51
|
Yasuda S, Kajiwara Y, Takamuku Y, Suzuki N, Murata T, Kinoshita M. Identification of Thermostabilizing Mutations for Membrane Proteins: Rapid Method Based on Statistical Thermodynamics. J Phys Chem B 2016; 120:3833-43. [DOI: 10.1021/acs.jpcb.6b01405] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
| | | | | | | | - Takeshi Murata
- JST, PRESTO, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
| | | |
Collapse
|
52
|
A generic selection system for improved expression and thermostability of G protein-coupled receptors by directed evolution. Sci Rep 2016; 6:21294. [PMID: 26887595 PMCID: PMC4758055 DOI: 10.1038/srep21294] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/21/2016] [Indexed: 11/09/2022] Open
Abstract
Structural and biophysical studies as well as drug screening approaches on G protein-coupled receptors (GPCRs) have been largely hampered by the poor biophysical properties and low expression yields of this largest class of integral membrane proteins. Thermostabilisation of GPCRs by introduction of stabilising mutations has been a key factor to overcome these limitations. However, labelled ligands with sufficient affinity, which are required for selective binding to the correctly folded receptor, are often not available. Here we describe a novel procedure to improve receptor expression and stability in a generic way, independent of specific ligands, by means of directed evolution in E. coli. We have engineered a homogenous fluorescent reporter assay that only detects receptors which are correctly integrated into the inner cell membrane and, thus, discriminates functional from non-functional receptor species. When we combined this method with a directed evolution procedure we obtained highly expressing mutants of the neurotensin receptor 1 with greatly improved thermostability. By this procedure receptors with poor expression and/or low stability, for which no ligands or only ones with poor binding properties are available, can now be generated in quantities allowing detailed structural and biophysical analysis.
Collapse
|
53
|
How Can Mutations Thermostabilize G-Protein-Coupled Receptors? Trends Pharmacol Sci 2015; 37:37-46. [PMID: 26547284 DOI: 10.1016/j.tips.2015.09.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/14/2015] [Accepted: 09/21/2015] [Indexed: 01/04/2023]
Abstract
Structures of over 30 different G-protein-coupled receptors (GPCRs) have advanced our understanding of cell signaling and have provided a foundation for structure-guided drug design. This exciting progress has required the development of three complementary methods to facilitate GPCR crystallization, one of which is the thermostabilization of receptors by systematic mutagenesis. However, the reason why a particular mutation, or combination of mutations, stabilizes the receptor is not always evident from a static crystal structure. Molecular dynamics (MD) simulations have been used to identify and estimate the energetic factors that affect thermostability through comparing the dynamics of the thermostabilized receptors with structure-based models of the wild-type receptor. The data indicate that receptors are stabilized through a combination of factors, including an increase in receptor rigidity, a decrease in collective motion, reduced stress at specific residues, and the presence of ordered water molecules. Predicting thermostabilizing mutations computationally represents a major challenge for the field.
Collapse
|
54
|
Abstract
We previously determined the structure of neurotensin receptor NTSR1 in an active-like conformation with six thermostabilizing mutations bound to the peptide agonist neurotensin. This receptor was unable to activate G proteins, indicating that the mutations restricted NTSR1 to relate agonist binding to G-protein activation. Here we analyse the effect of three of those mutations (E166A3.49, L310A6.37, F358A7.42) and present two structures of NTSR1 able to catalyse nucleotide exchange at Gα. The presence of F3587.42 causes the conserved W3216.48 to adopt a side chain orientation parallel to the lipid bilayer sealing the collapsed Na+ ion pocket and linking the agonist with residues in the lower receptor part implicated in GPCR activation. In the intracellular receptor half, the bulkier L3106.37 side chain dictates the position of R1673.50 of the highly conserved D/ERY motif. These residues, together with the presence of E1663.49 provide determinants for G-protein activation by NTSR1. The structural basis of how G-protein coupled receptors respond to unique stimuli remains poorly understood. Here, Krumm et al. present new structures of the neurotensin receptor and reveal insights into how ligand binding is linked to structural rearrangements associated with receptor activation.
Collapse
|
55
|
Conformational thermostabilisation of corticotropin releasing factor receptor 1. Sci Rep 2015; 5:11954. [PMID: 26159865 PMCID: PMC4498186 DOI: 10.1038/srep11954] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/11/2015] [Indexed: 01/16/2023] Open
Abstract
Recent technical advances have greatly facilitated G-protein coupled receptors crystallography as evidenced by the number of successful x-ray structures that have been reported recently. These technical advances include novel detergents, specialised crystallography techniques as well as protein engineering solutions such as fusions and conformational thermostabilisation. Using conformational thermostabilisation, it is possible to generate variants of GPCRs that exhibit significantly increased stability in detergent micelles whilst preferentially occupying a single conformation. In this paper we describe for the first time the application of this technique to a member of a class B GPCR, the corticotropin releasing factor receptor 1 (CRF1R). Mutational screening in the presence of the inverse agonist, CP-376395, resulted in the identification of a construct with twelve point mutations that exhibited significantly increased thermal stability in a range of detergents. We further describe the subsequent construct engineering steps that eventually yielded a crystallisation-ready construct which recently led to the solution of the first x-ray structure of a class B receptor. Finally, we have used molecular dynamic simulation to provide structural insight into CRF1R instability as well as the stabilising effects of the mutants, which may be extended to other class B receptors considering the high degree of structural conservation.
Collapse
|
56
|
Heydenreich FM, Vuckovic Z, Matkovic M, Veprintsev DB. Stabilization of G protein-coupled receptors by point mutations. Front Pharmacol 2015; 6:82. [PMID: 25941489 PMCID: PMC4403299 DOI: 10.3389/fphar.2015.00082] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/31/2015] [Indexed: 11/13/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are flexible integral membrane proteins involved in transmembrane signaling. Their involvement in many physiological processes makes them interesting targets for drug development. Determination of the structure of these receptors will help to design more specific drugs, however, their structural characterization has so far been hampered by the low expression and their inherent instability in detergents which made protein engineering indispensable for structural and biophysical characterization. Several approaches to stabilize the receptors in a particular conformation have led to breakthroughs in GPCR structure determination. These include truncations of the flexible regions, stabilization by antibodies and nanobodies, fusion partners, high affinity and covalently bound ligands as well as conformational stabilization by mutagenesis. In this review we focus on stabilization of GPCRs by insertion of point mutations, which lead to increased conformational and thermal stability as well as improved expression levels. We summarize existing mutagenesis strategies with different coverage of GPCR sequence space and depth of information, design and transferability of mutations and the molecular basis for stabilization. We also discuss whether mutations alter the structure and pharmacological properties of GPCRs.
Collapse
Affiliation(s)
- Franziska M Heydenreich
- Laboratory of Biomolecular Research, Paul Scherrer Institut Villigen, Switzerland ; Department of Biology, ETH Zürich Zürich, Switzerland
| | - Ziva Vuckovic
- Laboratory of Biomolecular Research, Paul Scherrer Institut Villigen, Switzerland ; Department of Biology, ETH Zürich Zürich, Switzerland
| | - Milos Matkovic
- Laboratory of Biomolecular Research, Paul Scherrer Institut Villigen, Switzerland ; Department of Biology, ETH Zürich Zürich, Switzerland
| | - Dmitry B Veprintsev
- Laboratory of Biomolecular Research, Paul Scherrer Institut Villigen, Switzerland ; Department of Biology, ETH Zürich Zürich, Switzerland
| |
Collapse
|
57
|
Thomas JA, Tate CG. Quality control in eukaryotic membrane protein overproduction. J Mol Biol 2015; 426:4139-4154. [PMID: 25454020 PMCID: PMC4271737 DOI: 10.1016/j.jmb.2014.10.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 10/12/2014] [Accepted: 10/13/2014] [Indexed: 10/25/2022]
Abstract
The overexpression of authentically folded eukaryotic membrane proteins in milligramme quantities is a fundamental prerequisite for structural studies. One of the most commonly used expression systems for the production of mammalian membrane proteins is the baculovirus expression system in insect cells. However, a detailed analysis by radioligand binding and comparative Western blotting of G protein-coupled receptors and a transporter produced in insect cells showed that a considerable proportion of the expressed protein was misfolded and incapable of ligand binding. In contrast, production of the same membrane proteins in stable inducible mammalian cell lines suggested that the majority was folded correctly. It was noted that detergent solubilisation of the misfolded membrane proteins using either digitonin or dodecylmaltoside was considerablyless efficient than using sodium dodecyl sulfate or foscholine-12, whilst these detergents were equally efficient at solubilising correctly folded membrane proteins. This provides a simple and rapid test to suggest whether heterologously expressed mammalian membrane proteins are indeed correctly folded, without requiring radioligand binding assays. This will greatly facilitate the high-throughput production of fully functional membrane proteins for structural studies.
