1
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Esteban JJ, Mason JR, Kaminski J, Ramachandran R, Luyt LG. A survey of stapling methods to increase affinity, activity, and stability of ghrelin analogues. RSC Med Chem 2024; 15:254-266. [PMID: 38283230 PMCID: PMC10809362 DOI: 10.1039/d3md00441d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 11/29/2023] [Indexed: 01/30/2024] Open
Abstract
The growth hormone secretagogue receptor (GHSR) is a G protein-coupled receptor which regulates various important physiological and pathophysiological processes in the body such as energy homeostasis, growth hormone secretion and regulation of appetite. As a result, it has been postulated as a potential therapeutic target for the treatment of cancer cachexia and other metabolic disorders, as well as a potential imaging agent target for cancers and cardiovascular diseases. Ghrelin is the primary high affinity endogenous ligand for GHSR and has limited secondary structure in solution, which makes it proteolytically unstable. This inherent instability in ghrelin can be overcome by incorporating helix-inducing staples that stabilize its structure and improve affinity and activity. We present an analysis of different stapling methods at positions 12 and 16 of ghrelin(1-20) analogues with the goal of increasing proteolytic stability and to retain or improve affinity and activity towards the GHSR. Ghrelin(1-20) analogues were modified with a wide range of chemical staples, including a lactam staple, triazole staple, hydrocarbon staple, Glaser staple, and xylene-thioether staple. Once synthesized, the receptor affinity and α-helicity were measured using competitive binding assays and circular dichroism spectroscopy, respectively. Generally, an increase in alpha-helicity using a flexible staple linker led to improved affinity towards GHSR. Ghrelin(1-20) analogues with a lactam, triazole, and hydrocarbon staple resulted in helical analogues with stronger affinity towards GHSR than unstapled ghrelin(1-20), a compound that lacks helical character. Compounds were also investigated for their agonist activity through β-arrestin 1 & 2 recruitment BRET assays and for their metabolic stability through serum stability analysis.
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Affiliation(s)
- Juan J Esteban
- Department of Chemistry, University of Western Ontario 1151 Richmond Street London Ontario N6A 3K7 Canada
| | - Julia R Mason
- Department of Chemistry, University of Western Ontario 1151 Richmond Street London Ontario N6A 3K7 Canada
| | - Jakob Kaminski
- Department of Chemistry, University of Western Ontario 1151 Richmond Street London Ontario N6A 3K7 Canada
| | - Rithwik Ramachandran
- Department of Physiology and Pharmacology, University of Western Ontario 1151 Richmond Street London Ontario N6A 5C1 Canada
| | - Leonard G Luyt
- Department of Chemistry, University of Western Ontario 1151 Richmond Street London Ontario N6A 3K7 Canada
- Departments of Medical Imaging and Oncology, University of Western Ontario 1151 Richmond Street London Ontario N6A 3K7 Canada
- London Regional Cancer Program, Lawson Health Research Institute 800 Commissioners Road East London Ontario N6A 4L6 Canada
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2
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Lalonde T, Shepherd TG, Dhanvantari S, Luyt LG. Stapled ghrelin peptides as fluorescent imaging probes. Pept Sci (Hoboken) 2018. [DOI: 10.1002/pep2.24055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Tyler Lalonde
- Department of Chemistry; University of Western Ontario; London Ontario N6A 5B7 Canada
| | - Trevor G. Shepherd
- London Regional Cancer Program; London Ontario N6A 4L6 Canada
- Department of Obstetrics and Gynecology; University of Western Ontario; London Ontario N6A 5B7 Canada
| | - Savita Dhanvantari
- Imaging Program, Lawson Health Research Institute; London Ontario N6A 4V2 Canada
- Department of Medical Biophysics; University of Western Ontario; London Canada
- Department of Pathology; University of Western Ontario; London Canada
- Department of Laboratory Medicine; University of Western Ontario; London Canada
| | - Leonard G. Luyt
- Department of Chemistry; University of Western Ontario; London Ontario N6A 5B7 Canada
- London Regional Cancer Program; London Ontario N6A 4L6 Canada
- Department of Oncology; University of Western Ontario; London Ontario N6A 5B7 Canada
- Department of Medical Imaging; University of Western Ontario; London Ontario N6A 5B7 Canada
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3
