1
|
Fredgart MH, Leurgans TM, Stenelo M, Nybo M, Bloksgaard M, Lindblad L, De Mey JGR, Steckelings UM. The angiotensin AT 2-receptor agonist compound 21 is an antagonist for the thromboxane TP-receptor - Implications for preclinical studies and future clinical use. Peptides 2023; 164:170990. [PMID: 36894067 DOI: 10.1016/j.peptides.2023.170990] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/03/2023] [Accepted: 03/06/2023] [Indexed: 03/09/2023]
Abstract
Since the AT2-receptor (AT2R) agonist C21 has structural similarity to the AT1-receptor antagonists Irbesartan and Losartan, which are antagonists not only at the AT1R, but also at thromboxane TP-receptors, we tested the hypothesis that C21 has TP-receptor antagonistic properties as well. Isolated mouse mesenteric arteries from C57BL/6 J and AT2R-knockout mice (AT2R-/y) were mounted in wire myographs, contracted with either phenylephrine or the thromboxane A2 (TXA2) analogue U46619, and the relaxing effect of C21 (0.1 nM - 10 µM) was investigated. The effect of C21 on U46619-induced platelet aggregation was measured by an impedance aggregometer. Direct interaction of C21 with TP-receptors was determined by an β-arrestin biosensor assay. C21 caused significant, concentration-dependent relaxations in phenylephrine- and U46619-contracted mesenteric arteries from C57BL/6 J mice. The relaxing effect of C21 was absent in phenylephrine-contracted arteries from AT2R-/y mice, whereas it was unchanged in U46619-contracted arteries from AT2R-/y mice. C21 inhibited U46619-stimulated aggregation of human platelets, which was not inhibited by the AT2R-antagonist PD123319. C21 reduced U46619-induced recruitment of β-arrestin to human thromboxane TP-receptors with a calculated Ki of 3.74 µM. We conclude that in addition to AT2R-agonistic properties, C21 also acts as low-affinity TP-receptor antagonist, and that - depending on the constrictor - both mechanisms can be responsible for C21-induced vasorelaxation. Furthermore, by acting as a TP-receptor antagonist, C21 inhibits platelet aggregation. These findings are important for understanding potential off-target effects of C21 in the preclinical and clinical context and for the interpretation of C21-related myography data in assays with TXA2-analogues as constrictor.
Collapse
Affiliation(s)
- Maise H Fredgart
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Thomas M Leurgans
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Martin Stenelo
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Mads Nybo
- Dept. of Clinical Biochemistry, Odense University Hospital, Odense, Denmark
| | - Maria Bloksgaard
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | | | - Jo G R De Mey
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - U Muscha Steckelings
- Institute of Molecular Medicine - Dept. of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark.
| |
Collapse
|
2
|
mtIF3 is locally translated in axons and regulates mitochondrial translation for axonal growth. BMC Biol 2022; 20:12. [PMID: 34996455 PMCID: PMC8742369 DOI: 10.1186/s12915-021-01215-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 11/09/2021] [Indexed: 11/13/2022] Open
Abstract
Background The establishment and maintenance of functional neural connections relies on appropriate distribution and localization of mitochondria in neurites, as these organelles provide essential energy and metabolites. In particular, mitochondria are transported to axons and support local energy production to maintain energy-demanding neuronal processes including axon branching, growth, and regeneration. Additionally, local protein synthesis is required for structural and functional changes in axons, with nuclear-encoded mitochondrial mRNAs having been found localized in axons. However, it remains unclear whether these mRNAs are locally translated and whether the potential translated mitochondrial proteins are involved in the regulation of mitochondrial functions in axons. Here, we aim to further understand the purpose of such compartmentalization by focusing on the role of mitochondrial initiation factor 3 (mtIF3), whose nuclear-encoded transcripts have been shown to be present in axonal growth cones. Results We demonstrate that brain-derived neurotrophic factor (BDNF) induces local translation of mtIF3 mRNA in axonal growth cones. Subsequently, mtIF3 protein is translocated into axonal mitochondria and promotes mitochondrial translation as assessed by our newly developed bimolecular fluorescence complementation sensor for the assembly of mitochondrial ribosomes. We further show that BDNF-induced axonal growth requires mtIF3-dependent mitochondrial translation in distal axons. Conclusion We describe a previously unknown function of mitochondrial initiation factor 3 (mtIF3) in axonal protein synthesis and development. These findings provide insight into the way neurons adaptively control mitochondrial physiology and axonal development via local mtIF3 translation. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01215-w.
Collapse
|
3
|
Aydin Y, Coin I. Biochemical insights into structure and function of arrestins. FEBS J 2021; 288:2529-2549. [DOI: 10.1111/febs.15811] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/26/2021] [Accepted: 03/09/2021] [Indexed: 12/13/2022]
Affiliation(s)
- Yasmin Aydin
- Institute of Biochemistry Faculty of Life Sciences University of Leipzig Germany
| | - Irene Coin
- Institute of Biochemistry Faculty of Life Sciences University of Leipzig Germany
| |
Collapse
|
4
|
A localized adaptor protein performs distinct functions at the Caulobacter cell poles. Proc Natl Acad Sci U S A 2021; 118:2024705118. [PMID: 33753507 PMCID: PMC8020655 DOI: 10.1073/pnas.2024705118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Asymmetric cell division yields two distinct daughter cells by mechanisms that underlie stem cell behavior and cellular diversity in all organisms. The bacterium Caulobacter crescentus is able to orchestrate this complex process with less than 4,000 genes. This article describes a strategy deployed by Caulobacter where a regulatory protein, PopA, is programed to perform distinct roles based on its subcellular address. We demonstrate that, depending on the availability of a second messenger molecule, PopA adopts either a monomer or dimer form. The two oligomeric forms interact with different partners at the two cell poles, playing a critical role in the degradation of a master transcription factor at one pole and flagellar assembly at the other pole. Asymmetric cell division generates two daughter cells with distinct characteristics and fates. Positioning different regulatory and signaling proteins at the opposing ends of the predivisional cell produces molecularly distinct daughter cells. Here, we report a strategy deployed by the asymmetrically dividing bacterium Caulobacter crescentus where a regulatory protein is programmed to perform distinct functions at the opposing cell poles. We find that the CtrA proteolysis adaptor protein PopA assumes distinct oligomeric states at the two cell poles through asymmetrically distributed c-di-GMP: dimeric at the stalked pole and monomeric at the swarmer pole. Different polar organizing proteins at each cell pole recruit PopA where it interacts with and mediates the function of two molecular machines: the ClpXP degradation machinery at the stalked pole and the flagellar basal body at the swarmer pole. We discovered a binding partner of PopA at the swarmer cell pole that together with PopA regulates the length of the flagella filament. Our work demonstrates how a second messenger provides spatiotemporal cues to change the physical behavior of an effector protein, thereby facilitating asymmetry.
