1
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Deichmann M, Hansson FG, Jensen ED. Yeast-based screening platforms to understand and improve human health. Trends Biotechnol 2024; 42:1258-1272. [PMID: 38677901 DOI: 10.1016/j.tibtech.2024.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 04/01/2024] [Accepted: 04/03/2024] [Indexed: 04/29/2024]
Abstract
Detailed molecular understanding of the human organism is essential to develop effective therapies. Saccharomyces cerevisiae has been used extensively for acquiring insights into important aspects of human health, such as studying genetics and cell-cell communication, elucidating protein-protein interaction (PPI) networks, and investigating human G protein-coupled receptor (hGPCR) signaling. We highlight recent advances and opportunities of yeast-based technologies for cost-efficient chemical library screening on hGPCRs, accelerated deciphering of PPI networks with mating-based screening and selection, and accurate cell-cell communication with human immune cells. Overall, yeast-based technologies constitute an important platform to support basic understanding and innovative applications towards improving human health.
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Affiliation(s)
- Marcus Deichmann
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Frederik G Hansson
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Emil D Jensen
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
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2
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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] [MESH Headings] [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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3
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Lengger B, Jensen MK. Engineering G protein-coupled receptor signalling in yeast for biotechnological and medical purposes. FEMS Yeast Res 2021; 20:5673487. [PMID: 31825496 PMCID: PMC6977407 DOI: 10.1093/femsyr/foz087] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 12/09/2019] [Indexed: 12/13/2022] Open
Abstract
G protein-coupled receptors (GPCRs) comprise the largest class of membrane proteins in the human genome, with a common denominator of seven-transmembrane domains largely conserved among eukaryotes. Yeast is naturally armoured with three different GPCRs for pheromone and sugar sensing, with the pheromone pathway being extensively hijacked for characterising heterologous GPCR signalling in a model eukaryote. This review focusses on functional GPCR studies performed in yeast and on the elucidated hotspots for engineering, and discusses both endogenous and heterologous GPCR signalling. Key emphasis will be devoted to studies describing important engineering parameters to consider for successful coupling of GPCRs to the yeast mating pathway. We also review the various means of applying yeast for studying GPCRs, including the use of yeast armed with heterologous GPCRs as a platform for (i) deorphanisation of orphan receptors, (ii) metabolic engineering of yeast for production of bioactive products and (iii) medical applications related to pathogen detection and drug discovery. Finally, this review summarises the current challenges related to expression of functional membrane-bound GPCRs in yeast and discusses the opportunities to continue capitalising on yeast as a model chassis for functional GPCR signalling studies.
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Affiliation(s)
- Bettina Lengger
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet, Building 220, Kgs. Lyngby, 2800, Denmark
| | - Michael K Jensen
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet, Building 220, Kgs. Lyngby, 2800, Denmark
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4
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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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5
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Engineering a Model Cell for Rational Tuning of GPCR Signaling. Cell 2019; 177:782-796.e27. [PMID: 30955892 PMCID: PMC6476273 DOI: 10.1016/j.cell.2019.02.023] [Citation(s) in RCA: 107] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/20/2018] [Accepted: 02/13/2019] [Indexed: 12/18/2022]
Abstract
G protein-coupled receptor (GPCR) signaling is the primary method eukaryotes use to respond to specific cues in their environment. However, the relationship between stimulus and response for each GPCR is difficult to predict due to diversity in natural signal transduction architecture and expression. Using genome engineering in yeast, we constructed an insulated, modular GPCR signal transduction system to study how the response to stimuli can be predictably tuned using synthetic tools. We delineated the contributions of a minimal set of key components via computational and experimental refactoring, identifying simple design principles for rationally tuning the dose response. Using five different GPCRs, we demonstrate how this enables cells and consortia to be engineered to respond to desired concentrations of peptides, metabolites, and hormones relevant to human health. This work enables rational tuning of cell sensing while providing a framework to guide reprogramming of GPCR-based signaling in other systems.
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6
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Liu H, Kim HR, Deepak RNVK, Wang L, Chung KY, Fan H, Wei Z, Zhang C. Orthosteric and allosteric action of the C5a receptor antagonists. Nat Struct Mol Biol 2018; 25:472-481. [PMID: 29867214 DOI: 10.1038/s41594-018-0067-z] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/16/2018] [Indexed: 01/09/2023]
Abstract
The C5a receptor (C5aR) is a G-protein-coupled receptor (GPCR) that can induce strong inflammatory response to the anaphylatoxin C5a. Targeting C5aR has emerged as a novel anti-inflammatory therapeutic method. However, developing potent C5aR antagonists as drugs has proven difficult. Here, we report two crystal structures of human C5aR in ternary complexes with the peptide antagonist PMX53 and a non-peptide antagonist, either avacopan or NDT9513727. The structures, together with other biophysical, computational docking and cell-based signaling data, reveal the orthosteric action of PMX53 and its effect of stabilizing the C5aR structure, as well as the allosteric action of chemically diverse non-peptide C5aR antagonists with different binding poses. Structural comparison analysis suggests the presence of similar allosteric sites in other GPCRs. We also discuss critical structural features of C5aR in activation, including a novel conformation of helix 8. On the basis of our results, we suggest novel strategies for developing C5aR-targeting drugs.
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Affiliation(s)
- Heng Liu
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, Suwon, Republic of Korea
| | - R N V Krishna Deepak
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Lei Wang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon, Republic of Korea
| | - Hao Fan
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Zhiyi Wei
- Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Cheng Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
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7
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Zhang J, Yang J, Jang R, Zhang Y. GPCR-I-TASSER: A Hybrid Approach to G Protein-Coupled Receptor Structure Modeling and the Application to the Human Genome. Structure 2015; 23:1538-1549. [PMID: 26190572 DOI: 10.1016/j.str.2015.06.007] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 06/03/2015] [Accepted: 06/10/2015] [Indexed: 12/31/2022]
Abstract
Experimental structure determination remains difficult for G protein-coupled receptors (GPCRs). We propose a new hybrid protocol to construct GPCR structure models that integrates experimental mutagenesis data with ab initio transmembrane (TM) helix assembly simulations. The method was tested on 24 known GPCRs where the ab initio TM-helix assembly procedure constructed the correct fold for 20 cases. When combined with weak homology and sparse mutagenesis restraints, the method generated correct folds for all the tested cases with an average Cα root-mean-square deviation 2.4 Å in the TM regions. The new hybrid protocol was applied to model all 1,026 GPCRs in the human genome, where 923 have a high confidence score and are expected to have correct folds; these contain many pharmaceutically important families with no previously solved structures, including Trace amine, Prostanoids, Releasing hormones, Melanocortins, Vasopressin, and Neuropeptide Y receptors. The results demonstrate new progress on genome-wide structure modeling of TM proteins.
