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Wood SJ, Goldufsky JW, Seu MY, Dorafshar AH, Shafikhani SH. Pseudomonas aeruginosa Cytotoxins: Mechanisms of Cytotoxicity and Impact on Inflammatory Responses. Cells 2023; 12:cells12010195. [PMID: 36611990 PMCID: PMC9818787 DOI: 10.3390/cells12010195] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/01/2022] [Accepted: 12/01/2022] [Indexed: 01/05/2023] Open
Abstract
Pseudomonas aeruginosa is one of the most virulent opportunistic Gram-negative bacterial pathogens in humans. It causes many acute and chronic infections with morbidity and mortality rates as high as 40%. P. aeruginosa owes its pathogenic versatility to a large arsenal of cell-associated and secreted virulence factors which enable this pathogen to colonize various niches within hosts and protect it from host innate immune defenses. Induction of cytotoxicity in target host cells is a major virulence strategy for P. aeruginosa during the course of infection. P. aeruginosa has invested heavily in this strategy, as manifested by a plethora of cytotoxins that can induce various forms of cell death in target host cells. In this review, we provide an in-depth review of P. aeruginosa cytotoxins based on their mechanisms of cytotoxicity and the possible consequences of their cytotoxicity on host immune responses.
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Affiliation(s)
- Stephen J. Wood
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Josef W. Goldufsky
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
| | - Michelle Y. Seu
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Amir H. Dorafshar
- Department of Surgery, Division of Plastic and Reconstructive Surgery, Rush University Medical Center, Chicago, IL 60612, USA
| | - Sasha H. Shafikhani
- Department of Medicine, Division of Hematology, Oncology and Cell Therapy, Rush University Medical Center, Chicago, IL 60612, USA
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL 60612, USA
- Cancer Center, Rush University Medical Center, Chicago, IL 60612, USA
- Correspondence:
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Evaluating Bacterial Pathogenesis Using a Model of Human Airway Organoids Infected with Pseudomonas aeruginosa Biofilms. Microbiol Spectr 2022; 10:e0240822. [PMID: 36301094 PMCID: PMC9769610 DOI: 10.1128/spectrum.02408-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Pseudomonas aeruginosa is one of the leading invasive agents of human pulmonary infection, especially in patients with compromised immunity. Prior studies have used various in vitro models to establish P. aeruginosa infection and to analyze transcriptomic profiles of either the host or pathogen, and yet how much those works are relevant to the genuine human airway still raises doubts. In this study, we cultured and differentiated human airway organoids (HAOs) that recapitulate, to a large extent, the histological and physiological features of the native human mucociliary epithelium. HAOs were then employed as a host model to monitor P. aeruginosa biofilm development. Through dual-species transcriptome sequencing (RNA-seq) analyses, we found that quorum sensing (QS) and several associated protein secretion systems were significantly upregulated in HAO-associated bacteria. Cocultures of HAOs and QS-defective mutants further validated the role of QS in the maintenance of a robust biofilm and disruption of host tissue. Simultaneously, the expression magnitude of multiple inflammation-associated signaling pathways was higher in the QS mutant-infected HAOs, suggesting that QS promotes immune evasion at the transcriptional level. Altogether, modeling infection of HAOs by P. aeruginosa captured several crucial facets in host responses and bacterial pathogenesis, with QS being the most dominant virulence pathway showing profound effects on both bacterial biofilm and host immune responses. Our results revealed that HAOs are an optimal model for studying the interaction between the airway epithelium and bacterial pathogens. IMPORTANCE Human airway organoids (HAOs) are an organotypic model of human airway mucociliary epithelium. The HAOs can closely resemble their origin organ in terms of epithelium architecture and physiological function. Accumulating studies have revealed the great values of the HAO cultures in host-pathogen interaction research. In this study, HAOs were used as a host model to grow Pseudomonas aeruginosa biofilm, which is one of the most common pathogens found in pulmonary infection cases. Dual transcriptome sequencing (RNA-seq) analyses showed that the cocultures have changed the gene expression pattern of both sides significantly and simultaneously. Bacterial quorum sensing (QS), the most upregulated pathway, contributed greatly to biofilm formation, disruption of barrier function, and subversion of host immune responses. Our study therefore provides a global insight into the transcriptomic responses of both P. aeruginosa and human airway epithelium.
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3
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Sangeet S, Pawar S, Nawani N, Junnarkar M, Gaikwad S. Computational approach to attenuate virulence of Pseudomonas aeruginosa through bioinspired silver nanoparticles. 3 Biotech 2022; 12:317. [PMID: 36276439 PMCID: PMC9547761 DOI: 10.1007/s13205-022-03367-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/17/2022] [Indexed: 11/24/2022] Open
Abstract
In this study we aim to investigate the computational docking approach of biofabricated silver nanoparticles against P. aeruginosa virulent exoenzymes, such as ExoS and ExoY. Therefore, the synthesis and characterization of biofabricated silver nanoparticles using Piper betle leaves (Pb-AgNPs) were carried out. The surface topology and functional group attachment on the surface of Pb-AgNPs were analyzed using UV-visible spectroscopy, Scanning Electron Microscopy, Fourier Transformed Infrared Spectroscopy (FTIR), and X-Ray Diffraction. The FTIR analysis revealed that the synthesized silver nanoparticles were capped with P. betle phytochemicals importantly Eugenol and Hydroxychavicol. These are the major bioactive compounds present in P. betle leaves; therefore, computational docking of Eugenol-conjugated AgNPs (PbEu-AgNPs) and Hydroxychavicol-conjugated AgNPs (PbHy-AgNPs) against ExoS and ExoY was performed. The active residues of PbEu-AgNPs and PbHy-AgNPs interacted with the active site of ExoS and ExoY exoenzymes. Biofabricated AgNP-mediated inhibition of these virulent exoenzymes blocked the adverse effect of P. aeruginosa on the host cell. The computational analysis provides new approach into the design of biofabricated AgNPs as promising anti-infective nanomedicine agents. Supplementary Information The online version contains supplementary material available at 10.1007/s13205-022-03367-0.
