1
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Hu Z, Martí J. Isomer-sourced structure iteration methods for in silico development of inhibitors: Inducing GTP-bound NRAS-Q61 oncogenic mutations to an "off-like" state. Comput Struct Biotechnol J 2024; 23:2418-2428. [PMID: 38882681 PMCID: PMC11176632 DOI: 10.1016/j.csbj.2024.05.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 05/20/2024] [Accepted: 05/21/2024] [Indexed: 06/18/2024] Open
Abstract
The NRAS-mutant subset of melanoma represent some of the most aggressive and deadliest types associated with poor overall survival. Unfortunately, for more than 40 years, no therapeutic agent directly targeting NRAS mutations has been clinically approved. In this work, based on microsecond scale molecular dynamics simulations, the effect of Q61 mutations on NRAS conformational characteristics is revealed at the atomic level. The GTP-bound NRAS-Q61R and Q61K mutations show a specific targetable pocket between Switch-II and α-helix 3 whereas the NRAS-Q61L non-polar mutation category shows a different targetable pocket. Moreover, a new isomer-sourced structure iteration method has been developed for the in silico design of potential inhibitor prototypes for oncogenes. We show the possibility of a designed prototype HM-387 to target activated NRAS-Q61R and that it can gradually induce the transition from the activated NRAS-Q61R to an "off-like" state.
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Affiliation(s)
- Zheyao Hu
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, B4-B5 Northern Campus UPC, Barcelona, 08034, Catalonia, Spain
| | - Jordi Martí
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, B4-B5 Northern Campus UPC, Barcelona, 08034, Catalonia, Spain
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2
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Healy FM, Turner AL, Marensi V, MacEwan DJ. Mediating kinase activity in Ras-mutant cancer: potential for an individualised approach? Front Pharmacol 2024; 15:1441938. [PMID: 39372214 PMCID: PMC11450236 DOI: 10.3389/fphar.2024.1441938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Accepted: 09/06/2024] [Indexed: 10/08/2024] Open
Abstract
It is widely acknowledged that there is a considerable number of oncogenic mutations within the Ras superfamily of small GTPases which are the driving force behind a multitude of cancers. Ras proteins mediate a plethora of kinase pathways, including the MAPK, PI3K, and Ral pathways. Since Ras was considered undruggable until recently, pharmacological targeting of pathways downstream of Ras has been attempted to varying success, though drug resistance has often proven an issue. Nuances between kinase pathway activation in the presence of various Ras mutants are thought to contribute to the resistance, however, the reasoning behind activation of different pathways in different Ras mutational contexts is yet to be fully elucidated. Indeed, such disparities often depend on cancer type and disease progression. However, we are in a revolutionary age of Ras mutant targeted therapy, with direct-targeting KRAS-G12C inhibitors revolutionising the field and achieving FDA-approval in recent years. However, these are only beneficial in a subset of patients. Approximately 90% of Ras-mutant cancers are not KRAS-G12C mutant, and therefore raises the question as to whether other distinct amino acid substitutions within Ras may one day be targetable in a similar manner, and indeed whether better understanding of the downstream pathways these various mutants activate could further improve therapy. Here, we discuss the favouring of kinase pathways across an array of Ras-mutant oncogenic contexts and assess recent advances in pharmacological targeting of various Ras mutants. Ultimately, we will examine the utility of individualised pharmacological approaches to Ras-mediated cancer.
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Affiliation(s)
- Fiona M. Healy
- Department of Pharmacology and Therapeutics, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Amy L. Turner
- Department of Pharmacology and Therapeutics, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Vanessa Marensi
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
- Chester Medical School, University of Chester, Chester, United Kingdom
| | - David J. MacEwan
- Department of Pharmacology and Therapeutics, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
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3
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Fink JC, Landry D, Webb LJ. Probing the Electrostatic Effects of H-Ras Tyrosine 32 Mutations on Intrinsic GTP Hydrolysis Using Vibrational Stark Effect Spectroscopy of a Thiocyanate Probe. Biochemistry 2024; 63:1752-1760. [PMID: 38967549 DOI: 10.1021/acs.biochem.4c00075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
The wildtype H-Ras protein functions as a molecular switch in a variety of cell signaling pathways, and mutations to key residues result in a constitutively active oncoprotein. However, there is some debate regarding the mechanism of the intrinsic GTPase activity of H-Ras. It has been hypothesized that ordered water molecules are coordinated at the active site by Q61, a highly transforming amino acid site, and Y32, a position that has not previously been investigated. Here, we examine the electrostatic contribution of the Y32 position to GTP hydrolysis by comparing the rate of GTP hydrolysis of Y32X mutants to the vibrational energy shift of each mutation measured by a nearby thiocyanate vibrational probe to estimate changes in the electrostatic environment caused by changes at the Y32 position. We further compared vibrational energy shifts for each mutation to the hydration potential of the respective side chain and demonstrated that Y32 is less critical for recruiting water molecules into the active site to promote hydrolysis than Q61. Our results show a clear interplay between a steric contribution from Y32 and an electrostatic contribution from Q61 that are both critical for intrinsic GTP hydrolysis.
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Affiliation(s)
- Jackson C Fink
- Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Danielle Landry
- Department of Chemistry, Texas Materials Institute, and Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Lauren J Webb
- Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
- Department of Chemistry, Texas Materials Institute, and Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
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4
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Hu F, Wang Y, Zeng J, Deng X, Xia F, Xu X. Unveiling the State Transition Mechanisms of Ras Proteins through Enhanced Sampling and QM/MM Simulations. J Phys Chem B 2024; 128:1418-1427. [PMID: 38323538 DOI: 10.1021/acs.jpcb.3c07666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
In cells, wild-type RasGTP complexes exist in two distinct states: active State 2 and inactive State 1. These complexes regulate their functions by transitioning between the two states. However, the mechanisms underlying this state transition have not been clearly elucidated. To address this, we conducted a detailed simulation study to characterize the energetics of the stable states involved in the state transitions of the HRasGTP complex, specifically from State 2 to State 1. This was achieved by employing multiscale quantum mechanics/molecular mechanics and enhanced sampling molecular dynamics methods. Based on the simulation results, we constructed the two-dimensional free energy landscapes that provide crucial information about the conformational changes of the HRasGTP complex from State 2 to State 1. Furthermore, we also explored the conformational changes from the intermediate state to the product state during guanosine triphosphate hydrolysis. This study on the conformational changes involved in the HRas state transitions serves as a valuable reference for understanding the corresponding events of both KRas and NRas as well.
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Affiliation(s)
- Fangchen Hu
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Yiqiu Wang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Juan Zeng
- School of Biomedical Engineering, Guangdong Medical University, Dongguan 523808, China
| | - Xianming Deng
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Fei Xia
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Xin Xu
- Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, MOE Key Laboratory of Computational Physical Sciences, Department of Chemistry, Fudan University, Shanghai 200433, China
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5
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Berta D, Gehrke S, Nyíri K, Vértessy BG, Rosta E. Mechanism-Based Redesign of GAP to Activate Oncogenic Ras. J Am Chem Soc 2023; 145:20302-20310. [PMID: 37682266 PMCID: PMC10515638 DOI: 10.1021/jacs.3c04330] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Indexed: 09/09/2023]
Abstract
Ras GTPases play a crucial role in cell signaling pathways. Mutations of the Ras gene occur in about one third of cancerous cell lines and are often associated with detrimental clinical prognosis. Hot spot residues Gly12, Gly13, and Gln61 cover 97% of oncogenic mutations, which impair the enzymatic activity in Ras. Using QM/MM free energy calculations, we present a two-step mechanism for the GTP hydrolysis catalyzed by the wild-type Ras.GAP complex. We found that the deprotonation of the catalytic water takes place via the Gln61 as a transient Brønsted base. We also determined the reaction profiles for key oncogenic Ras mutants G12D and G12C using QM/MM minimizations, matching the experimentally observed loss of catalytic activity, thereby validating our reaction mechanism. Using the optimized reaction paths, we devised a fast and accurate procedure to design GAP mutants that activate G12D Ras. We replaced GAP residues near the active site and determined the activation barrier for 190 single mutants. We furthermore built a machine learning for ultrafast screening, by fast prediction of the barrier heights, tested both on the single and double mutations. This work demonstrates that fast and accurate screening can be accomplished via QM/MM reaction path optimizations to design protein sequences with increased catalytic activity. Several GAP mutations are predicted to re-enable catalysis in oncogenic G12D, offering a promising avenue to overcome aberrant Ras-driven signal transduction by activating enzymatic activity instead of inhibition. The outlined computational screening protocol is readily applicable for designing ligands and cofactors analogously.
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Affiliation(s)
- Dénes Berta
- Department
of Physics and Astronomy, University College
London, Gower Street, London WC1E
6BT, United Kingdom
| | - Sascha Gehrke
- Department
of Physics and Astronomy, University College
London, Gower Street, London WC1E
6BT, United Kingdom
| | - Kinga Nyíri
- Institute
of Enzymology, Research Centre for Natural Sciences, Magyar tudósok körútja
2, Budapest 1117, Hungary
- Department
of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budafoki út 6-8, Budapest 1111, Hungary
| | - Beáta G. Vértessy
- Institute
of Enzymology, Research Centre for Natural Sciences, Magyar tudósok körútja
2, Budapest 1117, Hungary
- Department
of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budafoki út 6-8, Budapest 1111, Hungary
| | - Edina Rosta
- Department
of Physics and Astronomy, University College
London, Gower Street, London WC1E
6BT, United Kingdom
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6
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GAP positions catalytic H-Ras residue Q61 for GTP hydrolysis in molecular dynamics simulations, complicating chemical rescue of Ras deactivation. Comput Biol Chem 2023; 104:107835. [PMID: 36893567 DOI: 10.1016/j.compbiolchem.2023.107835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/01/2023] [Accepted: 02/16/2023] [Indexed: 03/05/2023]
Abstract
Functional interaction of Ras signaling proteins with upstream, negative regulatory GTPase activating proteins (GAPs) represents a crucial step in cellular decision making related to growth and survival. Key components of the catalytic transition state for Ras deactivation by GAP-accelerated hydrolysis of Ras-bound guanosine triphosphate (GTP) are thought to include an arginine residue from the GAP (the arginine finger), a glutamine residue from Ras (Q61), and a water molecule that is likely coordinated by Q61 to engage in nucleophilic attack on GTP. Here, we use in-vitro fluorescence experiments to show that 0.1-100 mM concentrations of free arginine, imidazole, and other small nitrogenous molecule fail to accelerate GTP hydrolysis, even in the presence of the catalytic domain of a mutant GAP lacking its arginine finger (R1276A NF1). This result is surprising given that imidazole can chemically rescue enzyme activity in arginine-to-alanine mutant protein tyrosine kinases (PTKs) that share many active site components with Ras/GAP complexes. Complementary all-atom molecular dynamics (MD) simulations reveal that an arginine finger GAP mutant still functions to enhance Ras Q61-GTP interaction, though less extensively than wild-type GAP. This increased Q61-GTP proximity may promote more frequent fluctuations into configurations that enable GTP hydrolysis as a component of the mechanism by which GAPs accelerate Ras deactivation in the face of arginine finger mutations. The failure of small molecule analogs of arginine to chemically rescue catalytic deactivation of Ras is consistent with the idea that the influence of the GAP goes beyond the simple provision of its arginine finger. However, the failure of chemical rescue in the presence of R1276A NF1 suggests that the GAPs arginine finger is either unsusceptible to rescue due to exquisite positioning or that it is involved in complex multivalent interactions. Therefore, in the context of oncogenic Ras proteins with mutations at codons 12 or 13 that inhibit arginine finger penetration toward GTP, drug-based chemical rescue of GTP hydrolysis may have bifunctional chemical/geometric requirements that are more difficult to satisfy than those that result from arginine-to-alanine mutations in other enzymes for which chemical rescue has been demonstrated.