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Affiliation(s)
- Jian Zhang
- Department of Computational Medicine and Bioinformatics, University of Michigan, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA
| | - Jianyi Yang
- Department of Computational Medicine and Bioinformatics, University of Michigan, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA; School of Mathematical Sciences and LPMC, Nankai University, Tianjin 300071, China
| | - Richard Jang
- Department of Computational Medicine and Bioinformatics, University of Michigan, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA
| | - Yang Zhang
- Department of Computational Medicine and Bioinformatics, University of Michigan, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
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8
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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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9
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Domains for activation and inactivation in G protein-coupled receptors – A mutational analysis of constitutive activity of the adenosine A2B receptor. Biochem Pharmacol 2014; 92:348-57. [DOI: 10.1016/j.bcp.2014.08.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 11/18/2022]
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10
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Lua RC, Marciano DC, Katsonis P, Adikesavan AK, Wilkins AD, Lichtarge O. Prediction and redesign of protein-protein interactions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:194-202. [PMID: 24878423 DOI: 10.1016/j.pbiomolbio.2014.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/02/2014] [Accepted: 05/17/2014] [Indexed: 12/14/2022]
Abstract
Understanding the molecular basis of protein function remains a central goal of biology, with the hope to elucidate the role of human genes in health and in disease, and to rationally design therapies through targeted molecular perturbations. We review here some of the computational techniques and resources available for characterizing a critical aspect of protein function - those mediated by protein-protein interactions (PPI). We describe several applications and recent successes of the Evolutionary Trace (ET) in identifying molecular events and shapes that underlie protein function and specificity in both eukaryotes and prokaryotes. ET is a part of analytical approaches based on the successes and failures of evolution that enable the rational control of PPI.
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Affiliation(s)
- Rhonald C Lua
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - David C Marciano
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Panagiotis Katsonis
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Anbu K Adikesavan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Angela D Wilkins
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Computational and Integrative Biomedical Research Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Olivier Lichtarge
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Computational and Integrative Biomedical Research Center, Baylor College of Medicine, Houston, TX 77030, USA.
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11
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Tehan BG, Bortolato A, Blaney FE, Weir MP, Mason JS. Unifying family A GPCR theories of activation. Pharmacol Ther 2014; 143:51-60. [PMID: 24561131 DOI: 10.1016/j.pharmthera.2014.02.004] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 02/05/2014] [Indexed: 10/25/2022]
Abstract
Several new pairs of active and inactive GPCR structures have recently been solved enabling detailed structural insight into the activation process, not only of rhodopsin but now also of the β2 adrenergic, M2 muscarinic and adenosine A2A receptors. Combined with structural analyses they have enabled us to examine the different recent theories proposed for GPCR activation and show that they are all indeed parts of the same process, and are intrinsically related through their effect on the central hydrophobic core of GPCRs. This new unifying general process of activation is consistent with the identification of known constitutively active mutants and an in-depth conservational analysis of significant residues implicated in the process.
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Affiliation(s)
- Benjamin G Tehan
- Heptares Therapeutics BioPark, Broadwater Road, Welwyn Garden City AL7 3AX United Kingdom.
| | - Andrea Bortolato
- Heptares Therapeutics BioPark, Broadwater Road, Welwyn Garden City AL7 3AX United Kingdom
| | - Frank E Blaney
- Heptares Therapeutics BioPark, Broadwater Road, Welwyn Garden City AL7 3AX United Kingdom
| | - Malcolm P Weir
- Heptares Therapeutics BioPark, Broadwater Road, Welwyn Garden City AL7 3AX United Kingdom
| | - Jonathan S Mason
- Heptares Therapeutics BioPark, Broadwater Road, Welwyn Garden City AL7 3AX United Kingdom
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12
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Ishii J, Oda A, Togawa S, Fukao A, Fujiwara T, Ogino C, Kondo A. Microbial fluorescence sensing for human neurotensin receptor type 1 using Gα-engineered yeast cells. Anal Biochem 2014; 446:37-43. [DOI: 10.1016/j.ab.2013.10.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 10/04/2013] [Accepted: 10/10/2013] [Indexed: 12/12/2022]
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13
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Nichols AS, Floyd DH, Bruinsma SP, Narzinski K, Baranski TJ. Frizzled receptors signal through G proteins. Cell Signal 2013; 25:1468-75. [PMID: 23524329 PMCID: PMC3640709 DOI: 10.1016/j.cellsig.2013.03.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 02/23/2013] [Accepted: 03/06/2013] [Indexed: 10/27/2022]
Abstract
Frizzled receptors have long been thought to couple to G proteins but biochemical evidence supporting such an interaction has been lacking. Here we expressed mammalian Wnt-Frizzled fusion proteins in Saccharomyces cerevisiae and tested the receptors' ability to activate the yeast mitogen-activated protein kinase (MAPK) pathway via heterotrimeric G proteins. Our results show that Frizzled receptors can interact with Gαi, Gαq, and Gαs proteins, thus confirming that Frizzled functions as a G protein coupled receptor (GPCR). However, the activity level of Frizzled-mediated G protein signaling was much lower than that of a typical GPCR and, surprisingly, was highest when coupled to Gαs. The Frizzled/Gαs interaction was further established in vivo as Drosophila expressing a loss-of-function Gαs allele rescued the photoreceptor differentiation phenotype of Frizzled mutant flies. Together, these data point to an important role for Frizzled as a nontraditional GPCR that preferentially couples to Gαs heterotrimeric G proteins.
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Affiliation(s)
- Andrea S. Nichols
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Desiree H. Floyd
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Stephen P. Bruinsma
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Kirk Narzinski
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Thomas J. Baranski
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
- Department of Developmental Biology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
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14
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Furukawa K, Hohmann S. Synthetic biology: lessons from engineering yeast MAPK signalling pathways. Mol Microbiol 2013; 88:5-19. [PMID: 23461595 DOI: 10.1111/mmi.12174] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/04/2013] [Indexed: 02/04/2023]
Abstract
All living cells respond to external stimuli and execute specific physiological responses through signal transduction pathways. Understanding the mechanisms controlling signalling pathways is important for diagnosing and treating diseases and for reprogramming cells with desired functions. Although many of the signalling components in the budding yeast Saccharomyces cerevisiae have been identified by genetic studies, many features concerning the dynamic control of pathway activity, cross-talk, cell-to-cell variability or robustness against perturbation are still incompletely understood. Comparing the behaviour of engineered and natural signalling pathways offers insight complementary to that achievable with standard genetic and molecular studies. Here, we review studies that aim at a deeper understanding of signalling design principles and generation of novel signalling properties by engineering the yeast mitogen-activated protein kinase (MAPK) pathways. The underlying approaches can be applied to other organisms including mammalian cells and offer opportunities for building synthetic pathways and functionalities useful in medicine and biotechnology.
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Affiliation(s)
- Kentaro Furukawa
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden.
