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Cornut D, Soulié M, Moreno A, Boussambe GNM, Damian M, Igonet S, Guillet P, Banères JL, Durand G. Non-ionic cholesterol-based additives for the stabilization of membrane proteins. Biochimie 2023; 205:27-39. [PMID: 36586567 DOI: 10.1016/j.biochi.2022.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 12/30/2022]
Abstract
We report herein the synthesis of two non-ionic amphiphiles with a cholesterol hydrophobic moiety that can be used as chemical additives for biochemical studies of membrane proteins. They were designed to show a high similarity with the planar steroid core of cholesterol and small-to-medium polar head groups attached at the C3 position of ring-A on the sterol skeleton. The two Chol-Tris and Chol-DG have a Tris-hydroxymethyl and a branched diglucose polar head group, respectively, which provide them sufficient water solubility when mixed with the "gold standard" detergent n-Dodecyl-β-D-Maltoside (DDM). The colloidal properties of these mixed micelles were investigated by means of surface tension (SFT) measurements and dynamic light scattering (DLS) experiments and showed the formation of globular micelles of about 8 nm in diameter with a critical micellar concentration of 0.20 mM for DDM:Chol-DG and 0.22 mM for DDM:Chol-Tris. We showed that mixed micelles do not alter the extraction potency of a G-protein coupled receptor (GPCR): the human adenosine A2A receptor (A2AR). The thermostabilizing effect of the mixed micelles was confirmed on two GPCRs, A2AR and the growth hormone secretagogue receptor (GHSR). Finally, these two mixed micelles were found suitable for the purification of an active form of A2AR which remained able to bind two ligands of different class i.e. the specific agonist CGS-21680 and the specific inverse agonist ZM-241385. This suggests that Chol-Tris and Chol-DG may be used as a non-ionic alternative to the cholesteryl hemisuccinate (CHS) stabilizing agent.
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Affiliation(s)
- Damien Cornut
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM & Avignon Université, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France; CHEM2STAB, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France
| | - Marine Soulié
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM & Avignon Université, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France; CHEM2STAB, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France
| | | | - Gildas Nyame Mendendy Boussambe
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM & Avignon Université, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France; CHEM2STAB, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France
| | - Marjorie Damian
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM, 1919 route de Mende, 34293, Montpellier, Cedex 5, France
| | | | - Pierre Guillet
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM & Avignon Université, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France; CHEM2STAB, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France
| | - Jean-Louis Banères
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM, 1919 route de Mende, 34293, Montpellier, Cedex 5, France
| | - Grégory Durand
- Institut des Biomolécules Max Mousseron UMR 5247 UM-CNRS-ENSCM & Avignon Université, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France; CHEM2STAB, 301 rue Baruch de Spinoza, 84916, Avignon, Cedex 9, France.
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2
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Johansen NT, Tidemand FG, Pedersen MC, Arleth L. Travel light: Essential packing for membrane proteins with an active lifestyle. Biochimie 2023; 205:3-26. [PMID: 35963461 DOI: 10.1016/j.biochi.2022.07.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/29/2022] [Accepted: 07/23/2022] [Indexed: 11/02/2022]
Abstract
We review the considerable progress during the recent decade in the endeavours of designing, optimising, and utilising carrier particle systems for structural and functional studies of membrane proteins in near-native environments. New and improved systems are constantly emerging, novel studies push the perceived limits of a given carrier system, and specific carrier systems consolidate and entrench themselves as the system of choice for particular classes of target membrane protein systems. This review covers the most frequently used carrier systems for such studies and emphasises similarities and differences between these systems as well as current trends and future directions for the field. Particular interest is devoted to the biophysical properties and membrane mimicking ability of each system and the manner in which this may impact an embedded membrane protein and an eventual structural or functional study.