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Lufrano D, Trejo SA, Llovera RE, Salgueiro M, Fernandez G, Martínez Damonte V, González Flecha FL, Raingo J, Ermácora MR, Perelló M. Ghrelin binding to serum albumin and its biological impact. Mol Cell Endocrinol 2016; 436:130-40. [PMID: 27431015 DOI: 10.1016/j.mce.2016.07.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 06/08/2016] [Accepted: 07/14/2016] [Indexed: 01/07/2023]
Abstract
Ghrelin is an octanoylated peptide hormone that plays a key role in the regulation of the body weight and glucose homeostasis. In plasma, ghrelin circulates bound to larger proteins whose identities are partially established. Here, we used size exclusion chromatography, mass spectrometry and isothermal titration microcalorimetry to show that ghrelin interacts with serum albumin. Furthermore, we found that such interaction displays an estimated dissociation constant (KD) in the micromolar range and involves albumin fatty-acid binding sites as well as the octanoyl moiety of ghrelin. Notably, albumin-ghrelin interaction reduces the spontaneous deacylation of the hormone. Both in vitro experiments-assessing ghrelin ability to inhibit calcium channels-and in vivo studies-evaluating ghrelin orexigenic effects-indicate that the binding to albumin affects the bioactivity of the hormone. In conclusion, our results suggest that ghrelin binds to serum albumin and that this interaction impacts on the biological activity of the hormone.
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Affiliation(s)
- Daniela Lufrano
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina
| | - Sebastián A Trejo
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina; Servei de Proteòmica i Biologia Estructural, Universitat Autònoma de Barcelona, Spain
| | - Ramiro E Llovera
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina
| | - Mariano Salgueiro
- Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Argentina
| | - Gimena Fernandez
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina
| | | | - F Luis González Flecha
- Instituto de Química y Fisicoquímica Biológicas, Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
| | - Jesica Raingo
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina
| | - Mario R Ermácora
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina; Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Argentina
| | - Mario Perelló
- Instituto Multidisciplinario de Biología Celular, Conicet, Argentina.
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4
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Satou M, Kaiya H, Nishi Y, Shinohara A, Kawada SI, Miyazato M, Kangawa K, Sugimoto H. Mole ghrelin: cDNA cloning, gene expression, and diverse molecular forms in Mogera imaizumii. Gen Comp Endocrinol 2016; 232:199-210. [PMID: 27102942 DOI: 10.1016/j.ygcen.2016.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 03/14/2016] [Accepted: 04/16/2016] [Indexed: 11/28/2022]
Abstract
Here, we describe cDNA cloning and purification of the ghrelin gene sequences and ghrelin peptides from the Japanese true mole, Mogera imaizumii. The gene spans >2.9kbp, has four exons and three introns, and shares structural similarity with those of terrestrial animals. Mature mole ghrelin peptide was predicted to be 28 amino acids long (GSSFLSPEHQKVQQRKESKKPPSKPQPR) and processed from a prepropeptide of 116 amino acids. To further elucidate molecular characteristics, we purified ghrelin peptides from mole stomach. By mass spectrometry, we found that the mole ghrelin peptides had higher ratios of the odd-number fatty acids (C9 and C11 as much as C8) attached to the third serine residue than other vertebrate ghrelin. Truncated forms of ghrelins such as [1-27], [1-19], [1-16] and [1-15], and that lacked the 14th glutamine residue (des-Gln14 ghrelin) were produced in the stomach. Marked expression of ghrelin mRNA in lung was observed as in stomach and brain. Phylogenetic analysis indicated that the branch of M. imaizumii has slightly higher dN/dS ratios (the nucleotide substitution rates at non-synonymous and synonymous sites) than did other eulipotyphlans. Peptide length was positively correlated with human ghrelin receptor activation, whereas the length of fatty-acyl chains showed no obvious functional correlation. The basal higher luciferase activities of the 5'-proximal promoter region of mole ghrelin were detected in ghrelin-negative C2C12 cells and hypoxic culture conditions impaired transcriptional activity. These results indicated that moles have acquired diverse species of ghrelin probably through distinctive fatty acid metabolism because of their food preferences. The results provide a gateway to understanding ghrelin metabolism in fossorial animals.