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15
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Caltabiano G, Gonzalez A, Cordomí A, Campillo M, Pardo L. The Role of Hydrophobic Amino Acids in the Structure and Function of the Rhodopsin Family of G Protein-Coupled Receptors. Methods Enzymol 2013; 520:99-115. [DOI: 10.1016/b978-0-12-391861-1.00005-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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16
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Abstract
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor critical for maintaining energy homeostasis. Transmembrane domain 3 (TM3) of MC4R contains residues that were suggested to be essential in ligand binding and signaling. Several MC4R mutations in TM3 are associated with human obesity. To gain a better understanding of the functions of TM3, we analyzed the functions of 26 residues in TM3 using alanine-scanning mutagenesis. We showed that all mutants had normal cell-surface expression. Four mutants were defective in ligand binding and signaling and six mutants had normal ligand binding but impaired cAMP production. L140A had increased basal cAMP level. To further characterize the function of L140, we generated 17 additional L140 mutants. Fifteen L140 mutants had significantly decreased cell-surface expression, with L140R and L140V expressed normally. Ten L140 mutants had increased basal cAMP activities. Four L140 mutants were defective in ligand-stimulated cAMP generation. Interestingly, with the ERK1/2 pathway, we showed that nine constitutively active mutants had similar levels of basal pERK1/2 as that of WT, and two signaling defective mutants had similar levels of pERK1/2 as that of WT upon agonist stimulation, different from their cAMP signaling properties, suggesting biased signaling in these mutant receptors. In summary, we identified 13 residues in TM3 that were essential for ligand binding and/or signaling. Moreover, L140 was critical for locking MC4R in inactive conformation and several mutants showed biased signaling in cAMP and ERK1/2 signaling pathways.
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Affiliation(s)
- Xiu-Lei Mo
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USA
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17
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Valentin-Hansen L, Holst B, Frimurer TM, Schwartz TW. PheVI:09 (Phe6.44) as a sliding microswitch in seven-transmembrane (7TM) G protein-coupled receptor activation. J Biol Chem 2012; 287:43516-26. [PMID: 23135271 DOI: 10.1074/jbc.m112.395137] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In seven-transmembrane (7TM), G protein-coupled receptors, highly conserved residues function as microswitches, which alternate between different conformations and interaction partners in an extended allosteric interface between the transmembrane segments performing the large scale conformational changes upon receptor activation. Computational analysis using x-ray structures of the β(2)-adrenergic receptor demonstrated that PheVI:09 (6.44), which in the inactive state is locked between the backbone and two hydrophobic residues in transmembrane (TM)-III, upon activation slides ∼2 Å toward TM-V into a tight pocket generated by five hydrophobic residues protruding from TM-III and TM-V. Of these, the residue in position III:16 (3.40) (often an Ile or Val) appears to function as a barrier or gate for the transition between inactive and active conformation. Mutational analysis showed that PheVI:09 is essential for the constitutive and/or agonist-induced signaling of the ghrelin receptor, GPR119, the β(2)-adrenergic receptor, and the neurokinin-1 receptor. Substitution of the residues constituting the hydrophobic pocket between TM-III and TM-V in the ghrelin receptor in four of five positions impaired receptor signaling. In GPR39, representing the 12% of 7TM receptors lacking an aromatic residue at position VI:09, unchanged agonist-induced signaling was observed upon Ala substitution of LeuVI:09 despite reduced cell surface expression of the mutant receptor. It is concluded that PheVI:09 constitutes an aromatic microswitch that stabilizes the active, outward tilted conformation of TM-VI relative to TM-III by sliding into a tight hydrophobic pocket between TM-III and TM-V and that the hydrophobic residue in position III:16 constitutes a gate for this transition.
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Affiliation(s)
- Louise Valentin-Hansen
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, the Panum Institute, Copenhagen, Denmark
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Ishii J, Moriguchi M, Hara KY, Shibasaki S, Fukuda H, Kondo A. Improved identification of agonist-mediated Gαi-specific human G-protein-coupled receptor signaling in yeast cells by flow cytometry. Anal Biochem 2012; 426:129-33. [DOI: 10.1016/j.ab.2012.04.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 04/03/2012] [Accepted: 04/05/2012] [Indexed: 11/26/2022]
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Wilkins AD, Bachman BJ, Erdin S, Lichtarge O. The use of evolutionary patterns in protein annotation. Curr Opin Struct Biol 2012; 22:316-25. [PMID: 22633559 DOI: 10.1016/j.sbi.2012.05.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 05/01/2012] [Indexed: 01/13/2023]
Abstract
With genomic data skyrocketing, their biological interpretation remains a serious challenge. Diverse computational methods address this problem by pointing to the existence of recurrent patterns among sequence, structure, and function. These patterns emerge naturally from evolutionary variation, natural selection, and divergence--the defining features of biological systems--and they identify molecular events and shapes that underlie specificity of function and allosteric communication. Here we review these methods, and the patterns they identify in case studies and in proteome-wide applications, to infer and rationally redesign function.
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Affiliation(s)
- Angela D Wilkins
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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Cell wall trapping of autocrine peptides for human G-protein-coupled receptors on the yeast cell surface. PLoS One 2012; 7:e37136. [PMID: 22623985 PMCID: PMC3356411 DOI: 10.1371/journal.pone.0037136] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 04/13/2012] [Indexed: 12/01/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) regulate a wide variety of physiological processes and are important pharmaceutical targets for drug discovery. Here, we describe a unique concept based on yeast cell-surface display technology to selectively track eligible peptides with agonistic activity for human GPCRs (Cell Wall Trapping of Autocrine Peptides (CWTrAP) strategy). In our strategy, individual recombinant yeast cells are able to report autocrine-positive activity for human GPCRs by expressing a candidate peptide fused to an anchoring motif. Following expression and activation, yeast cells trap autocrine peptides onto their cell walls. Because captured peptides are incapable of diffusion, they have no impact on surrounding yeast cells that express the target human GPCR and non-signaling peptides. Therefore, individual yeast cells can assemble the autonomous signaling complex and allow single-cell screening of a yeast population. Our strategy may be applied to identify eligible peptides with agonistic activity for target human GPCRs.
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Shenker A. Activating Mutations of the Lutropin Choriogonadotropin Receptor in Precocious Puberty. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820212138] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Three "hotspots" important for adenosine A(2B) receptor activation: a mutational analysis of transmembrane domains 4 and 5 and the second extracellular loop. Purinergic Signal 2011; 8:23-38. [PMID: 21818573 PMCID: PMC3286537 DOI: 10.1007/s11302-011-9251-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 07/14/2011] [Indexed: 01/13/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are a major drug target and can be activated by a range of stimuli, from photons to proteins. Despite the progress made in the last decade in molecular and structural biology, their exact activation mechanism is still unknown. Here we describe new insights in specific regions essential in adenosine A2B receptor activation (A2BR), a typical class A GPCR. We applied unbiased random mutagenesis on the middle part of the human adenosine A2BR, consisting of transmembrane domains 4 and 5 (TM4 and TM5) linked by extracellular loop 2 (EL2), and subsequently screened in a medium-throughput manner for gain-of-function and constitutively active mutants. For that purpose, we used a genetically engineered yeast strain (Saccharomyces cerevisiae MMY24) with growth as a read-out parameter. From the random mutagenesis screen, 12 different mutant receptors were identified that form three distinct clusters; at the top of TM4, in a cysteine-rich region in EL2, and at the intracellular side of TM5. All mutant receptors show a vast increase in agonist potency and most also displayed a significant increase in constitutive activity. None of these residues are supposedly involved in ligand binding directly. As a consequence, it appears that disrupting the relatively “silent” configuration of the wild-type receptor in each of the three clusters readily causes spontaneous receptor activity.
