151
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van der Westhuizen ET, Valant C, Sexton PM, Christopoulos A. Endogenous Allosteric Modulators of G Protein–Coupled Receptors. J Pharmacol Exp Ther 2015; 353:246-60. [DOI: 10.1124/jpet.114.221606] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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152
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Chakraborty H, Chattopadhyay A. Excitements and challenges in GPCR oligomerization: molecular insight from FRET. ACS Chem Neurosci 2015; 6:199-206. [PMID: 25363209 DOI: 10.1021/cn500231d] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest family of proteins involved in signal transduction across cell membranes, and they represent major drug targets in all clinical areas. Oligomerization of GPCRs and its implications in drug discovery constitute an exciting area in contemporary biology. In this Review, we have highlighted the application of fluorescence resonance energy transfer (FRET) in exploring GPCR oligomerization, with special emphasis on possible pitfalls and experimental complications involved. Based on FRET photophysics, we discuss some of the possible complications, and recommend that FRET results in complex cellular environments should be interpreted with caution. Although both hetero- and homo-FRET are used in measurements of GPCR oligomerization, we suggest that homo-FRET enjoys certain advantages over hetero-FRET. Given the seminal role of GPCRs as current drug targets, we envision that methodological progress in studying GPCR oligomerization would result in better therapeutic strategies.
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Affiliation(s)
- Hirak Chakraborty
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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153
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Prasanna X, Chattopadhyay A, Sengupta D. Role of lipid-mediated effects in β₂-adrenergic receptor dimerization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 842:247-61. [PMID: 25408348 DOI: 10.1007/978-3-319-11280-0_16] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Xavier Prasanna
- CSIR-National Chemical Laboratory, Council of Scientific and Industrial Research, Dr. Homi Bhabha Road, Pune, 411 008, India
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154
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Chattopadhyay A, Rao BD, Jafurulla M. Solubilization of G Protein-Coupled Receptors. Methods Enzymol 2015; 557:117-34. [DOI: 10.1016/bs.mie.2015.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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155
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Blocker KM, Britton ZT, Naranjo AN, McNeely PM, Young CL, Robinson AS. Recombinant G Protein-Coupled Receptor Expression in Saccharomyces cerevisiae for Protein Characterization. Methods Enzymol 2015; 556:165-83. [DOI: 10.1016/bs.mie.2014.12.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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156
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On the modularity of the intrinsic flexibility of the µ opioid receptor: a computational study. PLoS One 2014; 9:e115856. [PMID: 25549261 PMCID: PMC4280117 DOI: 10.1371/journal.pone.0115856] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 12/01/2014] [Indexed: 11/19/2022] Open
Abstract
The µ opioid receptor (µOR), the principal target to control pain, belongs to the G protein-coupled receptors (GPCRs) family, one of the most highlighted protein families due to their importance as therapeutic targets. The conformational flexibility of GPCRs is one of their essential characteristics as they take part in ligand recognition and subsequent activation or inactivation mechanisms. It is assessed that the intrinsic mechanical properties of the µOR, more specifically its particular flexibility behavior, would facilitate the accomplishment of specific biological functions, at least in their first steps, even in the absence of a ligand or any chemical species usually present in its biological environment. The study of the mechanical properties of the µOR would thus bring some indications regarding the highly efficient ability of the µOR to transduce cellular message. We therefore investigate the intrinsic flexibility of the µOR in its apo-form using all-atom Molecular Dynamics simulations at the sub-microsecond time scale. We particularly consider the µOR embedded in a simplified membrane model without specific ions, particular lipids, such as cholesterol moieties, or any other chemical species that could affect the flexibility of the µOR. Our analyses highlighted an important local effect due to the various bendability of the helices resulting in a diversity of shape and volume sizes adopted by the µOR binding site. Such property explains why the µOR can interact with ligands presenting highly diverse structural geometry. By investigating the topology of the µOR binding site, a conformational global effect is depicted: the correlation between the motional modes of the extra- and intracellular parts of µOR on one hand, along with a clear rigidity of the central µOR domain on the other hand. Our results show how the modularity of the µOR flexibility is related to its pre-ability to activate and to present a basal activity.
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157
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Shahane G, Parsania C, Sengupta D, Joshi M. Molecular insights into the dynamics of pharmacogenetically important N-terminal variants of the human β2-adrenergic receptor. PLoS Comput Biol 2014; 10:e1004006. [PMID: 25501358 PMCID: PMC4263363 DOI: 10.1371/journal.pcbi.1004006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 10/28/2014] [Indexed: 12/27/2022] Open
Abstract
The human β2-adrenergic receptor (β2AR), a member of the G-protein coupled receptor (GPCR) family, is expressed in bronchial smooth muscle cells. Upon activation by agonists, β2AR causes bronchodilation and relief in asthma patients. The N-terminal polymorphism of β2AR at the 16th position, Arg16Gly, has warranted a lot of attention since it is linked to variations in response to albuterol (agonist) treatment. Although the β2AR is one of the well-studied GPCRs, the N-terminus which harbors this mutation, is absent in all available experimental structures. The goal of this work was to study the molecular level differences between the N-terminal variants using structural modeling and atomistic molecular dynamics simulations. Our simulations reveal that the N-terminal region of the Arg variant shows greater dynamics than the Gly variant, leading to differential placement. Further, the position and dynamics of the N-terminal region, further, affects the ligand binding-site accessibility. Interestingly, long-range effects are also seen at the ligand binding site, which is marginally larger in the Gly as compared to the Arg variant resulting in the preferential docking of albuterol to the Gly variant. This study thus reveals key differences between the variants providing a molecular framework towards understanding the variable drug response in asthma patients. The human β2-adrenergic receptor (β2AR) is an important member of the GPCR family and a mutation at the 16th position, Arg16Gly, is commonly found in the population. This variation in asthma patients is linked to differential (good/bad) response to the drug albuterol, an agonist of the β2AR. To date, the coordinates of the N-terminal residues harboring the 16th position mutation have not been resolved. In our study we sought to glean insights into the dynamics of the variants that could address the differential response to albuterol. We used knowledge from class A GPCRs to build the N-terminal region of β2AR variants in conjunction with the available structure of the inactive receptor. This was followed by atomistic simulations in triplicate totaling to a sampling of 6 µs. We observe that the N-terminal region of the Arg variant is more dynamic than the Gly variant. Amongst the various differences between the variants, we observe long-range effects at the binding site leading to preferential docking of albuterol to the Gly variant. Our work is a first step to unravel the molecular mechanism linking the Arg16Gly variation to the differential response to albuterol in asthma patients.
