1
|
Lobysheva E, Taylor CM, Marshall GR, Kisselev OG. Tauroursodeoxycholic acid binds to the G-protein site on light activated rhodopsin. Exp Eye Res 2018; 170:51-57. [PMID: 29454859 PMCID: PMC5983371 DOI: 10.1016/j.exer.2018.02.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 02/14/2018] [Accepted: 02/14/2018] [Indexed: 12/18/2022]
Abstract
The heterotrimeric G-protein binding site on G-protein coupled receptors remains relatively unexplored regarding its potential as a new target of therapeutic intervention or as a secondary site of action by the existing drugs. Tauroursodeoxycholic acid bears structural resemblance to several compounds that were previously identified to specifically bind to the light-activated form of the visual receptor rhodopsin and to inhibit its activation of transducin. We show that TUDCA stabilizes the active form of rhodopsin, metarhodopsin II, and does not display the detergent-like effects of common amphiphilic compounds that share the cholesterol scaffold structure, such as deoxycholic acid. Computer docking of TUDCA to the model of light-activated rhodopsin revealed that it interacts using similar mode of binding to the C-terminal domain of transducin alpha subunit. The ring regions of TUDCA made hydrophobic contacts with loop 3 region of rhodopsin, while the tail of TUDCA is exposed to solvent. The results show that TUDCA interacts specifically with rhodopsin, which may contribute to its wide-ranging effects on retina physiology and as a potential therapeutic compound for retina degenerative diseases.
Collapse
Affiliation(s)
- E Lobysheva
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA
| | - C M Taylor
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - G R Marshall
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - O G Kisselev
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA.
| |
Collapse
|
2
|
Jones Brunette AM, Sinha A, David L, Farrens DL. Evidence that the Rhodopsin Kinase (GRK1) N-Terminus and the Transducin Gα C-Terminus Interact with the Same "Hydrophobic Patch" on Rhodopsin TM5. Biochemistry 2016; 55:3123-35. [PMID: 27078130 DOI: 10.1021/acs.biochem.6b00328] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Phosphorylation of G protein-coupled receptors (GPCRs) terminates their ability to couple with and activate G proteins by increasing their affinity for arrestins. Unfortunately, detailed information regarding how GPCRs interact with the kinases responsible for their phosphorylation is still limited. Here, we purified fully functional GPCR kinase 1 (GRK1) using a rapid method and used it to gain insights into how this important kinase interacts with the GPCR rhodopsin. Specifically, we find that GRK1 uses the same site on rhodopsin as the transducin (Gt) Gtα C-terminal tail and the arrestin "finger loop", a cleft formed in the cytoplasmic face of the receptor upon activation. Our studies also show GRK1 requires two conserved residues located in this cleft (L226 and V230) that have been shown to be required for Gt activation due to their direct interactions with hydrophobic residues on the Gα C-terminal tail. Our data and modeling studies are consistent with the idea that all three proteins (Gt, GRK1, and visual arrestin) bind, at least in part, in the same site on rhodopsin and interact with the receptor through a similar hydrophobic contact-driven mechanism.
Collapse
Affiliation(s)
- Amber M Jones Brunette
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239-3098, United States
| | - Abhinav Sinha
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239-3098, United States
| | - Larry David
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239-3098, United States
| | - David L Farrens
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239-3098, United States
| |
Collapse
|
3
|
Rose AS, Zachariae U, Grubmüller H, Hofmann KP, Scheerer P, Hildebrand PW. Role of Structural Dynamics at the Receptor G Protein Interface for Signal Transduction. PLoS One 2015; 10:e0143399. [PMID: 26606751 PMCID: PMC4659624 DOI: 10.1371/journal.pone.0143399] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/04/2015] [Indexed: 11/19/2022] Open
Abstract
GPCRs catalyze GDP/GTP exchange in the α-subunit of heterotrimeric G proteins (Gαßγ) through displacement of the Gα C-terminal α5 helix, which directly connects the interface of the active receptor (R*) to the nucleotide binding pocket of G. Hydrogen-deuterium exchange mass spectrometry and kinetic analysis of R* catalysed G protein activation have suggested that displacement of α5 starts from an intermediate GDP bound complex (R*•GGDP). To elucidate the structural basis of receptor-catalysed displacement of α5, we modelled the structure of R*•GGDP. A flexible docking protocol yielded an intermediate R*•GGDP complex, with a similar overall arrangement as in the X-ray structure of the nucleotide free complex (R*•Gempty), however with the α5 C-terminus (GαCT) forming different polar contacts with R*. Starting molecular dynamics simulations of GαCT bound to R* in the intermediate position, we observe a screw-like motion, which restores the specific interactions of α5 with R* in R*•Gempty. The observed rotation of α5 by 60° is in line with experimental data. Reformation of hydrogen bonds, water expulsion and formation of hydrophobic interactions are driving forces of the α5 displacement. We conclude that the identified interactions between R* and G protein define a structural framework in which the α5 displacement promotes direct transmission of the signal from R* to the GDP binding pocket.
Collapse
Affiliation(s)
- Alexander S. Rose
- Institute of Medical Physics and Biophysics (CC2), Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
- Team ProteiInformatics, Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
| | - Ulrich Zachariae
- Dep. of Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, 37077, Göttingen, Germany
- Computational Biology, School of Life Sciences, and Physics, School of Science and Engineering, University of Dundee, Dow Street, Dundee, DD1 5EH, United Kingdom
| | - Helmut Grubmüller
- Dep. of Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Klaus Peter Hofmann
- Institute of Medical Physics and Biophysics (CC2), Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
- Centre of Biophysics and Bioinformatics, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115, Berlin, Germany
| | - Patrick Scheerer
- Institute of Medical Physics and Biophysics (CC2), Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
- Team Protein X-ray Crystallography and Signal Transduction, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
| | - Peter W. Hildebrand
- Institute of Medical Physics and Biophysics (CC2), Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
- Team ProteiInformatics, Universitätsmedizin Berlin, Charitéplatz 1, 10098, Berlin, Germany
| |
Collapse
|
4
|
Blankenship E, Vahedi-Faridi A, Lodowski DT. The High-Resolution Structure of Activated Opsin Reveals a Conserved Solvent Network in the Transmembrane Region Essential for Activation. Structure 2015; 23:2358-2364. [PMID: 26526852 DOI: 10.1016/j.str.2015.09.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/27/2015] [Accepted: 09/06/2015] [Indexed: 11/15/2022]
Abstract
Rhodopsin, a light-activated G protein coupled receptor (GPCR), has been the subject of numerous biochemical and structural investigations, serving as a model receptor for GPCRs and their activation. We present the 2.3-Å resolution structure of native source rhodopsin stabilized in a conformation competent for G protein binding. An extensive water-mediated hydrogen bond network linking the chromophore binding site to the site of G protein binding is observed, providing connections to conserved motifs essential for GPCR activation. Comparison of this extensive solvent-mediated hydrogen-bonding network with the positions of ordered solvent in earlier crystallographic structures of rhodopsin photointermediates reveals both static structural and dynamic functional water-protein interactions present during the activation process. When considered along with observations that solvent occupies similar positions in the structures of other GPCRs, these analyses strongly support an integral role for this dynamic ordered water network in both rhodopsin and GPCR activation.
Collapse
Affiliation(s)
- Elise Blankenship
- Department of Nutrition, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Ardeschir Vahedi-Faridi
- Department of Pharmacology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - David T Lodowski
- Department of Nutrition, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Department of Pharmacology, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| |
Collapse
|
5
|
Duc NM, Kim HR, Chung KY. Structural mechanism of G protein activation by G protein-coupled receptor. Eur J Pharmacol 2015; 763:214-22. [PMID: 25981300 DOI: 10.1016/j.ejphar.2015.05.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/03/2015] [Accepted: 05/11/2015] [Indexed: 12/17/2022]
Abstract
G protein-coupled receptors (GPCRs) are a family of membrane receptors that regulate physiology and pathology of various organs. Consequently, about 40% of drugs in the market targets GPCRs. Heterotrimeric G proteins are composed of α, β, and γ subunits, and act as the key downstream signaling molecules of GPCRs. The structural mechanism of G protein activation by GPCRs has been of a great interest, and a number of biochemical and biophysical studies have been performed since the late 80's. These studies investigated the interface between GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. Recently, arrestins are also reported to be important molecular switches in GPCR-mediated signal transduction, and the physiological output of arrestin-mediated signal transduction is different from that of G protein-mediated signal transduction. Understanding the structural mechanism of the activation of G proteins and arrestins would provide fundamental information for the downstream signaling-selective GPCR-targeting drug development. This review will discuss the structural mechanism of GPCR-induced G protein activation by comparing previous biochemical and biophysical studies.
