1
|
Morea V, Angelucci F, Bellelli A. Is allostery a fuzzy concept? FEBS Open Bio 2024; 14:1040-1056. [PMID: 38783588 PMCID: PMC11216940 DOI: 10.1002/2211-5463.13794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/30/2024] [Accepted: 03/11/2024] [Indexed: 05/25/2024] Open
Abstract
Allostery is an important property of biological macromolecules which regulates diverse biological functions such as catalysis, signal transduction, transport, and molecular recognition. However, the concept was expressed using two different definitions by J. Monod and, over time, more have been added by different authors, making it fuzzy. Here, we reviewed the different meanings of allostery in the current literature and found that it has been used to indicate that the function of a protein is regulated by heterotropic ligands, and/or that the binding of ligands and substrates presents homotropic positive or negative cooperativity, whatever the hypothesized or demonstrated reaction mechanism might be. Thus, proteins defined to be allosteric include not only those that obey the two-state concerted model, but also those that obey different reaction mechanisms such as ligand-induced fit, possibly coupled to sequential structure changes, and ligand-linked dissociation-association. Since each reaction mechanism requires its own mathematical description and is defined by it, there are many possible 'allosteries'. This lack of clarity is made even fuzzier by the fact that the reaction mechanism is often assigned imprecisely and/or implicitly in the absence of the necessary experimental evidence. In this review, we examine a list of proteins that have been defined to be allosteric and attempt to assign a reaction mechanism to as many as possible.
Collapse
Affiliation(s)
- Veronica Morea
- Institute of Molecular Biology and Pathology, CNRRomeItaly
| | - Francesco Angelucci
- Department of Life, Health, and Environmental SciencesUniversity of L'AquilaItaly
| | - Andrea Bellelli
- Department of Biochemical Sciences “A. Rossi Fanelli”Sapienza University of RomeItaly
| |
Collapse
|
2
|
Roy S, Sinha S, Silas AJ, Ghassemian M, Kufareva I, Ghosh P. Growth factor-dependent phosphorylation of Gα i shapes canonical signaling by G protein-coupled receptors. Sci Signal 2024; 17:eade8041. [PMID: 38833528 DOI: 10.1126/scisignal.ade8041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 05/17/2024] [Indexed: 06/06/2024]
Abstract
A long-standing question in the field of signal transduction is how distinct signaling pathways interact with each other to control cell behavior. Growth factor receptors and G protein-coupled receptors (GPCRs) are the two major signaling hubs in eukaryotes. Given that the mechanisms by which they signal independently have been extensively characterized, we investigated how they may cross-talk with each other. Using linear ion trap mass spectrometry and cell-based biophysical, biochemical, and phenotypic assays, we found at least three distinct ways in which epidermal growth factor affected canonical G protein signaling by the Gi-coupled GPCR CXCR4 through the phosphorylation of Gαi. Phosphomimicking mutations in two residues in the αE helix of Gαi (tyrosine-154/tyrosine-155) suppressed agonist-induced Gαi activation while promoting constitutive Gβγ signaling. Phosphomimicking mutations in the P loop (serine-44, serine-47, and threonine-48) suppressed Gi activation entirely, thus completely segregating growth factor and GPCR pathways. As expected, most of the phosphorylation events appeared to affect intrinsic properties of Gαi proteins, including conformational stability, nucleotide binding, and the ability to associate with and to release Gβγ. However, one phosphomimicking mutation, targeting the carboxyl-terminal residue tyrosine-320, promoted mislocalization of Gαi from the plasma membrane, a previously uncharacterized mechanism of suppressing GPCR signaling through G protein subcellular compartmentalization. Together, these findings elucidate not only how growth factor and chemokine signals cross-talk through the phosphorylation-dependent modulation of Gαi but also how such cross-talk may generate signal diversity.
Collapse
Affiliation(s)
- Suchismita Roy
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA 92093, USA
| | - Saptarshi Sinha
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA 92093, USA
| | - Ananta James Silas
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA 92093, USA
| | - Majid Ghassemian
- Department of Chemistry and Biochemistry, Biomolecular and Proteomics Mass Spectrometry Facility, University of California San Diego, San Diego, CA 92093, USA
| | - Irina Kufareva
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA 92093, USA
| | - Pradipta Ghosh
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA 92093, USA
- Department of Medicine, University of California San Diego, San Diego, CA 92093, USA
- Moores Comprehensive Cancer Center, University of California San Diego, San Diego, CA 92093, USA
| |
Collapse
|
3
|
Torres-Rodriguez MD, Lee SG, Roy Choudhury S, Paul R, Selvam B, Shukla D, Jez JM, Pandey S. Structure-function analysis of plant G-protein regulatory mechanisms identifies key Gα-RGS protein interactions. J Biol Chem 2024; 300:107252. [PMID: 38569936 PMCID: PMC11061236 DOI: 10.1016/j.jbc.2024.107252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/20/2024] [Accepted: 03/28/2024] [Indexed: 04/05/2024] Open
Abstract
Heterotrimeric GTP-binding protein alpha subunit (Gα) and its cognate regulator of G-protein signaling (RGS) protein transduce signals in eukaryotes spanning protists, amoeba, animals, fungi, and plants. The core catalytic mechanisms of the GTPase activity of Gα and the interaction interface with RGS for the acceleration of GTP hydrolysis seem to be conserved across these groups; however, the RGS gene is under low selective pressure in plants, resulting in its frequent loss. Our current understanding of the structural basis of Gα:RGS regulation in plants has been shaped by Arabidopsis Gα, (AtGPA1), which has a cognate RGS protein. To gain a comprehensive understanding of this regulation beyond Arabidopsis, we obtained the x-ray crystal structures of Oryza sativa Gα, which has no RGS, and Selaginella moellendorffi (a lycophyte) Gα that has low sequence similarity with AtGPA1 but has an RGS. We show that the three-dimensional structure, protein-protein interaction with RGS, and the dynamic features of these Gα are similar to AtGPA1 and metazoan Gα. Molecular dynamic simulation of the Gα-RGS interaction identifies the contacts established by specific residues of the switch regions of GTP-bound Gα, crucial for this interaction, but finds no significant difference due to specific amino acid substitutions. Together, our data provide valuable insights into the regulatory mechanisms of plant G-proteins but do not support the hypothesis of adaptive co-evolution of Gα:RGS proteins in plants.
Collapse
Affiliation(s)
| | - Soon Goo Lee
- Department of Molecular & Cellular Biology, Kennesaw State University, Kennesaw, Georgia, USA
| | - Swarup Roy Choudhury
- Donald Danforth Plant Science Center, St Louis, Missouri, USA; Department of Biology, Indian Institute of Science Education and Research, Tirupati, India
| | - Rabindranath Paul
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Balaji Selvam
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Joseph M Jez
- Department of Biology, Washington University in St Louis, St Louis, Missouri, USA
| | - Sona Pandey
- Donald Danforth Plant Science Center, St Louis, Missouri, USA.
| |
Collapse
|
4
|
Papasergi-Scott MM, Pérez-Hernández G, Batebi H, Gao Y, Eskici G, Seven AB, Panova O, Hilger D, Casiraghi M, He F, Maul L, Gmeiner P, Kobilka BK, Hildebrand PW, Skiniotis G. Time-resolved cryo-EM of G-protein activation by a GPCR. Nature 2024; 629:1182-1191. [PMID: 38480881 DOI: 10.1038/s41586-024-07153-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 02/02/2024] [Indexed: 03/26/2024]
Abstract
G-protein-coupled receptors (GPCRs) activate heterotrimeric G proteins by stimulating guanine nucleotide exchange in the Gα subunit1. To visualize this mechanism, we developed a time-resolved cryo-EM approach that examines the progression of ensembles of pre-steady-state intermediates of a GPCR-G-protein complex. By monitoring the transitions of the stimulatory Gs protein in complex with the β2-adrenergic receptor at short sequential time points after GTP addition, we identified the conformational trajectory underlying G-protein activation and functional dissociation from the receptor. Twenty structures generated from sequential overlapping particle subsets along this trajectory, compared to control structures, provide a high-resolution description of the order of main events driving G-protein activation in response to GTP binding. Structural changes propagate from the nucleotide-binding pocket and extend through the GTPase domain, enacting alterations to Gα switch regions and the α5 helix that weaken the G-protein-receptor interface. Molecular dynamics simulations with late structures in the cryo-EM trajectory support that enhanced ordering of GTP on closure of the α-helical domain against the nucleotide-bound Ras-homology domain correlates with α5 helix destabilization and eventual dissociation of the G protein from the GPCR. These findings also highlight the potential of time-resolved cryo-EM as a tool for mechanistic dissection of GPCR signalling events.
Collapse
MESH Headings
- Humans
- Binding Sites
- Cryoelectron Microscopy
- GTP-Binding Protein alpha Subunits, Gs/chemistry
- GTP-Binding Protein alpha Subunits, Gs/drug effects
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- GTP-Binding Protein alpha Subunits, Gs/ultrastructure
- Guanosine Triphosphate/metabolism
- Guanosine Triphosphate/pharmacology
- Models, Molecular
- Molecular Dynamics Simulation
- Protein Binding
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/ultrastructure
- Time Factors
- Enzyme Activation/drug effects
- Protein Domains
- Protein Structure, Secondary
- Signal Transduction/drug effects
Collapse
Affiliation(s)
- Makaía M Papasergi-Scott
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Guillermo Pérez-Hernández
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Hossein Batebi
- Institute of Medical Physics and Biophysics, Faculty of Medicine, Leipzig University, Leipzig, Germany
| | - Yang Gao
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Gözde Eskici
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Alpay B Seven
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Ouliana Panova
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
- Institute of Pharmaceutical Chemistry, Philipps-University of Marburg, Marburg, Germany
| | - Marina Casiraghi
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Feng He
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Luis Maul
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Peter W Hildebrand
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
- Institute of Medical Physics and Biophysics, Faculty of Medicine, Leipzig University, Leipzig, Germany
- Berlin Institute of Health at Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
| |
Collapse
|
5
|
Knight KM, Obarow EG, Wei W, Mani S, Esteller MI, Cui M, Ma N, Martin SA, Brinson E, Hewitt N, Soden GM, Logothetis DE, Vaidehi N, Dohlman HG. Molecular annotation of G protein variants in a neurological disorder. Cell Rep 2023; 42:113462. [PMID: 37980565 PMCID: PMC10872635 DOI: 10.1016/j.celrep.2023.113462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 10/04/2023] [Accepted: 11/02/2023] [Indexed: 11/21/2023] Open
Abstract
Heterotrimeric G proteins transduce extracellular chemical messages to generate appropriate intracellular responses. Point mutations in GNAO1, encoding the G protein αo subunit, have been implicated in a pathogenic condition characterized by seizures, movement disorders, intellectual disability, and developmental delay (GNAO1 disorder). However, the effects of these mutations on G protein structure and function are unclear. Here, we report the effects of 55 mutations on Gαo conformation, thermostability, nucleotide binding, and hydrolysis, as well as interaction with Gβγ subunits, receptors, and effectors. Our effort reveals four functionally distinct groups of mutants, including one group that sequesters receptors and another that sequesters Gβγ, both acting in a genetically dominant manner. These findings provide a more comprehensive understanding of disease-relevant mutations and reveal that GNAO1 disorder is likely composed of multiple mechanistically distinct disorders that will likely require multiple therapeutic strategies.
Collapse
Affiliation(s)
- Kevin M Knight
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Elizabeth G Obarow
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Wenyuan Wei
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
| | - Sepehr Mani
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA
| | - Maria I Esteller
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA
| | - Ning Ma
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
| | - Sarah A Martin
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Emily Brinson
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Natalie Hewitt
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Gaby M Soden
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA.
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
| | - Henrik G Dohlman
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| |
Collapse
|
6
|
Park JC, Luebbers A, Dao M, Semeano A, Nguyen AM, Papakonstantinou MP, Broselid S, Yano H, Martemyanov KA, Garcia-Marcos M. Fine-tuning GPCR-mediated neuromodulation by biasing signaling through different G protein subunits. Mol Cell 2023; 83:2540-2558.e12. [PMID: 37390816 PMCID: PMC10527995 DOI: 10.1016/j.molcel.2023.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/28/2023] [Accepted: 06/02/2023] [Indexed: 07/02/2023]
Abstract
G-protein-coupled receptors (GPCRs) mediate neuromodulation through the activation of heterotrimeric G proteins (Gαβγ). Classical models depict that G protein activation leads to a one-to-one formation of Gα-GTP and Gβγ species. Each of these species propagates signaling by independently acting on effectors, but the mechanisms by which response fidelity is ensured by coordinating Gα and Gβγ responses remain unknown. Here, we reveal a paradigm of G protein regulation whereby the neuronal protein GINIP (Gα inhibitory interacting protein) biases inhibitory GPCR responses to favor Gβγ over Gα signaling. Tight binding of GINIP to Gαi-GTP precludes its association with effectors (adenylyl cyclase) and, simultaneously, with regulator-of-G-protein-signaling (RGS) proteins that accelerate deactivation. As a consequence, Gαi-GTP signaling is dampened, whereas Gβγ signaling is enhanced. We show that this mechanism is essential to prevent the imbalances of neurotransmission that underlie increased seizure susceptibility in mice. Our findings reveal an additional layer of regulation within a quintessential mechanism of signal transduction that sets the tone of neurotransmission.
Collapse
Affiliation(s)
- Jong-Chan Park
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, MA 02118, USA
| | - Alex Luebbers
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, MA 02118, USA
| | - Maria Dao
- U.F. Scripps Biomedical Research, University of Florida, Jupiter, FL 33458, USA
| | - Ana Semeano
- Department of Pharmaceutical Sciences, Center for Drug Discovery, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, USA
| | - Anh Minh Nguyen
- Department of Pharmaceutical Sciences, Center for Drug Discovery, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, USA
| | - Maria P Papakonstantinou
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, MA 02118, USA
| | - Stefan Broselid
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, MA 02118, USA
| | - Hideaki Yano
- Department of Pharmaceutical Sciences, Center for Drug Discovery, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, USA
| | | | - Mikel Garcia-Marcos
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, MA 02118, USA; Department of Biology, College of Arts & Sciences, Boston University, Boston, MA 02115, USA.
| |
Collapse
|
7
|
Papasergi-Scott MM, Kwarcinski FE, Yu M, Panova O, Ovrutsky AM, Skiniotis G, Tall GG. Structures of Ric-8B in complex with Gα protein folding clients reveal isoform specificity mechanisms. Structure 2023; 31:553-564.e7. [PMID: 36931277 PMCID: PMC10164081 DOI: 10.1016/j.str.2023.02.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 01/23/2023] [Accepted: 02/20/2023] [Indexed: 03/18/2023]
Abstract
Mammalian Ric-8 proteins act as chaperones to regulate the cellular abundance of heterotrimeric G protein α subunits. The Ric-8A isoform chaperones Gαi/o, Gα12/13, and Gαq/11 subunits, while Ric-8B acts on Gαs/olf subunits. Here, we determined cryoelectron microscopy (cryo-EM) structures of Ric-8B in complex with Gαs and Gαolf, revealing isoform differences in the relative positioning and contacts between the C-terminal α5 helix of Gα within the concave pocket formed by Ric-8 α-helical repeat elements. Despite the overall architectural similarity with our earlier structures of Ric-8A complexed to Gαq and Gαi1, Ric-8B distinctly accommodates an extended loop found only in Gαs/olf proteins. The structures, along with results from Ric-8 protein thermal stability assays and cell-based Gαolf folding assays, support a requirement for the Gα C-terminal region for binding specificity, and highlight that multiple structural elements impart specificity for Ric-8/G protein binding.
Collapse
Affiliation(s)
- Makaía M Papasergi-Scott
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Frank E Kwarcinski
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA
| | - Maiya Yu
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA
| | - Ouliana Panova
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ann M Ovrutsky
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA
| | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Gregory G Tall
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA.
| |
Collapse
|
8
|
Papasergi-Scott MM, Pérez-Hernández G, Batebi H, Gao Y, Eskici G, Seven AB, Panova O, Hilger D, Casiraghi M, He F, Maul L, Gmeiner P, Kobilka BK, Hildebrand PW, Skiniotis G. Time-resolved cryo-EM of G protein activation by a GPCR. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.20.533387. [PMID: 36993214 PMCID: PMC10055275 DOI: 10.1101/2023.03.20.533387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
G protein-coupled receptors (GPCRs) activate heterotrimeric G proteins by stimulating the exchange of guanine nucleotide in the Gα subunit. To visualize this mechanism, we developed a time-resolved cryo-EM approach that examines the progression of ensembles of pre-steady-state intermediates of a GPCR-G protein complex. Using variability analysis to monitor the transitions of the stimulatory Gs protein in complex with the β 2 -adrenergic receptor (β 2 AR) at short sequential time points after GTP addition, we identified the conformational trajectory underlying G protein activation and functional dissociation from the receptor. Twenty transition structures generated from sequential overlapping particle subsets along this trajectory, compared to control structures, provide a high-resolution description of the order of events driving G protein activation upon GTP binding. Structural changes propagate from the nucleotide-binding pocket and extend through the GTPase domain, enacting alterations to Gα Switch regions and the α5 helix that weaken the G protein-receptor interface. Molecular dynamics (MD) simulations with late structures in the cryo-EM trajectory support that enhanced ordering of GTP upon closure of the alpha-helical domain (AHD) against the nucleotide-bound Ras-homology domain (RHD) correlates with irreversible α5 helix destabilization and eventual dissociation of the G protein from the GPCR. These findings also highlight the potential of time-resolved cryo-EM as a tool for mechanistic dissection of GPCR signaling events.
Collapse
|
9
|
Jiang H, Galtes D, Wang J, Rockman HA. G protein-coupled receptor signaling: transducers and effectors. Am J Physiol Cell Physiol 2022; 323:C731-C748. [PMID: 35816644 PMCID: PMC9448338 DOI: 10.1152/ajpcell.00210.2022] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/27/2022] [Accepted: 07/10/2022] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are of considerable interest due to their importance in a wide range of physiological functions and in a large number of Food and Drug Administration (FDA)-approved drugs as therapeutic entities. With continued study of their function and mechanism of action, there is a greater understanding of how effector molecules interact with a receptor to initiate downstream effector signaling. This review aims to explore the signaling pathways, dynamic structures, and physiological relevance in the cardiovascular system of the three most important GPCR signaling effectors: heterotrimeric G proteins, GPCR kinases (GRKs), and β-arrestins. We will first summarize their prominent roles in GPCR pharmacology before transitioning into less well-explored areas. As new technologies are developed and applied to studying GPCR structure and their downstream effectors, there is increasing appreciation for the elegance of the regulatory mechanisms that mediate intracellular signaling and function.
Collapse
Affiliation(s)
- Haoran Jiang
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
| | - Daniella Galtes
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
| | - Jialu Wang
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
| | - Howard A Rockman
- Department of Medicine, Duke University Medical Center, Durham, North Carolina
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina
| |
Collapse
|
10
|
Bongirwar V, Mokhade AS. Different methods, techniques and their limitations in protein structure prediction: A review. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2022; 173:72-82. [PMID: 35588858 DOI: 10.1016/j.pbiomolbio.2022.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 04/16/2022] [Accepted: 05/11/2022] [Indexed: 11/17/2022]
Abstract
Because of the increase in different types of diseases in human habitats, demands for designing various types of drugs are also increasing. Protein and its structure play a very important role in drug design. Therefore researchers from different areas like mathematics, medicines, and computer science are teaming up for getting better solutions in the said field. In this paper, we have discussed different methods of secondary and tertiary protein structure prediction (PSP), along with the limitations of different approaches. Different types of datasets used in PSP are also discussed here. This paper also tells about different performance measures to evaluate the prediction accuracy of PSP methods. Different software's/servers are available for download, which are used to find the protein structures for the input protein sequence. These softwares will also help to compare the performance of any new algorithm with other available methods. Details of those softwares are also mentioned in this paper.
Collapse
Affiliation(s)
| | - A S Mokhade
- Visvesvaraya National Institute of Technology, Nagpur, India
| |
Collapse
|
11
|
Nubbemeyer B, Pepanian A, Paul George AA, Imhof D. Strategies towards Targeting Gαi/s Proteins: Scanning of Protein-Protein Interaction Sites To Overcome Inaccessibility. ChemMedChem 2021; 16:1696-1715. [PMID: 33615736 PMCID: PMC8252600 DOI: 10.1002/cmdc.202100039] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Indexed: 12/16/2022]
Abstract
Heterotrimeric G proteins are classified into four subfamilies and play a key role in signal transduction. They transmit extracellular signals to intracellular effectors subsequent to the activation of G protein-coupled receptors (GPCRs), which are targeted by over 30 % of FDA-approved drugs. However, addressing G proteins as drug targets represents a compelling alternative, for example, when G proteins act independently of the corresponding GPCRs, or in cases of complex multifunctional diseases, when a large number of different GPCRs are involved. In contrast to Gαq, efforts to target Gαi/s by suitable chemical compounds has not been successful so far. Here, a comprehensive analysis was conducted examining the most important interface regions of Gαi/s with its upstream and downstream interaction partners. By assigning the existing compounds and the performed approaches to the respective interfaces, the druggability of the individual interfaces was ranked to provide perspectives for selective targeting of Gαi/s in the future.
Collapse
Affiliation(s)
- Britta Nubbemeyer
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
| | - Anna Pepanian
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
| | | | - Diana Imhof
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
| |
Collapse
|
12
|
Polit A, Mystek P, Błasiak E. Every Detail Matters. That Is, How the Interaction between Gα Proteins and Membrane Affects Their Function. MEMBRANES 2021; 11:222. [PMID: 33804791 PMCID: PMC8003949 DOI: 10.3390/membranes11030222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 11/16/2022]
Abstract
In highly organized multicellular organisms such as humans, the functions of an individual cell are dependent on signal transduction through G protein-coupled receptors (GPCRs) and subsequently heterotrimeric G proteins. As most of the elements belonging to the signal transduction system are bound to lipid membranes, researchers are showing increasing interest in studying the accompanying protein-lipid interactions, which have been demonstrated to not only provide the environment but also regulate proper and efficient signal transduction. The mode of interaction between the cell membrane and G proteins is well known. Despite this, the recognition mechanisms at the molecular level and how the individual G protein-membrane attachment signals are interrelated in the process of the complex control of membrane targeting of G proteins remain unelucidated. This review focuses on the mechanisms by which mammalian Gα subunits of G proteins interact with lipids and the factors responsible for the specificity of membrane association. We summarize recent data on how these signaling proteins are precisely targeted to a specific site in the membrane region by introducing well-defined modifications as well as through the presence of polybasic regions within these proteins and interactions with other components of the heterocomplex.
Collapse
Affiliation(s)
- Agnieszka Polit
- Department of Physical Biochemistry, Faculty of Biochemistry Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland; (P.M.); (E.B.)
| | | | | |
Collapse
|
13
|
Knight KM, Ghosh S, Campbell SL, Lefevre TJ, Olsen RHJ, Smrcka AV, Valentin NH, Yin G, Vaidehi N, Dohlman HG. A universal allosteric mechanism for G protein activation. Mol Cell 2021; 81:1384-1396.e6. [PMID: 33636126 DOI: 10.1016/j.molcel.2021.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 12/01/2020] [Accepted: 01/29/2021] [Indexed: 12/11/2022]
Abstract
G proteins play a central role in signal transduction and pharmacology. Signaling is initiated by cell-surface receptors, which promote guanosine triphosphate (GTP) binding and dissociation of Gα from the Gβγ subunits. Structural studies have revealed the molecular basis of subunit association with receptors, RGS proteins, and downstream effectors. In contrast, the mechanism of subunit dissociation is poorly understood. We use cell signaling assays, molecular dynamics (MD) simulations, and biochemistry and structural analyses to identify a conserved network of amino acids that dictates subunit release. In the presence of the terminal phosphate of GTP, a glycine forms a polar network with an arginine and glutamate, putting torsional strain on the subunit binding interface. This "G-R-E motif" secures GTP and, through an allosteric link, discharges the Gβγ dimer. Replacement of network residues prevents subunit dissociation regardless of agonist or GTP binding. These findings reveal the molecular basis of the final committed step of G protein activation.
Collapse
Affiliation(s)
- Kevin M Knight
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Soumadwip Ghosh
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
| | - Sharon L Campbell
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Tyler J Lefevre
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Reid H J Olsen
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alan V Smrcka
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Natalie H Valentin
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Guowei Yin
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
| | - Henrik G Dohlman
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| |
Collapse
|
14
|
Calebiro D, Koszegi Z, Lanoiselée Y, Miljus T, O'Brien S. G protein-coupled receptor-G protein interactions: a single-molecule perspective. Physiol Rev 2020; 101:857-906. [PMID: 33331229 DOI: 10.1152/physrev.00021.2020] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
G protein-coupled receptors (GPCRs) regulate many cellular and physiological processes, responding to a diverse range of extracellular stimuli including hormones, neurotransmitters, odorants, and light. Decades of biochemical and pharmacological studies have provided fundamental insights into the mechanisms of GPCR signaling. Thanks to recent advances in structural biology, we now possess an atomistic understanding of receptor activation and G protein coupling. However, how GPCRs and G proteins interact in living cells to confer signaling efficiency and specificity remains insufficiently understood. The development of advanced optical methods, including single-molecule microscopy, has provided the means to study receptors and G proteins in living cells with unprecedented spatio-temporal resolution. The results of these studies reveal an unexpected level of complexity, whereby GPCRs undergo transient interactions among themselves as well as with G proteins and structural elements of the plasma membrane to form short-lived signaling nanodomains that likely confer both rapidity and specificity to GPCR signaling. These findings may provide new strategies to pharmaceutically modulate GPCR function, which might eventually pave the way to innovative drugs for common diseases such as diabetes or heart failure.
Collapse
Affiliation(s)
- Davide Calebiro
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Zsombor Koszegi
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Yann Lanoiselée
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Tamara Miljus
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Shannon O'Brien
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| |
Collapse
|
15
|
McClelland LJ, Zhang K, Mou TC, Johnston J, Yates-Hansen C, Li S, Thomas CJ, Doukov TI, Triest S, Wohlkonig A, Tall GG, Steyaert J, Chiu W, Sprang SR. Structure of the G protein chaperone and guanine nucleotide exchange factor Ric-8A bound to Gαi1. Nat Commun 2020; 11:1077. [PMID: 32103024 PMCID: PMC7044438 DOI: 10.1038/s41467-020-14943-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Accepted: 02/10/2020] [Indexed: 12/24/2022] Open
Abstract
Ric-8A is a cytosolic Guanine Nucleotide exchange Factor (GEF) that activates heterotrimeric G protein alpha subunits (Gα) and serves as an essential Gα chaperone. Mechanisms by which Ric-8A catalyzes these activities, which are stimulated by Casein Kinase II phosphorylation, are unknown. We report the structure of the nanobody-stabilized complex of nucleotide-free Gα bound to phosphorylated Ric-8A at near atomic resolution by cryo-electron microscopy and X-ray crystallography. The mechanism of Ric-8A GEF activity differs considerably from that employed by G protein-coupled receptors at the plasma membrane. Ric-8A engages a specific conformation of Gα at multiple interfaces to form a complex that is stabilized by phosphorylation within a Ric-8A segment that connects two Gα binding sites. The C-terminus of Gα is ejected from its beta sheet core, thereby dismantling the GDP binding site. Ric-8A binds to the exposed Gα beta sheet and switch II to stabilize the nucleotide-free state of Gα.
Collapse
Affiliation(s)
- Levi J McClelland
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA
| | - Kaiming Zhang
- Department of Bioengineering and James H. Clark Center, Stanford University, Stanford, CA, 94305, USA
| | - Tung-Chung Mou
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA
- Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA
| | - Jake Johnston
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA
- Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA
| | - Cindee Yates-Hansen
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA
| | - Shanshan Li
- Department of Bioengineering and James H. Clark Center, Stanford University, Stanford, CA, 94305, USA
| | - Celestine J Thomas
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA
- Regeneron Pharmaceutical, Inc., Tarrytown, NY, USA
| | - Tzanko I Doukov
- Macromolecular Crystallography Group, Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, 94025, USA
| | - Sarah Triest
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Alexandre Wohlkonig
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Gregory G Tall
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Wah Chiu
- Department of Bioengineering and James H. Clark Center, Stanford University, Stanford, CA, 94305, USA.
- Biosciences Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA.
| | - Stephen R Sprang
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, 59812, USA.
- Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA.
- Graduate Program in Biochemistry and Biophysics, University of Montana, Missoula, MT, 59812, USA.
| |
Collapse
|
16
|
Fonin AV, Darling AL, Kuznetsova IM, Turoverov KK, Uversky VN. Multi-functionality of proteins involved in GPCR and G protein signaling: making sense of structure-function continuum with intrinsic disorder-based proteoforms. Cell Mol Life Sci 2019; 76:4461-4492. [PMID: 31428838 PMCID: PMC11105632 DOI: 10.1007/s00018-019-03276-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 08/05/2019] [Accepted: 08/12/2019] [Indexed: 12/21/2022]
Abstract
GPCR-G protein signaling system recognizes a multitude of extracellular ligands and triggers a variety of intracellular signaling cascades in response. In humans, this system includes more than 800 various GPCRs and a large set of heterotrimeric G proteins. Complexity of this system goes far beyond a multitude of pair-wise ligand-GPCR and GPCR-G protein interactions. In fact, one GPCR can recognize more than one extracellular signal and interact with more than one G protein. Furthermore, one ligand can activate more than one GPCR, and multiple GPCRs can couple to the same G protein. This defines an intricate multifunctionality of this important signaling system. Here, we show that the multifunctionality of GPCR-G protein system represents an illustrative example of the protein structure-function continuum, where structures of the involved proteins represent a complex mosaic of differently folded regions (foldons, non-foldons, unfoldons, semi-foldons, and inducible foldons). The functionality of resulting highly dynamic conformational ensembles is fine-tuned by various post-translational modifications and alternative splicing, and such ensembles can undergo dramatic changes at interaction with their specific partners. In other words, GPCRs and G proteins exist as sets of conformational/basic, inducible/modified, and functioning proteoforms characterized by a broad spectrum of structural features and possessing various functional potentials.
Collapse
Affiliation(s)
- Alexander V Fonin
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
| | - April L Darling
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Irina M Kuznetsova
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
| | - Konstantin K Turoverov
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
- Department of Biophysics, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya av. 29, St. Petersburg, 195251, Russian Federation
| | - Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
- Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow, Russian Federation.
| |
Collapse
|
17
|
Draper-Joyce C, Furness SGB. Conformational Transitions and the Activation of Heterotrimeric G Proteins by G Protein-Coupled Receptors. ACS Pharmacol Transl Sci 2019; 2:285-290. [PMID: 32259062 PMCID: PMC7088962 DOI: 10.1021/acsptsci.9b00054] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Indexed: 01/10/2023]
Abstract
G protein-coupled receptors (GPCRs) are particularly attractive targets for therapeutic pharmaceuticals. This is because they are involved in almost all facets of physiology, in many pathophysiological processes, they are tractable due to their cell surface location, and can exhibit highly textured pharmacology. While the development of new drugs does not require the molecular details of the mechanism of activity for a particular target, there has been increasing interest in the GPCR field in these details. In part, this has come with the recognition that differential activity at a particular target might be a way in which to leverage drug activity, either through manipulation of efficacy or through differential coupling (signaling bias). To this end, the past few years have seen a number of publications that have specifically attempted to address one or more aspects of the molecular reaction pathway, leading to activation of heterotrimeric G proteins by GPCRs.
