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Bennie LA, Feng J, Emmerson C, Hyland WB, Matchett KB, McCarthy HO, Coulter JA. Formulating RALA/Au nanocomplexes to enhance nanoparticle internalisation efficiency, sensitising prostate tumour models to radiation treatment. J Nanobiotechnology 2021; 19:279. [PMID: 34538237 PMCID: PMC8451112 DOI: 10.1186/s12951-021-01019-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Gold nanoparticles (AuNP) are effective radiosensitisers, however, successful clinical translation has been impeded by short systemic circulation times and poor internalisation efficiency. This work examines the potential of RALA, a short amphipathic peptide, to enhance the uptake efficiency of negatively charged AuNPs in tumour cells, detailing the subsequent impact of AuNP internalisation on tumour cell radiation sensitivity. RESULTS RALA/Au nanoparticles were formed by optimising the ratio of RALA to citrate capped AuNPs, with assembly occurring through electrostatic interactions. Physical nanoparticle characteristics were determined by UV-vis spectroscopy and dynamic light scattering. Nano-complexes successfully formed at w:w ratios > 20:1 (20 µg RALA:1 µg AuNP) yielding positively charged nanoparticles, sized < 110 nm with PDI values < 0.52. ICP-MS demonstrated that RALA enhanced AuNP internalisation by more than threefold in both PC-3 and DU145 prostate cancer cell models, without causing significant toxicity. Importantly, all RALA-AuNP formulations significantly increased prostate cancer cell radiosensitivity. This effect was greatest using the 25:1 RALA-AuNP formulation, producing a dose enhancement effect (DEF) of 1.54 in PC3 cells. Using clinical radiation energies (6 MV) RALA-AuNP also significantly augmented radiation sensitivity. Mechanistic studies support RALA-AuNP nuclear accumulation resulting in increased DNA damage yields. CONCLUSIONS This is the first study to demonstrate meaningful radiosensitisation using low microgram AuNP treatment concentrations. This effect was achieved using RALA, providing functional evidence to support our previous imaging study indicating RALA-AuNP nuclear accumulation.
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Affiliation(s)
- Lindsey A Bennie
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
| | - Jie Feng
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
| | - Christopher Emmerson
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
| | - Wendy B Hyland
- Western Health & Social Care Trust, North West Cancer Centre, Altnagelvin Hospital, Derry/Londonderry, BT47 6SB, Northern Ireland, UK
| | - Kyle B Matchett
- Northern Ireland Centre for Stratified Medicine, C-TRIC, Altnagelvin Hospital Campus, Derry/Londonderry, BT47 6SB, Northern Ireland, UK
| | - Helen O McCarthy
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
- School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Jonathan A Coulter
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK.
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2
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Chamberlain SG, Gohlke A, Shafiq A, Squires IJ, Owen D, Mott HR. Calmodulin extracts the Ras family protein RalA from lipid bilayers by engagement with two membrane-targeting motifs. Proc Natl Acad Sci U S A 2021; 118:e2104219118. [PMID: 34480001 PMCID: PMC8433508 DOI: 10.1073/pnas.2104219118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 08/05/2021] [Indexed: 11/18/2022] Open
Abstract
RalA is a small GTPase and a member of the Ras family. This molecular switch is activated downstream of Ras and is widely implicated in tumor formation and growth. Previous work has shown that the ubiquitous Ca2+-sensor calmodulin (CaM) binds to small GTPases such as RalA and K-Ras4B, but a lack of structural information has obscured the functional consequences of these interactions. Here, we have investigated the binding of CaM to RalA and found that CaM interacts exclusively with the C terminus of RalA, which is lipidated with a prenyl group in vivo to aid membrane attachment. Biophysical and structural analyses show that the two RalA membrane-targeting motifs (the prenyl anchor and the polybasic motif) are engaged by distinct lobes of CaM and that CaM binding leads to removal of RalA from its membrane environment. The structure of this complex, along with a biophysical investigation into membrane removal, provides a framework with which to understand how CaM regulates the function of RalA and sheds light on the interaction of CaM with other small GTPases, including K-Ras4B.
