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Summary of the detected nonsynonymous variants in MRAP2
Source publication
Objective:
The melanocortin receptor accessory protein 2 (MRAP2) is relevant for weight regulation in mice and humans. This function is likely mediated by regulation of the melanocortin-4 receptor (MC4R). Functional implications of human MRAP2 mutations have not been described yet.
Methods:
A mutation screen was conducted in MRAP2 in 184 childre...
Contexts in source publication
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... coding region of MRAP2 was analyzed by four PCR fragments (F1-4; Supporting Information Table S1). Fragment 1 was screened for mutations by denaturing high-performance liquid chromatogra- phy (dHPLC) as described previously (14). ...
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... screen of the coding region of MRAP2 identified a total of eight variants. Two are novel coding variants (p.Ala137Thr, p.Gln174Arg, Table 1; Supporting Information Figure S1), one known nonsynonymous (rs115655382: p.Arg125His, Table 1), two synony- mous variants: rs9449776 (p.Asn1595), rs2875382 (p.His2015), and three intronic variants (rs4556336, rs112932891, rs9449777). The analysis of all detected variants by in silico programs revealed a potential functional impact for p.Gln174Arg only. ...
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... screen of the coding region of MRAP2 identified a total of eight variants. Two are novel coding variants (p.Ala137Thr, p.Gln174Arg, Table 1; Supporting Information Figure S1), one known nonsynonymous (rs115655382: p.Arg125His, Table 1), two synony- mous variants: rs9449776 (p.Asn1595), rs2875382 (p.His2015), and three intronic variants (rs4556336, rs112932891, rs9449777). The analysis of all detected variants by in silico programs revealed a potential functional impact for p.Gln174Arg only. ...
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... p.Ala137Thr is located in a conserved position among dif- ferent species (Table 1). Among 42 species (10 primates, 7 rodents, 15 laurasiatheria, 3 placental mammals, and 7 sauropsida) 30 also show the amino acid alanine at that position (Supporting Information Figure S2). ...
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... second unknown nonconservative, nonsynonymous variation p.Gln174Arg affects a highly conserved position (Table 1). Hence, the amino acid glutamine at position 174 in MRAP2 is found in all 42 species we in silico screened (Supporting Information Figure S2). ...
Citations
... The identification of the first human MRAP2 mutations found in obese patients highlighted the role of MRAP2 in modulating MC4R signaling 4,24,28 . It was presumed that MRAP2 would function analogously to RAMPs, that can modulate GPCRs by influencing their trafficking to the cell surface, expression, ligand binding, signaling and internalization. ...
... Our findings that MRAP2 increases the capacity of MC4R to activate different G protein subtypes begs the questions (a) is this a true reflection of physiology and (b) how this might be achieved. In support of the former, there is a precedent for these findings in previous studies that demonstrated a reduction of MC4R signaling in the presence of loss-of-function MRAP2 mutations 4,24,28 . In addition, a more specific increase in Gs and Gq activation by MC4R was observed in HEK293 cells that stably express MRAP2 51 . ...
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor (GPCR) and a key regulator of appetite and metabolism. It can interact with the melanocortin-receptor accessory protein 2 (MRAP2), a single transmembrane helix protein known to interplay with several different GPCRs. However, the consequences of this interaction are not completely understood. Here we report that co-expression of MRAP2 has multiple effects on the MC4R: it enhances G protein-mediated signaling and simultaneously impairs β-arrestin2 recruitment and, consequently, internalization. In addition, co-expression of MRAP2 leads to an increased number of monomers of MC4R by disrupting receptor oligomers. A structural model of the active state MC4R–MRAP2 complex supports the experimentally observed monomerization. Taken together, our data indicate that MRAP2 is an accessory protein that interacts with and influences MC4R structure, biasing its signaling towards G protein-mediated effects.
... were found in patients with obesity (23,(26)(27)(28). Mrap2 -/mice develop severe obesity, although they lack the early-onset hyperphagia of Mc4r -/mice (23), which brings into question the extent to which MRAP2 qualitatively and quantitatively interacts with MC4R in vivo. ...
... MRAP2 promotes MC4R targeting to the primary cilium in heterologous cells. The interaction between MRAP2 and MC4R, as well as the cellular localization of MRAP2, have been previously studied in nonciliated cells (23)(24)(25)(26)30). Since MC4R localizes to the primary cilium, and MRAP2 has been reported to interact with MC4R in vitro (23), we tested whether MRAP2 colocalizes with MC4R at the primary cilium following transient transfection in murine ciliated inner medullary collecting duct 3 (IMCD3) cells. ...
