CLONING AND CHARACTERIZATION OF THE CHICKEN THYROTROPIN-RELEASING-HORMONE RECEPTOR

We report on the cloning of the full-length complementary DNA for the chicken TRH receptor. Although the TRH receptor has been cloned from s everal mammalian species, this is the first report from another verteb rate class. The ligand binding pocket, which is situated in the transm embrane helixes of the mouse and rat TRH receptors, is completely cons erved in the chicken receptor. Pharmacological studies (receptor bindi ng and signaling) employing several TRH analogs revealed that there ar e no significant differences between the chicken and mouse receptors. These findings show that there have been considerable evolutionary con straints on TRH receptor structure and function. Several truncated for ms of the chicken TRH receptor that appear to retain a part of an intr on and are truncated in the putative third intracellular loop were als o cloned, but were nonfunctional. This study provides a useful tool fo r further studies on the roles of TRH in avian growth and TSH regulati on.