Collapse
|
5
|
Stoddart LA, Kilpatrick LE, Corriden R, Kellam B, Briddon SJ, Hill SJ. Efficient G protein coupling is not required for agonist-mediated internalization and membrane reorganization of the adenosine A 3 receptor. FASEB J 2021; 35:e21211. [PMID: 33710641 PMCID: PMC9328438 DOI: 10.1096/fj.202001729rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 11/03/2020] [Accepted: 11/09/2020] [Indexed: 01/09/2023]
Abstract
Organization of G protein‐coupled receptors at the plasma membrane has been the focus of much recent attention. Advanced microscopy techniques have shown that these receptors can be localized to discrete microdomains and reorganization upon ligand activation is crucial in orchestrating their signaling. Here, we have compared the membrane organization and downstream signaling of a mutant (R108A, R3.50A) of the adenosine A3 receptor (A3AR) to that of the wild‐type receptor. Fluorescence Correlation Spectroscopy (FCS) studies with a fluorescent agonist (ABEA‐X‐BY630) demonstrated that both wild‐type and mutant receptors bind agonist with high affinity but in subsequent downstream signaling assays the R108A mutation abolished agonist‐mediated inhibition of cAMP production and ERK phosphorylation. In further FCS studies, both A3AR and A3AR R108A underwent similar agonist‐induced increases in receptor density and molecular brightness which were accompanied by a decrease in membrane diffusion after agonist treatment. Using bimolecular fluorescence complementation, experiments showed that the R108A mutant retained the ability to recruit β‐arrestin and these receptor/arrestin complexes displayed similar membrane diffusion and organization to that observed with wild‐type receptors. These data demonstrate that effective G protein signaling is not a prerequisite for agonist‐stimulated β‐arrestin recruitment and membrane reorganization of the A3AR.
Collapse
Affiliation(s)
- Leigh A Stoddart
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Laura E Kilpatrick
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK.,School of Pharmacy, Biodiscovery Institute, University Park Nottingham, Nottingham, UK
| | - Ross Corriden
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Barrie Kellam
- Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK.,School of Pharmacy, Biodiscovery Institute, University Park Nottingham, Nottingham, UK
| | - Stephen J Briddon
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Stephen J Hill
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| |
Collapse
|
6
|
Beaulieu ME, Castillo F, Soucek L. Structural and Biophysical Insights into the Function of the Intrinsically Disordered Myc Oncoprotein. Cells 2020; 9:E1038. [PMID: 32331235 PMCID: PMC7226237 DOI: 10.3390/cells9041038] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/16/2020] [Accepted: 04/17/2020] [Indexed: 12/13/2022] Open
Abstract
Myc is a transcription factor driving growth and proliferation of cells and involved in the majority of human tumors. Despite a huge body of literature on this critical oncogene, our understanding of the exact molecular determinants and mechanisms that underlie its function is still surprisingly limited. Indubitably though, its crucial and non-redundant role in cancer biology makes it an attractive target. However, achieving successful clinical Myc inhibition has proven challenging so far, as this nuclear protein is an intrinsically disordered polypeptide devoid of any classical ligand binding pockets. Indeed, Myc only adopts a (partially) folded structure in some contexts and upon interacting with some protein partners, for instance when dimerizing with MAX to bind DNA. Here, we review the cumulative knowledge on Myc structure and biophysics and discuss the implications for its biological function and the development of improved Myc inhibitors. We focus this biophysical walkthrough mainly on the basic region helix-loop-helix leucine zipper motif (bHLHLZ), as it has been the principal target for inhibitory approaches so far.
Collapse
Affiliation(s)
| | | | - Laura Soucek
- Peptomyc S.L., Edifici Cellex, 08035 Barcelona, Spain; (F.C.); (L.S.)
- Vall d’Hebron Institute of Oncology (VHIO), Edifici Cellex, 08035 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08035 Barcelona, Spain
- Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, 08035 Bellaterra, Spain
| |
Collapse
|
7
|
Köfalvi A, Moreno E, Cordomí A, Cai NS, Fernández-Dueñas V, Ferreira SG, Guixà-González R, Sánchez-Soto M, Yano H, Casadó-Anguera V, Cunha RA, Sebastião AM, Ciruela F, Pardo L, Casadó V, Ferré S. Control of glutamate release by complexes of adenosine and cannabinoid receptors. BMC Biol 2020; 18:9. [PMID: 31973708 PMCID: PMC6979073 DOI: 10.1186/s12915-020-0739-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 01/13/2020] [Indexed: 12/20/2022] Open
Abstract
Background It has been hypothesized that heteromers of adenosine A2A receptors (A2AR) and cannabinoid CB1 receptors (CB1R) localized in glutamatergic nerve terminals mediate the integration of adenosine and endocannabinoid signaling involved in the modulation of striatal excitatory neurotransmission. Previous studies have demonstrated the existence of A2AR-CB1R heteromers in artificial cell systems. A dependence of A2AR signaling for the Gi protein-mediated CB1R signaling was described as one of its main biochemical characteristics. However, recent studies have questioned the localization of functionally significant A2AR-CB1R heteromers in striatal glutamatergic terminals. Results Using a peptide-interfering approach combined with biophysical and biochemical techniques in mammalian transfected cells and computational modeling, we could establish a tetrameric quaternary structure of the A2AR-CB1R heterotetramer. This quaternary structure was different to the also tetrameric structure of heteromers of A2AR with adenosine A1 receptors or dopamine D2 receptors, with different heteromeric or homomeric interfaces. The specific quaternary structure of the A2A-CB1R, which depended on intermolecular interactions involving the long C-terminus of the A2AR, determined a significant A2AR and Gs protein-mediated constitutive activation of adenylyl cyclase. Using heteromer-interfering peptides in experiments with striatal glutamatergic terminals, we could then demonstrate the presence of functionally significant A2AR-CB1R heteromers with the same biochemical characteristics of those studied in mammalian transfected cells. First, either an A2AR agonist or an A2AR antagonist allosterically counteracted Gi-mediated CB1R agonist-induced inhibition of depolarization-induced glutamate release. Second, co-application of both an A2AR agonist and an antagonist cancelled each other effects. Finally, a CB1R agonist inhibited glutamate release dependent on a constitutive activation of A2AR by a canonical Gs-Gi antagonistic interaction at the adenylyl cyclase level. Conclusions We demonstrate that the well-established cannabinoid-induced inhibition of striatal glutamate release can mostly be explained by a CB1R-mediated counteraction of the A2AR-mediated constitutive activation of adenylyl cyclase in the A2AR-CB1R heteromer.
Collapse
Affiliation(s)
- Attila Köfalvi
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain
| | - Arnau Cordomí
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Ning-Sheng Cai
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Victor Fernández-Dueñas
- Unitat de Farmacologia, Departament Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
| | - Samira G Ferreira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Ramón Guixà-González
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Marta Sánchez-Soto
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Hideaki Yano
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Verònica Casadó-Anguera
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain
| | - Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ana Maria Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Francisco Ciruela
- Unitat de Farmacologia, Departament Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain. .,Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain.
| | - Leonardo Pardo
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain.
