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Melanocortin Receptors (melanocortin + receptor)
Selected AbstractsCell Signaling and Trafficking of Human Melanocortin Receptors in Real Time Using Two-photon Fluorescence and Confocal Laser Microscopy: Differentiation of Agonists and AntagonistsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2006Minying Cai Melanocortin hormones and neurotransmitters regulate a vast array of physiologic processes by interacting with five G-protein-coupled melanocortin receptor types. In the present study, we have systematically studied the regulation of individual human melanocortin receptor wild subtypes using a synthetic rhodamine-labeled human melanotropin agonist and antagonist, arrestins fused to green fluorescent protein in conjunction with two-photon fluorescence laser scanning microscopy and confocal microscopy. Stimulation of the melanocortin receptors by its cognate agonist triggered rapid arrestin recruitment and receptor internalization for all four human melanocortin receptors examined. Antagonists-bound melanocortin receptors, on the other hand, did not recruit , -arrestins, and remained in the cell membrane even after long-term (30 min) treatment. Agonist-mediated internalization of all melanocortin receptor subtypes was sensitive to inhibitors of clathrin-dependent endocytosis, but not to caveolae inhibitors. In summary, agonist-mediated internalization of all subtypes of melanocortin receptors are dependent upon ,-arrestin-mediated clathrin-coated pits, whereas, ,-arrestin-2 conjugated green fluorescence protein (,-arrestin-2-GFP) recruitment is not dependent on protein kinase A activation. Real time two-photon fluorescence laser scanning microscopy is a most powerful tool to study the dynamic processes in living cells and tissues, without inflicting significant and often lethal damage to the specimen. [source] The melanocortin system in articular chondrocytes: Melanocortin receptors, pro-opiomelanocortin, precursor proteases, and a regulatory effect of ,-melanocyte,stimulating hormone on proinflammatory cytokines and extracellular matrix componentsARTHRITIS & RHEUMATISM, Issue 10 2009Susanne Grässel Objective The pro-opiomelanocortin (POMC),derived neuropeptide ,-melanocyte,stimulating hormone (,-MSH) mediates its effects via melanocortin (MC) receptors. This study was carried out to investigate the expression patterns of the MC system and the effects of ,-MSH in human articular chondrocytes. Methods Articular chondrocytes established from human osteoarthritic joint cartilage were analyzed by reverse transcription,polymerase chain reaction (RT-PCR) and Western blotting for the expression of MC receptors, POMC, and prohormone convertases (PCs). MC-1 receptor (MC-1R) expression in articular cartilage was further studied by immunohistochemistry. Ca2+ and cAMP assays were used to monitor ,-MSH signaling, while studies of ,-MSH function were performed in cultures with chondrocyte micromass pellets stimulated with ,-MSH. Expression of cytokines and extracellular matrix (ECM) components was determined by real-time RT-PCR, Western immunoblotting, and enzyme-linked immunosorbent assays. Results MC-1R expression was detected in articular chondrocytes in vitro and in articular cartilage in situ. In addition, expression of transcripts for MC-2R, MC-5R, POMC, and PCs was detected in articular chondrocytes. Stimulation with ,-MSH increased the levels of intracellular cAMP, but not Ca2+, in chondrocytes. Both messenger RNA and protein expression of various proinflammatory cytokines, collagens, matrix metalloproteinases (MMPs), and SOX9 was modulated by ,-MSH. Conclusion Human articular chondrocytes are target cells for ,-MSH. The effects of ,-MSH on expression of cytokines and MMPs suggest that this neuropeptide plays a role in inflammatory and degenerative processes in cartilage. It is conceivable that inflammatory reactions can be mitigated by the induction of endogenous MCs or administration of ,-MSH to the affected joints. The induction pattern of regulatory and structural ECM components such as collagens as well as SOX9 and anabolic and catabolic cytokines points to a function of ,-MSH as a trophic factor in skeletal development during endochondral ossification rather than as a factor in homeostasis of permanent cartilage. [source] Molecular variation in pigmentation genes contributing to coat