Interactions of α-Melanotropin and Agouti on B16 Melanoma Cells: Evidence for Inverse Agonism of Agouti

Siegrist, Walter; Drozdz, Roma; Cotti, Renato; Willard, Derril H.; Wilkison, William O.; Eberlé, Alex N.

doi:10.3109/10799899709036595

Cited by 81 publications

(57 citation statements)

References 40 publications

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“…Structures of hMC4R small-molecule agonists. Putative arrangement of the N-terminal fragment (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) inside the binding pocket of hMC4R, docked similarly to the peptide agonistα-MSH (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). The N-terminal fragment is shown in the licorice representation colored by element,α-MSH is shown by a thin purple line.…”

Section: Supplementary Materialsmentioning

confidence: 99%

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,

et al. 2005

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Specific interactions of human melanocortin-4 receptor (hMC4R) with its non-peptide and peptide agonists were studied using alanine-scanning mutagenesis. The binding affinities and potencies of two synthetic small-molecule agonists (THIQ, MB243) were strongly affected by substitutions in transmembrane α-helices (TM) 2, 3, 6, and 7 (residues Glu 100 Asp 122 , Asp 126 , Phe 261 , His 264 , Leu 265 , and Leu 288 ). In addition, I129A mutation primarily affected binding and potency of THIQ, while F262A, W258A, Y268A mutations impaired interactions with MB243. By contrast, binding affinity and potency of the linear peptide agonist NDP-MSH were substantially reduced only in D126A and H264A mutants. 3D models of receptor-ligand complexes with their agonists were generated by distance geometry using the experimental, homology-based, and other structural constraints, including interhelical H-bonds and two disulfide bridges (Cys 40 -Cys 279 , Cys 271 -Cys 277 ) of hMC4R. In the models, all pharmacophore elements of small-molecule agonists are spatially overlapped with the corresponding key residues (His 6 , D-Phe 7 , Arg 8 and Trp 9 ) of the linear peptide: their charged amine groups interact with acidic residues from TM2 and TM3, similar to His 6 and Arg 6 of NDP-MSH; their substituted piperidines mimic Trp 9 of the peptide and interact with TM5 and TM6; while the D-Phe aromatic rings of all three agonists contact with Leu 133 , Trp 258 , and Phe 261 residues.Melanotropins, which include melanocyte-stimulating hormones (α-, β-, and γ-MSH) and adrenocorticotropic hormone (ACTH), are the products of proteolytic cleavage of the 31-36 kDa precursor, pro-opiomelanocortin (1). α-MSH (Ac-Ser 1 -Tyr 2 -Ser 3 -Met 4 -Glu 5 -His 6 -Phe 7 -Arg 8 -Trp 9 -Gly 10 -Lys 11 -Pro 12 -Val 13 -NH 2 ) shares with all melanotropins the central core tetrapeptide 'His 6 -Phe 7 -Arg 8 -Trp 9 ', which is essential for its biological activity (2). These neuropeptides exert their function through five subtypes of melanocortin receptors (MCRs), which have been cloned and characterized (1,3). MCRs belong to the G protein-coupled receptor (GPCR) superfamily (4) and are positively coupled to cAMP-generation by adenylate cyclase via the stimulatory Gs-proteins. They are involved in regulation of multiple physiological functions, such as pigmentation (MC1R), adrenal cortical steroidogenesis † This work was supported by NIH grants DK054032 (I. Table of receptor type-specific distance constraints for the distance geometry refinement of the model of the active conformation of MC4R. This material is available free of charge via the Internet at http://pubs.acs.org.G NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2008 September 8. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript (MC2R), exocrine secretion (MC5R), energy homeostasis, penile erection (MC3R and MC4R) and many others (1,5,6).The MC4R subtype is regarded as a potential drug target, because it is involved in feeding and sexual ...

