Differentiation-associated Na+-dependent Inorganic Phosphate Cotransporter (DNPI) Is a Vesicular Glutamate Transporter in Endocrine Glutamatergic Systems

Hayashi, Mitsuko; Otsuka, Masato; Morimoto, Riyo; Hirota, Sumiko; Yatsushiro, Shouki; Takeda, Jun; Yamamoto, Akira; Moriyama, Yoshinori

doi:10.1074/jbc.m106244200

Cited by 108 publications

(122 citation statements)

References 45 publications

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“…These VGLUTs seem to be potential probes for the site of L-glutamate release in peripheral tissues as well as the central nervous system since these transporters are essential for L-glutamate signal output. We have shown that VGLUT2 is expressed in ␣TC6 cells, clonal ␣ cells, and islet ␣ cells, but not in ␤ or ␦ cells (18). These results are consistent with the occurrence of Ca 2ϩ -dependent exocytosis of L-glutamate from ␣TC6 cells (22) and suggest that ␣ cells are the sites of L-glutamate signal appearance.…”

supporting

confidence: 77%

“…1C). Crude synaptic vesicles (LP2 fraction) were prepared as described previously (18). To prepare membrane fraction of islets, at least 500 islets were washed, suspended in 2 ml of 20 mM MOPS-Tris (pH 7.0) containing 0.3 M sucrose, 5 mM EDTA, 10 g/ml pepstatin A and 10 g/ml leupeptin, and homogenized by hand with a small glass homogenizer.…”

Section: Methodsmentioning

confidence: 99%

“…Antibodies-Site-specific rabbit polyclonal antibodies against rat VGLUT2 were raised as described previously (18). For the preparation of anti-VGLUT1 antibodies, DNA fragments encoding G506-S560 were amplified by PCR and cloned into the EcoR1 site of expression vector pGEX3X (Amersham Biosciences) to form glutathione S-transferase fusion plasmids.…”

Section: Methodsmentioning

confidence: 99%

“…Immunohistochemistry and Immunoelectronmicroscopy-Indirect immunofluorescence microscopy was performed as described previously, using an Olympus FV-300 confocal laser microscope (18). For immunoelectronmicroscopy, the LR White embedding immunogold method was used with a slight modification (30).…”

Section: Methodsmentioning

confidence: 99%

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Secretory Granule-mediated Co-secretion ofl-Glutamate and Glucagon Triggers Glutamatergic Signal Transmission in Islets of Langerhans

Hayashi

Yamada

Uehara

et al. 2003

Journal of Biological Chemistry

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122

158

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L-Glutamate is the major excitatory neurotransmitter in the central nervous system and plays important roles in many neuronal processes such as fast synaptic transmission and neuronal plasticity (1, 2). To use L-glutamate as an intercellular signaling molecule, neuronal cells develop the glutamatergic system. Thus, L-glutamate is accumulated in synaptic vesicles through vesicular glutamate transporters (VGLUTs), 1 and is secreted through exocytosis. The released L-glutamate binds to the receptor so as to transmit signals intercellularly. The excess amount of L-glutamate in synaptic cleft is sequestrated through plasma membrane-type glutamate transporter. Recent evidence has indicated that peripheral non-neuronal tissues also possess the glutamatergic system and use L-glutamate as an intercellular transmitter (3). The islet of Langerhans, a pancreatic miniature organ for the hormones regulating the blood glucose level, is composed of four major types of endocrine cells, i.e. insulin-secreting ␤ cells, glucagon-secreting ␣ cells, somatostatin-secreting ␦ cells, and pancreatic polypeptide-secreting F cells. These islet cells expresses functional glutamate receptors and plasma membrane-type glutamate transporter (4 -11), suggesting that L-glutamate functions as an intercellular transmitter in islet. In fact, L-glutamate has been shown to affect secretion of insulin or glucagon from islet cells, isolated islets, or perfused pancreas (4 -11). However, the role of L-glutamate as an intercellular chemical transmitter in the islets has been long controversial, mainly because critical issues, i.e. where, when, and how L-glutamate appears in the islets and what happens upon stimulation of glutamate receptors in the islets, remain unresolved.Recent findings indicate that brain-specific Na ϩ -dependent inorganic phosphate cotransporter (12) and its isoform, differentiation-associated Na ϩ -dependent inorganic phosphate cotransporter (13), function as VGLUTs and are thus abbreviated as VGLUT1 and VGLUT2, respectively (14 -21). These VGLUTs seem to be potential probes for the site of L-glutamate release in peripheral tissues as well as the central nervous system since these transporters are essential for L-glutamate signal output. We have shown that VGLUT2 is expressed in ␣TC6 cells, clonal ␣ cells, and islet ␣ cells, but not in ␤ or ␦ cells (18). These results are consistent with the occurrence of Ca 2ϩ -dependent exocytosis of L-glutamate from ␣TC6 cells (22) and suggest that ␣ cells are the sites of L-glutamate signal appearance.During course of the study, we noticed that the expression and subcellular localization of VGLUTs are of extraordinary

