Association of luteinizing hormone receptor (LHR) mRNA with its binding protein leads to decapping and degradation of the mRNA in the p bodies

Abstract

Luteinizing hormone receptor (LHR) undergoes downregulation during preovulatory LH surge through a post-transcriptional mechanism involving an RNA binding protein designated as LRBP. The present study examined the mechanism by which LRBP induces the degradation of LHR mRNA, specifically the role of decapping of LHR mRNA and the translocation of LRBP-bound LHR mRNA to degradative machinery. Immunoprecipitation of the complex with the 5’cap structure antibody followed by real time PCR analysis showed progressive loss of capped LHR mRNA during downregulation suggesting that LHR mRNA undergoes decapping prior to degradation. RNA immunoprecipitation (RIP) analysis confirmed dissociation of eIF4E from the cap structure, a step required for decapping. Furthermore, RIP analysis using antibody against the p body marker protein, DCP1A showed that LHR mRNA was associated with the p bodies, the cytoplasmic foci that contains RNA degradative enzymes and decapping complex. Immunohistochemical studies using antibodies against LRBP and DCP1A followed by confocal analysis showed colocalization of LRBP with DCP1A during downregulation. This was further confirmed by co-immunoprecipitation of LRBP with DCP1A. The association of LRBP and LHR mRNA in the p bodies during downregulation was further confirmed by examining the association of a second p body component, rck/p54, using IP and RIP, respectively. These data suggest that the association of LRBP with LHR mRNA results in the translocation of the mRNP complex to the p bodies leading to decapping and degradation.

Molecular regulation of LHCGR expression by miR-122 during follicle growth in the rat ovary

“…The active SREBP translocates to the nucleus and activates transcription of target genes, including LRBP, by binding to sterol response elements (SREs) in the promoter/enhancer regions of multiple target genes. LRBP then binds LHCGR mRNA and targets it for degradation [12]. Based on the present results combined with those of previous studies, a schematic model that depicts the molecular mechanism illustrating the role of miR-122 in FSH-induced LHCGR mRNA expression is presented in Fig 6.…”

“…Biochemical characterization of LRBP established its identity as being mevalonate kinase (MVK) [8, 9]. LHCGR mRNA and LRBP expression show a reciprocal relationship at different stages of the ovarian cycle since at elevated levels of LHCGR expression, LRBP expression showed a decrease, whereas higher levels of LRBP were seen in response to the preovulatory LH surge, when LHCGR expression is transiently suppressed [12]. Further studies demonstrated that LRBP (MVK), a member of the oxysterol-responsive gene family, is regulated by miR-122, a microRNA that is expressed in the liver as well as in rodent and human ovaries [10, 11].…”

“…MiR-122, in turn, activates SREBPs, leading to an increase in the expression of LRBP [10]. LRBP then binds to LHCGR mRNA and targets it for degradation in the p bodies by interacting with other cytosolic proteins [12]. Our previous studies have shown that an increase in the expression of miR-122 leads to increased LRBP expression, resulting in LHCGR mRNA downregulation in response to the preovulatory LH surge [10, 11].…”

Impact of RNA structure on ZFP36L2 interaction with luteinizing hormone receptor mRNA

“…Degradation of the LHR mRNA is the main process responsible for this rapid decrease in expression (Lu et al 1993). The mechanism of LHR transcript decay is not fully understood, but at least one protein, LHR mRNA binding protein (LRBP), binds to this transcript and accelerates its degradation (Hoffman et al 1991;Menon et al 2013).…”