colour in native Korean Hanwoo cattleANIMAL GENETICS, Issue 5 2008T. R. Mohanty Summary Pigmentation genes such as TYR (tyrosinase), TYRP1 (tyrosinase-related protein 1), DCT (previously TYRP2, or tyrosinase-related protein 2), ASIP (agouti) and MC1R (melanocortin receptor 1) play a major role in cattle coat colour. To understand the genotypic profile underlying coat colour in native Korean Hanwoo cattle and Angus black cattle, portions of the above-mentioned genes were amplified. Sequence analysis revealed variation in the TYRP1 (exon 5) and MC1R genes. Restriction enzyme analysis of these two genes could distinguish between different colours of Hanwoo cattle. Quantitative estimates of melanin and eumelanin in hair from three different-coloured Hanwoo phenotypes and Angus black showed significant differences at the breed and phenotypic levels. Finally, sequence variants in MC1R were associated with total melanin and eumelanin in breeds as well as in Hanwoo phenotypes. [source] Bovine melanocortin receptor 4: cDNA sequence, polymorphisms and mappingANIMAL GENETICS, Issue 4 2001A. Haegeman A cDNA encoding the bovine melanocortin receptor 4 (MC4R) was cloned and sequenced. Comparing human, pig and rat homologues showed a 87, 85 and 89% identity on the DNA level, respectively, and over 90% on the protein level. The bovine MC4R gene was mapped to BTU 24 by radiation hybrid mapping. Two nucleotide changes were identified by single stranded conformation polymorphism (SSCP) and sequencing. The substitutions proved to be a T to C and G (allele B) to A (allele A) resulting, respectively, in a conservative valine to alanine substitution (Val 145 Ala) and an alanine to threonine (Ala 172 Thr). Using PCR-RFLP, 13 different cattle breeds were screened for the presence of the Ala 172 Thr substitution. With the exception of one Red Pied animal, allele A could only be detected in Red Holstein animals. [source] The human basophil , a novel target of the neuropeptide alpha-melanocyte-stimulating hormoneEXPERIMENTAL DERMATOLOGY, Issue 8 2006M. Böhm There is increasing evidence that the basophil does not only play an important role in acute allergic reactions but also in the pathogenesis of chronic allergic disorders. Here we show that human basophils express melanocortin receptors (MC-Rs) and respond to alpha-melanocyte-stimulating hormone (alpha-MSH) with regulation of proallergic cytokine expression and modulation of basophil activation markers. Using primers against all known MC-R subtypes we demonstrate that the human basophil cell line KU812 expresses MC-1R. Expression of MC-1R on the surface of KU812 cells was confirmed by FACS analysis using an anti-MC-1R antibody. The MC-1R expressed by KU812 cells was functionally active as alpha-MSH induced intracellular cAMP in a dose-dependent manner. Moreover, alpha-MSH abrogated the effect of calcium ionophore A23187 on IL-4 mRNA expression in these cells. The relevance of the above findings was corroborated by showing that MC-1R surface expression is also detectable in basophils of leukocyte suspensions derived from whole human blood. Most interestingly, alpha-MSH was capable of suppressing the inductive effect of fMLP on surface expression of the basophil activation marker CD63 in leukocyte suspensions of atopic individuals. Likewise, alpha-MSH significantly blocked grass pollen-induced up-regulation of CD63 in leukocyte suspensions of patients with grass pollen allergy. Our findings highlight a novel functional dimension of alpha-MSH. In addition, MSH peptides may become a novel future therapeutic avenue in treating human allergic diseases. [source] Identification of novel genes regulated by ,-melanocyte-stimulating hormone in murine bone marrow-derived dendritic cellsEXPERIMENTAL DERMATOLOGY, Issue 9 2004T. Brzoska Many strains of evidence indicate that ,-melanocyte-stimulating hormone (,-MSH) elicits its immunomodulatory activity via binding to melanocortin receptors (MC-Rs) expressed on monocytes and dendritic cells. In order to identify novel target genes regulated by ,-MSH in these cells, we prepared bone marrow-derived dendritic cell precursors from BALB/c mice and treated them with GM-CSF and IL-4 for 6 days. The MC-R profile on these immature dendritic cells was first determined by quantitative RT-PCR. Both transcripts for MC-1R and MC-5R were detected in these cells. Cells were subsequently stimulated