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Affiliation(s)
- Motoyasu Satou
- Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan
| | - Hiroyuki Kaiya
- Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan
| | - Yoshihiro Nishi
- Department of Physiology, Kurume University School of Medicine, Kurume, Fukuoka 830-0011, Japan
| | - Akio Shinohara
- Division of Bio-resources, Department of Biotechnology, Frontier Science Research Center, University of Miyazaki, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan
| | - Shin-Ichiro Kawada
- Department of Zoology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
| | - Mikiya Miyazato
- Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan
| | - Kenji Kangawa
- Department of Biochemistry, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan
| | - Hiroyuki Sugimoto
- Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan.
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5
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Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin. PLoS One 2015; 10:e0122444. [PMID: 25803439 PMCID: PMC4372444 DOI: 10.1371/journal.pone.0122444] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 02/11/2015] [Indexed: 12/18/2022] Open
Abstract
The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide’s secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide’s positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8–17 form an α-helix, while residues 21–23 and 26–27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.
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6
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Delporte C. Structure and physiological actions of ghrelin. SCIENTIFICA 2013; 2013:518909. [PMID: 24381790 PMCID: PMC3863518 DOI: 10.1155/2013/518909] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/10/2013] [Indexed: 05/30/2023]
Abstract
Ghrelin is a gastric peptide hormone, discovered as being the endogenous ligand of growth hormone secretagogue receptor. Ghrelin is a 28 amino acid peptide presenting a unique n-octanoylation modification on its serine in position 3, catalyzed by ghrelin O-acyl transferase. Ghrelin is mainly produced by a subset of stomach cells and also by the hypothalamus, the pituitary, and other tissues. Transcriptional, translational, and posttranslational processes generate ghrelin and ghrelin-related peptides. Homo- and heterodimers of growth hormone secretagogue receptor, and as yet unidentified receptors, are assumed to mediate the biological effects of acyl ghrelin and desacyl ghrelin, respectively. Ghrelin exerts wide physiological actions throughout the body, including growth hormone secretion, appetite and food intake, gastric secretion and gastrointestinal motility, glucose homeostasis, cardiovascular functions, anti-inflammatory functions, reproductive functions, and bone formation. This review focuses on presenting the current understanding of ghrelin and growth hormone secretagogue receptor biology, as well as the main physiological effects of ghrelin.
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Affiliation(s)
- Christine Delporte
- Laboratory of Pathophysiological and Nutritional Biochemistry, Université Libre de Bruxelles, 808 Route de Lennik, Bat G/E-CP611, 1070 Brussels, Belgium
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7
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Coimbra JT, Sousa SF, Fernandes PA, Rangel M, Ramos MJ. Biomembrane simulations of 12 lipid types using the general amber force field in a tensionless ensemble. J Biomol Struct Dyn 2013; 32:88-103. [DOI: 10.1080/07391102.2012.750250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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8
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De Ricco R, Valensin D, Gaggelli E, Valensin G. Conformation propensities of des-acyl-ghrelin as probed by CD and NMR. Peptides 2013; 43:62-7. [PMID: 23470254 DOI: 10.1016/j.peptides.2013.02.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 02/20/2013] [Accepted: 02/20/2013] [Indexed: 12/30/2022]
Abstract
Des-acyl-ghrelin is a 28 amino acid peptide secreted by both human and rat stomach. Together with ghrelin and obestatin, it is obtained by post-translational modification of a 117 aminoacid prepropeptide mainly expressed in distinct endocrine cell type in the stomach. Although its receptor has not been unambiguously identified so far, des-acyl-ghrelin is considered one of the strongest antagonists of ghrelin in activating the growth hormone secretagogue receptor (GHS-R). Here the secondary structure of des-acyl-ghrelin in different experimental conditions has been investigated and compared with that of obestatin, a bioactive peptide having similar biological functions. CD and NMR techniques have been combined for gaining the desired conformational features. The obtained structures support a steady alpha-helix structure spanning residues from 7 to 14, very similar to that observed for obestatin at the same experimental conditions, leading to suggest that a similar secondary structure can be associated with the similar biological role.