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7
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Huynh MV, Hobbs GA, Schaefer A, Pierobon M, Carey LM, Diehl JN, DeLiberty JM, Thurman RD, Cooke AR, Goodwin CM, Cook JH, Lin L, Waters AM, Rashid NU, Petricoin EF, Campbell SL, Haigis KM, Simeone DM, Lyssiotis CA, Cox AD, Der CJ. Functional and biological heterogeneity of KRAS Q61 mutations. Sci Signal 2022; 15:eabn2694. [PMID: 35944066 PMCID: PMC9534304 DOI: 10.1126/scisignal.abn2694] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Missense mutations at the three hotspots in the guanosine triphosphatase (GTPase) RAS-Gly12, Gly13, and Gln61 (commonly known as G12, G13, and Q61, respectively)-occur differentially among the three RAS isoforms. Q61 mutations in KRAS are infrequent and differ markedly in occurrence. Q61H is the predominant mutant (at 57%), followed by Q61R/L/K (collectively 40%), and Q61P and Q61E are the rarest (2 and 1%, respectively). Probability analysis suggested that mutational susceptibility to different DNA base changes cannot account for this distribution. Therefore, we investigated whether these frequencies might be explained by differences in the biochemical, structural, and biological properties of KRASQ61 mutants. Expression of KRASQ61 mutants in NIH 3T3 fibroblasts and RIE-1 epithelial cells caused various alterations in morphology, growth transformation, effector signaling, and metabolism. The relatively rare KRASQ61E mutant stimulated actin stress fiber formation, a phenotype distinct from that of KRASQ61H/R/L/P, which disrupted actin cytoskeletal organization. The crystal structure of KRASQ61E was unexpectedly similar to that of wild-type KRAS, a potential basis for its weak oncogenicity. KRASQ61H/L/R-mutant pancreatic ductal adenocarcinoma (PDAC) cell lines exhibited KRAS-dependent growth and, as observed with KRASG12-mutant PDAC, were susceptible to concurrent inhibition of ERK-MAPK signaling and of autophagy. Our results uncover phenotypic heterogeneity among KRASQ61 mutants and support the potential utility of therapeutic strategies that target KRASQ61 mutant-specific signaling and cellular output.
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Affiliation(s)
- Minh V. Huynh
- Department of Biochemistry & Biophysics, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - G. Aaron Hobbs
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Antje Schaefer
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Mariaelena Pierobon
- Center for Applied Proteomics and Molecular Medicine,
George Mason University, Manassas, VA 20110, USA
| | - Leiah M. Carey
- Department of Biochemistry & Biophysics, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - J. Nathaniel Diehl
- Curriculum in Genetics and Molecular Biology, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jonathan M. DeLiberty
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ryan D. Thurman
- Department of Biochemistry & Biophysics, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Adelaide R. Cooke
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Craig M. Goodwin
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Joshua H. Cook
- Department of Cancer Biology, Dana-Farber Cancer Institute,
Boston, MA 02215, USA
- Department of Medicine, Brigham & Women's
Hospital, Harvard Medical School, Boston, MA 02115, USA
- Department of Biomedical Informatics, Harvard Medical
School, Boston, MA 02115, USA
| | - Lin Lin
- Department of Molecular and Integrative Physiology,
University of Michigan Health System, Ann Arbor, MI 48109, USA
| | - Andrew M. Waters
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Naim U. Rashid
- Department of Biostatistics, University of North Carolina
at Chapel Hill, NC 27955, USA
| | - Emanuel F. Petricoin
- Center for Applied Proteomics and Molecular Medicine,
George Mason University, Manassas, VA 20110, USA
| | - Sharon L. Campbell
- Department of Biochemistry & Biophysics, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kevin M. Haigis
- Department of Cancer Biology, Dana-Farber Cancer Institute,
Boston, MA 02215, USA
- Department of Medicine, Brigham & Women's
Hospital, Harvard Medical School, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
- Harvard Digestive Disease Center, Harvard Medical School,
Boston, MA 02115, USA
| | - Diane M. Simeone
- Perlmutter Cancer Center, New York University, New York,
NY10016, USA
| | - Costas A. Lyssiotis
- Department of Molecular and Integrative Physiology,
University of Michigan Health System, Ann Arbor, MI 48109, USA
- Department of Internal Medicine, Division of
Gastroenterology, University of Michigan, Ann Arbor, MI 48198, USA
- University of Michigan Comprehensive Cancer Center, Ann
Arbor, MI 48109, USA
| | - Adrienne D. Cox
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Radiation Oncology, University of North
Carolina at Chapel Hill, Chapel Hill, NC 2799, USA
| | - Channing J. Der
- Department of Pharmacology, University of North Carolina at
Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, University of
North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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8
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Murphy BM, Terrell EM, Chirasani VR, Weiss TJ, Lew RE, Holderbaum AM, Dhakal A, Posada V, Fort M, Bodnar MS, Carey LM, Chen M, Burd CJ, Coppola V, Morrison DK, Campbell SL, Burd CE. Enhanced BRAF engagement by NRAS mutants capable of promoting melanoma initiation. Nat Commun 2022; 13:3153. [PMID: 35672316 PMCID: PMC9174180 DOI: 10.1038/s41467-022-30881-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 05/24/2022] [Indexed: 01/07/2023] Open
Abstract
A distinct profile of NRAS mutants is observed in each tumor type. It is unclear whether these profiles are determined by mutagenic events or functional differences between NRAS oncoproteins. Here, we establish functional hallmarks of NRAS mutants enriched in human melanoma. We generate eight conditional, knock-in mouse models and show that rare melanoma mutants (NRAS G12D, G13D, G13R, Q61H, and Q61P) are poor drivers of spontaneous melanoma formation, whereas common melanoma mutants (NRAS Q61R, Q61K, or Q61L) induce rapid tumor onset with high penetrance. Molecular dynamics simulations, combined with cell-based protein-protein interaction studies, reveal that melanomagenic NRAS mutants form intramolecular contacts that enhance BRAF binding affinity, BRAF-CRAF heterodimer formation, and MAPK > ERK signaling. Along with the allelic series of conditional mouse models we describe, these results establish a mechanistic basis for the enrichment of specific NRAS mutants in human melanoma.
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Affiliation(s)
- Brandon M Murphy
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Elizabeth M Terrell
- Laboratory of Cell and Developmental Signaling, National Cancer Institute-Frederick, Frederick, MD, 21702, USA
| | - Venkat R Chirasani
- Department of Biochemistry & Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Tirzah J Weiss
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Rachel E Lew
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Andrea M Holderbaum
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Aastha Dhakal
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Valentina Posada
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Marie Fort
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Michael S Bodnar
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Leiah M Carey
- Department of Biochemistry & Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Min Chen
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
- Genetically Engineered Mouse Modeling Core, The Ohio State University, Columbus, OH, 43210, USA
| | - Craig J Burd
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA
| | - Vincenzo Coppola
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA
- Genetically Engineered Mouse Modeling Core, The Ohio State University, Columbus, OH, 43210, USA
| | - Deborah K Morrison
- Laboratory of Cell and Developmental Signaling, National Cancer Institute-Frederick, Frederick, MD, 21702, USA
| | - Sharon L Campbell
- Department of Biochemistry & Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Christin E Burd
- Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, 43210, USA.
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA.
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9
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Zeng J, Chen J, Xia F, Cui Q, Deng X, Xu X. Identification of functional substates of KRas during GTP hydrolysis with enhanced sampling simulations. Phys Chem Chem Phys 2022; 24:7653-7665. [PMID: 35297922 PMCID: PMC8972078 DOI: 10.1039/d2cp00274d] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
As the hub of major signaling pathways, Ras proteins are implicated in 19% of tumor-caused cancers due to perturbations in their conformational and/or catalytic properties. Despite numerous studies, the functions of the conformational substates for the most important isoform, KRas, remain elusive. In this work, we perform an extensive simulation analysis on the conformational landscape of KRas in its various chemical states during the GTP hydrolysis cycle: the reactant state KRasGTP·Mg2+, the intermediate state KRasGDP·Pi·Mg2+ and the product state KRasGDP·Mg2+. The results from enhanced sampling simulations reveal that State 1 of KRasGTP·Mg2+ has multiple stable substates in solution, one of which might account for interacting with GEFs. State 2 of KRasGTP·Mg2+ features two substates "Tyr32in" and "Tyr32out", which are poised to interact with effectors and GAPs, respectively. For the intermediate state KRasGDP·Pi·Mg2+, Gln61 and Pi are found to assume a broad set of conformations, which might account for the weak oncogenic effect of Gln61 mutations in KRas in contrast to the situation in HRas and NRas. Finally, the product state KRasGDP·Mg2+ has more than two stable substates in solution, pointing to a conformation-selection mechanism for complexation with GEFs. Based on these results, some specific inhibition strategies for targeting the binding sites of the high-energy substates of KRas during GTP hydrolysis are discussed.
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Affiliation(s)
- Juan Zeng
- School of Biomedical Engineering, Guangdong Medical University, Dongguan 523808, China
| | - Jian Chen
- School of Chemistry and Molecular Engineering, NYU-ECNU Center for Computational Chemistry at NYU Shanghai, East China Normal University, Shanghai 200062, China.
| | - Fei Xia
- School of Chemistry and Molecular Engineering, NYU-ECNU Center for Computational Chemistry at NYU Shanghai, East China Normal University, Shanghai 200062, China.
| | - Qiang Cui
- Departments of Chemistry, Physics and Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Xianming Deng
- State Key Laboratory of Cellular Stress Biology Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361101, China.
| | - Xin Xu
- Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, MOE Key Laboratory of Computational Physical Sciences, Department of Chemistry, Fudan University, Shanghai 200433, China.
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10
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Burge RA, Hobbs GA. Not all RAS mutations are equal: A detailed review of the functional diversity of RAS hot spot mutations. Adv Cancer Res 2022; 153:29-61. [PMID: 35101234 DOI: 10.1016/bs.acr.2021.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The RAS family of small GTPases are among the most frequently mutated oncogenes in human cancer. Approximately 20% of cancers harbor a RAS mutation, and >150 different missense mutations have been detected. Many of these mutations have mutant-specific biochemical defects that alter nucleotide binding and hydrolysis, effector interactions and cell signaling, prompting renewed efforts in the development of anti-RAS therapies, including the mutation-specific strategies. Previously viewed as undruggable, the recent FDA approval of a KRASG12C-selective inhibitor has offered real promise to the development of allele-specific RAS therapies. A broader understanding of the mutational consequences on RAS function must be developed to exploit additional allele-specific vulnerabilities. Approximately 94% of RAS mutations occur at one of three mutational "hot spots" at Gly12, Gly13 and Gln61. Further, the single-nucleotide substitutions represent >99% of these mutations. Within this scope, we discuss the mutational frequencies of RAS isoforms in cancer, mutant-specific effector interactions and biochemical properties. By limiting our analysis to this mutational subset, we simplify the analysis while only excluding a small percentage of total mutations. Combined, these data suggest that the presence or absence of select RAS mutations in human cancers can be linked to their biochemical properties. Continuing to examine the biochemical differences in each RAS-mutant protein will continue to provide additional breakthroughs in allele-specific therapeutic strategies.
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Affiliation(s)
- Rachel A Burge
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, United States
| | - G Aaron Hobbs
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC, United States; Hollings Cancer Center, Medical University of South Carolina, Charleston, SC, United States.
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11
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The Q61H mutation decouples KRAS from upstream regulation and renders cancer cells resistant to SHP2 inhibitors. Nat Commun 2021; 12:6274. [PMID: 34725361 PMCID: PMC8560773 DOI: 10.1038/s41467-021-26526-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 09/23/2021] [Indexed: 12/31/2022] Open
Abstract
Cancer cells bearing distinct KRAS mutations exhibit variable sensitivity to SHP2 inhibitors (SHP2i). Here we show that cells harboring KRAS Q61H are uniquely resistant to SHP2i, and investigate the underlying mechanisms using biophysics, molecular dynamics, and cell-based approaches. Q61H mutation impairs intrinsic and GAP-mediated GTP hydrolysis, and impedes activation by SOS1, but does not alter tyrosyl phosphorylation. Wild-type and Q61H-mutant KRAS are both phosphorylated by Src on Tyr32 and Tyr64 and dephosphorylated by SHP2, however, SHP2i does not reduce ERK phosphorylation in KRAS Q61H cells. Phosphorylation of wild-type and Gly12-mutant KRAS, which are associated with sensitivity to SHP2i, confers resistance to regulation by GAP and GEF activities and impairs binding to RAF, whereas the near-complete GAP/GEF-resistance of KRAS Q61H remains unaltered, and high-affinity RAF interaction is retained. SHP2 can stimulate KRAS signaling by modulating GEF/GAP activities and dephosphorylating KRAS, processes that fail to regulate signaling of the Q61H mutant. SHP2 promotes RAS-driven MAPK signalling, but it is unclear why cancer cells with distinct KRAS mutations exhibit differential sensitivity to SHP2 inhibition. Here the authors show that KRAS Q61H is decoupled from SHP2- mediated upstream regulation, thus Q61H pancreatic cancer cells maintain MAPK signalling and are refractory to SHP2 inhibitors.
