Menon B, Gulappa T, Menon KMJ. miR-122 Regulates LH Receptor Expression by Activating Sterol Response Element Binding Protein in Rat Ovaries. Endocrinology. http://press.endocrine.org/doi/abs/10.1210/en.2015-1121
Luteinizing hormone (LH) receptor undergoes downregulation during preovulatory LH surge or in response to exposure to a supraphysiological concentration of its ligands through a post-transcriptional mechanism involving an RNA binding protein designated as LRBP.
miR-122, a short non-coding RNA has been shown to mediate the upregulation of LRBP.
In the present study, we show that inhibition of miR-122 using an LNA-conjugated antagomir suppressed hCG-induced upregulation of LRBP as well as its association with LHR mRNA, as analyzed by RNA electrophoretic mobility shift assay.
Most importantly, inhibition of miR-122 resulted in the abolishment of hCG-mediated LHR mRNA downregulation.
We also show that the transcription factor, Sterol Regulatory Element Binding Protein (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/PKA and ERK pathways, upstream activators of miR-122, abolished SREBP activation following hCG treatment.
SREBP-mediated regulation of LRBP expression is mediated by recruitment of LRBP promoter element to SREBP-1a, since ChIP 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 upregulation of LRBP mRNA and protein.
Fatostatin also inhibited LRBP-LHR mRNP complex formation and LHR downregulation.
These results conclusively show that miR-122 plays a regulatory role in LH/hCG-induced LHR mRNA downregulation by increasing LRBP expression through the activation of SREBP pathway.
Luteinizing hormone (LH) receptor undergoes downregulation during preovulatory LH surge or in response to exposure to a supraphysiological concentration of its ligands through a post-transcriptional mechanism involving an RNA binding protein designated as LRBP.
miR-122, a short non-coding RNA has been shown to mediate the upregulation of LRBP.
In the present study, we show that inhibition of miR-122 using an LNA-conjugated antagomir suppressed hCG-induced upregulation of LRBP as well as its association with LHR mRNA, as analyzed by RNA electrophoretic mobility shift assay.
Most importantly, inhibition of miR-122 resulted in the abolishment of hCG-mediated LHR mRNA downregulation.
We also show that the transcription factor, Sterol Regulatory Element Binding Protein (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/PKA and ERK pathways, upstream activators of miR-122, abolished SREBP activation following hCG treatment.
SREBP-mediated regulation of LRBP expression is mediated by recruitment of LRBP promoter element to SREBP-1a, since ChIP 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 upregulation of LRBP mRNA and protein.
Fatostatin also inhibited LRBP-LHR mRNP complex formation and LHR downregulation.
These results conclusively show that miR-122 plays a regulatory role in LH/hCG-induced LHR mRNA downregulation by increasing LRBP expression through the activation of SREBP pathway.
