title: A direct role for arrestins in desensitization of the luteinizing hormone/choriogonadotropin receptor in porcine ovarian follicular membranes.
abstract: The luteinizing hormone/choriogonadotropin (LH/CG) receptor (R) is a heptahelical R that, upon agonist binding, activates the stimulatory guanine nucleotide-binding protein (Gs) and the downstream effector adenylyl cyclase (AC). Like other G protein-coupled Rs, the LH/CG R subsequently exhibits reduced agonist-dependent effector activity, or desensitization, in response to saturating agonist. Unlike desensitization of many other G protein-coupled Rs, the in vivo desensitization response of LH/CG R-stimulated AC activity of ovarian follicles to the preovulatory surge of LH can be mimicked under cell-free conditions. Based on evidence that porcine ovarian follicular membranes unexpectedly contained beta-arrestin-1, the role of arrestins in desensitization of the LH/CG R was investigated. Results showed that neutralizing arrestin antibodies blocked the development of desensitization and that desensitization was rescued with a synthetic peptide corresponding to the antibody-binding epitope on beta-arrestin-1. These results suggest that endogenous beta-arrestin-1 participates in agonist-dependent desensitization of the LH/CG R. Addition of recombinant purified beta-arrestin-1 mimicked human chorionic gonadotrophin to promote desensitization of human chorionic gonadotrophin-stimulated AC activity, in the presence of the ATP phosphorylation antagonist adenylyl-imidodiphosphate, with an ED50 of approximately 0.1 nM. Increased levels of an 87-kDa protein reactive with glycoprotein hormone R-reactive antibody, consistent with the LH/CG R, coimmunoprecipitated with follicular membrane beta-arrestin-1 in response to LH/CG R activation compared with unactivated R. Taken together, these results show that ovarian follicles contain membrane-associated beta-arrestin-1, that beta-arrestin-1 participates in agonist-dependent desensitization of the LH/CG R, and that the trigger for beta-arrestin-1 binding to the LH/CG R appears to be R activation.
authors.affiliation: Department of Cell and Molecular Biology, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, IL 60611, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mukherjee
authors.forename: K
authors.initials: K
authors.lastname: Palczewski
authors.forename: V
authors.initials: V
authors.lastname: Gurevich
authors.forename: J L
authors.initials: JL
authors.lastname: Benovic
authors.forename: J P
authors.initials: JP
authors.lastname: Banga
authors.forename: M
authors.initials: M
authors.lastname: Hunzicker-Dunn
mesh_terms: D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D006080:Ovarian Follicle / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D011233:Precipitin Tests; D011485:Protein Binding; D011974:Receptors, LH / Q000819:agonists / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D013552:Swine; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
chemical_list: C000605253:ARRB1 protein, human; D019390:Arrestins; D010446:Peptide Fragments; D011974:Receptors, LH; D011994:Recombinant Proteins; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D000266:Adenylyl Imidodiphosphate; D019204:GTP-Binding Proteins