title: miR-122 Regulates LH Receptor Expression by Activating Sterol Response Element Binding Protein in Rat Ovaries.
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.
authors.affiliation: Departments of Obstetrics/Gynecology and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0617.
authors.forename: Bindu
authors.initials: B
authors.lastname: Menon
authors.affiliation: Departments of Obstetrics/Gynecology and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0617.
authors.forename: Thippeswamy
authors.initials: T
authors.lastname: Gulappa
authors.affiliation: Departments of Obstetrics/Gynecology and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0617.
authors.forename: K M J
authors.initials: KM
authors.lastname: Menon
mesh_terms: D000818:Animals; D000070416:Antagomirs; D006063:Chorionic Gonadotropin; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D020935:MAP Kinase Signaling System; D035683:MicroRNAs / Q000378:metabolism*; D009841:Oligonucleotides; D010053:Ovary / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor); D011725:Pyridines; D016601:RNA-Binding Proteins / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D011974:Receptors, LH / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D051779:Sterol Regulatory Element Binding Proteins / Q000378:metabolism*; D013844:Thiazoles
chemical_list: D000070416:Antagomirs; D006063:Chorionic Gonadotropin; C580643:MIRN122 microRNA, rat; D035683:MicroRNAs; D009841:Oligonucleotides; D011725:Pyridines; D016601:RNA-Binding Proteins; D011974:Receptors, LH; D012261:Ribonucleoproteins; D051779:Sterol Regulatory Element Binding Proteins; D013844:Thiazoles; C520440:antagomir-122; C545733:fatostatin; C026452:messenger ribonucleoprotein; D000242:Cyclic AMP; D017853:Phosphotransferases (Alcohol Group Acceptor); C021796:mevalonate kinase; D017868:Cyclic AMP-Dependent Protein Kinases