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Affiliation(s)
| | | | - Durba Sengupta
- CSIR-National Chemical Laboratory, Pune, India
- * E-mail: (DS); (MJ)
| | - Manali Joshi
- Bioinformatics Center, University of Pune, Pune, India
- * E-mail: (DS); (MJ)
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158
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Prasanna X, Chattopadhyay A, Sengupta D. Cholesterol modulates the dimer interface of the β₂-adrenergic receptor via cholesterol occupancy sites. Biophys J 2014; 106:1290-300. [PMID: 24655504 DOI: 10.1016/j.bpj.2014.02.002] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 02/01/2014] [Accepted: 02/03/2014] [Indexed: 11/26/2022] Open
Abstract
The β2-adrenergic receptor is an important member of the G-protein-coupled receptor (GPCR) superfamily, whose stability and function are modulated by membrane cholesterol. The recent high-resolution crystal structure of the β2-adrenergic receptor revealed the presence of possible cholesterol-binding sites in the receptor. However, the functional relevance of cholesterol binding to the receptor remains unexplored. We used MARTINI coarse-grained molecular-dynamics simulations to explore dimerization of the β2-adrenergic receptor in lipid bilayers containing cholesterol. A novel (to our knowledge) aspect of our results is that receptor dimerization is modulated by membrane cholesterol. We show that cholesterol binds to transmembrane helix IV, and cholesterol occupancy at this site restricts its involvement at the dimer interface. With increasing cholesterol concentration, an increased presence of transmembrane helices I and II, but a reduced presence of transmembrane helix IV, is observed at the dimer interface. To our knowledge, this study is one of the first to explore the correlation between cholesterol occupancy and GPCR organization. Our results indicate that dimer plasticity is relevant not just as an organizational principle but also as a subtle regulatory principle for GPCR function. We believe these results constitute an important step toward designing better drugs for GPCR dimer targets.
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159
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Adamson RJ, Watts A. Kinetics of the early events of GPCR signalling. FEBS Lett 2014; 588:4701-7. [PMID: 25447525 PMCID: PMC4266533 DOI: 10.1016/j.febslet.2014.10.043] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/10/2014] [Accepted: 10/27/2014] [Indexed: 11/28/2022]
Abstract
Little is known of the kinetics of interactions between GPCRs and their signalling partners. NTS1 binds Gαi1 and Gαs with affinities of 15 ± 6 nM and 31 ± 18 nM (SE), respectively. This SPR assay may be applicable to multiple partners in the signalling cascade. We provide the first direct evidence for GPCR-G protein coupling in nanodiscs.
Neurotensin receptor type 1 (NTS1) is a G protein-coupled receptor (GPCR) that affects cellular responses by initiating a cascade of interactions through G proteins. The kinetic details for these interactions are not well-known. Here, NTS1-nanodisc-Gαs and Gαi1 interactions were studied. The binding affinities of Gαi1 and Gαs to NTS1 were directly measured by surface plasmon resonance (SPR) and determined to be 15 ± 6 nM and 31 ± 18 nM, respectively. This SPR configuration permits the kinetics of early events in signalling pathways to be explored and can be used to initiate descriptions of the GPCR interactome.
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Affiliation(s)
- Roslin J Adamson
- Biomembrane Structure Unit, Biochemistry Department, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Anthony Watts
- Biomembrane Structure Unit, Biochemistry Department, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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160
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Conformational antibody binding to a native, cell-free expressed GPCR in block copolymer membranes. PLoS One 2014; 9:e110847. [PMID: 25329156 PMCID: PMC4203850 DOI: 10.1371/journal.pone.0110847] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 09/19/2014] [Indexed: 11/19/2022] Open
Abstract
G-protein coupled receptors (GPCRs) play a key role in physiological processes and are attractive drug targets. Their biophysical characterization is, however, highly challenging because of their innate instability outside a stabilizing membrane and the difficulty of finding a suitable expression system. We here show the cell-free expression of a GPCR, CXCR4, and its direct embedding in diblock copolymer membranes. The polymer-stabilized CXCR4 is readily immobilized onto biosensor chips for label-free binding analysis. Kinetic characterization using a conformationally sensitive antibody shows the receptor to exist in the correctly folded conformation, showing binding behaviour that is commensurate with heterologously expressed CXCR4.
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161
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Abstract
G protein-coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across cell membranes and represent major targets in the development of novel drug candidates in all clinical areas. Although there have been some recent leads, structural information on GPCRs is relatively rare due to the difficulty associated with crystallization. A specific reason for this is the intrinsic flexibility displayed by GPCRs, which is necessary for their functional diversity. Since GPCRs are integral membrane proteins, interaction of membrane lipids with them constitutes an important area of research in GPCR biology. In particular, membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. The role of membrane cholesterol in GPCR function is discussed with specific example of the serotonin1A receptor. Recent results show that GPCRs are characterized with structural motifs that preferentially associate with cholesterol. An emerging and important concept is oligomerization of GPCRs and its role in GPCR function and signaling. The role of membrane cholesterol in GPCR oligomerization is highlighted. Future research in GPCR biology would offer novel insight in basic biology and provide new avenues for drug discovery.