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Affiliation(s)
- Satyam Sangeet
- Microbial Diversity Research Center, Dr. D.Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra India
- Present Address: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, 741246 India
| | - Sarika Pawar
- Microbial Diversity Research Center, Dr. D.Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra India
| | - Neelu Nawani
- Microbial Diversity Research Center, Dr. D.Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra India
| | - Manisha Junnarkar
- Microbial Diversity Research Center, Dr. D.Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra India
| | - Swapnil Gaikwad
- Microbial Diversity Research Center, Dr. D.Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra India
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Smith KP, Lee W, Tonelli M, Lee Y, Light SH, Cornilescu G, Chakravarthy S. Solution structure and dynamics of the mitochondrial-targeted GTPase-activating protein (GAP) VopE by an integrated NMR/SAXS approach. Protein Sci 2022; 31:e4282. [PMID: 35137487 PMCID: PMC9047041 DOI: 10.1002/pro.4282] [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: 09/29/2021] [Revised: 01/17/2022] [Accepted: 01/27/2022] [Indexed: 11/11/2022]
Abstract
The bacterial pathogen Vibrio cholerae use a type III secretion system to inject effector proteins into a host cell. Recently, a putative Toxic GTPase Activating Protein (ToxGAP) called VopE was identified as a T3SS substrate and virulence factor that affected host mitochondrial dynamics and immune response. However, biophysical and structural characterization has been absent. Here, we describe solution NMR structure of the putative GAP domain (73-204) of VopE. Using SEC-SAXS and RDC data, we restrained the MD process to efficiently determine the overall fold and improve the quality of the output calculated structures. Comparing the structure of VopE with other ToxGAP's revealed a similar overall fold with several features unique to VopE. Specifically, the "Bulge 1", α1 helix, and noteworthy "backside linker" elements on the N-terminus are dissimilar to the other ToxGAP's. By using NMR relaxation dispersion experiments, we demonstrate that these regions undergo motions on a >6 s-1 timescale. Based on the disposition of these mobile regions relative to the putative catalytic arginine residue, we hypothesize the protein may undergo structural changes to bind cognate GTPases. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Kyle P Smith
- Current, Xilio Therapeutics, Waltham, MA, USA.,Former, Department of Cell & Developmental Biology, Northwestern University Chicago, IL, USA
| | - Woonghee Lee
- Department of Chemistry, University of Colorado-Denver, Denver, CO, USA
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Yeongjoon Lee
- Department of Chemistry, University of Colorado-Denver, Denver, CO, USA
| | - Samuel H Light
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Gabriel Cornilescu
- Advanced Technology Research Facility, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., National Cancer Institute, National Institutes of Health, Frederick, MD, USA
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Gazi AD, Kokkinidis M, Fadouloglou VE. α-Helices in the Type III Secretion Effectors: A Prevalent Feature with Versatile Roles. Int J Mol Sci 2021; 22:ijms22115412. [PMID: 34063760 PMCID: PMC8196651 DOI: 10.3390/ijms22115412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/14/2021] [Accepted: 05/17/2021] [Indexed: 12/16/2022] Open
Abstract
Type III Secretion Systems (T3SSs) are multicomponent nanomachines located at the cell envelope of Gram-negative bacteria. Their main function is to transport bacterial proteins either extracellularly or directly into the eukaryotic host cell cytoplasm. Type III Secretion effectors (T3SEs), latest to be secreted T3S substrates, are destined to act at the eukaryotic host cell cytoplasm and occasionally at the nucleus, hijacking cellular processes through mimicking eukaryotic proteins. A broad range of functions is attributed to T3SEs, ranging from the manipulation of the host cell's metabolism for the benefit of the bacterium to bypassing the host's defense mechanisms. To perform this broad range of manipulations, T3SEs have evolved numerous novel folds that are compatible with some basic requirements: they should be able to easily unfold, pass through the narrow T3SS channel, and refold to an active form when on the other side. In this review, the various folds of T3SEs are presented with the emphasis placed on the functional and structural importance of α-helices and helical domains.
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Affiliation(s)
- Anastasia D. Gazi
- Unit of Technology & Service Ultrastructural Bio-Imaging (UTechS UBI), Institut Pasteur, 75015 Paris, France
- Correspondence: (A.D.G.); (V.E.F.)
| | - Michael Kokkinidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Nikolaou Plastira 100, Heraklion, 70013 Crete, Greece;
- Department of Biology, Voutes University Campus, University of Crete, Heraklion, 70013 Crete, Greece
| | - Vasiliki E. Fadouloglou
- Department of Molecular Biology & Genetics, Democritus University of Thrace, 68100 Alexandroupolis, Greece
- Correspondence: (A.D.G.); (V.E.F.)
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Giannakou LE, Giannopoulos AS, Hatzoglou C, Gourgoulianis KI, Rouka E, Zarogiannis SG. Investigation and Functional Enrichment Analysis of the Human Host Interaction Network with Common Gram-Negative Respiratory Pathogens Predicts Possible Association with Lung Adenocarcinoma. PATHOPHYSIOLOGY 2021; 28:20-33. [PMID: 35366267 PMCID: PMC8830454 DOI: 10.3390/pathophysiology28010003] [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: 11/09/2020] [Revised: 12/26/2020] [Accepted: 12/27/2020] [Indexed: 11/16/2022] Open
Abstract
Haemophilus influenzae (Hi), Moraxella catarrhalis (MorCa) and Pseudomonas aeruginosa (Psa) are three of the most common gram-negative bacteria responsible for human respiratory diseases. In this study, we aimed to identify, using the functional enrichment analysis (FEA), the human gene interaction network with the aforementioned bacteria in order to elucidate the full spectrum of induced pathogenicity. The Human Pathogen Interaction Database (HPIDB 3.0) was used to identify the human proteins that interact with the three pathogens. FEA was performed via the ToppFun tool of the ToppGene Suite and the GeneCodis database so as to identify enriched gene ontologies (GO) of biological processes (BP), cellular components (CC) and diseases. In total, 11 human proteins were found to interact with the bacterial pathogens. FEA of BP GOs revealed associations with mitochondrial membrane permeability relative to apoptotic pathways. FEA of CC GOs revealed associations with focal adhesion, cell junctions and exosomes. The most significantly enriched annotations in diseases and pathways were lung adenocarcinoma and cell cycle, respectively. Our results suggest that the Hi, MorCa and Psa pathogens could be related to the pathogenesis and/or progression of lung adenocarcinoma via the targeting of the epithelial cellular junctions and the subsequent deregulation of the cell adhesion and apoptotic pathways. These hypotheses should be experimentally validated.
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Affiliation(s)
- Lydia-Eirini Giannakou
- Department of Physiology, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece; (L.-E.G.); (A.-S.G.); (C.H.); (S.G.Z.)
| | - Athanasios-Stefanos Giannopoulos
- Department of Physiology, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece; (L.-E.G.); (A.-S.G.); (C.H.); (S.G.Z.)
| | - Chrissi Hatzoglou
- Department of Physiology, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece; (L.-E.G.); (A.-S.G.); (C.H.); (S.G.Z.)
- Department of Respiratory Medicine, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece;
| | - Konstantinos I. Gourgoulianis
- Department of Respiratory Medicine, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece;
| | - Erasmia Rouka
- Department of Physiology, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece; (L.-E.G.); (A.-S.G.); (C.H.); (S.G.Z.)
- Department of Respiratory Medicine, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece;
- Correspondence:
| | - Sotirios G. Zarogiannis
- Department of Physiology, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece; (L.-E.G.); (A.-S.G.); (C.H.); (S.G.Z.)