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA.
| |
Collapse
|
8
|
HSP90 Interacts with the Fibronectin N-terminal Domains and Increases Matrix Formation. Cells 2020; 9:cells9020272. [PMID: 31979118 PMCID: PMC7072298 DOI: 10.3390/cells9020272] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/15/2020] [Accepted: 01/18/2020] [Indexed: 12/20/2022] Open
Abstract
Heat shock protein 90 (HSP90) is an evolutionarily conserved chaperone protein that controls the function and stability of a wide range of cellular client proteins. Fibronectin (FN) is an extracellular client protein of HSP90, and exogenous HSP90 or inhibitors of HSP90 alter the morphology of the extracellular matrix. Here, we further characterized the HSP90 and FN interaction. FN bound to the M domain of HSP90 and interacted with both the open and closed HSP90 conformations; and the interaction was reduced in the presence of sodium molybdate. HSP90 interacted with the N-terminal regions of FN, which are known to be important for matrix assembly. The highest affinity interaction was with the 30-kDa (heparin-binding) FN fragment, which also showed the greatest colocalization in cells and accommodated both HSP90 and heparin in the complex. The strength of interaction with HSP90 was influenced by the inherent stability of the FN fragments, together with the type of motif, where HSP90 preferentially bound the type-I FN repeat over the type-II repeat. Exogenous extracellular HSP90 led to increased incorporation of both full-length and 70-kDa fragments of FN into fibrils. Together, our data suggested that HSP90 may regulate FN matrix assembly through its interaction with N-terminal FN fragments.
Collapse
|
9
|
Evidence for functional pre-coupled complexes of receptor heteromers and adenylyl cyclase. Nat Commun 2018; 9:1242. [PMID: 29593213 PMCID: PMC5871782 DOI: 10.1038/s41467-018-03522-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 02/21/2018] [Indexed: 01/13/2023] Open
Abstract
G protein-coupled receptors (GPCRs), G proteins and adenylyl cyclase (AC) comprise one of the most studied transmembrane cell signaling pathways. However, it is unknown whether the ligand-dependent interactions between these signaling molecules are based on random collisions or the rearrangement of pre-coupled elements in a macromolecular complex. Furthermore, it remains controversial whether a GPCR homodimer coupled to a single heterotrimeric G protein constitutes a common functional unit. Using a peptide-based approach, we here report evidence for the existence of functional pre-coupled complexes of heteromers of adenosine A2A receptor and dopamine D2 receptor homodimers coupled to their cognate Gs and Gi proteins and to subtype 5 AC. We also demonstrate that this macromolecular complex provides the necessary frame for the canonical Gs-Gi interactions at the AC level, sustaining the ability of a Gi-coupled GPCR to counteract AC activation mediated by a Gs-coupled GPCR. It is unclear whether GPCRs, G proteins and adenylyl cyclase (AC) associate through random collisions or defined pre-coupling mechanisms. Using a peptide-based approach, the authors show that heteromers of adenosine A2A and dopamine D2 receptors form pre-coupled complexes with their cognate G proteins and AC5.
Collapse
|
10
|
Kaufholdt D, Baillie CK, Meinen R, Mendel RR, Hänsch R. The Molybdenum Cofactor Biosynthesis Network: In vivo Protein-Protein Interactions of an Actin Associated Multi-Protein Complex. FRONTIERS IN PLANT SCIENCE 2017; 8:1946. [PMID: 29184564 PMCID: PMC5694649 DOI: 10.3389/fpls.2017.01946] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/30/2017] [Indexed: 05/09/2023]
Abstract
Survival of plants and nearly all organisms depends on the pterin based molybdenum cofactor (Moco) as well as its effective biosynthesis and insertion into apo-enzymes. To this end, both the central Moco biosynthesis enzymes are characterized and the conserved four-step reaction pathway for Moco biosynthesis is well-understood. However, protection mechanisms to prevent degradation during biosynthesis as well as transfer of the highly oxygen sensitive Moco and its intermediates are not fully enlightened. The formation of protein complexes involving transient protein-protein interactions is an efficient strategy for protected metabolic channelling of sensitive molecules. In this review, Moco biosynthesis and allocation network is presented and discussed. This network was intensively studied based on two in vivo interaction methods: bimolecular fluorescence complementation (BiFC) and split-luciferase. Whereas BiFC allows localisation of interacting partners, split-luciferase assay determines interaction strengths in vivo. Results demonstrate (i) interaction of Cnx2 and Cnx3 within the mitochondria and (ii) assembly of a biosynthesis complex including the cytosolic enzymes Cnx5, Cnx6, Cnx7, and Cnx1, which enables a protected transfer of intermediates. The whole complex is associated with actin filaments via Cnx1 as anchor protein. After biosynthesis, Moco needs to be handed over to the specific apo-enzymes. A potential pathway was discovered. Molybdenum-containing enzymes of the sulphite oxidase family interact directly with Cnx1. In contrast, the xanthine oxidoreductase family acquires Moco indirectly via a Moco binding protein (MoBP2) and Moco sulphurase ABA3. In summary, the uncovered interaction matrix enables an efficient transfer for intermediate and product protection via micro-compartmentation.
Collapse
|
11
|
The use of fluorescence correlation spectroscopy to characterize the molecular mobility of fluorescently labelled G protein-coupled receptors. Biochem Soc Trans 2016; 44:624-9. [PMID: 27068980 PMCID: PMC5264494 DOI: 10.1042/bst20150285] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 01/10/2023]
Abstract
The membranes of living cells have been shown to be highly organized into distinct microdomains, which has spatial and temporal consequences for the interaction of membrane bound receptors and their signalling partners as complexes. Fluorescence correlation spectroscopy (FCS) is a technique with single cell sensitivity that sheds light on the molecular dynamics of fluorescently labelled receptors, ligands or signalling complexes within small plasma membrane regions of living cells. This review provides an overview of the use of FCS to probe the real time quantification of the diffusion and concentration of G protein-coupled receptors (GPCRs), primarily to gain insights into ligand–receptor interactions and the molecular composition of signalling complexes. In addition we document the use of photon counting histogram (PCH) analysis to investigate how changes in molecular brightness (ε) can be a sensitive indicator of changes in molecular mass of fluorescently labelled moieties.
Collapse
|
12
|
Hudson BD. Using Biosensors to Study Free Fatty Acid Receptor Pharmacology and Function. Handb Exp Pharmacol 2016; 236:79-100. [PMID: 27757763 DOI: 10.1007/164_2016_58] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The free fatty acid (FFA) family of G protein coupled receptors (GPCRs) has generated significant interest for exploiting its members as potential drug targets. However, unravelling the complex pharmacology of this family of receptors has proven challenging. In recent years the use of biosensor technologies capable of assessing biological functions in living cells, and in real time, has greatly enhanced our ability to study GPCR pharmacology and function. These include genetically encoded sensors that change the intensity or wavelength of light emitted from a bioluminescent or fluorescent protein in response to a stimulus, as well as non-genetically encoded sensors able to measure more global cellular changes, such as mass redistribution within a cell. This chapter will examine how these sensors can be used to study GPCRs, and in particular how they are helping uncover the pharmacology of the FFA family of receptors.