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162
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Bandari S, Chakraborty H, Covey DF, Chattopadhyay A. Membrane dipole potential is sensitive to cholesterol stereospecificity: implications for receptor function. Chem Phys Lipids 2014; 184:25-9. [PMID: 25219773 DOI: 10.1016/j.chemphyslip.2014.09.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/05/2014] [Accepted: 09/08/2014] [Indexed: 12/25/2022]
Abstract
Dipole potential is the potential difference within the membrane bilayer, which originates due to the nonrandom arrangement of lipid dipoles and water molecules at the membrane interface. Cholesterol, an essential lipid in higher eukaryotic membranes, has previously been shown to increase membrane dipole potential. In this work, we explored the effect of stereoisomers of cholesterol, ent-cholesterol and epi-cholesterol, on membrane dipole potential, monitored by the dual wavelength ratiometric approach utilizing the probe di-8-ANEPPS. Our results show that cholesterol and ent-cholesterol share comparable ability in increasing membrane dipole potential. In contrast, epi-cholesterol displays a slight reduction in membrane dipole potential. Our results constitute the first report on the effect of stereoisomers of cholesterol on membrane dipole potential, and imply that an extremely subtle change in sterol structure can significantly alter the dipolar field at the membrane interface. These results assume relevance in the context of differential abilities of these stereoisomers of cholesterol in supporting the activity of the serotonin1A receptor, a representative G protein-coupled receptor. The close correlation between membrane dipole potential and receptor activity provides new insight in receptor-cholesterol interaction in terms of stereospecificity. We envision that membrane dipole potential could prove to be a sensitive indicator of lipid-protein interactions in biological membranes.
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Affiliation(s)
- Suman Bandari
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Hirak Chakraborty
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Douglas F Covey
- Departments of Developmental Biology, Anesthesiology, Psychiatry and The Taylor Family Institute for Innovative Psychiatry Research, WA University in St. Louis Medical School, St. Louis, MO 63110, USA
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163
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Logez C, Berger S, Legros C, Banères JL, Cohen W, Delagrange P, Nosjean O, Boutin JA, Ferry G, Simonin F, Wagner R. Recombinant human melatonin receptor MT1 isolated in mixed detergents shows pharmacology similar to that in mammalian cell membranes. PLoS One 2014; 9:e100616. [PMID: 24959712 PMCID: PMC4069108 DOI: 10.1371/journal.pone.0100616] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 05/27/2014] [Indexed: 01/08/2023] Open
Abstract
The human melatonin MT1 receptor—belonging to the large family of G protein-coupled receptors (GPCRs)—plays a key role in circadian rhythm regulation and is notably involved in sleep disorders and depression. Structural and functional information at the molecular level are highly desired for fine characterization of this receptor; however, adequate techniques for isolating soluble MT1 material suitable for biochemical and biophysical studies remain lacking. Here we describe the evaluation of a panel of constructs and host systems for the production of recombinant human MT1 receptors, and the screening of different conditions for their solubilization and purification. Our findings resulted in the establishment of an original strategy using a mixture of Fos14 and CHAPS detergents to extract and purify a recombinant human MT1 from Pichia pastoris membranes. This procedure enabled the recovery of relatively pure, monomeric and ligand-binding active MT1 receptor in the near-milligram range. A comparative study based on extensive ligand-binding characterization highlighted a very close correlation between the pharmacological profiles of MT1 purified from yeast and the same receptor present in mammalian cell membranes. The high quality of the purified MT1 was further confirmed by its ability to activate its cognate Gαi protein partner when reconstituted in lipid discs, thus opening novel paths to investigate this receptor by biochemical and biophysical approaches.
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Affiliation(s)
- Christel Logez
- CNRS UMR7242/Laboratoire d'excellence MEDALIS, Institut de Recherche de l'ESBS, Biotechnologie et Signalisation Cellulaire, Université de Strasbourg, Illkirch, France
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Sylvie Berger
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Céline Legros
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Jean-Louis Banères
- CNRS UMR 5247, Institut des Biomolécules Max Mousseron (IBMM), Université de Montpellier 1 and Montpellier 2, Faculté de Pharmacie, Montpellier, France
| | - William Cohen
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Philippe Delagrange
- Unité de Recherches et Découvertes en Neurosciences, Institut de Recherche Servier, Croissy-sur-Seine, France
| | - Olivier Nosjean
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Jean A. Boutin
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
- * E-mail:
| | - Gilles Ferry
- Biotechnologie, Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, Croissy-sur-Seine, France
| | - Frédéric Simonin
- CNRS UMR7242/Laboratoire d'excellence MEDALIS, Institut de Recherche de l'ESBS, Biotechnologie et Signalisation Cellulaire, Université de Strasbourg, Illkirch, France
| | - Renaud Wagner
- CNRS UMR7242/Laboratoire d'excellence MEDALIS, Institut de Recherche de l'ESBS, Biotechnologie et Signalisation Cellulaire, Université de Strasbourg, Illkirch, France
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164
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Javanainen M. Universal Method for Embedding Proteins into Complex Lipid Bilayers for Molecular Dynamics Simulations. J Chem Theory Comput 2014; 10:2577-82. [DOI: 10.1021/ct500046e] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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165
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Zhang YT, Xu LH, Lu Q, Liu KP, Liu PY, Ji F, Liu XM, Ouyang DY, He XH. VASP activation via the Gα13/RhoA/PKA pathway mediates cucurbitacin-B-induced actin aggregation and cofilin-actin rod formation. PLoS One 2014; 9:e93547. [PMID: 24691407 PMCID: PMC3972149 DOI: 10.1371/journal.pone.0093547] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 03/06/2014] [Indexed: 11/25/2022] Open
Abstract
Cucurbitacin B (CuB), a potent antineoplastic agent of cucurbitacin triterpenoids, induces rapid disruption of actin cytoskeleton and aberrant cell cycle inhibiting carcinogenesis. However, the underlying molecular mechanism of such anticancer effects remains incompletely understood. In this study, we showed that CuB treatment rapidly induced vasodilator-stimulated phosphoprotein (VASP) phosphorylation (i.e. activation) at the Ser157 residue and generated VASP clumps which were co-localized with amorphous actin aggregates prior to the formation of highly-ordered cofilin-actin rods in melanoma cells. Knockdown of VASP or inhibition of VASP activation using PKA-specific inhibitor H89 suppressed CuB-induced VASP activation, actin aggregation and cofilin-actin rod formation. The VASP activation was mediated by cAMP-independent PKA activation as CuB decreased the levels of cAMP while MDL12330A, an inhibitor of adenylyl cyclase, had weak effect on VASP activation. Knockdown of either Gα13 or RhoA not only suppressed VASP activation, but also ameliorated CuB-induced actin aggregation and abrogated cofilin-actin rod formation. Collectively, our studies highlighted that the CuB-induced actin aggregation and cofilin-actin rod formation was mediated via the Gα13/RhoA/PKA/VASP pathway.