Collapse
Affiliation(s)
- Jennifer A Thomas
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Christopher G Tate
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK.
| |
Collapse
|
58
|
Lee S, Bhattacharya S, Tate CG, Grisshammer R, Vaidehi N. Structural dynamics and thermostabilization of neurotensin receptor 1. J Phys Chem B 2015; 119:4917-28. [PMID: 25807267 PMCID: PMC4564841 DOI: 10.1021/jp510735f] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The neurotensin receptor NTSR1 binds the peptide agonist neurotensin (NTS) and signals preferentially via the Gq protein. Recently, Grisshammer and co-workers reported the crystal structure of a thermostable mutant NTSR1-GW5 with NTS bound. Understanding how the mutations thermostabilize the structure would allow efficient design of thermostable mutant GPCRs for protein purification, and subsequent biophysical studies. Using microsecond scale molecular dynamics simulations (4 μs) of the thermostable mutant NTSR1-GW5 and wild type NTSR1, we have elucidated the structural and energetic factors that affect the thermostability and dynamics of NTSR1. The thermostable mutant NTSR1-GW5 is found to be less flexible and less dynamic than the wild type NTSR1. The point mutations confer thermostability by improving the interhelical hydrogen bonds, hydrophobic packing, and receptor interactions with the lipid bilayer, especially in the intracellular regions. During MD, NTSR1-GW5 becomes more hydrated compared to wild type NTSR1, with tight hydrogen bonded water clusters within the transmembrane core of the receptor, thus providing evidence that water plays an important role in improving helical packing in the thermostable mutant. Our studies provide valuable insights into the stability and functioning of NTSR1 that will be useful in future design of thermostable mutants of other peptide GPCRs.
Collapse
Affiliation(s)
- Sangbae Lee
- †Division of Immunology, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| | - Supriyo Bhattacharya
- †Division of Immunology, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| | - Christopher G Tate
- ‡MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, U.K
| | - Reinhard Grisshammer
- §Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Nagarajan Vaidehi
- †Division of Immunology, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, California 91010, United States
| |
Collapse
|
59
|
Milić D, Veprintsev DB. Large-scale production and protein engineering of G protein-coupled receptors for structural studies. Front Pharmacol 2015; 6:66. [PMID: 25873898 PMCID: PMC4379943 DOI: 10.3389/fphar.2015.00066] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Accepted: 03/13/2015] [Indexed: 01/26/2023] Open
Abstract
Structural studies of G protein-coupled receptors (GPCRs) gave insights into molecular mechanisms of their action and contributed significantly to molecular pharmacology. This is primarily due to technical advances in protein engineering, production and crystallization of these important receptor targets. On the other hand, NMR spectroscopy of GPCRs, which can provide information about their dynamics, still remains challenging due to difficulties in preparation of isotopically labeled receptors and their low long-term stabilities. In this review, we discuss methods used for expression and purification of GPCRs for crystallographic and NMR studies. We also summarize protein engineering methods that played a crucial role in obtaining GPCR crystal structures.
Collapse
Affiliation(s)
- Dalibor Milić
- Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen Switzerland
| | - Dmitry B Veprintsev
- Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen Switzerland ; Department of Biology, Eidgenössische Technische Hochschule Zürich, Zürich Switzerland
| |
Collapse
|
60
|
Hirozane Y, Motoyaji T, Maru T, Okada K, Tarui N. Generating thermostabilized agonist-bound GPR40/FFAR1 using virus-like particles and a label-free binding assay. Mol Membr Biol 2015; 31:168-75. [PMID: 25068810 DOI: 10.3109/09687688.2014.923588] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Elucidating the detailed mechanism of activation of membrane protein receptors and their ligand binding is essential for structure-based drug design. Membrane protein crystal structure analysis successfully aids in understanding these fundamental molecular interactions. However, protein crystal structure analysis of the G-protein-coupled receptor (GPCR) remains challenging, even for the class of GPCRs which have been included in the majority of structure analysis reports among membrane proteins, due to the substantial instability of these receptors when extracted from lipid bilayer membranes. It is known that increased thermostability tends to decrease conformational flexibility, which contributes to the generation of diffraction quality crystals. However, this is still not straightforward, and significant effort is required to identify thermostabilized mutants that are optimal for crystallography. To address this issue, a versatile screening platform based on a label-free ligand binding assay combined with transient overexpression in virus-like particles was developed. This platform was used to generate thermostabilized GPR40 [also known as free fatty acid receptor 1 (FFAR1)] for fasiglifam (TAK-875). This demonstrated that the thermostabilized mutant GPR40 (L42A/F88A/G103A/Y202F) was successfully used for crystal structure analysis.
Collapse
Affiliation(s)
- Yoshihiko Hirozane
- Biomolecular Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd , Fujisawa, Kanagawa , Japan
| | | | | | | | | |
Collapse
|
61
|
Bertheleme N, Singh S, Dowell SJ, Hubbard J, Byrne B. Loss of constitutive activity is correlated with increased thermostability of the human adenosine A2A receptor. Br J Pharmacol 2015; 169:988-98. [PMID: 23489072 DOI: 10.1111/bph.12165] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 02/12/2013] [Accepted: 02/19/2013] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND AND PURPOSE Thermostabilization by mutagenesis is one method which has facilitated the determination of high-resolution structures of the adenosine A2A receptor (A(2A)R). Sets of mutations were identified, which both thermostabilized the receptor and resulted in preferential agonist (Rag23 mutant) or antagonist (Rant5 and Rant21) binding forms as assessed by radioligand binding analysis. While the ligand-binding profiles of these mutants are known, the effects these mutations have on receptor activation and downstream signalling are less well characterized. EXPERIMENTAL APPROACH Here we have investigated the effects of the thermostabilizing mutations on receptor activation using a yeast cell growth assay. The assay employs an engineered Saccharomyces cerevisiae, MMY24, which couples receptor activation to cell growth. KEY RESULTS Analysis of the receptor activation profile revealed that the wild-type (WT) A(2A)R had considerable constitutive activity. In contrast, the Rag23, Rant5 and Rant21 thermostabilized mutants all exhibited no constitutive activity. While the preferentially antagonist-binding mutants Rant5 and Rant21 showed a complete lack of agonist-induced activity, the Rag23 mutant showed high levels of agonist-induced receptor activity. Further analysis using a mutant intermediate between Rag23 and WT indicated that the loss of constitutive activity observed in the agonist responsive mutants was not due to reduced G-protein coupling. CONCLUSIONS AND IMPLICATIONS The loss of constitutive activity may be an important feature of these thermostabilized GPCRs. In addition, the constitutively active and agonist-induced active conformations of the A(2A)R are distinct.
Collapse
|
62
|
Miller DM, Gulbis JM. Engineering protocells: prospects for self-assembly and nanoscale production-lines. Life (Basel) 2015; 5:1019-53. [PMID: 25815781 PMCID: PMC4500129 DOI: 10.3390/life5021019] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Revised: 03/09/2015] [Accepted: 03/16/2015] [Indexed: 11/16/2022] Open
Abstract
The increasing ease of producing nucleic acids and proteins to specification offers potential for design and fabrication of artificial synthetic "organisms" with a myriad of possible capabilities. The prospects for these synthetic organisms are significant, with potential applications in diverse fields including synthesis of pharmaceuticals, sources of renewable fuel and environmental cleanup. Until now, artificial cell technology has been largely restricted to the modification and metabolic engineering of living unicellular organisms. This review discusses emerging possibilities for developing synthetic protocell "machines" assembled entirely from individual biological components. We describe a host of recent technological advances that could potentially be harnessed in design and construction of synthetic protocells, some of which have already been utilized toward these ends. More elaborate designs include options for building self-assembling machines by incorporating cellular transport and assembly machinery. We also discuss production in miniature, using microfluidic production lines. While there are still many unknowns in the design, engineering and optimization of protocells, current technologies are now tantalizingly close to the capabilities required to build the first prototype protocells with potential real-world applications.
