1
|
Pepanian A, Sommerfeld P, Binbay FA, Fischer D, Pietsch M, Imhof D. In-depth analysis of Gαs protein activity by probing different fluorescently labeled guanine nucleotides. Biol Chem 2024; 405:297-309. [PMID: 38353111 DOI: 10.1515/hsz-2023-0321] [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: 10/10/2023] [Accepted: 01/10/2024] [Indexed: 05/04/2024]
Abstract
G proteins are interacting partners of G protein-coupled receptors (GPCRs) in eukaryotic cells. Upon G protein activation, the ability of the Gα subunit to exchange GDP for GTP determines the intracellular signal transduction. Although various studies have successfully shown that both Gαs and Gαi have an opposite effect on the intracellular cAMP production, with the latter being commonly described as "more active", the functional analysis of Gαs is a comparably more complicated matter. Additionally, the thorough investigation of the ubiquitously expressed variants of Gαs, Gαs(short) and Gαs(long), is still pending. Since the previous experimental evaluation of the activity and function of the Gαs isoforms is not consistent, the focus was laid on structural investigations to understand the GTPase activity. Herein, we examined recombinant human Gαs by applying an established methodological setup developed for Gαi characterization. The ability for GTP binding was evaluated with fluorescence and fluorescence anisotropy assays, whereas the intrinsic hydrolytic activity of the isoforms was determined by a GTPase assay. Among different nucleotide probes, BODIPY FL GTPγS exhibited the highest binding affinity towards the Gαs subunit. This work provides a deeper understanding of the Gαs subunit and provides novel information concerning the differences between the two protein variants.
Collapse
Affiliation(s)
- Anna Pepanian
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Paul Sommerfeld
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, D-50931 Cologne, Germany
| | - Furkan Ayberk Binbay
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Dietmar Fischer
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, D-50931 Cologne, Germany
| | - Markus Pietsch
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, D-50931 Cologne, Germany
- Faculty of Applied Natural Sciences, TH Köln-University of Applied Sciences, Campus Leverkusen, D-51379 Leverkusen, Germany
| | - Diana Imhof
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| |
Collapse
|
2
|
Wu J, Li X, Wu C, Wang Y, Zhang J. Current advances and development strategies of targeting son of sevenless 1 (SOS1) in drug discovery. Eur J Med Chem 2024; 268:116282. [PMID: 38430853 DOI: 10.1016/j.ejmech.2024.116282] [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: 01/19/2024] [Revised: 02/20/2024] [Accepted: 02/23/2024] [Indexed: 03/05/2024]
Abstract
The Son of Sevenless 1 (SOS1) guanine nucleotide exchange factor, prevalent across eukaryotic species, plays a pivotal role in facilitating the attachment of RAS protein to GTP, thereby regulating the activation of intracellular RAS proteins. This regulation is part of a feedback mechanism involving SOS1, which allows both activators and inhibitors of SOS1 to exert control over downstream signaling pathways, demonstrating potential anti-tumor effects. Predominantly, small molecule modulators that target SOS1 focus on a hydrophobic pocket within the CDC25 protein domain. The effectiveness of these modulators largely depends on their ability to interact with specific amino acids, notably Phe890 and Tyr884. This interaction is crucial for influencing the protein-protein interaction (PPI) between RAS and the catalytic domain of SOS1. Currently, most small molecule modulators targeting SOS1 are in the preclinical research phase, with a few advancing to clinical trials. This progression raises safety concerns, making the assurance of drug safety a primary consideration alongside the enhancement of efficacy in the development of SOS1 modulators. This review encapsulates recent advancements in the chemical categorization of SOS1 inhibitors and activators. It delves into the evolution of small molecule modulation targeting SOS1 and offers perspectives on the design of future generations of selective SOS1 small molecule modulators.
