title: G proteins and autocrine signaling differentially regulate gonadotropin subunit expression in pituitary gonadotrope.
abstract: Gonadotropin-releasing hormone (GnRH) acts at gonadotropes to direct the synthesis of the gonadotropins, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). The frequency of GnRH pulses determines the pattern of gonadotropin synthesis. Several hypotheses for how the gonadotrope decodes GnRH frequency to regulate gonadotropin subunit genes differentially have been proposed. However, key regulators and underlying mechanisms remain uncertain. We investigated the role of individual G proteins by perturbations using siRNA or bacterial toxins. In LβT2 gonadotrope cells, FSHβ gene induction depended predominantly on Gα(q/11), whereas LHβ expression depended on Gα(s). Specifically reducing Gα(s) signaling also disinhibited FSHβ expression, suggesting the presence of a Gα(s)-dependent signal that suppressed FSH biosynthesis. The presence of secreted factors influencing FSHβ expression levels was tested by studying the effects of conditioned media from Gα(s) knockdown and cholera toxin-treated cells on FSHβ expression. These studies and related Transwell culture experiments implicate Gα(s)-dependent secreted factors in regulating both FSHβ and LHβ gene expression. siRNA studies identify inhibinα as a Gα(s)-dependent GnRH-induced autocrine regulatory factor that contributes to feedback suppression of FSHβ expression. These results uncover differential regulation of the gonadotropin genes by Gα(q/11) and by Gα(s) and implicate autocrine and gonadotrope-gonadotrope paracrine regulatory loops in the differential induction of gonadotropin genes.
authors.affiliation: Center for Translational Systems Biology and the Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Soon-Gang
authors.initials: SG
authors.lastname: Choi
authors.forename: Jingjing
authors.initials: J
authors.lastname: Jia
authors.forename: Robert L
authors.initials: RL
authors.lastname: Pfeffer
authors.forename: Stuart C
authors.initials: SC
authors.lastname: Sealfon
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000502:physiology*; D002460:Cell Line; D005640:Follicle Stimulating Hormone / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone; D006062:Gonadotropins / Q000235:genetics / Q000378:metabolism; D007986:Luteinizing Hormone / Q000235:genetics / Q000378:metabolism; D051379:Mice; D010902:Pituitary Gland / Q000378:metabolism*
chemical_list: D006062:Gonadotropins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D019204:GTP-Binding Proteins