Collapse
Affiliation(s)
- Brian D Hudson
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, G12 8QQ, UK.
| |
Collapse
|
13
|
Zhang XE, Cui Z, Wang D. Sensing of biomolecular interactions using fluorescence complementing systems in living cells. Biosens Bioelectron 2015; 76:243-50. [PMID: 26316254 DOI: 10.1016/j.bios.2015.07.069] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 07/28/2015] [Accepted: 07/29/2015] [Indexed: 01/09/2023]
Abstract
Sensing biomolecule interactions in living cells allows for a deeper understanding of the mechanisms governing biological processes, and has increasing significance for improvements in clinical diagnosis. It is now possible by using molecular biosensors. One method involving molecular biosensors is called molecular fluorescence complementation, usually referred to as BiFC (bimolecular fragment/fluorescence complementary/complementation) or TriFC (trimolecular fragment complementary/complementation). This complementation method is based on the principle that two non-fluorescent fragments of a fluorescent protein are brought into sufficient lyclose proximity, upon which they are reconstructed so that fluorescence is re-established. This process relies on the interaction between the two fusion partners, which normally are proteins. This method is simple, noninvasive, sensitive, and does not require specialized tools, hence being available to most standard laboratories. Here, we selectively describe three relevant examples, although many other molecular interactions have been shown to work with this method. Recent developments of this method include multicolor BiFC, which allows for simultaneous detection of multi-biomolecule interactions, RNA-protein interactions, far red and near infrared sensing systems for deep tissue imaging. Challenges in the utilization of this method are discussed. Given the current rate of technological advancements, we believe that fluorescence fragment complementing systems have the potential to be utilized across a wide range of areas, including in routine research and clinical diagnosis.
Collapse
Affiliation(s)
- Xian-En Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
| | - Zongqiang Cui
- State Key Laboratory of Virology and Center for Analytical Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, China
| | - Dianbing Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| |
Collapse
|
14
|
Stoddart LA, Kellam B, Briddon SJ, Hill SJ. Effect of a toggle switch mutation in TM6 of the human adenosine A₃ receptor on Gi protein-dependent signalling and Gi-independent receptor internalization. Br J Pharmacol 2015; 171:3827-44. [PMID: 24750014 PMCID: PMC4128046 DOI: 10.1111/bph.12739] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 04/07/2014] [Accepted: 04/14/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE The highly conserved tryptophan (W6.48) in transmembrane domain 6 of GPCRs has been shown to play a central role in forming an active conformation in response to agonist binding. We set out to characterize the effect of this mutation on the efficacy of two agonists at multiple signalling pathways downstream of the adenosine A3 receptor. EXPERIMENTAL APPROACH Residue W6.48 in the human adenosine A3 receptor fused to yellow fluorescent protein was mutated to phenylalanine and expressed in CHO-K1 cells containing a cAMP response element reporter gene. The effects on agonist-mediated receptor internalization were monitored by automated confocal microscopy and image analysis. Further experiments were carried out to investigate agonist-mediated ERK1/2 phosphorylation, inhibition of [3H]-cAMP accumulation and β-arrestin2 binding. KEY RESULTS NECA was able to stimulate agonist-mediated internalization of the W6.48F mutant receptor, while the agonist HEMADO was inactive. Investigation of other downstream signalling pathways indicated that G-protein coupling was impaired for both agonists tested. Mutation of W6.48F therefore resulted in differential effects on agonist efficacy, and introduced signalling pathway bias for HEMADO at the adenosine A3 receptor. CONCLUSIONS AND IMPLICATIONS Investigation of the pharmacology of the W6.48F mutant of the adenosine A3 receptor confirms that this region is important in forming the active conformation of the receptor for stimulating a number of different signalling pathways and that mutations in this residue can lead to changes in agonist efficacy and signalling bias.
Collapse
Affiliation(s)
- Leigh A Stoddart
- Institute of Cell Signalling, School of Life Sciences, The University of Nottingham, Nottingham, UK
| | | | | | | |
Collapse
|
15
|
Gherbi K, May LT, Baker JG, Briddon SJ, Hill SJ. Negative cooperativity across β1-adrenoceptor homodimers provides insights into the nature of the secondary low-affinity CGP 12177 β1-adrenoceptor binding conformation. FASEB J 2015; 29:2859-71. [PMID: 25837585 PMCID: PMC4478806 DOI: 10.1096/fj.14-265199] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 03/02/2015] [Indexed: 01/30/2023]
Abstract
At the β1-adrenoceptor, CGP 12177 potently antagonizes agonist responses at the primary high-affinity catecholamine conformation while also exerting agonist effects of its own through a secondary low-affinity conformation. A recent mutagenesis study identified transmembrane region (TM)4 of the β1-adrenoceptor as key for this low-affinity conformation. Others suggested that TM4 has a role in β1-adrenoceptor oligomerization. Here, assessment of the dissociation rate of a fluorescent analog of CGP 12177 [bordifluoropyrromethane-tetramethylrhodamine-(±)CGP 12177 (BODIPY-TMR-CGP)] at the human β1-adrenoceptor expressed in Chinese hamster ovary cells revealed negative cooperative interactions between 2 distinct β1-adrenoceptor conformations. The dissociation rate of 3 nM BODIPY-TMR-CGP was 0.09 ± 0.01 min−1 in the absence of competitor ligands, and this was enhanced 2.2- and 2.1-fold in the presence of 1 µM CGP 12177 and 1 µM propranolol, respectively. These effects on the BODIPY-TMR-CGP dissociation rate were markedly enhanced in β1-adrenoceptor homodimers constrained by bimolecular fluorescence complementation (9.8- and 9.9-fold for 1 µM CGP 12177 and 1 µM propranolol, respectively) and abolished in β1-adrenoceptors containing TM4 mutations vital for the second conformation pharmacology. This study suggests that negative cooperativity across a β1-adrenoceptor homodimer may be responsible for generating the low-affinity pharmacology of the secondary β1-adrenoceptor conformation.—Gherbi, K., May, L. T., Baker, J. G., Briddon, S. J., Hill, S. J. Negative cooperativity across β1-adrenoceptor homodimers provides insights into the nature of the secondary low-affinity CGP 12177 β1-adrenoceptor binding conformation.
Collapse
Affiliation(s)
- Karolina Gherbi
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Lauren T May
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Jillian G Baker
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Stephen J Briddon
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Stephen J Hill
- Cell Signalling Research Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| |
Collapse
|
16
|
Conway JRW, Carragher NO, Timpson P. Developments in preclinical cancer imaging: innovating the discovery of therapeutics. Nat Rev Cancer 2014; 14:314-28. [PMID: 24739578 DOI: 10.1038/nrc3724] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Integrating biological imaging into early stages of the drug discovery process can provide invaluable readouts of drug activity within complex disease settings, such as cancer. Iterating this approach from initial lead compound identification in vitro to proof-of-principle in vivo analysis represents a key challenge in the drug discovery field. By embracing more complex and informative models in drug discovery, imaging can improve the fidelity and statistical robustness of preclinical cancer studies. In this Review, we highlight how combining advanced imaging with three-dimensional systems and intravital mouse models can provide more informative and disease-relevant platforms for cancer drug discovery.
