Gonadotropin-releasing hormone (GnRH) positively regulates corticotropin-releasing hormone-binding protein expression via multiple intracellular signaling pathways and a multipartite GnRH response element in alphaT3-1 cells

Mol Endocrinol. 2005 Nov;19(11):2780-97. doi: 10.1210/me.2004-0519. Epub 2005 Jun 23.

Abstract

CRH-binding protein (CRH-BP) binds CRH with high affinity and inhibits CRH-mediated ACTH release from anterior pituitary corticotrope-like cells in vitro. In female mouse pituitary, CRH-BP is localized not only in corticotropes, but is also expressed in gonadotropes and lactotropes. To investigate the functional significance of gonadotrope CRH-BP, we examined the molecular mechanisms underlying GnRH-regulated CRH-BP expression in alphaT3-1 gonadotrope-like cells. CRH-BP is endogenously expressed in alphaT3-1 cells, and quantitative real-time RT-PCR and ribonuclease protection assays demonstrate that GnRH induces a 3.7-fold increase in CRH-BP mRNA levels. GnRH also induces intracellular CRH-BP (2.0-fold) and secreted CRH-BP (5.3-fold) levels, as measured by [125I]CRH:CRH-BP chemical cross-linking. Transient transfection assays using CRH-BP promoter-luciferase constructs indicate that GnRH regulation involves protein kinase C-, ERK- and calcium-dependent signaling pathways and is mediated via a multipartite GnRH response element that includes activator protein 1 and cAMP response element (CRE) sites. The CRE site significantly contributes to GnRH responsiveness, independent of protein kinase A, representing a unique form of multipartite GnRH regulation in alphaT3-1 cells. Furthermore, EMSAs indicate that alphaT3-1 nuclear proteins specifically bind at activator protein 1 and CRE sites. These data demonstrate novel regulation of pituitary CRH-BP, highlighting the importance of the pituitary gonadotrope as a potential interface between the stress and reproductive axes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Activating Transcription Factor 2 / metabolism
  • Animals
  • Base Sequence
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Binding Sites
  • Carrier Proteins / genetics*
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Gene Expression Regulation*
  • Gonadotropin-Releasing Hormone / metabolism
  • Gonadotropin-Releasing Hormone / pharmacology*
  • Mice
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Molecular Sequence Data
  • Nuclear Proteins / metabolism
  • Pituitary Gland / cytology
  • Pituitary Gland / metabolism
  • Promoter Regions, Genetic / drug effects
  • RNA, Messenger / analysis
  • RNA, Messenger / metabolism
  • Response Elements* / genetics
  • Signal Transduction
  • Up-Regulation

Substances

  • Activating Transcription Factor 2
  • Basic Helix-Loop-Helix Transcription Factors
  • Carrier Proteins
  • Nuclear Proteins
  • RNA, Messenger
  • Tcf3 protein, mouse
  • corticotropin releasing factor-binding protein
  • Gonadotropin-Releasing Hormone
  • Cyclic AMP-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase Kinases