Gonadotropin-Releasing Hormone (GnRH) Positively Regulates Corticotropin-Releasing Hormone-Binding Protein Expression via Multiple Intracellular Signaling Pathways and a Multipartite GnRH Response Element in αT3-1 Cells

Autor: Audrey F. Seasholtz, Nicole J. Westphal
Rok vydání: 2005
Předmět:
endocrine system
medicine.medical_specialty
Molecular Sequence Data
Gonadotropin-releasing hormone
Mitogen-activated protein kinase kinase
Biology
Response Elements
Gonadotropic cell
Gonadotropin-Releasing Hormone
Mice
Endocrinology
Anterior pituitary
Internal medicine
Basic Helix-Loop-Helix Transcription Factors
polycyclic compounds
medicine
Animals
RNA
Messenger
Nuclear protein
Promoter Regions
Genetic
Protein kinase A
Molecular Biology
Cells
Cultured
Mitogen-Activated Protein Kinase Kinases
Binding Sites
Activating Transcription Factor 2
Base Sequence
Nuclear Proteins
General Medicine
Cyclic AMP-Dependent Protein Kinases
Up-Regulation
medicine.anatomical_structure
Gene Expression Regulation
nervous system
Pituitary Gland
Corticotropic cell
Signal transduction
Carrier Proteins
hormones
hormone substitutes
and hormone antagonists
Signal Transduction
Zdroj: Molecular Endocrinology. 19:2780-2797
ISSN: 1944-9917
0888-8809
DOI: 10.1210/me.2004-0519
Popis: 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.
Databáze: OpenAIRE
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