研究者詳細 - 寳田　剛志

Glutamate transporters as drug targets 査読

Eiichi Hinoi, Takeshi Takarada, Yuriko Tsuchihashi, Yukio Yoneda

Current Drug Targets: CNS and Neurological Disorders 4 ( 2 ) 211 - 220 2005年4月

記述言語：英語出版者・発行元：2

The L-glutamate (Glu) has been hypothesized as an excitatory amino acid neurotransmitter in the mammalian central nervous system after successful cloning and identification of a number of genes encoding signaling machineries required for the neurocrine at synapses in the brain. These include excitatory amino acid transporters (EAATs) for signal termination and vesicular Glu transporters (VGLUTs) for signal output through exocytotic release, in addition to Glu receptors (GluRs) for signal input. These Glu signaling molecules not only play key roles in mechanisms associated with synaptic plasticity such as learning and memory, but also participate in the etiology and pathology of different neuropsychiatric disorders and neuronal cell death seen in various neurodegenerative diseases. Of the aforementioned Glu signaling molecules, EAATs are essential for the termination of signal transmission mediated by Glu as well as for the prevention of neurotoxicity mediated by this endogenous excitotoxin, while VGLUTs are crucial for the storage of Glu in synaptic vesicles to suffice for the definition of a glutamatergic phenotype. Many early desperate efforts were devoted to the search and development of novel compounds with a therapeutic window toward GluRs, while relatively little attention was paid to either EAATs or VGLUTs in this aspect. In this review, therefore, we will summarize the classification and functionality of EAATs and VGLUTs with a focus on their possibilities as potential therapeutic targets for different neurodegenerative and neuropsychiatric disorders related to malfunction of Glu signaling in human beings. © 2005 Bentham Science Publishers Ltd.

DOI： 10.2174/1568007053544093

Scopus

Accumulation of [H-3]glutamate in cultured rat calvarial osteoblasts 査読

T Takarada, E Hinoi, S Fujimori, Y Tsuchihashi, T Ueshima, H Taniura, Y Yoneda

BIOCHEMICAL PHARMACOLOGY 68 ( 1 ) 177 - 184 2004年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

In the present study, we have attempted to demonstrate constitutive and functional expression in bone of particular glutamate transporters (GluTs) required for signal termination in glutamatergic signaling process. Reverse transcription polymerase chain reaction revealed constitutive expression of mRNA for the neuronal GluT subtype excitatory amino acid carrier-1, in addition to glial subtypes such as glutamate aspartate transporter and glutamate transporter-1, in rat calvarial osteoblasts cultured for 7-21 days in vitro (DIV). The accumulation of [H-3]glutamate (Glu) occurred in a temperature- and sodium-dependent manner with pharmacological profiles similar to those for brain GluTs in osteoblasts cultured for 7 DIV, while three different agonists at ionotropic Glu receptors significantly inhibited the accumulation of [H-3]Glu in osteoblasts. Although [H-3]Glu accumulation consisted of a single component with a K-m value of 26.0 +/- 15.8 muM and a V-max value of 960 +/- 122 nmol/(min mg protein), respectively, in osteoblasts cultured for 7 DIV, in vitro maturation led to a significant decrease in V-max value to 290 +/- 33 nmol/(min mg protein) without significantly affecting K-m values on 21 DIV. These results suggest that Glu could be incorporated into intracellular locations through glial and/or neuronal GluT subtypes expressed in cultured rat calvarial osteoblasts. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bcp.2004.03.020

Possible expression of functional glutamate transporters in the rat testis 査読

T Takarada, E Hinoi, VJ Balcar, H Taniura, Y Yoneda

JOURNAL OF ENDOCRINOLOGY 181 ( 2 ) 233 - 244 2004年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC ENDOCRINOLOGY

Neither expression nor functionality is clear in peripheral tissues with the molecular machineries required for excitatory neurotransmitter signaling by L-glutamate (Glu) in the central nervous system, while a recent study has shown that several Glu receptors are functionally expressed in the rat testis. This fact prompted us to explore the possible functional expression in the rat testis of the Glu transporters usually responsible for the regulation of extracellular Gin concentrations in the brain. RT-PCR revealed the expression, in the rat testis, of mRNA for five different subtypes of Glu transporters, in addition to that for particular subtypes of ionotropic and metabotropic Glu receptors. Glutamate transporter-1 (GLT-1) was different in the brain from that in the testis in terms of molecular sizes on Northern and Western blot analyses. Iu situ hybridization aswell as immunohistochemical analysis showed localized expression of glutamate aspartate transporter at interstitial spaces and GLT-1 at elongated spermatids in the rat testis respectively. The expression of mRNA was localized for excitatory amino acid transporter-5 at the basal compartment of the seminiferous tubule in the rat testis. [H-3]Glu was accumulated in testicular crude mitochondrial fractions in a temperature- and sodium-dependent saturable manner with pharmacological profiles similar to those shown in brain crude mitochondrial fractions. These results suggested that particular subtypes of central Glu transporters for the regulation of extracellular Glu concentrations in the rat testis could be constitutively and functionally expressed.

