Complementary distribution of vesicular glutamate transporters in the central nervous system.
Two vesicular glutamate transporters (VGluTs) have been identified at the molecular level very recently and revealed to possess similar pharmacological characteristics for glutamate uptake. Vesicular glutamate transporter 1 (VGluT1), which was originally named brain-specific Na+-dependent inorganic phosphate cotransporter (BNPI), is mainly expressed in telencephalic regions, whereas vesicular glutamate transporter 2 (VGluT2), formerly referred to as differentiation-associated Na+-dependent inorganic phosphate cotransporter (DNPI), is produced principally in diencephalic and lower brainstem regions. Since no other proteins show as high molecular similarity to VGluT1 or VGluT2 as the two transporters exhibit, it is likely that the mammalian central nervous system use only two gene products for vesicular glutamate uptake. Immunoelectron-microscopic analysis has revealed that the two VGluTs are located on synaptic vesicles in axon terminals making an asymmetric type of synapses, supporting that they serve as vesicular transporters in excitatory terminals. Furthermore, mRNA and immunoreactivity for VGluTs are distributed largely in a complementary fashion to distinct populations of excitatory neurons; for example, in the cerebral cortex, thalamocortical axon terminals use VGluT2, whereas excitatory axon terminals of corticocortical or intracortical fibers seem to apply VGluT1 for glutamate uptake. This complementary distribution might suggest that the two VGluTs have an as yet unknown difference in functions.
Kaneko
Takeshi
T
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, 606-8501, Kyoto, Japan. kaneko@mbs.med.kyoto-u.ac.jp
Fujiyama
Fumino
F
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002490:Central Nervous System / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D026901:Membrane Transport Proteins; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C493476:SLC17A6 protein, human; C493464:SLC17A7 protein, human; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid