1
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Santos-López J, de la Paz K, Fernández FJ, Vega MC. Structural biology of complement receptors. Front Immunol 2023; 14:1239146. [PMID: 37753090 PMCID: PMC10518620 DOI: 10.3389/fimmu.2023.1239146] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 08/16/2023] [Indexed: 09/28/2023] Open
Abstract
The complement system plays crucial roles in a wide breadth of immune and inflammatory processes and is frequently cited as an etiological or aggravating factor in many human diseases, from asthma to cancer. Complement receptors encompass at least eight proteins from four structural classes, orchestrating complement-mediated humoral and cellular effector responses and coordinating the complex cross-talk between innate and adaptive immunity. The progressive increase in understanding of the structural features of the main complement factors, activated proteolytic fragments, and their assemblies have spurred a renewed interest in deciphering their receptor complexes. In this review, we describe what is currently known about the structural biology of the complement receptors and their complexes with natural agonists and pharmacological antagonists. We highlight the fundamental concepts and the gray areas where issues and problems have been identified, including current research gaps. We seek to offer guidance into the structural biology of the complement system as structural information underlies fundamental and therapeutic research endeavors. Finally, we also indicate what we believe are potential developments in the field.
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Affiliation(s)
- Jorge Santos-López
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Karla de la Paz
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
- Research & Development, Abvance Biotech SL, Madrid, Spain
| | | | - M. Cristina Vega
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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2
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Ulloa-Aguirre A, Zariñán T, Jardón-Valadez E. Misfolded G Protein-Coupled Receptors and Endocrine Disease. Molecular Mechanisms and Therapeutic Prospects. Int J Mol Sci 2021; 22:ijms222212329. [PMID: 34830210 PMCID: PMC8622668 DOI: 10.3390/ijms222212329] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/28/2021] [Accepted: 10/01/2021] [Indexed: 11/30/2022] Open
Abstract
Misfolding of G protein-coupled receptors (GPCRs) caused by mutations frequently leads to disease due to intracellular trapping of the conformationally abnormal receptor. Several endocrine diseases due to inactivating mutations in GPCRs have been described, including X-linked nephrogenic diabetes insipidus, thyroid disorders, familial hypocalciuric hypercalcemia, obesity, familial glucocorticoid deficiency [melanocortin-2 receptor, MC2R (also known as adrenocorticotropin receptor, ACTHR), and reproductive disorders. In these mutant receptors, misfolding leads to endoplasmic reticulum retention, increased intracellular degradation, and deficient trafficking of the abnormal receptor to the cell surface plasma membrane, causing inability of the receptor to interact with agonists and trigger intracellular signaling. In this review, we discuss the mechanisms whereby mutations in GPCRs involved in endocrine function in humans lead to misfolding, decreased plasma membrane expression of the receptor protein, and loss-of-function diseases, and also describe several experimental approaches employed to rescue trafficking and function of the misfolded receptors. Special attention is given to misfolded GPCRs that regulate reproductive function, given the key role played by these particular membrane receptors in sexual development and fertility, and recent reports on promising therapeutic interventions targeting trafficking of these defective proteins to rescue completely or partially their normal function.
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Affiliation(s)
- Alfredo Ulloa-Aguirre
- Red de Apoyo a la Investigación, Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición SZ, Mexico City 14080, Mexico;
- Correspondence:
| | - Teresa Zariñán
- Red de Apoyo a la Investigación, Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición SZ, Mexico City 14080, Mexico;
| | - Eduardo Jardón-Valadez
- Departamento de Recursos de la Tierra, Universidad Autónoma Metropolitana-Lerma, Lerma de Villada 52005, Estado de México, Mexico;
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3
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Das A, Behera LM, Rana S. Interaction of Human C5a with the Major Peptide Fragments of C5aR1: Direct Evidence in Support of "Two-Site" Binding Paradigm. ACS OMEGA 2021; 6:22876-22887. [PMID: 34514259 PMCID: PMC8427777 DOI: 10.1021/acsomega.1c03400] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/18/2021] [Indexed: 05/26/2023]
Abstract
The C5a receptor's (C5aR1) physiological function in various tissues depends on its high-affinity binding to the cationic proinflammatory glycoprotein C5a, produced during the activation of the complement system. However, an overstimulated complement can quickly alter the C5a-C5aR1 function from physiological to pathological, as has been noted in the case of several chronic inflammation-induced diseases like asthma, lung injury, multiorgan failure, sepsis, and now COVID-19. In the absence of the structural data, the current study provides the confirmatory biophysical validation of the hypothesized "two-site" binding interactions of C5a, involving (i) the N-terminus (NT) peptide ("Site1") and (ii) the extracellular loop 2 (ECL2) peptide of the extracellular surface (ECS) of the C5aR1 ("Site2"), as illustrated earlier in the reported model structural complex of C5a-C5aR1. The biophysical and computational data elaborated in the study provides an improved understanding of the C5a-C5aR1 interaction at an atomistic resolution, highlighting the energetic importance of the aspartic acids on the NT-peptide of C5aR1 toward binding of C5a. The current study can potentially advance the search and optimization of new-generation alternative "antibodies" as well as "neutraligands" targeting the C5a to modulate its interaction with C5aR1.
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4
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Ashokan A, Harisankar HS, Kameswaran M, Aradhyam GK. Critical APJ receptor residues in extracellular domains that influence effector selectivity. FEBS J 2021; 288:6543-6562. [PMID: 34076959 DOI: 10.1111/febs.16048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/14/2021] [Accepted: 05/01/2021] [Indexed: 11/29/2022]
Abstract
Human APJ receptor/apelin receptor (APJR), activated by apelin peptide isoforms, regulates a wide range of physiological processes. The role of extracellular loop (ECL) domain residues of APJR in ligand binding and receptor activation has not been established yet. Based on multiple sequence alignment of APJ receptor from various organisms, we identified conserved residues in the extracellular domains. Alanine substitutions of specific residues were characterized to evaluate their ligand binding efficiency and Gq -, Gi -, and β-arrestin-mediated signaling. Mutation-dependent variation in ligand binding and signaling was observed. W197 A in ECL2 and L276 L277 W279 -AAA in ECL3 were deficient in Gi and β-arrestin signaling pathways with relatively preserved Gq -mediated signaling. T169 T170 -AA, Y182 A, and T190 A mutants in ECL2 showed impaired β-arrestin-dependent cell signaling while maintaining G protein- mediated signaling. Structural comparison with angiotensin II type I receptor revealed the importance of ECL2 and ECL3 residues in APJR ligand binding and signaling. Our results unequivocally confirm the specific role of these ECL residues in ligand binding and in orchestrating receptor conformations that are involved in preferential/biased signaling functions.
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Affiliation(s)
- Anisha Ashokan
- Signal Transduction Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Harikumar Sheela Harisankar
- Signal Transduction Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Mythili Kameswaran
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Gopala Krishna Aradhyam
- Signal Transduction Laboratory, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
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5
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Wang X, van Westen GJP, Heitman LH, IJzerman AP. G protein-coupled receptors expressed and studied in yeast. The adenosine receptor as a prime example. Biochem Pharmacol 2020; 187:114370. [PMID: 33338473 DOI: 10.1016/j.bcp.2020.114370] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 12/11/2020] [Accepted: 12/11/2020] [Indexed: 11/25/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest class of membrane proteins with around 800 members in the human genome/proteome. Extracellular signals such as hormones and neurotransmitters regulate various biological processes via GPCRs, with GPCRs being the bodily target of 30-40% of current drugs on the market. Complete identification and understanding of GPCR functionality will provide opportunities for novel drug discovery. Yeast expresses three different endogenous GPCRs regulating pheromone and sugar sensing, with the pheromone pathway offering perspectives for the characterization of heterologous GPCR signaling. Moreover, yeast offers a ''null" background for studies on mammalian GPCRs, including GPCR activation and signaling, ligand identification, and characterization of disease-related mutations. This review focuses on modifications of the yeast pheromone signaling pathway for functional GPCR studies, and on opportunities and usage of the yeast system as a platform for human GPCR studies. Finally, this review discusses in some further detail studies of adenosine receptors heterologously expressed in yeast, and what Geoff Burnstock thought of this approach.
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Affiliation(s)
- Xuesong Wang
- Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Gerard J P van Westen
- Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Laura H Heitman
- Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands; Oncode Institute, Leiden, The Netherlands
| | - Adriaan P IJzerman
- Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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6
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Nakamura Y, Asama R, Tabata T, Morita K, Maruyama T, Kondo A, Ishii J. Comparative analyses of site-directed mutagenesis of human melatonin MTNR1A and MTNR1B receptors using a yeast fluorescent biosensor. Biotechnol Bioeng 2020; 118:863-876. [PMID: 33095446 DOI: 10.1002/bit.27609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/22/2020] [Accepted: 10/22/2020] [Indexed: 11/08/2022]
Abstract
Melatonin is an indoleamine neurohormone made by the pineal gland. Its receptors, MTNR1A and MTNR1B, are members of the G-protein-coupled receptor (GPCR) family and are involved in sleep, circadian rhythm, and mood disorders, and in the inhibition of cancer growth. These receptors, therefore, represent significant molecular targets for insomnia, circadian sleep disorders, and cancer. The yeast Saccharomyces cerevisiae is an attractive host for assaying agonistic activity for human GPCR. We previously constructed a GPCR-based biosensor employing a high-sensitivity yeast strain that incorporated both a chimeric yeast-human Gα protein and a bright fluorescent reporter gene (ZsGreen). Similar approaches have been used for simple and convenient measurements of various GPCR activities. In the current study, we constructed a fluorescence-based yeast biosensor for monitoring the signaling activation of human melatonin receptors. We used this system to analyze point mutations, including previously unreported mutations of the consensus sequences of MTNR1A and MTNR1B melatonin receptors and compared their effects. Most mutations in the consensus sequences significantly affected the signaling capacities of both receptors, but several mutations showed differences between these subtype receptors. Thus, this yeast biosensor holds promise for revealing the functions of melatonin receptors.
