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Sharon L Wardlaw - One of the best experts on this subject based on the ideXlab platform.
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diurnal patterns for cortisol cortisone and agouti related Protein in human cerebrospinal fluid and blood
The Journal of Clinical Endocrinology and Metabolism, 2020Co-Authors: Sunil K Panigrahi, Cristina D Toedesbusch, Jennifer S Mcleland, Brendan P Lucey, Sharon L WardlawAbstract:CONTEXT Cortisol in blood has a robust circadian rhythm and exerts potent effects on energy balance that are mediated in part by central mechanisms. These interactions involve orexigenic Agouti-Related Protein (AgRP) neurons that are stimulated by glucocorticoids. However, diurnal changes in brain or cerebrospinal fluid (CSF) cortisol and cortisone, which are interconverted by 11s-HSD1, have not been characterized in humans. OBJECTIVE To conduct a secondary analysis of existing samples to characterize diurnal changes in cortisol and cortisone in CSF and examine their relationships to changes in AgRP. METHODS Stored CSF and plasma samples were obtained from 8 healthy subjects who served as controls for a sleep study. CSF was collected every 2h for 36h via indwelling lumbar catheter; plasma was collected every 2h. RESULTS There was a diurnal rhythm for cortisol and cortisone in CSF that closely followed the plasma rhythm by 2 h with peak and nadir levels at 0900h and 0100h. The ratio of cortisol (active) to cortisone (inactive) in CSF was 48% higher at the peak versus nadir. There was a diurnal rhythm for AgRP in plasma that was out of phase with the cortisol rhythm. There was a less distinct diurnal rhythm for AgRP in CSF that oscillated with a similar phase as cortisol. CONCLUSIONS There is a robust diurnal rhythm for cortisol and cortisone in CSF. Diurnal changes were noted for AgRP that are related to the cortisol changes. It remains to be determined if AgRP mediates adverse metabolic effects associated with disruption of the cortisol circadian rhythm.
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plasma agouti related Protein levels in acromegaly and effects of surgical or pegvisomant therapy
The Journal of Clinical Endocrinology and Metabolism, 2019Co-Authors: Pamela U Freda, Sunil K Panigrahi, Jeffrey N Bruce, Carlos Reyesvidal, Zhezhen Jin, Mya Pugh, Sharon L WardlawAbstract:CONTEXT GH activates Agouti-Related Protein (AgRP) neurons, leading to orexigenic responses in mice. The relationship between serum GH and plasma AgRP, which has been shown to reflect hypothalamic AgRP, has not been evaluated in humans. OBJECTIVE To test the hypothesis that central stimulatory actions of GH on hypothalamic AgRP could be reflected in plasma AgRP in acromegaly. METHODS We studied 23 patients with active acromegaly before and for ≤2 years after surgical (n = 13) or GH receptor antagonist therapy with pegvisomant (n = 10), and 100 healthy subjects with morning fasting blood samples for AgRP, leptin, GH, and IGF-1 and anthropometric measurements. RESULTS The plasma AgRP levels were higher in those with active acromegaly than in the matched healthy subjects [median, 100 pg/mL; interquartile range (IQR), 78 to 139 pg/mL vs median, 63 pg/mL; IQR, 58 to 67 pg/mL; P < 0.0001]. Plasma AgRP decreased from before to after surgery (median, 102 pg/mL; IQR, 82 to 124 pg/mL vs median, 63 pg/mL; IQR, 55.6 to 83 pg/mL; P = 0.0024) and from before to during pegvisomant therapy (median, 97 pg/mL; IQR, 77 to 175 pg/mL vs median, 63; IQR, 61 to 109 pg/mL; P = 0.006). The plasma AgRP level correlated with GH (r = 0.319; P = 0.011) and IGF-1 (r = 0.292; P = 0.002). In repeated measure analysis, AgRP was significantly associated with IGF-1. CONCLUSIONS Our data have provided evidence of a stimulatory effect of GH on plasma AgRP in humans. The levels were greater in active acromegaly and decreased in parallel with GH and IGF-1 decreases with acromegaly treatment. Data from mice suggest that AgRP may mediate some of the known effects of GH on energy metabolism. This warrants further study in patients with acromegaly and other populations.
