Isolation and characterization of an alpha 2-type zebrafish glycine receptor subunit

The complementary DNA for a novel or subunit of the glycine receptor, alpha Z2, was isolated from a zebrafish adult brain library. The molecular chara cteristics, phylogenetic relationships and messenger RNA length of this alp ha Z2 subunit show it to be an alpha2-type glycine receptor subunit isoform . The leader peptide however, diverges from those of known glycine receptor oc isoforms. Recombinantly expressed in Xenopus oocytes, alpha Z2 formed f unctional glycine receptor channels. These homomeric channels were activate d by glycine and taurine, with apparent affinities similar to those reporte d for zebrafish alpha Z1 glycine receptor, and were also effectively antago nized by nanomolar concentrations of strychnine. However, during prolonged applications of agonists, ionic currents of alpha Z2 receptor channels decl ined to a much lower steady-state level than those of alpha Z1, indicating different desensitization properties. Analysis of messenger RNA revealed th at alpha Z2 is specifically expressed in adult brain tissue and present in both adult and embryonic zebrafish. This report contributes to the characterization of the diversity of glycine receptor isoforms in vertebrates. (C) 2001 IBRO. Published by Elsevier Sci ence Ltd. All rights reserved.