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Affiliation(s)
- Nicolai Tidemand Johansen
- Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark.
| | - Frederik Grønbæk Tidemand
- Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark
| | - Martin Cramer Pedersen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen E, 2100, Denmark
| | - Lise Arleth
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen E, 2100, Denmark
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3
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McGraw C, Koretz KS, Oseid D, Lyman E, Robinson AS. Cholesterol Dependent Activity of the Adenosine A 2A Receptor Is Modulated via the Cholesterol Consensus Motif. Molecules 2022; 27:molecules27113529. [PMID: 35684466 PMCID: PMC9182133 DOI: 10.3390/molecules27113529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/22/2022] [Accepted: 05/23/2022] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Membrane cholesterol dysregulation has been shown to alter the activity of the adenosine A2A receptor (A2AR), a G protein-coupled receptor, thereby implicating cholesterol levels in diseases such as Alzheimer's and Parkinson's. A limited number of A2AR crystal structures show the receptor interacting with cholesterol, as such molecular simulations are often used to predict cholesterol interaction sites. METHODS Here, we use experimental methods to determine whether a specific interaction between amino acid side chains in the cholesterol consensus motif (CCM) of full length, wild-type human A2AR, and cholesterol modulates activity of the receptor by testing the effects of mutational changes on functional consequences, including ligand binding, G protein coupling, and downstream activation of cyclic AMP. RESULTS AND CONCLUSIONS Our data, taken with previously published studies, support a model of receptor state-dependent binding between cholesterol and the CCM, whereby cholesterol facilitates both G protein coupling and downstream signaling of A2AR.
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Affiliation(s)
- Claire McGraw
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA; (C.M.); (D.O.)
| | - Kirsten Swonger Koretz
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA;
| | - Daniel Oseid
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA; (C.M.); (D.O.)
| | - Edward Lyman
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19711, USA;
| | - Anne Skaja Robinson
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA;
- Correspondence: ; Tel.: +1-(412)-268-7673
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4
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Agasid MT, Sørensen L, Urner LH, Yan J, Robinson CV. The Effects of Sodium Ions on Ligand Binding and Conformational States of G Protein-Coupled Receptors-Insights from Mass Spectrometry. J Am Chem Soc 2021; 143:4085-4089. [PMID: 33711230 PMCID: PMC7995251 DOI: 10.1021/jacs.0c11837] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
The use of mass spectrometry
to investigate proteins is now well
established and provides invaluable information for both soluble and
membrane protein assemblies. Maintaining transient noncovalent interactions
under physiological conditions, however, remains challenging. Here,
using nanoscale electrospray ionization emitters, we establish conditions
that enable mass spectrometry of two G protein-coupled receptors (GPCR)
from buffers containing high concentrations of sodium ions. For the
Class A GPCR, the adenosine 2A receptor, we observe ligand-induced
changes to sodium binding of the receptor at the level of individual
sodium ions. We find that antagonists promote sodium binding while
agonists attenuate sodium binding. These findings are in line with
high-resolution X-ray crystallography wherein only inactive conformations
retain sodium ions in allosteric binding pockets. For the glucagon
receptor (a Class B GPCR) we observed enhanced ligand binding in electrospray
buffers containing high concentrations of sodium, as opposed to ammonium
acetate buffers. A combination of native and -omics mass spectrometry
revealed the presence of a lipophilic negative allosteric modulator.
These experiments highlight the advantages of implementing native
mass spectrometry, from electrospray buffers containing high concentrations
of physiologically relevant salts, to inform on allosteric ions or
ligands with the potential to define their roles on GPCR function.