- Department of Respiratory Medicine, Faculty of Medicine, School of Health Sciences, University of Thessaly, BIOPOLIS, 41500 Larissa, Greece;
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7
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Arrington ME, Temple B, Schaefer A, Campbell SL. The molecular basis for immune dysregulation by the hyperactivated E62K mutant of the GTPase RAC2. J Biol Chem 2020; 295:12130-12142. [PMID: 32636302 PMCID: PMC7443499 DOI: 10.1074/jbc.ra120.012915] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 07/02/2020] [Indexed: 12/20/2022] Open
Abstract
The RAS-related C3 botulinum toxin substrate 2 (RAC2) is a member of the RHO subclass of RAS superfamily GTPases required for proper immune function. An activating mutation in a key switch II region of RAC2 (RAC2E62K) involved in recognizing modulatory factors and effectors has been identified in patients with common variable immune deficiency. To better understand how the mutation dysregulates RAC2 function, we evaluated the structure and stability, guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) activity, and effector binding of RAC2E62K Our findings indicate the E62K mutation does not alter RAC2 structure or stability. However, it does alter GEF specificity, as RAC2E62K is activated by the DOCK GEF, DOCK2, but not by the Dbl homology GEF, TIAM1, both of which activate the parent protein. Our previous data further showed that the E62K mutation impairs GAP activity for RAC2E62K As this disease mutation is also found in RAS GTPases, we assessed GAP-stimulated GTP hydrolysis for KRAS and observed a similar impairment, suggesting that the mutation plays a conserved role in GAP activation. We also investigated whether the E62K mutation alters effector binding, as activated RAC2 binds effectors to transmit signaling through effector pathways. We find that RAC2E62K retains binding to an NADPH oxidase (NOX2) subunit, p67phox, and to the RAC-binding domain of p21-activated kinase, consistent with our earlier findings. Taken together, our findings indicate that the RAC2E62K mutation promotes immune dysfunction by promoting RAC2 hyperactivation, altering GEF specificity, and impairing GAP function yet retaining key effector interactions.
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Affiliation(s)
- Megan E Arrington
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Brenda Temple
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA; R. L. Juliano Structural Bioinformatics Core Facility, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Antje Schaefer
- Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Sharon L Campbell
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, USA.
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Abstract
Pseudomonas aeruginosa, a versatile Gram-negative pathogen that can cause a wide range of infections, is the most common causative agent in cases of bacterial keratitis associated with contact-lens use. Corneal infections with P. aeruginosa often have poor clinical outcomes and can result in long and costly treatments. During the infection process, the pathogen exploits its large genome, encoding complex regulatory networks and a wide range of virulence factors, including motility and the secretion of various proteases and toxins. Although antibiotic resistance levels in the UK are low, higher levels have been seen in some other countries. In the face of increasing antibiotic resistance, alternative therapeutic approaches such as antivirulence strategies and phage therapy are being developed. There is increasing evidence to suggest that keratitis infections are associated with a phylogenetic subgroup of P. aeruginosa isolates carrying the gene encoding the potent cytotoxin exotoxin U, one of two mutually exclusive exotoxins secreted via the type III secretion system. The mechanisms behind this association are unclear, but understanding the genetic differences that predispose P. aeruginosa to cause corneal infections may allow for the development of targeted and more effective future treatments to reduce the morbidity of P. aeruginosa keratitis. In order to minimize the risk of severe P. aeruginosa eye infections, a wide range of contact-lens disinfection solutions are available. Constant exposure to biocides at a range of concentrations, from sub-inhibitory to inhibitory, could contribute to the development of resistance to both antibiotics and disinfectants.
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Affiliation(s)
- Yasmin Hilliam
- Department of Clinical Infection, Microbiology, and Immunology, Institute of Infection and Global Health, University of Liverpool, Liverpool, L69 7BE, UK
| | - Stephen Kaye
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK
| | - Craig Winstanley
- Department of Clinical Infection, Microbiology, and Immunology, Institute of Infection and Global Health, University of Liverpool, Liverpool, L69 7BE, UK
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Pseudomonas aeruginosa ExsA Regulates a Metalloprotease, ImpA, That Inhibits Phagocytosis of Macrophages. Infect Immun 2019; 87:IAI.00695-19. [PMID: 31527124 DOI: 10.1128/iai.00695-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 02/08/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogenic bacterium whose type III secretion system (T3SS) plays a critical role in acute infections. Translocation of the T3SS effectors into host cells induces cytotoxicity. In addition, the T3SS promotes the intracellular growth of P. aeruginosa during host infections. The T3SS regulon genes are regulated by an AraC-type regulator, ExsA. In this study, we found that an extracellular metalloprotease encoded by impA (PA0572) is under the regulation of ExsA. An ExsA consensus binding sequence was identified upstream of the impA gene, and direct binding of the site by ExsA was demonstrated via an electrophoretic mobility shift assay. We further demonstrate that secreted ImpA cleaves the macrophage surface protein CD44, which inhibits the phagocytosis of the bacterial cells by macrophages. Combined, our results reveal a novel ExsA-regulated virulence factor that cooperatively inhibits the functions of macrophages with the T3SS.
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10
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Bacterial membrane vesicles transport their DNA cargo into host cells. Sci Rep 2017; 7:7072. [PMID: 28765539 PMCID: PMC5539193 DOI: 10.1038/s41598-017-07288-4] [Citation(s) in RCA: 198] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 06/27/2017] [Indexed: 12/25/2022] Open
Abstract
Bacterial outer membrane vesicles (OMVs) are extracellular sacs containing biologically active products, such as proteins, cell wall components and toxins. OMVs are reported to contain DNA, however, little is known about the nature of this DNA, nor whether it can be transported into host cells. Our work demonstrates that chromosomal DNA is packaged into OMVs shed by bacteria during exponential phase. Most of this DNA was present on the external surfaces of OMVs, with smaller amounts located internally. The DNA within the internal compartments of Pseudomonas aeruginosa OMVs were consistently enriched in specific regions of the bacterial chromosome, encoding proteins involved in virulence, stress response, antibiotic resistance and metabolism. Furthermore, we demonstrated that OMVs carry DNA into eukaryotic cells, and this DNA was detectable by PCR in the nuclear fraction of cells. These findings suggest a role for OMV-associated DNA in bacterial-host cell interactions and have implications for OMV-based vaccines.
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11
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Bankapalli LK, Mishra RC, Raychaudhuri S. VopE, a Vibrio cholerae Type III Effector, Attenuates the Activation of CWI-MAPK Pathway in Yeast Model System. Front Cell Infect Microbiol 2017; 7:82. [PMID: 28373966 PMCID: PMC5357651 DOI: 10.3389/fcimb.2017.00082] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 03/02/2017] [Indexed: 01/05/2023] Open
Abstract
VopE, a mitochondrial targeting T3SS effector protein of Vibrio cholerae, perturbs innate immunity by modulating mitochondrial dynamics. In the current study, ectopic expression of VopE was found to be toxic in a yeast model system and toxicity was further aggravated in the presence of various stressors. Interestingly, a VopE variant lacking predicted mitochondrial targeting sequence (MTS) also exhibited partial lethality in the yeast system. With the aid of yeast genetic tools and different stressors, we have demonstrated that VopE and its derivative VopEΔMTS modulate cell wall integrity (CWI-MAPK) signaling pathway and have identified several critical residues contributing to the lethality of VopE. Furthermore, co-expression of two effectors VopEΔMTS and VopX, interfering with the CWI-MAPK cellular pathway can partially suppress the VopX mediated yeast growth inhibition. Taken together, these results suggest that VopE alters signaling through the CWI-MAPK pathway, and demonstrates the usefulness of yeast model system to gain additional insights on the functionality of VopE.
