The calcium component of gonadotropin-releasing hormone-stimulated luteinizing hormone subunit gene transcription is mediated by calcium/calmodulin-dependent protein kinase type II.
Calcium influx plays a critical role in GnRH regulation of rat LH subunit gene transcription, but the site(s) of action are undefined. We investigated the potential of GnRH acting through calcium to activate calcium/calmodulin-dependent protein kinase type II (Ca/CaMK II) in mouse gonadotrope-derived LbetaT2 cells. GnRH stimulated Ca/CaMK II beta subunit activity 3-fold 2 min after treatment and returned to control values by 45 min. The Ca/CaMK II response to GnRH was blocked by administration of the Ca/CaMK II-specific inhibitor, KN-93. The calcium channel activator Bay K 8644 stimulated a 3-fold increase in Ca/CaMK II activity, similar to GnRH. Blocking calcium influx with nimodipine or depleting intracellular calcium storage pools with thapsigargin each resulted in a partial suppression of GnRH-induced activation of Ca/CaMK II, and in combination, completely suppressed the Ca/CaMK II response to GnRH. KN-93 and nimodipine also suppressed alpha-subunit and LHbeta promoter responses to GnRH by 40-60%. LHbeta promoter constructs containing either proximal or proximal and distal GnRH-responsive regions were sensitive to inhibition. These data show for the first time that Ca/CaMK II activation plays an important role in the transmission of GnRH signals from the plasma membrane to the LH subunit genes.
Division of Endocrinology, Department of Medicine, University of Virginia Health Science Center, Charlottesville, Virginia 22908, USA. djh2q@virginia.edu
Daniel J
DJ
Haisenleder
Heather A
HA
Ferris
Margaret A
MA
Shupnik
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics*; D051379:Mice; D010766:Phosphorylation; D010902:Pituitary Gland / Q000166:cytology; D011401:Promoter Regions, Genetic / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D000096926:Benzenesulfonamides
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D001596:Benzylamines; D002118:Calcium; D002120:Calcium Channel Agonists; D015220:Calcium Channels; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D037201:Follicle Stimulating Hormone, beta Subunit; D007987:Gonadotropin-Releasing Hormone; D037101:Luteinizing Hormone, beta Subunit; D013449:Sulfonamides; C072105:KN 93; D000096926:Benzenesulfonamides