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Affiliation(s)
- Riccardo De Ricco
- Department of Biotechnology, University of Siena, Via A. Moro 2, 53100 Siena, Italy
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9
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ITP Adjuster 1.0: A New Utility Program to Adjust Charges in the Topology Files Generated by the PRODRG Server. J CHEM-NY 2013. [DOI: 10.1155/2013/803151] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The suitable computation of accurate atomic charges for the GROMACS topology *.itp files of small molecules, generated in the PRODRG server, has been a tricky task nowadays because it does not calculate atomic charges using an ab initio method. Usually additional steps of structure optimization and charges calculation, followed by a tedious manual replacement of atomic charges in the *.itp file, are needed. In order to assist this task, we report here the ITP Adjuster 1.0, a utility program developed to perform the replacement of the PRODRG charges in the *.itp files of small molecules by ab initio charges.
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10
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Granata R, Settanni F, Julien M, Nano R, Togliatto G, Trombetta A, Gallo D, Piemonti L, Brizzi MF, Abribat T, van Der Lely AJ, Ghigo E. Des-acyl ghrelin fragments and analogues promote survival of pancreatic β-cells and human pancreatic islets and prevent diabetes in streptozotocin-treated rats. J Med Chem 2012; 55:2585-96. [PMID: 22352743 DOI: 10.1021/jm201223m] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Des-acyl ghrelin, although devoid of binding to ghrelin receptor (GRLN), exerts many biological effects, including regulation of glucose and lipid metabolism. Indeed, des-acyl ghrelin promotes pancreatic β-cell and human islet cell survival and prevents diabetes in streptozotocin (STZ) treated rats. We investigated whether des-acyl ghrelin fragments excluding serine(3), which is essential for binding to GRLN, would display similar actions. Among the different compounds tested, des-acyl ghrelin((6-13)) and des-acyl ghrelin((6-13)) with alanine substitutions or cyclization, but not with d-amino acid substitutions, showed the best survival effect, similar to des-acyl ghrelin. Des-acyl ghrelin((6-13)) even prevented diabetes in STZ-treated rats and protected human circulating angiogenic cells from oxidative stress and senescence, similar to des-acyl ghrelin. These results suggest that not only full-length des-acyl ghrelin but also short des-acyl ghrelin fragments have clear beneficial effects on several tissues in vitro and in vivo.
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Affiliation(s)
- Riccarda Granata
- Laboratory of Molecular and Cellular Endocrinology, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy.
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Morozumi N, Sato S, Yoshida S, Yamaki A, Furuya M, Inomata N, Ohnuma N, Minamitake Y, Ohsuye K, Kangawa K. A new strategy for metabolic stabilization of motilin using the C-terminal part of ghrelin. Peptides 2012; 33:279-84. [PMID: 22286034 DOI: 10.1016/j.peptides.2012.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 01/11/2012] [Accepted: 01/11/2012] [Indexed: 11/23/2022]
Abstract
Ghrelin consists of 28 amino acid residues with an octanoyl modification at the third serine residue. Recently we have found that the C-terminal part of ghrelin protects the ester bond of 3-octanoyled serine from plasma esterases and plays the essential role to prolong the plasma half-life and to show its biological activity in vivo. In the present study, we researched whether the C-terminal part of ghrelin has a potential to prolong the plasma half-life of motilin, by comparing the pharmacokinetics of various chimeric peptides of ghrelin and motilin. Motilin is another gastro-intestinal peptide hormone related with ghrelin structurally, binding to the same family of G protein-coupled receptors. Chimeric peptides were designed to be composed of motilin(1-12) fragment, the active core binding to the motilin receptor, GPR38, and C-terminal part of ghrelin. The modification of motilin(1-12) fragment by C-terminal part of ghrelin hardly influenced its agonist activity to GPR38 and almost all these chimeric peptides showed more than two times longer plasma half-lives than motilin in rats. From the relationship between structures of chimeric peptides and their corresponding plasma half-lives, the mid-region of ghrelin rich in basic amino acids ((15)RKESKK(20)) was considered to be the most important in prolonging the plasma half-life of motilin. The deletion of these fragments or replacement of 17th glutamic acid with a neutral amino acid resulted in short plasma half-lives. In conclusion, our data suggested that the C-terminal part of ghrelin has a potential to improve the biokinetics of motilin probably by a metabolic stabilizing effect.
