Glia of the cholinergic electromotor nucleus of Torpedo are the source of the cDNA encoding a GAT-1-like GABA transporter.

A PCR-based strategy was used to clone DNAs encoding Na(+)- and Cl(-)-dependent cotransport proteins using DNA from the cholinergic electromotor nucleus of Torpedo californica. This cloning strategy resulted in the isolation of a cDNA clone that shows strong nucleotide sequence homology to the GABA transporter-1 (GAT-1) types of rat and human brain. When expressed in frog oocytes, this transporter mediates the uptake of GABA. Moreover, physiologically and pharmacologically, the Torpedo protein behaves very similarly to the rat and human GAT-1 proteins. However, in contrast to the predominantly neuronal localization of the mammalian GAT-1 proteins, the mRNA for the fish protein is found almost exclusively in glial elements of the electromotor nucleus. This unexpected discovery of a GABA transporter cDNA in a nucleus that has no previously characterized GABAergic innervation raises questions about the role of GABA and this transporter in the electromotor system. Several speculative models for GABA function are proposed.