MOLECULAR AND ELECTROPHYSIOLOGICAL CHARACTERIZATIONS OF FGLUR3-ALPHA,AN IONOTROPIC GLUTAMATE-RECEPTOR SUBUNIT OF A TELEOST FISH

Here we report the cloning and functional analysis of a cDNA encoding a functional glutamate receptor subunit of Oreochromis sp., a freshwat er teleost fish. The deduced amino acid sequence of this cDNA clone, f GluR3 alpha, displays the highest sequence identity to that of the mam malian GluR3 subunit. Results of quantitative reverse-transcriptase po lymerase chair: reaction (RT-PCR) analysis indicated that the expressi on level of fGluR3 alpha in the cerebellum was much less than that in the telencephalon and optical lobe. Similar to its mammalian counterpa rt, variants of fGluR3 alpha were created by alternative splicing and RNA editing at the R/G site. The channel properties of homomeric fGluR 3 alpha expressed in Xenopus oocytes were similar to those of the mamm alian alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) -preferring receptors. The rank order of agonist potency of the expres sed fGluR3 alpha is AMPA greater than or equal to glutamate greater th an or equal to quisqualate > domoate greater than or equal to kainate. This is the first functional glutamate receptor of teleost fish being demonstrated to be sensitive to AMPA. Furthermore, this study suggest ed a strong functional conservation of AMPA-preferring receptors in ve rtebrates. (C) 1998 Elsevier Science B.V. All rights reserved.