Collapse
|
18
|
Najor M, Leverson BD, Goossens JL, Kothawala S, Olsen KW, Mota de Freitas D. Folding of G α Subunits: Implications for Disease States. ACS OMEGA 2018; 3:12320-12329. [PMID: 30411001 PMCID: PMC6210069 DOI: 10.1021/acsomega.8b01174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/18/2018] [Indexed: 06/08/2023]
Abstract
G-proteins play a central role in signal transduction by fluctuating between "on" and "off" phases that are determined by a conformational change. cAMP is a secondary messenger whose formation is inhibited or stimulated by activated Giα1 or Gsα subunit. We used tryptophan fluorescence, UV/vis spectrophotometry, and circular dichroism to probe distinct structural features within active and inactive conformations from wild-type and tryptophan mutants of Giα1 and Gsα. For all proteins studied, we found that the active conformations were more stable than the inactive conformations, and upon refolding from higher temperatures, activated wild-type subunits recovered significantly more native structure. We also observed that the wild-type subunits partially regained the ability to bind nucleotide. The increased compactness observed upon activation was consistent with the calculated decrease in solvent accessible surface area for wild-type Giα1. We found that as the temperature increased, Gα subunits, which are known to be rich in α-helices, converted to proteins with increased content of β-sheets and random coil. For active conformations from wild-type and tryptophan mutants of Giα1, melting temperatures indicated that denaturation starts around hydrophobic tryptophan microenvironments and then radiates toward tyrosine residues at the surface, followed by alteration of the secondary structure. For Gsα, however, disruption of secondary structure preceded unfolding around tyrosine residues. In the active conformations, a π-cation interaction between essential arginine and tryptophan residues, which was characterized by a fluorescence-measured red shift and modeled by molecular dynamics, was also shown to be a contributor to the stability of Gα subunits. The folding properties of Gα subunits reported here are discussed in the context of diseases associated to G-proteins.
Collapse
|
19
|
Maeda S, Koehl A, Matile H, Hu H, Hilger D, Schertler GFX, Manglik A, Skiniotis G, Dawson RJP, Kobilka BK. Development of an antibody fragment that stabilizes GPCR/G-protein complexes. Nat Commun 2018; 9:3712. [PMID: 30213947 PMCID: PMC6137068 DOI: 10.1038/s41467-018-06002-w] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 07/25/2018] [Indexed: 11/10/2022] Open
Abstract
Single-particle cryo-electron microscopy (cryo-EM) has recently enabled high-resolution structure determination of numerous biological macromolecular complexes. Despite this progress, the application of high-resolution cryo-EM to G protein coupled receptors (GPCRs) in complex with heterotrimeric G proteins remains challenging, owning to both the relative small size and the limited stability of these assemblies. Here we describe the development of antibody fragments that bind and stabilize GPCR-G protein complexes for the application of high-resolution cryo-EM. One antibody in particular, mAb16, stabilizes GPCR/G-protein complexes by recognizing an interface between Gα and Gβγ subunits in the heterotrimer, and confers resistance to GTPγS-triggered dissociation. The unique recognition mode of this antibody makes it possible to transfer its binding and stabilizing effect to other G-protein subtypes through minimal protein engineering. This antibody fragment is thus a broadly applicable tool for structural studies of GPCR/G-protein complexes. The determination of high resolution structures of G protein coupled receptors (GPCRs) in complex with heterotrimeric G proteins is challenging. Here authors develop an antibody fragment, mAB16, which stabilizes GPCR/G-protein complexes and facilitates the application of high resolution cryo-EM.
Collapse
Affiliation(s)
- Shoji Maeda
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA
| | - Antoine Koehl
- Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA
| | - Hugues Matile
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F.Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Hongli Hu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA
| | - Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA
| | - Gebhard F X Schertler
- Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232, Villigen, Switzerland
| | - Aashish Manglik
- Department of Pharmaceutical Chemistry, University of California San Francisco, 1700 4th Street, San Francisco, CA, 94143, USA.,Department of Anesthesia and Perioperative Care, University of California San Francisco, 1700 4th Street, San Francisco, CA, 94143, USA
| | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA
| | - Roger J P Dawson
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F.Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland.
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, 94305, USA.
| |
Collapse
|
20
|
Interplay between negative and positive design elements in Gα helical domains of G proteins determines interaction specificity toward RGS2. Biochem J 2018; 475:2293-2304. [PMID: 29925530 DOI: 10.1042/bcj20180285] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/18/2018] [Accepted: 06/19/2018] [Indexed: 01/26/2023]
Abstract
Regulators of G protein signaling (RGS) proteins inactivate Gα subunits, thereby controlling G protein-coupled signaling networks. Among all RGS proteins, RGS2 is unique in interacting only with the Gαq but not with the Gαi subfamily. Previous studies suggested that this specificity is determined by the RGS domain and, in particular, by three RGS2-specific residues that lead to a unique mode of interaction with Gαq This interaction was further proposed to act through contacts with the Gα GTPase domain. Here, we combined energy calculations and GTPase activity measurements to determine which Gα residues dictate specificity toward RGS2. We identified putative specificity-determining residues in the Gα helical domain, which among G proteins is found only in Gα subunits. Replacing these helical domain residues in Gαi with their Gαq counterparts resulted in a dramatic specificity switch toward RGS2. We further show that Gα-RGS2 specificity is set by Gαi residues that perturb interactions with RGS2, and by Gαq residues that enhance these interactions. These results show, for the first time, that the Gα helical domain is central to dictating specificity toward RGS2, suggesting that this domain plays a general role in governing Gα-RGS specificity. Our insights provide new options for manipulating RGS-G protein interactions in vivo, for better understanding of their 'wiring' into signaling networks, and for devising novel drugs targeting such interactions.
Collapse
|
21
|
Asli A, Sadiya I, Avital-Shacham M, Kosloff M. “Disruptor” residues in the regulator of G protein signaling (RGS) R12 subfamily attenuate the inactivation of Gα subunits. Sci Signal 2018; 11:11/534/eaan3677. [DOI: 10.1126/scisignal.aan3677] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
22
|
Disease-Causing Mutations in the G Protein Gαs Subvert the Roles of GDP and GTP. Cell 2018; 173:1254-1264.e11. [PMID: 29628140 DOI: 10.1016/j.cell.2018.03.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 01/23/2018] [Accepted: 03/07/2018] [Indexed: 12/17/2022]
Abstract
The single most frequent cancer-causing mutation across all heterotrimeric G proteins is R201C in Gαs. The current model explaining the gain-of-function activity of the R201 mutations is through the loss of GTPase activity and resulting inability to switch off to the GDP state. Here, we find that the R201C mutation can bypass the need for GTP binding by directly activating GDP-bound Gαs through stabilization of an intramolecular hydrogen bond network. Having found that a gain-of-function mutation can convert GDP into an activator, we postulated that a reciprocal mutation might disrupt the normal role of GTP. Indeed, we found R228C, a loss-of-function mutation in Gαs that causes pseudohypoparathyroidism type 1a (PHP-Ia), compromised the adenylyl cyclase-activating activity of Gαs bound to a non-hydrolyzable GTP analog. These findings show that disease-causing mutations in Gαs can subvert the canonical roles of GDP and GTP, providing new insights into the regulation mechanism of G proteins.
Collapse
|
23
|
Sebastiani G, Ceccarelli E, Castagna MG, Dotta F. G-protein-coupled receptors (GPCRs) in the treatment of diabetes: Current view and future perspectives. Best Pract Res Clin Endocrinol Metab 2018; 32:201-213. [PMID: 29678286 DOI: 10.1016/j.beem.2018.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
G-protein coupled receptors (GPCRs) represent the largest receptor family in the genome and are of great interest for the design of novel drugs in a wide variety of diseases including neurologic disorders, obesity and Type 2 diabetes mellitus. The latter is a chronic disease characterized by insulin resistance and impaired insulin secretion, affecting >400 million patients worldwide. Here we provide an overview on: a) The molecular basis of GPCR signalling and of its involvement in the regulation of insulin secretion and of glucose homeostasis; b) the role of GPCRs in type 2 diabetes pathophysiology and as therapeutic targets of current and future glucose-lowering drugs.
Collapse
Affiliation(s)
- Guido Sebastiani
- Department of Medicine, Surgery and Neurosciences, University of Siena, Italy; Fondazione Umberto Di Mario ONLUS c/o Toscana Life Science, Siena, Italy
| | - Elena Ceccarelli
- Department of Medicine, Surgery and Neurosciences, University of Siena, Italy
| | | | - Francesco Dotta
- Department of Medicine, Surgery and Neurosciences, University of Siena, Italy; Fondazione Umberto Di Mario ONLUS c/o Toscana Life Science, Siena, Italy.
| |
Collapse
|
24
|
Senarath K, Kankanamge D, Samaradivakara S, Ratnayake K, Tennakoon M, Karunarathne A. Regulation of G Protein βγ Signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2018; 339:133-191. [PMID: 29776603 DOI: 10.1016/bs.ircmb.2018.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Heterotrimeric guanine nucleotide-binding proteins (G proteins) deliver external signals to the cell interior, upon activation by the external signal stimulated G protein-coupled receptors (GPCRs).While the activated GPCRs control several pathways independently, activated G proteins control the vast majority of cellular and physiological functions, ranging from vision to cardiovascular homeostasis. Activated GPCRs dissociate GαGDPβγ heterotrimer into GαGTP and free Gβγ. Earlier, GαGTP was recognized as the primary signal transducer of the pathway and Gβγ as a passive signaling modality that facilitates the activity of Gα. However, Gβγ later found to regulate more number of pathways than GαGTP does. Once liberated from the heterotrimer, free Gβγ interacts and activates a diverse range of signaling regulators including kinases, lipases, GTPases, and ion channels, and it does not require any posttranslation modifications. Gβγ family consists of 48 members, which show cell- and tissue-specific expressions, and recent reports show that cells employ the subtype diversity in Gβγ to achieve desired signaling outcomes. In addition to activated GPCRs, which induce free Gβγ generation and the rate of GTP hydrolysis in Gα, which sequester Gβγ in the heterotrimer, terminating Gβγ signaling, additional regulatory mechanisms exist to regulate Gβγ activity. In this chapter, we discuss structure and function, subtype diversity and its significance in signaling regulation, effector activation, regulatory mechanisms as well as the disease relevance of Gβγ in eukaryotes.
