Internalization kinetics of the gonadotropin-releasing hormone (GnRH) receptor

This study quantified the agonist-induced endocytotic and recycling events of the mammalian gonadotropin releasing hormone receptor (GnRH-R) and inves tigated the role of the intracellular carboxyl (C)-terminal tail in regulat ing agonist-induced receptor internalization kinetics. The rate of internal ization for the rat GnRH-R was found to be exceptionally low when compared with G-protein coupled receptors (GPCRs) which possess a cytoplasmic C-term inal tail (thyrotropin-releasing hormone receptor (TRH-R), catfish GnRH-R ( cfGnRH-R) and GnRH/TRH-R chimeric receptor). These data provide evidence th at the presence of a functional intracellular cytoplasmic C-terminal tail i s essential for rapid internalization of the studied GPCRs.