Hideki Matsui

Okayama University, Okayama, Okayama, Japan

Are you Hideki Matsui?

Claim your profile

Publications (177)628.2 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Glioblastoma, a malignant brain tumor with poor disease outcomes, is managed in modern medicine by multimodality therapy. Boron neutron capture therapy (BNCT) is an encouraging treatment under clinical investigation. In malignant cells, BNCT consists of two major factors: neutron radiation and boron uptake. To increase boron uptake in cells, we created a mercapto-closo-undecahydrododecaborate ([B12HnSH](2-)2Na(+), BSH) fused with a short arginine peptide (1R, 2R, 3R) and checked cellular uptake in vitro and in vivo. In a mouse brain tumor model, only BSH with at least three arginine domains could penetrate cell membranes of glioma cells in vitro and in vivo. Furthermore, to monitor the pharmacokinetic properties of these agents in vivo, we fused BSH and BSH-3R with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA); DOTA is a metal chelating agent for labeling positron emission tomography (PET) probe with (64)Cu. We administered BSH-DOTA-(64)Cu and BSH-3R-DOTA-(64)Cu to the tumor model through a mouse tail vein and determined the drugs' pharmacokinetics by PET imaging. BSH-3R showed a high uptake in the tumor area on PET imaging. We concluded that BSH-3R is the ideal boron compound for clinical use during BNCT and that in developing this compound for clinical use, the BSH-3R PET probe is essential for pharmacokinetic imaging. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Biomaterials 07/2015; 56. DOI:10.1016/j.biomaterials.2015.03.061 · 8.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cortactin contributes to growth cone morphogenesis by forming with dynamin, ring-shaped complexes that mechanically bundle and stabilize F-actin. However, the regulatory mechanism of cortactin action is poorly understood. Immunofluorescence microscopy revealed that protein kinase C (PKC) α colocalizes with cortactin at growth cone filopodia in SH-SY5Y neuroblastoma cells. PKC-activation by phorbol 12-myristate 13-acetate causes cortactin phosphorylation, filopodial retraction and F-actin-bundle loss. Moreover, PKCα directly phosphorylates cortactin in vitro at S135/T145/S172, mitigating both cortactin's actin-binding and actin-crosslinking capacity, whereas cellular expression of a phosphorylation-mimetic cortactin mutant hinders filopodial formation with a significant decrease of actin bundles. Our results indicate that PKC-mediated cortactin phosphorylation might be implicated in maintenance of growth cone. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Biology of the Cell 06/2015; 107(9). DOI:10.1111/boc.201500032 · 3.51 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transfer RNAs (tRNAs) contain a wide variety of posttranscriptional modifications that are important for accurate decoding. Mammalian mitochondrial tRNAs (mt-tRNAs) are modified by nuclear-encoded tRNA-modifying enzymes; however, the physiological roles of these modifications remain largely unknown. In this study, we report that Cdk5 regulatory subunit-associated protein 1 (Cdk5rap1) is responsible for 2-methylthio (ms(2)) modifications of mammalian mt-tRNAs for Ser(UCN), Phe, Tyr, and Trp codons. Deficiency in ms(2) modification markedly impaired mitochondrial protein synthesis, which resulted in respiratory defects in Cdk5rap1 knockout (KO) mice. The KO mice were highly susceptive to stress-induced mitochondrial remodeling and exhibited accelerated myopathy and cardiac dysfunction under stressed conditions. Furthermore, we demonstrate that the ms(2) modifications of mt-tRNAs were sensitive to oxidative stress and were reduced in patients with mitochondrial disease. These findings highlight the fundamental role of ms(2) modifications of mt-tRNAs in mitochondrial protein synthesis and their pathological consequences in mitochondrial disease. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell Metabolism 03/2015; 21(3):428-42. DOI:10.1016/j.cmet.2015.01.019 · 17.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A hybrid comprising an autophagy-inducing peptide (AIP) and a cell-penetrating peptide (CPP) connected via heterodimeric leucine zippers was generated and delivered into cells. The hybrid successfully induced autophagy without significant cell death, while the same AIP directly connected to a CPP caused both autophagy and significant cell death.