Collapse
|
25
|
DiGiacomo V, de Opakua AI, Papakonstantinou MP, Nguyen LT, Merino N, Blanco-Canosa JB, Blanco FJ, Garcia-Marcos M. The Gαi-GIV binding interface is a druggable protein-protein interaction. Sci Rep 2017; 7:8575. [PMID: 28819150 PMCID: PMC5561080 DOI: 10.1038/s41598-017-08829-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/12/2017] [Indexed: 01/26/2023] Open
Abstract
Heterotrimeric G proteins are usually activated by the guanine-nucleotide exchange factor (GEF) activity of GPCRs. However, some non-receptor proteins are also GEFs. GIV (a.k.a Girdin) was the first non-receptor protein for which the GEF activity was ascribed to a well-defined protein sequence that directly binds Gαi. GIV expression promotes metastasis and disruption of its binding to Gαi blunts the pro-metastatic behavior of cancer cells. Although this suggests that inhibition of the Gαi-GIV interaction is a promising therapeutic strategy, protein-protein interactions (PPIs) are considered poorly "druggable" targets requiring case-by-case validation. Here, we set out to investigate whether Gαi-GIV is a druggable PPI. We tested a collection of >1,000 compounds on the Gαi-GIV PPI by in silico ligand screening and separately by a chemical high-throughput screening (HTS) assay. Two hits, ATA and NF023, obtained in both screens were confirmed in secondary HTS and low-throughput assays. The binding site of NF023, identified by NMR spectroscopy and biochemical assays, overlaps with the Gαi-GIV interface. Importantly, NF023 did not disrupt Gαi-Gβγ binding, indicating its specificity toward Gαi-GIV. This work establishes the Gαi-GIV PPI as a druggable target and sets the conceptual and technical framework for the discovery of novel inhibitors of this PPI.
Collapse
Affiliation(s)
- Vincent DiGiacomo
- Department of Biochemistry, Boston University School of Medicine, Boston, USA
| | | | | | - Lien T Nguyen
- Department of Biochemistry, Boston University School of Medicine, Boston, USA
| | | | - Juan B Blanco-Canosa
- Department of Chemistry and Molecular Pharmacology, IRB Barcelona, Barcelona, Spain
| | - Francisco J Blanco
- CIC-BioGune, Derio, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Mikel Garcia-Marcos
- Department of Biochemistry, Boston University School of Medicine, Boston, USA.
| |
Collapse
|
26
|
Nanosecond Dynamics of Gαi1 Bound to Nucleotides or Ric-8A, a Gα Chaperone with GEF Activity. Biophys J 2017; 111:722-731. [PMID: 27558716 DOI: 10.1016/j.bpj.2016.07.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 06/22/2016] [Accepted: 07/11/2016] [Indexed: 12/13/2022] Open
Abstract
Resistance to Inhibitors of Cholinesterase A (Ric-8A) is a 60-kDa cytosolic protein that has chaperone and guanine nucleotide exchange (GEF) activity toward heterotrimeric G protein α subunits of the i, q, and 12/13 classes, catalyzing the release of GDP from Gα and subsequent binding of GTP. In the absence of GTP or GTP analogs, and subsequent to GDP release, Gα forms a stable nucleotide-free complex with Ric-8A. In this study, time-resolved fluorescence anisotropy measurements were employed to detect local motions of Gαi1 labeled at selected sites with Alexa 488 (C5) fluorescent dye (Ax) in the GDP, GTPγS (collectively, GXP), and Ric-8A-bound states. Sites selected for Alexa 488 (C5) derivatization were in the α-helical domain (residue 106), the α-helical domain-Ras-like domain hinge (residue 63), Switch I (residue 180), Switch II (residue 209), Switch III (residue 238), the α4 helix (residue 305), and at the junction between the purine-binding subsite in the β6-α5 loop and the C-terminal α helix (residue 330). In the GXP-bound states, the Alexa fluorophore reports local motions with correlation times ranging from 1.0 to 1.8 ns. The dynamics at Ax180 is slower in Gαi1•GDP than in Gαi1•GTPγS. The reverse is true at Ax209. The order parameters, S(2), for Alexa probes at switch residues are high (0.78-0.88) in Gαi1•GDP and lower (0.67-0.75) in Gαi1•GTPγS, although in crystal structures, switch segments are more ordered in the latter. Local motions at Ax63, Ax180, Ax209, and Ax330 are all markedly slower (2.3-2.8 ns) in Gαi1:Ric-8A than in Gαi1•GXP, and only modest (± 0.1) differences in S(2) are observed at most sites in Gαi1:Ric-8A relative to Gαi1•GXP. The slow dynamics suggests long-range correlated transitions within an ensemble of states and, particularly in the hinge and switch segments that make direct contact with Ric-8A. Induction of Gαi1 structural heterogeneity by Ric-8A provides a mechanism for nucleotide release.
Collapse
|
27
|
Toyama Y, Kano H, Mase Y, Yokogawa M, Osawa M, Shimada I. Dynamic regulation of GDP binding to G proteins revealed by magnetic field-dependent NMR relaxation analyses. Nat Commun 2017; 8:14523. [PMID: 28223697 PMCID: PMC5322562 DOI: 10.1038/ncomms14523] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 01/10/2017] [Indexed: 11/30/2022] Open
Abstract
Heterotrimeric guanine-nucleotide-binding proteins (G proteins) serve as molecular switches in signalling pathways, by coupling the activation of cell surface receptors to intracellular responses. Mutations in the G protein α-subunit (Gα) that accelerate guanosine diphosphate (GDP) dissociation cause hyperactivation of the downstream effector proteins, leading to oncogenesis. However, the structural mechanism of the accelerated GDP dissociation has remained unclear. Here, we use magnetic field-dependent nuclear magnetic resonance relaxation analyses to investigate the structural and dynamic properties of GDP bound Gα on a microsecond timescale. We show that Gα rapidly exchanges between a ground-state conformation, which tightly binds to GDP and an excited conformation with reduced GDP affinity. The oncogenic D150N mutation accelerates GDP dissociation by shifting the equilibrium towards the excited conformation. Heterotrimeric guanine-nucleotide-binding proteins (G proteins) act as molecular switches. Here the authors use NMR relaxation analyses, which reveal the dynamics of G protein alpha subunit binding to GDP on a microsecond timescale.
Collapse
Affiliation(s)
- Yuki Toyama
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.,Japan Biological Informatics Consortium (JBiC), Aomi, Koto-ku, Tokyo 135-0064, Japan
| | - Hanaho Kano
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yoko Mase
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Mariko Yokogawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Osawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ichio Shimada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| |
Collapse
|
28
|
Duc NM, Kim HR, Chung KY. Recent Progress in Understanding the Conformational Mechanism of Heterotrimeric G Protein Activation. Biomol Ther (Seoul) 2017; 25:4-11. [PMID: 28035078 PMCID: PMC5207459 DOI: 10.4062/biomolther.2016.169] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 08/26/2016] [Accepted: 09/01/2016] [Indexed: 12/05/2022] Open
Abstract
Heterotrimeric G proteins are key intracellular coordinators that receive signals from cells through activation of cognate G protein-coupled receptors (GPCRs). The details of their atomic interactions and structural mechanisms have been described by many biochemical and biophysical studies. Specifically, a framework for understanding conformational changes in the receptor upon ligand binding and associated G protein activation was provided by description of the crystal structure of the β2-adrenoceptor-Gs complex in 2011. This review focused on recent findings in the conformational dynamics of G proteins and GPCRs during activation processes.
Collapse
Affiliation(s)
- Nguyen Minh Duc
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hee Ryung Kim
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ka Young Chung
- School of Pharmacy, Sungkyunkwan University, Suwon 16419, Republic of Korea
| |
Collapse
|
29
|
Kant R, Zeng B, Thomas CJ, Bothner B, Sprang SR. Ric-8A, a G protein chaperone with nucleotide exchange activity induces long-range secondary structure changes in Gα. eLife 2016; 5. [PMID: 28008853 PMCID: PMC5182059 DOI: 10.7554/elife.19238] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/22/2016] [Indexed: 11/24/2022] Open
Abstract
Cytosolic Ric-8A has guanine nucleotide exchange factor (GEF) activity and is a chaperone for several classes of heterotrimeric G protein α subunits in vertebrates. Using Hydrogen-Deuterium Exchange-Mass Spectrometry (HDX-MS) we show that Ric-8A disrupts the secondary structure of the Gα Ras-like domain that girds the guanine nucleotide-binding site, and destabilizes the interface between the Gαi1 Ras and helical domains, allowing domain separation and nucleotide release. These changes are largely reversed upon binding GTP and dissociation of Ric-8A. HDX-MS identifies a potential Gα interaction site in Ric-8A. Alanine scanning reveals residues crucial for GEF activity within that sequence. HDX confirms that, like G protein-coupled receptors (GPCRs), Ric-8A binds the C-terminus of Gα. In contrast to GPCRs, Ric-8A interacts with Switches I and II of Gα and possibly at the Gα domain interface. These extensive interactions provide both allosteric and direct catalysis of GDP unbinding and release and GTP binding. DOI:http://dx.doi.org/10.7554/eLife.19238.001
Collapse
Affiliation(s)
- Ravi Kant
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, United States
| | - Baisen Zeng
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| | - Celestine J Thomas
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, United States
| | - Stephen R Sprang
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| |
Collapse
|
30
|
Liu P, Jia MZ, Zhou XE, De Waal PW, Dickson BM, Liu B, Hou L, Yin YT, Kang YY, Shi Y, Melcher K, Xu HE, Jiang Y. The structural basis of the dominant negative phenotype of the Gαi1β1γ2 G203A/A326S heterotrimer. Acta Pharmacol Sin 2016; 37:1259-72. [PMID: 27498775 PMCID: PMC5022103 DOI: 10.1038/aps.2016.69] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 06/08/2016] [Indexed: 12/13/2022] Open
Abstract
Aim: Dominant negative mutant G proteins have provided critical insight into the mechanisms of G protein-coupled receptor (GPCR) signaling, but the mechanisms underlying the dominant negative characteristics are not completely understood. The aim of this study was to determine the structure of the dominant negative Gαi1β1γ2 G203A/A326S complex (Gi-DN) and to reveal the structural basis of the mutation-induced phenotype of Gαi1β1γ2. Methods: The three subunits of the Gi-DN complex were co-expressed with a baculovirus expression system. The Gi-DN heterotrimer was purified, and the structure of its complex with GDP was determined through X-ray crystallography. Results: The Gi-DN heterotrimer structure revealed a dual mechanism underlying the dominant negative characteristics. The mutations weakened the hydrogen bonding network between GDP/GTP and the binding pocket residues, and increased the interactions in the Gα-Gβγ interface. Concomitantly, the Gi-DN heterotrimer adopted a conformation, in which the C-terminus of Gαi and the N-termini of both the Gβ and Gγ subunits were more similar to the GPCR-bound state compared with the wild type complex. From these structural observations, two additional mutations (T48F and D272F) were designed that completely abolish the GDP binding of the Gi-DN heterotrimer. Conclusion: Overall, the results suggest that the mutations impede guanine nucleotide binding and Gα-Gβγ protein dissociation and favor the formation of the G protein/GPCR complex, thus blocking signal propagation. In addition, the structure provides a rationale for the design of other mutations that cause dominant negative effects in the G protein, as exemplified by the T48F and D272F mutations.