Collapse
Affiliation(s)
- Nguyen Minh Duc
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea.
| |
Collapse
|
6
|
Structure-Based Biophysical Analysis of the Interaction of Rhodopsin with G Protein and Arrestin. Methods Enzymol 2015; 556:563-608. [DOI: 10.1016/bs.mie.2014.12.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
7
|
Cheguru P, Majumder A, Yadav R, Gopalakrishna KN, Gakhar L, Artemyev NO. The solution structure of the transducin-α-uncoordinated 119 protein complex suggests occlusion of the Gβ₁γ₁-binding sites. FEBS J 2014; 282:550-61. [PMID: 25425538 DOI: 10.1111/febs.13161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/17/2014] [Accepted: 11/24/2014] [Indexed: 11/28/2022]
Abstract
Uncoordinated 119 protein (UNC119) is a partner of transducin-α subunit (Gαt ) that is essential for transducin trafficking in rod photoreceptors. The interaction is known to involve binding of the acylated N terminus of Gαt to the hydrophobic pocket of UNC119. To gain insights into the mechanism of transducin trafficking, we isolated a highly pure protein complex between myristoylated chimeric Gαt (Gαt *) and UNC119₅₀₋₂₄₀, and examined the solution structure by small angle X-ray scattering and chemical crosslinking. The solution structure of the Gαt -UNC119₅₀₋₂₄₀ complex was derived with rigid body/ab initio modeling against the small angle X-ray scattering data by use of known atomic structures of Gαt and UNC119, and a distance constraint based on the protein crosslinking with p-phenyldimaleimide. The model of the Gαt -UNC119₅₀₋₂₄₀ complex indicates rotation and bending of the N-terminal α-helix of Gαt from its position in the structure of the heterotrimeric G-protein transducin (Gt ). This allows a considerably more compact complex conformation, which also suggests a novel interface involving the switch II/α3-β5 surface of Gαt . Supporting a novel interface, UNC119 was found to bind full-length Gαt * more strongly than the Gαt N-terminal peptide. Furthermore, UNC119 competed with the effector molecule phosphodiesterase-6 γ-subunit, which is known to bind to the same surface of Gαt . The solution structure of the Gαt -UNC119 complex suggests that the ability of UNC119 to dissociate Gt subunits and release Gαt from the membrane is attributable to disruption and sterical occlusion of the Gβ₁γ₁-binding sites on Gαt .
Collapse
Affiliation(s)
- Pallavi Cheguru
- Department of Molecular Physiology and Biophysics, University of Iowa, IA, USA
| | | | | | | | | | | |
Collapse
|
8
|
Crystal structure of a common GPCR-binding interface for G protein and arrestin. Nat Commun 2014; 5:4801. [PMID: 25205354 PMCID: PMC4199108 DOI: 10.1038/ncomms5801] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 07/24/2014] [Indexed: 01/18/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) transmit extracellular signals to activate intracellular heterotrimeric G proteins (Gαβγ) and arrestins. For G protein signalling, the Gα C-terminus (GαCT) binds to a cytoplasmic crevice of the receptor that opens upon activation. A consensus motif is shared among GαCT from the Gi/Gt family and the ‘finger loop’ region (ArrFL1–4) of all four arrestins. Here we present a 2.75 Å crystal structure of ArrFL-1, a peptide analogue of the finger loop of rod photoreceptor arrestin, in complex with the prototypical GPCR rhodopsin. Functional binding of ArrFL to the receptor was confirmed by ultraviolet-visible absorption spectroscopy, competitive binding assays and Fourier transform infrared spectroscopy. For both GαCT and ArrFL, binding to the receptor crevice induces a similar reverse turn structure, although significant structural differences are seen at the rim of the binding crevice. Our results reflect both the common receptor-binding interface and the divergent biological functions of G proteins and arrestins. G-protein-coupled receptors (GPCRs) transmit signals through intracellular heterotrimeric G proteins and arrestins. Here, Szczepek et al. present the structure of a common binding interface for Gα and arrestin on rhodopsin to shed light on key interactions that mediate transduction of specific signals through a single GPCR.
Collapse
|
9
|
Rose AS, Elgeti M, Zachariae U, Grubmüller H, Hofmann KP, Scheerer P, Hildebrand PW. Position of Transmembrane Helix 6 Determines Receptor G Protein Coupling Specificity. J Am Chem Soc 2014; 136:11244-7. [DOI: 10.1021/ja5055109] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
| | | | - Ulrich Zachariae
- Division
of Computational Biology, College of Life Sciences, and Division of
Physics, School of Engineering, Physics and Mathematics, University of Dundee, Dow Street, Dundee DD1
5EH, U.K
| | - Helmut Grubmüller
- Department
of Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
| | - Klaus Peter Hofmann
- Centre
of Biophysics and Bioinformatics, Humboldt-Universität zu Berlin, Invalidenstrasse
42, D-10115 Berlin, Germany
| | | | | |
Collapse
|
10
|
Mnpotra JS, Qiao Z, Cai J, Lynch DL, Grossfield A, Leioatts N, Hurst DP, Pitman MC, Song ZH, Reggio PH. Structural basis of G protein-coupled receptor-Gi protein interaction: formation of the cannabinoid CB2 receptor-Gi protein complex. J Biol Chem 2014; 289:20259-72. [PMID: 24855641 DOI: 10.1074/jbc.m113.539916] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In this study, we applied a comprehensive G protein-coupled receptor-Gαi protein chemical cross-linking strategy to map the cannabinoid receptor subtype 2 (CB2)-Gαi interface and then used molecular dynamics simulations to explore the dynamics of complex formation. Three cross-link sites were identified using LC-MS/MS and electrospray ionization-MS/MS as follows: 1) a sulfhydryl cross-link between C3.53(134) in TMH3 and the Gαi C-terminal i-3 residue Cys-351; 2) a lysine cross-link between K6.35(245) in TMH6 and the Gαi C-terminal i-5 residue, Lys-349; and 3) a lysine cross-link between K5.64(215) in TMH5 and the Gαi α4β6 loop residue, Lys-317. To investigate the dynamics and nature of the conformational changes involved in CB2·Gi complex formation, we carried out microsecond-time scale molecular dynamics simulations of the CB2 R*·Gαi1β1γ2 complex embedded in a 1-palmitoyl-2-oleoyl-phosphatidylcholine bilayer, using cross-linking information as validation. Our results show that although molecular dynamics simulations started with the G protein orientation in the β2-AR*·Gαsβ1γ2 complex crystal structure, the Gαi1β1γ2 protein reoriented itself within 300 ns. Two major changes occurred as follows. 1) The Gαi1 α5 helix tilt changed due to the outward movement of TMH5 in CB2 R*. 2) A 25° clockwise rotation of Gαi1β1γ2 underneath CB2 R* occurred, with rotation ceasing when Pro-139 (IC-2 loop) anchors in a hydrophobic pocket on Gαi1 (Val-34, Leu-194, Phe-196, Phe-336, Thr-340, Ile-343, and Ile-344). In this complex, all three experimentally identified cross-links can occur. These findings should be relevant for other class A G protein-coupled receptors that couple to Gi proteins.
Collapse
Affiliation(s)
- Jagjeet S Mnpotra
- From the Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402
| | - Zhuanhong Qiao
- the Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, Kentucky 40292
| | - Jian Cai
- the Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, Kentucky 40292
| | - Diane L Lynch
- From the Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402
| | - Alan Grossfield
- the Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Nicholas Leioatts
- the Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Dow P Hurst
- From the Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402
| | - Michael C Pitman
- From the Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402, the Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598
| | - Zhao-Hui Song
- the Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, Kentucky 40292,
| | - Patricia H Reggio
- From the Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, North Carolina 27402,
| |
Collapse
|
11
|
Chung KY. Structural Aspects of GPCR-G Protein Coupling. Toxicol Res 2014; 29:149-55. [PMID: 24386514 PMCID: PMC3877993 DOI: 10.5487/tr.2013.29.3.149] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/10/2013] [Accepted: 09/17/2013] [Indexed: 11/24/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane receptors; approximately 40% of drugs on the market target GPCRs. A precise understanding of the activation mechanism of GPCRs would facilitate the development of more effective and less toxic drugs. Heterotrimeric G proteins are important molecular switches in GPCR-mediated signal transduction. An agonist-activated receptor interacts with specific sites on G proteins and promotes the release of GDP from the Gα subunit. Because of the important biological role of the GPCR-G protein coupling, conformational changes in the G protein upon receptor coupling have been of great interest. One of the most important questions was the interface between the GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. A number of biochemical and biophysical studies have been performed since the late 80s to address these questions; there was a significant breakthrough in 2011 when the crystal structure of a GPCR-G protein complex was solved. This review discusses the structural aspects of GPCR-G protein coupling by comparing the results of previous biochemical and biophysical studies to the GPCR-G protein crystal structure.