... Previous in vitro studies in unciliated cells have reported conflicting effects of MRAP2 on MC4R function: one study reported that MRAP2 does not affect MC4R activity (30), another suggested that MRAP2 may inhibit MC4R activity (24), and others reported that MRAP2 increases its response to ligand (23,25). MRAP2 was also reported to either positively or negatively regulate MC4R activity depending on their relative concentrations (26). Similarly, MRAP2 has been reported to either decrease (24) or modestly increase (25) MC4R cell-surface expression. ...
The G protein-coupled receptor melanocortin-4 receptor (MC4R) and its associated protein melanocortin receptor-associated protein 2 (MRAP2) are essential for the regulation of food intake and body weight in humans. MC4R localizes and functions at the neuronal primary cilium, a microtubule-based organelle that senses and relays extracellular signals. Here, we demonstrate that MRAP2 is critical for the weight-regulating function of MC4R neurons and the ciliary localization of MC4R. More generally, our study also reveals that GPCR localization to primary cilia can require specific accessory proteins that may not be present in heterologous cell culture systems. Our findings further demonstrate that targeting of MC4R to neuronal primary cilia is essential for the control of long-term energy homeostasis and suggest that genetic disruption of MC4R ciliary localization may frequently underlie inherited forms of obesity.
... This might be due to certain differences between the cell lines, such as the difference in the expression of regulatory proteins. Melanocortin 2 receptor accessory protein 2 (MRAP2) is a regulatory protein that is expressed in the HEK-293 cells we used [52], but not in COS-7 cells [53]. Several studies have shown that MC4R signaling is highly affected by MRAP2 [54][55][56][57][58]; therefore, the presence or rather, in the case of COS-7 cells, the absence of MRAP2 can affect results. ...
The melanocortin-4 receptor (MC4R) is critical for central satiety regulation, therefore presenting a potent target for pharmacological obesity treatment. Melanocortin-4 receptor mutations prevalently cause monogenetic obesity. A possibility of overcoming stop mutations is aminoglycoside-mediated translational readthrough. Promising results were achieved in COS-7 cells, but data for human cell systems are still missing, so uncertainty surrounds this potential treatment. In transfected HEK-293 cells, we tested whether translational readthrough by aminoglycoside Geneticin combined with high-affinity ligand setmelanotide, which is effective in proopiomelanocortin or leptin receptor deficiency patients, is a treatment option for affected patients. Five MC4R nonsense mutants (W16X, Y35X_D37V, E61X, W258X, Q307X) were investigated. Confocal microscopy and cell surface expression assays revealed the importance of the mutations’ position within the MC4R. N-terminal mutants were marginally expressed independent of Geneticin treatment, whereas mutants with nonsense mutations in transmembrane helix 6 or helix 8 showed wild-type-like expression. For functional analysis, Gs and Gq/11 signaling were measured. N-terminal mutants (W16X, Y35X_D37V) showed no cAMP formation after challenge with alpha-MSH or setmelanotide, irrespective of Geneticin treatment. Similarly, Gs activation was almost impossible in W258X and Q307X with wild-type-like cell surface expression. Results for Gq/11 signaling were comparable. Based on our data, this approach improbably represents a therapeutic option.
... 15 • Single-gene defects: The majority of Mendelian obesity cases are caused by a deficiency in mutation in a gene involved in the leptin-melanocortin signaling pathway, which is a key regulator of energy balance. 16 Monogenic obesity has been linked to mutations in 16 genes: adenylate cyclase 3 (ADCY3), brain-derived neurotrophic factor (BDNF), dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1B), kinase suppressor of ras 2 (KSR2), LEP, LEPR, melanocortin 4 receptor tyrosine kinase 2 (NTRK2), proprotein convertase subtilisin/kexin type 1 (PCSK1), POMC, peroxisome proliferator-activated receptor γ (PPARG), SH2B adaptor protein 1 (SH2B1), SIM BHLH transcription factor 1 (SIM1), and TUB bipartite transcription factor (TUB). 17,18 Although projections of the prevalence of these Mendelian diseases vary by study, they all account for a small percentage of obese people. They are responsible between 5 and 50% can contribute to obesity collectively. ...