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12
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Wertheim-Tysarowska K, Szczygielski O, Seliga K, Tysarowski A, Bal J, Michalak E, Rygiel AM, Sawicka E. The retrospective molecular analysis of large or giant congenital melanocytic nevi in a group of Polish children. JOURNAL OF MOTHER AND CHILD 2021; 25:19-24. [PMID: 34643354 PMCID: PMC8603851 DOI: 10.34763/jmotherandchild.20212501.d-21-00007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 04/22/2021] [Indexed: 11/22/2022]
Abstract
Background Large and giant congenital melanocytic nevi (CMN), benign naevomelanocytic proliferations derived from neural crests, with a projected adult size (PAS) ≥ 20 cm, are connected to a high risk of melanoma and neurocutaneous melanosis. Among several factors, genetic alterations seem to be involved in tumorigenesis. The aim of the present study was to analyse the mutation status of NRAS and BRAF genes in resection specimens from large or giant CMN in a group of Polish patients. Material and methods The formalin-fixed, paraffin-embedded resection specimens from 18 patients, fixed in the years of 2006 to 2017, were included in the study. The regions containing the highest load of melanocytes were macrodissected prior to DNA isolation. The NRAS and BRAF mutation status was evaluated using qPCR. Results We detected activating mutations in NRAS gene (codons: 12 and 61) in 7 out of the 18 (38.9%) patients. No BRAF mutations were found. Conclusion Our study, the first molecular analysis of large/giant CMN in Polish patients, supports the hypothesis that NRAS mutation in codon 61 are frequent, recurrent mutations in large/giant CMN. Moreover, we show, for the first time, that NRAS mutations in codon 12 (p.Gly12Asp) can be also detected in giant CMN. The exact role of these genetic alterations in CMN formation remains to be elucidated.
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Affiliation(s)
| | - Orest Szczygielski
- Clinic of Surgery of Children and Adolescents, Kasprzaka 17a, PL 01-211, Warsaw, Poland
| | - Katarzyna Seliga
- Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Translational and Molecular Oncology Department, W. K. Roentgena 5, PL 02-781, Warsaw Poland
| | - Andrzej Tysarowski
- Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Translational and Molecular Oncology Department, W. K. Roentgena 5, PL 02-781, Warsaw Poland
| | - Jerzy Bal
- Institute of Mother and Child, Medical Genetics Department, Kasprzaka 17a, PL 01-211, Warsaw, Poland
| | - Elżbieta Michalak
- Institute of Mother and Child, Department of Pathology, Kasprzaka 17a, PL 01-211, Warsaw, Poland
| | | | - Ewa Sawicka
- Clinic of Surgery of Children and Adolescents, Kasprzaka 17a, PL 01-211, Warsaw, Poland
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13
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Zeng J, Weng J, Zhang Y, Xia F, Cui Q, Xu X. Conformational Features of Ras: Key Hydrogen-Bonding Interactions of Gln61 in the Intermediate State during GTP Hydrolysis. J Phys Chem B 2021; 125:8805-8813. [PMID: 34324329 DOI: 10.1021/acs.jpcb.1c04679] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The Ras protein is one of the most important drug targets for battling cancers. To effectively design novel drugs of Ras, we characterize here its conformational ensembles for the hydrolysis intermediate state RasGDP·Pi and the product state RasGDP by extensive replica-exchange molecular dynamics simulations. Several substates for RasGDP·Pi have been identified, while structural analyses have revealed an unrecognized hydrogen-bonding network that stabilizes the hydrolysis intermediate state. More interestingly, Gln61, which is involved in numerous oncogenic mutations, was found to be engaged in this hydrogen-bonding network, adopting a specific conformation that always points to Pi in contrast to that in the RasGTP state. The simulations also reveal that RasGDP has more than one substate, suggesting a conformational selection mechanism for the interaction between Ras and the guanine nucleotide exchange factors (GEFs). These findings offer new opportunities for the drug design of Ras by stabilizing the hydrolysis intermediate or disrupting its interaction with the GEFs.
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Affiliation(s)
- Juan Zeng
- School of Biomedical Engineering, Guangdong Medical University, Dongguan 523808, China
| | - Jingwei Weng
- Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, MOE Key Laboratory of Computational Physical Sciences, Departments of Chemistry, Fudan University, Shanghai 200433, China
| | - Yuwei Zhang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Fei Xia
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China.,Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
| | - Qiang Cui
- Departments of Chemistry, Physics and Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Xin Xu
- Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, MOE Key Laboratory of Computational Physical Sciences, Departments of Chemistry, Fudan University, Shanghai 200433, China
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14
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The RAS GTPase RIT1 compromises mitotic fidelity through spindle assembly checkpoint suppression. Curr Biol 2021; 31:3915-3924.e9. [PMID: 34237269 DOI: 10.1016/j.cub.2021.06.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 05/14/2021] [Accepted: 06/10/2021] [Indexed: 12/11/2022]
Abstract
The spindle assembly checkpoint (SAC) functions as a sensor of unattached kinetochores that delays mitotic progression into anaphase until proper chromosome segregation is guaranteed.1,2 Disruptions to this safety mechanism lead to genomic instability and aneuploidy, which serve as the genetic cause of embryonic demise, congenital birth defects, intellectual disability, and cancer.3,4 However, despite the understanding of the fundamental mechanisms that control the SAC, it remains unknown how signaling pathways directly interact with and regulate the mitotic checkpoint activity. In response to extracellular stimuli, a diverse network of signaling pathways involved in cell growth, survival, and differentiation are activated, and this process is prominently regulated by the Ras family of small guanosine triphosphatases (GTPases).5 Here we show that RIT1, a Ras-related GTPase that regulates cell survival and stress response,6 is essential for timely progression through mitosis and proper chromosome segregation. RIT1 dissociates from the plasma membrane (PM) during mitosis and interacts directly with SAC proteins MAD2 and p31comet in a process that is regulated by cyclin-dependent kinase 1 (CDK1) activity. Furthermore, pathogenic levels of RIT1 silence the SAC and accelerate transit through mitosis by sequestering MAD2 from the mitotic checkpoint complex (MCC). Moreover, SAC suppression by pathogenic RIT1 promotes chromosome segregation errors and aneuploidy. Our results highlight a unique function of RIT1 compared to other Ras GTPases and elucidate a direct link between a signaling pathway and the SAC through a novel regulatory mechanism.
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15
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Cleary JM, Wang V, Heist RS, Kopetz ES, Mitchell EP, Zwiebel JA, Kapner KS, Chen HX, Li S, Gray RJ, McShane LM, Rubinstein LV, Patton DR, Meric-Bernstam F, Dillmon MS, Williams PM, Hamilton SR, Conley BA, Aguirre AJ, O'Dwyer PJ, Harris LN, Arteaga CL, Chen AP, Flaherty KT. Differential Outcomes in Codon 12/13 and Codon 61 NRAS-Mutated Cancers in the Phase II NCI-MATCH Trial of Binimetinib in Patients with NRAS-Mutated Tumors. Clin Cancer Res 2021; 27:2996-3004. [PMID: 33637626 PMCID: PMC8542423 DOI: 10.1158/1078-0432.ccr-21-0066] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 01/11/2021] [Accepted: 02/18/2021] [Indexed: 01/02/2023]
Abstract
PURPOSE Preclinical and clinical data suggest that downstream inhibition with an MEK inhibitor, such as binimetinib, might be efficacious for NRAS-mutated cancers. PATIENTS AND METHODS Patients enrolled in the NCI-MATCH trial master protocol underwent tumor biopsy and molecular profiling by targeted next-generation sequencing. Patients with NRAS-mutated tumors, except melanoma, were enrolled in subprotocol Z1A, a single-arm study evaluating binimetinib 45 mg twice daily. The primary endpoint was objective response rate (ORR). Secondary endpoints included progression-free survival (PFS) and overall survival (OS). A post hoc analysis examined the association of NRAS mutation type with outcome. RESULTS In total, 47 eligible patients with a refractory solid tumor harboring a codon 12, 13, or 61 NRAS mutation were treated. Observed toxicity was moderate, and 30% of patients discontinued treatment because of binimetinib-associated toxicity. The ORR was 2.1% (1/47 patients). A patient with malignant ameloblastoma harboring a codon 61 NRAS mutation achieved a durable partial response (PR). A patient with NRAS codon 61-mutated colorectal cancer had an unconfirmed PR, and two other patients with NRAS codon 61-mutated colorectal had stable disease for at least 12 months. In an exploratory analysis, patients with colorectal cancer bearing a NRAS codon 61 mutation (n = 8) had a significantly longer OS (P = 0.03) and PFS (P = 0.007) than those with codon 12 or 13 mutations (n = 16). CONCLUSIONS Single-agent binimetinib did not show promising efficacy in NRAS-mutated cancers. The observation of increased OS and PFS in patients with codon 61 NRAS-mutated colorectal cancer merits further investigation.
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Affiliation(s)
- James M Cleary
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
| | | | - Rebecca S Heist
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, Massachusetts
| | - E Scott Kopetz
- University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Edith P Mitchell
- Thomas Jefferson University Hospital, Philadelphia, Pennsylvania
| | - James A Zwiebel
- Investigational Drug Branch, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - Kevin S Kapner
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Helen X Chen
- Cancer Therapy Evaluation Program, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - Shuli Li
- Dana-Farber Cancer Institute, Boston, Massachusetts
| | | | - Lisa M McShane
- Biometric Research Program, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - Larry V Rubinstein
- Biometric Research Program, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - David R Patton
- Center for Biomedical Informatics and Information Technology, NCI, Bethesda, Maryland
| | - Funda Meric-Bernstam
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, Massachusetts
| | | | - P Mickey Williams
- Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | | | - Barbara A Conley
- Cancer Diagnosis Program, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - Andrew J Aguirre
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | | | - Lyndsay N Harris
- Cancer Diagnosis Program, Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | | | - Alice P Chen
- Division of Cancer Treatment and Diagnosis, NCI, Bethesda, Maryland
| | - Keith T Flaherty
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, Massachusetts
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16
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Antiparasitic dibenzalacetone inhibits the GTPase activity of Rab6 protein of Leishmania donovani (LdRab6), a potential target for its antileishmanial effect. Parasitol Res 2020; 119:2991-3003. [PMID: 32748038 DOI: 10.1007/s00436-020-06810-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/08/2020] [Indexed: 10/23/2022]
Abstract
Visceral leishmaniasis (VL, also known as kala-azar) is a vector borne disease caused by obligate intracellular protozoan parasite Leishmania donovani. To overcome the limitations of currently available drugs for VL, molecular target-based study is a promising tool to develop new drugs to treat this neglected tropical disease. One such target we recently identified from L. donovani (Ld) genome (WGS, clinical Indian isolate; BHU 1220, AVPQ01000001) is a small GTP-binding protein, Rab6 protein. We now report a specific inhibitor of the GTPase activity of Rab6 protein of L. donovani (LdRab6) without restricting host enzyme activity. First, to understand the nature of LdRab6 protein, we generated recombinant LdRab6 mutant proteins (rLdRab6) by systematically introducing deletion (two cysteine residues at C-terminal) and mutations [single amino acid substitutions in the conserved region of GTP (Q84L)/GDP(T38N) coding sequence]. The GTPase activity of rLdRab6:GTP and rLdRab6:GDP locked mutant proteins showed ~ 8-fold and ~ 1.5-fold decreases in enzyme activity, respectively, compared to the wild type enzyme activity. The mutant protein rLdRab6:ΔC inhibited the GTPase activity. Sequence alignment analysis of Rab6 protein of L. donovani with Homo sapiens showed identical amino acids in the G conserved region (GTP/GDP-binding sites) but it differed in the C-terminal region. We then evaluated the inhibitory activity of trans-dibenzalacetone (DBA, a synthetic analog of curcumin with strong antileishmanial activity reported earlier by us) in the GTPase activity of LdRab6 protein. Comparative molecular docking analysis of DBA and specific inhibitors of Rab proteins (Lovastatin, BFA, Zoledronate, and NE10790) indicated that DBA had optimum binding affinity with LdRab6 protein. This was further confirmed by the GTPase activity of DBA-treated LdRab6 which showed a basal GTP level significantly lower than that of the wild-type rLdRab6. The results confirm that DBA inhibits the GTPase activity of LdRab6 protein from L. donovani (LdRab6), a potential target for its antileishmanial effect.