Collapse
Affiliation(s)
- Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon, Korea
| |
Collapse
|
12
|
Alexiev U, Farrens DL. Fluorescence spectroscopy of rhodopsins: insights and approaches. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:694-709. [PMID: 24183695 DOI: 10.1016/j.bbabio.2013.10.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 10/11/2013] [Accepted: 10/16/2013] [Indexed: 01/30/2023]
Abstract
Fluorescence spectroscopy has become an established tool at the interface of biology, chemistry and physics because of its exquisite sensitivity and recent technical advancements. However, rhodopsin proteins present the fluorescence spectroscopist with a unique set of challenges and opportunities due to the presence of the light-sensitive retinal chromophore. This review briefly summarizes some approaches that have successfully met these challenges and the novel insights they have yielded about rhodopsin structure and function. We start with a brief overview of fluorescence fundamentals and experimental methodologies, followed by more specific discussions of technical challenges rhodopsin proteins present to fluorescence studies. Finally, we end by discussing some of the unique insights that have been gained specifically about visual rhodopsin and its interactions with affiliate proteins through the use of fluorescence spectroscopy. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
Collapse
Affiliation(s)
- Ulrike Alexiev
- Physics Department, Freie Universität Berlin, Berlin, Germany.
| | - David L Farrens
- Departments of Biochemistry and Molecular Biology, Oregon Health Sciences University, USA
| |
Collapse
|
13
|
Shim JY, Ahn KH, Kendall DA. Molecular basis of cannabinoid CB1 receptor coupling to the G protein heterotrimer Gαiβγ: identification of key CB1 contacts with the C-terminal helix α5 of Gαi. J Biol Chem 2013; 288:32449-32465. [PMID: 24092756 DOI: 10.1074/jbc.m113.489153] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cannabinoid (CB1) receptor is a member of the rhodopsin-like G protein-coupled receptor superfamily. The human CB1 receptor, which is among the most expressed receptors in the brain, has been implicated in several disease states, including drug addiction, anxiety, depression, obesity, and chronic pain. Different classes of CB1 agonists evoke signaling pathways through the activation of specific subtypes of G proteins. The molecular basis of CB1 receptor coupling to its cognate G protein is unknown. As a first step toward understanding CB1 receptor-mediated G protein signaling, we have constructed a ternary complex structural model of the CB1 receptor and Gi heterotrimer (CB1-Gi), guided by the x-ray structure of β2-adrenergic receptor (β2AR) in complex with Gs (β2AR-Gs), through 824-ns duration molecular dynamics simulations in a fully hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer environment. We identified a group of residues at the juxtamembrane regions of the intracellular loops 2 and 3 (IC2 and IC3) of the CB1 receptor, including Ile-218(3.54), Tyr-224(IC2), Asp-338(6.30), Arg-340(6.32), Leu-341(6.33), and Thr-344(6.36), as potential key contacts with the extreme C-terminal helix α5 of Gαi. Ala mutations of these residues at the receptor-Gi interface resulted in little G protein coupling activity, consistent with the present model of the CB1-Gi complex, which suggests tight interactions between CB1 and the extreme C-terminal helix α5 of Gαi. The model also suggests that unique conformational changes in the extreme C-terminal helix α5 of Gα play a crucial role in the receptor-mediated G protein activation.
Collapse
Affiliation(s)
- Joong-Youn Shim
- From the J. L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina 27707.
| | - Kwang H Ahn
- the Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269
| | - Debra A Kendall
- the Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269
| |
Collapse
|
14
|
Moreira IS. Structural features of the G-protein/GPCR interactions. Biochim Biophys Acta Gen Subj 2013; 1840:16-33. [PMID: 24016604 DOI: 10.1016/j.bbagen.2013.08.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND The details of the functional interaction between G proteins and the G protein coupled receptors (GPCRs) have long been subjected to extensive investigations with structural and functional assays and a large number of computational studies. SCOPE OF REVIEW The nature and sites of interaction in the G-protein/GPCR complexes, and the specificities of these interactions selecting coupling partners among the large number of families of GPCRs and G protein forms, are still poorly defined. MAJOR CONCLUSIONS Many of the contact sites between the two proteins in specific complexes have been identified, but the three dimensional molecular architecture of a receptor-Gα interface is only known for one pair. Consequently, many fundamental questions regarding this macromolecular assembly and its mechanism remain unanswered. GENERAL SIGNIFICANCE In the context of current structural data we review the structural details of the interfaces and recognition sites in complexes of sub-family A GPCRs with cognate G-proteins, with special emphasis on the consequences of activation on GPCR structure, the prevalence of preassembled GPCR/G-protein complexes, the key structural determinants for selective coupling and the possible involvement of GPCR oligomerization in this process.
Collapse
Affiliation(s)
- Irina S Moreira
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
| |
Collapse
|
15
|
Elgeti M, Rose AS, Bartl FJ, Hildebrand PW, Hofmann KP, Heck M. Precision vs flexibility in GPCR signaling. J Am Chem Soc 2013; 135:12305-12. [PMID: 23883288 DOI: 10.1021/ja405133k] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The G protein coupled receptor (GPCR) rhodopsin activates the heterotrimeric G protein transducin (Gt) to transmit the light signal into retinal rod cells. The rhodopsin activity is virtually zero in the dark and jumps by more than one billion fold after photon capture. Such perfect switching implies both high fidelity and speed of rhodopsin/Gt coupling. We employed Fourier transform infrared (FTIR) spectroscopy and supporting all-atom molecular dynamics (MD) simulations to study the conformational diversity of rhodopsin in membrane environment and extend the static picture provided by the available crystal structures. The FTIR results show how the equilibria of inactive and active protein states of the receptor (so-called metarhodopsin states) are regulated by the highly conserved E(D)RY and Yx7K(R) motives. The MD data identify an intrinsically unstructured cytoplasmic loop region connecting transmembrane helices 5 and 6 (CL3) and show how each protein state is split into conformational substates. The C-termini of the Gtγ- and Gtα-subunits (GαCT and GγCT), prepared as synthetic peptides, are likely to bind sequentially and at different sites of the active receptor. The peptides have different effects on the receptor conformation. While GγCT stabilizes the active states but preserves CL3 flexibility, GαCT selectively stabilizes a single conformational substate with largely helical CL3, as it is found in crystal structures. Based on these results we propose a mechanism for the fast and precise signal transfer from rhodopsin to Gt, which assumes a stepwise and mutual reduction of their conformational space. The mechanism relies on conserved amino acids and may therefore underlie GPCR/G protein coupling in general.
Collapse
Affiliation(s)
- Matthias Elgeti
- Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
| | | | | | | | | | | |
Collapse
|
16
|
Passamaneck YJ, Martindale MQ. Evidence for a phototransduction cascade in an early brachiopod embryo. Integr Comp Biol 2013; 53:17-26. [PMID: 23630970 DOI: 10.1093/icb/ict037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Bilaterian photoreceptor cells are characterized by the expression of opsins, signal transduction genes, and ion channels, which together facilitate behavioral responses to light. We have previously identified a ciliary opsin gene from the brachiopod Terebratalia transversa, whose expression in gastrula stage embryos coincides with a photoresponse behavior, suggesting the presence of a functional phototransduction system in these early embryos. To further evaluate the potential for light reception in these embryos, we surveyed transcriptome data to identify phototransduction genes and evaluated their expression. In addition to the previously described ciliary opsin gene, we have identified two Go-class opsins that are also expressed in gastrula stage embryos. Representative members from all classes of Gα-protein genes were also expressed, with a Gα12-class gene being localized in the same anterior ectodermal domain as the opsin transcripts. Both CNG-class and TRP-class ion channels were expressed in the gastrula stage embryos, as were GRK and arrestin genes, which are associated with inhibition of rhodopsin activity. Taken together, these data support the presence of a functional phototransduction system in the early brachiopod embryo.
