研究者詳細 - 表　弘志

論文 - 表　弘志

分割表示 84 件中 21 - 40 件目／全件表示 >>

Involvement of the Leaf-Specific Multidrug and Toxic Compound Extrusion (MATE) Transporter Nt-JAT2 in Vacuolar Sequestration of Nicotine in Nicotiana tabacum 査読

Nobukazu Shitan, Shota Minami, Masahiko Morita, Minaho Hayashida, Shingo Ito, Kojiro Takanashi, Hiroshi Omote, Yoshinori Moriyama, Akifumi Sugiyama, Alain Goossens, Masataka Moriyasu, Kazufumi Yazaki

PLOS ONE 9 ( 9 ) e108789 2014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：PUBLIC LIBRARY SCIENCE

Alkaloids play a key role in higher plant defense against pathogens and herbivores. Following its biosynthesis in root tissues, nicotine, the major alkaloid of Nicotiana species, is translocated via xylem transport toward the accumulation sites, leaf vacuoles. Our transcriptome analysis of methyl jasmonate-treated tobacco BY-2 cells identified several multidrug and toxic compound extrusion (MATE) transporter genes. In this study, we characterized a MATE gene, Nicotiana tabacum jasmonate-inducible alkaloid transporter 2 (Nt-JAT2), which encodes a protein that has 32% amino acid identity with Nt-JAT1. Nt-JAT2 mRNA is expressed at a very low steady state level in whole plants, but is rapidly upregulated by methyl jasmonate treatment in a leaf-specific manner. To characterize the function of Nt-JAT2, yeast cells were used as the host organism in a cellular transport assay. Nt-JAT2 was localized at the plasma membrane in yeast cells. When incubated in nicotine-containing medium, the nicotine content in Nt-JAT2-expressing cells was significantly lower than in control yeast. Nt-JAT2-expressing cells also showed lower content of other alkaloids like anabasine and anatabine, but not of flavonoids, suggesting that Nt-JAT2 transports various alkaloids including nicotine. Fluorescence assays in BY-2 cells showed that Nt-JAT2-GFP was localized to the tonoplast. These findings indicate that Nt-JAT2 is involved in nicotine sequestration in leaf vacuoles following the translocation of nicotine from root tissues.

DOI： 10.1371/journal.pone.0108789

Components of Foods Inhibit a Drug Exporter, Human Multidrug and Toxin Extrusion Transporter 1 査読

Tatsuya Kawasaki, Hideyuki Ito, Hiroshi Omote

BIOLOGICAL & PHARMACEUTICAL BULLETIN 37 ( 2 ) 292 - 297 2014年2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：PHARMACEUTICAL SOC JAPAN

Human multidrug and toxic compounds extrusion transporter 1 (hMATE1/SLC47A1) is a H+-coupled organic cation exporter responsible for the final step of excretion of various xenobiotics at the kidney and liver. In this study, effects of dietary constituents on hMATE1 mediated drug transport were examined to evaluate possible food-drug interactions. Bergamottin inhibited hMATE1 mediated tetraethyl ammonium transport activity, with a K-i of 98.7 mu M. Coumarins, flavonols, and catechin inhibited hMATE1 activity. Among 23 compounds tested, isorhamnetin was the strongest inhibitor of hMATE1 with the K-i of 0.32 mu M in a competitive manner. Since isorhamnetin is abundant in Ginkgo biloba that is widely used for herbal supplements, the findings suggest the potential hMATE1 related food-drug interactions.

DOI： 10.1248/bpb.b13-00815

Essential role of vesicular nucleotide transporter in vesicular storage and release of nucleotides in platelets 査読

Miki Hiasa, Natsuko Togawa, Takaaki Miyaji, Hiroshi Omote, Akitsugu Yamamoto, Yoshinori Moriyama

Physiological Reports 2 ( 6 ) 2014年

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

Nucleotides are stored in the dense granules of platelets. The release of nucleotides triggers one of the first steps in a series of cascades responsible for blood coagulation. However, the mechanism of how the nucleotides are accumulated in the granules is still far less understood. The transporter protein responsible for storage of nucleotides in the neuroendocrine cells has been identified and characterized. We hypothesized that the vesicular nucleotide transporter (VNUT) is also involved in the vesicular storage of nucleotides in platelets. In this article, we present three lines of evidence that VNUT is responsible for the vesicular storage of nucleotides in platelets and that vesicular ATP transport is crucial for platelet function, detection and characterization of VNUT activity in platelets isolated from healthy humans and MEG-01 cells, RNA interference experiments on MEG-01 cells, and studies on nucleotide transport and release with a selective inhibitor.