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17
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de Martín Garrido N, Aylett CHS. Nutrient Signaling and Lysosome Positioning Crosstalk Through a Multifunctional Protein, Folliculin. Front Cell Dev Biol 2020; 8:108. [PMID: 32195250 PMCID: PMC7063858 DOI: 10.3389/fcell.2020.00108] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 02/10/2020] [Indexed: 12/16/2022] Open
Abstract
FLCN was identified as the gene responsible for Birt-Hogg-Dubé (BHD) syndrome, a hereditary syndrome associated with the appearance of familiar renal oncocytomas. Most mutations affecting FLCN result in the truncation of the protein, and therefore loss of its associated functions, as typical for a tumor suppressor. FLCN encodes the protein folliculin (FLCN), which is involved in numerous biological processes; mutations affecting this protein thus lead to different phenotypes depending on the cellular context. FLCN forms complexes with two large interacting proteins, FNIP1 and FNIP2. Structural studies have shown that both FLCN and FNIPs contain longin and differentially expressed in normal versus neoplastic cells (DENN) domains, typically involved in the regulation of small GTPases. Accordingly, functional studies show that FLCN regulates both the Rag and the Rab GTPases depending on nutrient availability, which are respectively involved in the mTORC1 pathway and lysosomal positioning. Although recent structural studies shed light on the precise mechanism by which FLCN regulates the Rag GTPases, which in turn regulate mTORC1, how FLCN regulates membrane trafficking through the Rab GTPases or the significance of the intriguing FLCN-FNIP-AMPK complex formation are questions that still remain unanswered. We discuss the recent progress in our understanding of FLCN regulation of both growth signaling and lysosomal positioning, as well as future approaches to establish detailed mechanisms to explain the disparate phenotypes caused by the loss of FLCN function and the development of BHD-associated and other tumors.
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Affiliation(s)
| | - Christopher H. S. Aylett
- Section for Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, London, United Kingdom
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18
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Calixto AR, Moreira C, Pabis A, Kötting C, Gerwert K, Rudack T, Kamerlin SCL. GTP Hydrolysis Without an Active Site Base: A Unifying Mechanism for Ras and Related GTPases. J Am Chem Soc 2019; 141:10684-10701. [PMID: 31199130 DOI: 10.1021/jacs.9b03193] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
GTP hydrolysis is a biologically crucial reaction, being involved in regulating almost all cellular processes. As a result, the enzymes that catalyze this reaction are among the most important drug targets. Despite their vital importance and decades of substantial research effort, the fundamental mechanism of enzyme-catalyzed GTP hydrolysis by GTPases remains highly controversial. Specifically, how do these regulatory proteins hydrolyze GTP without an obvious general base in the active site to activate the water molecule for nucleophilic attack? To answer this question, we perform empirical valence bond simulations of GTPase-catalyzed GTP hydrolysis, comparing solvent- and substrate-assisted pathways in three distinct GTPases, Ras, Rab, and the Gαi subunit of a heterotrimeric G-protein, both in the presence and in the absence of the corresponding GTPase activating proteins. Our results demonstrate that a general base is not needed in the active site, as the preferred mechanism for GTP hydrolysis is a conserved solvent-assisted pathway. This pathway involves the rate-limiting nucleophilic attack of a water molecule, leading to a short-lived intermediate that tautomerizes to form H2PO4- and GDP as the final products. Our fundamental biochemical insight into the enzymatic regulation of GTP hydrolysis not only resolves a decades-old mechanistic controversy but also has high relevance for drug discovery efforts. That is, revisiting the role of oncogenic mutants with respect to our mechanistic findings would pave the way for a new starting point to discover drugs for (so far) "undruggable" GTPases like Ras.
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Affiliation(s)
- Ana R Calixto
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
| | - Cátia Moreira
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
| | - Anna Pabis
- Department of Cell and Molecular Biology , Uppsala University , BMC Box 596, S-751 24 , Uppsala , Sweden
| | - Carsten Kötting
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Klaus Gerwert
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Till Rudack
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Shina C L Kamerlin
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
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19
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Gupta AK, Wang X, Pagba CV, Prakash P, Sarkar-Banerjee S, Putkey J, Gorfe AA. Multi-target, ensemble-based virtual screening yields novel allosteric KRAS inhibitors at high success rate. Chem Biol Drug Des 2019; 94:1441-1456. [PMID: 30903639 DOI: 10.1111/cbdd.13519] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 02/01/2019] [Accepted: 03/03/2019] [Indexed: 01/11/2023]
Abstract
RAS mutations account for >15% of all human tumors, and of these ~85% are due to mutations in a particular RAS gene: KRAS. Recent studies revealed that KRAS harbors four druggable allosteric sites. Here, we have (a) used molecular simulations to generate ensembles of wild type and four major oncogenic KRAS mutants (G12V, G12D, G13D, and Q61H); (b) characterized the druggability of each allosteric pocket in each protein; (c) conducted extensive ensemble-based virtual screening using pocket-tailored ligand libraries; (d) prioritized hits through hierarchical postdocking analysis; and (e) validated predicted hits with NMR. Of the 785 diverse potential hits identified by our in silico analysis, we tested 90 for their ability to bind KRAS using NMR and found that nine cause backbone amide chemical shift perturbations of residues near the functionally responsive switch loops, suggesting potential binding. We conducted detailed biophysical analyses on a novel indole-based compound to demonstrate the potential of our workflow to yield lead compounds. We believe the detailed information documented in this work regarding the druggability profile of each allosteric site and the chemical fingerprints of compounds that target them will serve as vital resources for future structure-based drug design efforts against KRAS, a high-value target for cancer therapy.
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Affiliation(s)
- Amit K Gupta
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Xu Wang
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Cynthia V Pagba
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Priyanka Prakash
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Suparna Sarkar-Banerjee
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - John Putkey
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Alemayehu A Gorfe
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
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20
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Mo X, Preston S, Zaidi MR. Macroenvironment-gene-microenvironment interactions in ultraviolet radiation-induced melanomagenesis. Adv Cancer Res 2019; 144:1-54. [PMID: 31349897 DOI: 10.1016/bs.acr.2019.03.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cutaneous malignant melanoma is one of the few major cancers that continue to exhibit a positive rate of increase in the developed world. A wealth of epidemiological data has undisputedly implicated ultraviolet radiation (UVR) from sunlight and artificial sources as the major risk factor for melanomagenesis. However, the molecular mechanisms of this cause-and-effect relationship remain murky and understudied. Recent efforts on multiple fronts have brought unprecedented expansion of our knowledge base on this subject and it is now clear that melanoma is caused by a complex interaction between genetic predisposition and environmental exposure, primarily to UVR. Here we provide an overview of the effects of the macroenvironment (UVR) on the skin microenvironment and melanocyte-specific intrinsic (mostly genetic) landscape, which conspire to produce one of the deadliest malignancies.
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Affiliation(s)
- Xuan Mo
- Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Sarah Preston
- Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - M Raza Zaidi
- Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States.
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21
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Kano Y, Gebregiworgis T, Marshall CB, Radulovich N, Poon BPK, St-Germain J, Cook JD, Valencia-Sama I, Grant BMM, Herrera SG, Miao J, Raught B, Irwin MS, Lee JE, Yeh JJ, Zhang ZY, Tsao MS, Ikura M, Ohh M. Tyrosyl phosphorylation of KRAS stalls GTPase cycle via alteration of switch I and II conformation. Nat Commun 2019; 10:224. [PMID: 30644389 PMCID: PMC6333830 DOI: 10.1038/s41467-018-08115-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/17/2018] [Indexed: 12/27/2022] Open
Abstract
Deregulation of the RAS GTPase cycle due to mutations in the three RAS genes is commonly associated with cancer development. Protein tyrosine phosphatase SHP2 promotes RAF-to-MAPK signaling pathway and is an essential factor in RAS-driven oncogenesis. Despite the emergence of SHP2 inhibitors for the treatment of cancers harbouring mutant KRAS, the mechanism underlying SHP2 activation of KRAS signaling remains unclear. Here we report tyrosyl-phosphorylation of endogenous RAS and demonstrate that KRAS phosphorylation via Src on Tyr32 and Tyr64 alters the conformation of switch I and II regions, which stalls multiple steps of the GTPase cycle and impairs binding to effectors. In contrast, SHP2 dephosphorylates KRAS, a process that is required to maintain dynamic canonical KRAS GTPase cycle. Notably, Src- and SHP2-mediated regulation of KRAS activity extends to oncogenic KRAS and the inhibition of SHP2 disrupts the phosphorylation cycle, shifting the equilibrium of the GTPase cycle towards the stalled ‘dark state’. Deregulation of the RAS GTPase cycle due to mutations in RAS genes is commonly associated with cancer development. Here authors use NMR and mass spectrometry to shows that KRAS phosphorylation via Src alters the conformation of switch I and II regions and thereby impacts the GTPase cycle.
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Affiliation(s)
- Yoshihito Kano
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada.,Department of Biochemistry, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Teklab Gebregiworgis
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Christopher B Marshall
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Nikolina Radulovich
- Princess Margaret Cancer Centre, University Health Network and Department of Pathology, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Betty P K Poon
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Jonathan St-Germain
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Jonathan D Cook
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Ivette Valencia-Sama
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada.,Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON, 5G OA4, Canada
| | - Benjamin M M Grant
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Silvia Gabriela Herrera
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jinmin Miao
- Department of Medicinal Chemistry and Molecular Pharmacology, Center for Cancer Research and Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN, 47907, USA
| | - Brian Raught
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Meredith S Irwin
- Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON, 5G OA4, Canada
| | - Jeffrey E Lee
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Jen Jen Yeh
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Surgery, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Zhong-Yin Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Center for Cancer Research and Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN, 47907, USA
| | - Ming-Sound Tsao
- Princess Margaret Cancer Centre, University Health Network and Department of Pathology, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Mitsuhiko Ikura
- Princess Margaret Cancer Centre, University Health Network and Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON, M5G 1L7, Canada
| | - Michael Ohh
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada. .,Department of Biochemistry, University of Toronto, 661 University Avenue, Toronto, ON, M5G 1M1, Canada.
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22
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Novelli ET, First JT, Webb LJ. Quantitative Measurement of Intrinsic GTP Hydrolysis for Carcinogenic Glutamine 61 Mutants in H-Ras. Biochemistry 2018; 57:6356-6366. [PMID: 30339365 DOI: 10.1021/acs.biochem.8b00878] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mutations of human oncoprotein p21H-Ras (hereafter "Ras") at glutamine 61 are known to slow the rate of guanosine triphosphate (GTP) hydrolysis and transform healthy cells into malignant cells. It has been hypothesized that this glutamine plays a role in the intrinsic mechanism of GTP hydrolysis by interacting with an active site water molecule that stabilizes the formation of the charged transition state at the γ-phosphate during hydrolysis. However, there is no comprehensive data set of the effects of mutations to Q61 on the protein's intrinsic catalytic rate, structure, or interactions with water at the active site. Here, we present the first comprehensive and quantitative set of initial rates of intrinsic hydrolysis for all stable variants of RasQ61X. We further conducted enhanced molecular dynamics (MD) simulations of each construct to determine the solvent accessible surface area (SASA) of the side chain at position 61 and compared these results to previously measured changes in electric fields caused by RasQ61X mutations. For polar and negatively charged residues, we found that the rates are normally distributed about an optimal electrostatic contribution, close to that of the native Q61 residue, and the rates are strongly correlated to the number of waters in the active site. Together, these results support a mechanism of GTP hydrolysis in which Q61 stabilizes a transient hydronium ion, which then stabilizes the transition state while the γ-phosphate is undergoing nucleophilic attack by a second, catalytically active water molecule. We discuss the implications of such a mechanism on future strategies for combating Ras-based cancers.