Collapse
Affiliation(s)
- David M Miller
- The Walter and Eliza Hall Institute of Medical Research, Parkville VIC 3052, Australia.
- Department of Medical Biology, The University of Melbourne, Parkville VIC 3052, Australia.
| | - Jacqueline M Gulbis
- The Walter and Eliza Hall Institute of Medical Research, Parkville VIC 3052, Australia.
- Department of Medical Biology, The University of Melbourne, Parkville VIC 3052, Australia.
| |
Collapse
|
63
|
Beuming T, Lenselink B, Pala D, McRobb F, Repasky M, Sherman W. Docking and Virtual Screening Strategies for GPCR Drug Discovery. Methods Mol Biol 2015; 1335:251-76. [PMID: 26260606 DOI: 10.1007/978-1-4939-2914-6_17] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Progress in structure determination of G protein-coupled receptors (GPCRs) has made it possible to apply structure-based drug design (SBDD) methods to this pharmaceutically important target class. The quality of GPCR structures available for SBDD projects fall on a spectrum ranging from high resolution crystal structures (<2 Å), where all water molecules in the binding pocket are resolved, to lower resolution (>3 Å) where some protein residues are not resolved, and finally to homology models that are built using distantly related templates. Each GPCR project involves a distinct set of opportunities and challenges, and requires different approaches to model the interaction between the receptor and the ligands. In this review we will discuss docking and virtual screening to GPCRs, and highlight several refinement and post-processing steps that can be used to improve the accuracy of these calculations. Several examples are discussed that illustrate specific steps that can be taken to improve upon the docking and virtual screening accuracy. While GPCRs are a unique target class, many of the methods and strategies outlined in this review are general and therefore applicable to other protein families.
Collapse
Affiliation(s)
- Thijs Beuming
- Schrödinger, Inc., 120 West 45th Street, New York, NY, 10036, USA,
| | | | | | | | | | | |
Collapse
|
64
|
Folding and stability of integral membrane proteins in amphipols. Arch Biochem Biophys 2014; 564:327-43. [PMID: 25449655 DOI: 10.1016/j.abb.2014.10.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/11/2014] [Accepted: 10/22/2014] [Indexed: 11/23/2022]
Abstract
Amphipols (APols) are a family of amphipathic polymers designed to keep transmembrane proteins (TMPs) soluble in aqueous solutions in the absence of detergent. APols have proven remarkably efficient at (i) stabilizing TMPs, as compared to detergent solutions, and (ii) folding them from a denatured state to a native, functional one. The underlying physical-chemical mechanisms are discussed.
Collapse
|
65
|
Bhattacharya S, Lee S, Grisshammer R, Tate CG, Vaidehi N. Rapid Computational Prediction of Thermostabilizing Mutations for G Protein-Coupled Receptors. J Chem Theory Comput 2014; 10:5149-5160. [PMID: 25400524 PMCID: PMC4230369 DOI: 10.1021/ct500616v] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 01/22/2023]
Abstract
![]()
G protein-coupled
receptors (GPCRs) are highly dynamic and often
denature when extracted in detergents. Deriving thermostable mutants
has been a successful strategy to stabilize GPCRs in detergents, but
this process is experimentally tedious. We have developed a computational
method to predict the position of the thermostabilizing mutations
for a given GPCR sequence. We have validated the method against experimentally
measured thermostability data for single mutants of the β1-adrenergic receptor (β1AR), adenosine A2A receptor (A2AR) and neurotensin receptor 1 (NTSR1).
To make these predictions we started from homology models of these
receptors of varying accuracies and generated an ensemble of conformations
by sampling the rigid body degrees of freedom of transmembrane helices.
Then, an all-atom force field function was used to calculate the enthalpy
gain, known as the “stability score” upon mutation of
every residue, in these receptor structures, to alanine. For all three
receptors, β1AR, A2AR, and NTSR1, we observed
that mutations of hydrophobic residues in the transmembrane domain
to alanine that have high stability scores correlate with high experimental
thermostability. The prediction using the stability score improves
when using an ensemble of receptor conformations compared to a single
structure, showing that receptor flexibility is important. We also
find that our previously developed LITiCon method for generating conformation
ensembles is similar in performance to predictions using ensembles
obtained from microseconds of molecular dynamics simulations (which
is computationally hundred times slower than LITiCon). We improved
the thermostability prediction by including other properties such
as residue-based stress and the extent of allosteric communication
by each residue in the stability score. Our method is the first step
toward a computational method for rapid prediction of thermostable
mutants of GPCRs.
Collapse
Affiliation(s)
- Supriyo Bhattacharya
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
| | - Sangbae Lee
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
| | - Reinhard Grisshammer
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health , Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Christopher G Tate
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus , Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Nagarajan Vaidehi
- Division of Immunology, Beckman Research Institute of the City of Hope , 1500 East Duarte Rd, Duarte, California 91010, United States
| |
Collapse
|
66
|
Shepherd CA, Hopkins AL, Navratilova I. Fragment screening by SPR and advanced application to GPCRs. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:113-23. [PMID: 25301577 DOI: 10.1016/j.pbiomolbio.2014.09.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 12/31/2022]
Abstract
Surface plasmon resonance (SPR) is one of the primary biophysical methods for the screening of low molecular weight 'fragment' libraries, due to its low protein consumption and 'label-free' methodology. SPR biosensor interaction analysis is employed to both screen and confirm the binding of compounds in fragment screening experiments, as it provides accurate information on the affinity and kinetics of molecular interactions. The most advanced application of the use of SPR for fragment screening is against membrane protein drug targets, such G-protein coupled receptors (GPCRs). Biophysical GPCR assays using SPR have been validated with pharmacological measurements approximate to cell-based methods, yet provide the advantage of biophysical methods in their ability to measure the weak affinities of low molecular weight fragments. A number of SPR fragment screens against GPCRs have now been disclosed in the literature. SPR fragment screening is proving versatile to screen both thermostabilised GPCRs and solubilised wild type receptors. In this chapter, we discuss the state-of-the-art in GPCR fragment screening by SPR and the technical considerations in performing such experiments.
Collapse
Affiliation(s)
- Claire A Shepherd
- Division of Biological Chemistry and Drug Discovery, College of Life Science, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
| | - Andrew L Hopkins
- Division of Biological Chemistry and Drug Discovery, College of Life Science, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom.
| | - Iva Navratilova
- Division of Biological Chemistry and Drug Discovery, College of Life Science, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
| |
Collapse
|
67
|
Congreve M, Dias JM, Marshall FH. Structure-based drug design for G protein-coupled receptors. PROGRESS IN MEDICINAL CHEMISTRY 2014; 53:1-63. [PMID: 24418607 DOI: 10.1016/b978-0-444-63380-4.00001-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Our understanding of the structural biology of G protein-coupled receptors has undergone a transformation over the past 5 years. New protein-ligand complexes are described almost monthly in high profile journals. Appreciation of how small molecules and natural ligands bind to their receptors has the potential to impact enormously how medicinal chemists approach this major class of receptor targets. An outline of the key topics in this field and some recent examples of structure- and fragment-based drug design are described. A table is presented with example views of each G protein-coupled receptor for which there is a published X-ray structure, including interactions with small molecule antagonists, partial and full agonists. The possible implications of these new data for drug design are discussed.
Collapse
Affiliation(s)
- Miles Congreve
- Heptares Therapeutics Ltd, BioPark, Welwyn Garden City, Hertfordshire, United Kingdom
| | - João M Dias
- Heptares Therapeutics Ltd, BioPark, Welwyn Garden City, Hertfordshire, United Kingdom
| | - Fiona H Marshall
- Heptares Therapeutics Ltd, BioPark, Welwyn Garden City, Hertfordshire, United Kingdom
| |
Collapse
|
68
|
Scott DJ, Kummer L, Egloff P, Bathgate RAD, Plückthun A. Improving the apo-state detergent stability of NTS1 with CHESS for pharmacological and structural studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2817-24. [PMID: 25064156 DOI: 10.1016/j.bbamem.2014.07.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 11/18/2022]
Abstract
The largest single class of drug targets is the G protein-coupled receptor (GPCR) family. Modern high-throughput methods for drug discovery require working with pure protein, but this has been a challenge for GPCRs, and thus the success of screening campaigns targeting soluble, catalytic protein domains has not yet been realized for GPCRs. Therefore, most GPCR drug screening has been cell-based, whereas the strategy of choice for drug discovery against soluble proteins is HTS using purified proteins coupled to structure-based drug design. While recent developments are increasing the chances of obtaining GPCR crystal structures, the feasibility of screening directly against purified GPCRs in the unbound state (apo-state) remains low. GPCRs exhibit low stability in detergent micelles, especially in the apo-state, over the time periods required for performing large screens. Recent methods for generating detergent-stable GPCRs, however, offer the potential for researchers to manipulate GPCRs almost like soluble enzymes, opening up new avenues for drug discovery. Here we apply cellular high-throughput encapsulation, solubilization and screening (CHESS) to the neurotensin receptor 1 (NTS1) to generate a variant that is stable in the apo-state when solubilized in detergents. This high stability facilitated the crystal structure determination of this receptor and also allowed us to probe the pharmacology of detergent-solubilized, apo-state NTS1 using robotic ligand binding assays. NTS1 is a target for the development of novel antipsychotics, and thus CHESS-stabilized receptors represent exciting tools for drug discovery.