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Abstract
AbstractThe melanocortin 4 receptor (MC4R) is involved in the regulation of energy homeostasis and is known as one of the major hypothalamic regulators of food intake. Several studies have shown that replacement of aspartic acid at position 126 of the MC4R abolishes the ligand binding. We used the modified yeast Saccharomyces cerevisiae strain MMY28 to functionally express the MC4R and characterise the importance of this amino acid for ligand based activation of the receptor. The efficiency of the functional expression system was estimated by activation with αMSH, ACTH and THIQ and compared with cAMP response in mammalian cells. We generated the library of MC4R mutants randomised at the amino acid position 126. Recombinant MC4R clones were screened for the αMSH induced activity in yeast. From 9 different amino acids obtained only the natural aspartic acid displayed the ligand dependent activity of MC4R. The MC4R variants with glutamic acid and leucine at position 126, however, displayed higher background activity than other amino acid substitutions. The results suggest that the yeast expression system is suitable for screening of the MC4R receptor ligands and that the substitution of aspartic acid at position 126 of MC4R by different amino acids functionally inactivates the receptor.
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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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Abstract
The melanocortin-4 receptor (MC4R) was cloned in 1993 by degenerate PCR; however, its function was unknown. Subsequent studies suggest that the MC4R might be involved in regulating energy homeostasis. This hypothesis was confirmed in 1997 by a series of seminal studies in mice. In 1998, human genetic studies demonstrated that mutations in the MC4R gene can cause monogenic obesity. We now know that mutations in the MC4R are the most common monogenic form of obesity, with more than 150 distinct mutations reported thus far. This review will summarize the studies on the MC4R, from its cloning and tissue distribution to its physiological roles in regulating energy homeostasis, cachexia, cardiovascular function, glucose and lipid homeostasis, reproduction and sexual function, drug abuse, pain perception, brain inflammation, and anxiety. I will then review the studies on the pharmacology of the receptor, including ligand binding and receptor activation, signaling pathways, as well as its regulation. Finally, the pathophysiology of the MC4R in obesity pathogenesis will be reviewed. Functional studies of the mutant MC4Rs and the therapeutic implications, including small molecules in correcting binding and signaling defect, and their potential as pharmacological chaperones in rescuing intracellularly retained mutants, will be highlighted.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology, and Pharmacology, Auburn University, Alabama 36849-5519, USA.
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Bonde MM, Yao R, Ma JN, Madabushi S, Haunsø S, Burstein ES, Whistler JL, Sheikh SP, Lichtarge O, Hansen JL. An angiotensin II type 1 receptor activation switch patch revealed through evolutionary trace analysis. Biochem Pharmacol 2010; 80:86-94. [PMID: 20227396 DOI: 10.1016/j.bcp.2010.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/08/2010] [Accepted: 03/04/2010] [Indexed: 12/21/2022]
Abstract
Seven transmembrane (7TM) or G protein-coupled receptors constitute a large superfamily of cell surface receptors sharing a structural motif of seven transmembrane spanning alpha helices. Their activation mechanism most likely involves concerted movements of the transmembrane helices, but remains to be completely resolved. Evolutionary Trace (ET) analysis is a computational method, which identifies clusters of functionally important residues by integrating information on evolutionary important residue variations with receptor structure. Combined with known mutational data, ET predicted a patch of residues in the cytoplasmic parts of TM2, TM3, and TM6 to form an activation switch that is common to all family A 7TM receptors. We tested this hypothesis in the rat Angiotensin II (Ang II) type 1a (AT1a) receptor. The receptor has important roles in the cardiovascular system, but has also frequently been applied as a model for 7TM receptor activation and signaling. Six mutations: F66A, L67R, L70R, L119R, D125A, and I245F were targeted to the putative switch and assayed for changes in activation state by their ligand binding, signaling, and trafficking properties. All but one receptor mutant (that was not expressed well) displayed phenotypes associated with changed activation state, such as increased agonist affinity or basal activity, promiscuous activation, or constitutive internalization highlighting the importance of testing different signaling pathways. We conclude that this evolutionary important patch mediates interactions important for maintaining the inactive state. More broadly, these observations in the AT1 receptor are consistent with computational predictions of a generic role for this patch in 7TM receptor activation.
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Affiliation(s)
- Marie Mi Bonde
- Laboratory for Molecular Cardiology, The Danish National Research Foundation Centre for Cardiac Arrhythmia, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Juliane Mariesvej 20, section 9312, DK-2100 Copenhagen, Denmark
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Nikiforovich GV, Baranski TJ. Computational Modeling of Constitutively Active Mutants of GPCRs. Methods Enzymol 2010; 485:369-91. [DOI: 10.1016/b978-0-12-381296-4.00021-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Light activation of rhodopsin: insights from molecular dynamics simulations guided by solid-state NMR distance restraints. J Mol Biol 2009; 396:510-27. [PMID: 20004206 DOI: 10.1016/j.jmb.2009.12.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 10/09/2009] [Accepted: 12/02/2009] [Indexed: 11/20/2022]
Abstract
Structural restraints provided by solid-state NMR measurements of the metarhodopsin II intermediate are combined with molecular dynamics simulations to help visualize structural changes in the light activation of rhodopsin. Since the timescale for the formation of the metarhodopsin II intermediate (>1 ms) is beyond that readily accessible by molecular dynamics, we use NMR distance restraints derived from 13C dipolar recoupling measurements to guide the simulations. The simulations yield a working model for how photoisomerization of the 11-cis retinylidene chromophore bound within the interior of rhodopsin is coupled to transmembrane helix motion and receptor activation. The mechanism of activation that emerges is that multiple switches on the extracellular (or intradiscal) side of rhodopsin trigger structural changes that converge to disrupt the ionic lock between helices H3 and H6 on the intracellular side of the receptor.