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Affiliation(s)
- Yan-Ting Zhang
- Department of Immunobiology, Jinan University, Guangzhou, China
| | - Li-Hui Xu
- Department of Cell Biology, Jinan University, Guangzhou, China
| | - Qun Lu
- Department of Anatomy and Cell Biology, East Carolina University Brody School of Medicine, Greenville, North Carolina, United States of America
| | - Kun-Peng Liu
- Department of Immunobiology, Jinan University, Guangzhou, China
| | - Pei-Yan Liu
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Fang Ji
- Guangdong Entomological Institute, Guangzhou, China
| | - Xiao-Ming Liu
- Southern China Primate Research Center, Guangzhou, China
| | - Dong-Yun Ouyang
- Department of Immunobiology, Jinan University, Guangzhou, China
- * E-mail: (DO); (XH)
| | - Xian-Hui He
- Department of Immunobiology, Jinan University, Guangzhou, China
- * E-mail: (DO); (XH)
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166
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Kumari R, Castillo C, Francesconi A. Agonist-dependent signaling by group I metabotropic glutamate receptors is regulated by association with lipid domains. J Biol Chem 2013; 288:32004-19. [PMID: 24045944 DOI: 10.1074/jbc.m113.475863] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group I metabotropic glutamate receptors (mGluRs), mGluR1 and mGluR5, play critical functions in forms of activity-dependent synaptic plasticity and synapse remodeling in physiological and pathological states. Importantly, in animal models of fragile X syndrome, group I mGluR activity is abnormally enhanced, a dysfunction that may partly underlie cognitive deficits in the condition. Lipid rafts are cholesterol- and sphingolipid-enriched membrane domains that are thought to form transient signaling platforms for ligand-activated receptors. Many G protein-coupled receptors, including group I mGluRs, are present in lipid rafts, but the mechanisms underlying recruitment to these membrane domains remain incompletely understood. Here, we show that mGluR1 recruitment to lipid rafts is enhanced by agonist binding and is supported at least in part by an intact cholesterol recognition/interaction amino acid consensus (CRAC) motif in the receptor. Substitutions of critical residues in the motif reduce mGluR1 association with lipid rafts and agonist-induced, mGluR1-dependent activation of extracellular-signal-activated kinase1/2 MAP kinase (ERK-MAPK). We find that alteration of membrane cholesterol content or perturbation of lipid rafts regulates agonist-dependent activation of ERK-MAPK by group I mGluRs, suggesting a potential function for cholesterol as a positive allosteric modulator of receptor function(s). Together, these findings suggest that drugs that alter membrane cholesterol levels or directed to the receptor-cholesterol interface could be employed to modulate abnormal group I mGluR activity in neuropsychiatric conditions, including fragile X syndrome.
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Affiliation(s)
- Ranju Kumari
- From the Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
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167
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Wallgren M, Beranova L, Pham QD, Linh K, Lidman M, Procek J, Cyprych K, Kinnunen PKJ, Hof M, Gröbner G. Impact of oxidized phospholipids on the structural and dynamic organization of phospholipid membranes: a combined DSC and solid state NMR study. Faraday Discuss 2013; 161:499-513; discussion 563-89. [PMID: 23805755 DOI: 10.1039/c2fd20089a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Membranes undergo severe changes under oxidative stress conditions due to the creation of oxidized phospholipid (OxPL) species, which possess molecular properties quite different from their parental lipid components. These OxPLs play crucial roles in various pathological disorders and their occurrence is involved in the onset of intrinsic apoptosis, a fundamental pathway in programmed mammalian cell death. However, the molecular mechanisms by which these lipids can exert their apoptotic action via their host membranes (e.g., altering membrane protein function) are poorly understood. Therefore, we studied the impact of OxPLs on the organization and biophysical properties of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) based lipid membranes by differential scanning calorimetry (DSC) and solid state nuclear magnetic resonance (NMR) spectroscopy. Incorporation of defined OxPLs with either a carboxyl group (1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC)) or aldehyde (1-palmitoyl-(9'oxononanoyl)-sn-glycero-3-phosphocholine (PoxnoPC)) at their truncated sn-2-chain ends enabled us to reveal OxPL species-dependent differences. The calorimetric studies revealed significant effects of OxPLs on the thermotropic phase behavior of DMPC bilayers, especially at elevated levels where PazePC induced more pronounced effects than PoxnoPC. Temperature-dependent changes in the solid state 31P NMR spectra, which provided information of the lipid headgroup region in these mixed membrane systems, reflected this complex phase behavior. In the temperature region between 293 K (onset of the Lalpha-phase) and 298 K, two overlapping NMR spectra were visible which reflect the co-existence of two liquid-crystalline lamellar phases with presumably one reflecting OxPL-poor domains and the other OxPL-rich domains. Deconvolution of the DSC profiles also revealed these two partially overlapping thermal events. In addition, a third thermal, non-NMR-visible, event occurred at low temperatures, which can most likely be associated to a solid-phase mixing/demixing process of the OxPL-containing membranes. The observed phase transitions were moved to higher temperatures in the presence of heavy water due its condensing effect, where additional wideline 2H-NMR studies revealed a complex hydration pattern in the presence of OxPLs.