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plasma agouti related Protein and cortisol levels in cushing disease evidence for the regulation of agouti related Protein by glucocorticoids in humans
The Journal of Clinical Endocrinology and Metabolism, 2019Co-Authors: Gabrielle Pagewilson, Jane Peters, Sunil K Panigrahi, Thomas P Jacobs, Judith Korner, Marc L Otten, Jeffrey N Bruce, Sharon L WardlawAbstract:Context Glucocorticoids regulate energy balance, in part by stimulating the orexigenic neuropeptide Agouti-Related Protein (AgRP). AgRP neurons express glucocorticoid receptors, and glucocorticoids have been shown to stimulate AgRP gene expression in rodents. Objective We sought to determine whether there is a relationship between plasma AgRP and hypothalamic AgRP in rats and to evaluate the relationship between cortisol and plasma AgRP in humans. Methods We retrospectively evaluated plasma AgRP levels prior to transsphenoidal surgery in 31 patients with Cushing disease (CD) vs 31 sex- and body mass index-matched controls from a separate study. We then prospectively measured plasma AgRP, before and 6 to 12 months after surgery, in a subgroup of 13 patients with CD. Plasma and hypothalamic AgRP were measured in adrenalectomized rats with and without corticosterone replacement. Results Plasma AgRP was stimulated by corticosterone in rats and correlated with hypothalamic AgRP expression. Plasma AgRP levels were higher in patients with CD than in controls (139 ± 12.3 vs 54.2 ± 3.1 pg/mL; P < 0.0001). Among patients with CD, mean 24-hour urine free cortisol (UFC) levels were 257 ± 39 μg/24 hours. Strong positive correlations were observed between plasma AgRP and UFC (r = 0.76; P < 0.0001). In 11 of 13 patients demonstrating surgical cure, AgRP decreased from 126 ± 20.6 to 62.5 ± 8.0 pg/mL (P < 0.05) postoperatively, in parallel with a decline in UFC. Conclusions Plasma AgRP levels are elevated in CD, are tightly correlated with cortisol concentrations, and decline with surgical cure. These data support the regulation of AgRP by glucocorticoids in humans. AgRP's role as a potential biomarker and as a mediator of the adverse metabolic consequences of CD deserves further study.
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proopiomelanocortin agouti related Protein and leptin in human cerebrospinal fluid correlations with body weight and adiposity
American Journal of Physiology-endocrinology and Metabolism, 2015Co-Authors: Gabrielle Pagewilson, Kana Meece, Anne White, Michael Rosenbaum, Rudolph L Leibel, Richard M Smiley, Sharon L WardlawAbstract:Leptin and its neuronal targets, which produce proopiomelanocortin (POMC) and Agouti-Related Protein (AgRP), regulate energy balance. This study characterized leptin, POMC, and AgRP in the cerebros...
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Effects of Estradiol on Cerebrospinal Fluid Levels of Agouti-Related Protein in Ovariectomized Rhesus Monkeys
Endocrinology, 2010Co-Authors: Ennian Xiao, Andrea Kim, Roxanne Dutia, Irene M. Conwell, Michel Ferin, Sharon L WardlawAbstract:Hypothalamic proopiomelanocortin (POMC)-derived MSH peptides and the melanocortin receptor antagonist, Agouti-Related Protein (AgRP), interact to regulate energy balance. Both POMC and AgRP neurons express estrogen receptors, but little is known about estrogen regulation of the melanocortin system in the primate. We have therefore examined the effects of physiological doses of estradiol (E2) on POMC and AgRP in lumbar cerebrospinal fluid (CSF) of ovariectomized monkeys. POMC prohormone was measured by ELISA. AgRP was measured by RIA (sensitive for the more biologically active C-terminal AgRP83-132 but also detects full-length AgRP) and by ELISA (measures primarily full length AgRP). In the first experiment, 14 animals were studied before and after 3 wk of E2. CSF POMC did not change, but AgRP(RIA) decreased from 7.9 ± 1.2 to 4.7 ± 1.2 fmol/ml after E2 (P = 0.03) and the POMC/AgRP(RIA) ratio increased from 4.2 ± 0.89 to 6.8 ± 1.04 (P = 0.04). AgRP(ELISA) did not change, but the ratio of AgRP(RIA) compared ...
Carrie Haskellluevano - One of the best experts on this subject based on the ideXlab platform.