Collapse
Affiliation(s)
- Yale J Passamaneck
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA.
| | | |
Collapse
|
17
|
Seddik R, Jungblut SP, Silander OK, Rajalu M, Fritzius T, Besseyrias V, Jacquier V, Fakler B, Gassmann M, Bettler B. Opposite effects of KCTD subunit domains on GABA(B) receptor-mediated desensitization. J Biol Chem 2012; 287:39869-77. [PMID: 23035119 DOI: 10.1074/jbc.m112.412767] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GABA(B) receptors assemble from principle and auxiliary subunits. The principle subunits GABA(B1) and GABA(B2) form functional heteromeric GABA(B(1,2)) receptors that associate with homotetramers of auxiliary KCTD8, -12, -12b, or -16 (named after their K(+) channel tetramerization domain) subunits. These auxiliary subunits constitute receptor subtypes with distinct functional properties. KCTD12 and -12b generate desensitizing receptor responses while KCTD8 and -16 generate largely non-desensitizing receptor responses. The structural elements of the KCTDs underlying these differences in desensitization are unknown. KCTDs are modular proteins comprising a T1 tetramerization domain, which binds to GABA(B2), and a H1 homology domain. KCTD8 and -16 contain an additional C-terminal H2 homology domain that is not sequence-related to the H1 domains. No functions are known for the H1 and H2 domains. Here we addressed which domains and sequence motifs in KCTD proteins regulate desensitization of the receptor response. We found that the H1 domains in KCTD12 and -12b mediate desensitization through a particular sequence motif, T/NFLEQ, which is not present in the H1 domains of KCTD8 and -16. In addition, the H2 domains in KCTD8 and -16 inhibit desensitization when expressed C-terminal to the H1 domains but not when expressed as a separate protein in trans. Intriguingly, the inhibitory effect of the H2 domain is sequence-independent, suggesting that the H2 domain sterically hinders desensitization by the H1 domain. Evolutionary analysis supports that KCTD12 and -12b evolved desensitizing properties by liberating their H1 domains from antagonistic H2 domains and acquisition of the T/NFLEQ motif.
Collapse
Affiliation(s)
- Riad Seddik
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Zheng X, Wu C, Ponder JW, Marshall GR. Molecular dynamics of β-hairpin models of epigenetic recognition motifs. J Am Chem Soc 2012; 134:15970-8. [PMID: 22934656 DOI: 10.1021/ja306803v] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The conformations and stabilities of the β-hairpin model peptides of Waters (Riemen, A. J.; Waters, M. L. Biochemistry 2009, 48, 1525; Hughes, R. M.; Benshoff, M. L.; Waters, M. L. Chemistry 2007, 13, 5753) have been experimentally characterized as a function of lysine ε-methylation. These models were developed to explore molecular recognition of known epigenetic recognition motifs. This system offered an opportunity to computationally examine the role of cation-π interactions, desolvation of the ε-methylated ammonium groups, and aromatic/aromatic interactions on the observed differences in NMR spectra. AMOEBA, a second-generation force field (Ponder, J. W.; Wu, C.; Ren, P.; Pande, V. S.; Chodera, J. D.; Schnieders, M. J.; Haque, I.; Mobley, D. L.; Lambrecht, D. S.; DiStasio, R. A., Jr.; Head-Gordon, M.; Clark, G. N.; Johnson, M. E.; Head-Gordon, T. J. Phys. Chem. B 2010, 114, 2549), was chosen as it includes both multipole electrostatics and polarizability thought to be essential to accurately characterize such interactions. Independent parametrization of ε-methylated amines was required from which aqueous solvation free energies were estimated and shown to agree with literature values. Molecular dynamics simulations (100 ns) using the derived parameters with model peptides, such as Ac-R-W-V-W-V-N-G-Orn-K(Me)(n)-I-L-Q-NH(2), where n = 0, 1, 2, or 3, were conducted in explicit solvent. Distances between the centers of the indole rings of the two-tryptophan residues, 2 and 4, and the ε-methylated ammonium group on Lys-9 as well as the distance between the N- and C-termini were monitored to estimate the strength and orientation of the cation-π and aromatic/aromatic interactions. In agreement with the experimental data, the stability of the β-hairpin increased significantly with lysine ε-methylation. The ability of MD simulations to reproduce the observed NOEs for the four peptides was further estimated for the monopole-based force fields, AMBER, CHARMM, and OPLSAA. AMOEBA correctly predicted over 80% of the observed NOEs for all 4 peptides, while the three-monopole force fields were 40-50% predictive in only 2 cases and approximately 10% in the other 10 examples. Preliminary analysis suggests that the decreased cost of desolvation of the substituted ammonium group significantly compensated for the reduced cation-π interaction resulting from the increased separation due to steric bulk of the ε-methylated amines.
Collapse
Affiliation(s)
- Xiange Zheng
- Department of Chemistry and of Biochemistry, Washington University, St. Louis, Missouri 63105, United States
| | | | | | | |
Collapse
|
19
|
Lomonosova E, Kolesnikov AV, Kefalov VJ, Kisselev OG. Signaling states of rhodopsin in rod disk membranes lacking transducin βγ-complex. Invest Ophthalmol Vis Sci 2012; 53:1225-33. [PMID: 22266510 DOI: 10.1167/iovs.11-9350] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To characterize the possible role of transducin Gtβγ-complex in modulating the signaling properties of photoactivated rhodopsin and its lifetime in rod disc membranes and intact rods. METHODS Rhodopsin photolysis was studied using UV-visible spectroscopy and rapid scanning spectroscopy in the presence of hydroxylamine in highly purified wild-type and Gtγ-deficient mouse rod disc membranes. Complex formation between photoactivated rhodopsin and transducin was measured by extra-metarhodopsin (meta) II assay. Recovery of dark current and flash sensitivity in individual intact wild-type and Gtγ-deficient mouse rods was measured by single-cell suction recordings. RESULTS Photoconversion of rhodopsin to meta I/meta II equilibrium proceeds normally after elimination of the Gtβγ-complex. The meta I/meta II ratio, the rate of meta II decay, the reactivity of meta II toward hydroxylamine, and the rate of meta III formation in Gtγ-deficient rod disc membranes were identical with those observed in wild-type samples. Under low-intensity illumination, the amount of extra-meta II in Gtγ-deficient discs was significantly reduced. The initial rate of dark current recovery after 12% rhodopsin bleach was three times faster in Gtγ-deficient rods, whereas the rate of the late current recovery was largely unchanged. Mutant rods also exhibited faster postbleach recovery of flash sensitivity. CONCLUSIONS Photoactivation and thermal decay of rhodopsin proceed similarly in wild-type and Gtγ-deficient mouse rods, but the complex formation between photoactivated rhodopsin and transducin is severely compromised in the absence of Gtβγ. The resultant lower transduction activation contributes to faster photoresponse recovery after a moderate pigment bleach in Gtγ-deficient rods.
Collapse
Affiliation(s)
- Elena Lomonosova
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, MO, USA
| | | | | | | |
Collapse
|
20
|
The spin label amino acid TOAC and its uses in studies of peptides: chemical, physicochemical, spectroscopic, and conformational aspects. Biophys Rev 2012; 4:45-66. [PMID: 22347893 PMCID: PMC3271205 DOI: 10.1007/s12551-011-0064-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 12/20/2011] [Indexed: 01/21/2023] Open
Abstract
We review work on the paramagnetic amino acid 2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid, TOAC, and its applications in studies of peptides and peptide synthesis. TOAC was the first spin label probe incorporated in peptides by means of a peptide bond. In view of the rigid character of this cyclic molecule and its attachment to the peptide backbone via a peptide bond, TOAC incorporation has been very useful to analyze backbone dynamics and peptide secondary structure. Many of these studies were performed making use of EPR spectroscopy, but other physical techniques, such as X-ray crystallography, CD, fluorescence, NMR, and FT-IR, have been employed. The use of double-labeled synthetic peptides has allowed the investigation of their secondary structure. A large number of studies have focused on the interaction of peptides, both synthetic and biologically active, with membranes. In the latter case, work has been reported on ligands and fragments of GPCR, host defense peptides, phospholamban, and β-amyloid. EPR studies of macroscopically aligned samples have provided information on the orientation of peptides in membranes. More recent studies have focused on peptide–protein and peptide–nucleic acid interactions. Moreover, TOAC has been shown to be a valuable probe for paramagnetic relaxation enhancement NMR studies of the interaction of labeled peptides with proteins. The growth of the number of TOAC-related publications suggests that this unnatural amino acid will find increasing applications in the future.