Obesity is a globally expanding silent epidemic having multiple risk factors and consequences associated with it. Genetic factors have been found to be playing undeniable roles in obesity. Intermingled relationship between epigenetics, metagenomics, and the environment influences obesity traits. High precision diagnostic tools have outlined many single nucleotide polymorphisms (SNPs), as well as many novel genes, that have been identified that create an obesogenic environment. Rare single-gene diseases can lead to early childhood obesity and less satiety. With almost 30% of the global population being under the grip of obesity, the coming days are alarming. This review summarizes the existing knowledge on the genetic causes of obesity including the epidemiology as well as the issues of concern and new additions to the list. Furthermore, we discuss the ways to enhance the healthcare outcome for patients of obesity through interdepartmental collaborations apart from pharmacological therapy that is still limited to a few drugs. The teamwork of geneticists, genetic counselors, physicians, bariatric surgeons, nurses, endocrinologists, and pharmacists may provide promising results in intervention.
... Mutations of arginine 125 in histidine (R125H) or cysteine (R125C) have been detected in the conserved C-terminal region of MRAP2 in humans, where they are correlated with an extreme obesity phenotype [11][12][13]. Mouse MRPA2, despite high sequence identity with its human counterpart, normally exhibits a substitution of arginine 125 for histidine, and shows greater efficiency in modulating the activity of PKRs. We produced two MRAP2 mutants in which the Arg125 residue was replaced by histidine or cysteine, then analyzed their interactions with PKR2 using yeast as a heterologous expression system. ...
... The arginine residue at position 125 is extremely conserved in primates and replaced by histidine in rodents ( Figure 1A). Interestingly, mutation of arginine 125 with histidine or cysteine leads to hyperphagic obesity in humans [11][12][13]. ...
... Mutations of arginine 125 in histidine (R125H) or cysteine (R125C) have been detected in the conserved C-terminal region of MRAP2 in humans, where they are correlated with an extreme obesity phenotype [11][12][13]. Mouse MRPA2, despite high sequence identity with its human counterpart, normally exhibits a substitution of arginine 125 for histidine, and shows greater efficiency in modulating the activity of PKRs. ...
MRAP2 is a small simple transmembrane protein arranged in a double antiparallel topology on the plasma membrane. It is expressed in the paraventricular nucleus of the hypothalamus, where it interacts with various G protein-coupled receptors, such as the prokineticin receptors, and regulates energy expenditure and appetite. The aim of this work was to analyze the functional role of the specific arginine residue at position 125 of MRAP2, which affects protein conformation, dimer formation, and PKR2 binding. Results obtained with the MRAP2 mutants R125H and R125C, which are found in human patients with extreme obesity, and mouse MRAP2, in which arginine 125 is normally replaced by histidine, were compared with those obtained with human MRAP2. Understanding the mechanism by which MRAP2 regulates G protein-coupled receptors helps in elucidating the metabolic pathways involved in metabolic dysfunction and in developing new drugs as specific targets of the MRAP2-PKR2 complex.
... One limitation of this model is that HEK293 cells cannot provide the same physiological setting that is present in the hypothalamic (paraventricular nucleus), where most MC4R activity related to weight regulation is anticipated [10]. Additionally, the marginal presence of the melanocortin 2 receptor accessory protein 2 (MRAP2) in HEK293 cells, which possibly influences MC4R signaling and is discussed in detail below, should be taken into consideration [35,36]. ...
... Results showed that coexpression of MRAP2 with MC4R enhances G s signaling. This makes MRAP2 an interesting endogenous allosteric factor when discussing dimer separation and its benefits [36]. ...
... Results showed that coexpression of MRAP2 with MC4R enhances Gs signaling. This makes MRAP2 an interesting endogenous allosteric factor when discussing dimer separation and its benefits [36]. Taken together, the study results provide information on the positive effect that inducing dimer separation of the MC4R has on G s as well as G q/11 signaling capacities in human HEK293 cells. ...