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incorporation of agouti related Protein agrp human single nucleotide polymorphisms snps in the agrp derived macrocyclic scaffold c pro arg phe phe asn ala phe dpro decreases melanocortin 4 receptor antagonist potency and results in the discovery of melanocortin 5 receptor antagonists
Journal of Medicinal Chemistry, 2020Co-Authors: Zoe M Koerperich, Mark D Ericson, Katie T Freeman, Robert C Speth, Irina D Pogozheva, Henry I Mosberg, Carrie HaskellluevanoAbstract:While the melanocortin receptors (MCRs) are known to be involved in numerous biological pathways, the potential roles of the MC5R have not been clearly elucidated in humans. Agouti-Related Protein ...
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a macrocyclic agouti related Protein nle4 dphe7 α melanocyte stimulating hormone chimeric scaffold produces subnanomolar melanocortin receptor ligands
Journal of Medicinal Chemistry, 2017Co-Authors: Mark D Ericson, Katie T Freeman, Sathya M Schnell, Carrie HaskellluevanoAbstract:The melanocortin system consists of five receptor subtypes, endogenous agonists, and naturally occurring antagonists. These receptors and ligands have been implicated in numerous biological pathways including processes linked to obesity and food intake. Herein, a truncation structure–activity relationship study of chimeric Agouti-Related Protein (AGRP)/[Nle4,DPhe7]α-melanocyte stimulating hormone (NDP-MSH) ligands is reported. The tetrapeptide His-DPhe-Arg-Trp or tripeptide DPhe-Arg-Trp replaced the Arg-Phe-Phe sequence in the AGRP active loop derivative c[Pro-Arg-Phe-Phe-Xxx-Ala-Phe-DPro], where Xxx was the native Asn of AGRP or a diaminopropionic (Dap) acid residue previously shown to increase antagonist potency at the mMC4R. The Phe, Ala, and Dap/Asn residues were successively removed to generate a 14-member library that was assayed for agonist activity at the mouse MC1R, MC3R, MC4R, and MC5R. Two compounds possessed nanomolar agonist potency at the mMC4R, c[Pro-His-DPhe-Arg-Trp-Asn-Ala-Phe-DPro] and c...
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pharmacological characterization of 40 human melanocortin 4 receptor polymorphisms with the endogenous proopiomelanocortin derived agonists and the agouti related Protein agrp antagonist
Biochemistry, 2006Co-Authors: Zhimin Xiang, Nicholas B Sorensen, Amanda M Shaw, William J Millard, Sally A Litherland, Bettina Proneth, Michael S Wood, Carrie HaskellluevanoAbstract:The melanocortin-4 receptor (MC4R) is a G-Protein coupled receptor (GPCR) that is expressed in the central nervous system and has a role in regulating energy homeostasis and obesity. Up to a remarkable 6% of morbidly obese adults and children studied possess single nucleotide polymorphisms (SNPs) of the MC4R. Upon stimulation by agonist, the MC4R signals through the intracellular adenylate cyclase signal transduction pathway. Posttranslational modification of the pro-opiomelanocortin (POMC) gene transcript results in the generation of several endogenous melanocortin receptor agonists including α-, β-, γ-melanocyte stimulating hormones (MSH) and adrenocorticotropin (ACTH) ligands. The endogenous MC4R antagonist, Agouti-Related Protein (AGRP), is expressed in the brain and is only one of two naturally occurring antagonists of GPCRs identified to date. Herein, we have generated 40 hMC4 polymorphic receptors and evaluated their cell surface expression by flow cytometry as well as pharmacologically characteriz...
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structure activity studies of the melanocortin 4 receptor by in vitro mutagenesis identification of agouti related Protein agrp melanocortin agonist and synthetic peptide antagonist interaction determinants
Biochemistry, 2001Co-Authors: Carrie Haskellluevano, Roger D. Cone, Eileen K. MonckAbstract:In vitro mutagenesis of the mouse melanocortin-4 receptor (mMC4R) has been performed, based upon homology molecular modeling and previous melanocortin receptor mutagenesis studies that identified putative ligand−receptor interactions. Twenty-three mMC4 receptor mutants were generated and pharmacologically characterized using several melanocortin-based ligands [α-MSH, NDP-MSH, MTII, dNal (1‘)7-MTII, Nal(2‘)7-MTII, SHU9119, and SHU9005]. Selected mutant receptors possessing significant differences in the melanocortin-based peptide agonist and/or antagonist pharmacology were further evaluated using the endogenous antagonist Agouti-Related Protein fragment hAGRP(83−132) and hAGRP(109−118) molecules. These studies of the mouse MC4R provide further experimental data suggesting that the conserved melanocortin receptor residues Glu92 (TM2), Asp114 (TM3), and Asp118 (TM3) (mouse MC4R numbering) are important for melanocortin-based peptide molecular recognition. Additionally, the Glu92 and Asp118 mMC4R residues are...
