The function of the excitatory neurotransmitter L-glutamate is not well defined in invertebrates. High-affinity glutamate transport by transporter molecules is essential in modulation of synaptic transmission and regulation of extracellular glutamate concentrations. Our goal is to characterize the glutamate transporter subtypes and identify the glutamatergic cells and neurons in C. elegans. Results of screening genomic and cDNA libraries and database searching indicates there may be five subtypes of glutamate transporters in C. elegans. The five transporter subtypes map to three different chromosomes (LG II, IV and X) and are 57-34% identical at the protein level to the vertebrate glutamate transporters. Previously, we have identified and cloned the glutamate transporter
glt-1 (LG X). The
glt-1 mRNA is alternately spliced resulting in two mRNA species encoding proteins differing by only 11 amino acids at the amino terminus. The expression pattern of
glt-1 was examined in transgenic worms that express GFP under control of the upstream
glt-1 sequences. GFP was expressed in the M3 pharyngeal neuron, eight cells in the male tail and six yet unidentified cells. Surprisingly GFP was also expressed in the anterior hypodermal cells
hyp1-6. We intend to confirm the GFP localizations using indirect immunofluorescence with affinity purified antibodies raised against recombinant GLT-1 protein. Our aim is to isolate the full length cDNAs from each subtype in order to study functional expression by transient expression in COS cells.