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Affiliation(s)
- Leela K Bankapalli
- Molecular Biology and Microbial Physiology, Institute of Microbial Technology Chandigarh, India
| | - Rahul C Mishra
- Molecular Biology and Microbial Physiology, Institute of Microbial Technology Chandigarh, India
| | - Saumya Raychaudhuri
- Molecular Biology and Microbial Physiology, Institute of Microbial Technology Chandigarh, India
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12
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Amin E, Jaiswal M, Derewenda U, Reis K, Nouri K, Koessmeier KT, Aspenström P, Somlyo AV, Dvorsky R, Ahmadian MR. Deciphering the Molecular and Functional Basis of RHOGAP Family Proteins: A SYSTEMATIC APPROACH TOWARD SELECTIVE INACTIVATION OF RHO FAMILY PROTEINS. J Biol Chem 2016; 291:20353-71. [PMID: 27481945 PMCID: PMC5034035 DOI: 10.1074/jbc.m116.736967] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/15/2016] [Indexed: 12/30/2022] Open
Abstract
RHO GTPase-activating proteins (RHOGAPs) are one of the major classes of regulators of the RHO-related protein family that are crucial in many cellular processes, motility, contractility, growth, differentiation, and development. Using database searches, we extracted 66 distinct human RHOGAPs, from which 57 have a common catalytic domain capable of terminating RHO protein signaling by stimulating the slow intrinsic GTP hydrolysis (GTPase) reaction. The specificity of the majority of the members of RHOGAP family is largely uncharacterized. Here, we comprehensively investigated the sequence-structure-function relationship between RHOGAPs and RHO proteins by combining our in vitro data with in silico data. The activity of 14 representatives of the RHOGAP family toward 12 RHO family proteins was determined in real time. We identified and structurally verified hot spots in the interface between RHOGAPs and RHO proteins as critical determinants for binding and catalysis. We have found that the RHOGAP domain itself is nonselective and in some cases rather inefficient under cell-free conditions. Thus, we propose that other domains of RHOGAPs confer substrate specificity and fine-tune their catalytic efficiency in cells.
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Affiliation(s)
- Ehsan Amin
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Mamta Jaiswal
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Urszula Derewenda
- the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, and
| | - Katarina Reis
- the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Kazem Nouri
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Katja T Koessmeier
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany
| | - Pontus Aspenström
- the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Avril V Somlyo
- the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, and
| | - Radovan Dvorsky
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany,
| | - Mohammad R Ahmadian
- From the Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany,
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13
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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: 47] [Impact Index Per Article: 5.9] [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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14
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Harris RC, Pettitt BM. Examining the assumptions underlying continuum-solvent models. J Chem Theory Comput 2015; 11:4593-600. [PMID: 26574250 DOI: 10.1021/acs.jctc.5b00684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Continuum-solvent models (CSMs) have successfully predicted many quantities, including the solvation-free energies (ΔG) of small molecules, but they have not consistently succeeded at reproducing experimental binding free energies (ΔΔG), especially for protein-protein complexes. Several CSMs break ΔG into the free energy (ΔGvdw) of inserting an uncharged molecule into solution and the free energy (ΔGel) gained from charging. Some further divide ΔGvdw into the free energy (ΔGrep) of inserting a nearly hard cavity into solution and the free energy (ΔGatt) gained from turning on dispersive interactions between the solute and solvent. We show that for 9 protein-protein complexes neither ΔGrep nor ΔGvdw was linear in the solvent-accessible area A, as assumed in many CSMs, and the corresponding components of ΔΔG were not linear in changes in A. We show that linear response theory (LRT) yielded good estimates of ΔGatt and ΔΔGatt, but estimates of ΔΔGatt obtained from either the initial or final configurations of the solvent were not consistent with those from LRT. The LRT estimates of ΔGel differed by more than 100 kcal/mol from the explicit solvent model's (ESM's) predictions, and its estimates of the corresponding component (ΔΔGel) of ΔΔG differed by more than 10 kcal/mol. Finally, the Poisson-Boltzmann equation produced estimates of ΔGel that were correlated with those from the ESM, but its estimates of ΔΔGel were much less so. These findings may help explain why many CSMs have not been consistently successful at predicting ΔΔG for many complexes, including protein-protein complexes.
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Affiliation(s)
- Robert C Harris
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
| | - B Montgomery Pettitt
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
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Wood S, Goldufsky J, Shafikhani SH. Pseudomonas aeruginosa ExoT Induces Atypical Anoikis Apoptosis in Target Host Cells by Transforming Crk Adaptor Protein into a Cytotoxin. PLoS Pathog 2015; 11:e1004934. [PMID: 26020630 PMCID: PMC4447348 DOI: 10.1371/journal.ppat.1004934] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 05/04/2015] [Indexed: 11/19/2022] Open
Abstract
Previously, we demonstrated that Pseudomonas aeruginosa ExoT induces potent apoptosis in host epithelial cells in a manner that primarily depends on its ADP-ribosyltransferase domain (ADPRT) activity. However, the mechanism underlying ExoT/ADPRT-induced apoptosis remains undetermined. We now report that ExoT/ADPRT disrupts focal adhesion sites, activates p38β and JNK, and interferes with integrin-mediated survival signaling; causing atypical anoikis. We show that ExoT/ADPRT-induced anoikis is mediated by the Crk adaptor protein. We found that Crk-/- knockout cells are significantly more resistant to ExoT-induced apoptosis, while Crk-/- cells complemented with Crk are rendered sensitive to ExoT-induced apoptosis. Moreover, a dominant negative (DN) mutant form of Crk phenocopies ExoT-induced apoptosis both kinetically and mechanistically. Crk is generally believed to be a component of focal adhesion (FA) and its role in cellular survival remains controversial in that it has been found to be either pro-survival or pro-apoptosis. Our data demonstrate that although Crk is recruited to FA sites, its function is likely not required for FA assembly or for survival per se. However, when modified by ExoT or by mutagenesis, it can be transformed into a cytotoxin that induces anoikis by disrupting FA sites and interfering with integrin survival signaling. To our knowledge, this is the first example whereby a bacterial toxin exerts its cytotoxicity by subverting the function of an innocuous host cellular protein and turning it against the host cell.
