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Neumann J, Hofmann B, Dhein S, Gergs U. Cardiac Roles of Serotonin (5-HT) and 5-HT-Receptors in Health and Disease. Int J Mol Sci 2023; 24:4765. [PMID: 36902195 PMCID: PMC10003731 DOI: 10.3390/ijms24054765] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 03/06/2023] Open
Abstract
Serotonin acts solely via 5-HT4-receptors to control human cardiac contractile function. The effects of serotonin via 5-HT4-receptors lead to positive inotropic and chronotropic effects, as well as arrhythmias, in the human heart. In addition, 5-HT4-receptors may play a role in sepsis, ischaemia, and reperfusion. These presumptive effects of 5-HT4-receptors are the focus of the present review. We also discuss the formation and inactivation of serotonin in the body, namely, in the heart. We identify cardiovascular diseases where serotonin might play a causative or additional role. We address the mechanisms which 5-HT4-receptors can use for cardiac signal transduction and their possible roles in cardiac diseases. We define areas where further research in this regard should be directed in the future, and identify animal models that might be generated to this end. Finally, we discuss in what regard 5-HT4-receptor agonists or antagonists might be useful drugs that could enter clinical practice. Serotonin has been the target of many studies for decades; thus, we found it timely to summarise our current knowledge here.
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Affiliation(s)
- Joachim Neumann
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany
| | - Britt Hofmann
- Cardiac Surgery, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany
| | - Stefan Dhein
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Universität Leipzig, D-04109 Leipzig, Germany
| | - Ulrich Gergs
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany
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Recke A, Regensburger AK, Weigold F, Müller A, Heidecke H, Marschner G, Hammers CM, Ludwig RJ, Riemekasten G. Autoantibodies in Serum of Systemic Scleroderma Patients: Peptide-Based Epitope Mapping Indicates Increased Binding to Cytoplasmic Domains of CXCR3. Front Immunol 2018; 9:428. [PMID: 29623076 PMCID: PMC5874968 DOI: 10.3389/fimmu.2018.00428] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/16/2018] [Indexed: 12/30/2022] Open
Abstract
Systemic sclerosis (SSc) is a severe chronic autoimmune disease with high morbidity and mortality. Sera of patients with SSc contain a large variety of autoantibody (aab) reactivities. Among these are functionally active aab that bind to G protein-coupled receptors (GPCR) such as C-X-C motif chemokine receptor 3 (CXCR3) and 4 (CXCR4). Aab binding to the N-terminal portion of these two GPCRs have been shown to be associated with slower disease progression in SSc, especially deterioration of lung function. Aabs binding to GPCRs exhibit functional activities by stimulating or inhibiting GPCR signaling. The specific functional activity of aabs crucially depends on the epitopes they bind to. To identify the location of important epitopes on CXCR3 recognized by aabs from SSc patients, we applied an array of 36 overlapping 18-20mer peptides covering the entire CXCR3 sequence, comparing epitope specificity of SSc patient sera (N = 32, with positive reactivity with CXCR3) to healthy controls (N = 30). Binding of SSc patient and control sera to these peptides was determined by ELISA. Using a Bayesian model approach, we found increased binding of SSc patient sera to peptides corresponding to intracellular epitopes within CXCR3, while the binding signal to extracellular portions of CXCR3 was found to be reduced. Experimentally determined epitopes showed a good correspondence to those predicted by the ABCpred tool. To verify these results and to translate them into a novel diagnostic ELISA, we combined the peptides that represent SSc-associated epitopes into a single ELISA and evaluated its potential to discriminate SSc patients (N = 31) from normal healthy controls (N = 47). This ELISA had a sensitivity of 0.61 and a specificity of 0.85. Our data reveals that SSc sera preferentially bind intracellular epitopes of CXCR3, while an extracellular epitope in the N-terminal domain that appears to be target of aabs in healthy individuals is not bound by SSc sera. Based upon our results, we could devise a novel ELISA concept that may be helpful for monitoring of SSc patients.