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characterization of the neuroanatomical distribution of agouti related Protein immunoreactivity in the rhesus monkey and the rat
Endocrinology, 1999Co-Authors: Carrie Haskellluevano, Peilin Chen, Kang Chang, Susan M Smith, Judy L Cameron, Roger D. ConeAbstract:Agouti-Related Protein (AGRP) is a recently described homolog of the skin agouti Protein. AGRP is transcribed primarily in the adrenal and hypothalamus and is a high affinity antagonist of the neural melanocortin-3 and melanocortin-4 receptors. The perikarya expressing AGRP messenger RNA are found in the arcuate nucleus of the rat and rhesus monkey. Using a polyclonal antibody against the pharmacologically active domain of AGRP (amino acids 83-132), we have also characterized the distribution of AGRP-immunoreactive neurons in both species. The major fiber tracts are conserved in both species, with dense projections originating in the arcuate nucleus and proceeding along the third ventricle. Dense fiber bundles are also visible in the paraventricular, dorsomedial, and posterior nuclei in the hypothalamus, in the bed nucleus of the stria terminalis, and in the lateral septal nucleus of the septal region. AGRP-containing neurons are not visualized in a number of areas, including portions of the amygdala, thalamus, and brain stem, that express MC3-R and MC4-R messenger RNA and receive innervation from POMC neurons that serve as the source of melanocortin agonists. Thus, AGRP is most likely to be involved in modulating a conserved subset of the physiological functions of central melanocortin peptides. Based on the particular distribution of AGRP neurons, those functions are likely to include the central control of energy homeostasis.
Gregory S. Barsh - One of the best experts on this subject based on the ideXlab platform.
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coordinated regulation of hepatic energy stores by leptin and hypothalamic agouti related Protein
The Journal of Neuroscience, 2013Co-Authors: James P Warne, Gregory S. Barsh, Christopher B Kaelin, Jillian M Varonin, Sofie S Nielsen, Louise E Olofsson, Streamson C Chua, Suneil K KoliwadAbstract:Like obesity, prolonged food deprivation induces severe hepatic steatosis; however, the functional significance of this phenomenon is not well understood. In this study, we show that the fall in plasma leptin concentration during fasting is required for the development of hepatic steatosis in mice. Removal of leptin receptors from AGRP neurons diminishes fasting-induced hepatic steatosis. Furthermore, the suppressive effects of leptin on fasting-induced hepatic steatosis are absent in mice lacking the gene encoding Agouti-Related Protein (Agrp), suggesting that this function of leptin is mediated by AGRP. Prolonged fasting leads to suppression of hepatic sympathetic activity, increased expression of acyl CoA:diacylglycerol acyltransferase-2 in the liver, and elevation of hepatic triglyceride content and all of these effects are blunted in the absence of AGRP. AGRP deficiency, despite having no effects on feeding or body adiposity in the free-fed state, impairs triglyceride and ketone body release from the liver during prolonged fasting. Furthermore, reducing CNS Agrp expression in wild-type mice by RNAi protected against the development of hepatic steatosis not only during starvation, but also in response to consumption of a high-fat diet. These findings identify the leptin-AGRP circuit as a critical modulator of hepatic triglyceride stores in starvation and suggest a vital role for this circuit in sustaining the supply of energy from the liver to extrahepatic tissues during periods of prolonged food deprivation.
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signal transducer and activator of transcription stat binding sites but not stat3 are required for fasting induced transcription of agouti related Protein messenger ribonucleic acid
Molecular Endocrinology, 2006Co-Authors: Christopher B Kaelin, Gregory S. Barsh, Michael W Schwartz, Lijie Gong, Fayi Yao, Kristin Hockman, Gregory J Morton, Robert G MackenzieAbstract:Energy homeostasis depends on the regulation of hypothalamic neurons by leptin, an adipocyte hormone whose circulating levels communicate body energy stores. Leptin activates the transcription factor signal transducer and activator of transcription 3 (Stat3) in hypothalamic neurons, including neuronal subtypes producing Agouti-Related Protein (Agrp), a neuropeptide that stimulates feeding. Previous studies have suggested a model in which high levels of Agrp transcription during fasting represent a default state that is actively repressed by phospho-Stat3 induced by leptin signaling in the fed state. We identify putative Stat3 binding elements in the Agrp promoter that have been highly conserved during vertebrate evolution. Using a reporter assay in transgenic mice that faithfully recapitulates normal regulation of Agrp, we show that these sites are required, but in a way opposite to that predicted by the existing model: mutation of the sites leads to a default state characterized by a low level of Agrp tr...