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Affiliation(s)
- Stephen Wood
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Josef Goldufsky
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Sasha H. Shafikhani
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
- Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois, United States of America
- Cancer Center, Rush University Medical Center, Chicago, Illinois, United States of America
- * E-mail:
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The ADP-ribosyltransferase domain of the effector protein ExoS inhibits phagocytosis of Pseudomonas aeruginosa during pneumonia. mBio 2014; 5:e01080-14. [PMID: 24917597 PMCID: PMC4056551 DOI: 10.1128/mbio.01080-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative pathogen commonly associated with nosocomial infections such as hospital-acquired pneumonia. It uses a type III secretion system to deliver effector proteins directly into the cytosol of host cells. Type III secretion in P. aeruginosa has been linked to severe disease and worse clinical outcomes in animal and human studies. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. Numerous in vitro studies have investigated the targets and cellular effects of ExoS, linking both its enzymatic activities with inhibition of bacterial internalization. However, little is known about how this toxin facilitates the progression of infection in vivo. In this study, we used a mouse model to investigate the role of ExoS in inhibiting phagocytosis during pneumonia. We first confirmed previous findings that the ADP-ribosyltransferase activity of ExoS, but not the GTPase-activating protein activity, was responsible for bacterial persistence and decreased host survival in this model. We then used two distinct assays to demonstrate that ExoS inhibited phagocytosis during pneumonia. In contrast to the findings of several in vitro studies, this in vivo inhibition was also dependent on the ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS. These results demonstrate for the first time the antiphagocytic function of ExoS in the context of an actual infection and indicate that blocking the ADP-ribosyltransferase activity of ExoS may have potential therapeutic benefit. Pseudomonas aeruginosa is a major cause of hospital-acquired infections. To cause severe disease, this bacterium uses a type III secretion system that delivers four effector proteins, ExoS, ExoT, ExoU, and ExoY, into host cells. The majority of P. aeruginosa strains secrete ExoS, a bifunctional toxin with GTPase-activating protein and ADP-ribosyltransferase activities. In cell culture models, both enzymatic activities have been associated with decreased bacterial internalization. However, our study is the first to examine a role for ExoS in blocking phagocytosis in an animal model. We report that ExoS does inhibit phagocytosis during pneumonia. The ADP-ribosyltransferase activity, but not the GTPase-activating protein activity, of ExoS is necessary for this effect. Our findings highlight the ability of P. aeruginosa to manipulate the inflammatory response during pneumonia to facilitate bacterial survival.
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Ruhanen H, Hurley D, Ghosh A, O'Brien KT, Johnston CR, Shields DC. Potential of known and short prokaryotic protein motifs as a basis for novel peptide-based antibacterial therapeutics: a computational survey. Front Microbiol 2014; 5:4. [PMID: 24478765 PMCID: PMC3896991 DOI: 10.3389/fmicb.2014.00004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 01/05/2014] [Indexed: 11/13/2022] Open
Abstract
Short linear motifs (SLiMs) are functional stretches of protein sequence that are of crucial importance for numerous biological processes by mediating protein-protein interactions. These motifs often comprise peptides of less than 10 amino acids that modulate protein-protein interactions. While well-characterized in eukaryotic intracellular signaling, their role in prokaryotic signaling is less well-understood. We surveyed the distribution of known motifs in prokaryotic extracellular and virulence proteins across a range of bacterial species and conducted searches for novel motifs in virulence proteins. Many known motifs in virulence effector proteins mimic eukaryotic motifs and enable the pathogen to control the intracellular processes of their hosts. Novel motifs were detected by finding those that had evolved independently in three or more unrelated virulence proteins. The search returned several significantly over-represented linear motifs of which some were known motifs and others are novel candidates with potential roles in bacterial pathogenesis. A putative C-terminal G[AG].$ motif found in type IV secretion system proteins was among the most significant detected. A KK$ motif that has been previously identified in a plasminogen-binding protein, was demonstrated to be enriched across a number of adhesion and lipoproteins. While there is some potential to develop peptide drugs against bacterial infection based on bacterial peptides that mimic host components, this could have unwanted effects on host signaling. Thus, novel SLiMs in virulence factors that do not mimic host components but are crucial for bacterial pathogenesis, such as the type IV secretion system, may be more useful to develop as leads for anti-microbial peptides or drugs.
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Affiliation(s)
- Heini Ruhanen
- Complex and Adaptive Systems Laboratory, University College Dublin Dublin, Ireland ; Conway Institute of Biomolecular and Biomedical Science, University College Dublin Dublin, Ireland ; School of Medicine and Medical Science, University College Dublin Dublin, Ireland
| | - Daniel Hurley
- Complex and Adaptive Systems Laboratory, University College Dublin Dublin, Ireland ; Conway Institute of Biomolecular and Biomedical Science, University College Dublin Dublin, Ireland ; School of Medicine and Medical Science, University College Dublin Dublin, Ireland
| | - Ambarnil Ghosh
- Crystallography and Molecular Biology Department, Saha Institute of Nuclear Physics Kolkata, India
| | - Kevin T O'Brien
- Complex and Adaptive Systems Laboratory, University College Dublin Dublin, Ireland ; Conway Institute of Biomolecular and Biomedical Science, University College Dublin Dublin, Ireland ; School of Medicine and Medical Science, University College Dublin Dublin, Ireland
| | | | - Denis C Shields
- Complex and Adaptive Systems Laboratory, University College Dublin Dublin, Ireland ; Conway Institute of Biomolecular and Biomedical Science, University College Dublin Dublin, Ireland ; School of Medicine and Medical Science, University College Dublin Dublin, Ireland
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Discovery of YopE Inhibitors by Pharmacophore-Based Virtual Screening and Docking. ISRN BIOINFORMATICS 2013; 2013:640518. [PMID: 25937949 PMCID: PMC4393062 DOI: 10.1155/2013/640518] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/28/2013] [Indexed: 01/24/2023]
Abstract
Gram-negative bacteria Yersinia secrete virulence factors that invade eukaryotic cells via type III secretion system. One particular virulence member, Yersinia outer protein E (YopE), targets Rho family of small GTPases by mimicking regulator GAP protein activity, and its secretion mainly induces cytoskeletal disruption and depolymerization of actin stress fibers within the host cell. In this work, potent drug-like inhibitors of YopE are investigated with virtual screening approaches. More than 500,000 unique small molecules from ZINC database were screened with a five-point pharmacophore, comprising three hydrogen acceptors, one hydrogen donor, and one ring, and derived from different salicylidene acylhydrazides. Binding modes and features of these molecules were investigated with a multistep molecular docking approach using Glide software. Virtual screening hits were further analyzed based on their docking score, chemical similarity, pharmacokinetic properties, and the key Arg144 interaction along with other active site residue interactions with the receptor. As a final outcome, a diverse set of ligands with inhibitory potential were proposed.