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Affiliation(s)
- Andreas Recke
- Department of Dermatology, University of Lübeck, Lübeck, Germany.,Lübeck Institute of Dermatological Research, University of Lübeck, Lübeck, Germany
| | | | - Florian Weigold
- Department of Rheumatology and Clinical Immunology, Charité University Hospital, Berlin, Germany
| | - Antje Müller
- Department of Rheumatology, University of Lübeck, Lübeck, Germany
| | | | | | | | - Ralf J Ludwig
- Lübeck Institute of Dermatological Research, University of Lübeck, Lübeck, Germany
| | - Gabriela Riemekasten
- Department of Rheumatology, University of Lübeck, Lübeck, Germany.,Priority Area Asthma & Allergy, Research Center Borstel, Airway Research Center North (ARCN), German Center for Lung Research (DZL), Borstel, Germany
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Spohn SN, Bianco F, Scott RB, Keenan CM, Linton AA, O’Neill CH, Bonora E, Dicay M, Lavoie B, Wilcox RL, MacNaughton WK, De Giorgio R, Sharkey KA, Mawe GM. Protective Actions of Epithelial 5-Hydroxytryptamine 4 Receptors in Normal and Inflamed Colon. Gastroenterology 2016; 151:933-944.e3. [PMID: 27480173 PMCID: PMC5159265 DOI: 10.1053/j.gastro.2016.07.032] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 06/16/2016] [Accepted: 07/06/2016] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS The 5-hydroxytryptamine receptor 4 (5-HT4R or HTR4) is expressed in the colonic epithelium but little is known about its functions there. We examined whether activation of colonic epithelial 5-HT4R protects colons of mice from inflammation. METHODS The 5-HT4R agonist tegaserod (1 mg/kg), the 5-HT4R antagonist GR113808 (1 mg/kg), or vehicle (control) were delivered by enema to wild-type or 5-HT4R knockout mice at the onset of, or during, active colitis, induced by administration of dextran sodium sulfate or trinitrobenzene sulfonic acid. Inflammation was measured using the colitis disease activity index and by histologic analysis of intestinal tissues. Epithelial proliferation, wound healing, and resistance to oxidative stress-induced apoptosis were assessed, as was colonic motility. RESULTS Rectal administration of tegaserod reduced the severity of colitis compared with mice given vehicle, and accelerated recovery from active colitis. Rectal tegaserod did not improve colitis in 5-HT4R knockout mice, and intraperitoneally administered tegaserod did not protect wild-type mice from colitis. Tegaserod increased proliferation of crypt epithelial cells. Stimulation of 5-HT4R increased Caco-2 cell migration and reduced oxidative stress-induced apoptosis; these actions were blocked by co-administration of the 5-HT4R antagonist GR113808. In noninflamed colons of wild-type mice not receiving tegaserod, inhibition of 5-HT4Rs resulted in signs of colitis within 3 days. In these mice, epithelial proliferation decreased and bacterial translocation to the liver and spleen was detected. Daily administration of tegaserod increased motility in inflamed colons of guinea pigs and mice, whereas administration of GR113808 disrupted motility in animals without colitis. CONCLUSIONS 5-HT4R activation maintains motility in healthy colons of mice and guinea pigs, and reduces inflammation in colons of mice with colitis. Agonists might be developed as treatments for patients with inflammatory bowel diseases.
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Affiliation(s)
| | - Francesca Bianco
- Department of Veterinary Medical Sciences,Department of Medical and Surgical Sciences, University of Bologna, Italy
| | | | - Catherine M. Keenan
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada,Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | | | | | - Elena Bonora
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - Michael Dicay
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | - Brigitte Lavoie
- Neurological Sciences, University of Vermont, Burlington, VT
| | | | - Wallace K. MacNaughton
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | - Roberto De Giorgio
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - Keith A. Sharkey
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada,Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada
| | - Gary M. Mawe
- Neurological Sciences, University of Vermont, Burlington, VT
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Peter JC, Zipfel G, Lecourt AC, Bekel A, Hofbauer KG. Antibodies raised against different extracellular loops of the melanocortin-3 receptor affect energy balance and autonomic function in rats. J Recept Signal Transduct Res 2011; 30:444-53. [PMID: 21091037 DOI: 10.3109/10799893.2010.534485] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Melanocortin receptors (MCR) play an important role in the regulation of energy balance and autonomic function. In the present studies, we used active immunization against peptide sequences from the first and the third extracellular loop (EL1 and EL3) of the MC3R to generate selective antibodies (Abs) against this MCR subtype in rats. Immunization with the EL1 peptide resulted in Abs that enhanced the effects of the endogenous ligand α-melanocyte-stimulating hormone (α-MSH), whereas immunization with the EL3 peptide resulted in Abs acting as non-competitive antagonists. The phenotype of immunized rats chronically instrumented with telemetry transducers was studied under four different conditions: a high-fat diet was followed by standard lab chow, by fasting, and finally by an intraperitoneal injection of lipopolysaccharide (LPS). Under high-fat diet, food intake and body weight were higher in the EL3 than in the EL1 or the control group. Blood pressure was increased in EL3 rats and locomotor activity was reduced. Plasma concentrations of triglycerides, insulin, and leptin tended to rise in the EL3 group. After switching to standard lab chow, the EL1 group showed a small significant increase in blood pressure that was more pronounced and associated with an increase in heart rate during food restriction. No differences between the EL1 or the EL3 group were observed after LPS injection. These results show that immunization against the MC3R resulted in the production of Abs with positive or negative allosteric properties. The presence of such Abs induced small changes in metabolic and cardiovascular parameters.