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Affiliation(s)
- Naomi Morozumi
- Faculty of Pharmacology I, Asubio Pharma Co, Ltd, 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan.
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12
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Zakhari JS, Zorrilla EP, Zhou B, Mayorov AV, Janda KD. Oligoclonal antibody targeting ghrelin increases energy expenditure and reduces food intake in fasted mice. Mol Pharm 2011; 9:281-9. [PMID: 22149064 DOI: 10.1021/mp200376c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ghrelin, an enteric peptide hormone linked to the pathophysiology of obesity has been a therapeutic target of great interest over the past decade. Many research efforts have focused on the antagonism of ghrelin's endogenous receptor GHSR1a, which is found along ascending vagal afferent fibers, as well as in the arcuate nucleus of the hypothalamus. Additionally, peptidic inhibitors of ghrelin O-acyltransferase, the enzyme responsible for the paracrine activation of ghrelin, have recently been studied. Our research has taken an alternative immunological approach, studying both active and passive vaccination as a means to sequester ghrelin in the periphery, with the original discovery in rat of decreased feed efficiency and adiposity, as well as increased metabolic activity. Using our previous hapten designs as a stepping-stone, three monoclonal antibodies (JG2, JG3, and JG4) were procured against ghrelin and tested in vivo. While mAb JG4 had the highest affinity for ghrelin, it failed to attenuate the orexigenic effects of food deprivation on energy metabolism or food intake in mice. However, animals that were administered a combination of JG3:JG4 (termed a doublet) or JG2:JG3:JG4 (termed a triplet) demonstrated higher heat dispersion and rate of respiration (higher CO(2) emission and O(2) consumption) during a 24 h fast refeed. Mice administered the triplet cocktail of JG2:JG3:JG4 also demonstrated decreased food intake upon refeeding as compared to control animals. Recently, Lu and colleagues reported that a passive approach using a single, high affinity N-terminally directed monoclonal antibody did not abrogate the effects of endogenous ghrelin. Our current report corroborates this finding, yet, refutes that a monoclonal antibody approach cannot be efficacious. Rather, we find that a multiple monoclonal antibody (oligoclonal) approach can reproduce the underlying logic to previously reported efficacies using active vaccinations.
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Affiliation(s)
- Joseph S Zakhari
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
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13
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Liu B, Garcia EA, Korbonits M. Genetic studies on the ghrelin, growth hormone secretagogue receptor (GHSR) and ghrelin O-acyl transferase (GOAT) genes. Peptides 2011; 32:2191-207. [PMID: 21930173 DOI: 10.1016/j.peptides.2011.09.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 09/03/2011] [Accepted: 09/06/2011] [Indexed: 12/15/2022]
Abstract
Ghrelin is a 28 amino acid peptide hormone that is produced both centrally and peripherally. Regulated by the ghrelin O-acyl transferase enzyme, ghrelin exerts its action through the growth hormone secretagogue receptor, and is implicated in a diverse range of physiological processes. These implications have placed the ghrelin signaling pathway at the center of a large number of candidate gene and genome-wide studies which aim to identify the genetic basis of human heterogeneity. In this review we summarize the available data on the genetic variability of ghrelin, its receptor and its regulatory enzyme, and their association with obesity, stature, type 2 diabetes, cardiovascular disease, eating disorders, and reward seeking behavior.
