Cloning and characterization of a zebrafish Y2 receptor.

The NPY receptors belong to the superfamily of G-protein coupled receptors and in mammals this family has five members, named Y1, Y2, Y4, Y5, and Y6. In bony fish, four receptors have been identified, named Ya, Yb, Yc and Y7. Yb and Y7 arose prior to the split between ray-fined fishes and tetrapods and have been lost in mammals. Yc appeared as a copy of Yb in teleost fishes. Ya may be an ortholog of Y4, but surprisingly no unambiguous receptor ortholog to any of the mammalian subtypes has yet been identified in bony fishes. Here we present the cloning and pharmacological characterization of a Y2 receptor in zebrafish, Danio rerio. To date, this is the first Y2 receptor outside mammals and birds that has been characterized pharmacologically. Phylogenetic analysis and synteny confirmed that this receptor is orthologous to mammalian Y2. We show that the receptor is pharmacologically most similar to chicken Y2 which leads to the conclusion that Y2 has acquired several novel characteristics in mammals. Y2 from zebrafish binds very poorly to the Y2-specific antagonist BIIE0246. Our pharmacological characterization supports our previous conclusions regarding the binding pocket of BIIE0246 in the human Y2 receptor.