miR-122 Regulates LH Receptor Expression by Activating Sterol Response Element Binding Protein in Rat Ovaries

Endocrinology. 2015 Sep;156(9):3370-80. doi: 10.1210/en.2015-1121. Epub 2015 Jun 30.

Abstract

LH/human chorionic gonadotropin receptor (LHR) undergoes down-regulation during preovulatory LH surge or in response to exposure to a supraphysiological concentration of its ligands through a posttranscriptional mechanism involving an RNA binding protein designated as LHR mRNA binding protein (LRBP). miR-122, a short noncoding RNA, has been shown to mediate the up-regulation of LRBP. In the present study, we show that inhibition of miR-122 using a locked nucleic acid (LNA)-conjugated antagomir suppressed human chorionic gonadotropin (hCG)-induced up-regulation of LRBP as well as its association with LHR mRNA, as analyzed by RNA EMSA. Most importantly, inhibition of miR-122 resulted in the abolishment of hCG-mediated LHR mRNA down-regulation. We also show that the transcription factor, sterol regulatory element binding protein (SREBP) (SREBP-1a and SREBP-2 isoforms), is an intermediate in miR-122-mediated LHR mRNA regulation. HCG-stimulated increase in the activation of both SREBP-1a and SREBP-2 was inhibited by pretreatment with the miR-122 antagomir. The inhibition of cAMP/protein kinase A (PKA) and ERK pathways, upstream activators of miR-122, abolished SREBP activation after hCG treatment. SREBP-mediated regulation of LRBP expression is mediated by recruitment of LRBP promoter element to SREBP-1a, because chromatin immunoprecipitation assay revealed that association of LRBP promoter to SREBP was increased by hCG treatment. Pretreatment with miR-122 antagomir suppressed this response. Inhibition of SREBP activation by pretreating the rats with a chemical compound, fatostatin abrogated hCG-induced up-regulation of LRBP mRNA and protein. Fatostatin also inhibited LHR-LRBP mRNA-protein complex formation and LHR down-regulation. These results conclusively show that miR-122 plays a regulatory role in LH/hCG-induced LHR mRNA down-regulation by increasing LRBP expression through the activation of SREBP pathway.

Publication types

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

MeSH terms

  • Animals
  • Antagomirs
  • Chorionic Gonadotropin
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Female
  • Gene Expression Regulation
  • MAP Kinase Signaling System
  • MicroRNAs / metabolism*
  • Oligonucleotides
  • Ovary / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor)
  • Pyridines
  • RNA-Binding Proteins / metabolism
  • Rats, Sprague-Dawley
  • Receptors, LH / metabolism*
  • Ribonucleoproteins / metabolism
  • Sterol Regulatory Element Binding Proteins / metabolism*
  • Thiazoles

Substances

  • Antagomirs
  • Chorionic Gonadotropin
  • MIRN122 microRNA, rat
  • MicroRNAs
  • Oligonucleotides
  • Pyridines
  • RNA-Binding Proteins
  • Receptors, LH
  • Ribonucleoproteins
  • Sterol Regulatory Element Binding Proteins
  • Thiazoles
  • antagomir-122
  • fatostatin
  • messenger ribonucleoprotein
  • Cyclic AMP
  • Phosphotransferases (Alcohol Group Acceptor)
  • mevalonate kinase
  • Cyclic AMP-Dependent Protein Kinases