Collapse
|
31
|
Computational Simulation of the Activation Cycle of Gα Subunit in the G Protein Cycle Using an Elastic Network Model. PLoS One 2016; 11:e0159528. [PMID: 27483005 PMCID: PMC4970668 DOI: 10.1371/journal.pone.0159528] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 07/04/2016] [Indexed: 01/13/2023] Open
Abstract
Agonist-activated G protein-coupled receptors (GPCRs) interact with GDP-bound G protein heterotrimers (Gαβγ) promoting GDP/GTP exchange, which results in dissociation of Gα from the receptor and Gβγ. The GTPase activity of Gα hydrolyzes GTP to GDP, and the GDP-bound Gα interacts with Gβγ, forming a GDP-bound G protein heterotrimer. The G protein cycle is allosterically modulated by conformational changes of the Gα subunit. Although biochemical and biophysical methods have elucidated the structure and dynamics of Gα, the precise conformational mechanisms underlying the G protein cycle are not fully understood yet. Simulation methods could help to provide additional details to gain further insight into G protein signal transduction mechanisms. In this study, using the available X-ray crystal structures of Gα, we simulated the entire G protein cycle and described not only the steric features of the Gα structure, but also conformational changes at each step. Each reference structure in the G protein cycle was modeled as an elastic network model and subjected to normal mode analysis. Our simulation data suggests that activated receptors trigger conformational changes of the Gα subunit that are thermodynamically favorable for opening of the nucleotide-binding pocket and GDP release. Furthermore, the effects of GTP binding and hydrolysis on mobility changes of the C and N termini and switch regions are elucidated. In summary, our simulation results enabled us to provide detailed descriptions of the structural and dynamic features of the G protein cycle.
Collapse
|
32
|
Sprang SR. Invited review: Activation of G proteins by GTP and the mechanism of Gα-catalyzed GTP hydrolysis. Biopolymers 2016; 105:449-62. [PMID: 26996924 PMCID: PMC5319639 DOI: 10.1002/bip.22836] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/11/2016] [Accepted: 03/17/2016] [Indexed: 02/02/2023]
Abstract
This review addresses the regulatory consequences of the binding of GTP to the alpha subunits (Gα) of heterotrimeric G proteins, the reaction mechanism of GTP hydrolysis catalyzed by Gα and the means by which GTPase activating proteins (GAPs) stimulate the GTPase activity of Gα. The high energy of GTP binding is used to restrain and stabilize the conformation of the Gα switch segments, particularly switch II, to afford stable complementary to the surfaces of Gα effectors, while excluding interaction with Gβγ, the regulatory binding partner of GDP-bound Gα. Upon GTP hydrolysis, the energy of these conformational restraints is dissipated and the two switch segments, particularly switch II, become flexible and are able to adopt a conformation suitable for tight binding to Gβγ. Catalytic site pre-organization presents a significant activation energy barrier to Gα GTPase activity. The glutamine residue near the N-terminus of switch II (Glncat ) must adopt a conformation in which it orients and stabilizes the γ phosphate and the water nucleophile for an in-line attack. The transition state is probably loose with dissociative character; phosphoryl transfer may be concerted. The catalytic arginine in switch I (Argcat ), together with amide hydrogen bonds from the phosphate binding loop, stabilize charge at the β-γ bridge oxygen of the leaving group. GAPs that harbor "regulator of protein signaling" (RGS) domains, or structurally unrelated domains within G protein effectors that function as GAPs, accelerate catalysis by stabilizing the pre-transition state for Gα-catalyzed GTP hydrolysis, primarily by restraining Argcat and Glncat to their catalytic conformations. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 449-462, 2016.
Collapse
Affiliation(s)
- Stephen R. Sprang
- Center for Biomolecular Structure and Dynamics, Division of Biological Sciences, University of Montana, 32 Campus Drive, Missoula, MT 59812, Telephone: (406) 243-6028, Fax: (406) 243-6024,
| |
Collapse
|
33
|
Yancey PH, Siebenaller JF. Co-evolution of proteins and solutions: protein adaptation versus cytoprotective micromolecules and their roles in marine organisms. ACTA ACUST UNITED AC 2016; 218:1880-96. [PMID: 26085665 DOI: 10.1242/jeb.114355] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Organisms experience a wide range of environmental factors such as temperature, salinity and hydrostatic pressure, which pose challenges to biochemical processes. Studies on adaptations to such factors have largely focused on macromolecules, especially intrinsic adaptations in protein structure and function. However, micromolecular cosolutes can act as cytoprotectants in the cellular milieu to affect biochemical function and they are now recognized as important extrinsic adaptations. These solutes, both inorganic and organic, have been best characterized as osmolytes, which accumulate to reduce osmotic water loss. Singly, and in combination, many cosolutes have properties beyond simple osmotic effects, e.g. altering the stability and function of proteins in the face of numerous stressors. A key example is the marine osmolyte trimethylamine oxide (TMAO), which appears to enhance water structure and is excluded from peptide backbones, favoring protein folding and stability and counteracting destabilizers like urea and temperature. Co-evolution of intrinsic and extrinsic adaptations is illustrated with high hydrostatic pressure in deep-living organisms. Cytosolic and membrane proteins and G-protein-coupled signal transduction in fishes under pressure show inhibited function and stability, while revealing a number of intrinsic adaptations in deep species. Yet, intrinsic adaptations are often incomplete, and those fishes accumulate TMAO linearly with depth, suggesting a role for TMAO as an extrinsic 'piezolyte' or pressure cosolute. Indeed, TMAO is able to counteract the inhibitory effects of pressure on the stability and function of many proteins. Other cosolutes are cytoprotective in other ways, such as via antioxidation. Such observations highlight the importance of considering the cellular milieu in biochemical and cellular adaptation.
Collapse
Affiliation(s)
- Paul H Yancey
- Department of Biology, Whitman College, Walla Walla, WA 99362, USA
| | - Joseph F Siebenaller
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| |
Collapse
|
34
|
Sunahara RK, Insel PA. The Molecular Pharmacology of G Protein Signaling Then and Now: A Tribute to Alfred G. Gilman. Mol Pharmacol 2016; 89:585-92. [PMID: 26984025 PMCID: PMC11037445 DOI: 10.1124/mol.116.104216] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 03/14/2016] [Indexed: 11/22/2022] Open
Abstract
The recent, unfortunate death of Alfred G. ("Al") Gilman, M.D., Ph.D., represents a sad signpost for an era spanning over 40 years in molecular pharmacology. Gilman's discoveries, influence, and persona were dominant forces in research and training in pharmacology. Here, we review the progression of ideas and knowledge that spawned early work by Gilman and collaborators (among them, one of the authors) and later efforts (including those of the other author) that have recently yielded a comprehensive and precise structural understanding of fundamental topics in pharmacology: the binding of ligands to G protein-coupled receptors (GPCRs) and the interaction of GPCRs with heterotrimeric G proteins and effector molecules. Those data provide new and important insights into the molecular basis that underlies affinity and efficacy, two of the most important features of drug action, which represent the latest chapter in the saga that Al Gilman's work helped launch.
Collapse
Affiliation(s)
- Roger K Sunahara
- Department of Pharmacology (R.K.S., P.A.I.) and Department of Medicine (P.A.I.), University of California, San Diego, La Jolla, California
| | - Paul A Insel
- Department of Pharmacology (R.K.S., P.A.I.) and Department of Medicine (P.A.I.), University of California, San Diego, La Jolla, California
| |
Collapse
|
35
|
Xu L, Choi S, Xie Y, Sze JY. Cell-Autonomous Gβ Signaling Defines Neuron-Specific Steady State Serotonin Synthesis in Caenorhabditis elegans. PLoS Genet 2015; 11:e1005540. [PMID: 26402365 PMCID: PMC4581872 DOI: 10.1371/journal.pgen.1005540] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 08/27/2015] [Indexed: 11/19/2022] Open
Abstract
Heterotrimeric G proteins regulate a vast array of cellular functions via specific intracellular effectors. Accumulating pharmacological and biochemical studies implicate Gβ subunits as signaling molecules interacting directly with a wide range of effectors to modulate downstream cellular responses, in addition to their role in regulating Gα subunit activities. However, the native biological roles of Gβ-mediated signaling pathways in vivo have been characterized only in a few cases. Here, we identified a Gβ GPB-1 signaling pathway operating in specific serotonergic neurons to the define steady state serotonin (5-HT) synthesis, through a genetic screen for 5-HT synthesis mutants in Caenorhabditis elegans. We found that signaling through cell autonomous GPB-1 to the OCR-2 TRPV channel defines the baseline expression of 5-HT synthesis enzyme tryptophan hydroxylase tph-1 in ADF chemosensory neurons. This Gβ signaling pathway is not essential for establishing the serotonergic cell fates and is mechanistically separated from stress-induced tph-1 upregulation. We identified that ADF-produced 5-HT controls specific innate rhythmic behaviors. These results revealed a Gβ-mediated signaling operating in differentiated cells to specify intrinsic functional properties, and indicate that baseline TPH expression is not a default generic serotonergic fate, but is programmed in a cell-specific manner in the mature nervous system. Cell-specific regulation of TPH expression could be a general principle for tailored steady state 5-HT synthesis in functionally distinct neurons and their regulation of innate behavior. Levels of neurotransmitter serotonin synthesis shape disparate behaviors in evolutionary diverse organisms, but the mechanisms defining steady state serotonin synthesis in functionally distinct neuronal types remain unknown. A genetic screen for neuron-specific serotonin synthesis mutants in Caenorhabditis elegans revealed a unique Gβ GPB-1 signaling pathway operating in specific serotonergic neurons to define the baseline expression of serotonin synthesis rate-limiting enzyme tryptophan hydroxylase tph-1. Unlike in canonical heterotrimeric G protein signaling pathways where Gα subunits drive downstream effectors, we found that signaling through Gβ GPB-1 to the OCR-2 TRPV channel defines the baseline tph-1 expression. This Gβ signaling is not required for the establishment or maintenance of the serotonergic cell fates, but dedicated to set steady state 5-HT synthesis in mature neurons. Behavioral analyses showed that 5-HT synthesized in different neurons modulates distinct innate rhythmic behaviors. Our work identified a Gβ-mediated signaling pathway operating in differentiated neuronal cells to specify intrinsic functional diversities, and illuminate a mechanistic principle for genetic programming of neuron-specific steady state 5-HT synthesis in dedicated behavioral circuits.