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Affiliation(s)
- Yasuyuki Nakamura
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Ririka Asama
- Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Takuya Tabata
- Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
| | - Kenta Morita
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Tatsuo Maruyama
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan
| | - Akihiko Kondo
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan.,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Kobe, Japan.,Center for Sustainable Resource Science, RIKEN, Yokohama, Japan
| | - Jun Ishii
- Engineering Biology Research Center, Kobe University, Kobe, Japan.,Graduate School of Science, Technology and Innovation, Kobe University, Kobe, Japan
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7
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Stauch B, Johansson LC, McCorvy JD, Patel N, Han GW, Huang XP, Gati C, Batyuk A, Slocum ST, Ishchenko A, Brehm W, White TA, Michaelian N, Madsen C, Zhu L, Grant TD, Grandner JM, Shiriaeva A, Olsen RHJ, Tribo AR, Yous S, Stevens RC, Weierstall U, Katritch V, Roth BL, Liu W, Cherezov V. Structural basis of ligand recognition at the human MT 1 melatonin receptor. Nature 2019; 569:284-288. [PMID: 31019306 PMCID: PMC6696938 DOI: 10.1038/s41586-019-1141-3] [Citation(s) in RCA: 136] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 03/25/2019] [Indexed: 11/08/2022]
Abstract
Melatonin (N-acetyl-5-methoxytryptamine) is a neurohormone that maintains circadian rhythms1 by synchronization to environmental cues and is involved in diverse physiological processes2 such as the regulation of blood pressure and core body temperature, oncogenesis, and immune function3. Melatonin is formed in the pineal gland in a light-regulated manner4 by enzymatic conversion from 5-hydroxytryptamine (5-HT or serotonin), and modulates sleep and wakefulness5 by activating two high-affinity G-protein-coupled receptors, type 1A (MT1) and type 1B (MT2)3,6. Shift work, travel, and ubiquitous artificial lighting can disrupt natural circadian rhythms; as a result, sleep disorders affect a substantial population in modern society and pose a considerable economic burden7. Over-the-counter melatonin is widely used to alleviate jet lag and as a safer alternative to benzodiazepines and other sleeping aids8,9, and is one of the most popular supplements in the United States10. Here, we present high-resolution room-temperature X-ray free electron laser (XFEL) structures of MT1 in complex with four agonists: the insomnia drug ramelteon11, two melatonin analogues, and the mixed melatonin-serotonin antidepressant agomelatine12,13. The structure of MT2 is described in an accompanying paper14. Although the MT1 and 5-HT receptors have similar endogenous ligands, and agomelatine acts on both receptors, the receptors differ markedly in the structure and composition of their ligand pockets; in MT1, access to the ligand pocket is tightly sealed from solvent by extracellular loop 2, leaving only a narrow channel between transmembrane helices IV and V that connects it to the lipid bilayer. The binding site is extremely compact, and ligands interact with MT1 mainly by strong aromatic stacking with Phe179 and auxiliary hydrogen bonds with Asn162 and Gln181. Our structures provide an unexpected example of atypical ligand entry for a non-lipid receptor, lay the molecular foundation of ligand recognition by melatonin receptors, and will facilitate the design of future tool compounds and therapeutic agents, while their comparison to 5-HT receptors yields insights into the evolution and polypharmacology of G-protein-coupled receptors.
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MESH Headings
- Acetamides/chemistry
- Acetamides/metabolism
- Amino Acid Sequence
- Antidepressive Agents/chemistry
- Antidepressive Agents/metabolism
- Crystallization
- Electrons
- Humans
- Indenes/chemistry
- Indenes/metabolism
- Lasers
- Ligands
- Melatonin/analogs & derivatives
- Melatonin/chemistry
- Models, Molecular
- Molecular Docking Simulation
- Mutation
- Receptor, Melatonin, MT1/agonists
- Receptor, Melatonin, MT1/chemistry
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Serotonin, 5-HT2C/chemistry
- Structure-Activity Relationship
- Substrate Specificity
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Affiliation(s)
- Benjamin Stauch
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Linda C Johansson
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - John D McCorvy
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Nilkanth Patel
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Gye Won Han
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Xi-Ping Huang
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Cornelius Gati
- SLAC National Accelerator Laboratory, Bioscience Division, Menlo Park, CA, USA
- Stanford University, Department of Structural Biology, Stanford, CA, USA
| | - Alexander Batyuk
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Samuel T Slocum
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Andrii Ishchenko
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Wolfgang Brehm
- Center for Free-Electron Laser Science, DESY, Hamburg, Germany
| | - Thomas A White
- Center for Free-Electron Laser Science, DESY, Hamburg, Germany
| | - Nairie Michaelian
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Caleb Madsen
- Department of Physics, Arizona State University, Tempe, AZ, USA
| | - Lan Zhu
- School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - Thomas D Grant
- Hauptman-Woodward Institute, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Jessica M Grandner
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Anna Shiriaeva
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Reid H J Olsen
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Alexandra R Tribo
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Saïd Yous
- Univ Lille, Inserm, CHU Lille, UMR-S 1172 - JPArc - Centre de Recherche Jean-Pierre AUBERT Neurosciences et Cancer, Lille, France
| | - Raymond C Stevens
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Uwe Weierstall
- Department of Physics, Arizona State University, Tempe, AZ, USA
- School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - Vsevolod Katritch
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Bryan L Roth
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Wei Liu
- School of Molecular Sciences and Biodesign Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, USA.
| | - Vadim Cherezov
- Bridge Institute,USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA.
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
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8
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Banerjee AA, Mahale SD. Extracellular loop 3 substitutions K589N and A590S in FSH receptor increase FSH-induced receptor internalization and along with S588T substitution exhibit impaired ERK1/2 phosphorylation. Arch Biochem Biophys 2018; 659:57-65. [DOI: 10.1016/j.abb.2018.09.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 09/11/2018] [Accepted: 09/14/2018] [Indexed: 12/30/2022]
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9
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Rizzo MJ, Evans JP, Burt M, Saunders CJ, Johnson EC. Unexpected role of a conserved domain in the first extracellular loop in G protein-coupled receptor trafficking. Biochem Biophys Res Commun 2018; 503:1919-1926. [PMID: 30064912 DOI: 10.1016/j.bbrc.2018.07.136] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 07/25/2018] [Indexed: 12/18/2022]
Abstract
G protein-coupled receptors are the largest superfamily of cell surface receptors in the Metazoa and play critical roles in transducing extracellular signals into intracellular responses. This action is mediated through conformational changes in the receptor following ligand binding. A number of conserved motifs have critical roles in GPCR function, and here we focus on a highly conserved motif (WxFG) in extracellular loop one (EL1). A phylogenetic analysis documents the presence of the WxFG motif in ∼90% of Class A GPCRs and the motif is represented in 17 of the 19 Class A GPCR subfamilies. Using site-directed mutagenesis, we mutagenized the conserved tryptophan residue in eight receptors which are members of disparate class A GPCR subfamilies from different taxa. The modification of the Drosophila leucokinin receptor shows that substitution of any non-aromatic amino acid for the tryptophan leads to a loss of receptor function. Additionally, leucine substitutions at this position caused similar signaling defects in the follicle-stimulating hormone receptor (FSHR), Galanin receptor (GALR1), AKH receptor (AKHR), corazonin receptor (CRZR), and muscarinic acetylcholine receptor (mACHR1). Visualization of modified receptors through the incorporation of a fluorescent tag revealed a severe reduction in plasma membrane expression, indicating aberrant trafficking of these modified receptors. Taken together, these results suggest a novel role for the WxFG motif in GPCR trafficking and receptor function.
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Affiliation(s)
- Michael J Rizzo
- Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - John P Evans
- Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Morgan Burt
- Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Cecil J Saunders
- Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Erik C Johnson
- Department of Biology, Wake Forest University, Winston-Salem, NC, 27109, USA; Center for Molecular Signaling, Wake Forest University, Winston-Salem, NC, 27109, USA.
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10
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Sahoo AR, Mishra R, Rana S. The Model Structures of the Complement Component 5a Receptor (C5aR) Bound to the Native and Engineered hC5a. Sci Rep 2018; 8:2955. [PMID: 29440703 PMCID: PMC5811428 DOI: 10.1038/s41598-018-21290-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/31/2018] [Indexed: 12/13/2022] Open
Abstract
The interaction of hC5a with C5aR, previously hypothesized to involve a “two-site” binding, (i) recognition of the bulk of hC5a by the N-terminus (NT) of C5aR (“site1”), and (ii) recognition of C-terminus (CT) of hC5a by the extra cellular surface (ECS) of the C5aR (“site2”). However, the pharmacological landscapes of such recognition sites are yet to be illuminated at atomistic resolution. In the context, unique model complexes of C5aR, harboring pharmacophores of diverse functionality at the “site2” has recently been described. The current study provides a rational illustration of the “two-site” binding paradigm in C5aR, by recruiting the native agonist hC5a and engineered antagonist hC5a(A8). The hC5a-C5aR and hC5a(A8)-C5aR complexes studied over 250 ns of molecular dynamics (MD) each in POPC bilayer illuminate the hallmark of activation mechanism in C5aR. The intermolecular interactions in the model complexes are well supported by the molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) based binding free energy calculation, strongly correlating with the reported mutational studies. Exemplified in two unique and contrasting molecular complexes, the study provides an exceptional understanding of the pharmacological divergence observed in C5aR, which will certainly be useful for search and optimization of new generation “neutraligands” targeting the hC5a-C5aR interaction.
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Affiliation(s)
- Amita Rani Sahoo
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, 752050, India
| | - Richa Mishra
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, 752050, India
| | - Soumendra Rana
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, 752050, India.
