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.
Haisenleder
Daniel J
DJ
Division of Endocrinology, Department of Medicine, University of Virginia Health Science Center, Charlottesville, Virginia 22908, USA. djh2q@virginia.edu
Ferris
Heather A
HA
Shupnik
Margaret A
MA
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