Collapse
Affiliation(s)
- James R W Conway
- Garvan Institute of Medical Research and The Kinghorn Cancer Centre Sydney, St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, New South Wales 2010, Sydney, Australia
| | - Neil O Carragher
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, EH4 2XR, UK
| | - Paul Timpson
- Garvan Institute of Medical Research and The Kinghorn Cancer Centre Sydney, St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, New South Wales 2010, Sydney, Australia
| |
Collapse
|
17
|
Liu S, Li X, Yang J, Zhang Z. Low false-positives in an mLumin-based bimolecular fluorescence complementation system with a bicistronic expression vector. SENSORS 2014; 14:3284-92. [PMID: 24556667 PMCID: PMC3958255 DOI: 10.3390/s140203284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/15/2014] [Accepted: 01/28/2014] [Indexed: 11/16/2022]
Abstract
The simplicity and sensitivity of the bimolecular fluorescence complementation (BiFC) assay make it a powerful tool to investigate protein-protein interactions (PPIs) in living cells. However, non-specific association of the fluorescent protein fragments in a BiFC system can complicate evaluation of PPIs. Here, we introduced a bicistronic expression vector, pBudCE4.1, into an mLumin-based BiFC system, denoted as the BEVL-BiFC system. The BEVL-BiFC system achieved a 25-fold contrast in BiFC efficiency between positive (Fos/Jun) and negative (ΔFos/Jun) PPIs. The high BiFC efficiency was due to a low false-positive rate, where less than 2% of cells displayed BiFC in the negative control. K-Ras and its interactive proteins, Ras binding domain (RBD) of Raf-1 and Grb2 were used to confirm the accuracy of the BEVL-BiFC system. The results also provide direct evidence in individual cells that post-translational modification of K-Ras and its localization at the plasma membrane (PM) were not essential for the interaction of K-Ras and Raf-1, whereas the interaction of Grb2 and K-Ras did depend on the PM localization of K-Ras. Taken together, the BEVL-BiFC system was developed to reduce the false-positive phenomenon in BiFC assays, resulting in more robust and accurate measurement of PPIs in living cells.
Collapse
Affiliation(s)
- Shun Liu
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Xiangyong Li
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Jie Yang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Zhihong Zhang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
| |
Collapse
|
18
|
Lasry I, Golan Y, Berman B, Amram N, Glaser F, Assaraf YG. In situ dimerization of multiple wild type and mutant zinc transporters in live cells using bimolecular fluorescence complementation. J Biol Chem 2014; 289:7275-92. [PMID: 24451381 DOI: 10.1074/jbc.m113.533786] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Zinc transporters (ZnTs) facilitate zinc efflux and zinc compartmentalization, thereby playing a key role in multiple physiological processes and pathological disorders, presumed to be modulated by transporter dimerization. We recently proposed that ZnT2 homodimerization is the underlying basis for the dominant negative effect of a novel heterozygous G87R mutation identified in women producing zinc-deficient milk. To provide direct visual evidence for the in situ dimerization and function of multiple normal and mutant ZnTs, we applied here the bimolecular fluorescence complementation (BiFC) technique, which enables direct visualization of specific protein-protein interactions. BiFC is based upon reconstitution of an intact fluorescent protein including YFP when its two complementary, non-fluorescent N- and C-terminal fragments (termed YN and YC) are brought together by a pair of specifically interacting proteins. Homodimerization of ZnT1, -2, -3, -4, and -7 was revealed by high subcellular fluorescence observed upon co-transfection of non-fluorescent ZnT-YC and ZnT-YN; this homodimer fluorescence localized in the characteristic compartments of each ZnT. The validity of the BiFC assay in ZnT dimerization was further corroborated when high fluorescence was obtained upon co-transfection of ZnT5-YC and ZnT6-YN, which are known to form heterodimers. We further show that BiFC recapitulated the pathogenic role that ZnT mutations play in transient neonatal zinc deficiency. Zinquin, a fluorescent zinc probe applied along with BiFC, revealed the in situ functionality of ZnT dimers. Hence, the current BiFC-Zinquin technique provides the first in situ evidence for the dimerization and function of wild type and mutant ZnTs in live cells.
Collapse
Affiliation(s)
- Inbal Lasry
- From the Fred Wyszkowski Cancer Research Laboratory, Department of Biology, and
| | | | | | | | | | | |
Collapse
|
19
|
Jaeger WC, Armstrong SP, Hill SJ, Pfleger KDG. Biophysical Detection of Diversity and Bias in GPCR Function. Front Endocrinol (Lausanne) 2014; 5:26. [PMID: 24634666 PMCID: PMC3943086 DOI: 10.3389/fendo.2014.00026] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/19/2014] [Indexed: 12/27/2022] Open
Abstract
Guanine nucleotide binding protein (G protein)-coupled receptors (GPCRs) function in complexes with a range of molecules and proteins including ligands, G proteins, arrestins, ubiquitin, and other receptors. Elements of these complexes may interact constitutively or dynamically, dependent upon factors such as ligand binding, phosphorylation, and dephosphorylation. They may also be allosterically modulated by other proteins in a manner that changes temporally and spatially within the cell. Elucidating how these complexes function has been greatly enhanced by biophysical technologies that are able to monitor proximity and/or binding, often in real time and in live cells. These include resonance energy transfer approaches such as bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET). Furthermore, the use of fluorescent ligands has enabled novel insights into allosteric interactions between GPCRs. Consequently, biophysical approaches are helping to unlock the amazing diversity and bias in G protein-coupled receptor signaling.
Collapse
Affiliation(s)
- Werner C. Jaeger
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
| | - Stephen P. Armstrong
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
| | - Stephen J. Hill
- Cell Signalling Research Group, School of Life Sciences, Queen’s Medical Centre, University of Nottingham Medical School, Nottingham, UK
| | - Kevin D. G. Pfleger
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
- Dimerix Bioscience Pty Ltd, Perth, WA, Australia
- *Correspondence: Kevin D. G. Pfleger, Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, QEII Medical Centre, QQ Block, 6 Verdun Street, Nedlands, Perth, WA 6009, Australia e-mail:
| |
Collapse
|
20
|
Song YB, Park CO, Jeong JY, Huh WK. Monitoring G protein-coupled receptor activation using an adenovirus-based β-arrestin bimolecular fluorescence complementation assay. Anal Biochem 2013; 449:32-41. [PMID: 24361713 DOI: 10.1016/j.ab.2013.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 11/16/2013] [Accepted: 12/10/2013] [Indexed: 01/22/2023]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors and are involved in a variety of pathological conditions including cancer and cardiovascular, metabolic, neurological, and autoimmune diseases. GPCRs are being intensively investigated as targets for therapeutic intervention, and the β-arrestin recruitment assay has become a popular tool for analyzing GPCR activation. Here, we report a high-throughput method for cloning GPCR cDNAs into adenoviral bimolecular fluorescence complementation (BiFC) vectors and performing the β-arrestin BiFC assay in cells transduced with recombinant adenoviruses. An analysis of the activation of somatostatin receptor 2 (SSTR2) with the adenovirus-based β-arrestin BiFC assay showed that the assay is suitable for quantifying SSTR2 activation in response to specific agonists or antagonists. Furthermore, the adenovirus-based β-arrestin BiFC assay was able to detect the activation of a broad range of GPCRs. Collectively, our data indicate that the adenovirus-based β-arrestin BiFC assay can serve as a simple and universal platform for studying GPCR activation and thus will be useful for high-throughput screening of drugs that target GPCRs.