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Affiliation(s)
- Marcus Wallgren
- Department of Chemistry, Umeå University, Umeå, Sweden SE-901 87
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168
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Jafurulla M, Rao BD, Sreedevi S, Ruysschaert JM, Covey DF, Chattopadhyay A. Stereospecific requirement of cholesterol in the function of the serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:158-63. [PMID: 24008092 DOI: 10.1016/j.bbamem.2013.08.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/16/2013] [Accepted: 08/23/2013] [Indexed: 01/04/2023]
Abstract
The serotonin1A receptor is an important member of the G protein-coupled receptor (GPCR) family. It is involved in the generation and modulation of a variety of cognitive and behavioral functions and serves as a drug target. Previous work from our laboratory has established the sensitivity of the function of the serotonin1A receptor to membrane cholesterol. Solubilization of the hippocampal serotonin1A receptor utilizing the zwitterionic detergent CHAPS is accompanied by loss of cholesterol and results in reduction in specific ligand binding. Replenishment of cholesterol to solubilized membranes restores specific ligand binding to the receptor. We utilized this strategy of sterol replenishment of solubilized membranes to explore the stereospecific stringency of cholesterol for receptor function. We used two stereoisomers of cholesterol, ent-cholesterol (enantiomer of cholesterol) and epi-cholesterol (a diastereomer of cholesterol), for this purpose. Importantly, we show here that while ent-cholesterol could replace cholesterol in supporting receptor function, epi-cholesterol could not. These results imply that the requirement of membrane cholesterol for the serotonin1A receptor function is diastereospecific, yet not enantiospecific. Our results extend and help define specificity of the interaction of membrane cholesterol with the serotonin1A receptor, and represent the first report utilizing ent-cholesterol to examine stereospecificity of GPCR-cholesterol interaction.
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Affiliation(s)
- Md Jafurulla
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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169
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A novel cholesterol-producing Pichia pastoris strain is an ideal host for functional expression of human Na,K-ATPase α3β1 isoform. Appl Microbiol Biotechnol 2013; 97:9465-78. [PMID: 23955473 DOI: 10.1007/s00253-013-5156-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 07/25/2013] [Accepted: 07/27/2013] [Indexed: 12/17/2022]
Abstract
The heterologous expression of mammalian membrane proteins in lower eukaryotes is often hampered by aberrant protein localization, structure, and function, leading to enhanced degradation and, thus, low expression levels. Substantial quantities of functional membrane proteins are necessary to elucidate their structure-function relationships. Na,K-ATPases are integral, human membrane proteins that specifically interact with cholesterol and phospholipids, ensuring protein stability and enhancing ion transport activity. In this study, we present a Pichia pastoris strain which was engineered in its sterol pathway towards the synthesis of cholesterol instead of ergosterol to foster the functional expression of human membrane proteins. Western blot analyses revealed that cholesterol-producing yeast formed enhanced and stable levels of human Na,K-ATPase α3β1 isoform. ATPase activity assays suggested that this Na,K-ATPase isoform was functionally expressed in the plasma membrane. Moreover, [(3)H]-ouabain cell surface-binding studies underscored that the Na,K-ATPase was present in high numbers at the cell surface, surpassing reported expression strains severalfold. This provides evidence that the humanized sterol composition positively influenced Na,K-ATPase α3β1 stability, activity, and localization to the yeast plasma membrane. Prospectively, cholesterol-producing yeast will have high potential for functional expression of many mammalian membrane proteins.
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170
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Zocher M, Bippes CA, Zhang C, Müller DJ. Single-molecule force spectroscopy of G-protein-coupled receptors. Chem Soc Rev 2013; 42:7801-15. [PMID: 23799399 DOI: 10.1039/c3cs60085h] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The applicability of single-molecule force spectroscopy (SMFS) to characterize membrane proteins in vitro is developing rapidly and opening a wide range of fascinating possibilities to study how intra- and intermolecular interactions determine their structural stability and functional state. In particular, understanding how molecular interactions contribute to the functional state of G-protein-coupled receptors (GPCRs) is of importance because they mediate most of our physiological responses and act as therapeutic targets for a broad spectrum of diseases. In our review we focus on SMFS to characterize GPCRs embedded in their physiologically relevant membranes and exposed to physiologically relevant conditions. SMFS uses a molecularly sharp stylus to grasp the terminal end of a GPCR and to quickly unfold the receptor while recording interaction forces. The positional accuracy of SMFS localizes these interactions to structural segments of the GPCR whereas the sensitivity of SMFS enables their stabilizing interaction forces to be quantified. To further investigate the kinetic, energetic and mechanical properties of the structural segments, dynamic SMFS (DFS) probes their stability over a wide range of loading rates. These parameters provide insight into the energy landscape that provides information on the structural and functional properties of the GPCRs. Selected highlights exemplify the application of SMFS to characterize inter- and intramolecular interactions, which change the properties of GPCRs in relation to their functional state (e.g., ligand binding), diseased state (e.g., mutation), or lipid environment such as cholesterol.
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Affiliation(s)
- Michael Zocher
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland.