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Investigations on 5-HT4 Receptor Expression and Effects of Tegaserod on Human Platelet Aggregation In Vitro. Am J Ther 2010; 17:543-52. [DOI: 10.1097/mjt.0b013e3181b63f21] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Derangeon M, Bozon V, Defamie N, Peineau N, Bourmeyster N, Sarrouilhe D, Argibay JA, Hervé JC. 5-HT4 and 5-HT2 receptors antagonistically influence gap junctional coupling between rat auricular myocytes. J Mol Cell Cardiol 2009; 48:220-9. [PMID: 19615378 DOI: 10.1016/j.yjmcc.2009.07.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 06/15/2009] [Accepted: 07/03/2009] [Indexed: 01/20/2023]
Abstract
5-hydroxytryptamine-4 (5-HT(4)) receptors have been proposed to contribute to the generation of atrial fibrillation in human atrial myocytes, but it is unclear if these receptors are present in the hearts of small laboratory animals (e.g. rat). In this study, we examined presence and functionality of 5-HT(4) receptors in auricular myocytes of newborn rats and their possible involvement in regulation of gap junctional intercellular communication (GJIC, responsible for the cell-to-cell propagation of the cardiac excitation). Western-blotting assays showed that 5-HT(4) receptors were present and real-time RT-PCR analysis revealed that 5-HT(4b) was the predominant isoform. Serotonin (1 microM) significantly reduced cAMP concentration unless a selective 5-HT(4) inhibitor (GR113808 or ML10375, both 1 microM) was present. Serotonin also reduced the amplitude of L-type calcium currents and influenced the strength of GJIC without modifying the phosphorylation profiles of the different channel-forming proteins or connexins (Cxs), namely Cx40, Cx43 and Cx45. GJIC was markedly increased when serotonin exposure occurred in presence of a 5-HT(4) inhibitor but strongly reduced when 5-HT(2A) and 5-HT(2B) receptors were inhibited, showing that activation of these receptors antagonistically regulated GJIC. The serotoninergic response was completely abolished when 5-HT(4), 5-HT(2A) and 5-HT(2B) were simultaneously inhibited. A 24 h serotonin exposure strongly reduced Cx40 expression whereas Cx45 was less affected and Cx43 still less. In conclusion, this study revealed that 5-HT(4) (mainly 5-HT(4b)), 5-HT(2A) and 5-HT(2B) receptors coexisted in auricular myocytes of newborn rat, that 5-HT(4) activation reduced cAMP concentration, I(Ca)(L) and intercellular coupling whereas 5-HT(2A) or 5-HT(2B) activation conversely enhanced GJIC.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Aminobenzoates/pharmacology
- Animals
- Animals, Newborn
- Blotting, Western
- Cells, Cultured
- Connexins/metabolism
- Gap Junctions/drug effects
- Gap Junctions/metabolism
- Heart Atria/cytology
- In Vitro Techniques
- Indoles/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Patch-Clamp Techniques
- Phosphorylation/drug effects
- Piperidines/pharmacology
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT2A/genetics
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptor, Serotonin, 5-HT2B/genetics
- Receptor, Serotonin, 5-HT2B/metabolism
- Receptor, Serotonin, 5-HT2C/genetics
- Receptor, Serotonin, 5-HT2C/metabolism
- Receptors, Serotonin, 5-HT4/genetics
- Receptors, Serotonin, 5-HT4/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Serotonin/pharmacology
- Serotonin 5-HT2 Receptor Antagonists
- Serotonin 5-HT4 Receptor Antagonists
- Serotonin Agents/pharmacology
- Serotonin Antagonists/pharmacology
- Sulfonamides/pharmacology
- para-Aminobenzoates
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Affiliation(s)
- Mickaël Derangeon
- UMR CNRS 6542, Physiologie des Cellules Cardiaques et Vasculaires, Faculté des Sciences et Techniques, Université de Tours, France
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Gupta A, Heimann AS, Gomes I, Devi LA. Antibodies against G-protein coupled receptors: novel uses in screening and drug development. Comb Chem High Throughput Screen 2009; 11:463-7. [PMID: 18673273 DOI: 10.2174/138620708784911465] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Antibodies are components of the body's humoral immune system that are generated in response to foreign pathogens. Modern biomedical research has employed these very specific and efficient molecules designed by nature in the diagnosis of diseases, localization of gene products as well as in the rapid screening of targets for drug discovery and testing. In addition, the introduction of antibodies with fluorescent or enzymatic tags has significantly contributed to advances in imaging and microarray technology, which are revolutionizing disease research and the search for effective therapeutics. More recently antibodies have been used in the isolation of dimeric G protein-coupled receptor (GPCR) complexes. In this review, we discuss antibodies as powerful research tools for studying GPCRs, and their potential to be developed as drugs themselves.