Collapse
Affiliation(s)
- Yong Bhum Song
- Department of Biological Sciences and Research Center for Functional Cellulomics, Seoul National University, Seoul 151-747, Republic of Korea
| | - Chul O Park
- Department of Biological Sciences and Research Center for Functional Cellulomics, Seoul National University, Seoul 151-747, Republic of Korea
| | - Jae-Yeon Jeong
- Marine Biotechnology Research Division, Korea Institute of Ocean Science & Technology, Ansan 426-744, Republic of Korea.
| | - Won-Ki Huh
- Department of Biological Sciences and Research Center for Functional Cellulomics, Seoul National University, Seoul 151-747, Republic of Korea; Institute of Microbiology, Seoul National University, Seoul 151-747, Republic of Korea.
| |
Collapse
|
21
|
Jameson DM, James NG, Albanesi JP. Fluorescence fluctuation spectroscopy approaches to the study of receptors in live cells. Methods Enzymol 2013; 519:87-113. [PMID: 23280108 DOI: 10.1016/b978-0-12-405539-1.00003-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Communication between cells and their environment, including other cells, is often mediated by cell surface receptors. Fluorescence methodologies are among the most important techniques used to study receptors and their interactions, and in the past decade, fluorescence fluctuation spectroscopy (FFS) approaches have been increasingly utilized. In this overview, we illustrate how diverse FFS approaches have been used to elucidate important aspects of receptor systems, including interactions of receptors with their ligands and receptor oligomerization and clustering. We also describe the most popular methods used to introduce fluorescent moieties into the biological systems. Finally, specific attention will be given to cell maintenance and transfection strategies especially as related to microscopy studies.
Collapse
Affiliation(s)
- David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
| | | | | |
Collapse
|
22
|
Ejendal KFK, Conley JM, Hu CD, Watts VJ. Bimolecular fluorescence complementation analysis of G protein-coupled receptor dimerization in living cells. Methods Enzymol 2013; 521:259-79. [PMID: 23351744 DOI: 10.1016/b978-0-12-391862-8.00014-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Emerging evidence indicates that G protein-coupled receptor (GPCR) signaling is mediated by receptor-receptor interactions at multiple levels. Thus, understanding the biochemistry and pharmacology of those receptor complexes is an important part of delineating the fundamental processes associated with GPCR-mediated signaling in human disease. A variety of experimental approaches have been used to explore these complexes, including bimolecular fluorescence complementation (BiFC) and multicolor BiFC (mBiFC). BiFC approaches have recently been used to explore the composition, cellular localization, and drug modulation of GPCR complexes. The basic methods for applying BiFC and mBiFC to study GPCRs in living cells are the subject of the present chapter.
Collapse
Affiliation(s)
- Karin F K Ejendal
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana, USA
| | | | | | | |
Collapse
|
23
|
Systems Analysis of Arrestin Pathway Functions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:431-67. [DOI: 10.1016/b978-0-12-394440-5.00017-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
24
|
Moulédous L, Froment C, Dauvillier S, Burlet-Schiltz O, Zajac JM, Mollereau C. GRK2 protein-mediated transphosphorylation contributes to loss of function of μ-opioid receptors induced by neuropeptide FF (NPFF2) receptors. J Biol Chem 2012; 287:12736-49. [PMID: 22375000 PMCID: PMC3339982 DOI: 10.1074/jbc.m111.314617] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 01/13/2012] [Indexed: 01/25/2023] Open
Abstract
Neuropeptide FF (NPFF) interacts with specific receptors to modulate opioid functions in the central nervous system. On dissociated neurons and neuroblastoma cells (SH-SY5Y) transfected with NPFF receptors, NPFF acts as a functional antagonist of μ-opioid (MOP) receptors by attenuating the opioid-induced inhibition of calcium conductance. In the SH-SY5Y model, MOP and NPFF(2) receptors have been shown to heteromerize. To understand the molecular mechanism involved in the anti-opioid activity of NPFF, we have investigated the phosphorylation status of the MOP receptor using phospho-specific antibody and mass spectrometry. Similarly to direct opioid receptor stimulation, activation of the NPFF(2) receptor by [D-Tyr-1-(NMe)Phe-3]NPFF (1DMe), an analog of NPFF, induced the phosphorylation of Ser-377 of the human MOP receptor. This heterologous phosphorylation was unaffected by inhibition of second messenger-dependent kinases and, contrarily to homologous phosphorylation, was prevented by inactivation of G(i/o) proteins by pertussis toxin. Using siRNA knockdown we could demonstrate that 1DMe-induced Ser-377 cross-phosphorylation and MOP receptor loss of function were mediated by the G protein receptor kinase GRK2. In addition, mass spectrometric analysis revealed that the phosphorylation pattern of MOP receptors was qualitatively similar after treatment with the MOP agonist Tyr-D-Ala-Gly (NMe)-Phe-Gly-ol (DAMGO) or after treatment with the NPFF agonist 1DMe, but the level of multiple phosphorylation was more intense after DAMGO. Finally, NPFF(2) receptor activation was sufficient to recruit β-arrestin2 to the MOP receptor but not to induce its internalization. These data show that NPFF-induced heterologous desensitization of MOP receptor signaling is mediated by GRK2 and could involve transphosphorylation within the heteromeric receptor complex.
Collapse
Affiliation(s)
- Lionel Moulédous
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| | - Carine Froment
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| | - Stéphanie Dauvillier
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| | - Odile Burlet-Schiltz
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| | - Jean-Marie Zajac
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| | - Catherine Mollereau
- From the Institut de Pharmacologie et de Biologie Structurale, CNRS/Université de Toulouse, UMR 5089, 205 Route de Narbonne, 31077 Toulouse Cedex, France
| |
Collapse
|
25
|
Kilpatrick LE, Briddon SJ, Holliday ND. Fluorescence correlation spectroscopy, combined with bimolecular fluorescence complementation, reveals the effects of β-arrestin complexes and endocytic targeting on the membrane mobility of neuropeptide Y receptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1068-81. [PMID: 22487268 PMCID: PMC3793875 DOI: 10.1016/j.bbamcr.2012.03.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 02/29/2012] [Accepted: 03/01/2012] [Indexed: 01/22/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) analysis are powerful ways to study mobility and stoichiometry of G protein coupled receptor complexes, within microdomains of single living cells. However, relating these properties to molecular mechanisms can be challenging. We investigated the influence of β-arrestin adaptors and endocytosis mechanisms on plasma membrane diffusion and particle brightness of GFP-tagged neuropeptide Y (NPY) receptors. A novel GFP-based bimolecular fluorescence complementation (BiFC) system also identified Y1 receptor-β-arrestin complexes. Diffusion co-efficients (D) for Y1 and Y2-GFP receptors in HEK293 cell plasma membranes were 2.22 and 2.15 × 10− 9 cm2 s− 1 respectively. At a concentration which promoted only Y1 receptor endocytosis, NPY treatment reduced Y1-GFP motility (D 1.48 × 10− 9 cm2 s− 1), but did not alter diffusion characteristics of the Y2-GFP receptor. Agonist induced changes in Y1 receptor motility were inhibited by mutations (6A) which prevented β-arrestin recruitment and internalisation; conversely they became apparent in a Y2 receptor mutant with increased β-arrestin affinity. NPY treatment also increased Y1 receptor-GFP particle brightness, changes which indicated receptor clustering, and which were abolished by the 6A mutation. The importance of β-arrestin recruitment for these effects was illustrated by reduced lateral mobility (D 1.20–1.33 × 10− 9 cm2 s− 1) of Y1 receptor-β-arrestin BiFC complexes. Thus NPY-induced changes in Y receptor motility and brightness reflect early events surrounding arrestin dependent endocytosis at the plasma membrane, results supported by a novel combined BiFC/FCS approach to detect the underlying receptor-β-arrestin signalling complex.