Collapse
Affiliation(s)
- Jialin Wu
- Department of Neurology, Neuro-system and Multimorbidity Laboratory and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China; Department of Pulmonary and Critical Care Medicine, Targeted Tracer Research and Development Laboratory, Institute of Respiratory Health, Frontiers Science Center for Disease-related Molecular Network, Precision Medicine Key Laboratory of Sichuan Province & Precision Medicine Research Center, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Xiaoxue Li
- Department of Dermatology, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Chengyong Wu
- Department of Neurology, Neuro-system and Multimorbidity Laboratory and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China; Department of Pulmonary and Critical Care Medicine, Targeted Tracer Research and Development Laboratory, Institute of Respiratory Health, Frontiers Science Center for Disease-related Molecular Network, Precision Medicine Key Laboratory of Sichuan Province & Precision Medicine Research Center, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Yuxi Wang
- Department of Pulmonary and Critical Care Medicine, Targeted Tracer Research and Development Laboratory, Institute of Respiratory Health, Frontiers Science Center for Disease-related Molecular Network, Precision Medicine Key Laboratory of Sichuan Province & Precision Medicine Research Center, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
| | - Jifa Zhang
- Department of Neurology, Neuro-system and Multimorbidity Laboratory and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
| |
Collapse
|
3
|
Larasati YA, Solis GP, Koval A, Griffiths ST, Berentsen R, Aukrust I, Lesca G, Chatron N, Ville D, Korff CM, Katanaev VL. Clinical Cases and the Molecular Profiling of a Novel Childhood Encephalopathy-Causing GNAO1 Mutation P170R. Cells 2023; 12:2469. [PMID: 37887313 PMCID: PMC10605901 DOI: 10.3390/cells12202469] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/29/2023] [Accepted: 10/12/2023] [Indexed: 10/28/2023] Open
Abstract
De novo mutations in GNAO1, the gene encoding the major neuronal G protein Gαo, cause a spectrum of pediatric encephalopathies with seizures, motor dysfunction, and developmental delay. Of the >80 distinct missense pathogenic variants, many appear to uniformly destabilize the guanine nucleotide handling of the mutant protein, speeding up GTP uptake and deactivating GTP hydrolysis. Zinc supplementation emerges as a promising treatment option for this disease, as Zn2+ ions reactivate the GTP hydrolysis on the mutant Gαo and restore cellular interactions for some of the mutants studied earlier. The molecular etiology of GNAO1 encephalopathies needs further elucidation as a prerequisite for the development of efficient therapeutic approaches. In this work, we combine clinical and medical genetics analysis of a novel GNAO1 mutation with an in-depth molecular dissection of the resultant protein variant. We identify two unrelated patients from Norway and France with a previously unknown mutation in GNAO1, c.509C>G that results in the production of the Pro170Arg mutant Gαo, leading to severe developmental and epileptic encephalopathy. Molecular investigations of Pro170Arg identify this mutant as a unique representative of the pathogenic variants. Its 100-fold-accelerated GTP uptake is not accompanied by a loss in GTP hydrolysis; Zn2+ ions induce a previously unseen effect on the mutant, forcing it to lose the bound GTP. Our work combining clinical and molecular analyses discovers a novel, biochemically distinct pathogenic missense variant of GNAO1 laying the ground for personalized treatment development.
Collapse
Affiliation(s)
- Yonika A. Larasati
- Translational Research Center in Oncohaematology, Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland (G.P.S.); (A.K.)
| | - Gonzalo P. Solis
- Translational Research Center in Oncohaematology, Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland (G.P.S.); (A.K.)
| | - Alexey Koval
- Translational Research Center in Oncohaematology, Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland (G.P.S.); (A.K.)
| | - Silja T. Griffiths
- Department of Pediatrics, Haukeland University Hospital, 5009 Bergen, Norway
| | - Ragnhild Berentsen
- Department of Medical Genetics, Haukeland University Hospital, 5009 Bergen, Norway; (R.B.)
| | - Ingvild Aukrust
- Department of Medical Genetics, Haukeland University Hospital, 5009 Bergen, Norway; (R.B.)
- Department of Clinical Science, University of Bergen, 5008 Bergen, Norway
| | - Gaetan Lesca
- Department of Medical Genetics, University Hospital of Lyon, 69002 Lyon, France; (G.L.); (N.C.)
| | - Nicolas Chatron
- Department of Medical Genetics, University Hospital of Lyon, 69002 Lyon, France; (G.L.); (N.C.)
| | - Dorothée Ville
- Pediatric Neurology Department, University Hospital of Lyon, 69002 Lyon, France;
| | - Christian M. Korff
- Pediatric Neurology Unit, University Hospitals of Geneva, CH-1211 Geneva, Switzerland;
| | - Vladimir L. Katanaev
- Translational Research Center in Oncohaematology, Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland (G.P.S.); (A.K.)
- Institute of Life Sciences and Biomedicine, Far Eastern Federal University, Vladivostok 690090, Russia
| |
Collapse
|
4
|
Pepanian A, Sommerfeld P, Kasprzyk R, Kühl T, Binbay FA, Hauser C, Löser R, Wodtke R, Bednarczyk M, Chrominski M, Kowalska J, Jemielity J, Imhof D, Pietsch M. Fluorescence Anisotropy Assay with Guanine Nucleotides Provides Access to Functional Analysis of Gαi1 Proteins. Anal Chem 2022; 94:14410-14418. [PMID: 36206384 DOI: 10.1021/acs.analchem.2c03176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gα proteins as part of heterotrimeric G proteins are molecular switches essential for G protein-coupled receptor- mediated intracellular signaling. The role of the Gα subunits has been examined for decades with various guanine nucleotides to elucidate the activation mechanism and Gα protein-dependent signal transduction. Several approaches describe fluorescent ligands mimicking the GTP function, yet lack the efficient estimation of the proteins' GTP binding activity and the fraction of active protein. Herein, we report the development of a reliable fluorescence anisotropy-based method to determine the affinity of ligands at the GTP-binding site and to quantify the fraction of active Gαi1 protein. An advanced bacterial expression protocol was applied to produce active human Gαi1 protein, whose GTP binding capability was determined with novel fluorescently labeled guanine nucleotides acting as high-affinity Gαi1 binders compared to the commonly used BODIPY FL GTPγS. This study thus contributes a new method for future investigations of the characterization of Gαi and other Gα protein subunits, exploring their corresponding signal transduction systems and potential for biomedical applications.
