Lhcgr expression in granulosa cells: roles for PKA-phosphorylated β-catenin, TCF3, and FOXO1

Mol Endocrinol. 2013 Aug;27(8):1295-310. doi: 10.1210/me.2013-1025. Epub 2013 Jun 10.

Abstract

Ovarian follicles lacking FSH or FSH receptors fail to progress to a preovulatory stage, resulting in infertility. One hallmark of the preovulatory follicle is the presence of luteinizing hormone/choriogonadotropin receptors (LHCGR) on granulosa cells (GCs). However, the mechanisms by which FSH induces Lhcgr gene expression are poorly understood. Our results show that protein kinase A (PKA) and phosphoinositide 3-kinase (PI3K)/AKT pathways are required for FSH to activate both the murine Lhcgr-luciferase reporter and expression of Lhcgr mRNA in rat GCs. Based on results showing that an adenovirus (Ad) expressing a steroidogenic factor 1 (SF1) mutant that cannot bind β-catenin abolished FSH-induced Lhcgr mRNA, we evaluated the role of β-catenin in the regulation of Lhcgr gene expression. FSH promoted the PKA-dependent, PI3K-independent phosphorylation of β-catenin on Ser552 and Ser665. FSH activated the β-catenin/T-cell factor (TCF) artificial promoter-reporter TOPFlash via a PKA-dependent, PI3K-independent pathway, and dominant-negative (DN) TCF abolished FSH-activated Lhcgr-luciferase reporter and induction of Lhcgr mRNA. Microarray analysis of GCs treated with Ad-DN-TCF and FSH identified the Lhcgr as the most down-regulated gene. Chromatin immunoprecipitation results placed β-catenin phosphorylated on Ser552 and Ser675 and SF1 on the Lhcgr promoter in FSH-treated GCs; TCF3 was constitutively associated with the Lhcgr promoter. Transduction with an Ad-phospho-β-catenin mutant (Ser552/665/Asp) enhanced Lhcgr mRNA expression in FSH-treated cells greater than 3-fold. Finally, we identified a recognized PI3K/AKT target, forkhead box O1, as a negative regulator of Lhcgr mRNA expression. These results provide new understanding of the complex regulation of Lhcgr gene expression in GCs.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Down-Regulation
  • Female
  • Follicle Stimulating Hormone / metabolism
  • Forkhead Transcription Factors / metabolism
  • Gene Expression Regulation
  • Granulosa Cells / metabolism*
  • Nerve Tissue Proteins / metabolism
  • Ovarian Follicle / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Messenger / biosynthesis
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Gonadotropin / biosynthesis
  • Receptors, Gonadotropin / genetics
  • Receptors, Gonadotropin / metabolism*
  • Receptors, LH / biosynthesis
  • Receptors, LH / genetics
  • Receptors, LH / metabolism*
  • Signal Transduction
  • Steroidogenic Factor 1 / genetics
  • Steroidogenic Factor 1 / metabolism
  • Transcription Factor 7-Like 1 Protein / metabolism
  • Transfection
  • beta Catenin / metabolism

Substances

  • Forkhead Transcription Factors
  • Nerve Tissue Proteins
  • RNA, Messenger
  • Receptors, Gonadotropin
  • Receptors, LH
  • Steroidogenic Factor 1
  • Transcription Factor 7-Like 1 Protein
  • beta Catenin
  • Foxo1 protein, rat
  • Follicle Stimulating Hormone
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt
  • Cyclic AMP-Dependent Protein Kinases