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Affiliation(s)
- Mark T Agasid
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Lars Sørensen
- Global Research Technologies, Novo Nordisk A/S, Novo Nordisk Park, Måløv 2760, Denmark
| | - Leonhard H Urner
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Jun Yan
- Global Research Technologies, Novo Nordisk A/S, Novo Nordisk Park, Måløv 2760, Denmark
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
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5
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Koretz KS, McGraw CE, Stradley S, Elbaradei A, Malmstadt N, Robinson AS. Characterization of binding kinetics of A 2AR to Gα s protein by surface plasmon resonance. Biophys J 2021; 120:1641-1649. [PMID: 33675761 DOI: 10.1016/j.bpj.2021.02.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 02/11/2021] [Accepted: 02/17/2021] [Indexed: 01/09/2023] Open
Abstract
Because of their surface localization, G protein-coupled receptors (GPCRs) are often pharmaceutical targets as they respond to a variety of extracellular stimuli (e.g., light, hormones, small molecules) that may activate or inhibit a downstream signaling response. The adenosine A2A receptor (A2AR) is a well-characterized GPCR that is expressed widely throughout the human body, with over 10 crystal structures determined. Truncation of the A2AR C-terminus is necessary for crystallization as this portion of the receptor is long and unstructured; however, previous work suggests shortening of the A2AR C-terminus from 412 to 316 amino acids (A2AΔ316R) ablates downstream signaling, as measured by cAMP production, to below that of constitutive full-length A2AR levels. As cAMP production is downstream of the first activation event-coupling of G protein to its receptor-investigating that first step in activation is important in understanding how the truncation effects native GPCR function. Here, using purified receptor and Gαs proteins, we characterize the association of A2AR and A2AΔ316R to Gαs with and without GDP or GTPγs using surface plasmon resonance (SPR). Gαs affinity for A2AR was greatest for apo-Gαs, moderately affected in the presence of GDP and nearly completely ablated by the addition of GTPγs. Truncation of the A2AR C-terminus (A2AΔ316R) decreased the affinity of the unliganded receptor for Gαs by ∼20%, suggesting small changes to binding can greatly impact downstream signaling.
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Affiliation(s)
- Kirsten S Koretz
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana; Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Claire E McGraw
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana
| | - Steven Stradley
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana
| | - Ahmed Elbaradei
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California
| | - Noah Malmstadt
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California
| | - Anne S Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana; Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania.
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Activation of G-protein-coupled receptors is thermodynamically linked to lipid solvation. Biophys J 2021; 120:1777-1787. [PMID: 33640381 DOI: 10.1016/j.bpj.2021.02.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/11/2021] [Accepted: 02/22/2021] [Indexed: 12/31/2022] Open
Abstract
Preferential lipid solvation of the G-protein-coupled A2A adenosine receptor (A2AR) is evaluated from 35 μs of all-atom molecular dynamics simulation. A coarse-grained transition matrix algorithm is developed to overcome slow equilibration of the first solvation shell, obtaining estimates of the free energy of solvation by different lipids for the receptor in different activation states. Results indicate preference for solvation by unsaturated chains, which favors the active receptor. A model for lipid-dependent G-protein-coupled receptor activity is proposed in which the chemical potential of lipids in the bulk membrane modulates receptor activity. The entropies associated with moving saturated and unsaturated lipids from bulk to A2AR's first solvation shell are evaluated. Overall, the acyl chains are more disordered (i.e., obtain a favorable entropic contribution) when partitioning to the receptor surface, and this effect is augmented for the saturated chains, which are relatively more ordered in bulk.
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Jain AR, Britton ZT, Markwalter CE, Robinson AS. Improved ligand-binding- and signaling-competent human NK2R yields in yeast using a chimera with the rat NK2R C-terminus enable NK2R-G protein signaling platform. Protein Eng Des Sel 2020; 32:459-469. [PMID: 32400863 DOI: 10.1093/protein/gzaa009] [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: 10/12/2019] [Revised: 03/09/2020] [Accepted: 04/16/2020] [Indexed: 02/07/2023] Open
Abstract
The tachykinin 2 receptor (NK2R) plays critical roles in gastrointestinal, respiratory and mental disorders and is a well-recognized target for therapeutic intervention. To date, therapeutics targeting NK2R have failed to meet regulatory agency approval due in large part to the limited characterization of the receptor-ligand interaction and downstream signaling. Herein, we report a protein engineering strategy to improve ligand-binding- and signaling-competent human NK2R that enables a yeast-based NK2R signaling platform by creating chimeras utilizing sequences from rat NK2R. We demonstrate that NK2R chimeras incorporating the rat NK2R C-terminus exhibited improved ligand-binding yields and downstream signaling in engineered yeast strains and mammalian cells, where observed yields were better than 4-fold over wild type. This work builds on our previous studies that suggest exchanging the C-termini of related and well-expressed family members may be a general protein engineering strategy to overcome limitations to ligand-binding and signaling-competent G protein-coupled receptor yields in yeast. We expect these efforts to result in NK2R drug candidates with better characterized signaling properties.