Collapse
Affiliation(s)
- Lu Xu
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Sunju Choi
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Yusu Xie
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Ji Ying Sze
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
| |
Collapse
|
36
|
Kwan DHT, Wong KM, Chan ASL, Yung LY, Wong YH. An intact helical domain is required for Gα14 to stimulate phospholipase Cβ. BMC STRUCTURAL BIOLOGY 2015; 15:18. [PMID: 26377666 PMCID: PMC4573470 DOI: 10.1186/s12900-015-0043-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 08/26/2015] [Indexed: 11/17/2022]
Abstract
Background Stimulation of phospholipase Cβ (PLCβ) by the activated α-subunit of Gq (Gαq) constitutes a major signaling pathway for cellular regulation, and structural studies have recently revealed the molecular interactions between PLCβ and Gαq. Yet, most of the PLCβ-interacting residues identified on Gαq are not unique to members of the Gαq family. Molecular modeling predicts that the core PLCβ-interacting residues located on the switch regions of Gαq are similarly positioned in Gαz which does not stimulate PLCβ. Using wild-type and constitutively active chimeras constructed between Gαz and Gα14, a member of the Gαq family, we examined if the PLCβ-interacting residues identified in Gαq are indeed essential. Results Four chimeras with the core PLCβ-interacting residues composed of Gαz sequences were capable of binding PLCβ2 and stimulating the formation of inositol trisphosphate. Surprisingly, all chimeras with a Gαz N-terminal half failed to functionally associate with PLCβ2, despite the fact that many of them contained the core PLCβ-interacting residues from Gα14. Further analyses revealed that the non-PLCβ2 interacting chimeras were capable of interacting with other effector molecules such as adenylyl cyclase and tetratricopeptide repeat 1, indicating that they could adopt a GTP-bound active conformation. Conclusion Collectively, our study suggests that the previously identified PLCβ-interacting residues are insufficient to ensure productive interaction of Gα14 with PLCβ, while an intact N-terminal half of Gα14 is apparently required for PLCβ interaction. Electronic supplementary material The online version of this article (doi:10.1186/s12900-015-0043-3) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Dawna H T Kwan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Ka M Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Anthony S L Chan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Lisa Y Yung
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Yung H Wong
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. .,State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| |
Collapse
|
37
|
Sun D, Flock T, Deupi X, Maeda S, Matkovic M, Mendieta S, Mayer D, Dawson R, Schertler GFX, Madan Babu M, Veprintsev DB. Probing Gαi1 protein activation at single-amino acid resolution. Nat Struct Mol Biol 2015; 22:686-694. [PMID: 26258638 PMCID: PMC4876908 DOI: 10.1038/nsmb.3070] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 07/17/2015] [Indexed: 11/08/2022]
Abstract
We present comprehensive maps at single-amino acid resolution of the residues stabilizing the human Gαi1 subunit in nucleotide- and receptor-bound states. We generated these maps by measuring the effects of alanine mutations on the stability of Gαi1 and the rhodopsin-Gαi1 complex. We identified stabilization clusters in the GTPase and helical domains responsible for structural integrity and the conformational changes associated with activation. In activation cluster I, helices α1 and α5 pack against strands β1-β3 to stabilize the nucleotide-bound states. In the receptor-bound state, these interactions are replaced by interactions between α5 and strands β4-β6. Key residues in this cluster are Y320, which is crucial for the stabilization of the receptor-bound state, and F336, which stabilizes nucleotide-bound states. Destabilization of helix α1, caused by rearrangement of this activation cluster, leads to the weakening of the interdomain interface and release of GDP.
Collapse
Affiliation(s)
- Dawei Sun
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Tilman Flock
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Xavier Deupi
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Condensed Matter Theory Group, Paul Scherrer Institut, Villigen, Switzerland
| | - Shoji Maeda
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Milos Matkovic
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Sandro Mendieta
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Daniel Mayer
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - Roger Dawson
- F. Hoffmann-La Roche AG, Pharma Research & Early Development, Discovery Technologies, Basel, Switzerland
| | - Gebhard F X Schertler
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| | - M Madan Babu
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Dmitry B Veprintsev
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Department of Biology, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland
| |
Collapse
|
38
|
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
|
39
|
Brown NE, Goswami D, Branch MR, Ramineni S, Ortlund EA, Griffin PR, Hepler JR. Integration of G protein α (Gα) signaling by the regulator of G protein signaling 14 (RGS14). J Biol Chem 2015; 290:9037-49. [PMID: 25666614 DOI: 10.1074/jbc.m114.634329] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Indexed: 11/06/2022] Open
Abstract
RGS14 contains distinct binding sites for both active (GTP-bound) and inactive (GDP-bound) forms of Gα subunits. The N-terminal regulator of G protein signaling (RGS) domain binds active Gαi/o-GTP, whereas the C-terminal G protein regulatory (GPR) motif binds inactive Gαi1/3-GDP. The molecular basis for how RGS14 binds different activation states of Gα proteins to integrate G protein signaling is unknown. Here we explored the intramolecular communication between the GPR motif and the RGS domain upon G protein binding and examined whether RGS14 can functionally interact with two distinct forms of Gα subunits simultaneously. Using complementary cellular and biochemical approaches, we demonstrate that RGS14 forms a stable complex with inactive Gαi1-GDP at the plasma membrane and that free cytosolic RGS14 is recruited to the plasma membrane by activated Gαo-AlF4(-). Bioluminescence resonance energy transfer studies showed that RGS14 adopts different conformations in live cells when bound to Gα in different activation states. Hydrogen/deuterium exchange mass spectrometry revealed that RGS14 is a very dynamic protein that undergoes allosteric conformational changes when inactive Gαi1-GDP binds the GPR motif. Pure RGS14 forms a ternary complex with Gαo-AlF4(-) and an AlF4(-)-insensitive mutant (G42R) of Gαi1-GDP, as observed by size exclusion chromatography and differential hydrogen/deuterium exchange. Finally, a preformed RGS14·Gαi1-GDP complex exhibits full capacity to stimulate the GTPase activity of Gαo-GTP, demonstrating that RGS14 can functionally engage two distinct forms of Gα subunits simultaneously. Based on these findings, we propose a working model for how RGS14 integrates multiple G protein signals in host CA2 hippocampal neurons to modulate synaptic plasticity.
Collapse
Affiliation(s)
| | - Devrishi Goswami
- the Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, Florida 33458
| | | | | | - Eric A Ortlund
- Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322 and
| | - Patrick R Griffin
- the Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, Florida 33458
| | | |
Collapse
|
40
|
The guanine nucleotide exchange factor Ric-8A induces domain separation and Ras domain plasticity in Gαi1. Proc Natl Acad Sci U S A 2015; 112:1404-9. [PMID: 25605908 DOI: 10.1073/pnas.1423878112] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Heterotrimeric G proteins are activated by exchange of GDP for GTP at the G protein alpha subunit (Gα), most notably by G protein-coupled transmembrane receptors. Ric-8A is a soluble cytoplasmic protein essential for embryonic development that acts as both a guanine nucleotide exchange factor (GEF) and a chaperone for Gα subunits of the i, q, and 12/13 classes. Previous studies demonstrated that Ric-8A stabilizes a dynamically disordered state of nucleotide-free Gα as the catalytic intermediate for nucleotide exchange, but no information was obtained on the structures involved or the magnitude of the structural fluctuations. In the present study, site-directed spin labeling (SDSL) together with double electron-electron resonance (DEER) spectroscopy is used to provide global distance constraints that identify discrete members of a conformational ensemble in the Gαi1:Ric-8A complex and the magnitude of structural differences between them. In the complex, the helical and Ras-like nucleotide-binding domains of Gαi1 pivot apart to occupy multiple resolved states with displacements as large as 25 Å. The domain displacement appears to be distinct from that observed in Gαs upon binding of Gs to the β2 adrenergic receptor. Moreover, the Ras-like domain exhibits structural plasticity within and around the nucleotide-binding cavity, and the switch I and switch II regions, which are known to adopt different conformations in the GDP- and GTP-bound states of Gα, undergo structural rearrangements. Collectively, the data show that Ric-8A induces a conformationally heterogeneous state of Gαi and provide insight into the mechanism of action of a nonreceptor Gα GEF.
Collapse
|
41
|
D. Lokits A, Koehler Leman J, E. Kitko K, S. Alexander N, E. Hamm H, Meiler J. A survey of conformational and energetic changes in G protein signaling. AIMS BIOPHYSICS 2015. [DOI: 10.3934/biophy.2015.4.630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
42
|
Kaya AI, Lokits AD, Gilbert JA, Iverson TM, Meiler J, Hamm HE. A conserved phenylalanine as a relay between the α5 helix and the GDP binding region of heterotrimeric Gi protein α subunit. J Biol Chem 2014; 289:24475-87. [PMID: 25037222 PMCID: PMC4148873 DOI: 10.1074/jbc.m114.572875] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Revised: 07/15/2014] [Indexed: 11/06/2022] Open
Abstract
G protein activation by G protein-coupled receptors is one of the critical steps for many cellular signal transduction pathways. Previously, we and other groups reported that the α5 helix in the G protein α subunit plays a major role during this activation process. However, the precise signaling pathway between the α5 helix and the guanosine diphosphate (GDP) binding pocket remains elusive. Here, using structural, biochemical, and computational techniques, we probed different residues around the α5 helix for their role in signaling. Our data showed that perturbing the Phe-336 residue disturbs hydrophobic interactions with the β2-β3 strands and α1 helix, leading to high basal nucleotide exchange. However, mutations in β strands β5 and β6 do not perturb G protein activation. We have highlighted critical residues that leverage Phe-336 as a relay. Conformational changes are transmitted starting from Phe-336 via β2-β3/α1 to Switch I and the phosphate binding loop, decreasing the stability of the GDP binding pocket and triggering nucleotide release. When the α1 and α5 helices were cross-linked, inhibiting the receptor-mediated displacement of the C-terminal α5 helix, mutation of Phe-336 still leads to high basal exchange rates. This suggests that unlike receptor-mediated activation, helix 5 rotation and translocation are not necessary for GDP release from the α subunit. Rather, destabilization of the backdoor region of the Gα subunit is sufficient for triggering the activation process.
