Neuron-specific human glutamate transporter: molecular cloning, characterization and expression in human brain.

A cDNA encoding a neuron-specific glutamate/aspartate transporter was isolated from human brain cDNA libraries and characterized. The new cDNA, designated human glutamate transporter III, is structurally distinct from two previously described brain specific glutamate transporters. This human cDNA is 90% and 95% homologous at nucleotide and amino acid level, respectively, with a previously reported rabbit glutamate/aspartate transporter. Northern blot analysis of human tissues revealed that the mRNA of this transporter is expressed in brain, liver, muscle, ovary, testis and in retinoblastoma cell lines. In situ hybridization in human brain sections showed that the mRNA is densely expressed in substantia nigra, red nucleus, hippocampus, and in cerebral cortical layers. Southern blot analysis revealed that the gene encoding this mRNA exists as a single copy in the human genome.