DOI： 10.14814/phy2.12034

Vesicular GABA transporter (VGAT) transports β-alanine. 査読

Juge N, Omote H, Moriyama Y

Journal of neurochemistry 127 ( 4 ) 482 - 486 2013年11月

Inhibitors of ATP release inhibit vesicular nucleotide transporter 査読

Yuri Kato, Hiroshi Omote, Takaaki Miyaji

Biological and Pharmaceutical Bulletin 36 ( 11 ) 1688 - 1691 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Vesicular nucleotide transporter (VNUT) is responsible for vesicular ATP storage in ATP-secreting cells. In the present study, we examined the effects on VNUT-mediated transport of ATP release inhibitors such as ATP-binding cassette (ABC) proteins, hemichannels, maxi anion channels and P2X7 receptor. The ATP transport activity of proteoliposomes containing purified human VNUT was blocked by glibenclamide, carbenoxolone, 18 á-glycyrrhetinic acid, flufenamic acid, arachidonic acid and A438079 without the formation of Äø (positive inside) as a driving force being affected. Thus, inhibitors of ATP release may inhibit VNUT and subsequent ATP release, since the previous works proved that inhibitors of ATP release blocked VNUT-mediated ATP release at the cell level. © 2013 The Pharmaceutical Society of Japan.

DOI： 10.1248/bpb.b13-00544

Vesicular neurotransmitter transporters: An approach for studying transporters with purified proteins 査読

Hiroshi Omote, Yoshinori Moriyama

Physiology 28 ( 1 ) 39 - 50 2013年1月

記述言語：英語

Vesicular storage and subsequent release of neurotransmitters are the key processes of chemical signal transmission. In this process, vesicular neurotransmitter transporters are responsible for loading the signaling molecules. The use of a "clean biochemical" approach with purified, recombinant transporters has helped in the identification of novel vesicular neurotransmitter transporters and in the analysis of the control of signal transmission. © 2013 Int. Union Physiol. Sci./Am. Physiol. Soc.

DOI： 10.1152/physiol.00033.2012

Type 1 sodium-dependent phosphate transporter acts as a membrane potential-driven urate exporter 査読

Takaaki Miyaji, Tatsuya Kawasaki, Natsuko Togawa, Hiroshi Omote, Yoshinori Moriyama

Current Molecular Pharmacology 6 ( 2 ) 88 - 94 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）

SLC17A1 protein (NPT1) was the first identified member of the SLC17 phosphate transporter family, and is known to mediate Na+/inorganic phosphate (Pi) co-transport when expressed in Xenopus oocytes. Although this protein was suggested to be a renal polyspecific anion exporter, its transport properties were not well characterized. The clean biochemical approach revealed that proteoliposomes comprising purified NPT1 as the only protein source transport various organic anions such as urate, p-aminohippuric acid (PAH), and acetylsalicylic acid (aspirin) in a membrane potential (δ̄)-driven and Cl- -dependent manner. Human NPT1 carrying an SNP mutation, Thr269Ile, known to increase the risk of gout, exhibited 32% lower urate transport activity compared to the wild type protein, leading to the conclusion that NPT1 is the long searched for transporter responsible for renal urate excretion. In the present article, we summarized the history of identification of the urate exporter and its possible involvement in the dynamism of urate under physiological and pathological conditions. © 2013 Bentham Science Publishers.