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Klco JM, Sen S, Hansen JL, Lyngsø C, Nikiforovich GV, Sheikh SP, Baranski TJ. Complement factor 5a receptor chimeras reveal the importance of lipid-facing residues in transport competence. FEBS J 2009; 276:2786-800. [PMID: 19459935 DOI: 10.1111/j.1742-4658.2009.07002.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Residues that mediate helix-helix interactions within the seven transmembranes (TM) of G protein-coupled receptors are important for receptor biogenesis and the receptor switch mechanism. By contrast, the residues directly contacting the lipid bilayer have only recently garnered attention as potential receptor dimerization interfaces. In the present study, we aimed to determine the contributions of these lipid-facing residues to receptor function and oligomerization by systemically generating chimeric complement factor 5a receptors in which the entire lipid-exposed surface of a single TM helix was exchanged with the cognate residues from the angiotensin type 1 receptor. Disulfide-trapping and bioluminescence resonance energy transfer (BRET) studies demonstrated robust homodimerization of both complement factor 5a receptor and angiotensin type 1 receptor, but no evidence for heterodimerization. Despite relatively conservative substitutions, the lipid-facing chimeras (TM1, TM2, TM4, TM5, TM6 or TM7) were retained in the endoplasmic reticulum/cis-Golgi network. With the exception of the TM7 chimera that did not bind ligand, the lipid-facing chimeras bound ligand with low affinity, but similar to wild-type complement factor 5a receptors trapped in the endoplasmic reticulum with brefeldin A. These results suggest that the chimeric receptors were properly folded; moreover, native complement factor 5a receptors are not fully competent to bind ligand when present in the endoplasmic reticulum. BRET oligomerization studies demonstrated energy transfer between the wild-type complement factor 5a receptor and the lipid-facing chimeras, suggesting that the lipid-facing residues within a single TM segment are not essential for oligomerization. These studies highlight the importance of the lipid-facing residues in the complement factor 5a receptor for transport competence.
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Affiliation(s)
- Jeffery M Klco
- Department of Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
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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: 509] [Impact Index Per Article: 33.9] [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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Tao YX. Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. Pharmacol Ther 2008; 120:129-48. [PMID: 18768149 DOI: 10.1016/j.pharmthera.2008.07.005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 07/22/2008] [Indexed: 01/17/2023]
Abstract
The existence of constitutive activity for G protein-coupled receptors (GPCRs) was first described in 1980s. In 1991, the first naturally occurring constitutively active mutations in GPCRs that cause diseases were reported in rhodopsin. Since then, numerous constitutively active mutations that cause human diseases were reported in several additional receptors. More recently, loss of constitutive activity was postulated to also cause diseases. Animal models expressing some of these mutants confirmed the roles of these mutations in the pathogenesis of the diseases. Detailed functional studies of these naturally occurring mutations, combined with homology modeling using rhodopsin crystal structure as the template, lead to important insights into the mechanism of activation in the absence of crystal structure of GPCRs in active state. Search for inverse agonists on these receptors will be critical for correcting the diseases cause by activating mutations in GPCRs. Theoretically, these inverse agonists are better therapeutics than neutral antagonists in treating genetic diseases caused by constitutively activating mutations in GPCRs.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, 212 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
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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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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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Dirnberger D, Seuwen K. Signaling of human frizzled receptors to the mating pathway in yeast. PLoS One 2007; 2:e954. [PMID: 17895994 PMCID: PMC1978518 DOI: 10.1371/journal.pone.0000954] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Accepted: 09/08/2007] [Indexed: 11/18/2022] Open
Abstract
Frizzled receptors have seven membrane-spanning helices and are considered as atypical G protein-coupled receptors (GPCRs). The mating response of the yeast Saccharomyces cerevisiae is mediated by a GPCR signaling system and this model organism has been used extensively in the past to study mammalian GPCR function. We show here that human Frizzled receptors (Fz1 and Fz2) can be properly targeted to the yeast plasma membrane, and that they stimulate the yeast mating pathway in the absence of added Wnt ligands, as evidenced by cell cycle arrest in G1 and reporter gene expression dependent on the mating pathway-activated FUS1 gene. Introducing intracellular portions of Frizzled receptors into the Ste2p backbone resulted in the generation of constitutively active receptor chimeras that retained mating factor responsiveness. Introducing intracellular portions of Ste2p into the Frizzled receptor backbone was found to strongly enhance mating pathway activation as compared to the native Frizzleds, likely by facilitating interaction with the yeast Galpha protein Gpa1p. Furthermore, we show reversibility of the highly penetrant G1-phase arrests exerted by the receptor chimeras by deletion of the mating pathway effector FAR1. Our data demonstrate that Frizzled receptors can functionally replace mating factor receptors in yeast and offer an experimental system to study modulators of Frizzled receptors.
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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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37
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Hagemann IS, Narzinski KD, Baranski TJ. E2F8 is a nonreceptor activator of heterotrimeric G proteins. J Mol Signal 2007; 2:3. [PMID: 17394670 PMCID: PMC1852105 DOI: 10.1186/1750-2187-2-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 03/30/2007] [Indexed: 01/22/2023] Open
Abstract
Background Heterotrimeric G proteins are important for numerous signaling events in eukaryotes, serving primarily to transduce signals that are initiated by G protein-coupled receptors. It has recently become clear that nonreceptor activators can regulate the level of heterotrimeric G protein signaling and, in some cases, drive cycles of receptor-independent G protein activation. In this study, we used a yeast expression cloning strategy to identify novel nonreceptor activators of heterotrimeric G proteins in a human adipocyte cDNA library. Results The human transcription factor E2F8 was found to activate heterotrimeric G proteins, suggesting a specific biological role for this recently described member of the E2F family. Epistasis studies showed that E2F8 acted at the level of G proteins and was specific for Gαi over Gpa1. E2F8 augmented receptor-driven signaling, but also activated G proteins in the absence of a receptor. The GTPase-activating protein RGS4 antagonized the effect of E2F8, showing that E2F8's effect on Gα involved nucleotide turnover. The entire E2F8 protein was required for full activity, but the majority of the signaling activity appeared to reside in the first 200 residues. Conclusion In yeast, E2F8 is a guanine nucleotide exchange factor (GEF) for the α subunit of heterotrimeric G proteins. The molecular mechanism and biological significance of this effect remain to be determined.
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Affiliation(s)
- Ian S Hagemann
- Departments of Medicine and of Molecular Biology & Pharmacology, 660 S. Euclid Ave., Campus Box 8127, St. Louis, Missouri 63110, USA
| | - Kirk D Narzinski
- Departments of Medicine and of Molecular Biology & Pharmacology, 660 S. Euclid Ave., Campus Box 8127, St. Louis, Missouri 63110, USA
| | - Thomas J Baranski
- Departments of Medicine and of Molecular Biology & Pharmacology, 660 S. Euclid Ave., Campus Box 8127, St. Louis, Missouri 63110, USA
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Isin B, Rader AJ, Dhiman HK, Klein-Seetharaman J, Bahar I. Predisposition of the dark state of rhodopsin to functional changes in structure. Proteins 2007; 65:970-83. [PMID: 17009319 DOI: 10.1002/prot.21158] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
As the only member of the family of G-protein-coupled receptors for which atomic coordinates are available, rhodopsin is widely studied for insight into the molecular mechanism of G-protein-coupled receptor activation. The currently available structures refer to the inactive, dark state, of rhodopsin, rather than the light-activated metarhodopsin II (Meta II) state. A model for the Meta II state is proposed here by analyzing elastic network normal modes in conjunction with experimental data. Key mechanical features and interactions broken/formed in the proposed model are found to be consistent with the experimental data. The model is further tested by using a set of Meta II fluorescence decay rates measured to empirically characterize the deactivation of rhodopsin mutants. The model is found to correctly predict 93% of the experimentally observed effects in 119 rhodopsin mutants for which the decay rates and misfolding data have been measured, including a systematic analysis of Cys-->Ser replacements reported here. Based on the detailed comparison between model and experiments, a cooperative activation mechanism is deduced that couples retinal isomerization to concerted changes in conformation, facilitated by the intrinsic dynamics of rhodopsin. A global hinge site is identified near the retinal-binding pocket that ensures the efficient propagation of signals from the central transmembrane region to both cytoplasmic and extracellular ends. The predicted activation mechanism opens the transmembrane helices at the critical G-protein binding cytoplasmic domain. This model provides a detailed, mechanistic description of the activation process, extending experimental observations and yielding new insights for further tests.