Melanocortin 4 receptor (MC4R) is part of the leptin-melanocortin pathway and plays an essential role in mediating energy homeostasis. Mutations in the MC4R are the most frequent monogenic cause for obesity. Due to increasing numbers of people with excess body weight, the MC4R has become a target of interest in the search of treatment options. We have previously reported that the MC4R forms homodimers, affecting receptor Gs signaling properties. Recent studies introducing setmelanotide, a novel synthetic MC4R agonist, suggest a predominant role of the Gq/11 pathway regarding weight regulation. In this study, we analyzed effects of inhibiting homodimerization on Gq/11 signaling using previously reported MC4R/CB1R chimeras. NanoBRETTM studies to determine protein–protein interaction were conducted, confirming decreased homodimerization capacities of chimeric receptors in HEK293 cells. Gq/11 signaling of chimeric receptors was analyzed using luciferase-based reporter gene (NFAT) assays. Results demonstrate an improvement of alpha-MSH-induced NFAT signaling of chimeras, reaching the level of setmelanotide signaling at wild-type MC4R (MC4R-WT). In summary, our study shows that inhibiting homodimerization has a setmelanotide-like effect on Gq/11 signaling, with chimeric receptors presenting increased potency compared to MC4R-WT. These findings indicate the potential of inhibiting MC4R homodimerization as a therapeutic target to treat obesity.
... 15 • Single-gene defects: The majority of Mendelian obesity cases are caused by a deficiency in mutation in a gene involved in the leptin-melanocortin signaling pathway, which is a key regulator of energy balance. 16 Monogenic obesity has been linked to mutations in 16 genes: adenylate cyclase 3 (ADCY3), brain-derived neurotrophic factor (BDNF), dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1B), kinase suppressor of ras 2 (KSR2), LEP, LEPR, melanocortin 4 receptor tyrosine kinase 2 (NTRK2), proprotein convertase subtilisin/kexin type 1 (PCSK1), POMC, peroxisome proliferator-activated receptor γ (PPARG), SH2B adaptor protein 1 (SH2B1), SIM BHLH transcription factor 1 (SIM1), and TUB bipartite transcription factor (TUB). 17,18 Although projections of the prevalence of these Mendelian diseases vary by study, they all account for a small percentage of obese people. They are responsible between 5 and 50% can contribute to obesity collectively. ...
Obesity is a globally expanding silent epidemic having multiple risk factors and consequences associated with it. Genetic factors have been found to be playing undeniable roles in obesity. Intermingled relationship between epigenetics, metagenomics, and the environment influences obesity traits. High precision diagnostic tools have outlined many single nucleotide polymorphisms (SNPs), as well as many novel genes, that have been identified that create an obesogenic environment. Rare single-gene diseases can lead to early childhood obesity and less satiety. With almost 30% of the global population being under the grip of obesity, the coming days are alarming. This review summarizes the existing knowledge on the genetic causes of obesity including the epidemiology as well as the issues of concern and new additions to the list. Furthermore, we discuss the ways to enhance the healthcare outcome for patients of obesity through interdepartmental collaborations apart from pharmacological therapy that is still limited to a few drugs. The teamwork of geneticists, genetic counselors, physicians, bariatric surgeons, nurses, endocrinologists, and pharmacists may provide promising results in intervention.
... Some alleles were significantly associated with adult human height (Wood et al., 2014). This gene would play a role in growth, as well as another candidate, MRAP2, which modulates melanocortin receptor signaling and have been associated with severe obesity in human (Asai et al., 2013;Schonnop et al., 2016). ...
Sheep farming is a major source of meat in Morocco and plays a key role in the country’s agriculture. This study aims at characterizing the whole-genome diversity and demographic history of the main Moroccan sheep breeds, as well as to identify selection signatures within and between breeds. Whole genome data from 87 individuals representing the five predominant local breeds were used to estimate their level of neutral genetic diversity and to infer the variation of their effective population size over time. In addition, we used two methods to detect selection signatures: either for detecting selective sweeps within each breed separately or by detecting differentially selected regions by contrasting different breeds. We identified hundreds of genomic regions putatively under selection, which related to several biological terms involved in local adaptation or the expression of zootechnical performances such as Growth, UV protection, Cell maturation or Feeding behavior. The results of this study revealed selection signatures in genes that have an important role in traits of interest and increased our understanding of how genetic diversity is distributed in these local breeds. Thus, Moroccan local sheep breeds exhibit both a high genetic diversity and a large set of adaptive variations, and therefore, represent a valuable genetic resource for the conservation of sheep in the context of climate change.
... Up to date, few studies have carried out a mutation analysis in the coding region of MRAP2 [15,[44][45][46]. However, five rare heterozygous variants of in this gene were found in patients with severe early-onset obesity. ...
... However, five rare heterozygous variants of in this gene were found in patients with severe early-onset obesity. No specific endocrine abnormalities were described in these cases [15,45]. In mice, Mrap2 knockout also caused severe obesity at a young age [15]. ...