Collapse
|
21
|
Fanelli F, De Benedetti PG. Update 1 of: computational modeling approaches to structure-function analysis of G protein-coupled receptors. Chem Rev 2011; 111:PR438-535. [PMID: 22165845 DOI: 10.1021/cr100437t] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Francesca Fanelli
- Dulbecco Telethon Institute, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy.
| | | |
Collapse
|
22
|
Shpakov AO. Signal protein-derived peptides as functional probes and regulators of intracellular signaling. JOURNAL OF AMINO ACIDS 2011; 2011:656051. [PMID: 22312467 PMCID: PMC3268021 DOI: 10.4061/2011/656051] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 06/01/2011] [Indexed: 12/21/2022]
Abstract
The functionally important regions of signal proteins participating in their specific interaction and responsible for transduction of hormonal signal into cell are rather short in length, having, as a rule, 8 to 20 amino acid residues. Synthetic peptides corresponding to these regions are able to mimic the activated form of full-size signal protein and to trigger signaling cascades in the absence of hormonal stimulus. They modulate protein-protein interaction and influence the activity of signal proteins followed by changes in their regulatory and catalytic sites. The present review is devoted to the achievements and perspectives of the study of signal protein-derived peptides and to their application as selective and effective regulators of hormonal signaling systems in vitro and in vivo. Attention is focused on the structure, biological activity, and molecular mechanisms of action of peptides, derivatives of the receptors, G protein α subunits, and the enzymes generating second messengers.
Collapse
Affiliation(s)
- Alexander O Shpakov
- I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Thorez avenue 44, 194223 St. Petersburg, Russia
| |
Collapse
|
23
|
Homology modeling of the structure of acyl coA:isopenicillin N-acyltransferase (IAT) from Penicillium chrysogenum. IAT interaction studies with isopenicillin-N, combining molecular dynamics simulations and docking. J Mol Model 2011; 18:1189-205. [DOI: 10.1007/s00894-011-1143-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 05/30/2011] [Indexed: 10/18/2022]
|
24
|
Solution- and solid-state NMR studies of GPCRs and their ligands. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1462-75. [DOI: 10.1016/j.bbamem.2010.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 12/29/2022]
|
25
|
Interaction of a G protein with an activated receptor opens the interdomain interface in the alpha subunit. Proc Natl Acad Sci U S A 2011; 108:9420-4. [PMID: 21606326 DOI: 10.1073/pnas.1105810108] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In G-protein signaling, an activated receptor catalyzes GDP/GTP exchange on the G(α) subunit of a heterotrimeric G protein. In an initial step, receptor interaction with G(α) acts to allosterically trigger GDP release from a binding site located between the nucleotide binding domain and a helical domain, but the molecular mechanism is unknown. In this study, site-directed spin labeling and double electron-electron resonance spectroscopy are employed to reveal a large-scale separation of the domains that provides a direct pathway for nucleotide escape. Cross-linking studies show that the domain separation is required for receptor enhancement of nucleotide exchange rates. The interdomain opening is coupled to receptor binding via the C-terminal helix of G(α), the extension of which is a high-affinity receptor binding element.
Collapse
|
26
|
Simulated Q-annealing: conformational search with an effective potential. J Mol Model 2011; 18:213-20. [PMID: 21523533 DOI: 10.1007/s00894-011-1072-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 03/24/2011] [Indexed: 10/18/2022]
Abstract
We have tested a version of the generalized simulated annealing algorithm based on molecular dynamics simulations with effective potential suggested by Tsallis statistics. The generalized annealing method, termed "simulated Q-annealing (SQ)," is applied to the simulations of a synthetic 11-residue peptide segment (1AQG). In SQ, the energy barriers between local minima change as the parameter q is varied and specific degrees of freedom can be selectively heated up and annealed. Conformational dynamics obtained by ordinary simulated annealing (SA) and SQ simulations are compared in order to illustrate the effectiveness of the SQ approach in conformational searching. We show that SQ can navigate the potential energy surface efficiently with a simple annealing protocol and demonstrate that conformations sampled by SQ can represent the funnel-like free energy surface.
Collapse
|
27
|
Elgeti M, Kazmin R, Heck M, Morizumi T, Ritter E, Scheerer P, Ernst OP, Siebert F, Hofmann KP, Bartl FJ. Conserved Tyr223(5.58) plays different roles in the activation and G-protein interaction of rhodopsin. J Am Chem Soc 2011; 133:7159-65. [PMID: 21506561 DOI: 10.1021/ja200545n] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rhodopsin, a seven transmembrane helix (TM) receptor, binds its ligand 11-cis-retinal via a protonated Schiff base. Coupling to the G-protein transducin (G(t)) occurs after light-induced cis/trans-retinal isomerization, which leads through photoproducts into a sequence of metarhodopsin (Meta) states: Meta I ⇌ Meta IIa ⇌ Meta IIb ⇌ Meta IIbH(+). The structural changes behind this three-step activation scheme are mediated by microswitch domains consisting of conserved amino acids. Here we focus on Tyr223(5.58) as part of the Y(5.58)X(7)K(R)(5.66) motif. Mutation to Ala, Phe, or Glu results in specific impairments of G(t)-activation measured by intrinsic G(t) fluorescence. UV-vis/FTIR spectroscopy of rhodopsin and its complex with a C-terminal G(t)α peptide allows the assignment of these deficiencies to specific steps in the activation path. Effects of mutation occur already in Meta I but do not directly influence deprotonation of the Schiff base during formation of Meta IIa. Absence of the whole phenol ring (Y223A) allows the activating motion of TM6 in Meta IIb but impairs the coupling to G(t). When only the hydroxyl group is lacking (Y223F), Meta IIb does not accumulate, but the activity toward G(t) remains substantial. From the FTIR features of Meta IIbH(+) we conclude that proton uptake to Glu134(3.49) is mandatory for Tyr223(5.58) to engage in the interaction with the key player Arg135(3.50) predicted by X-ray analysis. This polar interaction is partially recovered in Y223E, explaining its relatively high activity. Only the phenol side chain of tyrosine provides all characteristics for accumulation of the active state and G-protein activation.
Collapse
Affiliation(s)
- Matthias Elgeti
- Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Huang CC, Tesmer JJG. Recognition in the face of diversity: interactions of heterotrimeric G proteins and G protein-coupled receptor (GPCR) kinases with activated GPCRs. J Biol Chem 2011; 286:7715-7721. [PMID: 21199869 DOI: 10.1074/jbc.r109.051847] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors (GPCRs) represent the largest class of integral membrane protein receptors in the human genome. Despite the great diversity of ligands that activate these GPCRs, they interact with a relatively small number of intracellular proteins to induce profound physiological change. Both heterotrimeric G proteins and GPCR kinases are well known for their ability to specifically recognize GPCRs in their active state. Recent structural studies now suggest that heterotrimeric G proteins and GPCR kinases identify activated receptors via a common molecular mechanism despite having completely different folds.
Collapse
Affiliation(s)
| | - John J G Tesmer
- From the Life Sciences Institute and; Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-2216.
| |
Collapse
|
29
|
Highly conserved tyrosine stabilizes the active state of rhodopsin. Proc Natl Acad Sci U S A 2010; 107:19861-6. [PMID: 21041664 DOI: 10.1073/pnas.1009405107] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Light-induced isomerization of the 11-cis-retinal chromophore in the visual pigment rhodopsin triggers displacement of the second extracellular loop (EL2) and motion of transmembrane helices H5, H6, and H7 leading to the active intermediate metarhodopsin II (Meta II). We describe solid-state NMR measurements of rhodopsin and Meta II that target the molecular contacts in the region of the ionic lock involving these three helices. We show that a contact between Arg135(3.50) and Met257(6.40) forms in Meta II, consistent with the outward rotation of H6 and breaking of the dark-state Glu134(3.49)-Arg135(3.50)-Glu247(6.30) ionic lock. We also show that Tyr223(5.58) and Tyr306(7.53) form molecular contacts with Met257(6.40). Together these results reveal that the crystal structure of opsin in the region of the ionic lock reflects the active state of the receptor. We further demonstrate that Tyr223(5.58) and Ala132(3.47) in Meta II stabilize helix H5 in an active orientation. Mutation of Tyr223(5.58) to phenylalanine or mutation of Ala132(3.47) to leucine decreases the lifetime of the Meta II intermediate. Furthermore, the Y223F mutation is coupled to structural changes in EL2. In contrast, mutation of Tyr306(7.53) to phenylalanine shows only a moderate influence on the Meta II lifetime and is not coupled to EL2.