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Affiliation(s)
- Elisa T Novelli
- Department of Chemistry, Texas Materials Institute, Institute for Cell and Molecular Biology , The University of Texas at Austin , 105 E 24th Street STOP A5300 , Austin , Texas 78712-1224 , United States
| | - Jeremy T First
- Department of Chemistry, Texas Materials Institute, Institute for Cell and Molecular Biology , The University of Texas at Austin , 105 E 24th Street STOP A5300 , Austin , Texas 78712-1224 , United States
| | - Lauren J Webb
- Department of Chemistry, Texas Materials Institute, Institute for Cell and Molecular Biology , The University of Texas at Austin , 105 E 24th Street STOP A5300 , Austin , Texas 78712-1224 , United States
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23
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Tichauer RH, Favre G, Cabantous S, Landa G, Hemeryck A, Brut M. Water Distribution within Wild-Type NRas Protein and Q61 Mutants during Unrestrained QM/MM Dynamics. Biophys J 2018; 115:1417-1430. [PMID: 30224050 DOI: 10.1016/j.bpj.2018.07.042] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 07/25/2018] [Accepted: 07/26/2018] [Indexed: 10/28/2022] Open
Abstract
Point mutations in p21ras are associated with ∼30% of human tumors by disrupting its GTP hydrolysis cycle, which is critical to its molecular switch function in cellular signaling pathways. In this work, we investigate the impact of Gln 61 substitutions in the structure of the p21N-ras active site and particularly focus on water reorganization around GTP, which appears to be crucial to evaluate favorable and unfavorable hydration sites for hydrolysis. The NRas-GTP complex is analyzed using a hybrid quantum mechanics/molecular mechanics approach, treating for the first time to our knowledge transient water molecules at the ab initio level and leading to results that account for the electrostatic coupling between the protein complex and the solvent. We show that for the wild-type protein, water molecules are found around the GTP γ-phosphate group, forming an arch extended from residues 12 to 35. Two density peaks are observed, supporting previous results that suggest the presence of two water molecules in the active site, one in the vicinity of residue 35 and a second one stabilized by hydrogen bonds formed with nitrogen backbone atoms of residues 12 and 60. The structural changes observed in NRas Gln 61 mutants result in the drastic delocalization of water molecules that we discuss. In mutants Q61H and Q61K, for which water distribution is overlocalized next to residue 60, the second density peak supports the hypothesis of a second water molecule. We also conclude that Gly 60 indirectly participates in GTP hydrolysis by correctly positioning transient water molecules in the protein complex and that Gln 61 has an indirect steric effect in stabilizing the preorganized catalytic site.
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Affiliation(s)
- Ruth H Tichauer
- LAAS-CNRS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Gilles Favre
- Cancer Research Center of Toulouse, INSERM U1037, Toulouse, France; Université de Toulouse, Toulouse, France
| | - Stéphanie Cabantous
- Cancer Research Center of Toulouse, INSERM U1037, Toulouse, France; Université de Toulouse, Toulouse, France
| | - Georges Landa
- LAAS-CNRS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Anne Hemeryck
- LAAS-CNRS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Marie Brut
- LAAS-CNRS, Université de Toulouse, CNRS, UPS, Toulouse, France.
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24
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Shen K, Choe A, Sabatini DM. Intersubunit Crosstalk in the Rag GTPase Heterodimer Enables mTORC1 to Respond Rapidly to Amino Acid Availability. Mol Cell 2017; 68:552-565.e8. [PMID: 29056322 PMCID: PMC5674802 DOI: 10.1016/j.molcel.2017.09.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 08/14/2017] [Accepted: 09/19/2017] [Indexed: 01/03/2023]
Abstract
mTOR complex I (mTORC1) is a central growth regulator that senses amino acids through a pathway that converges on the Rag GTPases, an obligate heterodimer of two related GTPases. Despite their central role in amino acid sensing, it is unknown why the Rag GTPases are heterodimeric and whether their subunits communicate with each other. Here, we find that the binding of guanosine triphosphate (GTP) to one subunit inhibits the binding and induces the hydrolysis of GTP by the other. This intersubunit communication pushes the Rag GTPases into either of two stable configurations, which represent active "on" or "off" states that interconvert via transient intermediates. Subunit coupling confers on the mTORC1 pathway its capacity to respond rapidly to the amino acid level. Thus, the dynamic response of mTORC1 requires intersubunit communication by the Rag GTPases, providing a rationale for why they exist as a dimer and revealing a distinct mode of control for a GTP-binding protein.
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Affiliation(s)
- Kuang Shen
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Broad Institute of Harvard and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, MA 02142, USA
| | - Abigail Choe
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - David M Sabatini
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Broad Institute of Harvard and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, MA 02142, USA.
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25
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Kotyada C, Maulik A, Srivastava A, Singh M. Mechanistic Insights into the Differential Catalysis by RheB and Its Mutants: Y35A and Y35A-D65A. ACS OMEGA 2017; 2:6691-6702. [PMID: 29750207 PMCID: PMC5937686 DOI: 10.1021/acsomega.7b01025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 09/28/2017] [Indexed: 06/08/2023]
Abstract
RheB GTPase is a Ras-related molecular switch, which regulates the mTOR signaling pathway by cycling between the active [guanosine triphosphate (GTP)] state and inactive [guanine diphosphate (GDP)] state. Impairment of GTPase activity because of mutations in several small GTPases is known to be associated with several cancers. The conventional GTPase mechanism such as in H-Ras requires a conserved glutamine (Q64) in the switch-II region of RheB to align the catalytic water molecule for efficient GTP hydrolysis. The conformation of this conserved glutamine is different in RheB, resulting in an altered conformation of the entire switch-II region. Studies on the atypical switch-II conformation in RheB revealed a distinct, noncanonical mode of GTP hydrolysis. An RheB mutant Y35A was previously shown to exclusively enhance the intrinsic GTPase activity of RheB, whereas the Y35A-D65A double mutant was shown to reduce the elevated GTPase activity. Here, we have used all-atom molecular dynamics (MD) simulations for comprehensive understanding of the conformational dynamics associated with the fast (Y35A) and slow (Y35A-D65A) hydrolyzing mutants of RheB. Using a combination of starting models from PDB structures and in-silico generated mutant structures, we discuss the observed conformational deviations in wild type (WT) versus mutants. Our results show that a number of interactions of RheB with phosphates of GTP as well as Mg2+ are destabilized in Y35A mutant in the switch-I region. We report distinct water dynamics at the active site of WT and mutants. Furthermore, principal component analysis showed significant differences in the conformational space sampled by the WT and mutants. Our observations provide improved understanding of the noncanonical GTP hydrolysis mechanism adopted by RheB and its modulation by Y35A and Y35A-D65A mutants.
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Affiliation(s)
- Chaithanya Kotyada
- Molecular
Biophysics Unit and NMR Research Centre, Indian Institute of
Science, Bengaluru 560012, India
| | - Aditi Maulik
- Molecular
Biophysics Unit and NMR Research Centre, Indian Institute of
Science, Bengaluru 560012, India
| | - Anand Srivastava
- Molecular
Biophysics Unit and NMR Research Centre, Indian Institute of
Science, Bengaluru 560012, India
| | - Mahavir Singh
- Molecular
Biophysics Unit and NMR Research Centre, Indian Institute of
Science, Bengaluru 560012, India
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26
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Mishra AK, Lambright DG. Invited review: Small GTPases and their GAPs. Biopolymers 2016; 105:431-48. [PMID: 26972107 PMCID: PMC5439442 DOI: 10.1002/bip.22833] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 02/16/2016] [Accepted: 03/10/2016] [Indexed: 12/11/2022]
Abstract
Widespread utilization of small GTPases as major regulatory hubs in many different biological systems derives from a conserved conformational switch mechanism that facilitates cycling between GTP-bound active and GDP-bound inactive states under control of guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), which accelerate slow intrinsic rates of activation by nucleotide exchange and deactivation by GTP hydrolysis, respectively. Here we review developments leading to current understanding of intrinsic and GAP catalyzed GTP hydrolytic reactions in small GTPases from structural, molecular and chemical mechanistic perspectives. Despite the apparent simplicity of the GTPase cycle, the structural bases underlying the hallmark hydrolytic reaction and catalytic acceleration by GAPs are considerably more diverse than originally anticipated. Even the most fundamental aspects of the reaction mechanism have been challenging to decipher. Through a combination of experimental and in silico approaches, the outlines of a consensus view have begun to emerge for the best studied paradigms. Nevertheless, recent observations indicate that there is still much to be learned. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 431-448, 2016.
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Affiliation(s)
- Ashwini K Mishra
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605
| | - David G Lambright
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605
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27
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Fang Z, Marshall CB, Yin JC, Mazhab-Jafari MT, Gasmi-Seabrook GMC, Smith MJ, Nishikawa T, Xu Y, Neel BG, Ikura M. Biochemical Classification of Disease-associated Mutants of RAS-like Protein Expressed in Many Tissues (RIT1). J Biol Chem 2016; 291:15641-52. [PMID: 27226556 DOI: 10.1074/jbc.m116.714196] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Indexed: 01/09/2023] Open
Abstract
RAS-like protein expressed in many tissues 1 (RIT1) is a disease-associated RAS subfamily small guanosine triphosphatase (GTPase). Recent studies revealed that germ-line and somatic RIT1 mutations can cause Noonan syndrome (NS), and drive proliferation of lung adenocarcinomas, respectively, akin to RAS mutations in these diseases. However, the locations of these RIT1 mutations differ significantly from those found in RAS, and do not affect the three mutational "hot spots" of RAS. Moreover, few studies have characterized the GTPase cycle of RIT1 and its disease-associated mutants. Here we developed a real-time NMR-based GTPase assay for RIT1 and investigated the effect of disease-associated mutations on GTPase cycle. RIT1 exhibits an intrinsic GTP hydrolysis rate similar to that of H-RAS, but its intrinsic nucleotide exchange rate is ∼4-fold faster, likely as a result of divergent residues near the nucleotide binding site. All of the disease-associated mutations investigated increased the GTP-loaded, activated state of RIT1 in vitro, but they could be classified into two groups with different intrinsic GTPase properties. The S35T, A57G, and Y89H mutants exhibited more rapid nucleotide exchange, whereas F82V and T83P impaired GTP hydrolysis. A RAS-binding domain pulldown assay indicated that RIT1 A57G and Y89H were highly activated in HEK293T cells, whereas T83P and F82V exhibited more modest activation. All five mutations are associated with NS, whereas two (A57G and F82V) have also been identified in urinary tract cancers and myeloid malignancies. Characterization of the effects on the GTPase cycle of RIT1 disease-associated mutations should enable better understanding of their role in disease processes.