Collapse
Affiliation(s)
- Daniel J Scott
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; The Florey Institute of Neuroscience and Mental Health, and The Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Lutz Kummer
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Pascal Egloff
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Ross A D Bathgate
- The Florey Institute of Neuroscience and Mental Health, and The Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Andreas Plückthun
- Department of Biochemistry, The University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| |
Collapse
|
69
|
Structure of class C GPCR metabotropic glutamate receptor 5 transmembrane domain. Nature 2014; 511:557-62. [DOI: 10.1038/nature13396] [Citation(s) in RCA: 337] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 04/22/2014] [Indexed: 12/19/2022]
|
70
|
Miller-Gallacher JL, Nehmé R, Warne T, Edwards PC, Schertler GFX, Leslie AGW, Tate CG. The 2.1 Å resolution structure of cyanopindolol-bound β1-adrenoceptor identifies an intramembrane Na+ ion that stabilises the ligand-free receptor. PLoS One 2014; 9:e92727. [PMID: 24663151 PMCID: PMC3963952 DOI: 10.1371/journal.pone.0092727] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 02/25/2014] [Indexed: 12/30/2022] Open
Abstract
The β1-adrenoceptor (β1AR) is a G protein-coupled receptor (GPCR) that is activated by the endogenous agonists adrenaline and noradrenaline. We have determined the structure of an ultra-thermostable β1AR mutant bound to the weak partial agonist cyanopindolol to 2.1 Å resolution. High-quality crystals (100 μm plates) were grown in lipidic cubic phase without the assistance of a T4 lysozyme or BRIL fusion in cytoplasmic loop 3, which is commonly employed for GPCR crystallisation. An intramembrane Na+ ion was identified co-ordinated to Asp872.50, Ser1283.39 and 3 water molecules, which is part of a more extensive network of water molecules in a cavity formed between transmembrane helices 1, 2, 3, 6 and 7. Remarkably, this water network and Na+ ion is highly conserved between β1AR and the adenosine A2A receptor (rmsd of 0.3 Å), despite an overall rmsd of 2.4 Å for all Cα atoms and only 23% amino acid identity in the transmembrane regions. The affinity of agonist binding and nanobody Nb80 binding to β1AR is unaffected by Na+ ions, but the stability of the receptor is decreased by 7.5°C in the absence of Na+. Mutation of amino acid side chains that are involved in the co-ordination of either Na+ or water molecules in the network decreases the stability of β1AR by 5–10°C. The data suggest that the intramembrane Na+ and associated water network stabilise the ligand-free state of β1AR, but still permits the receptor to form the activated state which involves the collapse of the Na+ binding pocket on agonist binding.
Collapse
Affiliation(s)
| | - Rony Nehmé
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Tony Warne
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Patricia C. Edwards
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Gebhard F. X. Schertler
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Andrew G. W. Leslie
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Christopher G. Tate
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
- * E-mail:
| |
Collapse
|
71
|
Bertheleme N, Strege A, Bunting SE, Dowell SJ, Byrne B. Arginine 199 and leucine 208 have key roles in the control of adenosine A2A receptor signalling function. PLoS One 2014; 9:e89613. [PMID: 24595172 PMCID: PMC3940607 DOI: 10.1371/journal.pone.0089613] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/21/2014] [Indexed: 02/03/2023] Open
Abstract
One successful approach to obtaining high-resolution crystal structures of G-protein coupled receptors is the introduction of thermostabilising mutations within the receptor. This technique allows the generation of receptor constructs stabilised into different conformations suitable for structural studies. Previously, we functionally characterised a number of mutants of the adenosine A2A receptor, thermostabilised either in an agonist or antagonist conformation, using a yeast cell growth assay and demonstrated that there is a correlation between thermostability and loss of constitutive activity. Here we report the functional characterisation of 30 mutants intermediate between the Rag23 (agonist conformation mutant) and the wild-type receptor using the same yeast signalling assay with the aim of gaining greater insight into the role individual amino acids have in receptor function. The data showed that R199 and L208 have important roles in receptor function; substituting either of these residues for alanine abolishes constitutive activity. In addition, the R199A mutation markedly reduces receptor potency while L208A reduces receptor efficacy. A184L and L272A mutations also reduce constitutive activity and potency although to a lesser extent than the R199A and L208A. In contrast, the F79A mutation increases constitutive activity, potency and efficacy of the receptor. These findings shed new light on the role individual residues have on stability of the receptor and also provide some clues as to the regions of the protein responsible for constitutive activity. Furthermore, the available adenosine A2A receptor structures have allowed us to put our findings into a structural context.
Collapse
Affiliation(s)
- Nicolas Bertheleme
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Annette Strege
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Sorrel E. Bunting
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Simon J. Dowell
- Department of Molecular Discovery Research, GlaxoSmithKline, Hertfordshire, United Kingdom
| | - Bernadette Byrne
- Department of Life Sciences, Imperial College London, London, United Kingdom
- * E-mail:
| |
Collapse
|
72
|
Vaidehi N, Bhattacharya S, Larsen AB. Structure and dynamics of G-protein coupled receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 796:37-54. [PMID: 24158800 DOI: 10.1007/978-94-007-7423-0_3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G-protein coupled receptors (GPCRs) are seven helical transmembrane proteins that mediate cell-to-cell communication. They also form the largest superfamily of drug targets. Hence detailed studies of the three dimensional structure and dynamics are critical to understanding the functional role of GPCRs in signal transduction pathways, and for drug design. In this chapter we compare the features of the crystal structures of various biogenic amine receptors, such as β1 and β2 adrenergic receptors, dopamine D3 receptor, M2 and M3 muscarinic acetylcholine receptors. This analysis revealed that conserved residues are located facing the inside of the transmembrane domain in these GPCRs improving the efficiency of packing of these structures. The NMR structure of the chemokine receptor CXCR1 without any ligand bound, shows significant dynamics of the transmembrane domain, especially the helical kink angle on the transmembrane helix6. The activation mechanism of the β2-adrenergic receptor has been studied using multiscale computational methods. The results of these studies showed that the receptor without any ligand bound, samples conformations that resemble some of the structural characteristics of the active state of the receptor. Ligand binding stabilizes some of the conformations already sampled by the apo receptor. This was later observed in the NMR study of the dynamics of human β2-adrenergic receptor. The dynamic nature of GPCRs leads to a challenge in obtaining purified receptors for biophysical studies. Deriving thermostable mutants of GPCRs has been a successful strategy to reduce the conformational heterogeneity and stabilize the receptors. This has lead to several crystal structures of GPCRs. However, the cause of how these mutations lead to thermostability is not clear. Computational studies are beginning to shed some insight into the possible structural basis for the thermostability. Molecular Dynamics simulations studying the conformational ensemble of thermostable mutants have shown that the stability could arise from both enthalpic and entropic factors. There are regions of high stress in the wild type GPCR that gets relieved upon mutation conferring thermostability.