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19
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Structural basis of eukaryotic cell targeting by type III secretion system (T3SS) effectors. Res Microbiol 2013; 164:605-19. [PMID: 23541478 DOI: 10.1016/j.resmic.2013.03.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/27/2013] [Indexed: 02/06/2023]
Abstract
Type III secretion systems (T3SS) are macromolecular complexes that translocate a wide number of effector proteins into eukaryotic host cells. Once within the cytoplasm, many T3SS effectors mimic the structure and/or function of eukaryotic proteins in order to manipulate signaling cascades, and thus play pivotal roles in colonization, invasion, survival and virulence. Structural biology techniques have played key roles in the unraveling of bacterial strategies employed for mimicry and targeting. This review provides an overall view of our current understanding of structure and function of T3SS effectors, as well as of the different classes of eukaryotic proteins that are targeted and the consequences for the infected cell.
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Guttman C, Davidov G, Shaked H, Kolusheva S, Bitton R, Ganguly A, Miller JF, Chill JH, Zarivach R. Characterization of the N-terminal domain of BteA: a Bordetella type III secreted cytotoxic effector. PLoS One 2013; 8:e55650. [PMID: 23383256 PMCID: PMC3559503 DOI: 10.1371/journal.pone.0055650] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Accepted: 12/28/2012] [Indexed: 12/12/2022] Open
Abstract
BteA, a 69-kDa cytotoxic protein, is a type III secretion system (T3SS) effector in the classical Bordetella, the etiological agents of pertussis and related mammalian respiratory diseases. Currently there is limited information regarding the structure of BteA or its subdomains, and no insight as to the identity of its eukaryotic partners(s) and their modes of interaction with BteA. The mechanisms that lead to BteA dependent cell death also remain elusive. The N-terminal domain of BteA is multifunctional, acting as a docking platform for its cognate chaperone (BtcA) in the bacterium, and targeting the protein to lipid raft microdomains within the eukaryotic host cell. In this study we describe the biochemical and biophysical characteristics of this domain (BteA287) and determine its architecture. We characterize BteA287 as being a soluble and highly stable domain which is rich in alpha helical content. Nuclear magnetic resonance (NMR) experiments combined with size exclusion and analytical ultracentrifugation measurements confirm these observations and reveal BteA287 to be monomeric in nature with a tendency to oligomerize at concentrations above 200 µM. Furthermore, diffusion-NMR demonstrated that the first 31 residues of BteA287 are responsible for the apparent aggregation behavior of BteA287. Light scattering analyses and small angle X-ray scattering experiments reveal a prolate ellipsoidal bi-pyramidal dumb-bell shape. Thus, our biophysical characterization is a first step towards structure determination of the BteA N-terminal domain.
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Affiliation(s)
- Chen Guttman
- Departments of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
- National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Geula Davidov
- Departments of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
- National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Hadassa Shaked
- Department of Chemistry, Bar Ilan University, Ramat Gan, Israel
| | - Sofiya Kolusheva
- Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva, Israel
| | - Ronit Bitton
- Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva, Israel
- Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Atish Ganguly
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jeff F. Miller
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jordan H. Chill
- Department of Chemistry, Bar Ilan University, Ramat Gan, Israel
- * E-mail: (JHC); (RZ)
| | - Raz Zarivach
- Departments of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
- National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva, Israel
- * E-mail: (JHC); (RZ)
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21
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Hu SH, Whitten AE, King GJ, Jones A, Rowland AF, James DE, Martin JL. The weak complex between RhoGAP protein ARHGAP22 and signal regulatory protein 14-3-3 has 1:2 stoichiometry and a single peptide binding mode. PLoS One 2012; 7:e41731. [PMID: 22952583 PMCID: PMC3429473 DOI: 10.1371/journal.pone.0041731] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 06/25/2012] [Indexed: 12/17/2022] Open
Abstract
ARHGAP22 is a RhoGAP protein comprising an N-terminal PH domain, a RhoGAP domain and a C-terminal coiled-coil domain. It has recently been identified as an Akt substrate that binds 14-3-3 proteins in response to treatment with growth factors involved in cell migration. We used a range of biophysical techniques to investigate the weak interaction between 14-3-3 and a truncated form of ARHGAP22 lacking the coiled-coil domain. This weak interaction could be stabilized by chemical cross-linking which we used to show that: a monomer of ARHGAP22 binds a dimer of 14-3-3; the ARHGAP22 PH domain is required for the 14-3-3 interaction; the RhoGAP domain is unlikely to participate in the interaction; Ser16 is the more important of two predicted 14-3-3 binding sites; and, phosphorylation of Ser16 may not be necessary for 14-3-3 interaction under the conditions we used. Small angle X-ray scattering and cross-link information were used to generate solution structures of the isolated proteins and of the cross-linked ARHGAP22:14-3-3 complex, showing that no major rearrangement occurs in either protein upon binding, and supporting a role for the PH domain and N-terminal peptide of ARHGAP22 in the 14-3-3 interaction. Small-angle X-ray scattering measurements of mixtures of ARHGAP22 and 14-3-3 were used to establish that the affinity of the interaction is ∼30 µM.
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Affiliation(s)
- Shu-Hong Hu
- Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland, Australia
| | - Andrew E. Whitten
- Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland, Australia
| | - Gordon J. King
- Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland, Australia
| | - Alun Jones
- Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland, Australia
| | - Alexander F. Rowland
- Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales, Australia
| | - David E. James
- Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales, Australia
| | - Jennifer L. Martin
- Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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Berthier S, Nguyen MVC, Baillet A, Hograindleur MA, Paclet MH, Polack B, Morel F. Molecular interface of S100A8 with cytochrome b558 and NADPH oxidase activation. PLoS One 2012; 7:e40277. [PMID: 22808130 PMCID: PMC3393751 DOI: 10.1371/journal.pone.0040277] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 06/04/2012] [Indexed: 12/18/2022] Open
Abstract
S100A8 and S100A9 are two calcium binding Myeloid Related Proteins, and important mediators of inflammatory diseases. They were recently introduced as partners for phagocyte NADPH oxidase regulation. However, the precise mechanism of their interaction remains elusive. We had for aim (i) to evaluate the impact of S100 proteins on NADPH oxidase activity; (ii) to characterize molecular interaction of either S100A8, S100A9, or S100A8/S100A9 heterocomplex with cytochrome b558; and (iii) to determine the S100A8 consensus site involved in cytochrome b558/S100 interface. Recombinant full length or S100A9-A8 truncated chimera proteins and ExoS-S100 fusion proteins were expressed in E. coli and in P. aeruginosa respectively. Our results showed that S100A8 is the functional partner for NADPH oxidase activation contrary to S100A9, however, the loading with calcium and a combination with phosphorylated S100A9 are essential in vivo. Endogenous S100A9 and S100A8 colocalize in differentiated and PMA stimulated PLB985 cells, with Nox2/gp91phox and p22phox. Recombinant S100A8, loaded with calcium and fused with the first 129 or 54 N-terminal amino acid residues of the P. aeruginosa ExoS toxin, induced a similar oxidase activation in vitro, to the one observed with S100A8 in the presence of S100A9 in vivo. This suggests that S100A8 is the essential component of the S100A9/S100A8 heterocomplex for oxidase activation. In this context, recombinant full-length rS100A9-A8 and rS100A9-A8 truncated 90 chimera proteins as opposed to rS100A9-A8 truncated 86 and rS100A9-A8 truncated 57 chimeras, activate the NADPH oxidase function of purified cytochrome b558 suggesting that the C-terminal region of S100A8 is directly involved in the molecular interface with the hemoprotein. The data point to four strategic 87HEES90 amino acid residues of the S100A8 C-terminal sequence that are involved directly in the molecular interaction with cytochrome b558 and then in the phagocyte NADPH oxidase activation.