Collapse
Affiliation(s)
- Anna Pepanian
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, 53121 Bonn, Germany
| | - Paul Sommerfeld
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Renata Kasprzyk
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Toni Kühl
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, 53121 Bonn, Germany
| | - F Ayberk Binbay
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, 53121 Bonn, Germany
| | - Christoph Hauser
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Reik Löser
- Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Robert Wodtke
- Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Marcelina Bednarczyk
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland.,Division of Biophysics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland
| | | | - Joanna Kowalska
- Division of Biophysics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland
| | - Jacek Jemielity
- Centre of New Technologies, University of Warsaw, 02-097 Warsaw, Poland
| | - Diana Imhof
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, 53121 Bonn, Germany
| | - Markus Pietsch
- Institutes I & II of Pharmacology, Center of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| |
Collapse
|
5
|
Mondal S, Hsiao K, Goueli SA. A Homogenous Bioluminescent System for Measuring GTPase, GTPase Activating Protein, and Guanine Nucleotide Exchange Factor Activities. Assay Drug Dev Technol 2015; 13:444-55. [PMID: 26167953 PMCID: PMC4605356 DOI: 10.1089/adt.2015.643] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
GTPases play a major role in various cellular functions such as cell signaling, cell proliferation, cell differentiation, cytoskeleton modulation, and cell motility. Deregulation or mutation of these proteins has considerable consequences resulting in multiple pathological conditions. Targeting GTPases and its regulators has been challenging due to paucity of convenient assays. In this study, we describe a homogenous bioluminescent assay for monitoring the activities of GTPase and its immediate regulators: GTPase activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs). Since Mg2+ plays a critical role in influencing the affinity of GTPases with guanosine triphosphate/guanosine diphosphate (GTP/GDP) and the process of nucleotide exchange, manipulating Mg2+ concentrations in the GTPase reaction buffer allows continuous progression of the GTPase cycle and faster hydrolysis of GTP. The assay relies on enzymatic conversion of GTP that remains after the GTPase reaction to ATP and detection of the generated ATP using the luciferin/luciferase combination. The GTPase/GAP/GEF-Glo assay system enables monitoring of GTPase, GAP-stimulated GTPase, GAP, and GEF activities. The system can also be used to analyze these proteins when expressed in cells as fusion proteins by performing the assay in a pulldown format. The assays showed minimal false hits upon testing for compound interference using the library of pharmacologically active compounds and its robustness was demonstrated by a high Z′-factor of 0.93 and CV of 2.2%. The assay system has a high dynamic range, formatted in a convenient add–mix–read, and applicable to high-throughput screening.
Collapse
Affiliation(s)
- Subhanjan Mondal
- 1 Research and Development , Promega Corporation, Madison, Wisconsin
| | - Kevin Hsiao
- 1 Research and Development , Promega Corporation, Madison, Wisconsin
| | - Said A Goueli
- 1 Research and Development , Promega Corporation, Madison, Wisconsin.,2 Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health , Madison, Wisconsin
| |
Collapse
|
6
|
Evelyn CR, Biesiada J, Duan X, Tang H, Shang X, Papoian R, Seibel WL, Nelson S, Meller J, Zheng Y. Combined rational design and a high throughput screening platform for identifying chemical inhibitors of a Ras-activating enzyme. J Biol Chem 2015; 290:12879-98. [PMID: 25825487 DOI: 10.1074/jbc.m114.634493] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Indexed: 11/06/2022] Open
Abstract
The Ras family small GTPases regulate multiple cellular processes, including cell growth, survival, movement, and gene expression, and are intimately involved in cancer pathogenesis. Activation of these small GTPases is catalyzed by a special class of enzymes, termed guanine nucleotide exchange factors (GEFs). Herein, we developed a small molecule screening platform for identifying lead hits targeting a Ras GEF enzyme, SOS1. We employed an ensemble structure-based virtual screening approach in combination with a multiple tier high throughput experimental screen utilizing two complementary fluorescent guanine nucleotide exchange assays to identify small molecule inhibitors of GEF catalytic activity toward Ras. From a library of 350,000 compounds, we selected a set of 418 candidate compounds predicted to disrupt the GEF-Ras interaction, of which dual wavelength GDP dissociation and GTP-loading experimental screening identified two chemically distinct small molecule inhibitors. Subsequent biochemical validations indicate that they are capable of dose-dependently inhibiting GEF catalytic activity, binding to SOS1 with micromolar affinity, and disrupting GEF-Ras interaction. Mutagenesis studies in conjunction with structure-activity relationship studies mapped both compounds to different sites in the catalytic pocket, and both inhibited Ras signaling in cells. The unique screening platform established here for targeting Ras GEF enzymes could be broadly useful for identifying lead inhibitors for a variety of small GTPase-activating GEF reactions.