Modulation by static magnetism of neuronal activity

Glutamate signaling system in bone 査読

E Hinoi, T Takarada, Y Yoneda

JOURNAL OF PHARMACOLOGICAL SCIENCES 94 ( 3 ) 215 - 220 2004年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE PHARMACOLOGICAL SOC

L-Glutamate (Glu) has been thought to be an excitatory amino acid neurotransmitter in the mammalian central nervous system (CNS). The hypothesis is supported by successful cloning of a number of genes encoding different signaling molecules, such as Glu receptors for signal input, Glu transporters for signal termination, and vesicular Glu transporters for signal output through exocytotic release. Limited information is available in the literature with regard to an extracellular transmitter role of Glu in peripheral neuronal and non-neuronal tissues, whereas recent molecular biological analyses including ours give rise to a novel function for Glu as an autocrine and/or paracrine factor in bone comprised of osteoblasts, osteoclasts, and osteocytes, in addition to other peripheral tissues including pancreas, adrenal, and pituitary glands. Emerging evidence suggests that Glu could play a dual role in mechanisms underlying maintenance of cellular homeostasis as an excitatory neurotransmitter in the CNS and as an extracellular signal mediator in peripheral autocrine and/or paracrine tissues. In this review, therefore, we summarized the possible signaling by Glu as an extracellular signal mediator in mechanisms underlying maintenance of cellular homeostasis with a focus on bone tissues.

DOI： 10.1254/jphs.94.215

Glutamate signaling in peripheral tissues 査読

E Hinoi, T Takarada, T Ueshima, Y Tsuchihashi, Y Yoneda

EUROPEAN JOURNAL OF BIOCHEMISTRY 271 ( 1 ) 1 - 13 2004年1月

記述言語：英語出版者・発行元：BLACKWELL PUBLISHING LTD

The hypothesis that L-glutamate (Glu) is an excitatory amino acid neurotransmitter in the mammalian central nervous system is now gaining more support after the successful cloning of a number of genes coding for the signaling machinery required for this neurocrine at synapses in the brain. These include Glu receptors (signal detection), Glu transporters (signal termination) and vesicular Glu transporters (signal output through exocytotic release). Relatively little attention has been paid to the functional expression of these molecules required for Glu signaling in peripheral neuronal and non-neuronal tissues; however, recent molecular biological analyses show a novel function for Glu as an extracellular signal mediator in the autocrine and/or paracrine system. Emerging evidence suggests that Glu could play a dual role in mechanisms underlying the maintenance of cellular homeostasis - as an excitatory neurotransmitter in the central neurocrine system and an extracellular signal mediator in peripheral autocrine and/or paracrine tissues. In this review, the possible Glu signaling methods are outlined in specific peripheral tissues including bone, testis, pancreas, and the adrenal, pituitary and pineal glands.

DOI： 10.1046/j.1432-1033.2003.03907.x

Hirai, T., Goto, Y., Takarada, T., Taniura, H., Yoneda, Y.

Biomedical Reviews 15 ( 1 ) 2004年

Uptake of [H-3]L-serine in rat brain synaptosomal fractions 査読

T Takarada, VJ Balcar, K Baba, A Takamoto, GB Acosta, K Takano, Y Yoneda

BRAIN RESEARCH 983 ( 1-2 ) 36 - 47 2003年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Accumulation of [H-3]L-serine in crude synaptosomal fractions freshly prepared from rat brain has been found to be temperature-sensitive and to consist of both Na+-dependent and Na+-independent components. The accumulation of [H-3]L-serine measured at submicromolar concentrations had a distinct substrate selectivity, different from the uptake of [H-3]L-proline, [H-3]L-glutamate and [H-3]GABA. It was fully inhibited by L-glutamine, L-asparagine, L-cysteine, L-alanine, L-leucine, L-isoleucine, L-tyrosine, L-phenylalanine, L-threonine and by the synthetic marker for the large neutral amino acid transport systems 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid, but not influenced by P-alanine, taurine, glycine nor was it inhibited by the marker for the A system, L-2-methylamino isobutyric acid. D-Serine at 1 mM concentration produced no significant inhibition of the accumulation of 10 nM [H-3]L-serine. We conclude that L-serine uptake observed in the present study is mediated by at least two distinct transport systems: a Na+-dependent one of lower affinity (K-m in mM range) and a Na+-independent system of higher affinity (K(m)approximate to20-100 muM). Characteristics of [(3) H]L-serine accumulation displayed at low substrate concentrations suggest that it was mediated neither by the typical 'A', nor by the 'large neutral', amino acid transport systems but predominantly by transporters belonging to the recently identified LAT (L-amino acid transporter) family. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0006-8993(03)03024-5