Collapse
Affiliation(s)
| | | | | | | | - Jens Meiler
- From the Departments of Pharmacology, Chemistry, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | | |
Collapse
|
43
|
Ichiyama S, Nemoto R, Tanabe H, Haga T. Interaction of the muscarinic acetylcholine receptor M₂ subtype with G protein Gα(i/o) isotypes and Gβγ subunits as studied with the maltose-binding protein-M₂-Gα(i/o) fusion proteins expressed in Escherichia coli. J Biochem 2014; 156:259-72. [PMID: 24881046 DOI: 10.1093/jb/mvu036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We expressed the fusion proteins of the muscarinic acetylcholine receptor M2 subtype (M2 receptor) with a maltose-binding protein (MBP) and various G protein α subunits (Gα(i1-i3/o)) at its N- and C-terminals, respectively (MBP-M2-Gα(i/o)), in Escherichia coli, and examined the effect of G protein βγ subunits (Gβγ) on the receptor-Gα interaction as assessed by agonist- and GDP-dependent [(35)S]GTPγS binding of the fusion proteins. We found that (i) Gβγ promoted both the agonist-dependent and -independent [(35)S]GTPγS binding with little effect on the guanine nucleotide-sensitive high-affinity agonist binding, (ii) the specific [(35)S]GTPγS binding activity was much greater for MBP-M2-Gα(oA) than for MBP-M2-Gα(i1-i3) in the absence of Gβγ, whereas Gβγ preferentially promoted the agonist-dependent decrease in the affinity for GDP of MBP-M2-Gα(i1-i3) rather than of MBP-M2-Gα(oA), and (iii) the proportion of agonist-dependent [(35)S]GTPγS binding was roughly 50% irrespective of species of Gα and the presence or absence of Gβγ. These results demonstrate that receptor-Gα fusion proteins expressed in E. coli could be useful for studies of receptor-G interaction.
Collapse
Affiliation(s)
- Susumu Ichiyama
- Faculty of Science, Institute for Biomolecular Science, Gakushuin University, 1-5-1 Mejiro, Toshima-Ku, Tokyo 171-8588, Japan
| | - Reiko Nemoto
- Faculty of Science, Institute for Biomolecular Science, Gakushuin University, 1-5-1 Mejiro, Toshima-Ku, Tokyo 171-8588, Japan
| | - Hiroaki Tanabe
- Faculty of Science, Institute for Biomolecular Science, Gakushuin University, 1-5-1 Mejiro, Toshima-Ku, Tokyo 171-8588, Japan
| | - Tatsuya Haga
- Faculty of Science, Institute for Biomolecular Science, Gakushuin University, 1-5-1 Mejiro, Toshima-Ku, Tokyo 171-8588, Japan
| |
Collapse
|
44
|
Turcic K, Tobar-Rubin R, Janevska D, Carroll J, Din E, Alvarez R, Haick J, Pals-Rylaarsdam R. Three intragenic suppressors of a GTPase-deficient allele of GNAS associated with McCune-Albright syndrome. J Mol Endocrinol 2014; 52:321-31. [PMID: 24850831 DOI: 10.1530/jme-13-0297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Gain-of-function mutations in heterotrimeric G-protein α subunits are associated with a variety of human diseases. McCune-Albright syndrome (MAS) is caused by mutations in GNAS, the gene encoding Gs. Alterations at Arg201 significantly reduce the GTPase activity of the protein, rendering it constitutively active. In this study, we have constructed a library of random mutations in a constitutively active yeast GPA1 gene carrying a mutation homologous to the McCune-Albright allele (Arg297His). Intragenic suppressors found at sites with homology to the human Gs protein were tested for their ability to suppress the constitutive activity of an Arg201His mutation in Gs. Three intragenic suppressors, at Phe142, Arg231, and Leu266, were able to suppress elevated basal cAMP responses caused by Arg201His when expressed in HEK293 cells. A range of amino acid substitutions was introduced at each of these sites to investigate the chemical requirements for intragenic suppression. The ability of Gs proteins carrying the suppressor mutations alone to mediate receptor-induced cAMP production was measured. These results offer potential sites on Gs that could serve as drug targets for MAS therapies.
Collapse
Affiliation(s)
- Kyle Turcic
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Raquel Tobar-Rubin
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Daniela Janevska
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Julie Carroll
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Eraj Din
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Rebecca Alvarez
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Jennifer Haick
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| | - Robin Pals-Rylaarsdam
- Department of Biological ScienceBenedictine University, 5700 College Road, Lisle, Illinois 60532, USA
| |
Collapse
|
45
|
Dixit G, Baker R, Sacks CM, Torres MP, Dohlman HG. Guanine nucleotide-binding protein (Gα) endocytosis by a cascade of ubiquitin binding domain proteins is required for sustained morphogenesis and proper mating in yeast. J Biol Chem 2014; 289:15052-63. [PMID: 24722989 PMCID: PMC4031556 DOI: 10.1074/jbc.m114.566117] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 04/07/2014] [Indexed: 01/10/2023] Open
Abstract
Heterotrimeric G proteins are well known to transmit signals from cell surface receptors to intracellular effector proteins. There is growing appreciation that G proteins are also present at endomembrane compartments, where they can potentially interact with a distinct set of signaling proteins. Here, we examine the cellular trafficking function of the G protein α subunit in yeast, Gpa1. Gpa1 contains a unique 109-amino acid insert within the α-helical domain that undergoes a variety of posttranslational modifications. Among these is monoubiquitination, catalyzed by the NEDD4 family ubiquitin ligase Rsp5. Using a newly optimized method for G protein purification together with biophysical measures of structure and function, we show that the ubiquitination domain does not influence enzyme activity. By screening a panel of 39 gene deletion mutants, each lacking a different ubiquitin binding domain protein, we identify seven that are necessary to deliver Gpa1 to the vacuole compartment including four proteins (Ede1, Bul1, Ddi1, and Rup1) previously not known to be involved in this process. Finally, we show that proper endocytosis of the G protein is needed for sustained cellular morphogenesis and mating in response to pheromone stimulation. We conclude that a cascade of ubiquitin-binding proteins serves to deliver the G protein to its final destination within the cell. In this instance and in contrast to the previously characterized visual system, endocytosis from the plasma membrane is needed for proper signal transduction rather than for signal desensitization.
Collapse
Affiliation(s)
- Gauri Dixit
- From the Department of Biochemistry and Biophysics
| | | | | | - Matthew P Torres
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Henrik G Dohlman
- From the Department of Biochemistry and Biophysics, Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 and
| |
Collapse
|
46
|
Thaker TM, Sarwar M, Preininger AM, Hamm HE, Iverson TM. A transient interaction between the phosphate binding loop and switch I contributes to the allosteric network between receptor and nucleotide in Gαi1. J Biol Chem 2014; 289:11331-11341. [PMID: 24596087 DOI: 10.1074/jbc.m113.539064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor-mediated activation of the Gα subunit of heterotrimeric G proteins requires allosteric communication between the receptor binding site and the guanine nucleotide binding site, which are separated by >30 Å. Structural changes in the allosteric network connecting these sites are predicted to be transient in the wild-type Gα subunit, making studies of these connections challenging. In the current work, site-directed mutants that alter the energy barriers between the activation states are used as tools to better understand the transient features of allosteric signaling in the Gα subunit. The observed differences in relative receptor affinity for intact Gαi1 subunits versus C-terminal Gαi1 peptides harboring the K345L mutation are consistent with this mutation modulating the allosteric network in the protein subunit. Measurement of nucleotide exchange rates, affinity for metarhodopsin II, and thermostability suggest that the K345L Gαi1 variant has reduced stability in both the GDP-bound and nucleotide-free states as compared with wild type but similar stability in the GTPγS-bound state. High resolution x-ray crystal structures reveal conformational changes accompanying the destabilization of the GDP-bound state. Of these, the conformation for Switch I was stabilized by an ionic interaction with the phosphate binding loop. Further site-directed mutagenesis suggests that this interaction between Switch I and the phosphate binding loop is important for receptor-mediated nucleotide exchange in the wild-type Gαi1 subunit.
Collapse
Affiliation(s)
- Tarjani M Thaker
- Department of Biochemistry and Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Maruf Sarwar
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Anita M Preininger
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Heidi E Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
| | - T M Iverson
- Department of Biochemistry and Vanderbilt University Medical Center, Nashville, Tennessee 37232; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
| |
Collapse
|
47
|
Boularan C, Kehrl JH. Implications of non-canonical G-protein signaling for the immune system. Cell Signal 2014; 26:1269-82. [PMID: 24583286 DOI: 10.1016/j.cellsig.2014.02.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 02/22/2014] [Indexed: 01/13/2023]
Abstract
Heterotrimeric guanine nucleotide-binding proteins (G proteins), which consist of three subunits α, β, and γ, function as molecular switches to control downstream effector molecules activated by G protein-coupled receptors (GPCRs). The GTP/GDP binding status of Gα transmits information about the ligand binding state of the GPCR to intended signal transduction pathways. In immune cells heterotrimeric G proteins impact signal transduction pathways that directly, or indirectly, regulate cell migration, activation, survival, proliferation, and differentiation. The cells of the innate and adaptive immune system abundantly express chemoattractant receptors and lesser amounts of many other types of GPCRs. But heterotrimeric G-proteins not only function in classical GPCR signaling, but also in non-canonical signaling. In these pathways the guanine exchange factor (GEF) exerted by a GPCR in the canonical pathway is replaced or supplemented by another protein such as Ric-8A. In addition, other proteins such as AGS3-6 can compete with Gβγ for binding to GDP bound Gα. This competition can promote Gβγ signaling by freeing Gβγ from rapidly rebinding GDP bound Gα. The proteins that participate in these non-canonical signaling pathways will be briefly described and their role, or potential one, in cells of the immune system will be highlighted.
Collapse
Affiliation(s)
- Cédric Boularan
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, United States
| | - John H Kehrl
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, United States.
| |
Collapse
|
48
|
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
|
49
|
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
|
50
|
Conley JM, Watts VJ. Differential effects of AGS3 expression on D(2L) dopamine receptor-mediated adenylyl cyclase signaling. Cell Mol Neurobiol 2013; 33:551-8. [PMID: 23504261 PMCID: PMC3628818 DOI: 10.1007/s10571-013-9925-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 03/09/2013] [Indexed: 12/01/2022]
Abstract
Activator of G protein signaling 3 (AGS3) binds Gα(i) subunits in the GDP-bound state, implicating AGS3 as an important regulator of Gα(i)-linked receptor (e.g., D2 dopamine and μ-opioid) signaling. We examined the ability of AGS3 to modulate recombinant adenylyl cyclase (AC) type 1 and 2 signaling in HEK293 cells following both acute and persistent activation of the D(2L) dopamine receptor (D(2L)DR). AGS3 expression modestly enhanced the potency of acute quinpirole-induced D(2L)DR modulation of AC1 or AC2 activity. AGS3 also promoted desensitization of D(2L)DR-mediated inhibition of AC1, whereas desensitization of D(2L)DR-mediated AC2 activation was significantly attenuated. Additionally, AGS3 reduced D(2L)DR-mediated sensitization of AC1 and AC2. These data suggest that AGS3 is involved in altering G protein signaling in a complex fashion that is effector-specific and dependent on the duration of receptor activation.
Collapse
Affiliation(s)
- Jason M. Conley
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Val J. Watts
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| |
Collapse
|