Lee WY, Wang CJ, Lin TY, Hsiao CL, Luo CW. CXCL17, an orphan chemokine, acts as a novel angiogenic and anti-inflammatory factor. Am J Physiol Endocrinol Metab 304: E32-E40, 2013. First published October 31, 2012; doi:10.1152/ajpendo.00083.2012.-Chemokines play pivotal roles in the recruitment of various immune cells to diverse tissues in both physiological and pathological conditions. CXCL17 is an orphan chemokine preliminarily found to be involved in tumor angiogenesis. However, its protein nature, as well as its endogenous bioactivity, has not been well clarified. Using real-time PCR, immunohistochemical staining, and Western blotting, we found that CXCL17 is highly expressed in both a constitutive and inducible manner in the rat gastric mucosa, where it undergoes endoproteolysis during protein maturation. The mature CXCL17 exhibited strong chemoattractant abilities targeting monocytes and macrophages, potentially through ERK1/2 and p38 but not JNK signaling. CXCL17 also induced the production of proangiogenic factors such as vascular endothelial growth factor A from treated monocytes. Furthermore, in contrast to other CXC chemokines that accelerate inflammatory responses, CXCL17 showed novel anti-inflammatory effects on LPS-activated macrophages. Therefore, our data suggest that CXCL17 in the gastric lamina propria may play an important role in tissue repair and anti-inflammation, both of which help to maintain the integrity of the gastric mucosa. endoproteolysis; macrophages; stomach CHEMOKINES ARE A GROUP OF CHEMOTACTIC CYTOKINES that govern the recruitment of various leukocytes to inflammation sites. In addition to promoting the trafficking of leukocytes, recent studies indicate that chemokines also play important roles in many aspects, including tumor growth, angiogenesis, organ sclerosis, and autoimmunity (21). Based on sequence homology and the numbers of amino acids between the first two cysteines, chemokines can be subdivided into C, CC, CXC, and CX 3 C subgroups (15). Chemokines bind to G protein-coupled receptors (GPCRs) on different target cells to initiate intracellular signaling cascades. Although the physiological roles and cognate receptors of most chemokines have been well characterized (34), the endogenous function as well as the receptor nature of CXCL17, the most recent chemokine ligand to be reported (17), are still unclear.CXCL17 was originally identified in 2006 by threading methods as having a protein structure similar to the CXC chemokine family (17). Although its physiological functions have not been clearly explored, two studies have proposed that CXCL17 might act as a chemokine that accelerates tumor progression (13,30). Overexpression of CXCL17 in NIH3T3 or hepatocellular carcinoma cells significantly promotes their tumor formation capability in nude mice. Microarray analyses have indicated that the CXCL17 transcript is elevated dramatically in breast and colon tumors, where its level is tightly coregulated in concert with vascular endothelial growth factor (VEGF) expression. Becau...

Neuromedin U (NMU) activates two G protein-coupled receptors, NMUR1 and NMUR2; this signaling not only controls many physiological responses but also promotes tumorigenesis in diverse tissues. We recently identified a novel truncated NMUR2 derived by alternative splicing, namely NMUR2S, from human ovarian cancer cDNA. Sequence analysis, cell surface ELISA and immunocytochemical staining using 293T cells indicated that NMUR2S can be expressed well on the cell surface as a six-transmembrane protein. Receptor pull-down and fluorescent resonance energy transfer assays demonstrated that NMUR1, NMUR2 and this newly discovered NMUR2S can not only form homomeric complexes but also heteromeric complexes with each other. Although not activated by NMU itself, functional assay in combination with receptor quantification and radio-ligand binding in 293T cells indicated that NMUR2S does not alter the translocation and stability of NMUR1 or NMUR2, but rather effectively dampens their signaling by blocking their NMU binding capability through receptor heterodimerization. We further demonstrated that NMU signaling is significantly up-regulated in human ovarian cancers, whereas expression of NMUR2S can block endogenous NMU signaling and further lead to suppression of proliferation in SKOV-3 ovarian cancer cells. In contrast, in monocytic THP-1 cells that express comparable levels of NMUR1 and NMUR2S, depletion of NMUR2S restored both the signaling and effect of NMU. Thus, these results not only reveal the presence of previously uncharacterized heteromeric relationships among NMU receptors but also provide NMUR2S as a potential therapeutic target for the future treatment of NMU signaling-mediated cancers.

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 ...