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Affiliation(s)
- Achla Gupta
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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By Y, Durand-Gorde JM, Condo J, Lejeune PJ, Mallet B, Carayon P, Guieu R, Ruf J. Production of an agonist-like monoclonal antibody to the human A2A receptor of adenosine for clinical use. Mol Immunol 2008; 46:400-5. [PMID: 19041138 DOI: 10.1016/j.molimm.2008.10.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 10/13/2008] [Accepted: 10/14/2008] [Indexed: 10/21/2022]
Abstract
The second extracellular loop of the A(2A) receptor (A(2A)R) of adenosine was used to immunize mice for production of Adonis, an IgM monoclonal antibody. Adonis bound to the immunogen peptide and the native receptor in ELISA with K(D) values in 6.51-12.35 nM range. It recognized a linear epitope of 7 amino acids (LFEDVVP) at the C-terminal part of the external loop. Adonis revealed a 45-kDa band in lysate of human peripheral blood mononuclear cells in Western blotting in denaturing conditions. This served to monitor the up-regulation of the A(2A)R expression by caffeine. Adonis stimulated the cAMP production and inhibited the cell proliferation of an A(2A)R transfected stable cell line. These results confirm the immunogenicity and the functional relevance of the second extracellular loop of the A(2A)R. They suggest that Adonis may be of clinical use in various pathological situations to measure the regulation of the A(2A)R expression and to act as A(2A)R agonist drug.
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Affiliation(s)
- Youlet By
- Laboratoire de Biochimie Endocrinienne et Métabolique (EA3288), Université de la Méditerranée, Faculté de Médecine Timone, Marseille, France
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Hofbauer KG, Lecourt AC, Peter JC. Antibodies as pharmacologic tools for studies on the regulation of energy balance. Nutrition 2008; 24:791-7. [PMID: 18662861 DOI: 10.1016/j.nut.2008.06.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 06/03/2008] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Active immunization in rats may serve several purposes: the production of a disease-like phenotype, the generation of pharmacologic tools, and the development of clinically useful therapies. We selected the melanocortin-4 receptor (MC4R) as a target because its blockade could provide a treatment for anorexia and cachexia. METHODS We used a sequence of the N-terminal (NT) domain of the MC4R as an antigen. Rats immunized against the NT peptide produced specific MC4R antibodies (Abs) that were purified and characterized in vitro and in vivo. RESULTS The Abs acted as inverse agonists and reduced under basal conditions the production of cyclic adenosine monophosphate in HEK-293 cells expressing the human MC4R. Rats immunized against the NT peptide developed a phenotype consistent with hypothalamic MC4R blockade, i.e., increased food intake and body weight, liver and fat-pad weights, hepatic steatosis, and increased plasma triacylglycerols. With a high-fat diet, plasma insulin levels were significantly increased. In separate experiments an increase in food intake was observed after injection of purified MC4R Abs into the third ventricle. When lipopolysaccharide was administered in NT-immunized rats the reduction of food intake was partly prevented in this model of cytokine-induced anorexia. CONCLUSION Our results show that active immunization of rats against the MC4R resulted in the generation of specific Abs that stimulated food intake by acting as inverse agonists of the hypothalamic MC4R. Pharmacologically active monoclonal MC4R Abs could be the starting point for the development of novel treatments for patients with anorexia or cachexia.
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Affiliation(s)
- Karl G Hofbauer
- Applied Pharmacology, Biozentrum, University of Basel, Basel, Switzerland.