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Section: Supplementary Materialsmentioning

confidence: 99%

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,

et al. 2005

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“…We and others hypothesize that keratinocyte-derived α-MSH binds to Mc1r on epidermal melanocytes, initiating downstream production of the cAMP second messenger through activation of adenylyl cyclase 1 . Eumelanin synthesis can be stimulated pharmacologically by agents that raise cAMP levels 1,14,[31][32][33][34][35] .…”

Section: Introductionmentioning

confidence: 99%

Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model

Amaro-Ortiz

Vanover

Scott

et al. 2013

JoVE

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Fairness of skin, UV sensitivity and skin cancer risk all correlate with the physiologic function of the melanocortin 1 receptor, a G s -coupled signaling protein found on the surface of melanocytes. Mc1r stimulates adenylyl cyclase and cAMP production which, in turn, up-regulates melanocytic production of melanin in the skin. In order to study the mechanisms by which Mc1r signaling protects the skin against UV injury, this study relies on a mouse model with "humanized skin" based on epidermal expression of stem cell factor (Scf). K14-Scf transgenic mice retain melanocytes in the epidermis and therefore have the ability to deposit melanin in the epidermis. In this animal model, wild type Mc1r status results in robust deposition of black eumelanin pigment and a UV-protected phenotype. In contrast, K14-Scf animals with defective Mc1r signaling ability exhibit a red/blonde pigmentation, very little eumelanin in the skin and a UV-sensitive phenotype. Reasoning that eumelanin deposition might be enhanced by topical agents that mimic Mc1r signaling, we found that direct application of forskolin extract to the skin of Mc1r-defective fair-skinned mice resulted in robust eumelanin induction and UV protection 1 . Here we describe the method for preparing and applying a forskolin-containing natural root extract to K14-Scf fair-skinned mice and report a method for measuring UV sensitivity by determining minimal erythematous dose (MED). Using this animal model, it is possible to study how epidermal cAMP induction and melanization of the skin affect physiologic responses to UV exposure. Video LinkThe video component of this article can be found at

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“…Other studies have demonstrated that both AP and AgRP act as inverse agonists rather than classical competitive antagonists of MCRs (9). Thus, these authors (8,9) suggest a more complex mechanism by which APs and the melanocortin peptides mediate a physiological response via the MCRs.…”

Section: Introductionmentioning

confidence: 99%

Ectopic Agouti protein overexpression increases stimulated corticosterone production without effect on adenylate cyclase activity in mouse adrenal cells

Shevchenko

Бажан²,

Макарова³

et al. 2004

European Journal of Endocrinology

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Objective: The antagonism of Agouti protein (AP) and Agouti-related protein on melanocortin receptors suggests an inhibitory role in the regulation of steroidogenesis. However, we have previously demonstrated that ectopic AP overexpression increased restraint-induced corticosterone release and adrenal reactivity to ACTH in mice. A high steroidogenic response to ACTH may be a consequence of a stimulatory AP action on the adenylate cyclase (AC) and/or intracellular steroidogenic enzymes. The aim of the present study was to estimate the effect of ectopic AP overexpression on the activity of AC and steroidogenic intracellular enzymes. Methods: ACTH and forskolin were used for AC stimulation, and dibutyryl cAMP and progesterone were used for stimulation of intracellular steroidogenic enzymes in isolated adrenal cells in male C57Bl/6J mice of two Agouti genotypes: A y /a (ectopic AP overexpression) and a/a (absence of AP in all tissues). Results: ACTH and forskolin increased cAMP accumulation to the same extent in both A y /a and a/a mouse adrenal cells (P , 0.001; ANOVA), but resulted in higher corticosterone production in A y /a mice (P , 0.001 for ACTH and P , 0.01 for forskolin; ANOVA). Dibutyryl cAMP-and progesterone-induced corticosterone production was higher in A y /a mice than in a/a mice (P , 0.001 for dibutyryl cAMP and P , 0.01 for progesterone; ANOVA). Conclusions: Ectopic AP overexpression increased stimulated corticosterone production and intracellular steroidogenic enzyme reactivity to cAMP without an effect on AC activity.

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Interactions of α-Melanotropin and Agouti on B16 Melanoma Cells: Evidence for Inverse Agonism of Agouti

Cited by 81 publications

References 40 publications

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,

Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model

Ectopic Agouti protein overexpression increases stimulated corticosterone production without effect on adenylate cyclase activity in mouse adrenal cells

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Interactions of α-Melanotropin and Agouti on B16 Melanoma Cells: Evidence for Inverse Agonism of Agouti

Cited by 81 publications

References 40 publications

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists,

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists,

Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model

Ectopic Agouti protein overexpression increases stimulated corticosterone production without effect on adenylate cyclase activity in mouse adrenal cells

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Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,

Interactions of Human Melanocortin 4 Receptor with Nonpeptide and Peptide Agonists^,