Collapse
|
30
|
Farrens DL. What site-directed labeling studies tell us about the mechanism of rhodopsin activation and G-protein binding. Photochem Photobiol Sci 2010; 9:1466-74. [PMID: 20967340 DOI: 10.1039/c0pp00283f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Rhodopsin is the photoreceptor protein responsible for dim-light vision in mammals. Due to extensive biophysical, structural and computational analysis of this membrane protein, it is presently the best understood G-protein coupled receptor (GPCR). Here I briefly review one approach that has been extensively used to identify dynamic and structural changes in rhodopsin--the use of site-directed labeling methods (SDL) coupled with electron paramagnetic resonance (EPR) and fluorescence spectroscopy. These SDL studies involve introducing individual cysteine residues into the receptor, then labeling them with cysteine-reactive probes for subsequent analysis by the appropriate spectroscopy. I will give a brief overview of how SDL methods are carried out and how the data is analyzed. Then, I will discuss how SDL studies were carried out on rhodopsin, and how they were used to identify a key structural change that occurs in rhodopsin upon activation--movement of transmembrane helix 6 (TM6). I will also briefly discuss how the SDL studies of rhodopsin compare with SDL studies of other GPCRs, and compare the SDL data with early and recent crystal structures of rhodopsin. Finally, I will discuss why the TM6 movement is required for rhodopsin to couple with the G-protein transducin, and speculate how this mechanism might be a universal method used by all GPCRs to bind G-proteins and perhaps other proteins involved in visual signal transduction, such as arrestin and rhodopsin kinase.
Collapse
Affiliation(s)
- David L Farrens
- Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health & Science University, Portland, Oregon 97239, USA
| |
Collapse
|
31
|
Van Eps N, Anderson LL, Kisselev OG, Baranski TJ, Hubbell WL, Marshall GR. Electron paramagnetic resonance studies of functionally active, nitroxide spin-labeled peptide analogues of the C-terminus of a G-protein alpha subunit. Biochemistry 2010; 49:6877-86. [PMID: 20695526 DOI: 10.1021/bi100846c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The C-terminal tail of the transducin alpha subunit, Gtalpha(340-350), is known to bind and stabilize the active conformation of rhodopsin upon photoactivation (R*). Five spin-labeled analogues of Gtalpha(340-350) demonstrated native-like activity in their ability to bind and stabilize R*. The spin-label 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) was employed at interior sites within the peptide, whereas a Proxyl (3-carboxyl-2,2,5,5-tetramethyl-pyrrolidinyloxy) spin-label was employed at the amino terminus of the peptide. Upon binding to R*, the electron paramagnetic resonance spectrum of TOAC(343)-Gtalpha(340-350) revealed greater immobilization of the nitroxide when compared to that of the N-terminally modified Proxyl-Gtalpha(340-350) analogue. A doubly labeled Proxyl/TOAC(348)-Gtalpha(340-350) was examined by DEER spectrocopy to determine the distribution of distances between the two nitroxides in the peptides when in solution and when bound to R*. TOAC and Proxyl spin-labels in this GPCR-G-protein alpha-peptide system provide unique biophysical probes that can be used to explore the structure and conformational changes at the rhodopsin-G-protein interface.
Collapse
Affiliation(s)
- Ned Van Eps
- Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-7008, USA
| | | | | | | | | | | |
Collapse
|
32
|
Choe HW, Park JH, Kim YJ, Ernst OP. Transmembrane signaling by GPCRs: insight from rhodopsin and opsin structures. Neuropharmacology 2010; 60:52-7. [PMID: 20708633 DOI: 10.1016/j.neuropharm.2010.07.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Revised: 07/21/2010] [Accepted: 07/25/2010] [Indexed: 01/05/2023]
Abstract
G-protein-coupled receptors (GPCRs), also known as seven-transmembrane (7TM) receptors, are the largest family of membrane proteins in the human genome. As versatile signaling molecules, they mediate cellular responses to extracellular signals. Diffusible ligands like hormones and neurotransmitters bind to GPCRs to modulate GPCR activity. An extraordinary and highly specialized GPCR is the photoreceptor rhodopsin which contains the chromophore retinal as its covalently bound ligand. For receptor activation the configuration of retinal is altered by photon absorption. To date, rhodopsin is the only GPCR for which crystal structures of inactive, active and ligand-free conformations are known. Although the photochemical activation is unique to rhodopsin, many mechanistic insights from this receptor can be generalized for GPCRs.
Collapse
Affiliation(s)
- Hui-Woog Choe
- Institut für Medizinische Physik und Biophysik CC2, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.
| | | | | | | |
Collapse
|
33
|
Goncalves JA, Ahuja S, Erfani S, Eilers M, Smith SO. Structure and function of G protein-coupled receptors using NMR spectroscopy. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2010; 57:159-80. [PMID: 20633362 PMCID: PMC2907352 DOI: 10.1016/j.pnmrs.2010.04.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 04/08/2010] [Indexed: 05/15/2023]
Affiliation(s)
- Joseph A Goncalves
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | | | | | | | | |
Collapse
|
34
|
Chillar A, Wu J, Cervantes V, Ruan KH. Structural and Functional Analysis of the C-Terminus of Gαq in Complex with the Human Thromboxane A2 Receptor Provides Evidence of Constitutive Activity. Biochemistry 2010; 49:6365-74. [DOI: 10.1021/bi100047n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Annirudha Chillar
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Jiaxin Wu
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Vanessa Cervantes
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| | - Ke-He Ruan
- Center for Experimental Therapeutics and Pharmacoinformatics, Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77204
| |
Collapse
|
35
|
Chen Y, Wu Y, Henklein P, Li X, Hofmann KP, Nakanishi K, Ernst O. A Photo-Cross-Linking Strategy to Map Sites of Protein-Protein Interactions. Chemistry 2010; 16:7389-94. [DOI: 10.1002/chem.201000441] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
36
|
Kleinau G, Jaeschke H, Worth CL, Mueller S, Gonzalez J, Paschke R, Krause G. Principles and determinants of G-protein coupling by the rhodopsin-like thyrotropin receptor. PLoS One 2010; 5:e9745. [PMID: 20305779 PMCID: PMC2841179 DOI: 10.1371/journal.pone.0009745] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 02/19/2010] [Indexed: 11/23/2022] Open
Abstract
In this study we wanted to gain insights into selectivity mechanisms between G-protein-coupled receptors (GPCR) and different subtypes of G-proteins. The thyrotropin receptor (TSHR) binds G-proteins promiscuously and activates both Gs (cAMP) and Gq (IP). Our goal was to dissect selectivity patterns for both pathways in the intracellular region of this receptor. We were particularly interested in the participation of poorly investigated receptor parts. We systematically investigated the amino acids of intracellular loop (ICL) 1 and helix 8 using site-directed mutagenesis alongside characterization of cAMP and IP accumulation. This approach was guided by a homology model of activated TSHR in complex with heterotrimeric Gq, using the X-ray structure of opsin with a bound G-protein peptide as a structural template. We provide evidence that ICL1 is significantly involved in G-protein activation and our model suggests potential interactions with subunits Gα as well as Gβγ. Several amino acid substitutions impaired both IP and cAMP accumulation. Moreover, we found a few residues in ICL1 (L440, T441, H443) and helix 8 (R687) that are sensitive for Gq but not for Gs activation. Conversely, not even one residue was found that selectively affects cAMP accumulation only. Together with our previous mutagenesis data on ICL2 and ICL3 we provide here the first systematically completed map of potential interfaces between TSHR and heterotrimeric G-protein. The TSHR/Gq-heterotrimer complex is characterized by more selective interactions than the TSHR/Gs complex. In fact the receptor interface for binding Gs is a subset of that for Gq and we postulate that this may be true for other GPCRs coupling these G-proteins. Our findings support that G-protein coupling and preference is dominated by specific structural features at the intracellular region of the activated GPCR but is completed by additional complementary recognition patterns between receptor and G-protein subtypes.