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transcriptional regulation of agouti related Protein agrp in transgenic mice
Endocrinology, 2004Co-Authors: Christopher B Kaelin, Gregory S. BarshAbstract:Agouti-Related Protein (Agrp) encodes a hypothalamic neuropeptide that promotes positive energy balance by stimulating food intake and reducing energy expenditure. Agrp expression in the brain is restricted to neurons within the arcuate nucleus of the hypothalamus, and expression levels are elevated as a consequence of food deprivation. We tested a series of bacterial artificial chromosome reporter constructs with varying amounts of sequence flanking the Agrp transcription unit in transgenic mice to identify and refine a region of DNA capable of recapitulating characteristics of Agrp expression. We report that a 42.5-kb region upstream of Agrp,containingthreedistinctregionsthatareevolutionarily conserved between mouse and human, is necessary and sufficient to consistently drive reporter expression specifically within AgRP neurons in a fasting-responsive manner. In addition, we demonstrate that this region allows for the stable expression of Cre recombinase in transgenic mice, providing a genetic tool for studying anabolic neural circuits that control energy balance. (Endocrinology 145: 5798–5806, 2004)
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Inverse agonist activity of agouti and Agouti-Related Protein.
Peptides, 2003Co-Authors: Richard R. Neubig, Gregory S. Barsh, Darren A. Thompson, Glenn L. Millhauser, Pilgrim J. Jackson, Chris J. Dickinson, Yu Mei Lai, Ira GantzAbstract:Abstract Agouti and Agouti-Related Protein (AgRP) are endogenous antagonists of the melanocortin receptors (MCxR). Previous data showed that recombinant full-length agouti and a synthetic fragment of AgRP, AgRP (83–132), are inverse agonists at the MC1R and MC4R, respectively. This study demonstrates the smaller analogs AgRP (87–120) and ASIP [90–132 (L89Y)], and short peptides Yc[CRFFNAFC]Y and Qc[CRFFRSAC]S are also MC4R inverse agonists. Furthermore, the relative affinity of the series of MC4R ligands for displacement of radiolabeled antagonist 125 I -AgRP (86–132) versus radiolabeled agonist 125 I -NDP-MSH did not correlate with ligand efficacy, which is more consistent with an induced-fit model than a simple two-state model of MC4R activation. These data shed new light on the determinants and mechanism of inverse agonism at the MC4R.
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Loops and links: structural insights into the remarkable function of the Agouti-Related Protein.
Annals of the New York Academy of Sciences, 2003Co-Authors: Glenn L. Millhauser, Gregory S. Barsh, Darren A. Thompson, Pilgrim J. Jackson, Joe C. Mcnulty, Ira GantzAbstract:The Agouti-Related Protein (AGRP) is an endogenous antagonist of the melanocortin receptors MC3R and MC4R found in the hypothalamus and exhibits potent orexigenic activity. The cysteine-rich C-terminal domain of this Protein, corresponding to AGRP(87-132), exhibits receptor binding affinity and antagonism equivalent to that of the full-length Protein. We recently determined the NMR structure of AGRP(87-132) and demonstrated that a portion of the domain adopts the inhibitor cystine-knot fold. Remarkably, this is the first identification of a mammalian Protein with this specific architecture. Further analysis of the structure suggests that melanocortin receptor contacts are made primarily by two loops presented within the cystine knot. (10) To test this hypothesis we designed a 34-residue AGRP analogue corresponding to only the cystine knot. We found that this designed miniProtein folds to a homogeneous product, retains the desired cystine-knot architecture, functions as a potent antagonist, and maintains the melanocortin receptor pharmacological profile of AGRP(87-132). (26) The AGRP-like activity of this molecule supports the hypothesis that indeed the cystine-knot region possesses the melanocortin receptor contacts. Based on these design and structure studies, we propose that the N-terminal loop of AGRP(87-132) makes contact with a receptor exoloop and helps confer AGRP's selectivity for the central MCRs.