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Balau LS, Vahlberg C, Petoral RM, Uvdal K. Mixed monolayers to promote g-protein adsorption: alpha2A-adrenergic receptor-derived peptides coadsorbed with formyl-terminated oligopeptides. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:8474-9. [PMID: 17622157 DOI: 10.1021/la063447f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Pure and mixed monolayers of a synthetic peptide, GPR-i3n, derived from the third intracellular loop of the alpha2 adrenergic receptor and a shorter inactive oligopeptide, N-formyl-(Gly)3-(Cys) (called 3GC), were prepared on gold surfaces. The mixing ratio of the GPR-i3n and 3GC was used to control G-protein binding capability. The GPR-i3n peptide is specially designed for bovine G-protein selectivity and has been proven to have high affinity to G-proteins [Vahlberg, C.; Petoral, R. M., Jr.; Lindell, C.; Broo, K.; Uvdal, K. Langmuir 2006, 22 (17), 7260-7264]. Pure 3GC monolayers show very low protein adsorption capability. In this study, 3GC is chosen as a coadsorbent, with the aim to induce molecular conformational changes during monolayer formation to enhance G-protein adsorption. A full characterization of the mixed monolayers was done. The monolayer thickness and the mass-related surface coverage for both GPR-i3n and 3GC were investigated using radio labeling. The GPR-i3n was labeled by 125I-targeting tyrosine, and the activity was measured by using radioimmunoassay (RIA). The formation and chemical composition of GPR-i3n and 3GC monolayers were investigated using X-ray photoelectron spectroscopy, and it is shown that both GPR-i3n and 3GC bind chemically to the gold surface. The interaction between the mixed monolayers and G-proteins was investigated by means of real-time surface plasmon resonance. There is a higher protein binding capacity to the monolayer when the GPR-i3n peptide is intermixed with the 3GC coadsorbent, despite the fact that the 3GC itself has a very low G-protein binding capability. This supports a molecular reorientation at the surface, while 3GC is intermixed with GPR-i3n.
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Affiliation(s)
- Luminita Savitchi Balau
- Division of Sensor Science and Molecular Physics, Department of Physics, Chemistry and Biology, IFM, Linköping University, SE-581 83 Linköping, Sweden
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Peter JC, Nicholson JR, Heydet D, Lecourt AC, Hoebeke J, Hofbauer KG. Antibodies against the melanocortin-4 receptor act as inverse agonists in vitro and in vivo. Am J Physiol Regul Integr Comp Physiol 2007; 292:R2151-8. [PMID: 17322114 DOI: 10.1152/ajpregu.00878.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functionally active antibodies (Abs) against central G-protein-coupled receptors have not yet been reported. We selected the hypothalamic melanocortin-4 receptor (MC4-R) as a target because of its crucial role in the regulation of energy homeostasis. A 15 amino acid sequence of the N-terminal (NT) domain was used as an antigen. This peptide showed functional activity in surface plasmon resonance experiments and in studies on HEK-293 cells overexpressing the human MC4-R (hMC4-R). Rats immunized against the NT peptide produced specific antibodies, which were purified and characterized in vitro. In HEK-293 cells, rat anti-NT Abs showed specific immunofluorescence labeling of hMC4-R. They reduced the production of cAMP under basal conditions and after stimulation with a synthetic MC4-R agonist. Rats immunized against the NT peptide developed a phenotype consistent with MC4-R blockade, that is, increased food intake and body weight, increased liver and fat pad weight, and elevated plasma triglycerides. In a separate experiment in rats, an increase in food intake could be produced after injection of purified Abs into the third ventricle. Similar results were obtained in rats injected with anti-NT Abs raised in rabbits. Our data show for the first time that active immunization of rats against the NT sequence of the MC4-R results in specific Abs, which appear to stimulate food intake by acting as inverse agonists in the hypothalamus.
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12
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Vahlberg C, Petoral RM, Lindell C, Broo K, Uvdal K. alpha(2A)-adrenergic receptor derived peptide adsorbates: a G-protein interaction study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:7260-4. [PMID: 16893224 DOI: 10.1021/la052801r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The affinity of alpha(2A)-adrenergic receptor (alpha(2A)-AR) derived peptide adsorbates for the functional bovine brain G-protein is studied in the search for the minimum sequence recognition. Three short peptides (GPR-i2c, GPR-i3n, and GPR-i3c) are designed to mimic the second and third intracellular loops of the receptor. X-ray photoelectron spectroscopy is used to study the chemical composition of the peptides and the binding strength to the surfaces. Chemisorption of the peptides to the gold substrates is observed. Infrared spectroscopy is used to study the characteristic absorption bands of the peptides. The presence of peptides on the surfaces is verified by prominent amide I and amide II bands. The interaction between the peptides and the G-protein is studied with surface plasmon resonance. It is shown that GPR-i3n has the highest affinity for the G-protein. Equilibrium analysis of the binding shows that the G-protein keeps its native conformation when interacting with GPR-i3c, but during the interaction with GPR-i2c and GPR-i3n the conformation of G-protein is changed, leading to the formation of aggregates and/or multilayers.
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Affiliation(s)
- Cecilia Vahlberg
- Division of Molecular Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
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13
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Abstract
We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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