Promoter Usage and Estrogen Regulation of Prolactin Receptor Gene in the Brain of the Female Rat

Abstract

Mechanisms underlying hormonal regulation of prolactin receptor (PRL-R) gene in the brain are unknown. The 5’-untranslated region of PRL-R mRNA in peripheral tissues contains at least three alternative first exons (1A, B, C) that are expressed as tissue-specific, suggesting the differential usage of PRL-R gene promoters. The present study aimed to investigate: (1) the possible regulation of PRL-R mRNA levels by estrogen in in vitro and in vivo tissues; (2) which exon (1A, or 1B, or 1C)-containing PRL-R mRNA transcript is expressed in the brain, and (3) how the specific exon 1-containing mRNA is affected by estrogen by using RT-PCR, Southern blot and 5’Race PCR techniques. The RT-PCR results showed that PRL-R mRNA was detected in the cerebral cortex and pons medulla in addition to the choroid plexus and hypothalamus in the female rat. The expression of PRL-R mRNA was up-regulated by estrogen treatment in the rat brain tissue and in the GT1-7 cell culture. Both exon 1A- and 1C-containing transcripts were expressed in all four regions, suggesting that promoters 1A and 1C for the PRL-R gene are utilized in the rat brain. Exon 1A-containing transcript was up-regulated by estrogen treatment in all four brain regions, whereas Exon 1C-containing transcript was up-regulated by estrogen treatment in 3 of the 4 brain regions, cerebral cortex being the exception. Exon 1B-containing transcript was neither detectable nor induced by estrogen treatment in any of the brain regions examined. The RT-PCR results were confirmed by partial isolation of 5′-untranslated regions of exon 1A- and 1C-containing PRL-R mRNA transcripts from brain tissue by using 5’Race PCR. The present result confirms the expression of PRL-R mRNA in the cerebral cortex and pons medulla in the female rat. The levels of PRL-R mRNA were up-regulated by estrogen in rat brain tissue and GT1-7 cell cultures. Detection of exon 1A- and 1C-containing transcripts implies that the promoter 1A and 1C are active in the female rat brain. Estrogen differentially regulates expression of the PRL-R mRNA in the different brain regions by increasing the utilization of PRL-R gene promoters 1A and 1C in the female rat.

Characterization of multiple first exons in murine prolactin receptor gene and the effect of prolactin on their expression in the choroid plexus

“…These results indicate that PRL upregulates the expression of mE1 4 -Prlr mRNA in the murine choroid plexus and that the increased expression of mE1 3 -and mE1 5 -Prlr mRNAs at lactation may depend on factors other than PRL. It has been previously shown that estrogen upregulates Prlr gene expression in the choroid plexus (Pi et al 2003) as well as Prl gene expression in the pituitary gland (Shull & Gorski 1990, Kansra et al 2005. Our experiments in this study involving the ovariectomized mice showed that estrogen upregulates the expression of mE1 4 -Prlr mRNAs in the Prl C/K mice but not in the Prl K/K mice.…”

“…In addition, it has been reported that PRL enhances its own uptake in the choroid plexus (Mangurian et al 1992). Supporting this function, a high level of PRLR expression in the choroid plexus has been observed during lactation when the plasma PRL level is also high (Muccioli & Di Carlo 1994, Escalada et al 1996, Sugiyama et al 1996, Pi & Grattan 1999, Augustine et al 2003, Pi et al 2003, Nogami et al 2007, Anderson et al 2008. Also, PRLR expression in this brain region increases during the stress response, accompanying an increase in the plasma PRL level (Fujikawa et al 1995).…”

Regulation of Prolactin Receptor Gene Expression in the Rat Choroid Plexus via Transcriptional Activation of Multiple First Exons during Postnatal Development and Lactation

“…the long-form PrLr is known to be involved in most of the PrL functions mediated by the Jak2/stat5 (janus kinase 2/signal transducer and activator of transduction 5) intracellular signaling pathway [5,10,14], whereas the function and intracellular signaling system of the short-form PrLr is poorly understood. in the rat choroid plexus, the expression of the long-and short-form PRLR mrNas has been observed [3,4,15,27,30]. the molecular mechanisms of transcriptional activation of the E1 4 first exon, and the transport system of PrL mediated by long-or short-form PrLr in the choroid plexus remain to be elucidated.…”

“…PrL is known to be transported from the blood to the cerebrospinal fluid (CSF) via a PrLr-mediated system in the choroid plexus [37], and PrL enhances its own uptake in the choroid plexus [21]. Many studies have reported an increase in PRLR mrNa levels in the choroid plexus during lactation that correlate with plasma PrL level increases [1,2,13,24,27,30,31,33]. These findings suggest that regulation of PRLR expression in the choroid plexus is critical for PrL action in the brain.…”

Differential effects of sex steroid hormones on the expression of multiple first exons including a novel first exon of prolactin receptor gene in the rat liver

“…We have previously demonstrated that the higher levels of PRL-R mRNA in the rat brain in late pregnancy and the following lactating period are dependent on the expression of E1 4 , Tanaka et al 2002. It has also been shown that the expression levels of PRL-R mRNA in the different brain regions are regulated by oestrogen, which increases the utilization of E1 2 and E1 3 first exons (Pi et al 2003). In the liver, the expression of the PRL-R gene is known to be regulated by sex steroid hormones; up-regulation by oestrogen and down-regulation by testosterone (Jolicoeur et al 1989, Sakaguchi et al 1994.…”