes in postnatal cerebellum of CAPS2^Δx3/Δx3 mice. Interestingly, both BDNF and NT-3 were markedly reduced in axons of cerebellar granule cells, resulting in a significant decrease in their release. As a result, dex3 mice showed developmental deficits in dendritic arborization of Purkinje cells, vermian lobulation and fissurization, and granule cell precursor proliferation. Paired-pulse facilitation at parallel fiber- Purkinje cell synapses was also impaired. Together, our results indicate that CAPS2 plays an important role in subcellular locality (axonal vs. somato-dendritic) of enhanced BDNF and NT-3 release, which is indispensable for proper development of postnatal cerebellum. © 2014 Sadakata et al.

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The role of Cbln1 on Purkinje cell synapse formation

Ito-Ishida Aya, Okabe Shigeo, Yuzaki Michisuke

Neuroscience Research 83 64 - 68 2014.06

ISSN 0168-0102

Cbln1 is a glycoprotein which belongs to the C1q family. In the cerebellum, Cbln1 is produced and secreted from granule cells and works as a strong synapse organizer between Purkinje cells and parallel fibers, the axons of the granule cells. In this update article, we will describe the molecular mechanisms by which Cbln1 induces synapse formation and will review our findings on the axonal structural changes which occur specifically during this process. We will also describe our recent finding that Cbln1 has a suppressive role in inhibitory synapse formation between Purkinje cells and molecular layer interneurons. Our results have revealed that Cbln1 plays an essential role to establish parallel fiber-Purkinje cell synapses and to regulate balance between excitatory and inhibitory input on Purkinje cells.

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Reprogramming non-human primate somatic cells into functional neuronal cells by defined factors

Zhou Zhi, Kohda Kazuhisa, Ibata Keiji, Kohyama Jun, Akamatsu Wado, Yuzaki Michisuke, Okano Hirotaka James, Sasaki Erika, Okano Hideyuki

Molecular Brain 7 ( 1 ) 24 2014.04

Background: The common marmoset (Callithrix jacchus) is a New World primate sharing many similarities with humans. Recently developed technology for generating transgenic marmosets has opened new avenues for faithful recapitulation of human diseases, which could not be achieved in rodent models. However, the longer lifespan of common marmosets compared with rodents may result in an extended period for in vivo analysis of common marmoset disease models. Therefore, establishing rapid and efficient techniques for obtaining neuronal cells from transgenic individuals that enable in vitro analysis of molecular mechanisms underlying diseases are required. Recently, several groups have reported on methods, termed direct reprogramming, to generate neuronal cells by defined factors from somatic cells of various kinds of species, including mouse and human. The aim of the present study was to determine whether direct reprogramming technology was applicable to common marmosets. Results: Common marmoset induced neuronal (cjiN) cells with neuronal morphology were generated from common marmoset embryonic skin fibroblasts (cjF) by overexpressing the neuronal transcription factors: ASCL1, BRN2, MYT1L and NEUROD1. Reverse transcription-polymerase chain reaction of cjiN cells showed upregulation of neuronal genes highly related to neuronal differentiation and function. The presence of neuronal marker proteins was also confirmed by immunocytochemistry. Electrical field stimulation to cjiN cells increased the intracellular calcium level, which was reversibly blocked by the voltage-gated sodium channel blocker, tetrodotoxin, indicating that these cells were functional. The neuronal function of these cells was further confirmed by electrophysiological analyses showing that action potentials could be elicited by membrane depolarization in current-clamp mode while both fast-activating and inactivating sodium currents and outward currents were observed in voltage-clamp mode. The 5-bromodeoxyuridine (BrdU) incorporation assay showed that cjiN cells were directly converted from cjFs without passing a proliferative state. Conclusions: Functional common marmoset neuronal cells can be obtained directly from embryonic fibroblasts by overexpressing four neuronal transcription factors under in vitro conditions. Overall, direct conversion technology on marmoset somatic cells provides the opportunity to analyze and screen phenotypes of genetically-modified common marmosets. © 2014 Zhou et al.; licensee BioMed Central Ltd.