    Chemical Communications 11/2014; 51(2). DOI:10.1039/C4CC07459A · 6.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective Developmental disorders including cognitive deficit, hyperkinetic disorder, and autistic behaviors are frequently comorbid in epileptic patients with SCN1A mutations. However, the mechanisms underlying these developmental disorders are poorly understood and treatments are currently unavailable. Using a rodent model with an Scn1a mutation, we aimed to elucidate the pathophysiologic basis and potential therapeutic treatments for developmental disorders stemming from Scn1a mutations.Methods We conducted behavioral analyses on rats with the N1417H-Scn1a mutation. With high-performance liquid chromatography, we measured dopamine and its metabolites in the frontal cortex, striatum, nucleus accumbens, and midbrain. Methylphenidate was administered intraperitoneally to examine its effects on developmental disorder–like behaviors and hyperthermia-induced seizures.ResultsBehavioral studies revealed that Scn1a-mutant rats had repetitive behavior, hyperactivity, anxiety-like behavior, spatial learning impairments, and motor imbalance. Dopamine levels in the striatum and nucleus accumbens in Scn1a-mutant rats were significantly lower than those in wild-type rats. In Scn1a-mutant rats, methylphenidate, by increasing dopamine levels in the synaptic cleft, improved hyperactivity, anxiety-like behavior, and spatial learning impairments. Surprisingly, methylphenidate also strongly suppressed hyperthermia-induced seizures.SignificanceDysfunction of the mesolimbic dopamine reward pathway may contribute to the hyperactivity and learning impairments in Scn1a-mutant rats. Methylphenidate was effective for treating hyperactivity, learning impairments, and hyperthermia-induced seizures. We propose that methylphenidate treatment may ameliorate not only developmental disorders but also epileptic seizures in patients with SCN1A mutations.
    Epilepsia 08/2014; 55(10). DOI:10.1111/epi.12750 · 4.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Topical therapy is the most favored form of treatment for whitening against hyper-pigmentation and sunburn because it lends itself to self-administration, patient compliance and an absence of systemic adverse effects. However, high-molecular-weight, hydrophilic chemicals are difficult to use as transdermal delivery drugs and the use of topical drugs has been highly limited. There are now many potent tyrosinase inhibitors, for example, sulfite or kojic acid, but the efficacy of their skin transduction remains a big problem. Furthermore, melanogenesis inhibitors from natural sources have great potential, as they are considered to be safe and largely free from adverse side effects. We applied 11-arginine (11R), a cell-membrane-permeable peptide, as a transdermal delivery system with a skin delivery enhancer, pyrenbutyrate. We performed intracellular screening for melanogenesis inhibitors with 11R fused with several kinds of tyrosinase inhibitory peptides from natural sources. Of 28 tyrosinase peptides, 13 melanin synthesis inhibitory peptides were selected. Peptide No. 10 found in gliadin protein, a wheat component, most strongly inhibited melanin production. This No. 10 peptide, of only 8 amino acids, fused to 11R showed no cytotoxicity and inhibited melanin synthesis as determined through melanin content measured using an absorption spectrometer and observation with a transmission electron microscope. Next, we transduced this 11R-No. 10 into skin with an 11R transdermal delivery system after previous treatment with pyrenbutyrate and performed daily repetitive topical application for two weeks against a UV-induced sun-tanning guinea pig model. We observed a whitening effect in a model skin sample by Masson-Fontana staining and the 11R-No. 10 peptide-applied area showed significant melanogenesis inhibition. These results show that 11R using a transdermal drug delivery system with melanogenesis inhibitory peptide is a very safe and promising method for applications from cosmetics to the pharmaceutical industry.
    Biomaterials 03/2014; 35(15). DOI:10.1016/j.biomaterials.2014.01.052 · 8.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: New anti-cancer therapy with boron neutron capture therapy (BNCT) is based on the nuclear reaction of boron-10 with neutron irradiation. The median survival of BNCT patients with glioblastoma was almost twice as long as those receiving standard therapy in a Japanese BNCT clinical trial. In this clinical trial, two boron compounds, BPA (boronophenylalanine) and BSH (sodium borocaptate), were used for BNCT. BPA is taken up into cells through amino acid transporters that are expressed highly in almost all malignant cells, but BSH cannot pass through the cell membrane and remains outside the cell. We simulated the energy transfer against the nucleus at different locations of boron from outside the cell to the nuclear region with neutron irradiation and concluded that there was a marked difference between inside and outside the cell in boron localization. To overcome this disadvantage of BSH in BNCT, we used a cell-penetrating peptide system for transduction of BSH. CPP (cell-membrane penetrating peptide) is very common peptide domains that transduce many physiologically active substances into cells in vitro and in vivo. BSH-fused CPPs can penetrate the cell membrane and localize inside a cell. To increase the boron ratio in one BSH-peptide molecule, 8BSH fused to 11R with a dendritic lysine structure was synthesized and administrated to malignant glioma cells and a brain tumor mouse model. 8BSH-11R localized at the cell nucleus and showed a very high boron value in ICP results. With neutron irradiation, the 8BSH-11R administrated group showed a significant cancer killing effect compared to the 100 times higher concentration of BSH-administrated group. We concluded that BSH-fused CPPs were one of the most improved and potential boron compounds in the next-stage BNCT trial and 8BSH-11R may be applied in the clinical setting.