Collapse
Affiliation(s)
- Nagarajan Vaidehi
- Division of Immunology, Beckman Research Institute of the City of Hope, 1500, E. Duarte Road, Duarte, CA, 91010, USA,
| | | | | |
Collapse
|
73
|
L. Pollock N, Moran O, Baroni D, Zegarra-Moran O, C. Ford R. Characterisation of the salmon cystic fibrosis transmembrane conductance regulator protein for structural studies. AIMS MOLECULAR SCIENCE 2014. [DOI: 10.3934/molsci.2014.4.141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
74
|
Sridharan R, Zuber J, Connelly SM, Mathew E, Dumont ME. Fluorescent approaches for understanding interactions of ligands with G protein coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1838:15-33. [PMID: 24055822 PMCID: PMC3926105 DOI: 10.1016/j.bbamem.2013.09.005] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 09/03/2013] [Accepted: 09/08/2013] [Indexed: 11/18/2022]
Abstract
G protein coupled receptors are responsible for a wide variety of signaling responses in diverse cell types. Despite major advances in the determination of structures of this class of receptors, the underlying mechanisms by which binding of different types of ligands specifically elicits particular signaling responses remain unclear. The use of fluorescence spectroscopy can provide important information about the process of ligand binding and ligand dependent conformational changes in receptors, especially kinetic aspects of these processes that can be difficult to extract from X-ray structures. We present an overview of the extensive array of fluorescent ligands that have been used in studies of G protein coupled receptors and describe spectroscopic approaches for assaying binding and probing the environment of receptor-bound ligands with particular attention to examples involving yeast pheromone receptors. In addition, we discuss the use of fluorescence spectroscopy for detecting and characterizing conformational changes in receptors induced by the binding of ligands. Such studies have provided strong evidence for diversity of receptor conformations elicited by different ligands, consistent with the idea that GPCRs are not simple on and off switches. This diversity of states constitutes an underlying mechanistic basis for biased agonism, the observation that different stimuli can produce different responses from a single receptor. It is likely that continued technical advances will allow fluorescence spectroscopy to play an important role in continued probing of structural transitions in G protein coupled receptors. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding.
Collapse
Affiliation(s)
- Rajashri Sridharan
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Jeffrey Zuber
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Sara M. Connelly
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Elizabeth Mathew
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Mark E. Dumont
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
- Department of Pediatrics, P.O. Box 777, University of Rochester Medical Center, Rochester, NY 14642
| |
Collapse
|
75
|
Andrews SP, Brown GA, Christopher JA. Structure-Based and Fragment-Based GPCR Drug Discovery. ChemMedChem 2013; 9:256-75. [DOI: 10.1002/cmdc.201300382] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 11/15/2013] [Indexed: 01/05/2023]
|
76
|
Veronesi M, Romeo E, Lambruschini C, Piomelli D, Bandiera T, Scarpelli R, Garau G, Dalvit C. Fluorine NMR-Based Screening on Cell Membrane Extracts. ChemMedChem 2013; 9:286-9. [DOI: 10.1002/cmdc.201300438] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Indexed: 11/12/2022]
|
77
|
Chintapalli SV, Illingworth CJR, Upton GJG, Sacquin-Mora S, Reeves PJ, Mohammedali HS, Reynolds CA. Assessing the effect of dynamics on the closed-loop protein-folding hypothesis. J R Soc Interface 2013; 11:20130935. [PMID: 24258160 PMCID: PMC3869168 DOI: 10.1098/rsif.2013.0935] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The closed-loop (loop-n-lock) hypothesis of protein folding suggests that loops of about 25 residues, closed through interactions between the loop ends (locks), play an important role in protein structure. Coarse-grain elastic network simulations, and examination of loop lengths in a diverse set of proteins, each supports a bias towards loops of close to 25 residues in length between residues of high stability. Previous studies have established a correlation between total contact distance (TCD), a metric of sequence distances between contacting residues (cf. contact order), and the log-folding rate of a protein. In a set of 43 proteins, we identify an improved correlation (r2 = 0.76), when the metric is restricted to residues contacting the locks, compared to the equivalent result when all residues are considered (r2 = 0.65). This provides qualified support for the hypothesis, albeit with an increased emphasis upon the importance of a much larger set of residues surrounding the locks. Evidence of a similar-sized protein core/extended nucleus (with significant overlap) was obtained from TCD calculations in which residues were successively eliminated according to their hydrophobicity and connectivity, and from molecular dynamics simulations. Our results suggest that while folding is determined by a subset of residues that can be predicted by application of the closed-loop hypothesis, the original hypothesis is too simplistic; efficient protein folding is dependent on a considerably larger subset of residues than those involved in lock formation.
Collapse
Affiliation(s)
- Sree V Chintapalli
- School of Biological Sciences, University of Essex, , Wivenhoe Park, Colchester CO4 3SQ, UK
| | | | | | | | | | | | | |
Collapse
|
78
|
Bacterial-based membrane protein production. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:1739-49. [PMID: 24200679 DOI: 10.1016/j.bbamcr.2013.10.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/20/2013] [Accepted: 10/29/2013] [Indexed: 01/08/2023]
Abstract
Escherichia coli is by far the most widely used bacterial host for the production of membrane proteins. Usually, different strains, culture conditions and production regimes are screened for to design the optimal production process. However, these E. coli-based screening approaches often do not result in satisfactory membrane protein production yields. Recently, it has been shown that (i) E. coli strains with strongly improved membrane protein production characteristics can be engineered or selected for, (ii) many membrane proteins can be efficiently produced in E. coli-based cell-free systems, (iii) bacteria other than E. coli can be used for the efficient production of membrane proteins, and, (iv) membrane protein variants that retain functionality but are produced at higher yields than the wild-type protein can be engineered or selected for. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
Collapse
|
79
|
Bertheleme N, Chae PS, Singh S, Mossakowska D, Hann MM, Smith KJ, Hubbard JA, Dowell SJ, Byrne B. Unlocking the secrets of the gatekeeper: Methods for stabilizing and crystallizing GPCRs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2583-91. [DOI: 10.1016/j.bbamem.2013.07.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 07/01/2013] [Accepted: 07/08/2013] [Indexed: 02/07/2023]
|
80
|
Abdul-Hussein S, Andréll J, Tate CG. Thermostabilisation of the serotonin transporter in a cocaine-bound conformation. J Mol Biol 2013; 425:2198-207. [PMID: 23706649 PMCID: PMC3678023 DOI: 10.1016/j.jmb.2013.03.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 02/25/2013] [Accepted: 03/12/2013] [Indexed: 11/15/2022]
Abstract
Structure determination of mammalian integral membrane proteins is challenging due to their instability upon detergent solubilisation and purification. Recent successes in the structure determination of G-protein-coupled receptors (GPCRs) resulted from the development of GPCR-specific protein engineering strategies. One of these, conformational thermostabilisation, could in theory facilitate structure determination of other membrane proteins by improving their tolerance to detergents and locking them in a specific conformation. We have therefore used this approach on the cocaine-sensitive rat serotonin transporter (SERT). Out of a panel of 554 point mutants throughout SERT, 10 were found to improve its thermostability. The most stabilising mutations were combined to make the thermostabilised mutants SAH6 (L99A + G278A + A505L) and SAH7 (L405A + P499A + A505L) that were more stable than SERT by 18 °C and 16 °C, respectively. Inhibitor binding assays showed that both of the thermostabilised SERT mutants bound [125I]RTI55 (β-CIT) with affinity similar to that of the wild-type transporter, although cocaine bound with increased affinity (17- to 56-fold) whilst ibogaine, imipramine and paroxetine all bound with lower affinity (up to 90-fold). Neither SAH6 nor SAH7 was capable of transporting [3H]serotonin into HEK293 cell lines stably expressing the mutants, although serotonin bound to them with an apparent Ki of 155 μM or 82 μM, respectively. These data combined suggest that SAH6 and SAH7 are thermostabilised in a specific cocaine-bound conformation, making them promising candidates for crystallisation. Conformational thermostabilisation is thus equally applicable to membrane proteins that are transporters in addition to those that are GPCRs.
Collapse
|
81
|
Hollenstein K, Kean J, Bortolato A, Cheng RKY, Doré AS, Jazayeri A, Cooke RM, Weir M, Marshall FH. Structure of class B GPCR corticotropin-releasing factor receptor 1. Nature 2013; 499:438-43. [PMID: 23863939 DOI: 10.1038/nature12357] [Citation(s) in RCA: 320] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 06/07/2013] [Indexed: 12/17/2022]
Abstract
Structural analysis of class B G-protein-coupled receptors (GPCRs), cell-surface proteins that respond to peptide hormones, has been restricted to the amino-terminal extracellular domain, thus providing little understanding of the membrane-spanning signal transduction domain. The corticotropin-releasing factor receptor type 1 is a class B receptor which mediates the response to stress and has been considered a drug target for depression and anxiety. Here we report the crystal structure of the transmembrane domain of the human corticotropin-releasing factor receptor type 1 in complex with the small-molecule antagonist CP-376395. The structure provides detailed insight into the architecture of class B receptors. Atomic details of the interactions of the receptor with the non-peptide ligand that binds deep within the receptor are described. This structure provides a model for all class B GPCRs and may aid in the design of new small-molecule drugs for diseases of brain and metabolism.