DOI： 10.2174/18744672113069990035

A Na+-phosphate cotransporter homologue (SLC17A4 protein) is an intestinal organic anion exporter 査読

Natsuko Togawa, Takaaki Miyaji, Sho Izawa, Hiroshi Omote, Yoshinori Moriyama

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY 302 ( 11 ) C1652 - C1660 2012年6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：AMER PHYSIOLOGICAL SOC

Togawa N, Miyaji T, Izawa S, Omote H, Moriyama Y. A Na+ phosphate cotransporter homologue (SLC17A4 protein) is an intestinal organic anion exporter. Am J Physiol Cell Physiol 302: C1652-C1660, 2012. First published March 28, 2012; doi:10.1152/ajpcell.00015.2012.-The SLC17 anion transporter family comprises nine members that transport various organic anions in membrane potential (Delta psi)- and Cl- dependent manners. Although the transport substrates and physiological relevance of the majority of the members have already been determined, little is known about SLC17A4 proteins known to be Na+-phosphate cotransporter homologue (NPT homologue). In the present study, we investigated the expression and transport properties of human SLC17A4 protein. Using specific antibodies, we found that a human NPT homologue is specifically expressed and present in the intestinal brush border membrane. Proteoliposomes containing the purified protein took up radiolabeled p-aminohippuric acid (PAH) in a Cl--dependent manner at the expense of an electrochemical gradient of protons, especially Delta psi, across the membrane. The Delta psi- and Cl--dependent PAH uptake was inhibited by diisothiocyanostilbene-2,2'-disulfonic acid and Evans blue, common inhibitors of SLC17 family members. cis-Inhibition studies revealed that various anionic compounds, such as hydrophilic nonsteroidal anti-inflammatory drugs, pravastatin, and urate inhibited the PAH uptake. Proteoliposomes took up radiolabeled urate, with the uptake having properties similar to those of PAH uptake. These results strongly suggested that the human NPT homologue acts as a polyspecific organic anion exporter in the intestines. Since SLC17A1 protein (NPT1) and SLC17A3 protein (NPT4) are responsible for renal urate extrusion, our results reveal the possible involvement of a NPT homologue in urate extrusion from the intestinal duct.

DOI： 10.1152/ajpcell.00015.2012

Divalent Cation Transport by Vesicular Nucleotide Transporter 査読

Takaaki Miyaji, Keisuke Sawada, Hiroshi Omote, Yoshinori Moriyama

JOURNAL OF BIOLOGICAL CHEMISTRY 286 ( 50 ) 42881 - 42887 2011年12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：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Background: The vesicular nucleotide transporter (VNUT) transports nucleotides in the presence of Mg2+.
Results: VNUT transports divalent cations in a membrane potential-and nucleotide-dependent manner.
Conclusion: VNUT transports divalent cations as a nucleotide complex.
Significance: VNUT functions as a divalent cation importer in secretory vesicles.

DOI： 10.1074/jbc.M111.277269

Functional characterization of vesicular excitatory amino acid transport by human sialin 査読

Takaaki Miyaji, Hiroshi Omote, Yoshinori Moriyama

JOURNAL OF NEUROCHEMISTRY 119 ( 1 ) 1 - 5 2011年10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：WILEY-BLACKWELL

Sialin, the protein coded by SLC17A5, is responsible for membrane potential (Delta psi)-driven aspartate and glutamate transport into synaptic vesicles in addition to H(+)/sialic acid cotransport in lysosomes. Rodent sialin mutants harboring the mutations associated with Salla disease in humans did not transport aspartate and glutamate whereas H(+)/sialic acid cotransport activity was about one-third of the wild-type protein. In this study, we investigate the effects of various mutations on the transport activities of human sialin. Proteoliposomes containing purified heterologously expressed human sialin exhibited both Delta psi-driven aspartate and glutamate transport activity and H(+)/sialic acid co-transport activity. Aspartate and glutamate transport was not detected in the R39C and K136E mutant forms of SLC17A5 protein associated with Salla disease, whereas H(+)/sialic acid co-transport activity corresponded to 30-50% of the recombinant wild-type protein. In contrast, SLC17A5 protein harboring the mutations associated with infantile sialic acid storage disease, H183R and Delta 268SSLRN272 still showed normal levels of Delta psi-driven aspartate and glutamate transport even though H(+)/sialic acid co-transport activity was absent. Human sialin carrying the G328E mutation that causes both phenotypes, and P334R and G378V mutations that cause infantile sialic acid storage disease showed no transport activity. These results support the idea that people suffering from Salla disease have been defective in aspartergic and glutamatergic neurotransmissions.