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Affiliation(s)
- Abhinav R Jain
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA
| | - Zachary T Britton
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,AstraZeneca, Antibody Discovery and Protein Engineering, Gaithersburg, MD 20878, USA
| | - Chester E Markwalter
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Anne S Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA, 70118, USA.,Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy St, Newark, DE, 19716, USA.,Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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8
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Jain AR, Robinson AS. Functional Expression of Adenosine A 3 Receptor in Yeast Utilizing a Chimera with the A 2AR C-Terminus. Int J Mol Sci 2020; 21:E4547. [PMID: 32604732 PMCID: PMC7352405 DOI: 10.3390/ijms21124547] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 06/21/2020] [Accepted: 06/24/2020] [Indexed: 11/26/2022] Open
Abstract
The adenosine A3 receptor (A3R) is the only adenosine receptor subtype to be overexpressed in inflammatory and cancer cells and therefore is considered a novel and promising therapeutic target for inflammatory diseases and cancer. Heterologous expression of A3R at levels to allow biophysical characterization is a major bottleneck in structure-guided drug discovery efforts. Here, we apply protein engineering using chimeric receptors to improve expression and activity in yeast. Previously we had reported improved expression and trafficking of the chimeric A1R variant using a similar approach. In this report, we constructed chimeric A3/A2AR comprising the N-terminus and transmembrane domains from A3R (residues 1-284) and the cytoplasmic C-terminus of the A2AR (residues 291-412). The chimeric receptor showed approximately 2-fold improved expression with a 2-fold decreased unfolded protein response when compared to wild type A3R. Moreover, by varying culture conditions such as initial cell density and induction temperature a further 1.7-fold increase in total receptor yields was obtained. We observed native-like coupling of the chimeric receptor to Gai-Gpa1 in engineered yeast strains, activating the downstream, modified MAPK pathway. This strategy of utilizing chimeric receptor variants in yeast thus provides an exciting opportunity to improve expression and activity of "difficult-to-express" receptors, expanding the opportunity for utilizing yeast in drug discovery.
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Affiliation(s)
- Abhinav R. Jain
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA 70118, USA;
| | - Anne S. Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St Charles Ave, New Orleans, LA 70118, USA;
- Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
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9
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McGraw C, Yang L, Levental I, Lyman E, Robinson AS. Membrane cholesterol depletion reduces downstream signaling activity of the adenosine A 2A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:760-767. [PMID: 30629951 DOI: 10.1016/j.bbamem.2019.01.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 12/14/2018] [Accepted: 01/02/2019] [Indexed: 12/11/2022]
Abstract
Cholesterol has been shown to modulate the activity of multiple G Protein-coupled receptors (GPCRs), yet whether cholesterol acts through specific interactions, indirectly via modifications to the membrane, or via both mechanisms is not well understood. High-resolution crystal structures of GPCRs have identified bound cholesterols; based on a β2-adrenergic receptor (β2AR) structure bound to cholesterol and the presence of conserved amino acids in class A receptors, the cholesterol consensus motif (CCM) was identified. Here in mammalian cells expressing the adenosine A2A receptor (A2AR), ligand dependent production of cAMP is reduced following membrane cholesterol depletion with methyl-beta-cyclodextrin (MβCD), indicating that A2AR signaling is dependent on cholesterol. In contrast, ligand binding is not dependent on cholesterol depletion. All-atom molecular simulations suggest that cholesterol interacts specifically with the CCM when the receptor is in an active state, but not when in an inactive state. Taken together, the data support a model of receptor state-dependent binding between cholesterol and the CCM, which could facilitate both G-protein coupling and downstream signaling of A2AR.
