PT - JOURNAL ARTICLE AU - Marion Blomenröhr AU - Anders Heding AU - Robin Sellar AU - Rob Leurs AU - Jan Bogerd AU - Karin A. Eidne AU - Gary B. Willars TI - Pivotal Role for the Cytoplasmic Carboxyl-Terminal Tail of a Nonmammalian Gonadotropin-Releasing Hormone Receptor in Cell Surface Expression, Ligand Binding, and Receptor Phosphorylation and Internalization AID - 10.1124/mol.56.6.1229 DP - 1999 Dec 01 TA - Molecular Pharmacology PG - 1229--1237 VI - 56 IP - 6 4099 - http://molpharm.aspetjournals.org/content/56/6/1229.short 4100 - http://molpharm.aspetjournals.org/content/56/6/1229.full SO - Mol Pharmacol1999 Dec 01; 56 AB - The gonadotropin-releasing hormone receptor (GnRH-R) of the African catfish couples to phospholipase C and belongs to the large family of G protein-coupled receptors. We recently demonstrated that removal of the carboxyl-terminal tail (S331–Q379) from the catfish GnRH-R results in a loss of agonist binding; the current study sought to define more precisely the role of this region in receptor function. Progressive truncations of the carboxyl-terminal tail decreased cell surface expression detected by either enzyme-linked immunosorbent assay or agonist-binding. The two most truncated receptors (stop331 and stop337) showed no binding but were detected at the cell surface by enzyme-linked immunosorbent assay. All receptors able to bind agonist were also able to activate phospholipase C. The catfish GnRH-R was phosphorylated after agonist-occupation and use of truncated mutants showed this phosphorylation to be within the carboxyl-terminal tail. Furthermore, studies with S356A, S363A and SS356,363AA mutant receptors demonstrated that Ser363 is a major site of agonist-induced phosphorylation. The absence of this phospho-acceptor site markedly impaired agonist-mediated receptor internalization. In addition, both, Ser363 and the last 12 residues of the tail (not containing Ser363) were shown to be important for β-arrestin-dependent internalization. These observations are relevant to the regulatory function of the carboxyl-terminal tail of G protein-coupled receptors in general and are particularly intriguing given the absence of this region in mammalian GnRH-Rs.