The @entity140 receptor (AMPAR), a pharmacologically defined ionotropic @entity2227 receptor, mediates fast excitatory synaptic transmission in the vertebrate central nervous system. @entity1 and avian AMPARs are assembled from the products of four genes ( @entity7335 - @entity11587 ) conserved in their translated sequences and gene organizations. Teleost fish also express AMPAR subunits; however, the AMPAR genes have not been extensively investigated in lower vertebrates. To elucidate the evolution of vertebrate AMPAR genes, reverse-transcriptase PCR-based surveys of subunits expressed in the brains of eight nonmammalian vertebrates were performed. The newly cloned vertebrate AMPAR subunits were classified by their sequence identities to the @entity1 AMPAR subunits. The results of molecular and phylogenetic analyses indicated that the members of the AMPAR gene family increased from two in the jawless @entity14994 to four in the tetrapods and the shark and to more than four in the teleost fish. The sizes of AMPAR gene families correlate well with those of many multigene families observed in various vertebrates. Moreover, all vertebrates expressed at least one AMPAR subunit bearing an @entity369 (R) at the Q/R site, at which no invertebrate @entity2227 receptor subunit has been found to have an R residue, suggesting that the low @entity460 -permeable AMPARs appeared at early evolutionary stages of vertebrate central nervous systems. Uniquely, the loop 1 (L1) regions between hydrophobic domain 1 and hydrophobic domain 2 of the @entity14994 putative GRIA2 and all the teleost @entity7335 subunits were much longer than those of the remaining known ionotropic @entity2227 receptor subunits. The length and sequence of the L1 of teleost @entity7335 subunits were heterogeneous, suggesting that the @entity535 residues in L1 were not highly selected.

Identifications, classification, and evolution of the vertebrate XXXX ( @entity140 ) receptor subunit genes.

@entity1 :: ('9606', 'Species') :: ['mammalian', 'Mammalian'] @entity2227 :: ('CHEBI:29987', 'Chemical') :: ['glutamate'] @entity535 :: ('CHEBI:33704', 'Chemical') :: ['amino acid'] @entity14994 :: ('7769', 'Species') :: ['hagfish'] @entity11587 :: ('2893', 'Gene') :: ['GRIA4'] @entity140 :: ('MESH:D018350', 'Chemical') :: ['AMPA'] @entity460 :: ('MESH:D002118', 'Chemical') :: ['calcium'] @entity369 :: ('CHEBI:29016', 'Chemical') :: ['arginine'] @entity7335 :: ('2890', 'Gene') :: ['GRIA1']
@entity140 :: (MESH:D018350,Chemical) :: ['alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid']