DOI： 10.1111/j.1471-4159.2011.07388.x

Characterization of the human MATE2 proton-coupled polyspecific organic cation exporter 査読

Toshinori Komatsu, Miki Hiasa, Takaaki Miyaji, Takuji Kanamoto, Takuya Matsumoto, Masato Otsuka, Yoshinori Moriyama, Hiroshi Omote

INTERNATIONAL JOURNAL OF BIOCHEMISTRY & CELL BIOLOGY 43 ( 6 ) 913 - 918 2011年6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

Human multidrug and toxic compound extrusion 2 (hMATE2) is a kidney-specific isoform of hMATE1, an exporter of toxic organic cations (OCs) of exogenous and endogenous origins at the final excretion step in the kidneys and liver (Otsuka et al., 2005), and contains a splicing variant, MATE2K, that has an exon of hMATE2 deleted (Masuda et al., 2006). In the present study, we characterized the degree of expression and the transport properties of hMATE2. Quantitative PCR analysis with probes specific for hMATE2 indicated the presence of hMATE2 mRNA in the kidneys, which corresponded to 39% of total mRNA encoding both hMATE2 and hMATE2K. hMATE2-specific antibodies immunostained the renal urinary tubules. Upon expression in HEK293 cells, hMATE2 was localized in intracellular vesicular structures, and thus transport activity of tetraethylammonium (TEA), a typical substrate for MATE transporters, by the cells was not detected. The hMATE2 protein was purified and reconstituted into liposomes. An artificially imposed pH gradient (Delta pH) across the proteoliposomal membrane drove the uptake of TEA. Dissipation of Delta pH by ammonium sulfate effectively inhibited the TEA uptake, while that of the membrane potential by valinomycin had little effect. The profiles of cis-inhibition of TEA transport by hMATE2 and hMATE2K are similar to each other. Thus, both hMATE2 and hMATE2K equally operate in the human kidneys to extrude OCs into the urine. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.biocel.2011.03.005

Vesicular Neurotransmitter Transporter: Bioenergetics and Regulation of Glutamate Transport 査読

Hiroshi Omote, Takaaki Miyaji, Narinobu Juge, Yoshinori Moriyama

BIOCHEMISTRY 50 ( 25 ) 5558 - 5565 2011年6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：AMER CHEMICAL SOC

Glutamate plays essential roles in chemical transmission as a major excitatory neurotransmitter. The accumulation of glutamate in Secretory vesicles is mediated by vesicular glutamate transporters (VGLUTs) that together with the driving electrochemical gradient of proteins influence the subsequent quantum release Of glutamate and the function of higher order neurons. The vesicular content of glutamate is Well correlated with membrane potential (Delta psi) which suggests that Delta psi determines the vesicular glutamate concentration The transport of glutamate into secretory vesicles is highly dependent on Cl(-). This anion stimulates glutamate transport but is inhibitory at higher concentrations. Accumulating evidence indicates that Cl(-) regulates glutamate transport through control of VGLUT activity and the H(+) electrochemical gradient. Recently, a comprehensive study demonstrated that Cl(-) regulation of VGLUT is competitively inhibited by metabolic intermediates such as ketone bodies. It also showed that ketone bodies are effective in controlling epilepsy. These results suggest a correlation between metabolic state and higher order brain function. We propose a novel function for Cl(-) as a fundamental regulator for signal transmission.

DOI： 10.1021/bi200567k

A Vesicular Transporter That Mediates Aspartate and Glutamate Neurotransmission 査読

Takaaki Miyaji, Hiroshi Omote, Yoshinori Moriyama

BIOLOGICAL & PHARMACEUTICAL BULLETIN 33 ( 11 ) 1783 - 1785 2010年11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：PHARMACEUTICAL SOC JAPAN

Aspartate, an excitatory amino acid, is known to be stored in synaptic vesicles and exocytosed from some neurons to perform aspartergic neurotransmission. Through in vitro reconstitution, we found that sialin, a lysosomal sialic acid exporter, is responsible for the vesicular storage of aspartate in hippocampal neurons and pinealocytes. Mutations found in Salla disease cause decreased aspartate transport activity without affecting sialic acid transport. Thus, sialin is a multifunctional transporter. It is possible that people with Salla disease lose the ability of aspartergic neurotransmission, and this could explain why Salla disease involves severe neurological defects.

