Cloning and characterization of cDNAs encoding putative glutamate transporters from Caenorhabditis elegans and Onchocerca volvulus

We report the identification and partial characterization of cDNAs encoding for putative glutamate transporters from the free-living nematode Caenorhabditis elegans and the filarial parasite Onchocerca volvulus. Glutamate transporters can be used as reliable markers for identifying cells and neurons that synaptically release glutamate and aspartate. An amplified PCR fragment containing a highly conserved amino acid heptamer found in all vertebrate glutamate transporters was used to screen a C. elegans cDNA library. Two full-length cDNA sequences from C. elegans were deduced from the isolated cDNA clones and RT-PCR products with the splice leader. The two C. elegans cDNA sequences differ by only 97 nucleotides at the 5' end. The C. elegans glutamate transporter gene glt-1 spans at least 2.9 kb of chromosomal DNA and possesses nine exons and eight introns. Primers directed to the CeGlt cDNA were used with O. volvulus first-strand cDNA to amplify and isolate the O. volvulus cDNA homolog. The C. elegans and O. volvulus glutamate transporters are 98% identical over 492 amino acids to each other and 52 to 58% identical to the mammalian glutamate transporters. Antibodies generated against partial coding regions of the C. elegans glutamate transporter recognized a protein of approximately 66 kDa in C. elegans and O. volvulus protein extracts.