    Biomaterials 01/2014; 35(10). DOI:10.1016/j.biomaterials.2013.12.055 · 8.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Microenvironmental conditions such as hypoxia potentiate the local invasion of malignant tumors including glioblastomas by modulating signal transduction and protein modification, yet the mechanism by which hypoxia controls cytoskeletal dynamics to promote the local invasion is not well defined. Here, we show that cyclin G2 plays pivotal roles in the cytoskeletal dynamics in hypoxia-driven invasion by glioblastoma cells. Cyclin G2 is a hypoxia-induced and cytoskeleton-associated protein and is required for glioblastoma expansion. Mechanistically, cyclin G2 recruits cortactin to the juxtamembrane through its SH3 domain-binding motif and consequently promotes the restricted tyrosine phosphorylation of cortactin in concert with src. Moreover, cyclin G2 interacts with filamentous actin to facilitate the formation of membrane ruffles. In primary glioblastoma, cyclin G2 is abundantly expressed in severely hypoxic regions such as pseudopalisades, which consist of actively migrating glioma cells. Furthermore, we show the effectiveness of dasatinib against hypoxia-driven, cyclin G2-involved invasion in vitro and in vivo. Our findings elucidate the mechanism of cytoskeletal regulation by which severe hypoxia promotes the local invasion and may provide a therapeutic target in glioblastoma.
    Neoplasia (New York, N.Y.) 11/2013; 15(11):1272-81. DOI:10.1593/neo.131440 · 4.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A combination of molecular-targeted cancer imaging and therapy is an emerging strategy to improve cancer diagnosis and minimize the side effects of conventional treatments. Here, we generated a recombinant protein, EC1-GLuc-p53C, by fusing EC1 peptide, an artificial ligand of ErbB2, with Gaussia luciferase (GLuc) and a p53-activating peptide, p53C. EC1-GLuc-p53C was expressed and purified from E. coli BL21. In vitro experiments showed that EC1-GLuc-p53c was stable in luminescent activity and selectively targeted ErbB2-overexpressing BT474 cells for bioluminescence imaging. Moreover, the internalized EC1-GLuc-p53C in BT474 cells exerted its function to reactivate p53 and significantly inhibited cellular proliferation. In tumor-bearing mice, the ErbB2-targeted bioluminescence imaging and therapeutic effect of EC1-GLuc-p53C were also observed specifically in BT474 tumors but not in MCF7 tumors, which does not overexpress ErbB2. Thus, the present study demonstrates EC1-GLuc-p53C to be an effective theranostic reagent targeting ErbB2 for bioluminescence imaging and cancer therapy.