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Affiliation(s)
- Samuel G Chamberlain
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom
| | - Andrea Gohlke
- Mechanistic and Structural Biology, Discovery Sciences, R&D, AstraZeneca, Cambridge, CB4 0WG, United Kingdom
| | - Arooj Shafiq
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom
| | - Iolo J Squires
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom
| | - Darerca Owen
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom;
| | - Helen R Mott
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom;
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3
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Hurd CA, Brear P, Revell J, Ross S, Mott HR, Owen D. Affinity maturation of the RLIP76 Ral binding domain to inform the design of stapled peptides targeting the Ral GTPases. J Biol Chem 2021; 296:100101. [PMID: 33214225 PMCID: PMC7949049 DOI: 10.1074/jbc.ra120.015735] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/10/2020] [Accepted: 11/19/2020] [Indexed: 12/18/2022] Open
Abstract
Ral GTPases have been implicated as critical drivers of cell growth and metastasis in numerous Ras-driven cancers. We have previously reported stapled peptides, based on the Ral effector RLIP76, that can disrupt Ral signaling. Stapled peptides are short peptides that are locked into their bioactive form using a synthetic brace. Here, using an affinity maturation of the RLIP76 Ral-binding domain, we identified several sequence substitutions that together improve binding to Ral proteins by more than 20-fold. Hits from the selection were rigorously analyzed to determine the contributions of individual residues and two 1.5 Å cocrystal structures of the tightest-binding mutants in complex with RalB revealed key interactions. Insights gained from this maturation were used to design second-generation stapled peptides based on RLIP76 that exhibited vastly improved selectivity for Ral GTPases when compared with the first-generation lead peptide. The binding of second-generation peptides to Ral proteins was quantified and the binding site of the lead peptide on RalB was determined by NMR. Stapled peptides successfully competed with multiple Ral-effector interactions in cellular lysates. Our findings demonstrate how manipulation of a native binding partner can assist in the rational design of stapled peptide inhibitors targeting a protein-protein interaction.
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Affiliation(s)
- Catherine A Hurd
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Paul Brear
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Jefferson Revell
- AstraZeneca, Sir Aaron Klug Building, Granta Park, Cambridge, UK
| | - Sarah Ross
- Research and Early Development, Oncology R&D, AstraZeneca, Cambridge, UK
| | - Helen R Mott
- Department of Biochemistry, University of Cambridge, Cambridge, UK.
| | - Darerca Owen
- Department of Biochemistry, University of Cambridge, Cambridge, UK.
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4
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Abstract
The RAL proteins RALA and RALB belong to the superfamily of small RAS-like GTPases (guanosine triphosphatases). RAL GTPases function as molecular switches in cells by cycling through GDP- and GTP-bound states, a process which is regulated by several guanine exchange factors (GEFs) and two heterodimeric GTPase activating proteins (GAPs). Since their discovery in the 1980s, RALA and RALB have been established to exert isoform-specific functions in central cellular processes such as exocytosis, endocytosis, actin organization and gene expression. Consequently, it is not surprising that an increasing number of physiological functions are discovered to be controlled by RAL, including neuronal plasticity, immune response, and glucose and lipid homeostasis. The critical importance of RAL GTPases for oncogenic RAS-driven cellular transformation and tumorigenesis still attracts most research interest. Here, RAL proteins are key drivers of cell migration, metastasis, anchorage-independent proliferation, and survival. This chapter provides an overview of normal and pathological functions of RAL GTPases and summarizes the current knowledge on the involvement of RAL in human disease as well as current therapeutic targeting strategies. In particular, molecular mechanisms that specifically control RAL activity and RAL effector usage in different scenarios are outlined, putting a spotlight on the complexity of the RAL GTPase signaling network and the emerging theme of RAS-independent regulation and relevance of RAL.
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Affiliation(s)
- Lisa H Apken
- Institute of Molecular Tumor Biology, Faculty of Medicine, University of Münster, Münster, Germany
| | - Andrea Oeckinghaus
- Institute of Molecular Tumor Biology, Faculty of Medicine, University of Münster, Münster, Germany.
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5
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Shafiq A, Campbell LJ, Owen D, Mott HR. NMR resonance assignments for the active and inactive conformations of the small G protein RalA. Biomol NMR Assign 2020; 14:87-91. [PMID: 31916136 PMCID: PMC7069931 DOI: 10.1007/s12104-019-09925-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 12/26/2019] [Indexed: 06/10/2023]
Abstract
The Ral proteins (RalA and RalB) are small G proteins of the Ras family that have been implicated in exocytosis, endocytosis, transcriptional regulation and mitochondrial fission, as well as having a role in tumourigenesis. RalA and RalB are activated downstream of the master regulator, Ras, which causes the nucleotide exchange of GDP for GTP. Here we report the 1H, 15 N and 13C resonance assignments of RalA in its active form bound to the GTP analogue GMPPNP. We also report the backbone assignments of RalA in its inactive, GDP-bound form. The assignments give insight into the switch regions, which change conformation upon nucleotide exchange. These switch regions are invisible in the spectra of the active, GMPPNP bound form but the residues proximal to the switches can be monitored. RalA is also an important drug target due to its over activation in some cancers and these assignments will be extremely useful for NMR-based screening approaches.
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Affiliation(s)
- Arooj Shafiq
- Department of Biochemistry, 80, Tennis Court Road, Cambridge, CB2 1GA, UK
- Barrett Hodgson University, Korangi Creek, Salim Habib Campus, NC-24, Deh Dih, Korangi Creek, Karachi, 74900, Sindh, Pakistan
| | - Louise J Campbell
- Department of Biochemistry, 80, Tennis Court Road, Cambridge, CB2 1GA, UK
| | - Darerca Owen
- Department of Biochemistry, 80, Tennis Court Road, Cambridge, CB2 1GA, UK
| | - Helen R Mott
- Department of Biochemistry, 80, Tennis Court Road, Cambridge, CB2 1GA, UK.