Collapse
Affiliation(s)
- Laura E Kilpatrick
- Cell Signaling Research Group, School of Biomedical Sciences, University of Nottingham, the Medical School, Queen's Medical Centre, Nottingham, UK
| | | | | |
Collapse
|
26
|
Juhl C, Beck-Sickinger AG. Molecular tools to characterize adiponectin activity. VITAMINS AND HORMONES 2012; 90:31-56. [PMID: 23017711 DOI: 10.1016/b978-0-12-398313-8.00002-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Within the past years, numerous hormones were found to be secreted by adipose tissue. As these adipokines exert different physiological effects with great importance in obesity, they provide new strategies for the treatment of obesity associated disorders. Adiponectin is one of the most promising targets due to its protective properties in glucose and lipid metabolism, which are mediated by the adiponectin receptor 1 and 2. Within the past decades, substantial progress in understanding the molecular function of this unique ligand-receptor system could be achieved. This review summarizes the most important approaches for the investigation of adiponectin activity. Even though many insights into adipokine function could be achieved, clarification of the detailed mode of action is still challenging. For this reason, this review gives an overview of frequently used methods, which led to the molecular characterization of adiponectin and might help to get more detailed insights into the broad aspects of obesity.
Collapse
Affiliation(s)
- Cathleen Juhl
- Faculty of Biosciences, Pharmacy and Psychology, Institute of Biochemistry, Universität Leipzig, Leipzig, Germany
| | | |
Collapse
|
27
|
Imaging Protein Oligomerization in Neurodegeneration Using Bimolecular Fluorescence Complementation. Methods Enzymol 2012; 506:157-74. [DOI: 10.1016/b978-0-12-391856-7.00033-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
|
28
|
Kilpatrick LE, Holliday ND. Dissecting the pharmacology of G protein-coupled receptor signaling complexes using bimolecular fluorescence complementation. Methods Mol Biol 2012; 897:109-38. [PMID: 22674163 DOI: 10.1007/978-1-61779-909-9_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The affinity of G protein-coupled receptors (GPCRs) for particular ligands is altered by allosteric regulation with other proteins, for example signaling partners such as G proteins or β-arrestins, or multimeric receptor complexes. Studying the ways in which such interactions modulate pharmacology requires techniques that report these events at the molecular level. Options include bimolecular fluorescence complementation (BiFC), an imaging-based method that can directly demonstrate protein-protein association in living cells. Commonly used fluorescent proteins are split into two nonfluorescent halves, which then tag the protein partners under investigation. Interaction between the partners brings the complementary fragments together, allowing refolding and regeneration of the fluorescent protein to indicate that association has occurred. BiFC is irreversible and is not a real-time technique, yet the simplicity of its fluorescent signal holds key advantages for quantification and cellular localization of the resultant complexes.This review introduces general experimental considerations for using the BiFC approach, and describes specific protocols to develop a BiFC assay for GPCR-β-arrestin association, quantified using high content imaging and analysis. A further application of BiFC is to identify a particular protein-protein complex, thereby allowing investigation of its functional properties. This is illustrated in a protocol to quantify ligand-induced internalization of GPCR dimers of precise composition.
Collapse
Affiliation(s)
- Laura E Kilpatrick
- Cell Signalling Research Group, School of Biomedical Sciences, University of Nottingham, The Medical School, Nottingham, UK
| | | |
Collapse
|
29
|
Porotto M, Palmer SG, Palermo LM, Moscona A. Mechanism of fusion triggering by human parainfluenza virus type III: communication between viral glycoproteins during entry. J Biol Chem 2011; 287:778-793. [PMID: 22110138 DOI: 10.1074/jbc.m111.298059] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Parainfluenza viruses enter host cells by fusing the viral and target cell membranes via concerted action of their two envelope glycoproteins: the hemagglutinin-neuraminidase (HN) and the fusion protein (F). Receptor-bound HN triggers F to undergo conformational changes that render it fusion-competent. To address the role of receptor engagement and to elucidate how HN and F interact during the fusion process, we used bimolecular fluorescence complementation to follow the dynamics of human parainfluenza virus type 3 (HPIV3) HN/F pairs in living cells. We show that HN and F associate before receptor engagement. HN drives the formation of HN-F clusters at the site of fusion, and alterations in HN-F interaction determine the fusogenicity of the glycoprotein pair. An interactive site, at the HN dimer interface modulates HN fusion activation property, which is critical for infection of the natural host. This first evidence for the sequence of initial events that lead to viral entry may indicate a new paradigm for understanding Paramyxovirus infection.
Collapse
Affiliation(s)
- Matteo Porotto
- Departments of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021
| | - Samantha G Palmer
- Departments of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021
| | - Laura M Palermo
- Departments of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021
| | - Anne Moscona
- Departments of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021.
| |
Collapse
|
30
|
Haider AJ, Briggs D, Self TJ, Chilvers HL, Holliday ND, Kerr ID. Dimerization of ABCG2 analysed by bimolecular fluorescence complementation. PLoS One 2011; 6:e25818. [PMID: 21991363 PMCID: PMC3185054 DOI: 10.1371/journal.pone.0025818] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 09/11/2011] [Indexed: 12/18/2022] Open
Abstract
ABCG2 is one of three human ATP binding cassette transporters that are functionally capable of exporting a diverse range of substrates from cells. The physiological consequence of ABCG2 multidrug transport activity in leukaemia, and some solid tumours is the acquisition of cancer multidrug resistance. ABCG2 has a primary structure that infers that a minimal functional transporting unit would be a homodimer. Here we investigated the ability of a bimolecular fluorescence complementation approach to examine ABCG2 dimers, and to probe the role of individual amino acid substitutions in dimer formation. ABCG2 was tagged with fragments of venus fluorescent protein (vYFP), and this tagging did not perturb trafficking or function. Co-expression of two proteins bearing N-terminal and C-terminal fragments of YFP resulted in their association and detection of dimerization by fluorescence microscopy and flow cytometry. Point mutations in ABCG2 which may affect dimer formation were examined for alterations in the magnitude of fluorescence complementation signal. Bimolecular fluorescence complementation (BiFC) demonstrated specific ABCG2 dimer formation, but no changes in dimer formation, resulting from single amino acid substitutions, were detected by BiFC analysis.