    PLoS ONE 09/2013; 8(9):e75288. DOI:10.1371/journal.pone.0075288 · 3.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dynamin GTPase, a key molecule in endocytosis, mechanically severs the invaginated membrane upon GTP hydrolysis. Dynamin functions also in regulating actin cytoskeleton, but the mechanisms are yet to be defined. Here we show that dynamin 1, a neuronal isoform of dynamin, and cortactin form ring complexes, which twine around F-actin bundles and stabilize them. By negative-staining EM, dynamin 1-cortactin complexes appeared as "open" or "closed" rings depending on guanine nucleotide conditions. By pyrene actin assembly assay, dynamin 1 stimulated actin assembly in mouse brain cytosol. In vitro incubation of F-actin with both dynamin 1 and cortactin led to the formation of long and thick actin bundles, on which dynamin 1 and cortactin were periodically colocalized in puncta. A depolymerization assay revealed that dynamin 1 and cortactin increased the stability of actin bundles, most prominently in the presence of GTP. In rat cortical neurons and human neuroblastoma cell line, SH-SY5Y, both dynamin 1 and cortactin localized on actin filaments and the bundles at growth cone filopodia as revealed by immunoelectron microscopy. In SH-SY5Y cell, acute inhibition of dynamin 1 by application of dynamin inhibitor led to growth cone collapse. Cortactin knockdown also reduced growth cone filopodia. Together, our results strongly suggest that dynamin 1 and cortactin ring complex mechanically stabilizes F-actin bundles in growth cone filopodia. Thus, the GTPase-dependent mechanochemical enzyme property of dynamin is commonly used both in endocytosis and regulation of F-actin bundles by a dynamin 1-cortactin complex.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 03/2013; 33(10):4514-4526. DOI:10.1523/JNEUROSCI.2762-12.2013 · 6.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to assess the anticonvulsant effect of carbon dioxide (CO(2)) on Scn1a mutation-related febrile seizures. We examined physiological changes in the blood gas levels after the induction of hyperthermia-induced seizures (HISs), which were associated with the Scn1a missense mutation. We determined the efficacy of inhalation of 5% or 10% CO(2) to treat HISs. HISs were evoked in Scn1a mutant and wild-type (WT) rats by hot water baths. To determine the anticonvulsant effect of CO(2) inhalation, rats were placed in a chamber filled with air or mixed gas containing 5% CO(2) or 10% CO(2) for 3min, immediately after the induction of HISs. We also analyzed the blood gas levels at the end of inhalation of CO(2). Hot water bathing induced a significant reduction in the partial pressure of CO(2) (pCO(2)) and respiratory alkalosis in the WT and Scn1a mutant rats. HISs were evoked in 100% of the Scn1a mutant rats within 5min, but in none of the WT rats. The Scn1a mutant rats demonstrated a higher HISs susceptibility associated with respiratory alkalosis than the WT rats. Inhalation of 10% CO(2) shortened the seizure duration from 62.6±12.1s to 15.5±1.0s. Blood gas analysis after the inhalation of 10% CO(2) demonstrated an elevated pCO(2) level and respiratory acidosis. Inhalation of 10% CO(2) demonstrated a potent and fast-acting anticonvulsant effect against HISs.
    Epilepsy research 01/2013; 105(1-2). DOI:10.1016/j.eplepsyres.2013.01.003 · 2.02 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dravet syndrome is an intractable epileptic syndrome beginning in the first year of life. De novo mutations of SCN1A, which encode the Na(v)1.1 neuronal voltage-gated sodium channel, are considered the major cause of Dravet syndrome. In this study, we investigated genetic modifiers of this syndrome. We performed a mutational analysis of all coding exons of CACNA1A in 48 subjects with Dravet syndrome. To assess the effects of CACNA1A variants on the epileptic phenotypes of Dravet syndrome, we compared clinical features in two genotype groups: 1) subjects harboring SCN1A mutations but no CACNA1A variants (n=20) and 2) subjects with SCN1A mutations plus CACNA1A variants (n=20). CACNA1A variants detected in patients were studied using heterologous expression of recombinant human Ca(v)2.1 in HEK 293 cells and whole-cell patch-clamp recording. Nine CACNA1A variants, including six novel ones, were detected in 21 of 48 subjects (43.8%). Based on the incidence of variants in healthy controls, most of the variants seemed to be common polymorphisms. However, the subjects harboring SCN1A mutations and CACNA1A variants had absence seizures more frequently than patients with only SCN1A mutations (8/20 vs. 0/20, p=0.002). Moreover, the former group of subjects exhibited earlier onset of seizures and more frequent prolonged seizures before one year of age, compared to the latter group of subjects. The electrophysiological properties of four of the five novel Ca(v)2.1 variants exhibited biophysical changes consistent with gain-of-function. We conclude that CACNA1A variants in some Dravet syndrome persons may modify the epileptic phenotypes.
    Neurobiology of Disease 10/2012; 50(1). DOI:10.1016/j.nbd.2012.10.016 · 5.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We review here that oxytocin (OT) is released into blood and within distinct brain regions in response to stressful and social stimuli, and has been shown to have an antidepressant-like effect in animal studies. Clinical reports suggest OT to be a promising drug for psychiatric diseases such as depression, anxiety disorders, schizophrenia, and autism. OT may also have therapeutic potential in the treatment of major depressive disorders, even though OT administered into blood does not readily cross the blood–brain barrier. Physiological functions such as sexual activity and mating induce the release of OT in the central nervous system. A drug for the treatment of sexual dysfunction, sildenafil, enhances the electrically evoked release of OT from the posterior pituitary. This drug has antidepressant-like effects through activation of an OT signaling pathway. These results suggest that sildenafil may have promise as a potential antidepressant.