Collapse
Affiliation(s)
- Kaspar Hollenstein
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City AL7 3AX, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
82
|
Maeda S, Schertler GFX. Production of GPCR and GPCR complexes for structure determination. Curr Opin Struct Biol 2013; 23:381-92. [PMID: 23707225 DOI: 10.1016/j.sbi.2013.04.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 04/11/2013] [Accepted: 04/11/2013] [Indexed: 01/12/2023]
Abstract
Since the first high-resolution structure of the beta 2 adrenergic receptor (b2AR) in 2007, we have seen a growing number of G-protein-coupled receptor (GPCR) structures coming to the repertory, providing a significant progress in our understanding of the structural basis of their function. This has been achieved by the interdisciplinary collaborative work between scientists with various expertise and the development of new methodologies as well as combining and optimizing existing techniques.
Collapse
Affiliation(s)
- Shoji Maeda
- Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | | |
Collapse
|
83
|
Transient and stable expression of the neurotensin receptor NTS1: a comparison of the baculovirus-insect cell and the T-REx-293 expression systems. PLoS One 2013; 8:e63679. [PMID: 23696845 PMCID: PMC3656039 DOI: 10.1371/journal.pone.0063679] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 04/05/2013] [Indexed: 01/06/2023] Open
Abstract
Nowadays, baculovirus-infected insect cells and tetracycline-inducible mammalian cell lines (T-REx-293) are intensively used for G protein-coupled receptor (GPCR) production for crystallography purposes. Here we constructed a suspension T-REx-293 cell line to stably express an engineered neurotensin receptor 1 (NTS1) mutant and we quantitatively compared this cell line with the transient baculovirus-insect cell system throughout a milligram-scale NTS1 expression and purification process. The two systems were comparable with respect to functional NTS1 expression levels and receptor binding affinity for the agonist [3H] neurotensin. However, NTS1 surface display on T-REx-293 cells determined by radio-ligand binding assays was 2.8 fold higher than that on insect cells. This work demonstrates two approaches for preparing milligram quantities of purified NTS1 suitable for structural studies and provides useful input to users in choosing and optimizing an appropriate expression host for other GPCRs.
Collapse
|
84
|
Scott DJ, Kummer L, Tremmel D, Plückthun A. Stabilizing membrane proteins through protein engineering. Curr Opin Chem Biol 2013; 17:427-35. [PMID: 23639904 DOI: 10.1016/j.cbpa.2013.04.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 04/03/2013] [Accepted: 04/05/2013] [Indexed: 12/18/2022]
Abstract
Integral membrane proteins (IMPs) are crucial components of all cells but are difficult to study in vitro because they are generally unstable when removed from their native membranes using detergents. Despite the major biomedical relevance of IMPs, less than 1% of Protein Data Bank (PDB) entries are IMP structures, reflecting the technical gap between studies of soluble proteins compared to IMPs. Stability can be engineered into IMPs by inserting stabilizing mutations, thereby generating proteins that can be successfully applied to biochemical and structural studies when solubilized in detergent micelles. The identification of stabilizing mutations is not trivial, and this review will focus on the methods that have been used to identify stabilized membrane proteins, including alanine scanning and screening, directed evolution and computational design.
Collapse
Affiliation(s)
- Daniel J Scott
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria 3010, Australia
| | | | | | | |
Collapse
|
85
|
Christopher JA, Brown J, Doré AS, Errey JC, Koglin M, Marshall FH, Myszka DG, Rich RL, Tate CG, Tehan B, Warne T, Congreve M. Biophysical fragment screening of the β1-adrenergic receptor: identification of high affinity arylpiperazine leads using structure-based drug design. J Med Chem 2013; 56:3446-55. [PMID: 23517028 PMCID: PMC3654563 DOI: 10.1021/jm400140q] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Biophysical fragment screening of a thermostabilized β1-adrenergic receptor (β1AR) using surface plasmon resonance (SPR) enabled the identification of moderate affinity, high ligand efficiency (LE) arylpiperazine hits 7 and 8. Subsequent hit to lead follow-up confirmed the activity of the chemotype, and a structure-based design approach using protein-ligand crystal structures of the β1AR resulted in the identification of several fragments that bound with higher affinity, including indole 19 and quinoline 20. In the first example of GPCR crystallography with ligands derived from fragment screening, structures of the stabilized β1AR complexed with 19 and 20 were determined at resolutions of 2.8 and 2.7 Å, respectively.
Collapse
Affiliation(s)
- John A Christopher
- Heptares Therapeutics Ltd. , BioPark, Welwyn Garden City, Hertfordshire, AL7 3AX, U.K.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
86
|
Topiol S. X-ray structural information of GPCRs in drug design: what are the limitations and where do we go? Expert Opin Drug Discov 2013; 8:607-20. [PMID: 23537065 DOI: 10.1517/17460441.2013.783815] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
INTRODUCTION In 2007, the X-ray structural determination of non-rhodopsin G-Protein coupled receptors (GPCRs), considered the most extensively targeted protein class for marketed drugs, commenced. With the relatively rapid availability of additional structures, an assessment of the progression made is needed in addition to the assessment of the understandings gleaned, deployment successes and forthcoming prospects. AREAS COVERED The author reviews the approaches and tools that have made it possible to determine the three dimensional structures of GPCRs using X-ray crystallography. Furthermore, the author describes the methods suited for crystallization of membrane bound GPCR proteins including the lipidic cubic phase and various protein modification approaches. The author also provides highlights, from the literature, of the structures determined to date including targets solved, the nature of the content provided (such as selectivity, activating vs. inactivating determinants) and how these structural features relate to drug design strategies. EXPERT OPINION The GPCR X-ray structures that have been so far determined have yielded significant information. This has presented dramatic evidence concerning their ability to impact the discovery of compounds through their action as traditional, orthosteric modulators. It is, however, noted that more challenging design strategies, such as identifying biased agonists and the use of sites remote from the orthosteric site for allosteric modulation, are still in their infancy.
Collapse
Affiliation(s)
- Sid Topiol
- 3D-2Drug LLC, PO Box 184, Fair Lawn, NJ 07410, USA.
| |
Collapse
|
87
|
Rapid screening of membrane protein expression in transiently transfected insect cells. Protein Expr Purif 2013; 88:134-42. [DOI: 10.1016/j.pep.2012.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 12/07/2012] [Accepted: 12/08/2012] [Indexed: 01/09/2023]
|
88
|
Bennett KA, Tehan B, Lebon G, Tate CG, Weir M, Marshall FH, Langmead CJ. Pharmacology and structure of isolated conformations of the adenosine A₂A receptor define ligand efficacy. Mol Pharmacol 2013; 83:949-58. [PMID: 23429888 DOI: 10.1124/mol.112.084509] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using isolated receptor conformations crystal structures of the adenosine A₂A receptor have been solved in active and inactive states. Studying the change in affinity of ligands at these conformations allowed qualitative prediction of compound efficacy in vitro in a system-independent manner. Agonist 5'-N-ethylcarboxamidoadenosine displayed a clear preference to bind to the active state receptor; inverse agonists (xanthine amine congener, ZM241385, SCH58261, and preladenant) bound preferentially to the inactive state, whereas neutral antagonists (theophylline, caffeine, and istradefylline) demonstrated equal affinity for active and inactive states. Ligand docking into the known crystal structures of the A₂A receptor rationalized the pharmacology observed; inverse agonists, unlike neutral antagonists, cannot be accommodated within the agonist-binding site of the receptor. The availability of isolated receptor conformations opens the door to the concept of "reverse pharmacology" whereby the functional pharmacology of ligands can be characterized in a system-independent manner by their affinity for a pair (or set) of G protein-coupled receptor conformations.