Collapse
Affiliation(s)
- Chris R Evelyn
- From the Division of Experimental Hematology and Cancer Biology
| | | | - Xin Duan
- From the Division of Experimental Hematology and Cancer Biology
| | - Hong Tang
- Division of Immunobiology, and the Drug Discovery Center and
| | - Xun Shang
- From the Division of Experimental Hematology and Cancer Biology
| | - Ruben Papoian
- the Drug Discovery Center and Departments of Neurology and
| | - William L Seibel
- the Drug Discovery Center and Division of Oncology, Children's Hospital Research Foundation, Cincinnati, Ohio 45229 and
| | | | - Jaroslaw Meller
- Division of Biomedical Informatics, Environmental Health, University of Cincinnati, Cincinnati, Ohio 45267
| | - Yi Zheng
- From the Division of Experimental Hematology and Cancer Biology,
| |
Collapse
|
7
|
Evelyn CR, Duan X, Biesiada J, Seibel WL, Meller J, Zheng Y. Rational design of small molecule inhibitors targeting the Ras GEF, SOS1. ACTA ACUST UNITED AC 2014; 21:1618-28. [PMID: 25455859 DOI: 10.1016/j.chembiol.2014.09.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 09/02/2014] [Accepted: 09/05/2014] [Indexed: 01/21/2023]
Abstract
Ras GTPases regulate intracellular signaling involved in cell proliferation. Elevated Ras signaling activity has been associated with human cancers. Ras activation is catalyzed by guanine nucleotide exchange factors (GEFs), of which SOS1 is a major member that transduces receptor tyrosine kinase signaling to Ras. We have developed a rational approach coupling virtual screening with experimental screening in identifying small-molecule inhibitors targeting the catalytic site of SOS1 and SOS1-regulated Ras activity. A lead inhibitor, NSC-658497, was found to bind to SOS1, competitively suppress SOS1-Ras interaction, and dose-dependently inhibit SOS1 GEF activity. Mutagenesis and structure-activity relationship studies map the NSC-658497 site of action to the SOS1 catalytic site, and define the chemical moieties in the inhibitor essential for the activity. NSC-658497 showed dose-dependent efficacy in inhibiting Ras, downstream signaling activities, and associated cell proliferation. These studies establish a proof of principle for rational design of small-molecule inhibitors targeting Ras GEF enzymatic activity.
Collapse
Affiliation(s)
- Chris R Evelyn
- Division of Experimental Hematology and Cancer Biology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
| | - Xin Duan
- Division of Experimental Hematology and Cancer Biology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
| | - Jacek Biesiada
- Division of Biomedical Informatics, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
| | - William L Seibel
- Division of Oncology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
| | - Jaroslaw Meller
- Division of Biomedical Informatics, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA; Department of Environmental Health, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Yi Zheng
- Division of Experimental Hematology and Cancer Biology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA.
| |
Collapse
|
8
|
Parkinson disease-associated mutation R1441H in LRRK2 prolongs the "active state" of its GTPase domain. Proc Natl Acad Sci U S A 2014; 111:4055-60. [PMID: 24591621 DOI: 10.1073/pnas.1323285111] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD). A disease-causing point mutation R1441H/G/C in the GTPase domain of LRRK2 leads to overactivation of its kinase domain. However, the mechanism by which this mutation alters the normal function of its GTPase domain [Ras of complex proteins (Roc)] remains unclear. Here, we report the effects of R1441H mutation (RocR1441H) on the structure and activity of Roc. We show that Roc forms a stable monomeric conformation in solution that is catalytically active, thus demonstrating that LRRK2 is a bona fide self-contained GTPase. We further show that the R1441H mutation causes a twofold reduction in GTPase activity without affecting the structure, thermal stability, and GDP-binding affinity of Roc. However, the mutation causes a twofold increase in GTP-binding affinity of Roc, thus suggesting that the PD-causing mutation R1441H traps Roc in a more persistently activated state by increasing its affinity for GTP and, at the same time, compromising its GTP hydrolysis.