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6
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Hiatt SM, Neu MB, Ramaker RC, Hardigan AA, Prokop JW, Hancarova M, Prchalova D, Havlovicova M, Prchal J, Stranecky V, Yim DKC, Powis Z, Keren B, Nava C, Mignot C, Rio M, Revah-Politi A, Hemati P, Stong N, Iglesias AD, Suchy SF, Willaert R, Wentzensen IM, Wheeler PG, Brick L, Kozenko M, Hurst ACE, Wheless JW, Lacassie Y, Myers RM, Barsh GS, Sedlacek Z, Cooper GM. De novo mutations in the GTP/GDP-binding region of RALA, a RAS-like small GTPase, cause intellectual disability and developmental delay. PLoS Genet 2018; 14:e1007671. [PMID: 30500825 PMCID: PMC6291162 DOI: 10.1371/journal.pgen.1007671] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 12/12/2018] [Accepted: 08/30/2018] [Indexed: 01/22/2023] Open
Abstract
Mutations that alter signaling of RAS/MAPK-family proteins give rise to a group of Mendelian diseases known as RASopathies. However, among RASopathies, the matrix of genotype-phenotype relationships is still incomplete, in part because there are many RAS-related proteins and in part because the phenotypic consequences may be variable and/or pleiotropic. Here, we describe a cohort of ten cases, drawn from six clinical sites and over 16,000 sequenced probands, with de novo protein-altering variation in RALA, a RAS-like small GTPase. All probands present with speech and motor delays, and most have intellectual disability, low weight, short stature, and facial dysmorphism. The observed rate of de novo RALA variants in affected probands is significantly higher (p = 4.93 x 10−11) than expected from the estimated random mutation rate. Further, all de novo variants described here affect residues within the GTP/GDP-binding region of RALA; in fact, six alleles arose at only two codons, Val25 and Lys128. The affected residues are highly conserved across both RAL- and RAS-family genes, are devoid of variation in large human population datasets, and several are homologous to positions at which disease-associated variants have been observed in other GTPase genes. We directly assayed GTP hydrolysis and RALA effector-protein binding of the observed variants, and found that all but one tested variant significantly reduced both activities compared to wild-type. The one exception, S157A, reduced GTP hydrolysis but significantly increased RALA-effector binding, an observation similar to that seen for oncogenic RAS variants. These results show the power of data sharing for the interpretation and analysis of rare variation, expand the spectrum of molecular causes of developmental disability to include RALA, and provide additional insight into the pathogenesis of human disease caused by mutations in small GTPases. While many causes of developmental disabilities have been identified, a large number of affected children cannot be diagnosed despite extensive medical testing. Previously unknown genetic factors are likely to be the culprits in many of these cases. Using DNA sequencing, and by sharing information among many doctors and researchers, we have identified a set of individuals with developmental problems who all have changes to the same gene, RALA. The affected individuals all have similar symptoms, including intellectual disability, speech delay (or no speech), and problems with motor skills like walking. In nearly all of these cases (10 of 11), the genetic change found in the child was not inherited from either parent. The locations and biological properties of these changes suggest that they are likely to disrupt the normal functions of RALA. Functional experiments also show that the genetic changes found in these individuals alter two key functions of RALA. Together, we have provided evidence that genetic changes in RALA can cause developmental disabilities. These results will allow doctors and researchers to identify additional children with the same condition, providing a clinical diagnosis to these families and leading to new research opportunities.
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Affiliation(s)
- Susan M. Hiatt
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
| | - Matthew B. Neu
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Ryne C. Ramaker
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Andrew A. Hardigan
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Jeremy W. Prokop
- Department of Pediatrics and Human Development, Michigan State University, East Lansing, MI, United States of America
| | - Miroslava Hancarova
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Darina Prchalova
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Marketa Havlovicova
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Jan Prchal
- Laboratory of NMR Spectroscopy, University of Chemistry and Technology, Prague, Czech Republic
| | - Viktor Stranecky
- Department of Pediatrics and Adolescent Medicine, Diagnostic and Research Unit for Rare Diseases, Charles University 1st Faculty of Medicine and General University Hospital, Prague, Czech Republic
| | - Dwight K. C. Yim
- Kaiser Permanente-Hawaii, Honolulu, HI, United States of America
| | - Zöe Powis
- Department of Emerging Genetic Medicine, Ambry Genetics, Aliso Viejo, CA, United States of America
| | - Boris Keren
- Department of Genetics, La Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Caroline Nava
- Department of Genetics, La Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Cyril Mignot
- Department of Genetics, La Pitié-Salpêtrière Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France
- Centre de Référence Déficiences Intellectuelles de Causes Rares, Paris, France
- Groupe de Recherche Clinique UPMC "Déficience Intellectuelle et Autisme", Paris, France
| | - Marlene Rio
- Centre de Référence Déficiences Intellectuelles de Causes Rares, Paris, France
- Assistance Publique-Hôpitaux de Paris, service de Génétique, Hôpital Necker-Enfants-Malades, Paris, France
| | - Anya Revah-Politi
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY, United States of America
| | - Parisa Hemati
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY, United States of America
| | - Nicholas Stong
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY, United States of America
| | - Alejandro D. Iglesias
- Division of Clinical Genetics, Department of Pediatrics, Columbia University Medical Center, New York, NY, United States of America
