We describe a P2X subunit cloned from the zebrafish (Danio rerio) that is an orthologue of the mammalian P2X3 subunit. Like the mammalian P2X3, this receptor desensitizes rapidly in the presence of agonist. However, it differs in that αβ-meATP is a much less potent agonist than ATP and the antagonist TNP-ATP is not active at low nanomolar concentrations. Similar to the rat P2X3 subunit, the zebrafish subunit forms hetero-oligomeric assemblies with the rat P2X2 that possesses a phenotype distinct from either parent. This novel clone will provide an important basis for future experiments investigating the structure/function relationships of P2X subunit domains.