    The Journal of Physiological Sciences 09/2012; 62(6). DOI:10.1007/s12576-012-0232-9 · 1.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Topical therapy is the most favored form of treatment for whitening against hyperpigmentation and sunburn because it lends itself to self-administration, patient compliance, and absence of systemic adverse effects. However, transdermal delivery of hydrophilic chemicals is difficult. The main purpose of this study is to develop a delivering system of hydrophilic drugs and proteins across the skin. Hydroquinone (HQ), a well-known tyrosinase inhibitor and antimelanogenesis compound, and enhanced green fluorescent protein (EGFP) were fused with eleven poly-arginine (11R). Both HQ-11R and EGFP-11R were efficiently delivered in B16 cells, a mouse melanoma cell line. HQ-11R was as effective as HQ alone at inhibiting melanin synthesis in B16 cells. EGFP-11R was efficiently delivered into cells of the epidermis with 4-(1-pyrenyl)-butyric acid (PB), a counteranion bearing an aromatic hydrophobic moiety, in vivo, but EGFP alone or EGFP-11R without PB was not. Finally, topical application of HQ-11R with PB significantly inhibited UV irradiation-induced pigmentation in guinea pigs compared with HQ alone. These results suggest that topical therapy using poly-arginine in combination with PB is useful for the delivery of hydrophilic drugs and proteins by the transdermal route.
    Biomaterials 06/2012; 33(27):6468-75. DOI:10.1016/j.biomaterials.2012.04.056 · 8.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Protein transduction with cell-penetrating peptides such as poly-arginine and HIV TAT peptides is widely used to deliver proteins, peptides, siRNA and biologically active compounds. It has been thought that poly-arginine peptides transduce proteins in a manner dependent on the number of arginine residues and oligo-peptides such as three arginines (3R) are ineffective. Here we showed that 3R-fused proteins were effectively delivered and functioned in cells co-treated with pyrenebutyrate, a counteranion bearing an aromatic hydrophobic moiety. Little 3R was transduced in glioma cells without pyrenebutyrate whereas the oligo-arginine was effectively delivered with pyrenebutyrate. Enhanced green fluorescence protein (eGFP) fused with 3R was effectively delivered into various kinds of cells including primary cultured cells and suspended cells in the presence of pyrenebutyrate. p53 fused with 3R (3R-p53) was delivered into glioma cells without pyrenebutyrate but could not be translocated into the nucleus. In contrast, 3R-p53 was observed in nuclei of glioma cells when co-applied with pyrenebutyrate. Although 3R-p53 was delivered less effectively than 11R-p53 with pyrenebutyrate, its transcriptional activity was higher than that of 11R-p53. Moreover, a single administration of 3R-p53 with pyrenebutyrate significantly inhibited the growth of cancer cells. These results suggest protein transduction using an oligo-arginine (3R) with pyrenebutyrate to be a good tool for the delivery of functional transcription factors and a promising method of treating cancer.
    Biomaterials 03/2012; 33(18):4665-72. DOI:10.1016/j.biomaterials.2012.02.049 · 8.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The neuropeptide oxytocin (OT) has been shown to exert multiple functions in both males and females, and to play a key role in the regulation of emotionality in the central nervous system (CNS). OT has an anxiolytic effect in the CNS of rodents and humans. However, the molecular mechanisms of this effect are unclear. Here we show that OT induced the expression of regulator of G-protein signaling 2 (RGS2), a regulatory factor for anxiety, in the central amygdala (CeA) of female mice. Bath application of OT increased RGS2 levels in slices of the amygdala of virgin mice. RGS2 levels in the CeA were higher in lactating mice than in virgin mice. In contrast, RGS2 levels in mice that had given birth did not increase when the pups were removed. Acute restraint stress for 4h induced RGS2 expression within the CeA, and local administration of an OT receptor antagonist inhibited this expression. Behavioral experiments revealed that transient restraint stress had an anxiolytic effect in wild-type females, and RGS2 levels in the CeA correlated with the anxiolytic behavior. By contrast, in the OT receptor-deficient mice, restraint stress neither increased RGS2 levels in the CeA nor had an anxiolytic effect. These results suggest that OT displays an anxiolytic effect through the induction of RGS2 expression in the CNS.