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171
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Frei AP, Moest H, Novy K, Wollscheid B. Ligand-based receptor identification on living cells and tissues using TRICEPS. Nat Protoc 2013; 8:1321-36. [PMID: 23764939 DOI: 10.1038/nprot.2013.072] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Physiological responses to ligands such as peptides, proteins, pharmaceutical drugs or whole pathogens are generally mediated through interactions with specific cell surface protein receptors. Here we describe the application of TRICEPS, a specifically designed chemoproteomic reagent that can be coupled to a ligand of interest for the subsequent ligand-based capture of corresponding receptors on living cells and tissues. This is achieved by three orthogonal functionalities in TRICEPS-one that enables conjugation to an amino group containing ligands, a second for the ligand-based capture of glycosylated receptors on gently oxidized living cells and a biotin tag for purifying receptor peptides for analysis by quantitative mass spectrometry (MS). Specific receptors for the ligand of interest are identified through quantitative comparison of the identified peptides with a sample generated by a control probe with known (e.g., insulin) or no binding preferences (e.g., TRICEPS quenched with glycine). In combination with powerful statistical models, this ligand-based receptor capture (LRC) technology enables the unbiased and sensitive identification of one or several specific receptors for a given ligand under near-physiological conditions and without the need for genetic manipulations. LRC has been designed for applications with proteins but can easily be adapted for ligands ranging from peptides to intact viruses. In experiments with small ligands that bind to receptors with comparatively large extracellular domains, LRC can also reveal approximate ligand-binding sites owing to the defined spacer length of TRICEPS. Provided that sufficient quantities of the ligand and target cells are available, LRC can be carried out within 1 week.
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Affiliation(s)
- Andreas P Frei
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
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172
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Palczewski K, Orban T. From atomic structures to neuronal functions of g protein-coupled receptors. Annu Rev Neurosci 2013; 36:139-64. [PMID: 23682660 DOI: 10.1146/annurev-neuro-062012-170313] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
G protein-coupled receptors (GPCRs) are essential mediators of signal transduction, neurotransmission, ion channel regulation, and other cellular events. GPCRs are activated by diverse stimuli, including light, enzymatic processing of their N-termini, and binding of proteins, peptides, or small molecules such as neurotransmitters. GPCR dysfunction caused by receptor mutations and environmental challenges contributes to many neurological diseases. Moreover, modern genetic technology has helped identify a rich array of mono- and multigenic defects in humans and animal models that connect such receptor dysfunction with disease affecting neuronal function. The visual system is especially suited to investigate GPCR structure and function because advanced imaging techniques permit structural studies of photoreceptor neurons at both macro and molecular levels that, together with biochemical and physiological assessment in animal models, provide a more complete understanding of GPCR signaling.
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Affiliation(s)
- Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA.
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173
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McNeely PM, Naranjo AN, Robinson AS. Structure-function studies with G protein-coupled receptors as a paradigm for improving drug discovery and development of therapeutics. Biotechnol J 2013; 7:1451-61. [PMID: 23213015 DOI: 10.1002/biot.201200076] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 10/07/2012] [Accepted: 10/10/2012] [Indexed: 12/21/2022]
Abstract
There are a great variety of human membrane proteins, and these currently form the largest group of targets for marketed drugs. Despite the advances in drug design, however, promiscuity between drug molecules and targets often leads to undesired signaling effects, which result in unintended side effects. In this review, one family of membrane proteins - the G protein-coupled receptors (GPCRs) - is used as a model to review experimental techniques that may be used to examine the activity of membrane proteins. As these receptors are highly relevant to healthy human physiology and represent the largest family of drug targets, they represent an excellent model for membrane proteins in general. We also review experimental evidence that suggests there may be multiple ways to target a GPCR - and by extension, membrane proteins - to more effectively target unhealthy phenotypes while reducing the occurrence and severity of side effects.
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Affiliation(s)
- Patrick M McNeely
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA
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174
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G-protein-coupled receptor structure, ligand binding and activation as studied by solid-state NMR spectroscopy. Biochem J 2013; 450:443-57. [DOI: 10.1042/bj20121644] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
GPCRs (G-protein-coupled receptors) are versatile signalling molecules at the cell surface and make up the largest and most diverse family of membrane receptors in the human genome. They convert a large variety of extracellular stimuli into intracellular responses through the activation of heterotrimeric G-proteins, which make them key regulatory elements in a broad range of normal and pathological processes, and are therefore one of the most important targets for pharmaceutical drug discovery. Knowledge of a GPCR structure enables us to gain a mechanistic insight into its function and dynamics, and further aid rational drug design. Despite intensive research carried out over the last three decades, resolving the structural basis of GPCR function is still a major activity. The crystal structures obtained in the last 5 years provide the first opportunity to understand how protein structure dictates the unique functional properties of these complex signalling molecules. However, owing to the intrinsic hydrophobicity, flexibility and instability of membrane proteins, it is still a challenge to crystallize GPCRs, and, when this is possible, it is no longer in its native membrane environment and no longer without modification. Furthermore, the conformational change of the transmembrane α-helices associated with the structure activation increases the difficulty of capturing the activation state of a GPCR to a higher resolution by X-ray crystallography. On the other hand, solid-state NMR may offer a unique opportunity to study membrane protein structure, ligand binding and activation at atomic resolution in the native membrane environment, as well as described functionally significant dynamics. In the present review, we discuss some recent achievements of solid-state NMR for understanding GPCRs, the largest mammalian proteome at ~1% of the total expressed proteins. Structural information, details of determination, details of ligand conformations and the consequences of ligand binding to initiate activation can all be explored with solid-state NMR.
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175
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Expression and purification of functional human mu opioid receptor from E.coli. PLoS One 2013; 8:e56500. [PMID: 23437147 PMCID: PMC3578875 DOI: 10.1371/journal.pone.0056500] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 01/10/2013] [Indexed: 12/17/2022] Open
Abstract
N-terminally his-tagged human mu opioid receptor, a G protein-coupled receptor was produced in E.coli employing synthetic codon-usage optimized constructs. The receptor was expressed in inclusion bodies and membrane-inserted in different E.coli strains. By optimizing the expression conditions the expression level for the membrane-integrated receptor was raised to 0.3–0.5 mg per liter of culture. Milligram quantities of receptor could be enriched by affinity chromatography from IPTG induced cultures grown at 18°C. By size exclusion chromatography the protein fraction with the fraction of alpha-helical secondary structure expected for a 7-TM receptor was isolated, by CD-spectroscopy an alpha-helical content of ca. 45% was found for protein solubilised in the detergent Fos-12. Receptor in Fos-12 micelles was shown to bind endomorphin-1 with a KD of 61 nM. A final yield of 0.17 mg functional protein per liter of culture was obtained.