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Affiliation(s)
- Basak Isin
- Department of Computational Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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39
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Hauser M, Kauffman S, Lee BK, Naider F, Becker JM. The first extracellular loop of the Saccharomyces cerevisiae G protein-coupled receptor Ste2p undergoes a conformational change upon ligand binding. J Biol Chem 2007; 282:10387-97. [PMID: 17293349 DOI: 10.1074/jbc.m608903200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In this study of the Saccharomyces cerevisiae G protein-coupled receptor Ste2p, we present data indicating that the first extracellular loop (EL1) of the alpha-factor receptor has tertiary structure that limits solvent accessibility and that its conformation changes in a ligand-dependent manner. The substituted cysteine accessibility method was used to probe the solvent exposure of single cysteine residues engineered to replace residues Tyr(101) through Gln(135) of EL1 in the presence and absence of the tridecapeptide alpha-factor and a receptor antagonist. Surprisingly, many residues, especially those at the N-terminal region, were not solvent-accessible, including residues of the binding-competent yet signal transduction-deficient mutants L102C, N105C, S108C, Y111C, and T114C. In striking contrast, two N-terminal residues, Y101C and Y106C, were readily solvent-accessible, but upon incubation with alpha-factor labeling was reduced, suggesting a pheromone-dependent conformational change limiting solvent accessibility had occurred. Labeling in the presence of the antagonist, which binds Ste2p but does not initiate signal transduction, did not significantly alter reactivity with the Y101C and Y106C receptors, suggesting that the alpha-factor-dependent decrease in solvent accessibility was not because of steric hindrance that prevented the labeling reagent access to these residues. Based on these and previous observations, we propose a model in which the N terminus of EL1 is structured such that parts of the loop are buried in a solvent-inaccessible environment interacting with the extracellular part of the transmembrane domain bundle. This study highlights the essential role of an extracellular loop in activation of a G protein-coupled receptor upon ligand binding.
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Affiliation(s)
- Melinda Hauser
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, USA
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40
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Smit MJ, Vischer HF, Bakker RA, Jongejan A, Timmerman H, Pardo L, Leurs R. Pharmacogenomic and Structural Analysis of Constitutive G Protein–Coupled Receptor Activity. Annu Rev Pharmacol Toxicol 2007; 47:53-87. [PMID: 17029567 DOI: 10.1146/annurev.pharmtox.47.120505.105126] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
G protein-coupled receptors (GPCRs) respond to a chemically diverse plethora of signal transduction molecules. The notion that GPCRs also signal without an external chemical trigger, i.e., in a constitutive or spontaneous manner, resulted in a paradigm shift in the field of GPCR pharmacology. The discovery of constitutive GPCR activity and the fact that GPCR binding and signaling can be strongly affected by a single point mutation drew attention to the evolving area of GPCR pharmacogenomics. For a variety of GPCRs, point mutations have been convincingly linked to human disease. Mutations within conserved motifs, known to be involved in GPCR activation, might explain the properties of some naturally occurring, constitutively active GPCR variants linked to disease. In this review, we provide a brief historical introduction to the concept of constitutive receptor activity and the pharmacogenomic and structural aspects of constitutive receptor activity.
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Affiliation(s)
- Martine J Smit
- Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Vrije Universiteit, Faculty of Sciences, Department of Chemistry, 1081 HV Amsterdam, The Netherlands.
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41
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Matsumoto ML, Narzinski K, Nikiforovich GV, Baranski TJ. A Comprehensive Structure-Function Map of the Intracellular Surface of the Human C5a Receptor. J Biol Chem 2007; 282:3122-33. [PMID: 17090530 DOI: 10.1074/jbc.m607683200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Within any given cell many G protein-coupled receptors are expressed in the presence of multiple G proteins, yet most receptors couple to a specific subset of G proteins to elicit their programmed response. Numerous studies demonstrate that the carboxyl-terminal five amino acids of the Galpha subunits are a major determinant of specificity, however the receptor determinants of specificity are less clear. We have used a collection of 133 functional mutants of the C5a receptor obtained in a mutagenesis screen targeting the intracellular loops and the carboxyl terminus (Matsumoto, M. L., Narzinski, K., Kiser, P. D., Nikiforovich, G. V., and Baranski, T. J. (2007) J. Biol. Chem. 282, 3105-3121) to investigate how specificity is encoded. Each mutant, originally selected for its ability to signal through a nearly full-length Galpha(i) in yeast, was tested to see whether it could activate three versions of chimeric Galpha subunits consisting of Gpa1 fused to the carboxyl-terminal five amino acids of Galpha(i), Galpha(q), or Galpha(s) in yeast. Surprisingly the carboxyl-terminal tail of the C5a receptor is the most important specificity determinant in that nearly all mutants in this region showed a gain in coupling to Galpha(q) and/or Galpha(s). More than half of the receptors mutated in the second intracellular loop also demonstrated broadened G protein coupling. Given a lack of selective advantage for this broadened signaling in the initial screen, we propose a model in which the carboxyl-terminal tail acts together with the intracellular loops to generate a specificity filter for receptor-G protein interactions that functions primarily to restrict access of incorrect G proteins to the receptor.
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Affiliation(s)
- Marissa L Matsumoto
- Department of Medicine and Molecular Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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42
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Scarselli M, Li B, Kim SK, Wess J. Multiple residues in the second extracellular loop are critical for M3 muscarinic acetylcholine receptor activation. J Biol Chem 2007; 282:7385-96. [PMID: 17213190 DOI: 10.1074/jbc.m610394200] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent studies suggest that the second extracellular loop (o2 loop) of bovine rhodopsin and other class I G protein-coupled receptors (GPCRs) targeted by biogenic amine ligands folds deeply into the transmembrane receptor core where the binding of cis-retinal and biogenic amine ligands is known to occur. In the past, the potential role of the o2 loop in agonist-dependent activation of biogenic amine GPCRs has not been studied systematically. To address this issue, we used the M(3) muscarinic acetylcholine receptor (M3R), a prototypic class I GPCR, as a model system. Specifically, we subjected the o2 loop of the M3R to random mutagenesis and subsequently applied a novel yeast genetic screen to identity single amino acid substitutions that interfered with M3R function. This screen led to the recovery of about 20 mutant M3Rs containing single amino acid changes in the o2 loop that were inactive in yeast. In contrast, application of the same strategy to the extracellular N-terminal domain of the M3R did not yield any single point mutations that disrupted M3R function. Pharmacological characterization of many of the recovered mutant M3Rs in mammalian cells, complemented by site-directed mutagenesis studies, indicated that the presence of several o2 loop residues is important for efficient agonist-induced M3R activation. Besides the highly conserved Cys(220) residue, Gln(207), Gly(211), Arg(213), Gly(218), Ile(222), Phe(224), Leu(225), and Pro(228) were found to be of particular functional importance. In general, mutational modification of these residues had little effect on agonist binding affinities. Our findings are therefore consistent with a model in which multiple o2 loop residues are involved in stabilizing the active state of the M3R. Given the high degree of structural homology found among all biogenic amine GPCRs, our findings should be of considerable general relevance.