Ira Gantz - One of the best experts on this subject based on the ideXlab platform.
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Chimeras of the Agouti-Related Protein: insights into agonist and antagonist selectivity of melanocortin receptors.
Peptides, 2005Co-Authors: Pilgrim J. Jackson, Ira Gantz, Darren A. Thompson, Benjamin Hunrichs, Glenn L. MillhauserAbstract:The specific melanocortin receptors, MC3R and MC4R, are directly linked to metabolism and body weight control. These receptors are activated by the peptide hormone alpha-MSH and antagonized by the Agouti-Related Protein (AGRP). Whereas alpha-MSH acts broadly on most members of the MCR family (with the exception of MC2R), AGRP is highly specific for only MC3R and MC4R. AGRP is a complex ligand of approximately 100 amino acids. Within AGRP, MCR recognition and antagonism is localized to a 34 residue, cysteine-rich domain that adopts an inhibitor cystine knot (ICK) fold. An oxidatively folded peptide corresponding to this domain, referred to as mini-AGRP, exhibits full antagonist function and selectivity for MC3R and MC4R. Here we investigate a series of chimera Proteins based on the mini-AGRP scaffold. Amino acid sequences derived from peptide agonists are grafted into the mini-AGRP active loop, implicated in receptor recognition, with the goal of producing ICK based agonists specific for MC3R and MC4R. Several constructs indeed exhibited potent agonist activity; however, with all chimeras, receptor selectivity is significantly altered. Pharmacologic data indicate that the chimeras do not interact with MC receptors through native AGRP like contacts. A model to explain the data suggest that there is only partial overlap of the agonist versus antagonist binding surfaces within MC receptors. Moreover, accessibility to the binding pocket is highly receptor specific with MC3R being the least tolerant of ligand alterations.
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Peptoid mimics of agouti related Protein.
Bioorganic & medicinal chemistry letters, 2003Co-Authors: Darren A. Thompson, Ira Gantz, Hilary L.e. Rood, Michael A. Siani, Nicholai R. Douglas, Glenn L. MillhauserAbstract:Abstract The Agouti Related Protein (AGRP) is an endogenous antagonist of melanocortin-3 and -4 receptors, each of which plays a key role in body weight homeostasis. We designed a peptoid trimer based on AGRP 111–113 in which a single chiral atom is used to partially restrain the backbone structure. Peptoid 5 displaced both radiolabeled Nle4-α-MSH (IC50=3.1 μM) and AGRP (86–132) (IC50=1.9 μM) from the human melanocortin-4 receptor and functioned as an antagonist of α-MSH stimulated cAMP generation, thus providing an important lead in the development of AGRP mimetics.
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Inverse agonist activity of agouti and Agouti-Related Protein.
Peptides, 2003Co-Authors: Richard R. Neubig, Gregory S. Barsh, Darren A. Thompson, Glenn L. Millhauser, Pilgrim J. Jackson, Chris J. Dickinson, Yu Mei Lai, Ira GantzAbstract:Abstract Agouti and Agouti-Related Protein (AgRP) are endogenous antagonists of the melanocortin receptors (MCxR). Previous data showed that recombinant full-length agouti and a synthetic fragment of AgRP, AgRP (83–132), are inverse agonists at the MC1R and MC4R, respectively. This study demonstrates the smaller analogs AgRP (87–120) and ASIP [90–132 (L89Y)], and short peptides Yc[CRFFNAFC]Y and Qc[CRFFRSAC]S are also MC4R inverse agonists. Furthermore, the relative affinity of the series of MC4R ligands for displacement of radiolabeled antagonist 125 I -AgRP (86–132) versus radiolabeled agonist 125 I -NDP-MSH did not correlate with ligand efficacy, which is more consistent with an induced-fit model than a simple two-state model of MC4R activation. These data shed new light on the determinants and mechanism of inverse agonism at the MC4R.
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Loops and links: structural insights into the remarkable function of the Agouti-Related Protein.