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11
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Rana S, Sahoo AR, Majhi BK. Structural complexes of the agonist, inverse agonist and antagonist bound C5a receptor: insights into pharmacology and signaling. MOLECULAR BIOSYSTEMS 2017; 12:1586-99. [PMID: 26978009 DOI: 10.1039/c6mb00031b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The C5a receptor (C5aR) is a pharmacologically important G-protein coupled receptor (GPCR) that interacts with (h)C5a, by recruiting both the "orthosteric" sites (site1 at the N-terminus and site2 at the ECS, extra cellular surface) on C5aR in a two site-binding model. However, the complex pharmacological landscape and the distinguishing chemistry operating either at the "orthosteric" site1 or at the functionally important "orthosteric" site2 of C5aR are still not clear, which greatly limits the understanding of C5aR pharmacology. One of the major bottlenecks is the lack of an experimental structure or a refined model structure of C5aR with appropriately defined active sites. The study attempts to understand the pharmacology at the "orthosteric" site2 of C5aR rationally by generating a highly refined full-blown model structure of C5aR through advanced molecular modeling techniques, and further subjecting it to automated docking and molecular dynamics (MD) studies in the POPC bilayer. The first series of structural complexes of C5aR respectively bound to a linear native peptide agonist ((h)C5a-CT), a small molecule inverse agonist (NDT) and a cyclic peptide antagonist (PMX53) are reported, apparently establishing the unique pharmacological landscape of the "orthosteric" site2, which also illustrates an energetically distinct but coherent competitive chemistry ("cation-π" vs. "π-π" interactions) involved in distinguishing the established ligands known for targeting the "orthosteric" site2 of C5aR. Over a total of 1 μs molecular dynamics (MD) simulation in the POPC bilayer, it is evidenced that while the agonist prefers a "cation-π" interaction, the inverse agonist prefers a "cogwheel/L-shaped" interaction in contrast to the "edge-to-face/T-shaped" type π-π interactions demonstrated by the antagonist by engaging the F275(7.28) of the C5aR. In the absence of a NMR or crystallographically guided model structure of C5aR, the computational model complexes not only provide valuable insights for understanding the C5aR pharmacology, but also emerge as a promising platform for the design and discovery of future potential drug candidates targeting the (h)C5a-C5aR signaling axes.
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Affiliation(s)
- Soumendra Rana
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology, Bhubaneswar, Odisha 751007, India.
| | - Amita Rani Sahoo
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology, Bhubaneswar, Odisha 751007, India.
| | - Bharat Kumar Majhi
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology, Bhubaneswar, Odisha 751007, India.
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Liu R, Wong W, IJzerman AP. Human G protein-coupled receptor studies in Saccharomyces cerevisiae. Biochem Pharmacol 2016; 114:103-15. [DOI: 10.1016/j.bcp.2016.02.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 02/12/2016] [Indexed: 12/22/2022]
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13
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Schaarschmidt J, Nagel MBM, Huth S, Jaeschke H, Moretti R, Hintze V, von Bergen M, Kalkhof S, Meiler J, Paschke R. Rearrangement of the Extracellular Domain/Extracellular Loop 1 Interface Is Critical for Thyrotropin Receptor Activation. J Biol Chem 2016; 291:14095-14108. [PMID: 27129207 DOI: 10.1074/jbc.m115.709659] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Indexed: 11/06/2022] Open
Abstract
The thyroid stimulating hormone receptor (TSHR) is a G protein-coupled receptor (GPCR) with a characteristic large extracellular domain (ECD). TSHR activation is initiated by binding of the hormone ligand TSH to the ECD. How the extracellular binding event triggers the conformational changes in the transmembrane domain (TMD) necessary for intracellular G protein activation is poorly understood. To gain insight in this process, the knowledge on the relative positioning of ECD and TMD and the conformation of the linker region at the interface of ECD and TMD are of particular importance. To generate a structural model for the TSHR we applied an integrated structural biology approach combining computational techniques with experimental data. Chemical cross-linking followed by mass spectrometry yielded 17 unique distance restraints within the ECD of the TSHR, its ligand TSH, and the hormone-receptor complex. These structural restraints generally confirm the expected binding mode of TSH to the ECD as well as the general fold of the domains and were used to guide homology modeling of the ECD. Functional characterization of TSHR mutants confirms the previously suggested close proximity of Ser-281 and Ile-486 within the TSHR. Rigidifying this contact permanently with a disulfide bridge disrupts ligand-induced receptor activation and indicates that rearrangement of the ECD/extracellular loop 1 (ECL1) interface is a critical step in receptor activation. The experimentally verified contact of Ser-281 (ECD) and Ile-486 (TMD) was subsequently utilized in docking homology models of the ECD and the TMD to create a full-length model of a glycoprotein hormone receptor.
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Affiliation(s)
- Joerg Schaarschmidt
- Department of Internal Medicine, University of Leipzig, 04103 Leipzig, Germany
| | - Marcus B M Nagel
- Department of Internal Medicine, University of Leipzig, 04103 Leipzig, Germany,; Department of Proteomics, Helmholtz-Centre for Environmental Research, 04318 Leipzig, Germany
| | - Sandra Huth
- Department of Internal Medicine, University of Leipzig, 04103 Leipzig, Germany
| | - Holger Jaeschke
- Department of Internal Medicine, University of Leipzig, 04103 Leipzig, Germany
| | - Rocco Moretti
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Vera Hintze
- Institute of Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, 01069 Dresden, Germany
| | - Martin von Bergen
- Department of Proteomics, Helmholtz-Centre for Environmental Research, 04318 Leipzig, Germany,; Faculty of Biosciences, Pharmacy and Psychology, Institute of Biochemistry, University of Leipzig, 04103 Leipzig, Germany,; Aalborg University, Department of Chemistry and Bioscience, Fredrik Bajers Vej 7, 9220 Aalborg, Denmark
| | - Stefan Kalkhof
- Department of Proteomics, Helmholtz-Centre for Environmental Research, 04318 Leipzig, Germany,; Department of Bioanalytics, University of Applied Sciences and Arts of Coburg, 96450 Coburg, Germany
| | - Jens Meiler
- Department of Chemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235
| | - Ralf Paschke
- Division of Endocrinology and Metabolism and Arnie Charbonneau Cancer Institute University of Calgary, Calgary, Alberta T2N 1N4, Canada.
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Deluca SH, Rathmann D, Beck-Sickinger AG, Meiler J. The activity of prolactin releasing peptide correlates with its helicity. Biopolymers 2016; 99:314-25. [PMID: 23426574 DOI: 10.1002/bip.22162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 08/30/2012] [Accepted: 09/15/2012] [Indexed: 11/09/2022]
Abstract
The prolactin releasing peptide (PrRP) is involved in regulating food intake and body weight homeostasis, but molecular details on the activation of the PrRP receptor remain unclear. C-terminal segments of PrRP with 20 (PrRP20) and 13 (PrRP8-20) amino acids, respectively, have been suggested to be fully active. The data presented herein indicate this is true for the wildtype receptor only; a 5-10-fold loss of activity was found for PrRP8-20 compared to PrRP20 at two extracellular loop mutants of the receptor. To gain insight into the secondary structure of PrRP, we used CD spectroscopy performed in TFE and SDS. Additionally, previously reported NMR data, combined with ROSETTANMR, were employed to determine the structure of amidated PrRP20. The structural ensemble agrees with the spectroscopic data for the full-length peptide, which exists in an equilibrium between α- and 3(10)-helix. We demonstrate that PrRP8-20's reduced propensity to form an α-helix correlates with its reduced biological activity on mutant receptors. Further, distinct amino acid replacements in PrRP significantly decrease affinity and activity but have no influence on the secondary structure of the peptide. We conclude that formation of a primarily α-helical C-terminal region of PrRP is critical for receptor activation.
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Affiliation(s)
- Stephanie H Deluca
- Vanderbilt University Center for Structural Biology, 5144B Biosci/MRBIII, 465 21st Avenue South, Nashville, TN 37232-8725
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15
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Abrogation of immune complex glomerulonephritis by native carboxypeptidase and pharmacological antagonism of the C5a receptor. Cell Mol Immunol 2015; 13:651-7. [PMID: 26166765 PMCID: PMC5037280 DOI: 10.1038/cmi.2015.45] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 04/27/2015] [Accepted: 04/27/2015] [Indexed: 12/11/2022] Open
Abstract
Activation of complement generates C5a which leads to signaling through C5aR1. This is tightly controlled, including by the plasma proteins factor H (FH) and carboxypeptidase N. Here we studied a chronic serum sickness (CSS) model of glomerulonephritis (GN) in which there is an active humoral immune response, formation of glomerular immune complexes (ICs), and resulting glomerular inflammation. The antibody response, glomerular IC deposition, the degree of GN, and consequent renal functional insufficiency in CSS were all worse in FH−/− mice compared to wild-type FH+/+ animals. This was ameliorated in the former by giving a C5aR1 antagonist for the final 3 weeks of the 5-week protocol. In contrast, blocking CP-mediated inactivation of C5a increased these disease measures. Thus, complement regulation by both plasma FH and CP to limit the quantity of active C5a is important in conditions where the humoral immune response is directed to a continuously present foreign antigen. Signaling through C5aR1 enhances the humoral immune response as well as the inflammatory response to ICs that have formed in glomeruli. Both effects are relevant even after disease has begun. Thus, pharmacological targeting of C5a in IC-mediated GN has potential clinical relevance.
