Cloning and expression of a rat brain L-glutamate transporter

SYNAPTIC transmission of most vertebrate synapses is thought to be terminated by rapid transport of the neurotransmitter into presynaptic nerve terminals or neuroglia ^1-5. L-Glutamate is the major excitatory transmitter in brain and its transport represents the mechanism by which it is removed from the synaptic cleft and kept below toxic levels ^5,6. Here we use an antibody against a glial L-glutamate transporter from rat brain⁷ to isolate a complementary DNA clone encoding this transporter. Expression of this cDNA in transfected HeLa cells indicates that L-glutamate accumulation requires external sodium and internal potassium and transport shows the expected stereospecificity. The cDNA sequence predicts a protein of 573 amino acids with 8-9 putative transmembrane α-helices. Database searches indicate that this protein is not homologous to any identified protein of mammalian origin, including the recently described superfamily of neurotransmitter transporters. This protein therefore seems to be a member of a new family of transport molecules.