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Affiliation(s)
- Boyang Liu
- Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
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14
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Großauer J, Kosol S, Schrank E, Zangger K. The peptide hormone ghrelin binds to membrane-mimetics via its octanoyl chain and an adjacent phenylalanine. Bioorg Med Chem 2010; 18:5483-8. [PMID: 20621491 PMCID: PMC3038380 DOI: 10.1016/j.bmc.2010.06.062] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/15/2010] [Accepted: 06/16/2010] [Indexed: 02/01/2023]
Abstract
The peptide hormone ghrelin, which is the natural ligand of the membrane-bound growth hormone secretagogue receptor (GHS-R), regulates overall body and cell growth, energy homeostasis, carbohydrate, protein and lipid metabolism and water electrolyte balance. It contains an O-acyl linked octanoyl group on Ser3 and is the only peptide known to contain such a modification. Using solution state NMR spectroscopy and ultrafiltration we found that human ghrelin binds to membrane-mimetic environments via its octanoyl group as well as the aromatic moiety of Phe4. Relaxation enhancements in a paramagnetic environment reveal that both the octanoyl group on Ser3 and the aromatic group on Phe4 are inserted deep into the hydrophobic core of phosphocholine assemblies while the remaining peptide is freely mobile in solution. In contrast, no binding was observed for des-octanoyl ghrelin. Thus, the octanoyl chain, together with the Phe4 aromatic group of ghrelin, functions as a membrane anchor. Our results are in parallel with the previous finding that a bulky hydrophobic group on Ser3 and Phe4 of ghrelin are necessary for its function and thus indicate that membrane-binding is essential for ghrelin function.
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Affiliation(s)
| | | | | | - Klaus Zangger
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria
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15
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Staes E, Absil PA, Lins L, Brasseur R, Deleu M, Lecouturier N, Fievez V, Rieux AD, Mingeot-Leclercq MP, Raussens V, Préat V. Acylated and unacylated ghrelin binding to membranes and to ghrelin receptor: towards a better understanding of the underlying mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2102-13. [PMID: 20637180 DOI: 10.1016/j.bbamem.2010.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 07/02/2010] [Accepted: 07/06/2010] [Indexed: 10/19/2022]
Abstract
The O-octanoylation of human ghrelin is a natural post-translational modification that enhances its binding to model membranes and could potentially play a central role in ghrelin biological activities. Here, we aimed to clarify the mechanisms that drive ghrelin to the membrane and hence to its receptor that mediates most of its endocrinological effects. As the acylation enhances ghrelin lipophilicity and that ghrelin contains many basic residues, we examined the electrostatic attraction and/or hydrophobic interactions with membranes. Using various liposomes and buffer conditions in binding, zeta potential and isothermal titration calorimetry studies, we found that whereas acylated and unacylated ghrelin were both electrostatically attracted towards the membrane, only acylated ghrelin penetrated into the headgroup and the lipid backbone regions of negatively charged membranes. The O-acylation induced a 120-fold increase in ghrelin local concentration in the membrane. However, acylated ghrelin did not deeply penetrate the membrane nor did it perturb its organisation. Conformational studies by circular dichroism and attenuated total reflection Fourier transformed infrared as well as in silico modelling revealed that both forms of ghrelin mainly adopted the same structure in aqueous, micellar and bilayer environments even though acylated ghrelin structure is slightly more α-helical in a lipid bilayer environment. Altogether our results suggest that membrane acts as a "catalyst" in acylated ghrelin binding to the ghrelin receptor and hence could explain why acylated and unacylated ghrelin are both full agonists of this receptor but in the nanomolar and micromolar range, respectively.
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Affiliation(s)
- Edith Staes
- Université catholique de Louvain, Unité de Pharmacie Galénique, 1200 Brussels, Belgium.