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Affiliation(s)
- Zhenhao Fang
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Christopher B Marshall
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Jiani C Yin
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Mohammad T Mazhab-Jafari
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Geneviève M C Gasmi-Seabrook
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Matthew J Smith
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Tadateru Nishikawa
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Yang Xu
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Benjamin G Neel
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
| | - Mitsuhiko Ikura
- From the Department of Medical Biophysics, Campbell Family Institute for Cancer Research, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario M5G 2M9, Canada
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28
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Molecular Mechanism for Conformational Dynamics of Ras·GTP Elucidated from In-Situ Structural Transition in Crystal. Sci Rep 2016; 6:25931. [PMID: 27180801 PMCID: PMC4867591 DOI: 10.1038/srep25931] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/25/2016] [Indexed: 02/07/2023] Open
Abstract
Ras•GTP adopts two interconverting conformational states, state 1 and state 2, corresponding to inactive and active forms, respectively. However, analysis of the mechanism for state transition was hampered by the lack of the structural information on wild-type Ras state 1 despite its fundamental nature conserved in the Ras superfamily. Here we solve two new crystal structures of wild-type H-Ras, corresponding to state 1 and state 2. The state 2 structure seems to represent an intermediate of state transition and, intriguingly, the state 1 crystal is successfully derived from this state 2 crystal by regulating the surrounding humidity. Structural comparison enables us to infer the molecular mechanism for state transition, during which a wide range of hydrogen-bonding networks across Switch I, Switch II and the α3-helix interdependently undergo gross rearrangements, where fluctuation of Tyr32, translocation of Gln61, loss of the functional water molecules and positional shift of GTP play major roles. The NMR-based hydrogen/deuterium exchange experiments also support this transition mechanism. Moreover, the unveiled structural features together with the results of the biochemical study provide a new insight into the physiological role of state 1 as a stable pool of Ras•GTP in the GDP/GTP cycle of Ras.
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29
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Jenkins RW, Sullivan RJ. NRAS mutant melanoma: an overview for the clinician for melanoma management. Melanoma Manag 2016; 3:47-59. [PMID: 30190872 PMCID: PMC6097550 DOI: 10.2217/mmt.15.40] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/06/2015] [Indexed: 12/19/2022] Open
Abstract
Melanoma is the deadliest form of skin cancer and the incidence continues to rise in the United States and worldwide. Activating mutations in RAS oncogenes are found in roughly a third of all human cancers. Mutations in NRAS occur in approximately a fifth of cutaneous melanomas and are associated with aggressive clinical behavior. Cells harboring oncogenic NRAS mutations exhibit activation of multiple signaling cascades, including PI3K/Akt, MEK-ERK and RAL, which collectively stimulate cancer growth. While strategies to target N-Ras itself have proven ineffective, targeting one or more N-Ras effector pathways has shown promise in preclinical models. Despite promising preclinical data, current therapies for NRAS mutant melanoma remain limited. Immune checkpoint inhibitors and targeted therapies for BRAF mutant melanoma are transforming the treatment of metastatic melanoma, but the ideal treatment for NRAS mutant melanoma remains unknown. Improved understanding of NRAS mutant melanoma and relevant N-Ras effector signaling modules will be essential to develop new treatment strategies.
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Affiliation(s)
| | - Ryan J Sullivan
- Massachusetts General Hospital Cancer Center, Boston, MA, USA
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30
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Dias-Santagata D, Su Y, Hoang MP. Immunohistochemical Detection of NRASQ61R Mutation in Diverse Tumor Types. Am J Clin Pathol 2016; 145:29-34. [PMID: 26712868 DOI: 10.1093/ajcp/aqv015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVES Testing for NRAS mutation at codon Q61 is of therapeutic, prognostic, and diagnostic importance for metastatic melanoma, thyroid carcinoma, and colorectal carcinoma. Immunohistochemistry for NRASQ61R, the most common NRAS mutation, offers several practical advantages over current molecular diagnostic techniques. METHODS We investigated the sensitivity and specificity of NRASQ61R in a series of 149 tumors with known NRAS genotype (72 malignant melanomas, 13 melanocytic nevi, 28 thyroid carcinomas, 25 gastrointestinal carcinomas, and 11 other malignancies). RESULTS Thirty-five cases harbored the NRASQ61R mutation (19 malignant melanomas, one melanocytic nevus, 10 thyroid carcinomas, two gastrointestinal carcinomas, and three other malignancies). In this series, the concordance rate between immunohistochemistry and mutational analyses was 100%. The sensitivity and specificity were 100% and 100%, respectively. However, lower staining intensity was observed for thyroid carcinomas in comparison to melanomas and other tumors. CONCLUSIONS Our studies confirmed that immunohistochemistry provides excellent sensitivity and specificity for detecting the NRASQ61R mutation in a variety of tumor types in a clinical setting.
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Affiliation(s)
- Dora Dias-Santagata
- From the Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA
| | - Yuhua Su
- From the Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA
| | - Mai P Hoang
- From the Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
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31
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MacKay JL, Kumar S. Simultaneous and independent tuning of RhoA and Rac1 activity with orthogonally inducible promoters. Integr Biol (Camb) 2015; 6:885-94. [PMID: 25044255 DOI: 10.1039/c4ib00099d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The GTPases RhoA and Rac1 are key regulators of cell spreading, adhesion, and migration, and they exert distinct effects on the actin cytoskeleton. While RhoA classically stimulates stress fiber assembly and contraction, Rac1 promotes branched actin polymerization and membrane protrusion. These competing influences are reinforced by antagonistic crosstalk between RhoA and Rac1, which has complicated efforts to identify the specific mechanisms by which each GTPase regulates cell behavior. We therefore wondered whether RhoA and Rac1 are intrinsically coupled or whether they can be manipulated independently. To address this question, we placed constitutively active (CA) RhoA under a doxycycline-inducible promoter and CA Rac1 under an orthogonal cumate-inducible promoter, and we stably introduced both constructs into glioblastoma cells. We found that doxycycline addition increased RhoA activity without altering Rac1, and similarly cumate addition increased Rac1 activity without altering RhoA. Furthermore, co-expression of both mutants enabled high activation of RhoA and Rac1 simultaneously. When cells were cultured on collagen hydrogels, RhoA activation prevented cell spreading and motility, whereas Rac1 activation stimulated migration and dynamic cell protrusions. Interestingly, high activation of both GTPases induced a third phenotype, in which cells migrated at intermediate speeds similar to control cells but also aggregated into large, contractile clusters. In addition, we demonstrate dynamic and reversible switching between high RhoA and high Rac1 phenotypes. Overall, this approach represents a unique way to access different combinations of RhoA and Rac1 activity levels in a single cell and may serve as a valuable tool for multiplexed dissection and control of mechanobiological signals.
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Affiliation(s)
- Joanna L MacKay
- Department of Chemical and Biomolecular Engineering, University of California-Berkeley, Berkeley, California 94720, USA
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32
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Carvalho ATP, Szeler K, Vavitsas K, Åqvist J, Kamerlin SCL. Modeling the mechanisms of biological GTP hydrolysis. Arch Biochem Biophys 2015; 582:80-90. [PMID: 25731854 DOI: 10.1016/j.abb.2015.02.027] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 02/19/2015] [Accepted: 02/21/2015] [Indexed: 01/11/2023]
Abstract
Enzymes that hydrolyze GTP are currently in the spotlight, due to their molecular switch mechanism that controls many cellular processes. One of the best-known classes of these enzymes are small GTPases such as members of the Ras superfamily, which catalyze the hydrolysis of the γ-phosphate bond in GTP. In addition, the availability of an increasing number of crystal structures of translational GTPases such as EF-Tu and EF-G have made it possible to probe the molecular details of GTP hydrolysis on the ribosome. However, despite a wealth of biochemical, structural and computational data, the way in which GTP hydrolysis is activated and regulated is still a controversial topic and well-designed simulations can play an important role in resolving and rationalizing the experimental data. In this review, we discuss the contributions of computational biology to our understanding of GTP hydrolysis on the ribosome and in small GTPases.
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Affiliation(s)
- Alexandra T P Carvalho
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Klaudia Szeler
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Konstantinos Vavitsas
- Copenhagen Plant Science Centre (CPSC), Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| | - Johan Åqvist
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden
| | - Shina C L Kamerlin
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, SE-751 24 Uppsala, Sweden.
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33
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Burd CE, Liu W, Huynh MV, Waqas MA, Gillahan JE, Clark KS, Fu K, Martin BL, Jeck WR, Souroullas GP, Darr DB, Zedek DC, Miley MJ, Baguley BC, Campbell SL, Sharpless NE. Mutation-specific RAS oncogenicity explains NRAS codon 61 selection in melanoma. Cancer Discov 2014; 4:1418-29. [PMID: 25252692 PMCID: PMC4258185 DOI: 10.1158/2159-8290.cd-14-0729] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
UNLABELLED NRAS mutation at codons 12, 13, or 61 is associated with transformation; yet, in melanoma, such alterations are nearly exclusive to codon 61. Here, we compared the melanoma susceptibility of an NrasQ61R knock-in allele to similarly designed KrasG12D and NrasG12D alleles. With concomitant p16INK4a inactivation, KrasG12D or NrasQ61R expression efficiently promoted melanoma in vivo, whereas NrasG12D did not. In addition, NrasQ61R mutation potently cooperated with Lkb1/Stk11 loss to induce highly metastatic disease. Functional comparisons of NrasQ61R and NrasG12D revealed little difference in the ability of these proteins to engage PI3K or RAF. Instead, NrasQ61R showed enhanced nucleotide binding, decreased intrinsic GTPase activity, and increased stability when compared with NrasG12D. This work identifies a faithful model of human NRAS-mutant melanoma, and suggests that the increased melanomagenecity of NrasQ61R over NrasG12D is due to heightened abundance of the active, GTP-bound form rather than differences in the engagement of downstream effector pathways. SIGNIFICANCE This work explains the curious predominance in human melanoma of mutations of codon 61 of NRAS over other oncogenic NRAS mutations. Using conditional "knock-in" mouse models, we show that physiologic expression of NRASQ61R, but not NRASG12D, drives melanoma formation.
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Affiliation(s)
- Christin E Burd
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio. Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio
| | - Wenjin Liu
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Minh V Huynh
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Meriam A Waqas
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio
| | - James E Gillahan
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio. Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio
| | - Kelly S Clark
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Kailing Fu
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Brit L Martin
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio
| | - William R Jeck
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - George P Souroullas
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - David B Darr
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Daniel C Zedek
- Department of Dermatology, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Michael J Miley
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Bruce C Baguley
- Auckland Cancer Society Research Centre, University of Auckland, Auckland, New Zealand
| | - Sharon L Campbell
- The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina. Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina
| | - Norman E Sharpless
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina. The Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina.
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Mazhab-Jafari MT, Marshall CB, Ho J, Ishiyama N, Stambolic V, Ikura M. Structure-guided mutation of the conserved G3-box glycine in Rheb generates a constitutively activated regulator of mammalian target of rapamycin (mTOR). J Biol Chem 2014; 289:12195-201. [PMID: 24648513 DOI: 10.1074/jbc.c113.543736] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Constitutively activated variants of small GTPases, which provide valuable functional probes of their role in cellular signaling pathways, can often be generated by mutating the canonical catalytic residue (e.g. Ras Q61L) to impair GTP hydrolysis. However, this general approach is ineffective for a substantial fraction of the small GTPase family in which this residue is not conserved (e.g. Rap) or not catalytic (e.g. Rheb). Using a novel engineering approach, we have manipulated nucleotide binding through structure-guided substitutions of an ultraconserved glycine residue in the G3-box motif (DXXG). Substitution of Rheb Gly-63 with alanine impaired both intrinsic and TSC2 GTPase-activating protein (GAP)-mediated GTP hydrolysis by displacing the hydrolytic water molecule, whereas introduction of a bulkier valine side chain selectively blocked GTP binding by steric occlusion of the γ-phosphate. Rheb G63A stimulated phosphorylation of the mTORC1 substrate p70S6 kinase more strongly than wild-type, thus offering a new tool for mammalian target of rapamycin (mTOR) signaling.