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176
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Cang X, Du Y, Mao Y, Wang Y, Yang H, Jiang H. Mapping the Functional Binding Sites of Cholesterol in β2-Adrenergic Receptor by Long-Time Molecular Dynamics Simulations. J Phys Chem B 2013; 117:1085-94. [DOI: 10.1021/jp3118192] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiaohui Cang
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Yun Du
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Yanyan Mao
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Yuanyuan Wang
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Huaiyu Yang
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
| | - Hualiang Jiang
- Drug Discovery and
Design Center, State Key Laboratory of Drug Research, Shanghai Institute
of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
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177
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Xie XQ, Chowdhury A. Advances in methods to characterize ligand-induced ionic lock and rotamer toggle molecular switch in G protein-coupled receptors. Methods Enzymol 2013; 520:153-74. [PMID: 23332699 DOI: 10.1016/b978-0-12-391861-1.00007-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Structural biology of GPCRs has made significant progress upon recently developed technologies for GPCRs expression/purification and elucidation of GPCRs crystal structures. The crystal structures provide a snapshot of the receptor structural disposition of GPCRs itself or with cocrystallized ligands, and the results are congruent with biophysical and computer modeling studies reported about GPCRs conformational and dynamics flexibility, regulated activation, and the various stabilizing interactions, such as "molecular switches." The molecular switches generally constitute the most conserved domains within a particular GPCR superfamily. Often agonist-induced receptor activation proceeds by the disruption of majority of these interactions, while antagonist and inverse agonist act as blockers and structural stabilizers, respectively. Several elegant studies, particularly for the β2AR, have demonstrated the relationship between ligand structure, receptor conformational changes, and corresponding pharmacological outcomes. Thus, it is of great importance to understand GPCRs activation related to cell signaling pathways. Herein, we summarize the steps to produce functional GPCRs, generate suitably fluorescent labeled GPCRs and the procedure to use that to understand if ligand-induced activation can proceed by activation of the GPCRs via ionic lock switch and/or rotamer toggle switch mechanisms. Such understanding of ligand structure and mechanism of receptor activation will provide great insight toward uncovering newer pathways of GPCR activation and aid in structure-based drug design.
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Affiliation(s)
- Xiang-Qun Xie
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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178
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179
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Membrane cholesterol stabilizes the human serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2936-42. [DOI: 10.1016/j.bbamem.2012.07.032] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 12/17/2022]
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180
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Singh P, Haldar S, Chattopadhyay A. Differential effect of sterols on dipole potential in hippocampal membranes: implications for receptor function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012. [PMID: 23201544 DOI: 10.1016/j.bbamem.2012.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Dipole potential is the potential difference within the membrane bilayer, which originates due to the nonrandom arrangement of lipid dipoles and water molecules at the membrane interface. In this work, we have explored the possible correlation between functional modulation of a G protein-coupled receptor (the serotonin(1A) receptor) and membrane dipole potential, under conditions of altered membrane sterol composition. We have previously shown that the ligand binding activity of the hippocampal serotonin(1A) receptor is reduced upon cholesterol depletion and could be restored upon replenishment with cholesterol. Interestingly, when the replenishment was carried out with an immediate biosynthetic precursor of cholesterol (7-DHC), differing with cholesterol merely in a double bond, the ligand binding activity of the receptor was not restored. In order to understand the mechanistic framework of receptor-cholesterol interaction, we carried out dipole potential measurements of hippocampal membranes under these conditions, by the dual wavelength ratiometric approach using an electrochromic probe (di-8-ANEPPS). We show here that dipole potential of hippocampal membranes is reduced upon progressive depletion of cholesterol and is restored upon replenishment with cholesterol, but not with 7-DHC. Our results show that the recovery of ligand binding activity of the serotonin(1A) receptor upon replenishment with cholesterol (but not with 7-DHC) could be related to the differential ability of these closely related sterols to modulate membrane dipole potential. We conclude that subtle changes in membrane dipole potential could be crucial in understanding the complex interplay between membrane lipids and proteins in the cellular milieu.
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Affiliation(s)
- Pushpendra Singh
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
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181
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Cholesterol increases kinetic, energetic, and mechanical stability of the human β2-adrenergic receptor. Proc Natl Acad Sci U S A 2012; 109:E3463-72. [PMID: 23151510 DOI: 10.1073/pnas.1210373109] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The steroid cholesterol is an essential component of eukaryotic membranes, and it functionally modulates membrane proteins, including G protein-coupled receptors. To reveal insight into how cholesterol modulates G protein-coupled receptors, we have used dynamic single-molecule force spectroscopy to quantify the mechanical strength and flexibility, conformational variability, and kinetic and energetic stability of structural segments stabilizing the human β(2)-adrenergic receptor (β(2)AR) in the absence and presence of the cholesterol analog cholesteryl hemisuccinate (CHS). CHS considerably increased the kinetic, energetic, and mechanical stability of almost every structural segment at sufficient magnitude to alter the structure and functional relationship of β(2)AR. One exception was the structural core segment of β(2)AR, which establishes multiple ligand binding sites, and its properties were not significantly influenced by CHS.