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Affiliation(s)
- Sylvie Berthier
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
| | - Minh Vu Chuong Nguyen
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
- * E-mail:
| | - Athan Baillet
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
- Clinic of Rheumatology, Centre Hospitalier Universitaire (CHU), Grenoble, France
| | - Marc-André Hograindleur
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
| | - Marie-Hélène Paclet
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
- « Laboratoire des Enzymes et des Protéines », Centre Hospitalier Universitaire (CHU), Grenoble, France
- « Institut de Biologie et Pathologie », Centre Hospitalier Universitaire (CHU), Grenoble, France
| | - Benoît Polack
- « Institut de Biologie et Pathologie », Centre Hospitalier Universitaire (CHU), Grenoble, France
- Techniques de l’Ingénierie Médicale et de la Complexité–Informatique, Mathématiques et Applications de Grenoble (TIMC-IMAG) Unité Mixte de Recherche (UMR) 5525 Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier UJF, Grenoble, France
| | - Françoise Morel
- Groupe de Recherche et d’Etude du Processus Inflammatoire (GREPI), Laboratoire “Aging Imaging Modeling” (AGIM), Formation de Recherche en évolution (FRE) Centre National de la Recherche Scientifique CNRS 3405, Université Joseph Fourier UJF, Grenoble, France
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23
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Flannagan RS. Burkholderia cenocepacia infection: disruption of phagocyte immune functions through Rho GTPase inactivation. Cell Adh Migr 2012; 6:297-301. [PMID: 22622109 DOI: 10.4161/cam.20487] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Phagocytosis is an important component of innate immunity that contributes to the eradication of infectious microorganisms; however, successful bacterial pathogens often evade different aspects of host immune responses. A common bacterial evasion strategy entails the production of toxins and/or effectors that disrupt normal host cell processes and because of their importance Rho-family GTPases are often targeted. Burkholderia cenocepacia, an opportunistic pathogen that has a propensity to infect cystic fibrosis patients, is an example of a pathogenic bacterium that has only recently been shown to disrupt Rho GTPase function in professional phagocytes. More specifically, B. cenocepacia disrupts Rac and Cdc42 seemingly through perturbation of guanine nucleotide exchange factor function. Inactivation of Rac, Cdc42 and conceivably other Rho GTPases seriously compromises phagocyte function.
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Affiliation(s)
- Ronald S Flannagan
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada.
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24
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Ligeti E, Welti S, Scheffzek K. Inhibition and Termination of Physiological Responses by GTPase Activating Proteins. Physiol Rev 2012; 92:237-72. [DOI: 10.1152/physrev.00045.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Physiological processes are strictly organized in space and time. However, in cell physiology research, more attention is given to the question of space rather than to time. To function as a signal, environmental changes must be restricted in time; they need not only be initiated but also terminated. In this review, we concentrate on the role of one specific protein family involved in biological signal termination. GTPase activating proteins (GAPs) accelerate the endogenously low GTP hydrolysis rate of monomeric guanine nucleotide-binding proteins (GNBPs), limiting thereby their prevalence in the active, GTP-bound form. We discuss cases where defective or excessive GAP activity of specific proteins causes significant alteration in the function of the nervous, endocrine, and hemopoietic systems, or contributes to development of infections and tumors. Biochemical and genetic data as well as observations from human pathology support the notion that GAPs represent vital elements in the spatiotemporal fine tuning of physiological processes.
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Affiliation(s)
- Erzsébet Ligeti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Stefan Welti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Klaus Scheffzek
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
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Recombinant AexU effector protein of Aeromonas veronii bv. sobria disrupts the actin cytoskeleton by downregulation of Rac1 and induces direct cytotoxicity to β4-integrin expressing cell lines. Microb Pathog 2011; 51:454-65. [DOI: 10.1016/j.micpath.2011.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 09/08/2011] [Accepted: 09/15/2011] [Indexed: 12/27/2022]
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26
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Dean P. Functional domains and motifs of bacterial type III effector proteins and their roles in infection. FEMS Microbiol Rev 2011; 35:1100-25. [PMID: 21517912 DOI: 10.1111/j.1574-6976.2011.00271.x] [Citation(s) in RCA: 220] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A key feature of the virulence of many bacterial pathogens is the ability to deliver effector proteins into eukaryotic cells via a dedicated type three secretion system (T3SS). Many bacterial pathogens, including species of Chlamydia, Xanthomonas, Pseudomonas, Ralstonia, Shigella, Salmonella, Escherichia and Yersinia, depend on the T3SS to cause disease. T3SS effectors constitute a large and diverse group of virulence proteins that mimic eukaryotic proteins in structure and function. A salient feature of bacterial effectors is their modular architecture, comprising domains or motifs that confer an array of subversive functions within the eukaryotic cell. These domains/motifs therefore represent a fascinating repertoire of molecular determinants with important roles during infection. This review provides a snapshot of our current understanding of bacterial effector domains and motifs where a defined role in infection has been demonstrated.
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Affiliation(s)
- Paul Dean
- Institute of Cell and Molecular Bioscience, Medical School, University of Newcastle, Newcastle Upon Tyne, UK.
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27
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Songsungthong W, Higgins MC, Rolán HG, Murphy JL, Mecsas J. ROS-inhibitory activity of YopE is required for full virulence of Yersinia in mice. Cell Microbiol 2010; 12:988-1001. [PMID: 20148901 DOI: 10.1111/j.1462-5822.2010.01448.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
YopE, a type III secreted effector of Yersinia, is a GTPase Activating Protein for Rac1 and RhoA whose catalytic activity is critical for virulence. We found that YopE also inhibited reactive oxygen species (ROS) production and inactivated Rac2. How YopE distinguishes among its targets and which specific targets are critical for Yersinia survival in different tissues are unknown. A screen identifying YopE mutants in Yersinia pseudotuberculosis that interact with different Rho GTPases showed that YopE residues at positions 102, 106, 109 and 156 discern among switch I and II regions of Rac1, Rac2 and RhoA. Two mutants, which expressed YopE alleles with different antiphagocytic, ROS-inhibitory and cell-rounding activities, YptbL109A and YptbESptP, were studied in animal infections. Inhibition of both phagocytosis and ROS production were required for splenic colonization, whereas fewer YopE activities were required for Peyer's patch colonization. This study shows that Y. pseudotuberculosis encounters multiple host defences in different tissues and uses distinct YopE activities to disable them.