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Affiliation(s)
- Mohammad T Mazhab-Jafari
- From the Campbell Family Cancer Research Institute, Princess Margaret Cancer Centre and, Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9, Canada
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Li W, Sharma M, Kaur P. The DrrAB efflux system of Streptomyces peucetius is a multidrug transporter of broad substrate specificity. J Biol Chem 2014; 289:12633-46. [PMID: 24634217 DOI: 10.1074/jbc.m113.536136] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The soil bacterium Streptomyces peucetius produces two widely used anticancer antibiotics, doxorubicin and daunorubicin. Present within the biosynthesis gene cluster in S. peucetius is the drrAB operon, which codes for a dedicated ABC (ATP binding cassette)-type transporter for the export of these two closely related antibiotics. Because of its dedicated nature, the DrrAB system is believed to belong to the category of single-drug transporters. However, whether it also contains specificity for other known substrates of multidrug transporters has never been tested. In this study we demonstrate under both in vivo and in vitro conditions that the DrrAB system can transport not only doxorubicin but is also able to export two most commonly studied MDR substrates, Hoechst 33342 and ethidium bromide. Moreover, we demonstrate that many other substrates (including verapamil, vinblastine, and rifampicin) of the well studied multidrug transporters inhibit DrrAB-mediated Dox transport with high efficiency, indicating that they are also substrates of the DrrAB pump. Kinetic studies show that inhibition of doxorubicin transport by Hoechst 33342 and rifampicin occurs by a competitive mechanism, whereas verapamil inhibits transport by a non-competitive mechanism, thus suggesting the possibility of more than one drug binding site in the DrrAB system. This is the first in-depth study of a drug resistance system from a producer organism, and it shows that a dedicated efflux system like DrrAB contains specificity for multiple drugs. The significance of these findings in evolution of poly-specificity in drug resistance systems is discussed.
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Affiliation(s)
- Wen Li
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
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36
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Miyakawa T, Morikawa R, Takasu M, Sugimori K, Kawaguchi K, Saito H, Nagao H. Analysis of water molecules around GTP in Hras-GTP complex and GDP in Hras-GDP complex by molecular dynamics simulations. Mol Phys 2013. [DOI: 10.1080/00268976.2013.852697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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37
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Tsun ZY, Bar-Peled L, Chantranupong L, Zoncu R, Wang T, Kim C, Spooner E, Sabatini DM. The folliculin tumor suppressor is a GAP for the RagC/D GTPases that signal amino acid levels to mTORC1. Mol Cell 2013; 52:495-505. [PMID: 24095279 DOI: 10.1016/j.molcel.2013.09.016] [Citation(s) in RCA: 406] [Impact Index Per Article: 36.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 09/18/2013] [Accepted: 09/18/2013] [Indexed: 10/26/2022]
Abstract
The mTORC1 kinase is a master growth regulator that senses numerous environmental cues, including amino acids. The Rag GTPases interact with mTORC1 and signal amino acid sufficiency by promoting the translocation of mTORC1 to the lysosomal surface, its site of activation. The Rags are unusual GTPases in that they function as obligate heterodimers, which consist of RagA or B bound to RagC or D. While the loading of RagA/B with GTP initiates amino acid signaling to mTORC1, the role of RagC/D is unknown. Here, we show that RagC/D is a key regulator of the interaction of mTORC1 with the Rag heterodimer and that, unexpectedly, RagC/D must be GDP bound for the interaction to occur. We identify FLCN and its binding partners, FNIP1/2, as Rag-interacting proteins with GAP activity for RagC/D, but not RagA/B. Thus, we reveal a role for RagC/D in mTORC1 activation and a molecular function for the FLCN tumor suppressor.
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Affiliation(s)
- Zhi-Yang Tsun
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Liron Bar-Peled
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Lynne Chantranupong
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Roberto Zoncu
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Tim Wang
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Choah Kim
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Eric Spooner
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA
| | - David M Sabatini
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA.,Koch Institute for Integrative for Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.,Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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38
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Bar-Peled L, Schweitzer LD, Zoncu R, Sabatini DM. Ragulator is a GEF for the rag GTPases that signal amino acid levels to mTORC1. Cell 2012; 150:1196-208. [PMID: 22980980 DOI: 10.1016/j.cell.2012.07.032] [Citation(s) in RCA: 687] [Impact Index Per Article: 57.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 06/01/2012] [Accepted: 07/10/2012] [Indexed: 12/21/2022]
Abstract
The mTOR Complex 1 (mTORC1) pathway regulates cell growth in response to numerous cues, including amino acids, which promote mTORC1 translocation to the lysosomal surface, its site of activation. The heterodimeric RagA/B-RagC/D GTPases, the Ragulator complex that tethers the Rags to the lysosome, and the v-ATPase form a signaling system that is necessary for amino acid sensing by mTORC1. Amino acids stimulate the binding of guanosine triphosphate to RagA and RagB but the factors that regulate Rag nucleotide loading are unknown. Here, we identify HBXIP and C7orf59 as two additional Ragulator components that are required for mTORC1 activation by amino acids. The expanded Ragulator has nucleotide exchange activity toward RagA and RagB and interacts with the Rag heterodimers in an amino acid- and v-ATPase-dependent fashion. Thus, we provide mechanistic insight into how mTORC1 senses amino acids by identifying Ragulator as a guanine nucleotide exchange factor (GEF) for the Rag GTPases.
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Affiliation(s)
- Liron Bar-Peled
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, Nine Cambridge Center, Cambridge, MA 02142, USA
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Mazhab-Jafari MT, Marshall CB, Ishiyama N, Ho J, Di Palma V, Stambolic V, Ikura M. An autoinhibited noncanonical mechanism of GTP hydrolysis by Rheb maintains mTORC1 homeostasis. Structure 2012; 20:1528-39. [PMID: 22819219 DOI: 10.1016/j.str.2012.06.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 06/18/2012] [Accepted: 06/20/2012] [Indexed: 01/28/2023]
Abstract
Rheb, an activator of mammalian target of rapamycin (mTOR), displays low intrinsic GTPase activity favoring the biologically activated, GTP-bound state. We identified a Rheb mutation (Y35A) that increases its intrinsic nucleotide hydrolysis activity ∼10-fold, and solved structures of both its active and inactive forms, revealing an unexpected mechanism of GTP hydrolysis involving Asp65 in switch II and Thr38 in switch I. In the wild-type protein this noncanonical mechanism is markedly inhibited by Tyr35, which constrains the active site conformation, restricting the access of the catalytic Asp65 to the nucleotide-binding pocket. Rheb Y35A mimics the enthalpic and entropic changes associated with GTP hydrolysis elicited by the GTPase-activating protein (GAP) TSC2, and is insensitive to further TSC2 stimulation. Overexpression of Rheb Y35A impaired the regulation of mTORC1 signaling by growth factor availability. We demonstrate that the opposing functions of Tyr35 in the intrinsic and GAP-stimulated GTP catalysis are critical for optimal mTORC1 regulation.
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40
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Stafford AJ, Walker DM, Webb LJ. Electrostatic effects of mutations of Ras glutamine 61 measured using vibrational spectroscopy of a thiocyanate probe. Biochemistry 2012; 51:2757-67. [PMID: 22385209 DOI: 10.1021/bi201225p] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mutations of human oncoprotein p21(Ras) (hereafter Ras) at glutamine 61 are known to slow the rate of guanosine triphosphate (GTP) hydrolysis and transform healthy cells into malignant cells. It has been hypothesized that this glutamine plays a role in the intrinsic mechanism of GTP hydrolysis by interacting with an active site water molecule that electrostatically stabilizes the formation of the charged transition state at the γ-phosphate during hydrolysis. We have tested the interactions between amino acids at this position and water by measuring changes in the electrostatic field experienced by a nitrile probe positioned near Ras Q61 using vibrational Stark effect (VSE) spectroscopy. We mutated this glutamine to every amino acid except cysteine and proline and then incubated these mutants with a Ral guanine nucleotide dissociation stimulator (Ral) containing the I18C mutation that was chemically labeled with a thiocyanate vibrational spectroscopic probe. The formation of the docked Ras Q61X-labeled Ral complex was confirmed by measurement of the dissociation constant of the interaction. We measured the absorption energy of this nitrile to determine any differences in electrostatic environment in the immediate vicinity of the thiocyanate probe between wild type and mutants of Ras. For each Ras Q61X mutant, we correlate the change in electrostatic field at position 61 with the solvent accessible surface area of polar components of the mutant side chain determined from a Boltzmann-weighted ensemble of structures, as well as the residue's hydration potential. These results support the hypothesis that the role of Ras Q61 is to stabilize water in or near the active site during GTP hydrolysis. The substantial effect that nonpolar side chains of Ras Q61X have on the absorption energy of the thiocyanate must be investigated with further experiments.
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Affiliation(s)
- Amy J Stafford
- Department of Chemistry and Biochemistry, Institute for Cell and Molecular Biology, and Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712, United States
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41
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Heo JB, Sung S, Assmann SM. Ca2+-dependent GTPase, extra-large G protein 2 (XLG2), promotes activation of DNA-binding protein related to vernalization 1 (RTV1), leading to activation of floral integrator genes and early flowering in Arabidopsis. J Biol Chem 2012; 287:8242-53. [PMID: 22232549 DOI: 10.1074/jbc.m111.317412] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Heterotrimeric G proteins, consisting of Gα, Gβ, and Gγ subunits, play important roles in plant development and cell signaling. In Arabidopsis, in addition to one prototypical G protein α subunit, GPA1, there are three extra-large G proteins, XLG1, XLG2, and XLG3, of largely unknown function. Each extra-large G (XLG) protein has a C-terminal Gα-like region and a ∼400 amino acid N-terminal extension. Here we show that the three XLG proteins specifically bind and hydrolyze GTP, despite the fact that these plant-specific proteins lack key conserved amino acid residues important for GTP binding and hydrolysis of GTP in mammalian Gα proteins. Moreover, unlike other known Gα proteins, these activities require Ca(2+) instead of Mg(2+) as a cofactor. Yeast two-hybrid library screening and in vitro protein pull-down assays revealed that XLG2 interacts with the nuclear protein RTV1 (related to vernalization 1). Electrophoretic mobility shift assays show that RTV1 binds to DNA in vitro in a non-sequence-specific manner and that GTP-bound XLG2 promotes the DNA binding activity of RTV1. Overexpression of RTV1 results in early flowering. Combined overexpression of XLG2 and RTV1 enhances this early flowering phenotype and elevates expression of the floral pathway integrator genes, FT and SOC1, but does not repress expression of the floral repressor, FLC. Chromatin immunoprecipitation assays show that XLG2 increases RTV1 binding to FT and SOC1 promoters. Thus, a Ca(2+)-dependent G protein, XLG2, promotes RTV1 DNA binding activity for a subset of floral integrator genes and contributes to floral transition.
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Affiliation(s)
- Jae Bok Heo
- Department of Biology, Penn State University, University Park, Pennsylvania 16802, USA
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42
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Martín-García F, Mendieta-Moreno JI, López-Viñas E, Gómez-Puertas P, Mendieta J. The Role of Gln61 in HRas GTP hydrolysis: a quantum mechanics/molecular mechanics study. Biophys J 2012; 102:152-7. [PMID: 22225809 DOI: 10.1016/j.bpj.2011.11.4005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 11/26/2011] [Accepted: 11/29/2011] [Indexed: 11/19/2022] Open
Abstract
Activation of the water molecule involved in GTP hydrolysis within the HRas·RasGAP system is analyzed using a tailored approach based on hybrid quantum mechanics/molecular mechanics (QM/MM) simulation. A new path emerges: transfer of a proton from the attacking water molecule to a second water molecule, then a different proton is transferred from this second water molecule to the GTP. Gln(61) will stabilize the transient OH(-) and H(3)O(+) molecules thus generated. This newly proposed mechanism was generated by using, for the first time to our knowledge, the entire HRas-RasGAP protein complex in a QM/MM simulation context. It also offers a rational explanation for previous experimental results regarding the decrease of GTPase rate found in the HRas Q61A mutant and the increase exhibited by the HRas Q61E mutant.
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Affiliation(s)
- Fernando Martín-García
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Cientificas-Universidad Autónoma de Madrid), Madrid, Spain
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43
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Alan JK, Lundquist EA. Analysis of Rho GTPase function in axon pathfinding using Caenorhabditis elegans. Methods Mol Biol 2012; 827:339-58. [PMID: 22144285 DOI: 10.1007/978-1-61779-442-1_22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We provide information and protocols for the analysis of Rho GTPase function in axon pathfinding in Caenorhabditis elegans. The powerful molecular, genetic, imaging, and transgenic tools available in C. elegans make it an excellent system in which to study the in vivo roles of Rho GTPases. Methods for imaging of axon morphology in Rho GTPase single and double mutants are provided, as well as methods for the construction of transgenic C. elegans strains carrying exogenously introduced transgenes that drive the expression of constitutively active and dominant negative mutants.