| | | | | | | | - Patricia G. Wheeler
- Arnold Palmer Hospital, Division of Genetics, Orlando, FL, United States of America
| | - Lauren Brick
- Department of Genetics, McMaster Children's Hospital, Hamilton, Ontario, Canada
| | - Mariya Kozenko
- Department of Genetics, McMaster Children's Hospital, Hamilton, Ontario, Canada
| | - Anna C. E. Hurst
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - James W. Wheless
- Division of Pediatric Neurology, University of Tennessee Health Science Center, Neuroscience Institute & Le Bonheur Comprehensive Epilepsy Program, Memphis, TN, United States of America
- Le Bonheur Children’s Hospital, Memphis, TN, United States of America
| | - Yves Lacassie
- Division of Clinical Genetics, Louisiana State University Health Sciences Center, New Orleans, LA, United States of America
- Department of Genetics, Children's Hospital, New Orleans, LA, United States of America
| | - Richard M. Myers
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
| | - Gregory S. Barsh
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
| | - Zdenek Sedlacek
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Gregory M. Cooper
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
- * E-mail:
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7
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Gray CH, Konczal J, Mezna M, Ismail S, Bower J, Drysdale M. A fully automated procedure for the parallel, multidimensional purification and nucleotide loading of the human GTPases KRas, Rac1 and RalB. Protein Expr Purif 2017; 132:75-84. [PMID: 28137655 PMCID: PMC5415301 DOI: 10.1016/j.pep.2017.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 01/26/2017] [Accepted: 01/26/2017] [Indexed: 11/24/2022]
Abstract
Small GTPases regulate many key cellular processes and their role in human disease validates many proteins in this class as desirable targets for therapeutic intervention. Reliable recombinant production of GTPases, often in the active GTP loaded state, is a prerequisite for the prosecution of drug discovery efforts. The preparation of these active forms can be complex and often constricts the supply to the reagent intensive techniques used in structure base drug discovery. We have established a fully automated, multidimensional protein purification strategy for the parallel production of the catalytic G-domains of KRas, Rac1 and RalB GTPases in the active form. This method incorporates a four step chromatography purification with TEV protease-mediated affinity tag cleavage and a conditioning step that achieves the activation of the GTPase by exchanging GDP for the non-hydrolyzable GTP analogue GMPPnP. We also demonstrate that an automated method is efficient at loading of KRas with mantGDP for application in a SOS1 catalysed fluorescent nucleotide exchange assay. In comparison to more conventional manual workflows the automated method offers marked advantages in method run time and operator workload. This reduces the bottleneck in protein production while generating products that are highly purified and effectively loaded with nucleotide analogues.
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Affiliation(s)
- Christopher H Gray
- Drug Discovery Program, CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK.
| | - Jennifer Konczal
- Drug Discovery Program, CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Mokdad Mezna
- Drug Discovery Program, CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Shehab Ismail
- CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Justin Bower
- Drug Discovery Program, CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Martin Drysdale
- Drug Discovery Program, CRUK Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
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8
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Rajasekar K, Campbell L, Nietlispach D, Owen D, Mott H. The structure of the RLIP76 RhoGAP-Ral binding domain dyad: fixed position of the domains leads to dual engagement of small G proteins at the membrane. Structure 2013; 21:2131-42. [PMID: 24207123 PMCID: PMC3852207 DOI: 10.1016/j.str.2013.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 01/15/2023]
Abstract
RLIP76 is an effector for Ral small GTPases, which in turn lie downstream of the master regulator Ras. Evidence is growing that Ral and RLIP76 play a role in tumorigenesis, invasion, and metastasis. RLIP76 contains both a RhoGAP domain and a Ral binding domain (GBD) and is, therefore, a node between Ras and Rho family signaling. The structure of the RhoGAP-GBD dyad reveals that the RLIP76 RhoGAP domain adopts a canonical RhoGAP domain structure and that the linker between the two RLIP76 domains is structured, fixing the orientation of the two domains and allowing RLIP76 to interact with Rho-family GTPases and Ral simultaneously. However, the juxtaposed domains do not influence each other functionally, suggesting that the RLIP76-Ral interaction controls cellular localization and that the fixed orientation of the two domains orientates the RhoGAP domain with respect to the membrane, allowing it to be perfectly poised to engage its target G proteins.
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Affiliation(s)
- Karthik V. Rajasekar
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Louise J. Campbell
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Daniel Nietlispach
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Darerca Owen
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
| | - Helen R. Mott
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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9
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Fenwick RB, Prasannan S, Campbell LJ, Evetts KA, Nietlispach D, Owen D, Mott HR. Resonance assignments for the RLIP76 Ral binding domain in its free form and in complex with the small G protein RalB. Biomol NMR Assign 2008; 2:191-194. [PMID: 19636902 DOI: 10.1007/s12104-008-9118-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Accepted: 09/08/2008] [Indexed: 05/28/2023]
Abstract
We report (1)H and (15)N resonance assignments for the free Ral binding domain of RLIP76 (393-446) and the (1)H, (15)N and (13)C resonance assignments for the RLIP76 Ral binding domain in complex with the active conformation of RalB. The BMRB accession code for free RLIP76 is 15524 and in complex with RalB is 15525.