Collapse
Affiliation(s)
- Kirstie A Bennett
- Heptares Therapeutics Ltd, Welwyn Garden City, Hertfordshire, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
89
|
Direct Molecular Evolution of Detergent-Stable G Protein-Coupled Receptors Using Polymer Encapsulated Cells. J Mol Biol 2013; 425:662-77. [DOI: 10.1016/j.jmb.2012.11.015] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/05/2012] [Accepted: 11/06/2012] [Indexed: 11/18/2022]
|
90
|
Shibata Y, Gvozdenovic-Jeremic J, Love J, Kloss B, White JF, Grisshammer R, Tate CG. Optimising the combination of thermostabilising mutations in the neurotensin receptor for structure determination. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1293-301. [PMID: 23337476 DOI: 10.1016/j.bbamem.2013.01.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 10/27/2022]
Abstract
Conformational thermostabilisation of G protein-coupled receptors is a successful approach for their structure determination. We have recently determined the structure of a thermostabilised neurotensin receptor NTS1 in complex with its peptide agonist and here we describe the strategy for the identification and combination of the 6 thermostabilising mutations essential for crystallisation. First, thermostability assays were performed on a panel of 340 detergent-solubilised Ala/Leu NTS1 mutants and the best 16 thermostabilising mutations were identified. These mutations were combined pair-wise in nearly all combinations (119 out of a possible 120 combinations) and each mutant was expressed and its thermostability was experimentally determined. A theoretical stability score was calculated from the sum of the stabilities measured for each double mutant and applied to develop 24 triple mutants, which in turn led to the construction of 14 quadruple mutants. Use of the thermostability data for the double mutants to predict further mutant combinations resulted in a greater percentage of the triple and quadruple mutants showing improved thermostability than if only the thermostability data for the single mutations was considered. The best quadruple mutant (NTS1-Nag36k) was further improved by including an additional 2 mutations (resulting in NTS1-GW5) that were identified from a complete Ala/Leu scan of Nag36k by testing the thermostability of the mutants in situ in whole bacteria. NTS1-GW5 had excellent stability in short chain detergents and could be readily purified as a homogenous sample that ultimately allowed crystallisation and structure determination.
Collapse
Affiliation(s)
- Yoko Shibata
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | | | | | | | | | | | | |
Collapse
|
91
|
Directed evolution of G-protein-coupled receptors for high functional expression and detergent stability. Methods Enzymol 2013; 520:67-97. [PMID: 23332696 DOI: 10.1016/b978-0-12-391861-1.00004-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
G-protein-coupled receptors (GPCRs) are cell-surface receptors exhibiting a key role in cellular signal transduction processes, thus making them pharmacologically highly relevant target proteins. However, the molecular mechanisms driving receptor activation by ligand binding and signal transduction are poorly understood, since as integral membrane proteins, most GPCRs are very challenging for functional and structural studies. The biophysical properties of natural GPCRs, usually required by the cell in only low amounts, support their functionality in the lipid bilayer but are insufficient for high-level recombinant overexpression and stability in detergent solution. Current structural information about GPCRs is thus limited to a subset of GPCRs with either intrinsically favorable or properly improved biophysical behavior. Recently, directed protein evolution techniques for functional expression and detergent stability have been developed to increase the accessibility of GPCRs for functional and structural studies. Directed evolution does not rely on any preconceived notion of what might be limiting biophysical properties. By random mutagenesis combined with a high-throughput screening and selection system, directed protein evolution has the power to efficiently isolate rare phenotypes and thus contribute to the elucidation of the stability-determining factors, in addition to solving the practical problem of creating stable GPCRs. In the current chapter, protocols for generation of genetic diversity within GPCRs and selection are provided and discussed.
Collapse
|
92
|
Wiktor M, Morin S, Sass HJ, Kebbel F, Grzesiek S. Biophysical and structural investigation of bacterially expressed and engineered CCR5, a G protein-coupled receptor. JOURNAL OF BIOMOLECULAR NMR 2013; 55:79-95. [PMID: 23229639 DOI: 10.1007/s10858-012-9688-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 11/22/2012] [Indexed: 06/01/2023]
Abstract
The chemokine receptor CCR5 belongs to the class of G protein-coupled receptors. Besides its role in leukocyte trafficking, it is also the major HIV-1 coreceptor and hence a target for HIV-1 entry inhibitors. Here, we report Escherichia coli expression and a broad range of biophysical studies on E. coli-produced CCR5. After systematic screening and optimization, we obtained 10 mg of purified, detergent-solubilized, folded CCR5 from 1L culture in a triply isotope-labeled ((2)H/(15)N/(13)C) minimal medium. Thus the material is suitable for NMR spectroscopic studies. The expected α-helical secondary structure content is confirmed by circular dichroism spectroscopy. The solubilized CCR5 is monodisperse and homogeneous as judged by transmission electron microscopy. Interactions of CCR5 with its ligands, RANTES and MIP-1β were assessed by surface plasmon resonance yielding K(D) values in the nanomolar range. Using size exclusion chromatography, stable monomeric CCR5 could be isolated. We show that cysteine residues affect both the yield and oligomer distribution of CCR5. HSQC spectra suggest that the transmembrane domains of CCR5 are in equilibrium between several conformations. In addition we present a model of CCR5 based on the crystal structure of CXCR4 as a starting point for protein engineering.
Collapse
Affiliation(s)
- Maciej Wiktor
- Focal Area Structural Biology and Biophysics, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | | | | | | | | |
Collapse
|
93
|
Abstract
G protein-coupled receptors (GPCR) are the largest family of integral membrane proteins found in the plasma membrane of mammalian cells. GPCR respond to a large variety of ligands such as amines, lipids, hormones and amino-acids, which are involved in inter-cellular signalling events in a multitude of physiological and pathological processes. GPCRs are therefore key regulators of signal transduction by which cells respond to variations in their environment. During the last five years, striking progress has been made to solve high-resolution structure of GPCR. The most recent successes are the structures of the β(1) and β(2) adrenoreceptors and the adenosine A(2A) receptor bound to a variety of agonists. Most importantly, the structure of the β(2) adrenoreceptor in complex with a trimeric G protein, Gs, was recently reported. This review will present an overview of the X-ray structure determination of the GPCR and of their activation mechanism.
Collapse
Affiliation(s)
- Guillaume Lebon
- Département de Pharmacologie Moléculaire, Universités de Montpellier I et II, Montpellier, France.
| | | |
Collapse
|
94
|
Banères JL, Mouillac B. [Handling G-protein-coupled receptors: expression, purification and in vitro stabilization]. Med Sci (Paris) 2012; 28:837-44. [PMID: 23067414 DOI: 10.1051/medsci/20122810011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Among the different classes of integral membrane proteins, G protein-coupled receptors (GPCR) constitute the largest family. They are involved in most essential physiological functions and particularly play a key role in cell-to-cell communication and sensory signal transduction. They represent targets for approximately 30% of currently marketed drugs. In order to better understand their functioning, define their tridimensional structure and develop novel selective and efficient therapeutic compounds, it is crucial to purify these proteins for a full characterization. However, this biochemical step is not trivial since GPCR are present in membranes at very low levels and they require detergents to be extracted from their natural lipid environment and be handled as functional proteins. No universal strategy for GPCR production, purification and stabilization is currently available; each single GPCR possesses a unique set of physicochemical characteristics, preference for some detergents upon solubilization and specific conditions for purification. During the last decade, major breakthroughs regarding overexpression, purification and above all GPCR stabilization, thanks to amphipols and nanodiscs, opened very exciting perspectives for structural and dynamic investigations of these membrane proteins. The aim of this chapter is to provide an overview of the different aspects of GPCR handling.
Collapse
Affiliation(s)
- Jean-Louis Banères
- Institut des biomolécules Max Mousseron, faculté de pharmacie, Montpellier, France
| | | |
Collapse
|
95
|
White JF, Noinaj N, Shibata Y, Love J, Kloss B, Xu F, Gvozdenovic-Jeremic J, Shah P, Shiloach J, Tate CG, Grisshammer R. Structure of the agonist-bound neurotensin receptor. Nature 2012; 490:508-13. [PMID: 23051748 PMCID: PMC3482300 DOI: 10.1038/nature11558] [Citation(s) in RCA: 393] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 09/11/2012] [Indexed: 12/11/2022]
Abstract
Neurotensin (NT) is a 13 amino acid peptide that functions as both a neurotransmitter and a hormone through activation of the neurotensin receptor NTS1, a G protein-coupled receptor (GPCR). In the brain, NT modulates activity of dopaminergic systems, opioid-independent analgesia, and the inhibition of food intake, and in the gut NT regulates a range of digestive processes. Here we present the structure at 2.8 Å resolution of NTS1 in an active-like state, bound to NT8-13, the C terminal portion of NT responsible for agonist-induced activation of the receptor. The peptide agonist binds to NTS1 in an extended conformation nearly perpendicular to the membrane plane with the C-terminus oriented towards the receptor core. Our findings provide the first insight into the binding mode of a peptide agonist to a GPCR and may support the development of non-peptide ligands that could be useful in the treatment of neurological disorders, cancer and obesity.