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182
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Sengupta D, Chattopadhyay A. Identification of Cholesterol Binding Sites in the Serotonin1A Receptor. J Phys Chem B 2012; 116:12991-6. [DOI: 10.1021/jp309888u] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Durba Sengupta
- National Chemical
Laboratory, Council of Scientific and Industrial Research, Dr. Homi Bhabha Road, Pune 411 008, India
| | - Amitabha Chattopadhyay
- Centre for Cellular
and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007,
India
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183
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Shim JY, Bertalovitz AC, Kendall DA. Probing the interaction of SR141716A with the CB1 receptor. J Biol Chem 2012; 287:38741-54. [PMID: 22995906 DOI: 10.1074/jbc.m112.390955] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
SR141716A binds selectively to the brain cannabinoid (CB1) receptor and exhibits a potent inverse agonist/antagonist activity. Although SR141716A, also known as rimonabant, has been withdrawn from the market due to severe side effects, there remains interest in some of its many potential medical applications. Consequently, it is imperative to understand the mechanism by which SR141716A exerts its inverse agonist activity. As a result of using an approach combining mutagenesis and molecular dynamics simulations, we determined the binding mode of SR141716A. We found from the simulation of the CB1-SR141716A complex that SR141716A projects toward TM5 to interact tightly with the major binding pocket, replacing the coordinated water molecules, and secures the Trp-356(6.48) rotameric switch in the inactive state to promote the formation of an extensive water-mediated H-bonding network to the highly conserved SLAXAD and NPXXY motifs in TM2/TM7. We identify for the first time the involvement of the minor binding pocket formed by TM2/TM3/TM7 for SR141716A binding, which complements the major binding pocket formed by TM3/TM5/TM6. Simulation of the F174(2.61)A mutant CB1-SR141716A complex demonstrates the perturbation of TM2 that attenuates SR141716A binding indirectly. These results suggest SR141716A exerts inverse agonist activity through the stabilization of both TM2 and TM5, securing the Trp-356(6.48) rotameric switch and restraining it from activation.
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Affiliation(s)
- Joong-Youn Shim
- J. L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina 27707, USA.
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184
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Oates J, Faust B, Attrill H, Harding P, Orwick M, Watts A. The role of cholesterol on the activity and stability of neurotensin receptor 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2228-33. [DOI: 10.1016/j.bbamem.2012.04.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/15/2012] [Accepted: 04/12/2012] [Indexed: 10/28/2022]
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185
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Gaffuri AL, Ladarre D, Lenkei Z. Type-1 cannabinoid receptor signaling in neuronal development. Pharmacology 2012; 90:19-39. [PMID: 22776780 DOI: 10.1159/000339075] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 04/13/2012] [Indexed: 01/21/2023]
Abstract
The type-1 cannabinoid receptor (CB1R) was initially identified as the neuronal target of Δ(9)-tetrahydrocannabinol (THC), the major psychoactive substance of marijuana. This receptor is one of the most abundant G-protein-coupled receptors in the adult brain, the target of endocannabinoid ligands and a well-characterized retrograde synaptic regulator. However, CB1Rs are also highly and often transiently expressed in neuronal populations in the embryonic and early postnatal brain, even before the formation of synapses. This suggests important physiological roles for CB1Rs during neuronal development. Several recent reviews have summarized our knowledge about the role of the endocannabinoid (eCB) system in neurodevelopment and neurotransmission by focusing on the metabolism of endocannabinoid molecules. Here, we review current knowledge about the effects of the modulation of CB1R signaling during the different phases of brain development. More precisely, we focus on reports that directly implicate CB1Rs during progenitor cell migration and differentiation, neurite outgrowth, axonal pathfinding and synaptogenesis. Based on theoretical considerations and on the reviewed experimental data, we propose a new model to explain the diversity of experimental findings on eCB signaling on neurite growth and axonal pathfinding. In our model, cell-autonomus and paracrine eCBs acting on CB1Rs are part of a global inhibitory network of cytoskeletal effectors, which act in concert with positive-feedback local-excitation loops, to ultimately yield highly polarized neurons.
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Affiliation(s)
- Anne-Lise Gaffuri
- Neurobiology Laboratory, ESPCI-ParisTech, ESPCI-CNRS UMR 7637, Paris, France
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186
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Eren E, van den Berg B. Structural basis for activation of an integral membrane protease by lipopolysaccharide. J Biol Chem 2012; 287:23971-6. [PMID: 22645135 DOI: 10.1074/jbc.m112.376418] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Omptins constitute a unique family of outer membrane proteases that are widespread in Enterobacteriaceae. The plasminogen activator (Pla) of Yersinia pestis is an omptin family member that is very important for development of both bubonic and pneumonic plague. The physiological function of Pla is to cleave (activate) human plasminogen to form the plasma protease plasmin. Uniquely, lipopolysaccharide (LPS) is essential for the catalytic activity of all omptins, including Pla. Why omptins require LPS for enzymatic activity is unknown. Here, we report the co-crystal structure of LPS-free Pla in complex with the activation loop peptide of human plasminogen, its natural substrate. The structure shows that in the absence of LPS, the peptide substrate binds deep within the active site groove and displaces the nucleophilic water molecule, providing an explanation for the dependence of omptins on LPS for enzymatic activity.
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Affiliation(s)
- Elif Eren
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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187
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Goddard AD, Watts A. Regulation of G protein-coupled receptors by palmitoylation and cholesterol. BMC Biol 2012; 10:27. [PMID: 22429402 PMCID: PMC3307485 DOI: 10.1186/1741-7007-10-27] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 03/19/2012] [Indexed: 12/02/2022] Open
Abstract
Due to their membrane location, G protein-coupled receptors (GPCRs) are subject to regulation by soluble and integral membrane proteins as well as membrane components, including lipids and sterols. GPCRs also undergo a variety of post-translational modifications, including palmitoylation. A recent article by Zheng et al. in BMC Cell Biology demonstrates cooperative roles for receptor palmitoylation and cholesterol binding in GPCR dimerization and G protein coupling, underlining the complex regulation of these receptors. See research article http://www.biomedcentral.com/1471-2121/13/6
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Affiliation(s)
- Alan D Goddard
- Biomembrane Structure Unit, Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK
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