Molecular cloning and functional identification of mouse vesicular glutamate transporter 3 and its expression in subsets of novel excitatory neurons.
We have cloned and functionally characterized a third isoform of a vesicular glutamate transporter (VGLUT3) expressed on synaptic vesicles that identifies a distinct glutamatergic system in the brain that is partly and selectively promiscuous with cholinergic and serotoninergic transmission. Transport activity was specific for glutamate, was H(+)-dependent, was stimulated by Cl(-) ion, and was inhibited by Rose Bengal and trypan blue. Northern analysis revealed higher mRNA levels in early postnatal development than in adult brain. Restricted patterns of mRNA expression were observed in presumed interneurons in cortex and hippocampus, and projection systems were observed in the lateral and ventrolateral hypothalamic nuclei, limbic system, and brainstem. Double in situ hybridization histochemistry for vesicular acetylcholine transporter identified VGLUT3 neurons in the striatum as cholinergic interneurons, whereas VGLUT3 mRNA and protein were absent from all other cholinergic cell groups. In the brainstem VGLUT3 mRNA was concentrated in mesopontine raphé nuclei. VGLUT3 immunoreactivity was present throughout the brain in a diffuse system of thick and thin beaded varicose fibers much less abundant than, and strictly separated from, VGLUT1 or VGLUT2 synapses. Co-existence of VGLUT3 in VMAT2-positive and tyrosine hydroxylase -negative varicosities only in the cerebral cortex and hippocampus and in subsets of tryptophan hydroxylase-positive cell bodies and processes in differentiating primary raphé neurons in vitro indicates selective and target-specific expression of the glutamatergic/serotoninergic synaptic phenotype.
Schäfer
Martin K-H
MK
Department of Molecular Neuroscience, Institute of Anatomy and Cell Biology, Philipps University Marburg, D-35033 Marburg, Germany.
Varoqui
Hélène
H
Defamie
Norah
N
Weihe
Eberhard
E
Erickson
Jeffrey D
JD
D000595:Amino Acid Sequence; D026922:Amino Acid Transport Systems, Acidic / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D003342:Corpus Striatum / Q000378:metabolism; D020224:Expressed Sequence Tags; D005786:Gene Expression Regulation; D007031:Hypothalamus / Q000378:metabolism; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic; D050496:Vesicular Glutamate Transport Proteins
D026922:Amino Acid Transport Systems, Acidic; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; C460879:SLC17A8 protein, human; D050496:Vesicular Glutamate Transport Proteins