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Nakamura Y, Ishii J, Kondo A. Applications of yeast-based signaling sensor for characterization of antagonist and analysis of site-directed mutants of the human serotonin 1A receptor. Biotechnol Bioeng 2015; 112:1906-15. [DOI: 10.1002/bit.25597] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 02/26/2015] [Accepted: 03/03/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Yasuyuki Nakamura
- Department of Chemical Science and Engineering, Graduate School of Engineering; Kobe University; 1-1 Rokkodai, Nada Kobe 657-8501 Japan
| | - Jun Ishii
- Organization of Advanced Science and Technology; Kobe University; Kobe Japan
| | - Akihiko Kondo
- Department of Chemical Science and Engineering, Graduate School of Engineering; Kobe University; 1-1 Rokkodai, Nada Kobe 657-8501 Japan
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17
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Rana S, Sahoo AR. Model structures of inactive and peptide agonist bound C5aR: Insights into agonist binding, selectivity and activation. Biochem Biophys Rep 2015; 1:85-96. [PMID: 29124137 PMCID: PMC5668562 DOI: 10.1016/j.bbrep.2015.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/10/2015] [Accepted: 03/11/2015] [Indexed: 11/30/2022] Open
Abstract
C5a receptor (C5aR) is one of the major chemoattractant receptors of the druggable proteome that binds C5a, the proinflammatory polypeptide of complement cascade, triggering inflammation and SEPSIS. Here, we report the model structures of C5aR in both inactive and peptide agonist (YSFKPMPLaR; a=D-Ala) bound meta-active state. Assembled in CYANA and evolved over molecular dynamics (MD) in POPC bilayer, the inactive C5aR demonstrates a topologically unique compact heptahelical bundle topology harboring a β-hairpin in extracellular loop 2 (ECL2), derived from the atomistic folding simulations. The peptide agonist bound meta-active C5aR deciphers the “site2” at an atomistic resolution in the extracellular surface (ECS), in contrast to the previously hypothesized inter-helical crevice. With estimated Ki≈2.75 μM, the meta-active C5aR excellently rationalizes the IC50 (0.1–13 μM) and EC50 (0.01–6 μM) values, displayed by the peptide agonist in several signaling studies. Moreover, with Ki≈5.3×105 μM, the “site2” also illustrates selectivity, by discriminating the stereochemical mutant peptide (YSFkPMPLaR; k=D-Lys), known to be inert toward C5aR, up to 1 mM concentration. Topologically juxtaposed between the structures of rhodopsin and CXCR1, the C5aR models also display excellent structural correlations with the other G-protein coupled receptors (GPCRs). The models elaborated in the current study unravel many important structural insights previously not known for regulating the agonist binding and activation mechanism of C5aR. Topologically unique inactive and meta-active atomistic models of C5aR. Model demonstrates excellent structural correlation with the other reported GPCRs. Model deciphers the “site2” in the ECS and also demonstrates agonist selectivity. Agonist binding and activation requires “cation–π” interaction with F275 of C5aR. Inactive to meta-active transition involves TM3–TM6 movements (ΔΘ≈+11.1°) in C5aR.
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Affiliation(s)
- Soumendra Rana
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Odisha 751007, India
| | - Amita Rani Sahoo
- Chemical Biology Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Odisha 751007, India
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Gerbier R, Leroux V, Couvineau P, Alvear-Perez R, Maigret B, Llorens-Cortes C, Iturrioz X. New structural insights into the apelin receptor: identification of key residues for apelin binding. FASEB J 2014; 29:314-22. [PMID: 25359495 DOI: 10.1096/fj.14-256339] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Apelin is the endogenous ligand of the orphan 7-transmembrane domain GPCR APJ, now named the apelin receptor (ApelinR). Apelin plays a prominent role in body fluid and cardiovascular homeostasis. To better understand the structural organization of the ApelinR, we built 3 homology 3-dimensional (3D) models of the human ApelinR using the validated cholecystokinin receptor-1 3D model or the X-ray structures of the β2-adrenergic and CXCR4 receptors as templates. Docking of the pyroglutamyl form of apelin 13 (pE13F) into these models revealed the conservation at the bottom of the binding site of a hydrophobic cavity in which the C-terminal Phe of pE13F was embedded. In contrast, at the top of the binding site, depending on the model, different interactions were visualized between acidic residues of the ApelinR and the basic residues of pE13F. Using site-directed mutagenesis, we showed that Asp 92, Glu 172, and Asp 282 of rat ApelinR are key residues in apelin binding by interacting with Lys 8, Arg 2, and Arg 4 of pE13F, respectively. These residues are only seen in the CXCR4-based ApelinR 3D model, further validating this model. These findings bring new insights into the structural organization of the ApelinR and the mode of apelin binding.
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Affiliation(s)
- Romain Gerbier
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Vincent Leroux
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Pierre Couvineau
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Rodrigo Alvear-Perez
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Bernard Maigret
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Catherine Llorens-Cortes
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
| | - Xavier Iturrioz
- College de France, Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology (CIRB), Paris, France; CNRS, UMR 7241, Paris, France; and INSERM, U1050, Paris, France
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Ragnarsson L, Andersson Å, Thomas WG, Lewis RJ. Extracellular Surface Residues of the α1B-Adrenoceptor Critical for G Protein–Coupled Receptor Function. Mol Pharmacol 2014; 87:121-9. [DOI: 10.1124/mol.114.094557] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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20
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Balakumar P, Jagadeesh G. Structural determinants for binding, activation, and functional selectivity of the angiotensin AT1 receptor. J Mol Endocrinol 2014; 53:R71-92. [PMID: 25013233 DOI: 10.1530/jme-14-0125] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The renin-angiotensin system (RAS) plays an important role in the pathophysiology of cardiovascular disorders. Pharmacologic interventions targeting the RAS cascade have led to the discovery of renin inhibitors, angiotensin-converting enzyme inhibitors, and AT(1) receptor blockers (ARBs) to treat hypertension and some cardiovascular and renal disorders. Mutagenesis and modeling studies have revealed that differential functional outcomes are the results of multiple active states conformed by the AT(1) receptor upon interaction with angiotensin II (Ang II). The binding of agonist is dependent on both extracellular and intramembrane regions of the receptor molecule, and as a consequence occupies more extensive area of the receptor than a non-peptide antagonist. Both agonist and antagonist bind to the same intramembrane regions to interfere with each other's binding to exhibit competitive, surmountable interaction. The nature of interactions with the amino acids in the receptor is different for each of the ARBs given the small differences in the molecular structure between drugs. AT(1) receptors attain different conformation states after binding various Ang II analogues, resulting in variable responses through activation of multiple signaling pathways. These include both classical and non-classical pathways mediated through growth factor receptor transactivations, and provide cross-communication between downstream signaling molecules. The structural requirements for AT(1) receptors to activate extracellular signal-regulated kinases 1 and 2 through G proteins, or G protein-independently through β-arrestin, are different. We review the structural and functional characteristics of Ang II and its analogs and antagonists, and their interaction with amino acid residues in the AT(1) receptor.
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Affiliation(s)
- Pitchai Balakumar
- Pharmacology UnitFaculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Kedah Darul Aman, MalaysiaDivision of Cardiovascular and Renal ProductsCenter for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland 20993, USA
| | - Gowraganahalli Jagadeesh
- Pharmacology UnitFaculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Kedah Darul Aman, MalaysiaDivision of Cardiovascular and Renal ProductsCenter for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland 20993, USA
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21
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Pedragosa-Badia X, Sliwoski GR, Dong Nguyen E, Lindner D, Stichel J, Kaufmann KW, Meiler J, Beck-Sickinger AG. Pancreatic polypeptide is recognized by two hydrophobic domains of the human Y4 receptor binding pocket. J Biol Chem 2014; 289:5846-59. [PMID: 24375409 PMCID: PMC3937655 DOI: 10.1074/jbc.m113.502021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 12/21/2013] [Indexed: 12/12/2022] Open
Abstract
Structural characterization of the human Y4 receptor (hY4R) interaction with human pancreatic polypeptide (hPP) is crucial, not only for understanding its biological function but also for testing treatment strategies for obesity that target this interaction. Here, the interaction of receptor mutants with pancreatic polypeptide analogs was studied through double-cycle mutagenesis. To guide mutagenesis and interpret results, a three-dimensional comparative model of the hY4R-hPP complex was constructed based on all available class A G protein-coupled receptor crystal structures and refined using experimental data. Our study reveals that residues of the hPP and the hY4R form a complex network consisting of ionic interactions, hydrophobic interactions, and hydrogen binding. Residues Tyr(2.64), Asp(2.68), Asn(6.55), Asn(7.32), and Phe(7.35) of Y4R are found to be important in receptor activation by hPP. Specifically, Tyr(2.64) interacts with Tyr(27) of hPP through hydrophobic contacts. Asn(7.32) is affected by modifications on position Arg(33) of hPP, suggesting a hydrogen bond between these two residues. Likewise, we find that Phe(7.35) is affected by modifications of hPP at positions 33 and 36, indicating interactions between these three amino acids. Taken together, we demonstrate that the top of transmembrane helix 2 (TM2) and the top of transmembrane helices 6 and 7 (TM6-TM7) form the core of the peptide binding pocket. These findings will contribute to the rational design of ligands that bind the receptor more effectively to produce an enhanced agonistic or antagonistic effect.
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Affiliation(s)
- Xavier Pedragosa-Badia
- From the Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Universität Leipzig, 04103 Leipzig, Germany and
| | - Gregory R. Sliwoski
- the Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-8725
| | - Elizabeth Dong Nguyen
- the Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-8725
| | - Diana Lindner
- From the Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Universität Leipzig, 04103 Leipzig, Germany and
| | - Jan Stichel
- From the Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Universität Leipzig, 04103 Leipzig, Germany and
| | - Kristian W. Kaufmann
- the Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-8725
| | - Jens Meiler
- the Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-8725
| | - Annette G. Beck-Sickinger
- From the Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Universität Leipzig, 04103 Leipzig, Germany and
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Gonzalez A, Cordomí A, Matsoukas M, Zachmann J, Pardo L. Modeling of G Protein-Coupled Receptors Using Crystal Structures: From Monomers to Signaling Complexes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 796:15-33. [DOI: 10.1007/978-94-007-7423-0_2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Soriano-Ursúa MA, Trujillo-Ferrara JG, Correa-Basurto J, Vilar S. Recent structural advances of β1 and β2 adrenoceptors yield keys for ligand recognition and drug design. J Med Chem 2013; 56:8207-23. [PMID: 23862978 DOI: 10.1021/jm400471z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Because they represent attractive drug targets, adrenoceptors have been widely studied. Recent progress in structural data of β-adrenoceptors allows us to understand and predict key interactions in ligand recognition and receptor activation. Nevertheless, an important aspect of this process has only begun to be explored: the stabilization of a conformational state of these receptors upon contact with a ligand and the capacity of a ligand to influence receptor conformation through allosteric modulation, biased signaling, and selectivity. The aim of the present Perspective is to identify the well-defined orthosteric binding site and possible allosteric sites and to analyze the importance of the ligand-receptor interaction in the stabilization of certain receptor conformations. For this purpose, we have reviewed recent advances made through the use of X-ray data from ligand-β-adrenoceptor (including ADRB1 and ADRB2) crystal structures. Most importantly, implications in the medicinal chemistry field are explored in relation to drug design.