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supporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Secretory Granule-mediated Co-secretion ofl-Glutamate and Glucagon Triggers Glutamatergic Signal Transmission in Islets of Langerhans

Hayashi

Yamada

Uehara

et al. 2003

Journal of Biological Chemistry

Self Cite

122

158

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“…Multiple glutamate receptors have been found in the pancreas [13][14][15][16] . By functional and immunohistochemical studies, VGLUT, the protein responsible for the accumulation of glutamate from cytoplasm into the vesicles, has also been identified in islets of Langerhans 11,13 .…”

Section: Introductionmentioning

confidence: 99%

Sp1 Is Required for Glucose-Induced Transcriptional Regulation of Mouse Vesicular Glutamate Transporter 2 Gene

Bai

et al. 2008

Gastroenterology

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Background & Aims-Vesicular glutamate transporter (VGLUT) has been reported to be involved in glucose-induced insulin secretion. It has been shown that glucose stimulates the expression of VGLUT isoform 2 (VGLUT2) in β cells via transcriptional mechanism. In this study, we identified the mouse VGLUT2 (mVGLUT2) promoter and characterized the transcriptional mechanism of glucose-stimulated mVGLUT2 expression in β-cells.

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Distribution of vesicular glutamate transporter mRNA in rat hypothalamus

Ziegler

Cullinan

Herman

2002

J of Comparative Neurology

231

199

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Two isoforms of the vesicular glutamate transporter, VGLUT1 and VGLUT2, were recently cloned and biophysically characterized. Both VGLUT1 and VGLUT2 specifically transport glutamate into synaptic vesicles, making them definitive markers for neurons using glutamate as a neurotransmitter. The present study takes advantage of the specificity of the vesicular transporters to afford the first detailed map of putative glutamatergic neurons in the rat hypothalamus. In situ hybridization analysis was used to map hypothalamic distributions of VGLUT1 and VGLUT2 mRNAs. VGLUT2 is clearly the predominant vesicular transporter mRNA found in the hypothalamus; rich expression can be documented in regions regulating energy balance (ventromedial hypothalamus), neuroendocrine function (preoptic nuclei), autonomic tone (posterior hypothalamus), and behavioral/homeostatic integration (lateral hypothalamus, mammillary nuclei). Expression of VGLUT1 is decidedly more circumspect and is confined to relatively weak labeling in lateral hypothalamic regions, neuroendocrine nuclei, and the suprachiasmatic nucleus. Importantly, dual-label analysis revealed no incidence of colocalization of VGLUT1 or VGLUT2 mRNAs in glutamic acid decarboxylase (GAD) 65-positive neurons, indicating that GABA neurons do not express either transporter. Our data support a major role for hypothalamic glutamatergic neurons in regulation of all aspects of hypothalamic function.

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Differentiation-associated Na+-dependent Inorganic Phosphate Cotransporter (DNPI) Is a Vesicular Glutamate Transporter in Endocrine Glutamatergic Systems

Cited by 108 publications

References 45 publications

Secretory Granule-mediated Co-secretion ofl-Glutamate and Glucagon Triggers Glutamatergic Signal Transmission in Islets of Langerhans

Secretory Granule-mediated Co-secretion ofl-Glutamate and Glucagon Triggers Glutamatergic Signal Transmission in Islets of Langerhans

Sp1 Is Required for Glucose-Induced Transcriptional Regulation of Mouse Vesicular Glutamate Transporter 2 Gene

Distribution of vesicular glutamate transporter mRNA in rat hypothalamus

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