Open AccessRole of the cAMP signaling pathway in the regulation of gonadotropin-releasing hormone secretion in GT1 cells
Author(s) -
Elizabeth Vitalis,
James L. Costantin,
PeiSan Tsai,
Hideya Sakakibara,
Sreenivasan Paruthiyil,
Taroh Iiri,
Jean-François Martini,
Michiyoshi Taga,
Amy L. H. Choi,
Andrew Charles,
Richard I. Weiner
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.040545197
Subject(s) - adenylyl cyclase , camp dependent pathway , protein kinase a , endocrinology , gonadotropin releasing hormone , medicine , stimulation , secretion , g protein , biology , chemistry , signal transduction , gs alpha subunit , microbiology and biotechnology , hormone , phosphorylation , luteinizing hormone
We studied the signaling pathways coupling gonadotropin-releasing hormone (GnRH) secretion to elevations in cAMP levels in the GT1 GnRH-secreting neuronal cell line. We hypothesized that increased cAMP could be acting directly by means of cyclic nucleotide-gated (CNG) cation channels or indirectly by means of activation of cAMP-dependent protein kinase (PKA). We showed that GT1 cells express the three CNG subunits present in olfactory neurons (CNG2, -4.3, and -5) and exhibit functional cAMP-gated cation channels. Activation of PKA does not appear to be necessary for the stimulation of GnRH release by increased levels of cAMP. In fact, pharmacological inhibition of PKA activity caused an increase in the basal secretion of GnRH. Consistent with this observation activation PKA inhibited adenylyl cyclase activity, presumably by inhibiting adenylyl cyclase V expressed in the cells. Therefore, the stimulation of GnRH release by elevations in cAMP appears to be the result of depolarization of the neurons initiated by increased cation conductance by cAMP-gated cation channels. Activation of PKA may constitute a negative-feedback mechanisms for lowering cAMP levels. We hypothesize that these mechanisms could result in oscillations in cAMP levels, providing a biochemical basis for timing the pulsatile release of GnRH.