Annals of the New York Academy of Sciences, 2003Co-Authors: Glenn L. Millhauser, Gregory S. Barsh, Darren A. Thompson, Pilgrim J. Jackson, Joe C. Mcnulty, Ira GantzAbstract:The Agouti-Related Protein (AGRP) is an endogenous antagonist of the melanocortin receptors MC3R and MC4R found in the hypothalamus and exhibits potent orexigenic activity. The cysteine-rich C-terminal domain of this Protein, corresponding to AGRP(87-132), exhibits receptor binding affinity and antagonism equivalent to that of the full-length Protein. We recently determined the NMR structure of AGRP(87-132) and demonstrated that a portion of the domain adopts the inhibitor cystine-knot fold. Remarkably, this is the first identification of a mammalian Protein with this specific architecture. Further analysis of the structure suggests that melanocortin receptor contacts are made primarily by two loops presented within the cystine knot. (10) To test this hypothesis we designed a 34-residue AGRP analogue corresponding to only the cystine knot. We found that this designed miniProtein folds to a homogeneous product, retains the desired cystine-knot architecture, functions as a potent antagonist, and maintains the melanocortin receptor pharmacological profile of AGRP(87-132). (26) The AGRP-like activity of this molecule supports the hypothesis that indeed the cystine-knot region possesses the melanocortin receptor contacts. Based on these design and structure studies, we propose that the N-terminal loop of AGRP(87-132) makes contact with a receptor exoloop and helps confer AGRP's selectivity for the central MCRs.
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Design, pharmacology, and NMR structure of a minimized cystine knot with Agouti-Related Protein activity.
Biochemistry, 2002Co-Authors: Pilgrim J. Jackson, Biaoxin Chai, Gregory S. Barsh, Yingkui Yang, Ira Gantz, Darren A. Thompson, Joe C. Mcnulty, Glenn L. MillhauserAbstract:The Agouti-Related Protein (AGRP) is an endogenous antagonist of the melanocortin receptors MC3R and MC4R found in the hypothalamus and exhibits potent orexigenic activity. The cysteine-rich C-terminal domain of this Protein, corresponding to AGRP(87-132), exhibits receptor binding affinity and antagonism equivalent to that of the full-length Protein. The NMR structure of this active domain was recently determined and suggested that melanocortin receptor contacts were made primarily by two loops presented by a well-structured cystine knot domain within AGRP(87-132) [McNulty et al. (2001) Biochemistry 40, 15520-15527]. This hypothesis is tested here with NMR structure and activity studies of a 34-residue AGRP analogue designed to contain only the cystine knot domain. The designed miniProtein folds to a homogeneous product, retains the desired cystine knot architecture, functions as an antagonist, and maintains the melanocortin receptor pharmacological profile of AGRP(87-132). The AGRP-like activity of this molecule supports the hypothesis that indeed the cystine knot region possesses the melanocortin receptor contact points. Moreover, this potent AGRP analogue is synthetically accessible, may serve in the development of therapeutics for the treatment of diseases related to energy balance. and may also find use as a new reagent for probing melanocortin receptor structure and function.
Roger D. Cone - One of the best experts on this subject based on the ideXlab platform.
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Reply to Braasch and Postlethwait: Evolutionary origin of the teleost A2 agouti genes (agouti signaling Protein 2 and Agouti-Related Protein 2) remains unclear
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Helgi B. Schiöth, Åke Västermark, Roger D. ConeAbstract:Tetrapods express one agouti gene [agouti signaling Protein (asip)] in the skin regulating pigmentation and a second [Agouti-Related Protein (agrp)] in the brain regulating energy homeostasis. In contrast, most teleosts have four genes encoding agouti-type Proteins. Braasch and Postlethwait (1) present an analysis of the evolutionary history of agouti genes in teleosts, reordering the phylogenetic tree proposed previously (2) and proposing a nomenclature change. However, gene nomenclature derives mainly from functional or sequence properties and not from evolutionary predictions. Furthermore, inclusion of an ancient agouti sequence from the elephant shark provides an additional interpretation of the phylogeny (Fig. 1).
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fasting induces a large leptin dependent increase in the intrinsic action potential frequency of orexigenic arcuate nucleus neuropeptide y agouti related Protein neurons
Endocrinology, 2005Co-Authors: Kanji A Takahashi, Roger D. ConeAbstract:The neuropeptide Y (NPY)/Agouti-Related Protein (AgRP) neurons of the hypothalamic arcuate nucleus are thought to promote feeding. Here, we demonstrate that feeding state in vivo, through a leptin-dependent process, induces large and persistent changes in the electrophysiological activity of these neurons as measured extracellularly in vitro. Consistent with an orexigenic role, fasting induced a 4-fold increase in the basal action potential frequency of NPY/AgRP neurons. Leptin, when injected into fasted wild-type mice, induced a dose- and time-dependent decrease in spike frequency, which approached fed levels 2–3 h post treatment. In leptin-deficient (lepob/lepob) and leptin receptor-deficient (leprdb/leprdb) mice, NPY/AgRP spike frequency was not significantly increased by fasting, and even in mutant mice fed ad libitum, spike frequency was at least as high as in fasted wild-type mice. All recordings included GABAA and ionotropic glutamate receptor antagonists, suggesting that expression of this modulat...