Collapse
Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Holger Jaeschke
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | | | - Sandra Mueller
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Jorge Gonzalez
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Ralf Paschke
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
- * E-mail:
| |
Collapse
|
37
|
Taylor CM, Rockweiler NB, Liu C, Rikimaru L, Tunemalm AK, Kisselev OG, Marshall GR. Using ligand-based virtual screening to allosterically stabilize the activated state of a GPCR. Chem Biol Drug Des 2010; 75:325-32. [PMID: 20659113 DOI: 10.1111/j.1747-0285.2009.00944.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G-protein coupled receptors play an essential role in many biological processes. Despite an increase in the number of solved X-ray crystal structures of G-protein coupled receptors, capturing a G-protein coupled receptor in its activated state for structural analysis has proven to be difficult. An unexplored paradigm is stabilization of one or more conformational states of a G-protein coupled receptor via binding a small molecule to the intracellular loops. A short tetrazole peptidomimetic based on the photoactivated state of rhodopsin-bound structure of Gt(alpha)(340-350) was previously designed and shown to stabilize the photoactivated state of rhodopsin, the G-protein coupled receptor involved in vision. A pharmacophore model derived from the designed tetrazole tetrapeptide was used for ligand-based virtual screening to enhance the possible discovery of novel scaffolds. Maybridge Hitfinder and National Cancer Institute diversity libraries were screened for compounds containing the pharmacophore. Forty-seven compounds resulted from virtually screening the Maybridge library, whereas no hits resulted with the National Cancer Institute library. Three of the 47 Maybridge compounds were found to stabilize the MII state. As these compounds did not inhibit binding of transducin to photoactivated state of rhodopsin, they were assumed to be allosteric ligands. These compounds are potentially useful for crystallographic studies where complexes with these compounds might capture rhodopsin in its activated conformational state.
Collapse
Affiliation(s)
- Christina M Taylor
- Department of Biochemistry and Molecular Biophysics, Washington University, St. Louis, MO 63110, USA
| | | | | | | | | | | | | |
Collapse
|
38
|
Light activation of rhodopsin: insights from molecular dynamics simulations guided by solid-state NMR distance restraints. J Mol Biol 2009; 396:510-27. [PMID: 20004206 DOI: 10.1016/j.jmb.2009.12.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 10/09/2009] [Accepted: 12/02/2009] [Indexed: 11/20/2022]
Abstract
Structural restraints provided by solid-state NMR measurements of the metarhodopsin II intermediate are combined with molecular dynamics simulations to help visualize structural changes in the light activation of rhodopsin. Since the timescale for the formation of the metarhodopsin II intermediate (>1 ms) is beyond that readily accessible by molecular dynamics, we use NMR distance restraints derived from 13C dipolar recoupling measurements to guide the simulations. The simulations yield a working model for how photoisomerization of the 11-cis retinylidene chromophore bound within the interior of rhodopsin is coupled to transmembrane helix motion and receptor activation. The mechanism of activation that emerges is that multiple switches on the extracellular (or intradiscal) side of rhodopsin trigger structural changes that converge to disrupt the ionic lock between helices H3 and H6 on the intracellular side of the receptor.
Collapse
|
39
|
Feuerstein SE, Pulvermüller A, Hartmann R, Granzin J, Stoldt M, Henklein P, Ernst OP, Heck M, Willbold D, Koenig BW. Helix formation in arrestin accompanies recognition of photoactivated rhodopsin. Biochemistry 2009; 48:10733-42. [PMID: 19835414 DOI: 10.1021/bi900544p] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Binding of arrestin to photoactivated phosphorylated rhodopsin terminates the amplification of visual signals in photoreceptor cells. Currently, there is no crystal structure of a rhodopsin-arrestin complex available, although structures of unbound rhodopsin and arrestin have been determined. High-affinity receptor binding is dependent on distinct arrestin sites responsible for recognition of rhodopsin activation and phosphorylation. The loop connecting beta-strands V and VI in rod arrestin has been implicated in the recognition of active rhodopsin. We report the structure of receptor-bound arrestin peptide Arr(67-77) mimicking this loop based on solution NMR data. The peptide binds photoactivated rhodopsin in the unphosphorylated and phosphorylated form with similar affinities and stabilizes the metarhodopsin II photointermediate. A largely alpha-helical conformation of the receptor-bound peptide is observed.
Collapse
Affiliation(s)
- Sophie E Feuerstein
- Department Strukturbiochemie (ISB-3), Institut für Strukturbiologie undBiophysik, Forschungszentrum Jülich, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Kim HJ, Howell SC, Van Horn WD, Jeon YH, Sanders CR. Recent Advances in the Application of Solution NMR Spectroscopy to Multi-Span Integral Membrane Proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2009; 55:335-360. [PMID: 20161395 PMCID: PMC2782866 DOI: 10.1016/j.pnmrs.2009.07.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Affiliation(s)
- Hak Jun Kim
- Korea Polar Research Institute, Korea Ocean Research and Development Institute, Incheon, 406-840, Korea
| | - Stanley C. Howell
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Wade D. Van Horn
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Young Ho Jeon
- Center for Magnetic Resonance, Korea Basic Research Institute, Daejon, 305-333, Korea
| | - Charles R. Sanders
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
- Corresponding Author: ; phone: 615-936-3756; fax: 615-936-2211
| |
Collapse
|
41
|
A G protein-coupled receptor at work: the rhodopsin model. Trends Biochem Sci 2009; 34:540-52. [PMID: 19836958 DOI: 10.1016/j.tibs.2009.07.005] [Citation(s) in RCA: 294] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 07/17/2009] [Accepted: 07/28/2009] [Indexed: 12/17/2022]
Abstract
G protein-coupled receptors (GPCRs) are ubiquitous signal transducers in cell membranes, as well as important drug targets. Interaction with extracellular agonists turns the seven transmembrane helix (7TM) scaffold of a GPCR into a catalyst for GDP and GTP exchange in heterotrimeric Galphabetagamma proteins. Activation of the model GPCR, rhodopsin, is triggered by photoisomerization of its retinal ligand. From the augmentation of biochemical and biophysical studies by recent high-resolution 3D structures, its activation intermediates can now be interpreted as the stepwise engagement of protein domains. Rearrangement of TM5-TM6 opens a crevice at the cytoplasmic side of the receptor into which the C terminus of the Galpha subunit can bind. The Galpha C-terminal helix is used as a transmission rod to the nucleotide binding site. The mechanism relies on dynamic interactions between conserved residues and could therefore be common to other GPCRs.
Collapse
|
42
|
Kofuku Y, Yoshiura C, Ueda T, Terasawa H, Hirai T, Tominaga S, Hirose M, Maeda Y, Takahashi H, Terashima Y, Matsushima K, Shimada I. Structural basis of the interaction between chemokine stromal cell-derived factor-1/CXCL12 and its G-protein-coupled receptor CXCR4. J Biol Chem 2009; 284:35240-50. [PMID: 19837984 DOI: 10.1074/jbc.m109.024851] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The chemokine stromal cell-derived factor-1 (SDF-1/CXCL12) and its G-protein-coupled receptor (GPCR) CXCR4 play fundamental roles in many physiological processes, and CXCR4 is a drug target for various diseases such as cancer metastasis and human immunodeficiency virus, type 1, infection. However, almost no structural information about the SDF-1-CXCR4 interaction is available, mainly because of the difficulties in expression, purification, and crystallization of CXCR4. In this study, an extensive investigation of the preparation of CXCR4 and optimization of the experimental conditions enables NMR analyses of the interaction between the full-length CXCR4 and SDF-1. We demonstrated that the binding of an extended surface on the SDF-1 beta-sheet, 50-s loop, and N-loop to the CXCR4 extracellular region and that of the SDF-1 N terminus to the CXCR4 transmembrane region, which is critical for G-protein signaling, take place independently by methyl-utilizing transferred cross-saturation experiments along with the usage of the CXCR4-selective antagonist AMD3100. Furthermore, based upon the data, we conclude that the highly dynamic SDF-1 N terminus in the 1st step bound state plays a crucial role in efficiently searching the deeply buried binding pocket in the CXCR4 transmembrane region by the "fly-casting" mechanism. This is the first structural analyses of the interaction between a full-length GPCR and its chemokine, and our methodology would be applicable to other GPCR-ligand systems, for which the structural studies are still challenging.
