title: Signaling responses to pulsatile gonadotropin-releasing hormone in LbetaT2 gonadotrope cells.
abstract: The hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) is secreted in a pulsatile fashion by hypothalamic neurons, and alterations in pulse frequency and amplitude differentially regulate gonadotropin synthesis and release. In this study, we investigated the kinetics of G(s) and G(q) signaling in response to continuous or pulsatile GnRH using fluorescence resonance energy transfer reporters in live mouse LbetaT2 gonadotrope cells. cAMP and protein kinase A-dependent reporters showed a rapid but transient increase in fluorescence resonance energy transfer signal with increasing doses of constant GnRH, and in contrast diacylglycerol (DAG) and calcium reporters showed a rapid and sustained signal. Multiple pulses of GnRH caused multiple pulses of cAMP and protein kinase A activation without desensitization, but the DAG and calcium reporters were rapidly desensitized resulting in inhibition of calcium and DAG responses. At the transcriptional level, both a cAMP-dependent cAMP-response element reporter and a DAG/calcium-dependent AP-1 reporter showed a pulse frequency-dependent increase in luciferase activity. However, constant GnRH stimulation gave very little cAMP-response element activation but very strong AP-1 activation. Based on these data, we propose that both the GnRH-R-G(s) and G(q) pathways are responsive to pulses of GnRH, but only the G(q) pathway is responsive to constant GnRH. Furthermore, the G(q) pathway is subject to desensitization with multiple GnRH pulses, but the G(s) pathway is not.
authors.affiliation: Medical Research Service, Veterans Affairs San Diego Healthcare System, San Diego, California 92161, USA.
authors.forename: Rie
authors.initials: R
authors.lastname: Tsutsumi
authors.forename: Devendra
authors.initials: D
authors.lastname: Mistry
authors.forename: Nicholas J G
authors.initials: NJ
authors.lastname: Webster
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D052681:Gonadotrophs / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D015151:Immunoblotting; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004075:Diglycerides; D018808:Transcription Factor AP-1; D007987:Gonadotropin-Releasing Hormone; D000242:Cyclic AMP; D008156:Luciferases; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium
references.citation: Biol Chem. 2001 Jul;382(7):1077-81
references.pmid: 11530939
references.citation: J Biol Chem. 2005 Aug 12;280(32):28981-8
references.pmid: 15964850
references.citation: Annu Rev Med. 1994;45:391-405
references.pmid: 8198390
references.citation: J Biol Chem. 1999 Oct 15;274(42):30146-53
references.pmid: 10514504
references.citation: Proc Natl Acad Sci U S A. 2004 Nov 23;101(47):16513-8
references.pmid: 15545605
references.citation: Mol Pharmacol. 2006 Apr;69(4):1280-7
references.pmid: 16368893
references.citation: Mol Endocrinol. 2008 Aug;22(8):1908-23
references.pmid: 18550775
references.citation: Theor Biol Med Model. 2004 Sep 24;1:9
references.pmid: 15447787
references.citation: Biochem Biophys Res Commun. 2006 Sep 22;348(2):716-21
references.pmid: 16895723
references.citation: Circ Res. 2005 Dec 9;97(12):1296-304
references.pmid: 16269655
references.citation: Mol Endocrinol. 2002 Mar;16(3):419-34
references.pmid: 11875099
references.citation: Mol Endocrinol. 2004 Mar;18(3):606-23
references.pmid: 14701940
references.citation: J Biol Chem. 2004 Jan 2;279(1):152-62
references.pmid: 14570911
references.citation: J Biol Chem. 2009 Dec 18;284(51):35746-57
references.pmid: 19858197
references.citation: Mol Cell Endocrinol. 2001 Oct 25;183(1-2):29-32
references.pmid: 11604221
references.citation: Proc Natl Acad Sci U S A. 1995 Mar 14;92(6):1886-90
references.pmid: 7892195
references.citation: Science. 1996 Aug 30;273(5279):1219-21
references.pmid: 8703054
references.citation: Nature. 2005 Sep 22;437(7058):569-73
references.pmid: 16177793
references.citation: Mol Endocrinol. 2001 Mar;15(3):429-40
references.pmid: 11222744
references.citation: J Biol Chem. 2006 Aug 18;281(33):23999-4014
references.pmid: 16754659
references.citation: Endocrinology. 1999 May;140(5):2241-51
references.pmid: 10218977
references.citation: Endocrinology. 2004 Aug;145(8):3594-602
references.pmid: 15059960
references.citation: Arch Med Res. 2001 Nov-Dec;32(6):499-509
references.pmid: 11750725
references.citation: J Biol Chem. 2000 Mar 31;275(13):9193-200
references.pmid: 10734055
references.citation: Proc Natl Acad Sci U S A. 2005 Dec 20;102(51):18706-11
references.pmid: 16352729
references.citation: J Biol Chem. 2006 Nov 3;281(44):33345-51
references.pmid: 16963443
references.citation: Biochim Biophys Acta. 2007 Dec;1768(12):3001-11
references.pmid: 17996724
references.citation: Endocr Rev. 1997 Feb;18(1):46-70
references.pmid: 9034786
references.citation: Biol Reprod. 2007 Dec;77(6):1073-80
references.pmid: 17699734
references.citation: Mol Endocrinol. 2007 May;21(5):1175-91
references.pmid: 17299135
references.citation: J Bone Miner Res. 2010 Apr;25(4):819-29
references.pmid: 19821778
references.citation: J Biol Chem. 2002 Aug 30;277(35):32099-108
references.pmid: 12050161
references.citation: J Cell Biol. 2003 Jun 9;161(5):899-909
references.pmid: 12782683
references.citation: Nature. 1989 Aug 31;340(6236):692-6
references.pmid: 2549426
references.citation: Biochem J. 1997 Sep 15;326 ( Pt 3):701-7
references.pmid: 9307019
references.citation: PLoS One. 2008 Mar 19;3(3):e1796
references.pmid: 18350138
references.citation: Endocrinology. 2003 Oct;144(10):4354-65
references.pmid: 12960037