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Agouti-Related Protein (AGRP) is conserved and regulated by metabolic state in the zebrafish, Danio rerio.
Endocrine, 2003Co-Authors: Youngsup Song, Gregory Golling, Theresa L. Thacker, Roger D. ConeAbstract:Agouti-Related Protein (AGRP) and proopiomelanocortin (POMC) genes encode secreted hypothalamic factors regulated by metabolic state in mammals and are involved in energy homeostasis. The zebrafish, Danio rerio, is a model system for forward genetics in verte-brates: POMC and AGRP in this organism have not been well characterized. Toward this end, AGRP and POMC were cloned from zebrafish. Zebrafish AGRP cDNA encodes a 127-amino-acid Protein 36% and 40% identical to human and mouse AGRP, respectively. Zebrafish POMC cDNA encodes a 222-amino-acid preprohormone. Sequence identity to the mammalian ortholog is about 50%. Zebrafish AGRP and POMC transcripts were detected at 24 h post-fertilization (hpf) by RTPCR, and in situ hybridization demonstrated zebrafish AGRP mRNA exclusively in hypothalamus and POMC mRNA in hypothalamus and pituitary. Fasting did not alter POMC transcript levels, while AGRP transcripts were significantly upregulated. The ratio of AGRP/POMC transcripts in adult brain was increased up to threefold by fasting. These results demonstrate that the melanocortin system is regulated by metabolic state in zebrafish, and this finding thus provides a vertebrate system for the genetic analysis of the role of the melanocortin system in energy homeostasis.
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structure activity studies of the melanocortin 4 receptor by in vitro mutagenesis identification of agouti related Protein agrp melanocortin agonist and synthetic peptide antagonist interaction determinants
Biochemistry, 2001Co-Authors: Carrie Haskellluevano, Roger D. Cone, Eileen K. MonckAbstract:In vitro mutagenesis of the mouse melanocortin-4 receptor (mMC4R) has been performed, based upon homology molecular modeling and previous melanocortin receptor mutagenesis studies that identified putative ligand−receptor interactions. Twenty-three mMC4 receptor mutants were generated and pharmacologically characterized using several melanocortin-based ligands [α-MSH, NDP-MSH, MTII, dNal (1‘)7-MTII, Nal(2‘)7-MTII, SHU9119, and SHU9005]. Selected mutant receptors possessing significant differences in the melanocortin-based peptide agonist and/or antagonist pharmacology were further evaluated using the endogenous antagonist Agouti-Related Protein fragment hAGRP(83−132) and hAGRP(109−118) molecules. These studies of the mouse MC4R provide further experimental data suggesting that the conserved melanocortin receptor residues Glu92 (TM2), Asp114 (TM3), and Asp118 (TM3) (mouse MC4R numbering) are important for melanocortin-based peptide molecular recognition. Additionally, the Glu92 and Asp118 mMC4R residues are...
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Altered expression of Agouti-Related Protein and its colocalization with neuropeptide Y in the arcuate nucleus of the hypothalamus during lactation.
Endocrinology, 1999Co-Authors: Peilin Chen, Roger D. Cone, Carrie Haskell-luevano, M. Susan SmithAbstract:During lactation, the levels of neuropeptide Y (NPY), which plays an important role in mediating food intake, are significantly elevated in a number of hypothalamic areas, including the arcuate nucleus (ARH). To identify additional hypothalamic systems that might be important in mediating the increase in food intake and alterations in energy homeostasis during lactation, the present studies examined the expression of Agouti-Related Protein (AGRP), a recently described homologue of the skin agouti Protein. AGRP is found in the hypothalamus and has been suggested to play an important role in the regulation of food intake. In the first experiment, animals were studied during diestrus of the estrous cycle, a stage of the cycle when estrogen levels are basal and similar to lactation, or during days 12–13 postpartum. Lactating animals had their litters adjusted to eight pups on day 2 postpartum. Brain tissue sections were used to measure AGRP messenger RNA (mRNA) levels by in situ hybridization. AGRP mRNA signa...