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Rab8a and Rab8b are essential for several apical transport pathways but insufficient for ciliogenesis

Sato Takashi, Iwano Tomohiko, Kunii Masataka, Matsuda Shinji, Mizuguchi Rumiko, Jung Yongwook, Hagiwara Haruo, Yoshihara Yoshihiro, Yuzaki Michisuke, Harada Reiko, Harada Akihiro

Journal of Cell Science 127 ( 2 ) 422 - 431 2014.01

ISSN 0021-9533

The small GTP-binding protein Rab8 is known to play an essential role in intracellular transport and cilia formation. We have previously demonstrated that Rab8a is required for localising apical markers in various organisms. Rab8a has a closely related isoform, Rab8b. To determine whether Rab8b can compensate for Rab8a, we generated Rab8b-knockout mice. Although the Rab8b-knockout mice did not display an overt phenotype, Rab8a and Rab8b double-knockout mice exhibited mislocalisation of apical markers and died earlier than Rab8a-knockout mice. The apical markers accumulated in three intracellular patterns in the double-knockout mice. However, the localisation of basolateral and/or dendritic markers of the double-knockout mice seemed normal. The morphology and the length of various primary and/or motile cilia, and the frequency of ciliated cells appeared to be identical in control and double-knockout mice. However, an additional knockdown of Rab10 in double-knockout cells greatly reduced the percentage of ciliated cells. Our results highlight the compensatory effect of Rab8a and Rab8b in apical transport, and the complexity of the apical transport process. In addition, neither Rab8a nor Rab8b are required for basolateral and/or dendritic transport. However, simultaneous loss of Rab8a and Rab8b has little effect on ciliogenesis, whereas additional loss of Rab10 greatly affects ciliogenesis. © 2014. Published by The Company of Biologists Ltd.

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Neural ECM and synaptogenesis

Heikkinen Anne, Pihlajaniemi Taina, Faissner Andreas, Yuzaki Michisuke

Progress in Brain Research 214 29 - 51 2014

ISSN 0079-6123

Chemical synapses allow neurons to perform complex computations and regulate other systems of the body. At a chemical synapse, pre- and postsynaptic sites are separated by a small space (the synaptic cleft) and surrounded by astrocytes. The basement membrane (BM), a sheetlike, specialized extracellular matrix (ECM), is found ubiquitously in the PNS. It has become clear that the ECMs not only play a structural role but also serve as barriers and filters in the PNS and CNS. Moreover, proteoglycans and tenascin family proteins in the ECM regulate synapse formation and synaptic plasticity. Although CNS synapses lack the BMs, recent results indicate that the BM-associated collagens are also present in the CNS synaptic cleft and affect synaptogenesis in both the CNS and the PNS. The C1q domain-containing family proteins are important components of the CNS synaptic cleft in regulating synapse formation, maintenance, and the pruning process. The ECM is regarded as a crucial component of the tetrapartite synapse, consisting of pre- and postsynaptic neurons, astrocyte, and ECM.

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Cbln1 downregulates the formation and function of inhibitory synapses in mouse cerebellar Purkinje cells

Ito-Ishida Aya, Kakegawa Wataru, Kohda Kazuhisa, Miura Eriko, Okabe Shigeo, Yuzaki Michisuke