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Affiliation(s)
- Marvin A Soriano-Ursúa
- Departments of Biochemistry and Physiology, Laboratory of Molecular Modeling and Bioinformatics, Postgraduate Research Section, Escuela Superior de Medicina, Instituto Politécnico Nacional , Plan de San Luis y Dı́az Mirón s/n, Mexico City, 11340, Mexico
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Klos A, Wende E, Wareham KJ, Monk PN. International Union of Basic and Clinical Pharmacology. [corrected]. LXXXVII. Complement peptide C5a, C4a, and C3a receptors. Pharmacol Rev 2013; 65:500-43. [PMID: 23383423 DOI: 10.1124/pr.111.005223] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, originally termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, C5a, C4a, and C3a, participate at all levels of the immune response and are also involved in other processes such as neural development and organ regeneration. Their primary function, however, is in inflammation, so they are important targets for the development of antiinflammatory therapies. Only three receptors for complement peptides have been found, but there are no satisfactory antagonists as yet, despite intensive investigation. In humans, there is a single receptor for C3a (C3a receptor), no known receptor for C4a, and two receptors for C5a (C5a₁ receptor and C5a₂ receptor). The most recently characterized receptor, the C5a₂ receptor (previously known as C5L2 or GPR77), has been regarded as a passive binding protein, but signaling activities are now ascribed to it, so we propose that it be formally identified as a receptor and be given a name to reflect this. Here, we describe the complex biology of the complement peptides, introduce a new suggested nomenclature, and review our current knowledge of receptor pharmacology.
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Affiliation(s)
- Andreas Klos
- Department for Medical Microbiology, Medical School Hannover, Hannover, Germany
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25
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Homology models of melatonin receptors: challenges and recent advances. Int J Mol Sci 2013; 14:8093-121. [PMID: 23584026 PMCID: PMC3645733 DOI: 10.3390/ijms14048093] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 03/28/2013] [Accepted: 03/28/2013] [Indexed: 12/15/2022] Open
Abstract
Melatonin exerts many of its actions through the activation of two G protein-coupled receptors (GPCRs), named MT1 and MT2. So far, a number of different MT1 and MT2 receptor homology models, built either from the prototypic structure of rhodopsin or from recently solved X-ray structures of druggable GPCRs, have been proposed. These receptor models differ in the binding modes hypothesized for melatonin and melatonergic ligands, with distinct patterns of ligand-receptor interactions and putative bioactive conformations of ligands. The receptor models will be described, and they will be discussed in light of the available information from mutagenesis experiments and ligand-based pharmacophore models. The ability of these ligand-receptor complexes to rationalize structure-activity relationships of known series of melatonergic compounds will be commented upon.
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Kuwasako K, Hay DL, Nagata S, Hikosaka T, Kitamura K, Kato J. The third extracellular loop of the human calcitonin receptor-like receptor is crucial for the activation of adrenomedullin signalling. Br J Pharmacol 2012; 166:137-50. [PMID: 22142144 DOI: 10.1111/j.1476-5381.2011.01803.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE The extracellular loops (ECLs) in Family A GPCRs are important for ligand binding and receptor activation, but little is known about the function of Family B GPCR ECLs, especially ECL3. Calcitonin receptor-like receptor (CLR), a Family B GPCR, functions as a calcitonin gene-related peptide (CGRP) and an adrenomedullin (AM) receptor in association with three receptor activity-modifying proteins (RAMPs). Here, we examined the function of the ECL3 of human CLR within the CGRP and AM receptors. EXPERIMENTAL APPROACH A CLR ECL3 chimera, in which the ECL3 of CLR was substituted with that of VPAC2 (a Family B GPCR that is unable to interact with RAMPs), and CLR ECL3 point mutants were constructed and transiently transfected into HEK-293 cells along with each RAMP. Cell-surface expression of each receptor complex was then measured by flow cytometry; [(125) I]-CGRP and [(125) I]-AM binding and intracellular cAMP accumulation were also measured. KEY RESULTS Co-expression of the CLR ECL3 chimera with RAMP2 or RAMP3 led to significant reductions in the induction of cAMP signalling by AM, but CGRP signalling was barely affected, despite normal cell-surface expression of the receptors and normal [(125) I]-AM binding. The chimera had significantly decreased AM, but not CGRP, responses in the presence of RAMP1. Not all CLR ECL3 mutants supported these findings. CONCLUSIONS AND IMPLICATIONS The human CLR ECL3 is crucial for AM-induced cAMP responses via three CLR/RAMP heterodimers, and activation of these heterodimers probably relies on AM-induced conformational changes. This study provides a clue to the molecular basis of the activation of RAMP-based Family B GPCRs.
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Affiliation(s)
- Kenji Kuwasako
- Frontier Science Research Center, University of Miyazaki, Miyazaki, Japan.
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Abstract
Complement activation usually results in the formation of complement fragment 5a (C5a) that interacts with its two receptors, C5aR and C5L2. These receptors belong to the rhodopsin family of G protein-coupled seven transmembrane-containing receptors. C5aR and C5L2 are expressed on/in a wide variety of cells and tissues. Interaction of C5a with C5aR leads to many pleiotropic effects, including the release of cytokines and chemokines and recruitment of inflammatory cells. In certain circumstances, C5a-C5aR interactions can also result in pathophysiological changes as seen in sepsis, rheumatoid arthritis, asthma, acute lung injury and ischemia-reperfusion injury. This overview of the C5a-C5aR interactions describes how such interactions facilitate the pivotal role the complement system plays in the host's innate and adaptive responses.
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Affiliation(s)
- J Vidya Sarma
- University of Michigan Medical School, Department of Pathology, Ann Arbor, MI, USA
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The C5a receptor has a key role in immune complex glomerulonephritis in complement factor H-deficient mice. Kidney Int 2012; 82:961-8. [PMID: 22832515 PMCID: PMC3472160 DOI: 10.1038/ki.2012.249] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Chronic serum sickness leads to the formation of glomerular immune complexes; however, C57BL/6 mice do not develop glomerulonephritis unless complement factor H (CFH) is absent from the plasma. Here we studied the role for C5a receptor (R) in this setting. The exaggerated humoral immune response in CFH−/− mice was normalized in CFH−/−C5aR−/− double knockout mice, highlighting the C5aR dependence. The CFH knockout mice developed proliferative glomerulonephritis with endocapillary F4/80+ macrophage infiltration, a process reduced in the double knockout mice. There was no interstitial inflammation by histologic criteria or flow cytometry for F4/80+Ly6ChiCCR2hi inflammatory macrophages. There were, however, more interstitial CD3+CD4+ T lymphocytes in CFH knockout mice with chronic serum sickness, while double knockout mice had greater than 5-fold more Ly6CloCCR2lo anti-inflammatory macrophages compared to the CFH knockout mice. Mice lacking C5aR were significantly protected from functional renal disease as assessed by blood urea nitrogen levels. Thus, IgG- and iC3b-containing immune complexes are not inflammatory in C57BL/6 mice. Yet when these mice lack CFH, sufficient C3b persists in glomeruli to generate C5a and activate C5aR.
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29
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Rathmann D, Lindner D, DeLuca SH, Kaufmann KW, Meiler J, Beck-Sickinger AG. Ligand-mimicking receptor variant discloses binding and activation mode of prolactin-releasing peptide. J Biol Chem 2012; 287:32181-94. [PMID: 22778259 DOI: 10.1074/jbc.m112.349852] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The prolactin-releasing peptide receptor and its bioactive RF-amide peptide (PrRP20) have been investigated to explore the ligand binding mode of peptide G-protein-coupled receptors (GPCRs). By receptor mutagenesis, we identified the conserved aspartate in the upper transmembrane helix 6 (Asp(6.59)) of the receptor as the first position that directly interacts with arginine 19 of the ligand (Arg(19)). Replacement of Asp(6.59) with Arg(19) of PrRP20 led to D6.59R, which turned out to be a constitutively active receptor mutant (CAM). This suggests that the mutated residue at the top of transmembrane helix 6 mimics Arg(19) by interacting with additional binding partners in the receptor. Next, we generated an initial comparative model of this CAM because no ligand docking was required, and we selected the next set of receptor mutants to find the engaged partners of the binding pocket. In an iterative process, we identified two acidic residues and two hydrophobic residues that form the peptide ligand binding pocket. As all residues are localized on top or in the upper part of the transmembrane domains, we clearly can show that the extracellular surface of the receptor is sufficient for full signal transduction for prolactin-releasing peptide, rather than a deep, membrane-embedded binding pocket. This contributes to the knowledge of the binding of peptide ligands to GPCRs and might facilitate the development of GPCR ligands, but it also provides new targeting of CAMs involved in hereditary diseases.
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Affiliation(s)
- Daniel Rathmann
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy, and Psychology, Universität Leipzig, Brüderstrasse 34, 04103 Leipzig, Germany
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Gonzalez A, Cordomí A, Caltabiano G, Pardo L. Impact of Helix Irregularities on Sequence Alignment and Homology Modeling of G Protein-Coupled Receptors. Chembiochem 2012; 13:1393-9. [DOI: 10.1002/cbic.201200189] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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31
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Peeters MC, Wisse LE, Dinaj A, Vroling B, Vriend G, Ijzerman AP. The role of the second and third extracellular loops of the adenosine A1 receptor in activation and allosteric modulation. Biochem Pharmacol 2012; 84:76-87. [PMID: 22449615 DOI: 10.1016/j.bcp.2012.03.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 03/13/2012] [Accepted: 03/14/2012] [Indexed: 10/28/2022]
Abstract
The adenosine A1 receptor is a member of the large membrane protein family that signals through G proteins, the G protein-coupled receptors (GPCRs). GPCRs consist of seven transmembrane domains connected by three intracellular and three extracellular loops. Their N-terminus is extracellular, the C-terminal tail is in the cytoplasm. The transmembrane domains in receptor subfamilies that bind the same endogenous ligand, such as dopamine or adenosine, tend to be highly similar. In contrast, the loop regions can vary greatly, both in sequence and in length, and the role these loops have in the activation mechanism of the receptors remains unclear. Here, we investigated the activating role of the second and third extracellular loop of the human adenosine A1 receptor. By means of an (Ala)3 mutagenic scan in which consecutive sets of three amino acids were mutated into alanine residues in EL2 and a classical alanine scan in EL3, we revealed a strong regulatory role for the second extracellular loop (EL2) of the human adenosine A1 receptor. Besides many residues in the second and the third extracellular loops important for adenosine A1 receptor activation, we also identified two residues in EL2, a tryptophan and a glutamate, that affect the influence of the allosteric modulator PD81,723. These results, combined with a comparison of the different receptor loop regions, provide insight in the activation mechanism of this typical class A GPCR and further emphasize the unique pharmacological profile the loops can provide to individual receptors, even within subfamilies of GPCRs.