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Affiliation(s)
- Claire McGraw
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA, United States
| | - Lewen Yang
- Department of Physics and Astronomy, University of Delaware, Newark, DE, United States
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, University of Texas- Houston, Houston, TX, United States
| | - Edward Lyman
- Department of Physics and Astronomy, University of Delaware, Newark, DE, United States
| | - Anne Skaja Robinson
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA, United States.
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10
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Jain AR, Stradley SH, Robinson AS. The A2aR C-terminus provides improved total and active expression yields for adenosine receptor chimeras. AIChE J 2018. [DOI: 10.1002/aic.16398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Abhinav R. Jain
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Steven H. Stradley
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Anne S. Robinson
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
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11
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Surveying GPCR solubilisation conditions using surface plasmon resonance. Anal Biochem 2018; 556:23-34. [PMID: 29908863 DOI: 10.1016/j.ab.2018.06.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/08/2018] [Accepted: 06/13/2018] [Indexed: 11/22/2022]
Abstract
Biophysical screening techniques, such as surface plasmon resonance, enable detailed kinetic analysis of ligands binding to solubilised G-protein coupled receptors. The activity of a receptor solubilised out of the membrane is crucially dependent on the environment in which it is suspended. Finding the right conditions is challenging due to the number of variables to investigate in order to determine the optimum solubilisation buffer for any given receptor. In this study we used surface plasmon resonance technology to screen a variety of solubilisation conditions including buffers and detergents for two model receptors: CXCR4 and CCR5. We tested 950 different combinations of solubilisation conditions for both receptors. The activity of both receptors was monitored by using conformation dependent monoclonal antibodies and the binding of small molecule ligands. Despite both receptors belonging to the chemokine receptor family they show some differences in their preference for solubilisation conditions that provide the highest level of binding for both the conformation dependent antibodies and small molecules. The study described here is focused not only on finding the best solubilisation conditions for each receptor, but also on factors that determine the sensitivity of the assay for each receptor. We also suggest how these data about different buffers and detergents can be used as a guide for selecting solubilisation conditions for other membrane proteins.
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12
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McNeely PM, Naranjo AN, Forsten-Williams K, Robinson AS. A 2AR Binding Kinetics in the Ligand Depletion Regime. SLAS DISCOVERY 2016; 22:166-175. [PMID: 27577981 DOI: 10.1177/1087057116667256] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Ligand binding plays a fundamental role in stimulating the downstream signaling of membrane receptors. Here, ligand-binding kinetics of the full-length human adenosine A2A receptor (A2AR) reconstituted in detergent micelles were measured using a fluorescently labeled ligand via fluorescence anisotropy. Importantly, to optimize the signal-to-noise ratio, these experiments were conducted in the ligand depletion regime. In the ligand depletion regime, the assumptions used to determine analytical solutions for one-site binding models for either one or two ligands in competition are no longer valid. We therefore implemented a numerical solution approach to analyze kinetic binding data as experimental conditions approach the ligand depletion regime. By comparing the results from the numerical and the analytical solutions, we highlight the ligand-receptor ratios at which the analytical solution begins to lose predictive accuracy. Using the numerical solution approach, we determined the kinetic rate constants of the fluorescent ligand, FITC-APEC, and those for three unlabeled ligands using competitive association experiments. The association and dissociation rate constants of the unlabeled ligands determined from the competitive association experiments were then independently validated using competitive dissociation data. Based on this study, a numerical solution is recommended to determine kinetic ligand-binding parameters for experiments conducted in the ligand-depletion regime.
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Affiliation(s)
- Patrick M McNeely
- 1 Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA
| | - Andrea N Naranjo
- 1 Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA
| | | | - Anne Skaja Robinson
- 1 Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA.,2 Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA, USA
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