European Journal of Neuroscience 39 ( 8 ) 1268 - 1280 2014

ISSN 0953-816X

The formation of excitatory and inhibitory synapses must be tightly coordinated to establish functional neuronal circuitry during development. In the cerebellum, the formation of excitatory synapses between parallel fibers and Purkinje cells is strongly induced by Cbln1, which is released from parallel fibers and binds to the postsynaptic δ2 glutamate receptor (GluD2). However, Cbln1's role, if any, in inhibitory synapse formation has been unknown. Here, we show that Cbln1 downregulates the formation and function of inhibitory synapses between Purkinje cells and interneurons. Immunohistochemical analyses with an anti-vesicular GABA transporter antibody revealed an increased density of interneuron-Purkinje cell synapses in the cbln1-null cerebellum. Whole-cell patch-clamp recordings from Purkinje cells showed that both the amplitude and frequency of miniature inhibitory postsynaptic currents were increased in cbln1-null cerebellar slices. A 3-h incubation with recombinant Cbln1 reversed the increased amplitude of inhibitory currents in Purkinje cells in acutely prepared cbln1-null slices. Furthermore, an 8-day incubation with recombinant Cbln1 reversed the increased interneuron-Purkinje cell synapse density in cultured cbln1-null slices. In contrast, recombinant Cbln1 did not affect cerebellar slices from mice lacking both Cbln1 and GluD2. Finally, we found that tyrosine phosphorylation was upregulated in the cbln1-null cerebellum, and acute inhibition of Src-family kinases suppressed the increased inhibitory postsynaptic currents in cbln1-null Purkinje cells. These findings indicate that Cbln1-GluD2 signaling inhibits the number and function of inhibitory synapses, and shifts the excitatory-inhibitory balance towards excitation in Purkinje cells. Cbln1's effect on inhibitory synaptic transmission is probably mediated by a tyrosine kinase pathway. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

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Enriched expression of GluD1 in higher brain regions and its involvement in parallel fiber-interneuron synapse formation in the cerebellum

Konno Kohtarou, Matsuda Keiko, Nakamoto Chihiro, Uchigashima Motokazu, Miyazaki Taisuke, Yamasaki Miwako, Sakimura Kenji, Yuzaki Michisuke, Watanabe Masahiko

Journal of Neuroscience 34 ( 22 ) 7412 - 7424 2014

ISSN 0270-6474

Of the two members of the δ subfamily of ionotropic glutamate receptors, GluD2 is exclusively expressed at parallel fiber-Purkinje cell (PF-PC) synapses in the cerebellum and regulates their structural and functional connectivity. However, little is known to date regarding cellular and synaptic expression of GluD1 and its role in synaptic circuit formation. In the present study, we investigated this issue by producing specific and sensitive histochemical probes for GluD1 and analyzing cerebellar synaptic circuits in GluD1-knock-out mice. GluD1 was widely expressed in the adult mouse brain, with high levels in higher brain regions, including the cerebral cortex, striatum, limbic regions (hippocampus, nucleus accumbens, lateral septum, bed nucleus stria terminalis, lateral habenula, and central nucleus of the amygdala), and cerebellar cortex. In the cerebellar cortex, GluD1 mRNA was expressed at the highest level in molecular layer interneurons and its immunoreactivity was concentrated at PF synapses on interneuron somata. In GluD1-knock-out mice, the density of PF synapses on interneuron somata was significantly reduced and the size and number of interneurons were significantly diminished. Therefore, GluD1 is common to GluD2 in expression at PF synapses, but distinct from GluD2 in neuronal expression in the cerebellar cortex; that is, GluD1 in interneurons and GluD2 in PCs. Furthermore, GluD1 regulates the connectivity of PF-interneuron synapses and promotes the differentiation and/or survival of molecular layer interneurons. These results suggest that GluD1 works in concert with GluD2 for the construction of cerebellar synaptic wiring through distinct neuronal and synaptic expressions and also their shared synapse-connecting function. © 2014 the authors.