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Affiliation(s)
- M C Peeters
- Division of Medicinal Chemistry, Leiden/Amsterdam Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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32
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Nikiforovich GV, Baranski TJ. Structural mechanisms of constitutive activation in the C5a receptors with mutations in the extracellular loops: molecular modeling study. Proteins 2011; 80:71-80. [PMID: 21960464 DOI: 10.1002/prot.23162] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/26/2011] [Accepted: 08/19/2011] [Indexed: 12/28/2022]
Abstract
Previously we demonstrated by random saturation mutagenesis a set of mutations in the extracellular (EC) loops that constitutively activate the C5a receptor (C5aR) (Klco et al., Nat Struct Mol Biol 2005;12:320-326; Klco et al., J Biol Chem 2006;281:12010-12019). In this study, molecular modeling revealed possible conformations for the extracellular loops of the C5a receptors with mutations in the EC2 loop or in the EC3 loop. Comparison of low-energy conformations of the EC loops defined two distinct clusters of conformations typical either for strongly constitutively active mutants of C5aR (the CAM cluster) or for nonconstitutively active mutants (the non-CAM cluster). In the CAM cluster, the EC3 loop was turned towards the transmembrane (TM) helical bundle and more closely interacted with EC2 than in the non-CAM cluster. This suggested a structural mechanism of constitutive activity where EC3 contacts EC2 leading to EC2 interactions with helix TM3, thus triggering movement of TM7 towards TM2 and TM3. The movement initiates rearrangement of the system of hydrogen bonds between TM2, TM3 and TM7 including formation of the hydrogen bond between the side chains of D82(2.50) in TM2 and N296(7.49) in TM7, which is crucial for formation of the activated states of the C5a receptors (Nikiforovich et al., Proteins: Struct Funct Gene 2011;79:787-802). Since the relative large length of EC3 in C5aR (13 residues) is comparable with those in many other members of rhodopsin family of GPCRs (13-19 residues), our findings might reflect general mechanisms of receptor constitutive activation. The very recent X-ray structure of the agonist-induced constitutively active mutant of rhodopsin (Standfuss et al., Nature 2011;471:656-660) is discussed in view of our modeling results.
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Benned-Jensen T, Mokrosinski J, Rosenkilde MM. The E92K melanocortin 1 receptor mutant induces cAMP production and arrestin recruitment but not ERK activity indicating biased constitutive signaling. PLoS One 2011; 6:e24644. [PMID: 21931793 PMCID: PMC3172247 DOI: 10.1371/journal.pone.0024644] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 08/17/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The melanocortin 1 receptor (MC1R) constitutes a key regulator of melanism. Consequently, many naturally-occurring MC1R mutations are associated with a change in color. An example is the Glu-to-Lys substitution found at position II:20/2.60 in the top of transmembrane helix II which has been identified in melanic mice and several other species. This mutation induces a pronounced increase in MC1R constitutive activity suggesting a link between constitutive activity and melanism which is corroborated by the attenuation of α-melanocyte stimulating hormone (αMSH) induced activation. However, the mechanism by which the mutation induces constitutive activity is currently not known. METHODOLOGY/PRINCIPAL FINDINGS Here we characterize the constitutive activity, cell surface expression and internalization of the mouse mutant, Mc1r E92K. As previously reported, only positively charged residues at position II:20/2.60 induced an increase in constitutive activity as measured by cAMP accumulation and CREB activation. Furthermore, the mutation induced a constitutive recruitment of β-arrestin. This phenomenon is only observed in MC1R, however, as the equivalent mutations in MC2-5R had no effect on receptor signaling. Interestingly, the mutation did not induce constitutive ERK1/2 phosphorylation or increase the internalization rate indicating the constitutive activity to be biased. Finally, to identify regions of importance for the increased constitutive activity of Mc1r E92K, we employed a chimeric approach and identified G102 and L110 in the extracellular loop 1 to be selectively important for the constitutive activity as this, but not αMSH-mediated activation, was abolished upon Ala substitution. CONCLUSIONS/SIGNIFICANCE It is concluded that the E92K mutation induces an active conformation distinct from that induced by αMSH and that the extracellular loop 1 is involved in maintaining this conformational state. In turn, the results suggest that in MC1R, which lacks an extracellular loop 2, the first extracellular loop may play a more prominent role during receptor activation than in general.
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Affiliation(s)
- Tau Benned-Jensen
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacek Mokrosinski
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mette M. Rosenkilde
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
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34
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Maya-Núñez G, Janovick JA, Aguilar-Rojas A, Jardón-Valadez E, Leaños-Miranda A, Zariñan T, Ulloa-Aguirre A, Conn PM. Biochemical mechanism of pathogenesis of human gonadotropin-releasing hormone receptor mutants Thr104Ile and Tyr108Cys associated with familial hypogonadotropic hypogonadism. Mol Cell Endocrinol 2011; 337:16-23. [PMID: 21277937 PMCID: PMC3073020 DOI: 10.1016/j.mce.2011.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/18/2011] [Accepted: 01/19/2011] [Indexed: 12/28/2022]
Abstract
The pathogenic mechanisms whereby the Thr104Ile and Tyr108Cys mutations in the gonadotropin-releasing hormone receptor (GnRHR) gene cause hypogonadotropic hypogonadism in humans are unknown. Transient expression of Thr104Ile and Tyr108Cys mutants in COS-7 cells revealed that both GnRHR mutants neither bind nor respond to agonist. Removal of Lys191 rescued function of both mutants, while addition of a carboxyl-terminal targeting sequence only rescued function of the Thr104Ile mutant. Exposure to the pharmacoperone In3 rescued almost completely Thr104Ile mutant function to wild-type levels, whereas rescue was partial for the Tyr108Cys GnRHR. Additional mutations that block formation of bridges involving Cys108 showed that a Cys108-Cys200 disulfide bridge is the predominant moiety formed in the Tyr108Cys mutant. Thr104Ile and Tyr108Cys GnRHRs are misfolded structures whose function is rescuable by genetic and/or pharmacological strategies. The Tyr108Cys mutant forms an aberrant disulfide bridge that prevents formation of the required Cys14-Cys200 bridge essential for GnRHR plasma membrane expression.
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Affiliation(s)
- Guadalupe Maya-Núñez
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Jo Ann Janovick
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
| | - Arturo Aguilar-Rojas
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Centro de Investigación Biomédica del Sur (CIBIS), Instituto Mexicano del Seguro Social, Xochitepec, Mor., Mexico
| | - Eduardo Jardón-Valadez
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Alfredo Leaños-Miranda
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Teresa Zariñan
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Alfredo Ulloa-Aguirre
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
| | - P. Michael Conn
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
- Departments of Physiology and Pharmacology, Cell and Development Biology and Obstetrics and Gynecology, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR.97239
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Nikiforovich GV, Marshall GR, Baranski TJ. Simplified modeling approach suggests structural mechanisms for constitutive activation of the C5a receptor. Proteins 2010; 79:787-802. [PMID: 21287612 DOI: 10.1002/prot.22918] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 10/11/2010] [Accepted: 10/13/2010] [Indexed: 11/07/2022]
Abstract
Molecular modeling of conformational changes occurring in the transmembrane region of the complement factor 5a receptor (C5aR) during receptor activation was performed by comparing two constitutively active mutants (CAMs) of C5aR, NQ (I124N/L127Q), and F251A, to those of the wild-type C5aR and NQ-N296A (I124N/L127Q/N296A), which have the wild-type phenotype. Modeling involved comprehensive sampling of various rotations of TM helices aligned to the crystal template of the dark-adapted rhodopsin along their long axes. By assuming that the relative energies of the spontaneously activated states of CAMs should be lower or at least comparable to energies characteristic for the ground states, we selected the plausible models for the conformational states associated with constitutive activation in C5aR. The modeling revealed that the hydrogen bonds between the side chains of D82-N119, S85-N119, and S131-C221 characteristic for the ground state were replaced by the hydrogen bonds D82-N296, N296-Y300, and S131-R134, respectively, in the activated states. Also, conformational transitions that occurred upon activation were hindered by contacts between the side chains of L127 and F251. The results rationalize the available data of mutagenesis in C5aR and offer the first specific molecular mechanism for the loss of constitutive activity in NQ-N296A. Our results also contributed to understanding the general structural mechanisms of activation in G-protein-coupled receptors lacking the "ionic lock", R(3.50) and E/D(6.30). Importantly, these results were obtained by modeling approaches that deliberately simplify many elements in order to explore potential conformations of GPCRs involving large-scale molecular movements.