Collapse
Affiliation(s)
- Yutaka Kofuku
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Kapoor N, Menon ST, Chauhan R, Sachdev P, Sakmar TP. Structural evidence for a sequential release mechanism for activation of heterotrimeric G proteins. J Mol Biol 2009; 393:882-97. [PMID: 19703466 DOI: 10.1016/j.jmb.2009.08.043] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2009] [Revised: 08/13/2009] [Accepted: 08/17/2009] [Indexed: 11/18/2022]
Abstract
Heptahelical G-protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors couple to heterotrimeric G proteins to relay extracellular signals to intracellular signaling networks, but the molecular mechanism underlying guanosine 5'-diphosphate (GDP) release by the G protein alpha-subunit is not well understood. Amino acid substitutions in the conserved alpha5 helix of G(i), which extends from the C-terminal region to the nucleotide-binding pocket, cause dramatic increases in basal (receptor-independent) GDP release rates. For example, mutant Galpha(i1)-T329A shows an 18-fold increase in basal GDP release rate and, when expressed in culture, it causes a significant decrease in forskolin-stimulated cAMP accumulation. The crystal structure of Galpha(i1)-T329A.GDP shows substantial conformational rearrangement of the switch I region and additional striking alterations of side chains lining the catalytic pocket that disrupt the Mg(+2) coordination sphere and dislodge bound Mg(+2). We propose a "sequential release" mechanism whereby a transient conformational change in the alpha5 helix alters switch I to induce GDP release. Interestingly, this mechanistic model for heterotrimeric G protein activation is similar to that suggested for the activation of the plant small G protein Rop4 by RopGEF8.
Collapse
Affiliation(s)
- Neeraj Kapoor
- Laboratory of Biochemistry and Molecular Biology, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | | | | | | | | |
Collapse
|
44
|
Structural and kinetic modeling of an activating helix switch in the rhodopsin-transducin interface. Proc Natl Acad Sci U S A 2009; 106:10660-5. [PMID: 19541654 DOI: 10.1073/pnas.0900072106] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular signals prompt G protein-coupled receptors (GPCRs) to adopt an active conformation (R*) and catalyze GDP/GTP exchange in the alpha-subunit of intracellular G proteins (Galphabetagamma). Kinetic analysis of transducin (G(t)alphabetagamma) activation shows that an intermediary R*xG(t)alphabetagamma.GDP complex is formed that precedes GDP release and formation of the nucleotide-free R*xG protein complex. Based on this reaction sequence, we explore the dynamic interface between the proteins during formation of these complexes. We start from the R* conformation stabilized by a G(t)alpha C-terminal peptide (GalphaCT) obtained from crystal structures of the GPCR opsin. Molecular modeling allows reconstruction of the fully elongated C-terminal alpha-helix of G(t)alpha (alpha5) and shows how alpha5 can be docked to the open binding site of R*. Two modes of interaction are found. One of them--termed stable or S-interaction--matches the position of the GalphaCT peptide in the crystal structure and reproduces the hydrogen-bonding networks between the C-terminal reverse turn of GalphaCT and conserved E(D)RY and NPxxY(x)(5,6)F regions of the GPCR. The alternative fit--termed intermediary or I-interaction--is distinguished by a tilt (42 degrees ) and rotation (90 degrees ) of alpha5 relative to the S-interaction and shows different alpha5 contacts with the NPxxY(x)(5,6)F region and the second cytoplasmic loop of R*. From the 2 alpha5 interactions, we derive a "helix switch" mechanism for the transition of R*xG(t)alphabetagamma.GDP to the nucleotide-free R*xG protein complex that illustrates how alpha5 might act as a transmission rod to propagate the conformational change from the receptor-G protein interface to the nucleotide binding site.
Collapse
|
45
|
Scheerer P, Park JH, Hildebrand PW, Kim YJ, Krauss N, Choe HW, Hofmann KP, Ernst OP. Crystal structure of opsin in its G-protein-interacting conformation. Nature 2008; 455:497-502. [PMID: 18818650 DOI: 10.1038/nature07330] [Citation(s) in RCA: 854] [Impact Index Per Article: 53.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 08/08/2008] [Indexed: 12/14/2022]
Abstract
Opsin, the ligand-free form of the G-protein-coupled receptor rhodopsin, at low pH adopts a conformationally distinct, active G-protein-binding state known as Ops*. A synthetic peptide derived from the main binding site of the heterotrimeric G protein-the carboxy terminus of the alpha-subunit (GalphaCT)-stabilizes Ops*. Here we present the 3.2 A crystal structure of the bovine Ops*-GalphaCT peptide complex. GalphaCT binds to a site in opsin that is opened by an outward tilt of transmembrane helix (TM) 6, a pairing of TM5 and TM6, and a restructured TM7-helix 8 kink. Contacts along the inner surface of TM5 and TM6 induce an alpha-helical conformation in GalphaCT with a C-terminal reverse turn. Main-chain carbonyl groups in the reverse turn constitute the centre of a hydrogen-bonded network, which links the two receptor regions containing the conserved E(D)RY and NPxxY(x)(5,6)F motifs. On the basis of the Ops*-GalphaCT structure and known conformational changes in Galpha, we discuss signal transfer from the receptor to the G protein nucleotide-binding site.
Collapse
Affiliation(s)
- Patrick Scheerer
- Institut für Medizinische Physik und Biophysik (CC2), Charité - Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany
| | | | | | | | | | | | | | | |
Collapse
|
46
|
|
47
|
Taylor CM, Barda Y, Kisselev OG, Marshall GR. Modulating G-protein coupled receptor/G-protein signal transduction by small molecules suggested by virtual screening. J Med Chem 2008; 51:5297-303. [PMID: 18707087 DOI: 10.1021/jm800326q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modulation of interactions between activated GPCRs (G-protein coupled receptors) and the intracellular (IC) signal transducers, heterotrimeric G-proteins, is an attractive, yet essentially unexplored, paradigm for treatment of certain diseases. Regulating downstream signaling for treatment of congenital diseases due to constitutively active GPCRs, as well as tumors where GPCRs are often overexpressed, requires the development of new methodologies. Modeling, experimental data, docking, scoring, and experimental testing (MEDSET) was developed to discover inhibitors that target the IC loops of activated GPCRs. As proof-of-concept, MEDSET developed and utilized a model of the interface between photoactivated rhodopsin (R*) and transducin (Gt), its G-protein. A National Cancer Institute (NCI) compound library was screened to identify compounds that bound at the interface between R* and its G-protein. High-scoring compounds from this virtual screen were obtained and tested experimentally for their ability to stabilize R* and prevent Gt from binding to R*. Several compounds that modulate signal transduction have been identified.
Collapse
Affiliation(s)
- Christina M Taylor
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | |
Collapse
|
48
|
Son WJ, Jang S, Shin S. A simple method of estimating sampling consistency based on free energy map distance. J Mol Graph Model 2008; 27:321-5. [PMID: 18619879 DOI: 10.1016/j.jmgm.2008.05.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2008] [Revised: 05/20/2008] [Accepted: 05/23/2008] [Indexed: 11/28/2022]
Abstract
Free energy surfaces, calculated during computer simulations, are known to be useful in characterizing the system of interest such as bio-molecules. However, it is usually very difficult to evaluate free energy from direct simulations, mainly because of high computational costs. Several simulation strategies, including replica exchange method (REM), have been developed to overcome this problem by providing efficient conformational sampling methods. Even with such efficient simulation schemes, fundamental questions concerning simulation convergence still remain to be resolved. In this paper, we propose to use a meta-distance between different free energy surfaces as one of the minimal measures for determining simulation consistency. This method is used for examining free energy surfaces obtained from folding simulations of a synthetic 11-residue protein (1AQG) using REM.
Collapse
Affiliation(s)
- Won-Joon Son
- School of Chemistry, Seoul National University, Seoul 151-747, Republic of Korea
| | | | | |
Collapse
|
49
|
Natochin M, Moussaif M, Artemyev NO. Probing the mechanism of rhodopsin-catalyzed transducin activation. J Neurochem 2008. [DOI: 10.1046/j.1471-4159.2001.00221.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
50
|
Abstract
Heterotrimeric G proteins couple the activation of heptahelical receptors at the cell surface to the intracellular signaling cascades that mediate the physiological responses to extracellular stimuli. G proteins are molecular switches that are activated by receptor-catalyzed GTP for GDP exchange on the G protein alpha subunit, which is the rate-limiting step in the activation of all downstream signaling. Despite the important biological role of the receptor-G protein interaction, relatively little is known about the structure of the complex and how it leads to nucleotide exchange. This chapter will describe what is known about receptor and G protein structure and outline a strategy for assembling the current data into improved models for the receptor-G protein complex that will hopefully answer the question as to how receptors flip the G protein switch.
Collapse
Affiliation(s)
- William M Oldham
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | | |
Collapse
|