DOI： 10.1248/bpb.33.1783

Metabolic Control of Vesicular Glutamate Transport and Release 査読

Narinobu Juge, John A. Gray, Hiroshi Omote, Takaaki Miyaji, Tsuyoshi Inoue, Chiaki Hara, Hisayuki Uneyama, Robert H. Edwards, Roger A. Nicoll, Yoshinori Moriyama

NEURON 68 ( 1 ) 99 - 112 2010年10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：CELL PRESS

Fasting has been used to control epilepsy since antiquity, but the mechanism of coupling between metabolic state and excitatory neurotransmission remains unknown. Previous work has shown that the vesicular glutamate transporters (VGLUTs) required for exocytotic release of glutamate undergo an unusual form of regulation by Cl(-). Using functional reconstitution of the purified VGLUTs into proteoliposomes, we now show that Cl(-) acts as an allosteric activator, and the ketone bodies that increase with fasting inhibit glutamate release by competing with at the site of allosteric regulation. Consistent with these observations, acetoacetate reduced quantal size at hippocampal synapses and suppresses glutamate release and seizures evoked with 4-aminopyridine in the brain. The results indicate an unsuspected link between metabolic state and excitatory neurotransmission through anion-dependent regulation of VGLUT activity.

DOI： 10.1016/j.neuron.2010.09.002

Type 1 Sodium-dependent Phosphate Transporter (SLC17A1 Protein) Is a Cl--dependent Urate Exporter 査読

Masafumi Iharada, Takaaki Miyaji, Takahiro Fujimoto, Miki Hiasa, Naohiko Anzai, Hiroshi Omote, Yoshinori Moriyama

JOURNAL OF BIOLOGICAL CHEMISTRY 285 ( 34 ) 26107 - 26113 2010年8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：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

SLC17A1 protein (NPT1) is the first identified member of the SLC17 phosphate transporter family and mediates the transmembrane cotransport of Na+/P-i in oocytes. Although this protein is believed to be a renal polyspecific anion exporter, its transport properties are not well characterized. Here, we show that proteoliposomes containing purified SLC17A1 transport various organic anions such as p-aminohippuric acid and acetylsalicylic acid (aspirin) in an inside positive membrane potential (Delta psi)-dependent manner. We found that NPT1 also transported urate. The uptake characteristics were similar to that of SLC17 members in its Cl- dependence and inhibitor sensitivity. When arginine 138, an essential amino acid residue for members of the SLC17 family such as the vesicular glutamate transporter, was specifically mutated to alanine, the resulting mutant protein was inactive in Delta psi-dependent anion transport. Heterologously expressed and purified human NPT1 carrying the single nucleotide polymorphism mutation that is associated with increased risk of gout in humans exhibited 32% lower urate transport activity compared with the wild type protein. These results strongly suggested that NPT1 is a Cl--dependent polyspecific anion exporter involved in urate excretion under physiological conditions.

DOI： 10.1074/jbc.M110.122721

Tricks of the trade used to accelerate high-resolution structure determination of membrane proteins 査読

Yo Sonoda, Alex Cameron, Simon Newstead, Hiroshi Omote, Yoshinori Moriyama, Michihiro Kasahara, So Iwata, David Drew

FEBS LETTERS 584 ( 12 ) 2539 - 2547 2010年6月

記述言語：英語出版者・発行元：ELSEVIER SCIENCE BV

The rate at which X-ray structures of membrane proteins are solved is on a par with that of soluble proteins in the late 1970s. There are still many obstacles facing the membrane protein structural community. Recently, there have been several technical achievements in the field that have started to dramatically accelerate structural studies. Here, we summarize these so-called 'tricks-of-thetrade' and include case studies of several mammalian transporters. (C) 2010 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

DOI： 10.1016/j.febslet.2010.04.015

Vesicular Inhibitory Amino Acid Transporter Is a Cl-/gamma-Aminobutyrate Co-transporter 査読