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Affiliation(s)
- R Bryn Fenwick
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK
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10
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Fenwick RB, Prasannan S, Campbell LJ, Evetts KA, Nietlispach D, Owen D, Mott HR. 1H, 13C and 15N resonance assignments for the active conformation of the small G protein RalB in complex with its effector RLIP76. Biomol NMR Assign 2008; 2:179-82. [PMID: 19636899 DOI: 10.1007/s12104-008-9115-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Accepted: 09/08/2008] [Indexed: 05/28/2023]
Abstract
We report here the (1)H, (15)N and (13)C resonance assignments for the small G protein RalB bound to the GTP analogue, GMPPNP and complexed with the Ral binding domain of its downstream effector RLIP76. The BMRB accession code is 15525.
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Affiliation(s)
- R Bryn Fenwick
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
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11
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Prasannan S, Fenwick RB, Campbell LJ, Evetts KA, Nietlispach D, Owen D, Mott HR. 1H, 13C and 15N resonance assignments for the small G protein RalB in its active conformation. Biomol NMR Assign 2007; 1:147-149. [PMID: 19636851 DOI: 10.1007/s12104-007-9040-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 07/07/2007] [Indexed: 05/28/2023]
Abstract
We report 1H, 13C and 15N resonance assignments for the small G protein RalB in its active conformation. Backbone amide dynamics parameters for a majority of residues have also been obtained. The BMRB accession code is 15230 [corrected]
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Affiliation(s)
- Sunil Prasannan
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB21GA, UK
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12
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Vogelsgesang M, Pautsch A, Aktories K. C3 exoenzymes, novel insights into structure and action of Rho-ADP-ribosylating toxins. Naunyn Schmiedebergs Arch Pharmacol 2006; 374:347-60. [PMID: 17146673 DOI: 10.1007/s00210-006-0113-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/18/2006] [Indexed: 12/19/2022]
Abstract
The family of C3-like exoenzymes comprises seven bacterial ADP-ribosyltransferases of different origin. The common hallmark of these exoenzymes is the selective N-ADP-ribosylation of the low molecular mass GTP-binding proteins RhoA, B, and C and inhibition of signal pathways controlled by Rho GTPases. Therefore, C3-like exoenzymes were applied as pharmacological tools for analyses of cellular functions of Rho protein in numerous studies. Recent structural and functional analyses of C3-like exoenzymes provide detailed information on the molecular mechanisms and functional consequences of ADP-ribosylation catalyzed by these toxins. More recently additional non-enzymatic actions of C3-like ADP-ribosyltransferases have been identified showing that C3 transferases from Clostridium botulinum and Clostridium limosum form a GDI-like complex with the Ras-like low molecular mass GTPase Ral without ADP-ribosylation. These results add novel information on the molecular mode of action(s) of C3-like exoenzymes and are discussed in this review.
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Affiliation(s)
- Martin Vogelsgesang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-University Freiburg, Otto-Krayer-Haus, Albertstrasse 25, Freiburg, Germany
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13
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Abstract
Small GTPases, which are binary switches regulating various signal transduction cascades, function not only to relay signals but also to integrate them from multiple signalling branches. For example, RalA activity is regulated by at least three signalling cascades involving Ras, Rac or PI3K (phosphoinositide 3-kinase). To untangle such complicated regulatory mechanisms, we have been developing probes for GTPases, kinases and phosphatidylinositols based on the principle of FRET (fluorescence resonance energy transfer). We demonstrated previously that, upon EGF (epidermal growth factor) stimulation, Ras activity increases diffusely in the plasma membrane, whereas RalA activity increases predominantly in lamellipodial protrusions. Here, we show that the level of PtdIns(3,4,5)P3 is increased diffusely in the plasma membrane, whereas, in the central region, the level of PtdIns(3,4)P2 is increased more in the nascent lamellipodia than in the plasma membrane. The distribution and time course of Akt activation are similar to those of increased PtdIns(3,4)P2 levels. These observations suggest that the increase in PtdIns(3,4)P2 and the subsequent activation of Akt may be responsible for the localized activation of RalA. Thus the signals from Ras and PI3K converge at the level of Ral GEFs (guanine nucleotide-exchange factors), and this convergence restricts the area of RalA activation.