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Affiliation(s)
- Marco Scarselli
- Molecular Signaling , Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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43
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Li B, Scarselli M, Knudsen CD, Kim SK, Jacobson KA, McMillin SM, Wess J. Rapid identification of functionally critical amino acids in a G protein-coupled receptor. Nat Methods 2007; 4:169-74. [PMID: 17206152 DOI: 10.1038/nmeth990] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Accepted: 11/02/2006] [Indexed: 11/09/2022]
Abstract
G protein-coupled receptors (GPCRs) comprise one of the largest protein families found in nature. Here we describe a new experimental strategy that allows rapid identification of functionally critical amino acids in the rat M(3) muscarinic acetylcholine receptor (M3R), a prototypic class I GPCR. This approach involves low-frequency random mutagenesis of the entire M3R coding sequence, followed by the application of a new yeast genetic screen that allows the recovery of inactivating M3R single point mutations. The vast majority of recovered mutant M3Rs also showed substantial functional impairments in transfected mammalian (COS-7) cells. A subset of mutant receptors, however, behaved differently in yeast and mammalian cells, probably because of the specific features of the yeast expression system used. The screening strategy described here should be applicable to all GPCRs that can be expressed functionally in yeast.
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Affiliation(s)
- Bo Li
- Molecular Signaling, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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44
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Matsumoto ML, Narzinski K, Kiser PD, Nikiforovich GV, Baranski TJ. A comprehensive structure-function map of the intracellular surface of the human C5a receptor. I. Identification of critical residues. J Biol Chem 2006; 282:3105-21. [PMID: 17135254 DOI: 10.1074/jbc.m607679200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors are one of the largest protein families in nature; however, the mechanisms by which they activate G proteins are still poorly understood. To identify residues on the intracellular face of the human C5a receptor that are involved in G protein activation, we performed a genetic analysis of each of the three intracellular loops and the carboxyl-terminal tail of the receptor. Amino acid substitutions were randomly incorporated into each loop, and functional receptors were identified in yeast. The third intracellular loop contains the largest number of preserved residues (positions resistant to amino acid substitutions), followed by the second loop, the first loop, and lastly the carboxyl terminus. Surprisingly, complete removal of the carboxyl-terminal tail did not impair C5a receptor signaling. When mapped onto a three-dimensional structural model of the inactive state of the C5a receptor, the preserved residues reside on one half of the intracellular surface of the receptor, creating a potential activation face. Together these data provide one of the most comprehensive functional maps of the intracellular surface of any G protein-coupled receptor to date.
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Affiliation(s)
- Marissa L Matsumoto
- Department of Medicine and Molecular Biology, Washington School of Medicine, Missouri 63110, USA
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45
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Hagemann IS, Narzinski KD, Floyd DH, Baranski TJ. Random mutagenesis of the complement factor 5a (C5a) receptor N terminus provides a structural constraint for C5a docking. J Biol Chem 2006; 281:36783-92. [PMID: 17023413 DOI: 10.1074/jbc.m607686200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The N terminus of G protein-coupled receptors has been implicated in binding to peptide hormones. We have used random saturation mutagenesis to identify essential residues in the N terminus of the human complement factor 5a receptor (C5aR). In a library of N-terminal mutant C5aR molecules screened for activation by C5a, residues 24-30 of the C5aR showed a marked propensity to mutate to cysteine, most likely indicating that sulfhydryl groups at these positions are appropriately situated to form disulfide interactions with the unpaired Cys(27) of human C5a. This presumptive spatial constraint allowed the ligand to be computationally docked to the receptor to form a model of the C5a/C5aR interaction. When the N-terminal mutant C5aR library was rescreened with C5a C27R, a ligand incapable of disulfide interactions, no individual position in the N terminus was essential for receptor signaling. However, the region 19-29 was relatively highly conserved in the functional mutants, further demonstrating that this region of the C5aR makes a productive physiologic interaction with the C5a ligand.
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Affiliation(s)
- Ian S Hagemann
- Departments of Medicine and Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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46
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Hagemann IS, Nikiforovich GV, Baranski TJ. Comparison of the retinitis pigmentosa mutations in rhodopsin with a functional map of the C5a receptor. Vision Res 2006; 46:4519-31. [PMID: 16962629 DOI: 10.1016/j.visres.2006.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Revised: 07/14/2006] [Accepted: 07/19/2006] [Indexed: 10/24/2022]
Abstract
We compare the known retinitis pigmentosa (RP) mutations in rhodopsin with mutational data obtained for the complement factor 5a receptor (C5aR), a member of the rhodopsin-like family of G protein-coupled receptors (GPCRs). We have performed genetic analyses that define residues that are required for C5aR folding and function. The cognate residues in rhodopsin are not preferentially mutated in RP, suggesting that the predominant molecular defect in RP involves more than simple misfolding or inactivation. Energy calculations are performed to elucidate the structural effects of the RP mutations. Many of these mutations specifically disrupt the environment of the retinal prosthetic group of rhodopsin, and these do not correspond to essential residues in C5aR. This may be because a retinal group is present in rhodopsin but not in C5aR. Another subset of RP mutations is more generally important for receptor structure, and these mutations correlate with essential residues of C5aR.