Narinobu Juge, Akiko Muroyama, Miki Hiasa, Hiroshi Omote, Yoshinori Moriyama

JOURNAL OF BIOLOGICAL CHEMISTRY 284 ( 50 ) 35073 - 35078 2009年12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：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

The vesicular inhibitory amino acid transporter (VIAAT) is a synaptic vesicle protein responsible for the vesicular storage of gamma-aminobutyrate (GABA) and glycine which plays an essential role in GABAergic and glycinergic neurotransmission. The transport mechanism of VIAAT remains largely unknown. Here, we show that proteoliposomes containing purified VIAAT actively took up GABA upon formation of membrane potential (Delta psi) (positive inside) but not Delta pH. VIAAT-mediated GABA uptake had an absolute requirement for Cl- and actually accompanied Cl- movement. Kinetic analysis indicated that one GABA molecule and two Cl- equivalents were transported during one transport cycle. VIAAT in which Glu(213) was specifically mutated to alanine completely lost the ability to take up both GABA and Cl-. Essentially the same results were obtained with glycine, another substrate of VIAAT. These results demonstrated that VIAAT is a vesicular Cl- transporter that co-transports Cl- with GABA or glycine in a Delta psi dependent manner. It is concluded that Cl- plays an essential role in vesicular storage of GABA and glycine.

DOI： 10.1074/jbc.M109.062414

[Localization mechanism of vesicular neurotransmitter transporters]. 査読

Omote, H., Moriyama, Y.

Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 53 ( 16 Suppl ) 2220 - 2224 2008年12月

Vesicular glutamate transporter acts as a metabolic regulator 査読

Yoshinori Moriyama, Hiroshi Omote

BIOLOGICAL & PHARMACEUTICAL BULLETIN 31 ( 10 ) 1844 - 1846 2008年10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：PHARMACEUTICAL SOC JAPAN

Vesicular glutamate transporter (VGLUT) is responsible for the active transport of L-glutamate into synaptic vesicles and, thus, plays an essential role in the glutamatergic chemical transmission in the central and peripheral nervous systems. Recent studies indicated that VGLUT is also expressed and localized in various secretory vesicles in non-neuronal peripheral organelles such as hormone-containing secretory granules in endocrine cells. L-Glutamate is stored in VGLUT-containing organelles, secreted upon stimulation, and then acts as a paracrine and/or autocrine modulator to regulate cellular functions. Thus. VGLUT is a key molecule for glutamate signaling and is the core of a novel signaling system.

DOI： 10.1248/bpb.31.1844

Identification of a vesicular aspartate transporter 査読

Takaaki Miyaji, Noriko Echigo, Miki Hiasa, Shigenori Senoh, Hiroshi Omote, Yoshinori Moriyama

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 105 ( 33 ) 11720 - 11724 2008年8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：NATL ACAD SCIENCES

Aspartate is an excitatory amino acid that is costored with glutamate in synaptic vesicles of hippocampal neurons and synaptic-like microvesicles (SLMVs) of pinealocytes and is exocytosed and stimulates neighboring cells by binding to specific cell receptors. Although evidence increasingly supports the occurrence of aspartergic neurotransmission, this process is still debated because the mechanism for the vesicular storage of aspartate is unknown. Here, we show that sialin, a lysosomal H+/sialic acid cotransporter, is present in hippocampal synaptic vesicles and pineal SLMVs. RNA interference of sialin expression decreased exocytosis of aspartate and glutamate in pinealocytes. Proteoliposomes containing purified sialin actively accumulated aspartate and glutamate to a similar extent when inside positive membrane potential is imposed as the driving force. Sialin carrying a mutation found in people suffering from Salla disease (R39C) was completely devoid of aspartate and glutamate transport activity, although it retained appreciable H+/sialic acid cotransport activity. These results strongly suggest that sialin possesses dual physiological functions and acts as a vesicular aspartate/glutamate transporter. It is possible that people with Salla disease lose aspartergic (and also the associated glutamatergic) neurotransmission, and this could provide an explanation for why Salla disease causes severe neurological defects.

DOI： 10.1073/pnas.0804015105

　前のページ - 次のページ　

1
2
3
4
5