Abstract
Glutamate receptors are the predominant excitatory neurotransmitter receptors in vertebrate central nervous system. Ionotropic glutamate receptors have been divided into three subtypes, AMPA, kainate and NMDA receptors, according to their pharmacological properties. The mammalian brain expresses four AMPA receptor subunits, whereas the brains of telapia (Oreochromis mossambicus), puffer fish (Tetraodon fluviatilis) and zebrafish (Danio rerio) express eight or seven AMPA subunits. The genomic DNA encoding TMI and TMII segments of the teleost AMPA receptor subunits were cloned by PCR and by library screening. The results revealed that the gene structures of the teleost AMPA receptor subunits varied in this region. The TMI、L1 and TMII coding sequences of GluR1β genes of telapia and puffer fish are encoded by three exons, and that of telapia GluR2α (fGluR2α) are splice to two exons. A single exon encoding TMI, L1 and TMII was found in the remaining AMPA receptor genes. In addiction, DNA sequence analysis reveals the presence of an glutamine codon at the Q/R site of the zebrafish GluR2α, indicating that the arginine codon at the Q/R site is generated by RNA editing. On the other hand, the presence of an arginine codon at the Q/R site of the zebrafish GluR2β, indicating that the arginine codon at the Q/R site of zGluR2β is not created by RNA editing. This study reveals that Q/R editing mechanism is conservated in vertebrate.