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Interaction between ghrelin and the ghrelin receptor (GHS-R1a), a NMR study using living cells. Bioorg Med Chem 2010; 18:1583-90. [DOI: 10.1016/j.bmc.2010.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 12/24/2009] [Accepted: 01/02/2010] [Indexed: 02/02/2023]
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Floquet N, M'Kadmi C, Perahia D, Gagne D, Bergé G, Marie J, Banères JL, Galleyrand JC, Fehrentz JA, Martinez J. Activation of the ghrelin receptor is described by a privileged collective motion: a model for constitutive and agonist-induced activation of a sub-class A G-protein coupled receptor (GPCR). J Mol Biol 2009; 395:769-84. [PMID: 19782690 DOI: 10.1016/j.jmb.2009.09.051] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 09/18/2009] [Accepted: 09/20/2009] [Indexed: 10/20/2022]
Abstract
Three homology models of the human ghrelin receptor (GHS-R1a) have been generated from the available X-ray structures of rhodopsin (RHO model), opsin (OPS model) and beta-2 adrenergic receptor (B2 model). The latter was used as a starting point for combined molecular dynamics simulation (MDS) and full atom normal modes analysis (NMA). A low-frequency normal mode (mode 16) perfectly reproduced the intracellular motions observed between B2 and RHO models; in the opposite direction along the same mode, the generated structures are closer to the OPS model, suggesting a direct link with GHS-R1a activation. This was in agreement with motions of the seven transmembranous segments, increase of the solvent accessibility of the 140-ERY-142 sequence, and flip of the Trp276 (C WLP) residue, some features related to GPCRs activation. According to our model, His280 was proposed to stabilize Trp276 in the active state; this was verified by site-directed mutagenesis and biochemical characterization of the resulting H280A and H280S mutants, which were fully functional but sharing an important decrease of their basal activities. Docking performed with short ghrelin derivatives Gly-Ser-Ser ([octa])-Phe-NH (2) and Gly-Ser-Ser ([octa])-Phe-Leu-NH (2) allowed the identification of a robust position of these peptides in the active site of the receptor. This model was refined by MDS and validated by docking experiments performed on a set of 55 ghrelin receptor ligands based on the 1,2,4- triazole scaffold. Finally, NMA performed on the obtained peptide-receptor complex suggested stabilization of the Trp276 residue and of the whole receptor in the active state, preventing the motion observed along mode 16 computed for the unbound receptor. Our results show that NMA offers a powerful approach to study the conformational diversity and the activation mechanism of GPCRs.
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Affiliation(s)
- Nicolas Floquet
- Institut des Biomolécules Max Mousseron (I.B.M.M.), CNRS UMR5247 - Université Montpellier 1 - Université Montpellier 2, Faculté de Pharmacie, 15 avenue Charles Flahault, B.P. 14 491, 34093 Montpellier Cedex 5, France.
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Emperador A, Meyer T, Orozco M. United-Atom Discrete Molecular Dynamics of Proteins Using Physics-Based Potentials. J Chem Theory Comput 2008; 4:2001-10. [DOI: 10.1021/ct8003832] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Agustí Emperador
- Joint IRB-BSC research program in Computational Biology, Institute for Research in Biomedicine (IRB), Josep Samitier 1-5, Barcelona 08028, Spain, Barcelona Supercomputing Centre (BSC), Jordi Girona 29, Barcelona 08034, Spain, Departament de Bioquímica i Biología Molecular, Facultat de Biología, Universitat de Barcelona, Avgda Diagonal 645, Barcelona 08028, Spain, and National Institute of Bioinformatics, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona 08028, Spain
| | - Tim Meyer
- Joint IRB-BSC research program in Computational Biology, Institute for Research in Biomedicine (IRB), Josep Samitier 1-5, Barcelona 08028, Spain, Barcelona Supercomputing Centre (BSC), Jordi Girona 29, Barcelona 08034, Spain, Departament de Bioquímica i Biología Molecular, Facultat de Biología, Universitat de Barcelona, Avgda Diagonal 645, Barcelona 08028, Spain, and National Institute of Bioinformatics, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona 08028, Spain
| | - Modesto Orozco