Collapse
|
9
|
Gαi2 signaling: friend or foe in cardiac injury and heart failure? Naunyn Schmiedebergs Arch Pharmacol 2012; 385:443-53. [PMID: 22411356 DOI: 10.1007/s00210-011-0705-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 10/13/2011] [Indexed: 12/20/2022]
Abstract
Receptors coupled to G proteins have many effects on the heart. Enhanced signaling by Gα(s) and Gα(q) leads to cardiac injury and heart failure, while Gα(i2) signaling in cardiac myocytes can protect against ischemic injury and β-adrenergic-induced heart failure. We asked whether enhanced Gα(i2) signaling in mice could protect against heart failure using a point mutation in Gα(i2) (G184S), which prevents negative regulation by regulators of G protein signaling. Contrary to our expectation, it worsened effects of a genetic dilated cardiomyopathy (DCM) and catecholamine-induced cardiac injury. Gα (i2) (G184S/+) /DCM double heterozygote mice (TG9(+)Gα (i2) (G184S/+)) had substantially decreased survival compared to DCM animals. Furthermore, heart weight/body weight ratios (HW/BW) were significantly greater in TG9(+)Gα (i2) (G184S/+) mice as was expression of natriuretic peptide genes. Catecholamine injury in Gα (i2) (G184S/G184S) mutant mice produced markedly increased isoproterenol-induced fibrosis and collagen III gene expression vs WT mice. Cardiac fibroblasts from Gα (i2) (G184S/G184S) mice also showed a serum-dependent increase in proliferation and ERK phosphorylation, which were blocked by pertussis toxin and a mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor. Gα(i2) signaling in cardiac myocytes protects against ischemic injury but enhancing Gα(i2) signaling overall may have detrimental effects in heart failure, perhaps through actions on cardiac fibroblasts.
Collapse
|
10
|
Preininger AM, Kaya AI, Gilbert JA, Busenlehner LS, Armstrong RN, Hamm HE. Myristoylation exerts direct and allosteric effects on Gα conformation and dynamics in solution. Biochemistry 2012; 51:1911-24. [PMID: 22329346 DOI: 10.1021/bi201472c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Coupling of heterotrimeric G proteins to activated G protein-coupled receptors results in nucleotide exchange on the Gα subunit, which in turn decreases its affinity for both Gβγ and activated receptors. N-Terminal myristoylation of Gα subunits aids in membrane localization of inactive G proteins. Despite the presence of the covalently attached myristoyl group, Gα proteins are highly soluble after GTP binding. This study investigated factors facilitating the solubility of the activated, myristoylated protein. In doing so, we also identified myristoylation-dependent differences in regions of Gα known to play important roles in interactions with receptors, effectors, and nucleotide binding. Amide hydrogen-deuterium exchange and site-directed fluorescence of activated proteins revealed a solvent-protected amino terminus that was enhanced by myristoylation. Furthermore, fluorescence quenching confirmed that the myristoylated amino terminus is in proximity to the Switch II region in the activated protein. Myristoylation also stabilized the interaction between the guanine ring and the base of the α5 helix that contacts the bound nucleotide. The allosteric effects of myristoylation on protein structure, function, and localization indicate that the myristoylated amino terminus of Gα(i) functions as a myristoyl switch, with implications for myristoylation in the stabilization of nucleotide binding and in the spatial regulation of G protein signaling.
Collapse
Affiliation(s)
- Anita M Preininger
- Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States
| | | | | | | | | | | |
Collapse
|
11
|
Muller RE, Klein KR, Hutsell SQ, Siderovski DP, Kimple AJ. A homogeneous method to measure nucleotide exchange by α-subunits of heterotrimeric G-proteins using fluorescence polarization. Assay Drug Dev Technol 2010; 8:621-4. [PMID: 20662737 DOI: 10.1089/adt.2010.0286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The mainstay of assessing guanosine diphosphate release by the α-subunit of a heterotrimeric G-protein is the [³⁵S]guanosine 5'-O-(3-thiotriphosphate) (GTPγS) radionucleotide-binding assay. This assay requires separation of protein-bound GTPγS from free GTPγS at multiple time points followed by quantification via liquid scintillation. The arduous nature of this assay makes it difficult to quickly characterize multiple mutants, determine the effects of individual variables (e.g., temperature and Mg(2+) concentration) on nucleotide exchange, or screen for small molecule modulators of Gα nucleotide binding/cycling properties. Here, we describe a robust, homogeneous, fluorescence polarization assay using a red-shifted fluorescent GTPγS probe that can rapidly determine the rate of GTPγS binding by Gα subunits.