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Affiliation(s)
- Jamie K Alan
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
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44
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Klink BU, Scheidig AJ. New insight into the dynamic properties and the active site architecture of H-Ras p21 revealed by X-ray crystallography at very high resolution. BMC STRUCTURAL BIOLOGY 2010; 10:38. [PMID: 20973973 PMCID: PMC2987813 DOI: 10.1186/1472-6807-10-38] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Accepted: 10/25/2010] [Indexed: 12/01/2022]
Abstract
Background In kinetic crystallography, the usually static method of X-ray diffraction is expanded to allow time-resolved analysis of conformational rearrangements in protein structures. To achieve this, reactions have to be triggered within the protein crystals of interest, and optical spectroscopy can be used to monitor the reaction state. For this approach, a modified form of H-Ras p21 was designed which allows reaction initiation and fluorescence readout of the initiated GTPase reaction within the crystalline state. Rearrangements within the crystallized protein due to the progressing reaction and associated heterogeneity in the protein conformations have to be considered in the subsequent refinement processes. Results X-ray diffraction experiments on H-Ras p21 in different states along the reaction pathway provide detailed information about the kinetics and mechanism of the GTPase reaction. In addition, a very high data quality of up to 1.0 Å resolution allowed distinguishing two discrete subconformations of H-Ras p21, expanding the knowledge about the intrinsic flexibility of Ras-like proteins, which is important for their function. In a complex of H-Ras•GppNHp (guanosine-5'-(β,γ-imido)-triphosphate), a second Mg2+ ion was found to be coordinated to the γ-phosphate group of GppNHp, which positions the hydrolytically active water molecule very close to the attacked γ-phosphorous atom. Conclusion For the structural analysis of very high-resolution data we have used a new 'two-chain-isotropic-refinement' strategy. This refinement provides an alternative and easy to interpret strategy to reflect the conformational variability within crystal structures of biological macromolecules. The presented fluorescent form of H-Ras p21 will be advantageous for fluorescence studies on H-Ras p21 in which the use of fluorescent nucleotides is not feasible.
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Affiliation(s)
- Björn U Klink
- Department of Biophysics, Division of Structural Biology, Saarland University, Homburg/Saar, Germany
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45
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Lukman S, Grant BJ, Gorfe AA, Grant GH, McCammon JA. The distinct conformational dynamics of K-Ras and H-Ras A59G. PLoS Comput Biol 2010; 6. [PMID: 20838576 PMCID: PMC2936511 DOI: 10.1371/journal.pcbi.1000922] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 08/06/2010] [Indexed: 02/07/2023] Open
Abstract
Ras proteins regulate signaling cascades crucial for cell proliferation and differentiation by switching between GTP- and GDP-bound conformations. Distinct Ras isoforms have unique physiological functions with individual isoforms associated with different cancers and developmental diseases. Given the small structural differences among isoforms and mutants, it is currently unclear how these functional differences and aberrant properties arise. Here we investigate whether the subtle differences among isoforms and mutants are associated with detectable dynamical differences. Extensive molecular dynamics simulations reveal that wild-type K-Ras and mutant H-Ras A59G are intrinsically more dynamic than wild-type H-Ras. The crucial switch 1 and switch 2 regions along with loop 3, helix 3, and loop 7 contribute to this enhanced flexibility. Removing the gamma-phosphate of the bound GTP from the structure of A59G led to a spontaneous GTP-to-GDP conformational transition in a 20-ns unbiased simulation. The switch 1 and 2 regions exhibit enhanced flexibility and correlated motion when compared to non-transitioning wild-type H-Ras over a similar timeframe. Correlated motions between loop 3 and helix 5 of wild-type H-Ras are absent in the mutant A59G reflecting the enhanced dynamics of the loop 3 region. Taken together with earlier findings, these results suggest the existence of a lower energetic barrier between GTP and GDP states of the mutant. Molecular dynamics simulations combined with principal component analysis of available Ras crystallographic structures can be used to discriminate ligand- and sequence-based dynamic perturbations with potential functional implications. Furthermore, the identification of specific conformations associated with distinct Ras isoforms and mutants provides useful information for efforts that attempt to selectively interfere with the aberrant functions of these species.
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Affiliation(s)
- Suryani Lukman
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Bioinformatics Institute, Agency for Science, Technology and Research, Singapore
- * E-mail: (SL); (BJG)
| | - Barry J. Grant
- Department of Chemistry and Biochemistry, Center for Theoretical Biological Physics, University of California San Diego, La Jolla, California, United States of America
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, United States of America
- * E-mail: (SL); (BJG)
| | - Alemayehu A. Gorfe
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Guy H. Grant
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - J. Andrew McCammon
- Department of Chemistry and Biochemistry, Center for Theoretical Biological Physics, University of California San Diego, La Jolla, California, United States of America
- Department of Pharmacology, University of California San Diego, La Jolla, California, United States of America
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46
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Allosteric modulation of Ras positions Q61 for a direct role in catalysis. Proc Natl Acad Sci U S A 2010; 107:4931-6. [PMID: 20194776 DOI: 10.1073/pnas.0912226107] [Citation(s) in RCA: 190] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Ras and its effector Raf are key mediators of the Ras/Raf/MEK/ERK signal transduction pathway. Mutants of residue Q61 impair the GTPase activity of Ras and are found prominently in human cancers. Yet the mechanism through which Q61 contributes to catalysis has been elusive. It is thought to position the catalytic water molecule for nucleophilic attack on the gamma-phosphate of GTP. However, we previously solved the structure of Ras from crystals with symmetry of the space group R32 in which switch II is disordered and found that the catalytic water molecule is present. Here we present a structure of wild-type Ras with calcium acetate from the crystallization mother liquor bound at a site remote from the active site and likely near the membrane. This results in a shift in helix 3/loop 7 and a network of H-bonding interactions that propagates across the molecule, culminating in the ordering of switch II and placement of Q61 in the active site in a previously unobserved conformation. This structure suggests a direct catalytic role for Q61 where it interacts with a water molecule that bridges one of the gamma-phosphate oxygen atoms to the hydroxyl group of Y32 to stabilize the transition state of the hydrolysis reaction. We propose that Raf together with the binding of Ca(2+) and a negatively charged group mimicked in our structure by the acetate molecule induces the ordering of switch I and switch II to complete the active site of Ras.
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Rosenberger G, Meien S, Kutsche K. Oncogenic HRAS mutations cause prolonged PI3K signaling in response to epidermal growth factor in fibroblasts of patients with Costello syndrome. Hum Mutat 2009; 30:352-62. [PMID: 19035362 DOI: 10.1002/humu.20855] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Costello syndrome (CS) is a rare congenital disorder characterized by failure to thrive, craniofacial dysmorphisms, cardiac and skin abnormalities, mental retardation, and predisposition to malignancies. CS is caused by heterozygous gain-of-function mutations in HRAS that also occur as somatic alterations in human tumors. HRAS is one of the three classical RAS proteins and cycles between an active, GTP- and an inactive, GDP-bound conformation. We used primary human skin fibroblasts from patients with CS as a model system to study the functional consequences of HRAS mutations on endogenous signaling pathways. The GTP-bound form of HRAS was significantly enriched in CS compared with normal fibroblasts. Active HRAS is known to stimulate both the RAF-MEK-ERK and the PI3K-AKT signaling cascade. Phosphorylation of MEK and ERK was normal in CS fibroblasts under basal conditions and slightly prolonged after epidermal growth factor (EGF) stimulation. Interestingly, basal phosphorylation of AKT was increased yet more in CS fibroblasts. Moreover, AKT phosphorylation was diminished in the early and enhanced in the late phase of EGF stimulation. Taken together, these results document that CS-associated HRAS mutations result in prolonged signal flux in a ligand-dependent manner. Our data suggest that altered cellular response to growth factors rather than constitutive activation of HRAS downstream signaling molecules may contribute to some of the clinical features in patients with CS.
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Affiliation(s)
- Georg Rosenberger
- Institut für Humangenetik, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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Abstract
Purines are critical cofactors in the enzymatic reactions that create and maintain living organisms. In humans, there are approximately 3,266 proteins that utilize purine cofactors and these proteins constitute the so-called purinome. The human purinome encompasses a wide-ranging functional repertoire and many of these proteins are attractive drug targets. For example, it is estimated that 30% of modern drug discovery projects target protein kinases and that modulators of small G-proteins comprise more than 50% of currently marketed drugs. Given the importance of purine-binding proteins to drug discovery, the following review will discuss the forces that mediate protein:purine recognition, the factors that determine druggability of a protein target, and the process of structure-based drug design. A review of purine recognition in representatives of the various purine-binding protein families, as well as the challenges faced in targeting members of the purinome in drug discovery campaigns will also be given.
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Affiliation(s)
- Jeremy M Murray
- Department of Protein Engineering, Genentech, Inc., South San Francisco, CA, USA
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49
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Moreau M, Lee GI, Wang Y, Crane BR, Klessig DF. AtNOS/AtNOA1 is a functional Arabidopsis thaliana cGTPase and not a nitric-oxide synthase. J Biol Chem 2008; 283:32957-67. [PMID: 18801746 DOI: 10.1074/jbc.m804838200] [Citation(s) in RCA: 198] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
AtNOS1 was previously identified as a potential nitric-oxide synthase (NOS) in Arabidopsis thaliana, despite lack of sequence similarity to animal NOSs. Although the dwarf and yellowish leaf phenotype of Atnos1 knock-out mutant plants can be rescued by treatment with exogenous NO, doubts have recently been raised as to whether AtNOS1 is a true NOS. Moreover, depending on the type of physiological responses studied, Atnos1 is not always deficient in NO induction and/or detection, as previously reported. Here, we present experimental evidence showing that AtNOS1 is unable to bind and oxidize arginine to NO. These results support the argument that AtNOS1 is not a NOS. We also show that the renamed NO-associated protein 1 (AtNOA1) is a member of the circularly permuted GTPase family (cGTPase). AtNOA1 specifically binds GTP and hydrolyzes it. Complementation experiments of Atnoa1 mutant plants with different constructs of AtNOA1 show that GTP hydrolysis is necessary but not sufficient for the physiological function of AtNOA1. Mutant AtNOA1 lacking the C-terminal domain, although retaining GTPase activity, failed to complement Atnoa1, suggesting that this domain plays a crucial role in planta. cGTPases appear to be RNA-binding proteins, and the closest homolog of AtNOA1, the Bacillus subtilis YqeH, has been shown to participate in ribosome assembly and stability. We propose a similar function for AtNOA1 and discuss it in the light of its potential role in NO accumulation and plant development.
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Affiliation(s)
- Magali Moreau
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
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Salmonella enterica serovar Typhimurium BipA exhibits two distinct ribosome binding modes. J Bacteriol 2008; 190:5944-52. [PMID: 18621905 DOI: 10.1128/jb.00763-08] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BipA is a highly conserved prokaryotic GTPase that functions to influence numerous cellular processes in bacteria. In Escherichia coli and Salmonella enterica serovar Typhimurium, BipA has been implicated in controlling bacterial motility, modulating attachment and effacement processes, and upregulating the expression of virulence genes and is also responsible for avoidance of host defense mechanisms. In addition, BipA is thought to be involved in bacterial stress responses, such as those associated with virulence, temperature, and symbiosis. Thus, BipA is necessary for securing bacterial survival and successful invasion of the host. Steady-state kinetic analysis and pelleting assays were used to assess the GTPase and ribosome-binding properties of S. enterica BipA. Under normal bacterial growth, BipA associates with the ribosome in the GTP-bound state. However, using sucrose density gradients, we demonstrate that the association of BipA and the ribosome is altered under stress conditions in bacteria similar to those experienced during virulence. The data show that this differential binding is brought about by the presence of ppGpp, an alarmone that signals the onset of stress-related events in bacteria.
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