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Reevaluation of the role of parallel fiber synapses in delay eyeblink conditioning in mice using Cbln1 as a tool

Emi Kyoichi, Kakegawa Wataru, Miura Eriko, Ito-Ishida Aya, Kohda Kazuhisa, Yuzaki Michisuke

Frontiers in Neural Circuits 7 ( NOV ) 180 2013.11

ISSN 1662-5110

The delay eyeblink conditioning (EBC) is a cerebellum-dependent type of associative motor learning. However, the exact roles played by the various cerebellar synapses, as well as the underlying molecular mechanisms, remain to be determined. It is also unclear whether long-term potentiation (LTP) or long-term depression (LTD) at parallel fiber (PF)-Purkinje cell (PC) synapses is involved in EBC. In this study, to clarify the role of PF synapses in the delay EBC, we used mice in which a gene encoding Cbln1 was disrupted (cbln1^-/- mice), which display severe reduction of PF-PC synapses. We showed that delay EBC was impaired in cbln1^-/- mice. Although PF-LTD was impaired, PF-LTP was normally induced in cbln1^-/- mice. A single recombinant Cbln1 injection to the cerebellar cortex in vivo completely, though transiently, restored the morphology and function of PF-PC synapses and delay EBC in cbln1^-/- mice. Interestingly, the cbln1^-/- mice retained the memory for at least 30 days, after the Cbln1 injection's effect on PF synapses had abated. Furthermore, delay EBC memory could be extinguished even after the Cbln1 injection's effect were lost.These results indicate that intact PF-PC synapses and PF-LTD, not PF-LTP are necessary to acquire delay EBC in mice. In contrast, extracerebellar structures or remaining PF-PC synapses in cbln1^-/- mice may be sufficient for the expression, maintenance, and extinction of its memory trace. © 2013 Emi, Kakegawa, Miura, Ito-Ishida, Kohda and Yuzaki.

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Cerebellar LTD vs. motor learning-Lessons learned from studying GluD2

Yuzaki Michisuke

Neural Networks 47 36 - 41 2013.11

ISSN 0893-6080

Synaptic plasticity, such as long-term potentiation and long-term depression (LTD), is believed to underlie learning and memory processes in vivo. The cerebellum is an ideal brain region to obtain definitive proof for this hypothesis. The current belief is that the acquisition of motor learning is stored by LTD at the parallel fiber (PF)-Purkinje cell synapse in the cerebellar cortex. Recently, however, several lines of mutant mice that display normal motor learning in the absence of cerebellar LTD have been reported. A similar dichotomy between synaptic plasticity at the circuitry level and learning at the behavioral level has also been reported in the hippocampus. One possible explanation for this dichotomy is that compensatory pathways at the molecular and circuitry levels play an important role in mice that have been genetically modified for their entire lives. Mice that are genetically modified to be deficient in or to express mutant versions of the δ2 glutamate receptor (GluD2) serve as an interesting model due to the predominant expression of GluD2 at PF-Purkinje cell synapses. Furthermore, two major functions of GluD2-PF synapse formation and LTD induction-can be mechanistically dissociated so that the role of LTD in motor learning can be investigated in the absence of morphological abnormalities caused by altered synapse formation. Therefore, genetic manipulations of GluD2 will help to clarify the relationship between LTD and motor learning in the cerebellum. © 2012 Elsevier Ltd.

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Deletions in GRID2 lead to a recessive syndrome of cerebellar ataxia and tonic upgaze in humans

Hills L. Benjamin, Masri Amira, Konno Kotaro, Kakegawa Wataru, Lam Anh Thu N, Lim-Melia Elizabeth, Chandy Nandini, Hill R. Sean, Partlow Jennifer N., Al-Saffar Muna, Nasir Ramzi, Stoler Joan M., Barkovich A. James, Watanabe Masahiko, Yuzaki Michisuke, Mochida Ganeshwaran H.