Collapse
Affiliation(s)
- Robin E Muller
- Department of Pharmacology, UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA
| | | | | | | | | |
Collapse
|
12
|
Evelyn CR, Ferng T, Rojas RJ, Larsen MJ, Sondek J, Neubig RR. High-throughput screening for small-molecule inhibitors of LARG-stimulated RhoA nucleotide binding via a novel fluorescence polarization assay. ACTA ACUST UNITED AC 2009; 14:161-72. [PMID: 19196702 DOI: 10.1177/1087057108328761] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Guanine nucleotide exchange factors (GEFs) stimulate guanine nucleotide exchange and the subsequent activation of Rho-family proteins in response to extracellular stimuli acting upon cytokine, tyrosine kinase, adhesion, integrin, and G-protein-coupled receptors (GPCRs). Upon Rho activation, several downstream events occur, such as morphological and cytoskeletal changes, motility, growth, survival, and gene transcription. The leukemia-associated RhoGEF (LARG) is a member of the regulators of G-protein signaling homology domain (RH) family of GEFs originally identified as a result of chromosomal translocation in acute myeloid leukemia. Using a novel fluorescence polarization guanine nucleotide-binding assay using BODIPY-Texas Red-GTPgammaS (BODIPY-TR-GTPgammaS), the authors performed a 10,000-compound high-throughput screen for inhibitors of LARG-stimulated RhoA nucleotide binding. Five compounds identified from the high-throughput screen were confirmed in a nonfluorescent radioactive guanine nucleotide-binding assay measuring LARG-stimulated [( 35)S] GTPgammaS binding to RhoA, thus ruling out nonspecific fluorescent effects. All 5 compounds selectively inhibited LARG-stimulated RhoA [( 35)S] GTPgammaS binding but had little to no effect on RhoA or Galpha( o) [(35)S] GTPgammaS binding. Therefore, these 5 compounds should serve as promising starting points for the development of small-molecule inhibitors of LARG-mediated nucleotide exchange as both pharmacological tools and therapeutics. In addition, the fluorescence polarization guanine nucleotide-binding assay described here should serve as a useful approach for both high-throughput screening and general biological applications.
Collapse
Affiliation(s)
- Chris R Evelyn
- Department of Pharmacology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0632, USA
| | | | | | | | | | | |
Collapse
|
13
|
Lai TS, Liu Y, Tucker T, Daniel KR, Sane DC, Toone E, Burke JR, Strittmatter WJ, Greenberg CS. Identification of chemical inhibitors to human tissue transglutaminase by screening existing drug libraries. ACTA ACUST UNITED AC 2008; 15:969-78. [PMID: 18804034 DOI: 10.1016/j.chembiol.2008.07.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 07/16/2008] [Accepted: 07/23/2008] [Indexed: 12/20/2022]
Abstract
Human tissue transglutaminase (TGM2) is a calcium-dependent crosslinking enzyme involved in the posttranslational modification of intra- and extracellular proteins and implicated in several neurodegenerative diseases. To find specific inhibitors to TGM2, two structurally diverse chemical libraries (LOPAC and Prestwick) were screened. We found that ZM39923, a Janus kinase inhibitor, and its metabolite ZM449829 were the most potent inhibitors with IC(50) of 10 and 5 nM, respectively. In addition, two other inhibitors, including tyrphostin 47 and vitamin K(3), were found to have an IC(50) in the micromolar range. These agents used in part a thiol-dependent mechanism to inhibit TGM2, consistent with the activation of TGM2 by reduction of an intramolecular disulfide bond. These inhibitors were tested in a polyglutamine-expressing Drosophila model of neurodegeneration and found to improve survival. The TGM2 inhibitors we discovered may serve as valuable lead compounds for the development of orally active TGM2 inhibitors to treat human diseases.
Collapse
Affiliation(s)
- Thung-S Lai
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Lai TS, Liu Y, Li W, Greenberg CS. Identification of two GTP-independent alternatively spliced forms of tissue transglutaminase in human leukocytes, vascular smooth muscle, and endothelial cells. FASEB J 2007; 21:4131-43. [PMID: 17609251 PMCID: PMC2157556 DOI: 10.1096/fj.06-7598com] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Tissue transglutaminase (tTG) is a multifunctional enzyme with transglutaminase crosslinking (TGase), GTP binding, and hydrolysis activities that play a role in many different disorders. We identified, characterized, and investigated the function and stability of two alternatively spliced forms of tTG using biochemical, cellular, and molecular biological approaches. Using a human aortic vascular smooth muscle cells (VSMC) cDNA library, we identified two cDNAs encoding C-terminal truncated forms, tTG(V1) and tTG(V2). tTG(V1,2) mRNAs were synthesized by a rare splicing event using alternate splice sites within exons 12 and 13 of the tTG gene, respectively. Quantitative PCR and immunoblotting demonstrated that there was unique expression and localization of tTG(V1,2) compared with tTG in human umbilical vein endothelial cells (HUVECs), VSMC, and leukocytes. The loss of C-terminal 52 amino acid residues (AAs) in tTG(V1,2) altered GTP binding, enhanced GTP hydrolysis, rendered the variants insensitive to GTP inhibition, and resulted in <10% residual Ca(+2)-dependent TGase activity. Transfection in HEK293 demonstrated a 28- and 5-fold reduction in the expression of tTG(V1) and tTG(V2), respectively, demonstrating that the C-terminal GTP-binding domain is important in stabilizing and promoting the half-life of tTG. The altered affinity for GTP allowed tTG(V1,2) to exhibit enhanced TGase activity when there is a transient increase in Ca(+2) levels. The abundance of tTG(V1,2) and its distinct intracellular expression patterns in human vascular cells and leukocytes indicate these isoforms likely have unique physiological functions.