- Joint IRB-BSC research program in Computational Biology, Institute for Research in Biomedicine (IRB), Josep Samitier 1-5, Barcelona 08028, Spain, Barcelona Supercomputing Centre (BSC), Jordi Girona 29, Barcelona 08034, Spain, Departament de Bioquímica i Biología Molecular, Facultat de Biología, Universitat de Barcelona, Avgda Diagonal 645, Barcelona 08028, Spain, and National Institute of Bioinformatics, Parc Científic de Barcelona, Josep Samitier 1-5, Barcelona 08028, Spain
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Dehlin E, Liu J, Yun SH, Fox E, Snyder S, Gineste C, Willingham L, Geysen M, Gaylinn BD, Sando JJ. Regulation of ghrelin structure and membrane binding by phosphorylation. Peptides 2008; 29:904-11. [PMID: 18343535 PMCID: PMC2413428 DOI: 10.1016/j.peptides.2008.02.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 01/31/2008] [Accepted: 02/04/2008] [Indexed: 12/15/2022]
Abstract
The peptide hormone ghrelin requires Ser-3 acylation for receptor binding, orexigenic and anti-inflammatory effects. Functions of desacylghrelin are less well understood. In vitro kinase assays reveal that the evolutionarily conserved Ser-18 in the basic C-terminus is an excellent substrate for protein kinase C. Circular dichroism reveals that desacylghrelin is approximately 12% helical in aqueous solution and approximately 50% helical in trifluoroethanol. Ser-18-phosphorylation, Ser-18-Ala substitution, or Ser-3-acylation reduces the helical character in trifluoroethanol to approximately 24%. Both ghrelin and desacylghrelin bind to phosphatidylcholine:phosphatidylserine sucrose-loaded vesicles in a phosphatidylserine-dependent manner. Phosphoghrelin and phosphodesacylghrelin show greatly diminished phosphatidylserine-dependent binding. These results are consistent with binding of ghrelin and desacylghrelin to acidic lipids via the basic face of an amphipathic helix with Ser-18 phosphorylation disrupting both helical character and membrane binding.
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Affiliation(s)
- Eva Dehlin
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908
| | - Jianhua Liu
- Department of Medicine Division of Endocrinology, University of Virginia, Charlottesville, VA 22908
| | - Samuel H. Yun
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908
| | - Elizabeth Fox
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908
| | - Sandra Snyder
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908
| | - Cyrille Gineste
- Department of Chemistry, University of Virginia, Charlottesville, VA 22908
| | - Leslie Willingham
- Department of Chemistry, University of Virginia, Charlottesville, VA 22908
| | - Mario Geysen
- Department of Chemistry, University of Virginia, Charlottesville, VA 22908
| | - Bruce D. Gaylinn
- Department of Medicine Division of Endocrinology, University of Virginia, Charlottesville, VA 22908
| | - Julianne J. Sando
- Department of Anesthesiology, University of Virginia, Charlottesville, VA 22908
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Vos WL, Vermeer LS, Hemminga MA. Conformation of a peptide encompassing the proton translocation channel of vacuolar H(+)-ATPase. Biophys J 2007; 92:138-46. [PMID: 17040980 PMCID: PMC1697854 DOI: 10.1529/biophysj.106.089854] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Accepted: 09/14/2006] [Indexed: 11/18/2022] Open
Abstract
The structural properties of a crucial transmembrane helix for proton translocation in vacuolar ATPase are studied using double site-directed spin-labeling combined with electron spin resonance (ESR) (or electron paramagnetic resonance) and circular dichroism spectroscopy in sodium dodecyl sulfate micelles. For this purpose, we use a synthetic peptide derived from transmembrane helix 7 of subunit a from the yeast Saccharomyces cerevisiae vacuolar proton-translocating ATPase that contains two natural cysteine residues suitable for spin-labeling. The interspin distance is calculated using a second-moment analysis of the methanethiosulfonate spin-label ESR spectra at 150 K. Molecular dynamics simulation is used to study the effect of the side-chain dynamics and backbone dynamics on the interspin distance. Based on the combined results from ESR, circular dichroism, and molecular dynamics simulation we conclude that the peptide forms a dynamic alpha-helix. We discuss this finding in the light of current models for proton translocation. A novel role for a buried charged residue (H729) is proposed.
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Affiliation(s)
- Werner L Vos
- Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands
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