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Peeters MC, Westen GJP, Guo D, Wisse LE, Muller CE, Beukers MW, IJzerman AP. GPCR structure and activation: an essential role for the first extracellular loop in activating the adenosine A
2B
receptor. FASEB J 2010; 25:632-43. [DOI: 10.1096/fj.10-164319] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Miriam C. Peeters
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
| | - Gerard J. P. Westen
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
| | - Dong Guo
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
| | - Lisanne E. Wisse
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
| | - Christa E. Muller
- PharmaCenter BonnPharmaceutical InstitutePharmaceutical Chemistry IPharmaceutical Sciences Bonn (PSB)University of BonnBonnGermany
| | - Margot W. Beukers
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
| | - Adriaan P. IJzerman
- Division of Medicinal ChemistryLeiden/Amsterdam Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands
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Rana S, Baranski TJ. Third extracellular loop (EC3)-N terminus interaction is important for seven-transmembrane domain receptor function: implications for an activation microswitch region. J Biol Chem 2010; 285:31472-83. [PMID: 20663868 DOI: 10.1074/jbc.m110.129213] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The canonical heptahelical bundle architecture of seven-transmembrane domain (7TM) receptors is intertwined by three intra- and three extracellular loops, whose local conformations are important in receptor signaling. Many 7TM receptors contain a cysteine residue in the third extracellular loop (EC3) and a complementary cysteine residue on the N terminus. The functional role of such EC3-N terminus conserved cysteine pairs remains unclear. This study explores the role of the EC3-N terminus cysteine pairs on receptor conformation and G protein activation by disrupting them in the chemokine receptor CXCR4, while engineering a novel EC3-N terminus cysteine pair into the complement factor 5a receptor (C5aR), a chemo attractant receptor that lacks it. Mutated CXCR4 and C5aRs were expressed in engineered yeast. Mutation of the cysteine pair with the serine pair (C28S/C274S) in constitutively active mutant CXCR4 abrogated the receptor activation, whereas mutation with the aromatic pair (C28F-C274F) or the salt bridge pair (C28R/C274E), respectively, rescued or retained the receptor activation in response to CXCL12. In this context, the cysteine pair (Cys(30) and Cys(272)) engineered into the EC3-N terminus (Ser(30) and Ser(272)) of a novel constitutively active mutant of C5aR restrained the constitutive signaling without affecting the C5a-induced activation. Further mutational studies demonstrated a previously unappreciated role for Ser(272) on EC3 of C5aR and its interaction with the N terminus, thus defining a new microswitch region within the C5aR. Similar results were obtained with mutated CXCR4 and C5aRs expressed in COS-7 cells. These studies demonstrate a novel role of the EC3-N terminus cysteine pairs in G protein-coupled receptor activation and signaling.
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Affiliation(s)
- Soumendra Rana
- Division of Metabolism, Endocrinology, and Lipid Research, Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA
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Tantry S, Ding FX, Dumont M, Becker JM, Naider F. Binding of fluorinated phenylalanine alpha-factor analogues to Ste2p: evidence for a cation-pi binding interaction between a peptide ligand and its cognate G protein-coupled receptor. Biochemistry 2010; 49:5007-15. [PMID: 20420459 DOI: 10.1021/bi100280f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ste2p, a G protein-coupled receptor (GPCR), binds alpha-factor, WHWLQLKPGQPMY, a tridecapeptide pheromone secreted by yeast cells. Upon alpha-factor binding, Ste2p undergoes conformational changes activating a signal transduction system through its associated heterotrimeric G protein leading to the arrest of cell growth in the G1 phase to prepare cells for mating. Previous studies have indicated that Tyr at position 13 of alpha-factor interacts with Arg58 on transmembrane one (TM1) of Ste2p. This observation prompted this investigation to determine whether a cation-pi type of interaction occurred between these residues. Tyrosine at position 13 of alpha-factor was systematically substituted with analogous amino acids with varying cation-pi binding energies using solid-phase peptide synthesis, and these analogues were modified by derivatization of their Lys(7) residue with the fluorescent group 7-nitrobenz-2-oxa-1,3-diazole (NBD) to serve as a useful probe for binding determination. Saturation binding of these peptides to Ste2p was assayed using whole yeast cells and a flow cytometer. In parallel the biological activities of the peptides were determined using a growth arrest assay. The data provide evidence for the presence of a cation-pi interaction between Arg58 of Ste2p and Tyr(13) of alpha-factor.
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Affiliation(s)
- Subramanyam Tantry
- Department of Chemistry, College of Staten Island of the City University of New York, Staten Island, New York 10314, USA
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Fillion D, Lemieux G, Basambombo LL, Lavigne P, Guillemette G, Leduc R, Escher E. The amino-terminus of angiotensin II contacts several ectodomains of the angiotensin II receptor AT1. J Med Chem 2010; 53:2063-75. [PMID: 20146480 DOI: 10.1021/jm9015747] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and major targets for drug development. Herein, we sought to identify the regions of the human angiotensin II (AngII) type 1 (hAT(1)) receptor binding cleft that interact with all positions of the AngII using photoaffinity labeling. We conducted a complete iterative walk-through of the AngII sequence with either p-benzoyl-L-phenylalanine (Bpa) or p-[3-(trifluoromethyl)-3H-diazirin-3-yl]-L-phenylalanine (Tdf) to yield two series of eight photoreactive analogues. Pharmacological properties assessment of these sixteen analogues showed that the CAM receptor has a structure-activity relationship (SAR) more amenable to the amino acid substitutions at positions 1, 2, 3, and 5 of AngII than the WT receptor. Photoaffinity labeling of the CAM receptor with the selected analogues, which exhibit different but complementary photochemical properties, suggested that the AngII amino-terminus resides in a hydrophilic environment and interacts simultaneously with different regions of the hAT(1) receptor, including several ectodomains.
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Affiliation(s)
- Dany Fillion
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Universite de Sherbrooke, Sherbrooke, QC, Canada
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40
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Togawa S, Ishii J, Ishikura A, Tanaka T, Ogino C, Kondo A. Importance of asparagine residues at positions 13 and 26 on the amino-terminal domain of human somatostatin receptor subtype-5 in signalling. J Biochem 2010; 147:867-73. [DOI: 10.1093/jb/mvq022] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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41
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Iguchi Y, Ishii J, Nakayama H, Ishikura A, Izawa K, Tanaka T, Ogino C, Kondo A. Control of signalling properties of human somatostatin receptor subtype-5 by additional signal sequences on its amino-terminus in yeast. J Biochem 2010; 147:875-84. [DOI: 10.1093/jb/mvq023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Clark SD, Tran HT, Zeng J, Reinscheid RK. Importance of extracellular loop one of the neuropeptide S receptor for biogenesis and function. Peptides 2010; 31:130-8. [PMID: 19874863 PMCID: PMC2814945 DOI: 10.1016/j.peptides.2009.10.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 10/16/2009] [Accepted: 10/16/2009] [Indexed: 01/25/2023]
Abstract
Neuropeptide S (NPS) is the endogenous ligand of a formerly orphan G protein-coupled receptor (GPCR). The NPS receptor (NPSR) belongs to the subfamily of peptide GPCRs and is widely expressed in the brain. NPS promotes arousal and induces anxiolytic-like effects after central administration in rodents. Previously, we have reported that the N107I polymorphism in the human NPS receptor results in a gain-of-function characterized by an increase in agonist potency without changing agonist binding affinity. We have extended our findings by investigating pharmacological and biochemical consequences of mutations in the vicinity of position 107. Alanine substitutions were made for D105 and N101, and stable clones were analyzed for agonist-induced changes of intracellular Ca(2+). Receptor protein expression was monitored by Western blot and flow cytometry. The mutation D105A produced receptors that have a approximately 200-fold higher EC(50) despite elevated total receptor protein and surface expression compared to cell lines expressing the parental receptor NPSR-N107. The mutation N101A resulted in slightly reduced agonist potency without affecting the ability of the protein to form functional receptors. Stable NPSR-A101 clones show little expression of the fully glycosylated form. However, NPSR-A101 receptors are expressed on the cell surface and are functional, suggesting that full glycosylation is not required for receptor function. Our studies suggest that N-linked glycosylation is not important for receptor biogenesis or function, and that residue D105 might be critical for receptor binding.
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Affiliation(s)
- Stewart D. Clark
- Pharmaceutical Sciences, University of California, Irvine, 147 Biological Sciences Administration, Irvine, CA 92697, USA
| | - Ha T. Tran
- Pharmaceutical Sciences, University of California, Irvine, 147 Biological Sciences Administration, Irvine, CA 92697, USA
| | - Joanne Zeng
- Pharmaceutical Sciences, University of California, Irvine, 147 Biological Sciences Administration, Irvine, CA 92697, USA
| | - Rainer K. Reinscheid
- Pharmaceutical Sciences, University of California, Irvine, 147 Biological Sciences Administration, Irvine, CA 92697, USA
- Department of Pharmacology, University of California, Irvine, 360 Med Surge II, Irvine, CA 92697, USA
- Department of Molecular Biology and Biochemistry, 3205 McGaugh Hall, University of California, Irvine, CA 92697, USA
- Corresponding author: Rainer K. Reinscheid, Phone: (949) 824-9228, Fax: (949) 824-4855, , University of California, Department of Pharmaceutical Sciences, 310C Med Surge 2, Irvine, CA 92697
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43
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Rihakova L, Quiniou C, Hamdan FF, Kaul R, Brault S, Hou X, Lahaie I, Sapieha P, Hamel D, Shao Z, Gobeil F, Hardy P, Joyal JS, Nedev H, Duhamel F, Beauregard K, Heveker N, Saragovi HU, Guillon G, Bouvier M, Lubell WD, Chemtob S. VRQ397 (CRAVKY): a novel noncompetitive V2 receptor antagonist. Am J Physiol Regul Integr Comp Physiol 2009; 297:R1009-18. [PMID: 19641130 DOI: 10.1152/ajpregu.90766.2008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vasopressin type 2 receptor (V2R) exhibits mostly important properties for hydroosmotic equilibrium and, to a lesser extent, on vasomotricity. Drugs currently acting on this receptor are analogs of the natural neuropeptide, arginine vasopressin (AVP), and hence are competitive ligands. Peptides that reproduce specific sequences of a given receptor have lately been reported to interfere with its action, and if such molecules arise from regions remote from the binding site they would be anticipated to exhibit noncompetitive antagonism, but this has yet to be shown for V2R. Six peptides reproducing juxtamembranous regions of V2R were designed and screened; the most effective peptide, cravky (labeled VRQ397), was characterized. VRQ397 was potent (IC(50) = 0.69 +/- 0.25 nM) and fully effective in inhibiting V2R-dependent physiological function, specifically desmopressin-L-desamino-8-arginine-vasopressin (DDAVP)-induced cremasteric vasorelaxation; this physiological functional assay was utilized to avoid overlooking interference of specific signaling events. A dose-response profile revealed a noncompetitive property of VRQ397; correspondingly, VRQ397 bound specifically to V2R-expressing cells could not displace its natural ligand, AVP, but modulated AVP binding kinetics (dissociation rate). Specificity of VRQ397 was further confirmed by its inability to bind to homologous V1 and oxytocin receptors and its inefficacy to alter responses to stimulation of these receptors. VRQ397 exhibited pharmacological permissiveness on V2R-induced signals, as it inhibited DDAVP-induced PGI(2) generation but not that of cAMP or recruitment of beta-arrestin2. Consistent with in vitro and ex vivo effects as a V2R antagonist, VRQ397 displayed anticipated in vivo aquaretic efficacy. We hereby describe the discovery of a first potent noncompetitive antagonist of V2R, which exhibits functional selectivity, in line with properties of a negative allosteric modulator.