with dinitrobenzene sulfonic acid (DNBS), ,-MSH or both substances for 2 or 16 h. After RNA preparation, cDNA synthesis and in vitro transcripton hybridization of biotinylated cRNA samples was performed on MG U74A Affymetrix gene chips. Data evaluation, cleansing, extraction and analysis of the more than 12 000 cloned genes and expressed sequence tags were performed using the GENE DATA ANALYST vs. 1 Expressionist software. Filter criteria included a minimum threshold of 100, normalization by the logarithmic mean and a quality setting of P < 0.04. Changes with a change factor of >2 were regarded as significant. As expected, stimulation with DNBS resulted in induction or upregulation of genes encoding proinflammatory cytokines, growth factors, signal transduction intermediates and transcription factors. Treatment with ,-MSH blocked the DNBS-driven upregulation of several known genes such as IL-1 or CD86. On the other hand, ,-MSH modulated the expression of several novel genes implicated in immunomodulation, e.g. IL-1, converting enzyme, IFN-, receptor, FK506-binding proteins or several neuropeptides and their receptors. These data indicate novel molecular targets by which ,-MSH exerts its immunomodulatory activities in immunocompetent cells. [source] The Effect of Leptin on Luteinizing Hormone Release Is Exerted in the Zona Incerta and Mediated by Melanin-Concentrating HormoneJOURNAL OF NEUROENDOCRINOLOGY, Issue 11 2000J. F. Murray Abstract The adipose hormone, leptin, not only restrains appetite, but also influences energy expenditure. One such influence is to promote sexual maturation and fertility. The neuromodulatory circuits that mediate this effect are not well known but the present study suggests that one mediator could be melanin-concentrating hormone (MCH). We show that the long-form receptor (Ob-Rb) is expressed in the zona incerta of the rat and that administration of leptin (both 0.5 µg and 1.0 µg/side) into this area of ovariectomized, oestrogen-primed rats stimulated the release of luteinizing hormone (LH) within 1 h, the effect enduring for a further 1 h. Injections of leptin into the arcuate nucleus induced a smaller, transient rise in LH while injections into the paraventricular and ventromedial nuclei were without effect. MCH neurones are present in the zona incerta and administration of this hormone into the medial preoptic area (mPOA) stimulates LH release, therefore we investigated the possibility that MCH might mediate this effect of leptin. An injection of MCH antiserum into mPOA prevented the rise in LH normally induced by leptin injected into the zona incerta. In addition, melanocortin receptor antagonists ([D-Arg8]ACTH(4-10) and [Ala6]ACTH(4-10)), previously shown to inhibit the stimulatory effect of MCH on LH release, also inhibited the effect of leptin. We propose that one route by which leptin may promote reproductive activity is by enhancing MCH release from fibres within the mPOA. Speculative mechanisms for the action of MCH include the following possibilities: MCH may be acting on the specific MCH receptor which in turn interacts with a melanocortin or melanocortin-like receptor; MCH may bind directly to one of the melanocortin receptors; or melanocortin antagonists may interact with the MCH receptor. [source] Overlapping Peptide Control of Alcohol Self-Administration and FeedingALCOHOLISM, Issue 2 2004Todd E. Thiele Abstract: This article represents the proceedings of a symposium at the 2003 annual meeting of the Research Society on Alcoholism in Fort Lauderdale, FL. The organizers and chairpersons were Mark Egli and Todd E. Thiele. The presentations were (1) Voluntary alcohol consumption is modulated by central melanocortin receptors, by Todd E. Thiele; (2) Central infusion of neuropeptide Y reduces alcohol drinking in alcohol-preferring P rats, by Robert B. Stewart and Nancy E. Badia-Elder; (3) The gut peptide cholecystokinin controls alcohol intake in Sardinian alcohol-preferring rats, by Nori Geary and Maurizio Massi; and (4) Hypothalamic galanin: a possible role in excess alcohol drinking, by Sarah F. Leibowitz and Bartley G. Hoebel. [source] Current trends in the structure,activity relationship studies of the endogenous agouti-related protein (AGRP) melanocortin receptor antagonistMEDICINAL RESEARCH REVIEWS, Issue 5 2005Andrzej M. Wilczynski Abstract Agouti-related protein (AGRP) is an endogenous antagonist