    Brain research 03/2012; 1453:26-33. DOI:10.1016/j.brainres.2012.03.012 · 2.84 Impact Factor
  • Atsushi Fujimura · Kazuhito Tomizawa · Hideki Matsui
    Okayama Igakkai Zasshi (Journal of Okayama Medical Association) 01/2012; 124(2):101-104. DOI:10.4044/joma.124.101
  • Keiichiro Hayashi · Iori Ohmori · Hideki Matsui
    Okayama Igakkai Zasshi (Journal of Okayama Medical Association) 01/2012; 124(2):115-117. DOI:10.4044/joma.124.115
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although synaptotagmin I, which is a calcium (Ca(2+))-binding synaptic vesicle protein, may trigger soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated synaptic vesicle exocytosis, the mechanisms underlying the interaction between these proteins remain controversial, especially with respect to the identity of the protein(s) in the SNARE complex that bind(s) to synaptotagmin and whether Ca(2+) is required for their highly effective binding. To address these questions, native proteins were solubilized, immunoprecipitated from rat brain extracts, and analyzed by immunoblotting. SNARE complexes comprising syntaxin 1, 25-kDa synaptosomal-associated protein (SNAP-25), and synaptobrevin 2 were coprecipitated with synaptotagmin I in the presence of ethylene glycol tetraacetic acid. The amount of coprecipitated proteins was significantly unaltered by the addition of Ca(2+) to the brain extract. To identify the component of the SNARE complex that bound to synaptotagmin, SNARE was coexpressed with synaptotagmin in HEK293 cells and immunoprecipitated. Syntaxin, but not SNAP-25 and synaptobrevin, bound to synaptotagmin in a Ca(2+)-independent manner, and the binding was abolished in the presence of 1M NaCl. Synaptotagmin contains 2 Ca(2+)-binding domains (C(2)A, C(2)B). Mutating the positively charged lysine residues in the putative effector-binding region of the C(2)B domain, which are critical for transmitter release, markedly inhibited synaptotagmin-syntaxin binding, while similar mutations in the C(2)A domain had no effect on binding. Synaptotagmin-syntaxin binding was reduced by mutating multiple negatively charged glutamate residues in the amino-terminal half of the syntaxin SNARE motif. These results indicate that synaptotagmin I binds to syntaxin 1 electrostatically through its C(2)B domain effector region in a Ca(2+)-independent fashion, providing biochemical evidence that synaptotagmin I binds SNARE complexes before Ca(2+) influx into presynaptic nerve terminals.
    Molecular and Cellular Neuroscience 01/2012; 49(1):1-8. DOI:10.1016/j.mcn.2011.09.007 · 3.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Oxytocin (OT) levels in plasma increase during sexual response and are significantly lower in patients with depression. A drug for the treatment of sexual dysfunction, sildenafil, enhances the electrically evoked release of OT from the posterior pituitary. In this study, we showed that sildenafil had an antidepressant-like effect through activation of an OT signaling pathway. Application of sildenafil reduced depression-related behavior in male mice. The antidepressant-like effect was blocked by an OT receptor (OTR) antagonist and was absent in OTR knockout (KO) mice. Sildenafil increased the phosphorylation of cAMP response element-binding protein (CREB) in the hippocampus. The OTR antagonist inhibited sildenafil-induced CREB phosphorylation and sildenafil had no effect on CREB phosphorylation in OTR KO mice. These results suggest sildenafil to have an antidepressant-like effect through the activation of OT signaling and to be a promising drug for the treatment of depression.
    Neuroscience 11/2011; 200:13-8. DOI:10.1016/j.neuroscience.2011.11.001 · 3.36 Impact Factor

Publication Stats

4k Citations
628.20 Total Impact Points


  • 1995–2015
    • Okayama University
      • • Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences
      • • Department of Oral Physiology
      Okayama, Okayama, Japan
  • 2003
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 1997–1998
    • Kagawa University
      • Department of Physiology
      Takamatu, Kagawa, Japan
  • 1985
    • The University of Calgary
      Calgary, Alberta, Canada