Collapse
Affiliation(s)
- Jim F White
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Stabilization of functional recombinant cannabinoid receptor CB(2) in detergent micelles and lipid bilayers. PLoS One 2012; 7:e46290. [PMID: 23056277 PMCID: PMC3463599 DOI: 10.1371/journal.pone.0046290] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 08/28/2012] [Indexed: 11/19/2022] Open
Abstract
Elucidation of the molecular mechanisms of activation of G protein-coupled receptors (GPCRs) is among the most challenging tasks for modern membrane biology. For studies by high resolution analytical methods, these integral membrane receptors have to be expressed in large quantities, solubilized from cell membranes and purified in detergent micelles, which may result in a severe destabilization and a loss of function. Here, we report insights into differential effects of detergents, lipids and cannabinoid ligands on stability of the recombinant cannabinoid receptor CB2, and provide guidelines for preparation and handling of the fully functional receptor suitable for a wide array of downstream applications. While we previously described the expression in Escherichia coli, purification and liposome-reconstitution of multi-milligram quantities of CB2, here we report an efficient stabilization of the recombinant receptor in micelles - crucial for functional and structural characterization. The effects of detergents, lipids and specific ligands on structural stability of CB2 were assessed by studying activation of G proteins by the purified receptor reconstituted into liposomes. Functional structure of the ligand binding pocket of the receptor was confirmed by binding of 2H-labeled ligand measured by solid-state NMR. We demonstrate that a concerted action of an anionic cholesterol derivative, cholesteryl hemisuccinate (CHS) and high affinity cannabinoid ligands CP-55,940 or SR-144,528 are required for efficient stabilization of the functional fold of CB2 in dodecyl maltoside (DDM)/CHAPS detergent solutions. Similar to CHS, the negatively charged phospholipids with the serine headgroup (PS) exerted significant stabilizing effects in micelles while uncharged phospholipids were not effective. The purified CB2 reconstituted into lipid bilayers retained functionality for up to several weeks enabling high resolution structural studies of this GPCR at physiologically relevant conditions.
Collapse
|
97
|
Abstract
The number of structures of integral membrane proteins from higher eukaryotes is steadily increasing due to a number of innovative protein engineering and crystallization strategies devised over the last few years. However, it is sobering to reflect that these structures represent only a tiny proportion of the total number of membrane proteins encoded by a mammalian genome. In addition, the structures determined to date are of the most tractable membrane proteins, i.e., those that are expressed functionally and to high levels in yeast or in insect cells using the baculovirus expression system. However, some membrane proteins that are expressed inefficiently in these systems can be produced at sufficiently high levels in mammalian cells to allow structure determination. Mammalian expression systems are an under-used resource in structural biology and represent an effective way to produce fully functional membrane proteins for structural studies. This review will discuss examples of vertebrate membrane protein overexpression in mammalian cells using a variety of viral, constitutive or inducible expression systems.
Collapse
Affiliation(s)
- Juni Andréll
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | | |
Collapse
|
98
|
Caffrey M, Li D, Dukkipati A. Membrane protein structure determination using crystallography and lipidic mesophases: recent advances and successes. Biochemistry 2012; 51:6266-88. [PMID: 22783824 DOI: 10.1021/bi300010w] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The crystal structure of the β(2)-adrenergic receptor in complex with an agonist and its cognate G protein has just recently been determined. It is now possible to explore in molecular detail the means by which this paradigmatic transmembrane receptor binds agonist, communicates the impulse or signaling event across the membrane, and sets in motion a series of G protein-directed intracellular responses. The structure was determined using crystals of the ternary complex grown in a rationally designed lipidic mesophase by the so-called in meso method. The method is proving to be particularly useful in the G protein-coupled receptor field where the structures of 13 distinct receptor types have been determined in the past 5 years. In addition to receptors, the method has proven to be useful with a wide variety of integral membrane protein classes that include bacterial and eukaryotic rhodopsins, light-harvesting complex II (LHII), photosynthetic reaction centers, cytochrome oxidases, β-barrels, an exchanger, and an integral membrane peptide. This attests to the versatility and range of the method and supports the view that the in meso method should be included in the arsenal of the serious membrane structural biologist. For this to happen, however, the reluctance to adopt it attributable, in part, to the anticipated difficulties associated with handling the sticky, viscous cubic mesophase in which crystals grow must be overcome. Harvesting and collecting diffraction data with the mesophase-grown crystals are also viewed with some trepidation. It is acknowledged that there are challenges associated with the method. Over the years, we have endeavored to establish how the method works at a molecular level and to make it user-friendly. To these ends, tools for handling the mesophase in the pico- to nanoliter volume range have been developed for highly efficient crystallization screening in manual and robotic modes. Methods have been implemented for evaluating the functional activity of membrane proteins reconstituted into the bilayer of the cubic phase as a prelude to crystallogenesis. Glass crystallization plates that provide unparalleled optical quality and sensitivity to nascent crystals have been built. Lipid and precipitant screens have been designed for a more rational approach to crystallogenesis such that the method can now be applied to an even wider variety of membrane protein types. In this work, these assorted advances are outlined along with a summary of the membrane proteins that have yielded to the method. The prospects for and the challenges that must be overcome to further develop the method are described.
Collapse
Affiliation(s)
- Martin Caffrey
- Membrane Structural and Functional Biology Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
| | | | | |
Collapse
|
99
|
G-protein-coupled receptor dynamics: dimerization and activation models compared with experiment. Biochem Soc Trans 2012; 40:394-9. [PMID: 22435818 DOI: 10.1042/bst20110755] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Our previously derived models of the active state of the β2-adrenergic receptor are compared with recently published X-ray crystallographic structures of activated GPCRs (G-protein-coupled receptors). These molecular dynamics-based models using experimental data derived from biophysical experiments on activation were used to restrain the receptor to an active state that gave high enrichment for agonists in virtual screening. The β2-adrenergic receptor active model and X-ray structures are in good agreement over both the transmembrane region and the orthosteric binding site, although in some regions the active model is more similar to the active rhodopsin X-ray structures. The general features of the microswitches were well reproduced, but with minor differences, partly because of the unexpected X-ray results for the rotamer toggle switch. In addition, most of the interacting residues between the receptor and the G-protein were identified. This analysis of the modelling has also given important additional insight into GPCR dimerization: re-analysis of results on photoaffinity analogues of rhodopsin provided additional evidence that TM4 (transmembrane helix 4) resides at the dimer interface and that ligands such as bivalent ligands may pass between the mobile helices. A comparison, and discussion, is also carried out between the use of implicit and explicit solvent for active-state modelling.
Collapse
|
100
|
A crystal clear solution for determining G-protein-coupled receptor structures. Trends Biochem Sci 2012; 37:343-52. [PMID: 22784935 DOI: 10.1016/j.tibs.2012.06.003] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 05/31/2012] [Accepted: 06/05/2012] [Indexed: 11/21/2022]
Abstract
G-protein-coupled receptors (GPCRs) are medically important membrane proteins that are targeted by over 30% of small molecule drugs. At the time of writing, 15 unique GPCR structures have been determined, with 77 structures deposited in the PDB database, which offers new opportunities for drug development and for understanding the molecular mechanisms of GPCR activation. Many different factors have contributed to this success, but if there is one single factor that can be singled out as the foundation for producing well-diffracting GPCR crystals, it is the stabilisation of the detergent-solubilised receptor-ligand complex. This review will focus predominantly on one of the successful strategies for the stabilisation of GPCRs, namely the thermostabilisation of GPCRs using systematic mutagenesis coupled with thermostability assays. Structures of thermostabilised GPCRs bound to a wide variety of ligands have been determined, which has led to an understanding of ligand specificity; why some ligands act as agonists as opposed to partial or inverse agonists; and the structural basis for receptor activation.
Collapse
|