of the melanocortin-3 and -4 (MC3R and MC4) G-protein coupled receptors. The 87,132 amino acid C-terminal domain of hAGRP possesses five disulfide bridges and a well-defined three-dimensional structure that displays full biological activity as compared to the full-length protein. Based on the NMR structure of the C-terminal AGRP(87,132), a novel mini-protein, referred to as "Mini-AGRP" was designed that exhibited receptor binding affinity and antagonism similar to that of the parent hAGRP(87,132) protein. It was demonstrated that this new-engineered protein autonomously folds to the inhibitor cystine knot (ICK) motif. As this AGRP is a novel mammalian protein involved in energy homeostasis and possibly other physiological functions remaining to be identified, structure-function studies are starting to emerge toward the understanding of how this unique protein putatively interacts with the melanocortin receptors with the objective of designing potential therapeutic agents for in vivo physiological studies. This article summarizes the progress to date of AGRP-based structure,activity relationships and putative ligand,receptor interactions. © 2005 Wiley Periodicals, Inc. [source] Cell Signaling and Trafficking of Human Melanocortin Receptors in Real Time Using Two-photon Fluorescence and Confocal Laser Microscopy: Differentiation of Agonists and AntagonistsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2006Minying Cai Melanocortin hormones and neurotransmitters regulate a vast array of physiologic processes by interacting with five G-protein-coupled melanocortin receptor types. In the present study, we have systematically studied the regulation of individual human melanocortin receptor wild subtypes using a synthetic rhodamine-labeled human melanotropin agonist and antagonist, arrestins fused to green fluorescent protein in conjunction with two-photon fluorescence laser scanning microscopy and confocal microscopy. Stimulation of the melanocortin receptors by its cognate agonist triggered rapid arrestin recruitment and receptor internalization for all four human melanocortin receptors examined. Antagonists-bound melanocortin receptors, on the other hand, did not recruit , -arrestins, and remained in the cell membrane even after long-term (30 min) treatment. Agonist-mediated internalization of all melanocortin receptor subtypes was sensitive to inhibitors of clathrin-dependent endocytosis, but not to caveolae inhibitors. In summary, agonist-mediated internalization of all subtypes of melanocortin receptors are dependent upon ,-arrestin-mediated clathrin-coated pits, whereas, ,-arrestin-2 conjugated green fluorescence protein (,-arrestin-2-GFP) recruitment is not dependent on protein kinase A activation. Real time two-photon fluorescence laser scanning microscopy is a most powerful tool to study the dynamic processes in living cells and tissues, without inflicting significant and often lethal damage to the specimen. [source] Extensive structure,activity studies of lactam derivatives of MT-II and SHU-9119: their activity and selectivity at human melanocortin receptors 3, 4, and 5CHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2003P. Grieco Abstract: The melanocortin system is involved in the regulation of several diverse physiologic pathways. Recently we have demonstrated that replacing His6 by Pro6 in the well-known antagonist SHU-9119 resulted in a potent agonist at the hMC5R (EC50 = 0.072 nm) with full antagonist activity at the hMC3R and the hMC4R. We have designed, synthesized, and pharmacologically characterized a series of peptide analogs of MT-II and SHU-9119 at the human melanocortin receptors MC3R, MC4R and MC5R. All these peptides were modified at position 6 with a Pro instead of a His residue. In this study, we have identified new scaffolds which are antagonists at the hMC4R and hMC3R. Additionally, we have discovered a new selective agonist at the hMC4R, Ac-Nle-c[Asp-Pro-D-Phe-Arg-Trp-Lys]-Pro-Val-NH2 (6, PG-931) which will be useful in further biologic investigations of the hMC4R. PG-931 was about 100-fold more selective for the hMC4R vs. the hMC3R (IC50 = 0.58 and 55 nm, respectively). Some of these new analogs have exceptional biologic potencies at the hMC5R and will be useful in further efforts to differentiate the substructural features responsible for selectivity at the hMC3R, hMC4R, and hMC5R. [source] | |||||||||||||