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Affiliation(s)
- Ian S Hagemann
- Department of Medicine, Washington University in St. Louis, Campus Box 8127, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
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47
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D’Antona AM, Ahn KH, Wang L, Mierke DF, Lucas-Lenard J, Kendall DA. A cannabinoid receptor 1 mutation proximal to the DRY motif results in constitutive activity and reveals intramolecular interactions involved in receptor activation. Brain Res 2006; 1108:1-11. [PMID: 16879811 PMCID: PMC2733829 DOI: 10.1016/j.brainres.2006.05.042] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Revised: 05/04/2006] [Accepted: 05/06/2006] [Indexed: 11/25/2022]
Abstract
Activation of a G-protein-coupled receptor involves changes in specific microdomain interactions within the transmembrane region of the receptor. Here, we have focused on the role of L207, proximal to the DRY motif of the human cannabinoid receptor 1 in the interconversion of the receptor resting and active states. Ligand binding analysis of the mutant receptor L207A revealed an enhanced affinity for agonists (three- to six-fold) and a diminished affinity for inverse agonists (19- to 35-fold) compared to the wild-type receptor, properties characteristic of constitutive activity. To further examine whether this mutant adopts a ligand-independent, active form, treatment with GTPgammaS was used to inhibit G protein coupling. Under these conditions, the L207A receptor exhibited a 10-fold increase in affinity for the inverse agonist SR141716A, consistent with a shift away from an enhanced precoupled state. Analysis of the cellular activity of the L207A receptor showed elevated basal cyclic AMP accumulation relative to the wild type that is inhibited by SR141716A, consistent with receptor-mediated Gs precoupling. Using toxins to selectively abrogate Gs or Gi coupling, we found that CP55940 nonetheless induced only a Gi response suggesting a strong preference of this ligand-bound form for Gi in this system. Molecular dynamics simulations reveal that the single residue change of L207A impacts the association of TM3 and TM6 in the receptor by altering hydrophobic interactions involving L207, the salt bridge involving the Arg of the DRY motif, and the helical structure of TM6, consistent with events leading to activation. The structural alterations parallel those observed in models of a mutant CB(1) receptor T210I, with established constitutive activity (D'Antona, A.M., Ahn, K.H. and Kendall, D.A., 2006. Mutations of CB1 T210 produce active and inactive receptor forms: correlations with ligand affinity, receptor stability, and cellular localization. Biochemistry, 45, 5606-5617).
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Affiliation(s)
- Aaron M. D’Antona
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Kwang H. Ahn
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Lei Wang
- Department of Chemistry and Department of Molecular Pharmacology, Brown University, Providence, RI 02912, USA
| | - Dale F. Mierke
- Department of Chemistry and Department of Molecular Pharmacology, Brown University, Providence, RI 02912, USA
| | - Jean Lucas-Lenard
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Debra A. Kendall
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
- Corresponding author. E-mail address: (D.A. Kendall)
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48
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Urban JD, Clarke WP, von Zastrow M, Nichols DE, Kobilka B, Weinstein H, Javitch JA, Roth BL, Christopoulos A, Sexton PM, Miller KJ, Spedding M, Mailman RB. Functional selectivity and classical concepts of quantitative pharmacology. J Pharmacol Exp Ther 2006; 320:1-13. [PMID: 16803859 DOI: 10.1124/jpet.106.104463] [Citation(s) in RCA: 840] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The concept of intrinsic efficacy has been enshrined in pharmacology for half of a century, yet recent data have revealed that many ligands can differentially activate signaling pathways mediated via a single G protein-coupled receptor in a manner that challenges the traditional definition of intrinsic efficacy. Some terms for this phenomenon include functional selectivity, agonist-directed trafficking, and biased agonism. At the extreme, functionally selective ligands may be both agonists and antagonists at different functions mediated by the same receptor. Data illustrating this phenomenon are presented from serotonin, opioid, dopamine, vasopressin, and adrenergic receptor systems. A variety of mechanisms may influence this apparently ubiquitous phenomenon. It may be initiated by differences in ligand-induced intermediate conformational states, as shown for the beta(2)-adrenergic receptor. Subsequent mechanisms that may play a role include diversity of G proteins, scaffolding and signaling partners, and receptor oligomers. Clearly, expanded research is needed to elucidate the proximal (e.g., how functionally selective ligands cause conformational changes that initiate differential signaling), intermediate (mechanisms that translate conformation changes into differential signaling), and distal mechanisms (differential effects on target tissue or organism). Besides the heuristically interesting nature of functional selectivity, there is a clear impact on drug discovery, because this mechanism raises the possibility of selecting or designing novel ligands that differentially activate only a subset of functions of a single receptor, thereby optimizing therapeutic action. It also may be timely to revise classic concepts in quantitative pharmacology and relevant pharmacological conventions to incorporate these new concepts.
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MESH Headings
- Animals
- Humans
- Ligands
- Protein Conformation
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/physiology
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/physiology
- Receptors, Dopamine D1/chemistry
- Receptors, Dopamine D1/drug effects
- Receptors, Dopamine D1/physiology
- Receptors, Dopamine D2/chemistry
- Receptors, Dopamine D2/drug effects
- Receptors, Dopamine D2/physiology
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/physiology
- Receptors, Opioid, mu/chemistry
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/physiology
- Receptors, Vasopressin/chemistry
- Receptors, Vasopressin/drug effects
- Receptors, Vasopressin/physiology
- Signal Transduction
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Affiliation(s)
- Jonathan D Urban
- Curriculum in Toxicology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7160, USA
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49
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Spalding TA, Burstein ES. Constitutive activity of muscarinic acetylcholine receptors. J Recept Signal Transduct Res 2006; 26:61-85. [PMID: 16595339 DOI: 10.1080/10799890600567349] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We review the literature describing constitutive activity of the five muscarinic acetylcholine receptors in native and recombinant systems and discuss the effect of constitutive activity on muscarinic pharmacology in the context of modern models of receptor activation. We include a summary of mutations found to cause constitutive activity and discuss the implications of these data for the structure, function, and activation mechanism of muscarinic receptors. Finally, we discuss the possible physiological significance of constitutive activity of muscarinic receptors, incorporating information provided by targeted deletion of each of the muscarinic subtypes.
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Affiliation(s)
- Tracy A Spalding
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA.
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50
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Ringkananont U, Van Durme J, Montanelli L, Ugrasbul F, Yu YM, Weiss RE, Refetoff S, Grasberger H. Repulsive Separation of the Cytoplasmic Ends of Transmembrane Helices 3 and 6 Is Linked to Receptor Activation in a Novel Thyrotropin Receptor Mutant (M626I). Mol Endocrinol 2006; 20:893-903. [PMID: 16339276 DOI: 10.1210/me.2005-0339] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AbstractLigand-dependent activation of G protein-coupled receptors (GPCRs) involves repositioning of the juxtacytoplasmic ends of transmembrane helices TM3 and TM6. This concept, inferred from site-directed spin labeling studies, is supported by chemical cross-linking of the cytoplasmic ends of TM3 and TM6 blocking GPCR activation. Here we report a novel constitutive active mutation (M626I) in TM6 of the TSH receptor (TSHR), identified in affected members of a family with nonautoimmune hyperthyroidism. The specific constitutive activity of M626I, measured by its basal cAMP generation corrected for cell surface expression, was 13-fold higher than that of wild-type TSHR. Homology modeling of the TSHR serpentine domain based on the rhodopsin crystal structure suggests that M626 faces the side chain of I515 of TM3 near the membrane-cytoplasmic junction. Steric hindrance of the introduced isoleucine by I515 is consistent with the fact that shorter or more flexible side chains at position 626 did not increase constitutivity. Furthermore, a reciprocal mutation at position 515 (I515M), when introduced into the M626I background, acts as revertant mutation by allowing accommodation of the isoleucine sidechain at position 626 and fully restoring the constitutive activity to the level of wild-type TSHR. Thus, repulsive separation of the juxtacytoplasmic TM6 and TM3 in the M626I model conclusively demonstrates a direct link between the opening of this cytoplasmic face of the receptor structure and G protein coupling.
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Affiliation(s)
- Usanee Ringkananont
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
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