Collapse
Affiliation(s)
- Thung-S Lai
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | |
Collapse
|
15
|
Zeller CE, Parnell SC, Dohlman HG. The RACK1 ortholog Asc1 functions as a G-protein beta subunit coupled to glucose responsiveness in yeast. J Biol Chem 2007; 282:25168-76. [PMID: 17591772 DOI: 10.1074/jbc.m702569200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
According to the prevailing paradigm, G-proteins are composed of three subunits, an alpha subunit with GTPase activity and a tightly associated betagamma subunit complex. In the yeast Saccharomyces cerevisiae there are two known Galpha proteins (Gpa1 and Gpa2) but only one Gbetagamma, which binds only to Gpa1. Here we show that the yeast ortholog of RACK1 (receptor for activated protein kinase C1) Asc1 functions as the Gbeta for Gpa2. As with other known Gbeta proteins, Asc1 has a 7-WD domain structure, interacts directly with the Galpha in a guanine nucleotide-dependent manner, and inhibits Galpha guanine nucleotide exchange activity. In addition, Asc1 binds to the effector enzyme adenylyl cyclase (Cyr1), and diminishes the production of cAMP in response to glucose stimulation. Thus, whereas Gpa2 promotes glucose signaling through elevated production of cAMP, Asc1 has opposing effects on these same processes. Our findings reveal the existence of an unusual Gbeta subunit, one having multiple functions within the cell in addition to serving as a signal transducer for cell surface receptors and intracellular effectors.
Collapse
Affiliation(s)
- Corinne E Zeller
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | | | | |
Collapse
|
16
|
Willard FS, Kimple AJ, Johnston CA, Siderovski DP. A direct fluorescence-based assay for RGS domain GTPase accelerating activity. Anal Biochem 2005; 340:341-51. [PMID: 15840508 DOI: 10.1016/j.ab.2005.02.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Indexed: 11/17/2022]
Abstract
Diverse extracellular signals regulate seven transmembrane-spanning receptors to modulate cellular physiology. These receptors signal primarily through activation of heterotrimeric guanine nucleotide binding proteins (G proteins). A major determinant of heterotrimeric G protein signaling in vivo and in vitro is the intrinsic GTPase activity of the Galpha subunit. RGS (regulator of G protein signaling) domain-containing proteins are GTPase accelerating proteins specific for Galpha subunits. In this article, we describe the use of the ribose-conjugated fluorescent guanine nucleotide analog BODIPYFL-GTP as a spectroscopic probe to measure intrinsic and RGS protein-catalyzed nucleotide hydrolysis by Galphao. BODIPYFL-GTP bound to Galphao exhibits a 200% increase in fluorescence quantum yield. Hydrolysis of BODIPYFL-GTP to BODIPYFL-GDP reduces the quantum yield to 27% above its unbound value. We demonstrate that BODIPYFL-GTP can be used as a rapid real-time probe for measuring RGS domain-catalyzed GTP hydrolysis by Galphao. We demonstrate the effectiveness of this assay in the analysis of loss-of-function point mutants of both Galphao and RGS12. This assay should be useful in screening for and analyzing RGS protein inhibitory compounds.
Collapse
Affiliation(s)
- Francis S Willard
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | | | | | | |
Collapse
|
17
|
Siderovski DP, Willard FS. The GAPs, GEFs, and GDIs of heterotrimeric G-protein alpha subunits. Int J Biol Sci 2005; 1:51-66. [PMID: 15951850 PMCID: PMC1142213 DOI: 10.7150/ijbs.1.51] [Citation(s) in RCA: 317] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 02/01/2005] [Indexed: 12/21/2022] Open
Abstract
The heterotrimeric G-protein alpha subunit has long been considered a bimodal, GTP-hydrolyzing switch controlling the duration of signal transduction by seven-transmembrane domain (7TM) cell-surface receptors. In 1996, we and others identified a superfamily of “regulator of G-protein signaling” (RGS) proteins that accelerate the rate of GTP hydrolysis by Gα subunits (dubbed GTPase-accelerating protein or “GAP” activity). This discovery resolved the paradox between the rapid physiological timing seen for 7TM receptor signal transduction in vivo and the slow rates of GTP hydrolysis exhibited by purified Gα subunits in vitro. Here, we review more recent discoveries that have highlighted newly-appreciated roles for RGS proteins beyond mere negative regulators of 7TM signaling. These new roles include the RGS-box-containing, RhoA-specific guanine nucleotide exchange factors (RGS-RhoGEFs) that serve as Gα effectors to couple 7TM and semaphorin receptor signaling to RhoA activation, the potential for RGS12 to serve as a nexus for signaling from tyrosine kinases and G-proteins of both the Gα and Ras-superfamilies, the potential for R7-subfamily RGS proteins to couple Gα subunits to 7TM receptors in the absence of conventional Gβγ dimers, and the potential for the conjoint 7TM/RGS-box Arabidopsis protein AtRGS1 to serve as a ligand-operated GAP for the plant Gα AtGPA1. Moreover, we review the discovery of novel biochemical activities that also impinge on the guanine nucleotide binding and hydrolysis cycle of Gα subunits: namely, the guanine nucleotide dissociation inhibitor (GDI) activity of the GoLoco motif-containing proteins and the 7TM receptor-independent guanine nucleotide exchange factor (GEF) activity of Ric‑8/synembryn. Discovery of these novel GAP, GDI, and GEF activities have helped to illuminate a new role for Gα subunit GDP/GTP cycling required for microtubule force generation and mitotic spindle function in chromosomal segregation.