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Affiliation(s)
- L Rihakova
- Departments of Pediatrics and Pharmacology, Hôpital Ste Justine, Research Center, Montreal, QC, Canada
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44
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Klos A, Tenner AJ, Johswich KO, Ager RR, Reis ES, Köhl J. The role of the anaphylatoxins in health and disease. Mol Immunol 2009; 46:2753-66. [PMID: 19477527 DOI: 10.1016/j.molimm.2009.04.027] [Citation(s) in RCA: 501] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Accepted: 04/28/2009] [Indexed: 12/16/2022]
Abstract
The anaphylatoxin (AT) C3a, C5a and C5a-desArg are generally considered pro-inflammatory polypeptides generated after proteolytic cleavage of C3 and C5 in response to complement activation. Their well-appreciated effector functions include chemotaxis and activation of granulocytes, mast cells and macrophages. Recent evidence suggests that ATs are also generated locally within tissues by pathogen-, cell-, or contact system-derived proteases. This local generation of ATs is important for their pleiotropic biologic effects beyond inflammation. The ATs exert most of the biologic activities through ligation of three cognate receptors, i.e. the C3a receptor, the C5a receptor and the C5a receptor-like, C5L2. Here, we will discuss recent findings suggesting that ATs regulate cell apoptosis, lipid metabolism as well as innate and adaptive immune responses through their impact on antigen-presenting cells and T cells. As we will outline, such regulatory functions of ATs and their receptors play important roles in the pathogenesis of allergy, autoimmunity, neurodegenerative diseases, cancer and infections with intracellular pathogens.
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Affiliation(s)
- Andreas Klos
- Institute of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, MHH, Germany
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45
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Härterich S, Koschatzky S, Einsiedel J, Gmeiner P. Novel insights into GPCR—Peptide interactions: Mutations in extracellular loop 1, ligand backbone methylations and molecular modeling of neurotensin receptor 1. Bioorg Med Chem 2008; 16:9359-68. [DOI: 10.1016/j.bmc.2008.08.051] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 08/22/2008] [Indexed: 11/24/2022]
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46
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Hagemann IS, Miller DL, Klco JM, Nikiforovich GV, Baranski TJ. Structure of the Complement Factor 5a Receptor-Ligand Complex Studied by Disulfide Trapping and Molecular Modeling. J Biol Chem 2008; 283:7763-75. [DOI: 10.1074/jbc.m709467200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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47
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Nikiforovich GV, Marshall GR, Baranski TJ. Modeling molecular mechanisms of binding of the anaphylatoxin C5a to the C5a receptor. Biochemistry 2008; 47:3117-30. [PMID: 18275159 DOI: 10.1021/bi702321a] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study presents the 3D model of the complex between the anaphylatoxin C5a and its specific receptor, C5aR. This is the first 3D model of a G-protein-coupled receptor (GPCR) complex with a peptide ligand deduced by a molecular modeling procedure analyzing various conformational possibilities of the extracellular loops and the N-terminal segment of the GPCR. The modeling results indicated two very different ways of interacting between C5a and C5aR at the two interaction sites suggested earlier based on the data of site-directed mutagenesis. Specifically, C5a and C5aR can be involved in "mutual-induced fit", where the interface between the molecules is determined by both the receptor and the ligand. The rigid core of the C5a ligand selects the proper conformations of the highly flexible N-terminal segment of C5aR (the first interaction site). At the same time, the binding conformation of the flexible C-terminal fragment of C5a is selected by well-defined interactions with the TM region of the C5aR receptor (the second interaction site). The proposed 3D model of C5a/C5aR complex was built without direct use of structural constraints derived from site-directed mutagenesis reserving those data for validation of the model. The available data of site-directed mutagenesis of C5a and C5aR were successfully rationalized with the help of the model. Also, the modeling results predicted that the full-length C5a and C5a-des74 metabolite would have different binding modes with C5aR. Modeling approaches employed in this study are readily applicable for studies of molecular mechanisms of binding of other polypeptide ligands to their specific GPCRs.
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Affiliation(s)
- Gregory V Nikiforovich
- Center for Computational Biology, Department of Biochemistry and Molecular Biophysics, Washington University Medical School, St. Louis, Missouri 63110, USA.
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Sen S, Baranski TJ, Nikiforovich GV. Conformational movement of F251 contributes to the molecular mechanism of constitutive activation in the C5a receptor. Chem Biol Drug Des 2008; 71:197-204. [PMID: 18248350 DOI: 10.1111/j.1747-0285.2008.00630.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The activation mechanism of G-protein-coupled receptors triggered upon binding of a ligand represents a very important 'conformational switch' in the biological array of signal transduction. However, the molecular and functional details for this activation switch remain unknown. Random saturation mutagenesis data on the complement factor 5a receptor has provided a large data set of mutants including several constitutively active mutants. In the present study, we employed computational modeling to rationalize the constitutive activity for two constitutively active mutants, NQ (I124N/L127Q) and F251A, and we then made predictions for a series of mutants that either promote or constrain constitutive activity. Biological testing of the site-directed mutants confirmed most of the predictions of the computational modeling. These results support a molecular mechanism of constitutive activity in complement factor 5a receptor mutants that is associated with conformational changes in a network of residues neighboring F251 as the focal point of origin.
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Affiliation(s)
- Saurabh Sen
- Division of Endocrinology, Metabolism and Lipid Research, Department of Internal Medicine, Washington University School of Medicine, Box 8127, St Louis, MO 63110, USA
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49
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Monk PN, Scola AM, Madala P, Fairlie DP. Function, structure and therapeutic potential of complement C5a receptors. Br J Pharmacol 2007; 152:429-48. [PMID: 17603557 PMCID: PMC2050825 DOI: 10.1038/sj.bjp.0707332] [Citation(s) in RCA: 297] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Complement fragment (C)5a is a 74 residue pro-inflammatory polypeptide produced during activation of the complement cascade of serum proteins in response to foreign surfaces such as microorganisms and tissue damaged by physical or chemical injury. C5a binds to at least two seven-transmembrane domain receptors, C5aR (C5R1, CD88) and C5L2 (gpr77), expressed ubiquitously on a wide variety of cells but particularly on the surface of immune cells like macrophages, neutrophils and T cells. C5aR is a classical G protein-coupled receptor that signals through G alpha i and G alpha 16, whereas C5L2 does not appear to couple to G proteins and has no known signalling activity. Although C5a was first described as an anaphylatoxin and later as a leukocyte chemoattractant, the widespread expression of C5aR suggested more general functionality. Our understanding of the physiology of C5a has improved significantly in recent years through exploitation of receptor knockout and knocking mice, C5 and C5a antibodies, soluble recombinant C5a and C5a analogues and newly developed receptor antagonists. C5a is now also implicated in non-immunological functions associated with developmental biology, CNS development and neurodegeneration, tissue regeneration, and haematopoiesis. Combined receptor mutagenesis, molecular modelling, structure-activity relationship studies and species dependence for ligand potency on C5aR have been helpful for identifying ligand binding sites on the receptor and for defining mechanisms of receptor activation and inactivation. This review will highlight major developments in C5a receptor research that support C5aR as an important therapeutic target. The intriguing possibilities raised by the existence of a non-signalling C5a receptor are also discussed.
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Affiliation(s)
- P N Monk
- Academic Neurology Unit, School of Medicine and Biomedical Science, University of Sheffield, Sheffield, UK.
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50
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Abstract
The complement system is an important component of the innate immune system and a modulator of adaptive immunity. The entire complement system is focused on C3 and C5. Thus, there are proteins that activate C3 and C5, those that regulate this activation, and those that transduce the effects of C3 and C5 activation products; each can affect the kidney in renal injury. The normal kidney has the inherent capacity to protect itself from complement activation through cellular expression of decay-accelerating factor, membrane cofactor protein (in human beings), and Crry (in rodents). In addition, plasma factor H protects vascular spaces in the kidney. Although the main function of these proteins is to limit complement activation, there is now considerable evidence that they can transduce signals on engagement in immune cells. The G-protein-coupled 7-span transmembrane receptors for C3a and C5a, and the integral membrane complement receptors (CR) for C3b, iC3b, and C3dg, are expressed outside the kidney, particularly in cells of hematopoietic and immune lineage. These are important in renal injury through their infiltration of the kidney and/or by affecting kidney-directed immune responses. There is mounting evidence that intrinsic glomerular and tubular cell C3aR and C5aR expression and activation also can affect renal injury. CR1 on podocytes and the beta2 integrins CR3 and CR4 in kidney dendritic cells have functions that remain poorly defined. Cells of the kidney also have the capacity to produce and activate their own complement proteins. Thus, intrinsic renal cells express decay-accelerating factor, membrane cofactor protein, Crry, C3aR, C5aR, CR1, CR3, and CR4. These can be engaged by C3 and C5 activation products derived from systemic and local pools in renal injury. Given their capacity to provide signals that influence kidney cellular behavior, their activation can have substantial effects in renal injury. Defining these in a cell- and disease-specific fashion is an exciting challenge for future research.
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Affiliation(s)
- Tipu S Puri
- Section of Nephrology, University of Chicago, Chicago, IL 60637, USA
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