Ovarian regulation of neuromedin U and its local actions in the ovary, mediated through neuromedin U receptor 2

Abstract

Lin TY, Wu FJ, Lee WY, Hsiao CL, Luo CW. Ovarian regulation of neuromedin U and its local actions in the ovary, mediated through neuromedin U receptor 2. Am J Physiol Endocrinol Metab 304: E800-E809, 2013. First published February 19, 2013 doi:10.1152/ajpendo.00548.2012.-Neuromedin U (NMU) was originally identified as an anorexigenic peptide that modulates appetite as well as energy homeostasis through the brain-gut axis. Although growing evidence has linked NMU activity with the development of female reproductive organs, no direct expression of and function for NMU in these organs has been pinpointed. Using a superovulated rat model, we found that NMU is directly expressed in the ovary, where its transcript level is tightly regulated by gonadotropins. Ovarian microdissection and immunohistochemical staining showed clearly that NMU is expressed mainly in theca/interstitial cells and to a moderate extent in granulosa cells. Primary cell studies together with reporter assays indicated the Nmu mRNA level in these cells is strongly induced via cAMP signaling, whereas this increase in expression can be reversed by the degradation message residing within its 3=-untranslated region, which recruits cis-acting mRNA degradation mechanisms, such as the gonadotropininduced zinc finger RNA-binding protein Zfp36l1. This study also demonstrated that NMUR2, but not NMUR1, is the dominant NMU receptor in the ovary, where its expression is restricted to theca/ interstitial cells. Treatment with NMU led to induction of the early response c-Fos gene, phosphorylation of extracellular signal-regulated kinase 1/2, and promotion of progesterone production in both developing and mature theca/interstitial cells. Taken as a whole, this study demonstrates that NMU and NMU receptor 2 compose a novel autocrine system in theca/interstitial cells in which the intensity of signaling is tightly controlled by gonadotropins. adenosine 3=,5=-cyclic monophosphate; theca/interstitial cells NEUROMEDIN U (NMU) is a neuropeptide first isolated from the porcine spinal cord and was named based on its strong ability to cause uterine muscle contraction (31). Following its initial isolation, NMU has been subsequently identified in rats (7, 30), frogs (9), chickens (33), humans (2), and other vertebrates (5) with a diverse length due to there being different locations for its endoproteolytic sites in each propeptide. Despite this, mature NMU peptides across species display a remarkable amino acid identity in their COOH-terminal pentapeptide (Phe-ArgPro-Arg-Asn-NH 2 ), suggesting that this region is important to receptor binding and biological activity (37).NMU has not been detected in circulating blood, and therefore it has been proposed to act more as a local regulator than as a circulating hormone (8). Distribution of NMU was later reported to be ubiquitous, with higher expression in the pituitary gland, gastrointestinal tract, thyroid gland, ovary, and spinal cord (8,11). In contrast to this wide distribution, the two NMU receptors, NMUR1 and NMUR2, show ...

Identifying a Neuromedin U Receptor 2 Splice Variant and Determining Its Roles in the Regulation of Signaling and Tumorigenesis In Vitro

“…In addition to cell-based experiments, we also wanted to further explore whether the expression of NMUR2S can interfere in NMU signaling endogenously. We have previously demonstrated the existence of NMU signaling in the mammalian ovary [ 18 ]. Following this, we further found the transcripts of NMU and NMUR2 are significantly induced in the ovarian cancer tissues; this increase was by 941 folds and 5 folds, respectively on average compared to those in the adjacent normal controls ( Fig 7 ).…”

“…We have previously demonstrated the existence of NMU signaling in the rat ovary, where NMU and NMUR2 compose a novel autocrine system that controls ovarian cell development as well as progesterone production [ 18 ]. Therefore, we further tried to clarify whether the splice variant NMUR2S also exists in rats or other mammals.…”

“…The antigens on 5 μm-thick sections were retrieved by Target Retrieval Solution, pH 9 (DAKO). For the performance of immunohistochmeistry, the rabbit polyclonal anti-NMU antiserum was prepared as previously described [ 18 ] and the rabbit polyclonal anti-NMUR2 antibody (Abcam) was used. The rabbit preimmune serum and the normal IgG (Cell Signaling) at the same concentration were used as negative controls, respectively.…”

“…NMUR1 is expressed in diverse peripheral organs with relatively high levels in the small intestines and lung [ 14 ], where NMU signaling has a role in stimulating smooth muscle contraction and controlling blood pressure [ 15 ]. In contrast, NMUR2 is predominantly expressed in the central nervous system, such as the hypothalamus, and also the female ovary and uterus [ 16 ]; in this case NMU signaling can play important roles in controlling energy expenditure and reproductive development [ 13 , 17 , 18 ]. Nevertheless, both receptors have also been found to be co-expressed in many organs [ 19 – 21 ], where their functions have not yet been well characterized.…”

Neuromedin U: A Multifunctional Neuropeptide with Pleiotropic Roles

“…The relevance of NmU in sex hormone-related phenomena is confirmed by the fact that NmU expression varies from infancy through puberty and adulthood and along the female cycle, modulated by ovarian steroids (105 ); NmU receptor expression has also been shown to be estrogen dependent (106 ). Furthermore, NmU treatment induced ERK activation and progesterone release mediated by NMUR2 in cultured theca/interstitial cells of the ovary (107 ).…”