Neurology 81 ( 16 ) 1378 - 1386 2013.10

ISSN 0028-3878

Objective: To identify the genetic cause of a syndrome causing cerebellar ataxia and eye movement abnormalities. Methods: Weidentified 2 families with cerebellar ataxia, eyemovement abnormalities, and global developmental delay. We performed genetic analyses including single nucleotide polymorphism genotyping, linkage analysis, array comparative genomic hybridization, quantitative PCR, and Sanger sequencing. We obtained eye movement recordings of mutant mice deficient for the ortholog of the identified candidate gene, and performed immunohistochemistry using human and mouse brain specimens. Results: All affected individuals had ataxia, eye movement abnormalities, most notably tonic upgaze, and delayed speech and cognitive development. Homozygosity mapping identified the disease locus on chromosome 4q. Within this region, a homozygous deletion of GRID2 exon 4 in the index family and compound heterozygous deletions involving GRID2 exon 2 in the second family were identified. Grid2-deficient mice showed larger spontaneous and random eye movements compared to wild-type mice. In developing mouse and human cerebella, GRID2 localized to the Purkinje cell dendritic spines. Brain MRI in 2 affected children showed progressive cerebellar atrophy, which was more severe than that of Grid2-deficient mice. Conclusions: Biallelic deletions of GRID2 lead to a syndrome of cerebellar ataxia and tonic upgaze in humans. The phenotypic resemblance and similarity in protein expression pattern between humans and mice suggest a conserved role for GRID2 in the synapse organization between parallel fibers and Purkinje cells. However, the progressive and severe cerebellar atrophy seen in the affected individuals could indicate an evolutionarily unique role for GRID2 in the human cerebellum. © 2013 American Academy of Neurology.

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The δ2 glutamate receptor gates long-term depression by coordinating interactions between two AMPA receptor phosphorylation sites

Kohda Kazuhisa, Kakegawa Wataru, Matsuda Shinji, Yamamoto Tadashi, Hirano Hisashi, Yuzaki Michisuke

Proceedings of the National Academy of Sciences of the United States of America 110 ( 10 ) E948 - 57 2013.03

ISSN 0027-8424

Long-term depression (LTD) commonly affects learning andmemoryin various brain regions. Although cerebellar LTD absolutely requires the δ2 glutamate receptor (GluD2) that is expressed in Purkinje cells, LTDin other brain regions does not;why andhowcerebellar LTD is regulated by GluD2 remains unelucidated. Here, we show that the activitydependent phosphorylation of serine 880 (S880) in GluA2 AMPA receptor subunit, which is an essential step for AMPA receptor endocytosis during LTD induction, was impaired in GluD2-null cerebellum. In contrast, the basal phosphorylation levels of tyrosine 876 (Y876) in GluA2were increased in GluD2-null cerebellum. An in vitro phosphorylation assay revealed that Y876 phosphorylation inhibited subsequent S880 phosphorylation. Conversely, Y876 dephosphorylation was sufficient to restore S880 phosphorylation and LTD induction in GluD2-null Purkinje cells. Furthermore, megakaryocyte protein tyrosine phosphatase (PTPMEG), which binds to the C terminus of GluD2, directly dephosphorylated Y876. These data indicate that GluD2 gates LTD by coordinating interactions between the two phosphorylation sites of the GluA2.

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Unlocking the secrets of the δ2 glutamate receptor

Kohda Kazuhisa, Kakegawa Wataru, Yuzaki Michisuke

Communicative and Integrative Biology 6 ( 6 ) e26466 2013

ISSN 1942-0889

Long-term changes in synaptic transmission in the central nervous system, such as long-term potentiation and long-term depression (LTD), are believed to underlie learning and memory in vivo. Despite intensive research, the precise molecular mechanisms underlying these phenomena have remained unclear. LTD is most commonly caused by the endocytosis of postsynaptic AMPA-type glutamate receptors, triggered by activity- induced serine phosphorylation of the GluA2 subunit. Interestingly, cerebellar LTD, which occurs at synapses between parallel fibers (PFs; axons of granule cells) and Purkinje cells, is unique in requiring an additional type of glutamate receptor, the δ2 receptor (GluD2). Cbln1 was recently identified as a GluD2 ligand that regulates PF synapse formation and maintenance. However, how GluD2 induces downstream signaling in Purkinje cells to regulate LTD induction is unknown. We here present evidence that GluD2 reduces the tyrosine phosphorylation level of the GluA2 subunit via PTPMEG, a protein tyrosine phosphatase that binds to GluD2's C-terminus. We also found that the serine phosphorylation of GluA2, a crucial step for AMPA-receptor endocytosis, requires prior tyrosine dephosphorylation. Thus, GluD2 may serve as a gatekeeper for LTD induction by coordinating interactions between GluA2's 2 phosphorylation sites. © 2013 Landes Bioscience.