Collapse
Affiliation(s)
- Ameena J. Haider
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Deborah Briggs
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Tim J. Self
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Hannah L. Chilvers
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Nicholas D. Holliday
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Ian D. Kerr
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
- * E-mail:
| |
Collapse
|
31
|
Lawrence AJ, Heinz A. Imaging - the interface with pharmacology: looking to the future. Br J Pharmacol 2011; 163:1563-4. [DOI: 10.1111/j.1476-5381.2011.01294.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
|
32
|
May LT, Bridge LJ, Stoddart LA, Briddon SJ, Hill SJ. Allosteric interactions across native adenosine-A3 receptor homodimers: quantification using single-cell ligand-binding kinetics. FASEB J 2011; 25:3465-76. [PMID: 21715680 PMCID: PMC3177574 DOI: 10.1096/fj.11-186296] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A growing awareness indicates that many G-protein-coupled receptors (GPCRs) exist as homodimers, but the extent of the cooperativity across the dimer interface has been largely unexplored. Here, measurement of the dissociation kinetics of a fluorescent agonist (ABA-X-BY630) from the human A1 or A3 adenosine receptors expressed in CHO-K1 cells has provided evidence for highly cooperative interactions between protomers of the A3-receptor dimer in single living cells. In the absence of competitive ligands, the dissociation rate constants of ABA-X-BY630 from A1 and A3 receptors were 1.45 ± 0.05 and 0.57 ± 0.07 min−1, respectively. At the A3 receptor, this could be markedly increased by both orthosteric agonists and antagonists [15-, 9-, and 19-fold for xanthine amine congener (XAC), 5′-(N-ethyl carboxamido)adenosine (NECA), and adenosine, respectively] and reduced by coexpression of a nonbinding (N250A) A3-receptor mutant. The changes in ABA-X-BY630 dissociation were much lower at the A1 receptor (1.5-, 1.4-, and 1.5-fold). Analysis of the pEC50 values of XAC, NECA, and adenosine for the ABA-X-BY630-occupied A3-receptor dimer yielded values of 6.0 ± 0.1, 5.9 ± 0.1, and 5.2 ± 0.1, respectively. This study provides new insight into the spatial and temporal specificity of drug action that can be provided by allosteric modulation across a GPCR homodimeric interface.—May, L. T., Bridge, L. J., Stoddart, L. A., Briddon, S. J., Hill, S. J. Allosteric interactions across native adenosine-A3 receptor homodimers: quantification using single-cell ligand-binding kinetics.
Collapse
Affiliation(s)
- Lauren T May
- Institute of Cell Signalling, School of Biomedical Sciences, The University of Nottingham, Nottingham, UK, NG7 2UH
| | | | | | | | | |
Collapse
|
33
|
Porrello ER, Pfleger KDG, Seeber RM, Qian H, Oro C, Abogadie F, Delbridge LMD, Thomas WG. Heteromerization of angiotensin receptors changes trafficking and arrestin recruitment profiles. Cell Signal 2011; 23:1767-76. [PMID: 21740964 DOI: 10.1016/j.cellsig.2011.06.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 05/29/2011] [Accepted: 06/15/2011] [Indexed: 10/18/2022]
Abstract
The cardiovascular hormone angiotensin II (AngII) exerts its actions via two G protein-coupled receptor (GPCR) subtypes, AT(1) and AT(2), which often display antagonistic functions. Methodological constraints have so far precluded detailed analyses of the ligand-dependency, cellular localization, and functional relevance of AngII receptor interactions in live cells. In this study, we utilize a protein-fragment complementation assay (PCA) and GPCR-Heteromer Identification Technology (GPCR-HIT) to provide the first detailed investigation of the ligand-dependency and cellular localization of AngII receptor interactions in human embryonic kidney 293 cells. Fluorescent-tagged receptor constructs for PCA and GPCR-HIT displayed normal affinity and selectivity for AngII (AT(1): IC(50)=1.0-1.6nM; AT(2): IC(50)=2.0-3.0nM). Well-characterized angiotensin receptor interactions were used as positive and negative controls to demonstrate the sensitivity and specificity of these fluorescence-based assays. We report that AT(1)-AT(2) receptor heteromers form constitutively, are localized to the plasma membrane and perinuclear compartments, and do not internalize following AngII stimulation despite arrestin being recruited specifically to the heteromer. Our findings using novel fluorescence-based technologies reveal a previously unrecognized mechanism of angiotensin receptor cross-talk involving cross-inhibition of AT(1) receptor internalization through heteromerization with the AT(2) receptor subtype.
Collapse
Affiliation(s)
- Enzo R Porrello
- Department of Physiology, The University of Melbourne, Victoria 3010, Australia.
| | | | | | | | | | | | | | | |
Collapse
|
34
|
Pétrin D, Hébert TE. Imaging-based approaches to understanding g protein-coupled receptor signalling complexes. Methods Mol Biol 2011; 756:37-60. [PMID: 21870219 DOI: 10.1007/978-1-61779-160-4_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In the last 10 years, imaging assays based on resonance energy transfer (RET) and protein fragment complementation have made it possible to study interactions between components of G protein-coupled receptor (GPCR) signalling complexes in living cells under physiological conditions. Here, we consider the history of such approaches, the current tools available and how they have changed our understanding of GPCR signalling. We also discuss some theoretical and methodological issues important when combining the different types of assay.
Collapse
Affiliation(s)
- Darlaine Pétrin
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC, Canada
| | | |
Collapse
|
35
|
Kilpatrick LE, Briddon SJ, Hill SJ, Holliday ND. Quantitative analysis of neuropeptide Y receptor association with beta-arrestin2 measured by bimolecular fluorescence complementation. Br J Pharmacol 2010; 160:892-906. [PMID: 20438572 PMCID: PMC2901518 DOI: 10.1111/j.1476-5381.2010.00676.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE beta-Arrestins are critical scaffold proteins that shape spatiotemporal signalling from seven transmembrane domain receptors (7TMRs). Here, we study the association between neuropeptide Y (NPY) receptors and beta-arrestin2, using bimolecular fluorescence complementation (BiFC) to directly report underlying protein-protein interactions. EXPERIMENTAL APPROACH Y1 receptors were tagged with a C-terminal fragment, Yc, of yellow fluorescent protein (YFP), and beta-arrestin2 fused with the complementary N-terminal fragment, Yn. After Y receptor-beta-arrestin association, YFP fragment refolding to regenerate fluorescence (BiFC) was examined by confocal microscopy in transfected HEK293 cells. Y receptor/beta-arrestin2 BiFC responses were also quantified by automated imaging and granularity analysis. KEY RESULTS NPY stimulation promoted association between Y1-Yc and beta-arrestin2-Yn, and the specific development of BiFC in intracellular compartments, eliminated when using non-interacting receptor and arrestin mutants. Responses developed irreversibly and were slower than for downstream Y1 receptor-YFP internalization, a consequence of delayed maturation and stability of complemented YFP. However, beta-arrestin2 BiFC measurements delivered appropriate ligand pharmacology for both Y1 and Y2 receptors, and demonstrated higher affinity of Y1 compared to Y2 receptors for beta-arrestin2. Receptor mutagenesis combined with beta-arrestin2 BiFC revealed that alternative arrangements of Ser/Thr residues in the Y1 receptor C tail could support beta-arrestin2 association, and that Y2 receptor-beta-arrestin2 interaction was enhanced by the intracellular loop mutation H155P. CONCLUSIONS AND IMPLICATIONS The BiFC approach quantifies Y receptor ligand pharmacology focused on the beta-arrestin2 pathway, and provides insight into mechanisms of beta-arrestin2 recruitment by activated and phosphorylated 7TMRs, at the level of protein-protein interaction.
Collapse
Affiliation(s)
- L E Kilpatrick
- Institute of Cell Signalling, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, UK
| | | | | | | |
Collapse
|
36
|
|