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Affiliation(s)
- H Yoshizaki
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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14
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Pautsch A, Vogelsgesang M, Tränkle J, Herrmann C, Aktories K. Crystal structure of the C3bot-RalA complex reveals a novel type of action of a bacterial exoenzyme. EMBO J 2005; 24:3670-80. [PMID: 16177825 PMCID: PMC1276701 DOI: 10.1038/sj.emboj.7600813] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Accepted: 08/22/2005] [Indexed: 12/21/2022] Open
Abstract
C3 exoenzymes from bacterial pathogens ADP-ribosylate and inactivate low-molecular-mass GTPases of the Rho subfamily. Ral, a Ras subfamily GTPase, binds the C3 exoenzymes from Clostridium botulinum and C. limosum with high affinity without being a substrate for ADP ribosylation. In the complex, the ADP-ribosyltransferase activity of C3 is blocked, while binding of NAD and NAD-glycohydrolase activity remain. Here we report the crystal structure of C3 from C. botulinum in a complex with GDP-bound RalA at 1.8 A resolution. C3 binds RalA with a helix-loop-helix motif that is adjacent to the active site. A quaternary complex with NAD suggests a mode for ADP-ribosyltransferase inhibition. Interaction of C3 with RalA occurs at a unique interface formed by the switch-II region, helix alpha3 and the P loop of the GTPase. C3-binding stabilizes the GDP-bound conformation of RalA and blocks nucleotide release. Our data indicate that C. botulinum exoenzyme C3 is a single-domain toxin with bifunctional properties targeting Rho GTPases by ADP ribosylation and Ral by a guanine nucleotide dissociation inhibitor-like effect, which blocks nucleotide exchange.
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Affiliation(s)
- Alexander Pautsch
- Structural Research, Department of Integrated Lead Discovery, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Martin Vogelsgesang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Freiburg, Germany
| | - Jens Tränkle
- Physikalische Chemie I, Ruhr-Universität Bochum, Bochum, Germany
| | | | - Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Freiburg, Germany
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Universität Freiburg, Otto-Krayer-Haus, Albertstrasse 25, 79104 Freiburg, Germany. Tel.: +49 761 203 5301; Fax: +49 761 203 5311; E-mail:
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15
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Jin R, Junutula JR, Matern HT, Ervin KE, Scheller RH, Brunger AT. Exo84 and Sec5 are competitive regulatory Sec6/8 effectors to the RalA GTPase. EMBO J 2005; 24:2064-74. [PMID: 15920473 PMCID: PMC1150893 DOI: 10.1038/sj.emboj.7600699] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Accepted: 05/06/2005] [Indexed: 12/31/2022] Open
Abstract
The Sec6/8 complex, also known as the exocyst complex, is an octameric protein complex that has been implicated in tethering of secretory vesicles to specific regions on the plasma membrane. Two subunits of the Sec6/8 complex, Exo84 and Sec5, have recently been shown to be effector targets for active Ral GTPases. However, the mechanism by which Ral proteins regulate the Sec6/8 activities remains unclear. Here, we present the crystal structure of the Ral-binding domain of Exo84 in complex with active RalA. The structure reveals that the Exo84 Ral-binding domain adopts a pleckstrin homology domain fold, and that RalA interacts with Exo84 via an extended interface that includes both switch regions. Key residues of Exo84 and RalA were found that determine the specificity of the complex interactions; these interactions were confirmed by mutagenesis binding studies. Structural and biochemical data show that Exo84 and Sec5 competitively bind to active RalA. Taken together, these results further strengthen the proposed role of RalA-regulated assembly of the Sec6/8 complex.
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Affiliation(s)
- Rongsheng Jin
- Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | | | - Hugo T Matern
- Genentech Inc., 1 DNA Way, South San Francisco, CA, USA
| | - Karen E Ervin
- Genentech Inc., 1 DNA Way, South San Francisco, CA, USA
| | | | - Axel T Brunger
- Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
- Departments of Molecular and Cellular Physiology, Neurology and Neurological Science, Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, CA, USA
- Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University, James H Clark Center, E300C, 318 Campus Drive, Stanford, CA 94305-5432, USA. Tel.:+1 650 736 1031; Fax: +1 650 736 1961; E-mail:
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16
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Holbourn KP, Sutton JM, Evans HR, Shone CC, Acharya KR. Molecular recognition of an ADP-ribosylating Clostridium botulinum C3 exoenzyme by RalA GTPase. Proc Natl Acad Sci U S A 2005; 102:5357-62. [PMID: 15809419 PMCID: PMC556266 DOI: 10.1073/pnas.0501525102] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Indexed: 01/19/2023] Open
Abstract
C3 exoenzymes (members of the ADP-ribosyltranferase family) are produced by Clostridium botulinum (C3bot1 and -2), Clostridium limosum (C3lim), Bacillus cereus (C3cer), and Staphylococcus aureus (C3stau1-3). These exoenzymes lack a translocation domain but are known to specifically inactivate Rho GTPases in host target cells. Here, we report the crystal structure of C3bot1 in complex with RalA (a GTPase of the Ras subfamily) and GDP at a resolution of 2.66 A. RalA is not ADP-ribosylated by C3 exoenzymes but inhibits ADP-ribosylation of RhoA by C3bot1, C3lim, and C3cer to different extents. The structure provides an insight into the molecular interactions between C3bot1 and RalA involving the catalytic ADP-ribosylating turn-turn (ARTT) loop from C3bot1 and helix alpha4 and strand beta6 (which are not part of the GDP-binding pocket) from RalA. The structure also suggests a molecular explanation for the different levels of C3-exoenzyme inhibition by RalA and why RhoA does not bind C3bot1 in this manner.