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CAPS1 deficiency perturbs dense-core vesicle trafficking and golgi structure and reduces presynaptic release probability in the mouse brain

Sadakata Tetsushi, Kakegawa Wataru, Shinoda Yo, Hosono Mayu, Katoh-Semba Ritsuko, Sekine Yukiko, Sato Yumi, Tanaka Mika, Iwasato Takuji, Itohara Shigeyoshi, Furuyama Kenichiro, Kawaguchi Yoshiya, Ishizaki Yasuki, Yuzaki Michisuke, Furuichi Teiichi

Journal of Neuroscience 33 ( 44 ) 17326 - 17334 2013

ISSN 0270-6474

Ca ²⁺ -dependent activator protein for secretion 1 (CAPS1) plays a regulatory role in the dense-core vesicle (DCV) exocytosis pathway, but its functions at the cellular and synaptic levels in the brain are essentially unknown because of neonatal death soon after birth in Caps1 knock-out mice. To clarify the functions of the protein in the brain, we generated two conditional knock-out (cKO) mouse lines: 1) one lacking Caps1 in the forebrain; and 2) the other lacking Caps1 in the cerebellum. Both cKO mouse lines were born normally and grew to adulthood, although they showed subcellular and synaptic abnormalities. Forebrain-specific Caps1 cKO mice showed reduced immunoreactivity for the DCV marker secretogranin II (SgII) and the trans-Golgi network (TGN) marker syntaxin 6, a reduced number of presynaptic DCVs, and dilated trans-Golgi cisternae in the CA3 region. Cerebellum-specific Caps1 cKO mice had decreased immunoreactivity for SgII and brain-derived neurotrophic factor (BDNF) along the climbing fibers. At climbing fiber-Purkinje cell synapses, the number of DCVs was markedly lower and the number of synaptic vesicles was also reduced. Correspondingly, the mean amplitude of EPSCs was decreased, whereas paired-pulse depression was significantly increased. Our results suggest that loss of CAPS1 disrupts the TGN-DCV pathway, which possibly impairs synaptic transmission by reducing the presynaptic release probability. © 2013 the authors.

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Stargazin regulates AMPA receptor trafficking through adaptor protein complexes during long-term depression

Matsuda Shinji, Kakegawa Wataru, Budisantoso Timotheus, Nomura Toshihiro, Kohda Kazuhisa, Yuzaki Michisuke

Nature Communications 4 2759 2013

Long-term depression (LTD) underlies learning and memory in various brain regions. Although postsynaptic AMPA receptor trafficking mediates LTD, its underlying molecular mechanisms remain largely unclear. Here we show that stargazin, a transmembrane AMPA receptor regulatory protein, forms a ternary complex with adaptor proteins AP-2 and AP-3A in hippocampal neurons, depending on its phosphorylation state. Inhibiting the stargazin-AP-2 interaction disrupts NMDA-induced AMPA receptor endocytosis, and inhibiting that of stargazin-AP-3A abrogates the late endosomal/lysosomal trafficking of AMPA receptors, thereby upregulating receptor recycling to the cell surface. Similarly, stargazin's interaction with AP-2 or AP-3A is necessary for low-frequency stimulus-evoked LTD in CA1 hippocampal neurons. Thus, stargazin has a crucial role in NMDA-dependent LTD by regulating two trafficking pathways of AMPA receptors - transport from the cell surface to early endosomes and from early endosomes to late endosomes/lysosomes - through its sequential binding to AP-2 and AP-3A. © 2013 Macmillan Publishers Limited. All rights reserved.

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