... Furthermore, one missense mutation (p.Arg125His) was found in two obese children and adolescents from Germany [44]. Similarly, Schonnop et al. [45] have reported three missense mutations (p.Arg125His, p.Ala137Thr and p.Gln174Arg) and two synonymous variants (p.Asn159 = and p.His201 =) from severely obese patients. Only Gln174Arg was predicted to have a potential functional impact by in silico programs and in vitro analyses (slightly reduced MC4R signaling). ...
PurposeMonogenic forms of obesity are caused by single-gene variants which affect the energy homeostasis by increasing food intake and decreasing energy expenditure. Most of these variants result from disruption of the leptin–melanocortin signaling, which can cause severe early-onset obesity and hyperphagia. These mutation have been identified in genes encoding essential proteins to this pathway, including leptin (LEP), melanocortin 2 receptor accessory proteins 2 (MRAP2) and proopiomelanocortin (POMC). We aimed to investigate the prevalence of LEP, MRAP2 and POMC rare variants in severely obese adults, who developed obesity during childhood. To the best of our knowledge, this is the first study screening rare variants of these genes in patients from Brazil.MethodsA total of 122 Brazilian severely obese patients (BMI ≥ 35 kg/m2) were screened for the coding regions of LEP, MRAP2 and POMC by Sanger sequencing. All patients are candidates to the bariatric surgery. Clinical characteristics were described in patients with novel and/or potentially pathogenic variants.ResultsSixteen different variants were identified in these genes, of which two were novel. Among them, one previous variant with potentially deleterious effect in MRAP2 (p.Arg125Cys) was found. In addition, two heterozygous mutations in POMC (p.Phe87Leu and p.Arg90Leu) were predicted to impair protein function. We also observed a POMC homozygous 9 bp insertion (p.Gly99_Ala100insSerSerGly) in three patients. No pathogenic variant was observed in LEP.Conclusion
Our study described for the first time the prevalence of rare potentially pathogenic MRAP2 and POMC variants in a cohort of Brazilian severely obese adults.Level of evidenceLevel V, cross-sectional descriptive study.
... Most (but not all) Mendelian obesity cases are due to deficiency in a gene of the leptin-melanocortin signaling pathway, a major player in the regulation of energy balance (65). Thus far, defects in 16 genes have been identified in monogenic obesity: adenylate cyclase 3 (ADCY3), brain-derived neurotrophic factor (BDNF), dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1B), kinase suppressor of ras 2 (KSR2), leptin (LEP), leptin receptor (LEPR), melanocortin 4 receptor (MC4R), melanocortin-2 receptor accessory protein 2 (MRAP2), nuclear receptor subfamily 0 group B member 2 (NR0B2), neurotrophic receptor tyrosine kinase 2 (NTRK2), proprotein convertase subtilisin/kexin type 1 (PCSK1), proopiomelanocortin (POMC), peroxisome proliferator-activated receptor γ (PPARG), SH2B adaptor protein 1 (SH2B1), SIM BHLH transcription factor 1 (SIM1), and TUB bipartite transcription factor (TUB) (66,67). Table 2 provides a list of genes most frequently identified as causal of Mendelian obesity along with their prevalence and notes on phenotypic manifestations (68). ...
There is a genetic component to human obesity that accounts for 40% to 50% of the variability in body weight status but that is lower among normal weight individuals (about 30%) and substantially higher in the subpopulation of individuals with obesity and severe obesity (about 60%-80%). The appreciation that heritability varies across classes of BMI represents an important advance. After controlling for BMI, ectopic fat and fat distribution traits are characterized by heritability levels ranging from 30% to 55%. Defects in at least 15 genes are the cause of monogenic obesity cases, resulting mostly from deficiencies in the leptin-melanocortin signaling pathway. Approximately two-thirds of the BMI heritability can be imputed to common DNA variants, whereas low-frequency and rare variants explain the remaining fraction. Diminishing allele effect size is observed as the number of obesity-associated variants expands, with most BMI-increasing or -decreasing alleles contributing only a few grams or less to body weight. Obesity-promoting alleles exert minimal effects in normal weight individuals but have larger effects in individuals with a proneness to obesity, suggesting a higher penetrance; however, it is not known whether these larger effect sizes precede obesity or are caused by an obese state. The obesity genetic risk is conditioned by thousands of DNA variants that make genetically based obesity prevention and treatment a major challenge.