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Affiliation(s)
- Kenneth P Holbourn
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
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17
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Spiliotis M, Brehm K. Echinococcus multilocularis: identification and molecular characterization of a Ral-like small GTP-binding protein. Exp Parasitol 2004; 107:163-72. [PMID: 15363942 DOI: 10.1016/j.exppara.2004.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Revised: 04/02/2004] [Accepted: 05/27/2004] [Indexed: 11/24/2022]
Abstract
In mammals, Ral (Ras-like) GTPases have been implicated in the regulation of several cellular key processes such as oncogenic transformation, endocytosis, and actin-cytoskeleton dynamics. Here we provide, for the first time, molecular data on a Ral homologue from a parasitic helminth. We have cloned and characterized the complete cDNA molecule and the chromosomal locus encoding a novel GTP binding protein, EmRal, of the human parasite Echinococcus multilocularis. The encoded protein contained all highly conserved amino acid residues of the protein family at corresponding positions and shared significant sequence homologies with human RalA (53% identity) and RalB (54%). Upon heterologous expression of EmRal in Escherichia coli, the recombinant protein was able to bind GTP, thus indicating functionality of the Echinococcus factor. Using an in vitro prenylation assay, the purified protein was shown to be geranylgernylated, but not farnesylated, in both rabbit reticulocyte and Echinococcus cell extracts. The EmRal mRNA was found to be processed via trans-splicing and, using RT-PCR and virtual Northern blot experiments, expression of the factor could be demonstrated for the larval stages metacestode and protoscolex during an infection of the intermediate host. The data presented herein provide a solid basis for further investigations on Ras-Ral signaling mechanisms in Echinococcus.
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Affiliation(s)
- Markus Spiliotis
- Institute of Hygiene and Microbiology, University of Würzburg, Josef-Schneider-Strasse 2, D-97080, Germany
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18
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Kiel C, Selzer T, Shaul Y, Schreiber G, Herrmann C. Electrostatically optimized Ras-binding Ral guanine dissociation stimulator mutants increase the rate of association by stabilizing the encounter complex. Proc Natl Acad Sci U S A 2004; 101:9223-8. [PMID: 15197281 PMCID: PMC438957 DOI: 10.1073/pnas.0401160101] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Association of two proteins can be described as a two-step process, with the formation of an encounter complex followed by desolvation and establishment of a tight complex. Here, by using the computer algorithm PARE, we designed a set of mutants of the Ras effector protein Ral guanine nucleotide dissociation stimulator (RalGDS) with optimized electrostatic steering. The fastest binding RalGDS mutant, M26K,D47K,E54K, binds Ras 14-fold faster and 25-fold tighter compared with WT. A linear correlation was found between the calculated and experimental data, with a correlation coefficient of 0.97 and a slope of 0.65 for the 24 mutants produced. The data suggest that increased electrostatic steering specifically stabilizes the encounter complex and transition state. This conclusion is backed up by Phi analysis of the encounter complex and transition state of the RalGDS(M26K,D47K,E54K)/Ras complex, with both values being close to 1. Upon further formation of the final complex, the increased Coulombic interactions are probably counterbalanced by the cost of desolvation of charges, keeping the dissociation rate constant almost unchanged. This mechanism is also reflected by the mutual compensation of enthalpy and entropy changes quantified by isothermal titration calorimetry. The binding constants of the faster binding RalGDS mutants toward Ras are similar to those of Raf, the most prominent Ras effector, suggesting that the design methodology may be used to switch between signal transduction pathways.
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Affiliation(s)
- C Kiel
- Max-Planck-Institut fur Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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19
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Mott HR, Nietlispach D, Hopkins LJ, Mirey G, Camonis JH, Owen D. Structure of the GTPase-binding domain of Sec5 and elucidation of its Ral binding site. J Biol Chem 2003; 278:17053-9. [PMID: 12624092 DOI: 10.1074/jbc.m300155200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The exocyst complex is involved in the final stages of exocytosis, when vesicles are targeted to the plasma membrane and dock. The regulation of exocytosis is vital for a number of processes, for example, cell polarity, embryogenesis, and neuronal growth formation. Regulation of the exocyst complex in mammals was recently shown to be dependent upon binding of the small G protein, Ral, to Sec5, a central component of the exocyst. This interaction is thought to be necessary for anchoring the exocyst to secretory vesicles. We have determined the structure of the Ral-binding domain of Sec5 and shown that it adopts a fold that has not been observed in a G protein effector before. This fold belongs to the immunoglobulin superfamily in a subclass known as IPT domains. We have mapped the Ral binding site on this domain and found that it overlaps with protein-protein interaction sites on other IPT domains but that it is completely different from the G protein-geranyl-geranyl interaction face of the Ig-like domain of the Rho guanine nucleotide dissociation inhibitor. This mapping, along with available site-directed mutagenesis data, allows us to predict how Ral and Sec5 may interact.