Collapse
Affiliation(s)
- David P Siderovski
- Department of Pharmacology, UNC Lineberger Comprehensive Cancer Center, and UNC Neuroscience Center, The University of North Carolina at Chapel Hill, CB#7365, 1106 M.E. Jones Building, Chapel Hill, NC 27599-7365 USA.
| | | |
Collapse
|
18
|
Willard FS, Siderovski DP. Purification and in vitro functional analysis of the Arabidopsis thaliana regulator of G-protein signaling-1. Methods Enzymol 2004; 389:320-38. [PMID: 15313574 DOI: 10.1016/s0076-6879(04)89019-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Abstract
The model organism Arabidopsis thaliana contains a restricted set of heterotrimeric G-protein subunits, with only one canonical Galpha subunit (AtGPA1), one Gbeta subunit (AtAGB1), and two Ggamma subunits (AtAGG1 and AtGG2) identified. We have identified a novel additional component of heterotrimeric G-protein signaling in the A. thaliana genome, regulator of G-protein signaling-1 (AtRGS1). This protein has the predicted topology and structure of a G-protein-coupled receptor in that it contains seven transmembrane domains, but AtRGS1 also contains a unique C-terminal extension, namely a regulator of G-protein signaling domain (RGS box). This article describes methods for the purification and in vitro functional analysis of the RGS box of AtRGS1.
Collapse
Affiliation(s)
- Francis S Willard
- Department of Pharmacology, The University of North Carolina at Chapel Hill, 27599-7365, USA
| | | |
Collapse
|
19
|
Korlach J, Baird DW, Heikal AA, Gee KR, Hoffman GR, Webb WW. Spontaneous nucleotide exchange in low molecular weight GTPases by fluorescently labeled gamma-phosphate-linked GTP analogs. Proc Natl Acad Sci U S A 2004; 101:2800-5. [PMID: 14973186 PMCID: PMC365700 DOI: 10.1073/pnas.0308579100] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Regulated guanosine nucleotide exchange and hydrolysis constitute the fundamental activities of low molecular weight GTPases. We show that three guanosine 5'-triphosphate analogs with BODIPY fluorophores coupled via the gamma phosphate bind to the GTPases Cdc42, Rac1, RhoA, and Ras and displace guanosine 5'-diphosphate with high intrinsic exchange rates in the presence of Mg(2+) ions, thereby acting as synthetic, low molecular weight guanine nucleotide exchange factors. The accompanying large fluorescence enhancements (as high as 12-fold), caused by a reduction in guanine quenching of the environmentally sensitive BODIPY dye fluorescence on protein binding, allow for real-time monitoring of this spontaneous nucleotide exchange in the visible spectrum with high signal-to-noise ratios. Binding affinities increased with longer aliphatic linkers connecting the nucleotide and BODIPY fluorophore and were in the 10-100 nM range. Steady-state and time-resolved fluorescence spectroscopy showed an inverse relationship between linker length and fluorescence enhancement factors and differences in protein-bound fluorophore mobilities, providing optimization criteria for future applications of such compounds as efficient elicitors and reporters of nucleotide exchange. EDTA markedly enhanced nucleotide exchange, enabling rapid loading of GTPases with these probes. Differences in active site geometries, in the absence of Mg(2+), caused qualitatively different reporting of the bound state by the different analogs. The BODIPY analogs also prevented the interaction of Cdc42 with p21 activated kinase. Together, these results validate the use of these analogs as valuable tools for studying GTPase functions and for developing potent synthetic nucleotide exchange factors for this important class of signaling molecules.
Collapse
Affiliation(s)
- Jonas Korlach
- Field of Biochemistry, Molecular and Cell Biology, School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
| | | | | | | | | | | |
Collapse
|