γ2-Melanocyte stimulation hormone (γ2-MSH) truncation studies results in the cautionary note that γ2-MSH is not selective for the mouse MC3R over the mouse MC5R

Abstract

The melanocortin system has been implicated in a multitude of physiological pathways including obesity, satiety, energy homeostasis, sexual behavior, pigmentation, sodium regulation, hypertension, and many others. Based upon studies of the endogenous melanocortin receptor agonists at the cloned human melanocortin receptor proteins, it was concluded that the γ-MSH related agonist ligands are selective for the MC3 versus the MC4 and MC5 receptors. In attempts to understand and identify the specific amino acids of γ 2 -MSH important for MC3R selectivity, we have performed Nand C-terminal truncation studies and pharmacologically characterized twenty-eight ligands at the mouse MC1 and MC3-5 melanocortin receptors. The C-terminal Trp-Asp 9 -Arg 10 -Phe 11 residues are important for nM potency at the mMC3R and the Arg 7 -Trp 8 residues are important for mMC5R nM potency. We observed the unanticipated results that several of the C-terminal truncated analogues possessed nM agonist potency at the mMC3 and mMC5Rs which lead us to performed a comparative side-by-side study of the mouse and human MC5R. These data resulted in μM γ 2 -MSH analogue potency at the hMC5R, consistent with previous reports, however at the mMC5R, nM γ 2 -MSH analogue potency was observed. Thus, these data support the hypothesis of important species specific differences in γ-MSH related ligand potency at the rodent versus human MC5R subtype that is critical for the interpretation of in vivo rodent physiological studies. These results prompted us to examine the affects of a peripherally administered melanocortin agonist on hypothalamic gene expression levels of the MC3R, MC4R, and MC5R. The super potent non-selective NDP-MSH agonist was administered i.p. and resulted in significantly decreased levels of mMC3R and mMC5R hypothalamic mRNA versus saline control. These data provide for the first time data demonstrating peripherally administered NDP-MSH can modify hypothalamic melanocortin receptor expression levels. KeywordsMelanotropin; heart; blood pressure; obesity; receptor brain expression; GPCR © 2010 Elsevier Inc. All rights reserved. * Reprint request should be addressed to Dr. Carrie Haskell-Luevano, University of Florida, Department of Pharmacodynamics, P. O. Box 100487, Gainesville, FL 32610-0487. Phone (352) Fax (352) 273-7723, carrie@cop.ufl.edu.. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptPeptides. Author manuscript; available in PMC 2011 December 1. Published in final edited form as:Peptides. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA...

Both MC 1 and MC 3 Receptors Provide Protection From Cerebral Ischemia-Reperfusion–Induced Neutrophil Recruitment

“…BMS-470539 is almost entirely selective for MC 1 , whilst [DTRP 8 ]-γ-MSH may activate other MCs than MC 3 9 . To further examine the roles of specific MC subtypes, the MC 3/4 antagonist SHU9119 was co-administered with either α-MSH or [DTRP 8 ]-γ-MSH (Figure 3C and D), revealing that MC 3/4 antagonism caused no increase in rolling or adhesion at 40min reperfusion vs. α-MSH or [DTRP 8 ]-γ-MSH alone.…”

“…The melanocortin receptor system displays a number of disparities between humans and rodents and a number of MC agonists and antagonists have different selectivity in MCs from different species 9,11 . To assess the effectiveness of melanocortin treatments on human cells, we utilized the neutrophil flow chamber model and chemotaxis assay to investigate neutrophil inflammatory function (Supplemental Figure VII).…”

Bench-top to clinical therapies: A review of melanocortin ligands from 1954 to 2016

“…An alanine positional scan of γ 2 -MSH indicated residues Met 3 , His 5 , Phe 6 , Arg 7 , and Trp 8 were all functionally important for stimulation of the MC3-5R, similar to residues in α-MSH important for activity [69]. Differences in functional receptor selectivity have been observed between species, where γ 2 -MSH possessed a 100-fold selectivity for the human (h)MC3R over the hMC5R [69, 70], whereas there was no potency difference between the mouse (m)MC3R and mMC5R [71]. When the activity of γ 2 -MSH was compared in parallel between the MC1R, MC3R, MC4R, and MC5R, both the mouse and human MC1R and MC4R possessed similar sub-micromolar potencies [71, 72], although the potency of γ 2 -MSH at the hMC3R [72] was approximately 100-fold lower than previous reports [9, 69, 70].…”

“…Differences in functional receptor selectivity have been observed between species, where γ 2 -MSH possessed a 100-fold selectivity for the human (h)MC3R over the hMC5R [69, 70], whereas there was no potency difference between the mouse (m)MC3R and mMC5R [71]. When the activity of γ 2 -MSH was compared in parallel between the MC1R, MC3R, MC4R, and MC5R, both the mouse and human MC1R and MC4R possessed similar sub-micromolar potencies [71, 72], although the potency of γ 2 -MSH at the hMC3R [72] was approximately 100-fold lower than previous reports [9, 69, 70]. Expression of γ-MSH in the brain is predominantly in the pituitary and hypothalamic arcuate [73-76], but has also been reported in the adrenal medulla [77].…”

Melanocortin-3 Receptors and Metabolic Homeostasis

“…These compounds should also be characterized using mouse receptors, as there can be species specificity in activity. 193 The pharmacology is further complicated by the issue of biased agonism (i.e., ligands of the same receptor that can stabilize distinct receptor conformations and preferentially modulate one signaling pathway to the exclusion of others) and by the heterodimers formed between the MC3R and MC4Rs with other GPCRs that are involved in the regulation of ingestive behaviors and metabolism.…”