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Affiliation(s)
- Helen R Mott
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, United Kingdom.
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20
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Bhattacharya M, Anborgh PH, Babwah AV, Dale LB, Dobransky T, Benovic JL, Feldman RD, Verdi JM, Rylett RJ, Ferguson SSG. Beta-arrestins regulate a Ral-GDS Ral effector pathway that mediates cytoskeletal reorganization. Nat Cell Biol 2002; 4:547-55. [PMID: 12105416 DOI: 10.1038/ncb821] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
beta-Arrestins are important in chemoattractant receptor-induced granule release, a process that may involve Ral-dependent regulation of the actin cytoskeleton. We have identified the Ral GDP dissociation stimulator (Ral-GDS) as a beta-arrestin-binding protein by yeast two-hybrid screening and co-immunoprecipitation from human polymorphonuclear neutrophilic leukocytes (PMNs). Under basal conditions, Ral-GDS is localized to the cytosol and remains inactive in a complex formed with beta-arrestins. In response to formyl-Met-Leu-Phe (fMLP) receptor stimulation, beta-arrestin Ral-GDS protein complexes dissociate and Ral-GDS translocates with beta-arrestin from the cytosol to the plasma membrane, resulting in the Ras-independent activation of the Ral effector pathway required for cytoskeletal rearrangement. The subsequent re-association of beta-arrestin Ral-GDS complexes is associated with the inactivation of Ral signalling. Thus, beta-arrestins regulate multiple steps in the Ral-dependent processes that result in chemoattractant-induced cytoskeletal reorganization.
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Affiliation(s)
- Moshmi Bhattacharya
- Cell Biology Research Group, The John P. Robarts Research Institute, The University of Western Ontario, 100 Perth Drive, London, Ontario, N6A 5K8, Canada
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21
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Fraylick JE, Rucks EA, Greene DM, Vincent TS, Olson JC. Eukaryotic cell determination of ExoS ADP-ribosyltransferase substrate specificity. Biochem Biophys Res Commun 2002; 291:91-100. [PMID: 11829467 DOI: 10.1006/bbrc.2002.6402] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exoenzyme S (ExoS) ADP-ribosylates multiple low-molecular-mass G- (LMMG-) proteins in vitro. Identification of the in vivo substrate specificity of ExoS has been hindered by its bacterial contact delivery into eukaryotic cells and difficulties in identifying ADP-ribosylated proteins within cells. Two-dimensional electrophoresis comparisons of substrate modifications by ExoS in vitro to that following bacterial translocation into HT-29 epithelial cells identified Ras, Ral, and Rab proteins and Rac1 as in vivo substrates of ExoS ADPRT activity. Cellular fractionation studies identified a relationship between membrane association and efficiency of substrate modification. Moreover, Rac and Cdc42 relocalized to the membrane in response to ExoS. Comparisons of substrate modification to time of exposure to ExoS identified a progression of substrate modification, with Ras, RalA, and Rab5 modified first, followed by Rab8 and 11, then Rab7 and Rac1. The data support that intrinsic properties of LMMG-proteins and their subcellular localization are determinants of bacterially translocated ExoS substrate selectivity.
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Affiliation(s)
- Jennifer E Fraylick
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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22
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Rudolph MG, Linnemann T, Grunewald P, Wittinghofer A, Vetter IR, Herrmann C. Thermodynamics of Ras/effector and Cdc42/effector interactions probed by isothermal titration calorimetry. J Biol Chem 2001; 276:23914-21. [PMID: 11292826 DOI: 10.1074/jbc.m011600200] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proliferation, differentiation, and morphology of eucaryotic cells is regulated by a large network of signaling molecules. Among the major players are members of the Ras and Rho/Rac subfamilies of small GTPases that bind to different sets of effector proteins. Recognition of multiple effectors is important for communicating signals into different pathways, leading to the question of how an individual GTPase achieves tight binding to diverse targets. To understand the observed specificity, detailed information about binding energetics is expected to complement the information gained from the three-dimensional structures of GTPase/effector protein complexes. Here, the thermodynamics of the interaction of four closely related members of the Ras subfamily with four different effectors and, additionally, the more distantly related Cdc42/WASP couple were quantified by means of isothermal titration calorimetry. The heat capacity changes upon complex formation were rationalized in light of the GTPase/effector complex structures. Changes in enthalpy, entropy, and heat capacity of association with various Ras proteins are similar for the same effector. In contrast, although the structures of the Ras-binding domains are similar, the thermodynamics of the Ras/Raf and Ras/Ral guanine nucleotide dissociation stimulator interactions are quite different. The energy profile of the Cdc42/WASP interaction is similar to Ras/Ral guanine nucleotide dissociation stimulator, despite largely different structures and interface areas of the complexes. Water molecules in the interface cannot fully account for the observed discrepancy but may explain the large range of Ras/effector binding specificity. The differences in the thermodynamic parameters, particularly the entropy changes, could help in the design of effector-specific inhibitors that selectively block a single pathway.
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Affiliation(s)
- M G Rudolph
- Abteilung Strukturelle Biologie, Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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