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Abstract
Bacterial toxins damage the host at the site of bacterial infection or distant from the site. Bacterial toxins can be single proteins or oligomeric protein complexes that are organized with distinct AB structure-function properties. The A domain encodes a catalytic activity. ADP ribosylation of host proteins is the earliest post-translational modification determined to be performed by bacterial toxins; other modifications include glucosylation and proteolysis. Bacterial toxins also catalyze the non-covalent modification of host protein function or can modify host cell properties through direct protein-protein interactions. The B domain includes two functional domains: a receptor-binding domain, which defines the tropism of a toxin for a cell and a translocation domain that delivers the A domain across a lipid bilayer, either on the plasma membrane or the endosome. Bacterial toxins are often characterized based upon the secretion mechanism that delivers the toxin out of the bacterium, termed types I-VII. This review summarizes the major families of bacterial toxins and also describes the specific structure-function properties of the botulinum neurotoxins.
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Affiliation(s)
- James S Henkel
- Medical College of Wisconsin, Department of Microbiology and Molecular Genetics, Milwaukee, WI 53151, USA.
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29
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Abstract
Evolutionary conflicts involving mimicry are found throughout nature. Diverse pathogens produce a range of 'mimics' that resemble host components in both form and function. Such mimics subvert crucial cellular processes, including the cell cycle, apoptosis, cytoskeletal dynamics and immunity. Here, we review the mounting evidence that mimicry of host processes is a highly successful strategy for pathogens. Discriminating mimics can be crucial for host survival, and host factors exist that effectively counteract mimics, using strategies that combine rapid evolution and an unexpected degree of flexibility in protein-protein interactions. Even in these instances, mimicry may alter the evolutionary course of fundamental cellular processes in host organisms.
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30
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Abstract
The Gram-negative bacterium Pseudomonas aeruginosa uses a complex type III secretion apparatus to inject effector proteins into host cells. The configuration of this secretion machinery, the activities of the proteins that are injected by it and the consequences of this process for infection are now being elucidated. This Review summarizes our current knowledge of P. aeruginosa type III secretion, including the secretion and translocation machinery, the regulation of this machinery, and the associated chaperones and effector proteins. The features of this interesting secretion system have important implications for the pathogenesis of P. aeruginosa infections and for other type III secretion systems.
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Affiliation(s)
- Alan R Hauser
- Departments of MicrobiologyImmunology and Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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31
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Lee SH, Taek Han S, Choi SW, Sung SY, You HJ, Ye SK, Chung MH. Inhibition of Rac and Rac-linked functions by 8-oxo-2'-deoxyguanosine in murine macrophages. Free Radic Res 2009; 43:78-84. [PMID: 19358003 DOI: 10.1080/10715760802609432] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Rac is a protein involved in the various functions of macrophages (Mphi), including the production of reactive oxygen species (ROS), phagocytosis, chemotaxis and the secretion of cytokines (such as gamma-INF). This study tested the effects of nucleosides containing 8-oxoguanine(8-hydroxyguanine) such as 8-oxo-2'-guanosine (8-oxoG) or 8-oxo-2'-deoxyguanosine (8-oxodG), on Rac and the above-listed Rac-associated functions of Mphi using mouse peritoneal Mphi (MpMphi). It is reported that 8-oxodG was able to effectively inhibit Rac and the Rac-associated functions of MpMphi. Compared to 8-oxodG, 8-oxoG showed negligible effects. Furthermore, normal nucleosides such as deoxyguanosine (dG), guanosine (G) and adenosine (A) did not exert any effects. These results suggest that 8-oxodG could be used as a potential tool to modulate the functions of Mphi that are intimately related to various pathological processes.
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Affiliation(s)
- Sun-Hye Lee
- Department of Pharmacology, Seoul National University College of Medicine, Seoul, Korea
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32
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Nielsen KH, Chamieh H, Andersen CBF, Fredslund F, Hamborg K, Le Hir H, Andersen GR. Mechanism of ATP turnover inhibition in the EJC. RNA (NEW YORK, N.Y.) 2009; 15:67-75. [PMID: 19033377 PMCID: PMC2612766 DOI: 10.1261/rna.1283109] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The exon junction complex (EJC) is deposited onto spliced mRNAs and is involved in many aspects of mRNA function. We have recently reconstituted and solved the crystal structure of the EJC core made of MAGOH, Y14, the most conserved portion of MLN51, and the DEAD-box ATPase eIF4AIII bound to RNA in the presence of an ATP analog. The heterodimer MAGOH/Y14 inhibits ATP turnover by eIF4AIII, thereby trapping the EJC core onto RNA, but the exact mechanism behind this remains unclear. Here, we present the crystal structure of the EJC core bound to ADP-AIF(3), the first structure of a DEAD-box helicase in the transition-mimicking state during ATP hydrolysis. It reveals a dissociative transition state geometry and suggests that the locking of the EJC onto the RNA by MAGOH/Y14 is not caused by preventing ATP hydrolysis. We further show that ATP can be hydrolyzed inside the EJC, demonstrating that MAGOH/Y14 acts by locking the conformation of the EJC, so that the release of inorganic phosphate, ADP, and RNA is prevented. Unifying features of ATP hydrolysis are revealed by comparison of our structure with the EJC-ADPNP structure and other helicases. The reconstitution of a transition state mimicking complex is not limited to the EJC and eIF4AIII as we were also able to reconstitute the complex Dbp5-RNA-ADP-AlF(3), suggesting that the use of ADP-AlF(3) may be a valuable tool for examining DEAD-box ATPases in general.
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Affiliation(s)
- Klaus H Nielsen
- Department of Molecular Biology, University of Aarhus, DK-8000 Aarhus, Denmark
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33
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Identification of protein interaction partners and protein-protein interaction sites. J Mol Biol 2008; 382:1276-89. [PMID: 18708070 DOI: 10.1016/j.jmb.2008.08.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 07/10/2008] [Accepted: 08/01/2008] [Indexed: 01/10/2023]
Abstract
Rigid-body docking has become quite successful in predicting the correct conformations of binary protein complexes, at least when the constituent proteins do not undergo large conformational changes upon binding. However, determining whether two given proteins interact is a more difficult problem. Successful docking procedures often give equally good scores for proteins that do not interact experimentally. This is the case for the multiple minimization approach we use here. An analysis of the results where all proteins within a set are docked with all other proteins (complete cross-docking) shows that the predictions can be greatly improved if the location of the correct binding interface on each protein is known, since the experimental complexes are much more likely to bring these two interfaces into contact, at the same time as yielding good interaction energy scores. While various methods exist for identifying binding interfaces, it is shown that simply studying the interaction of all potential protein pairs within a data set can itself help to identify the correct interfaces.
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34
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Pielage JF, Powell KR, Kalman D, Engel JN. RNAi screen reveals an Abl kinase-dependent host cell pathway involved in Pseudomonas aeruginosa internalization. PLoS Pathog 2008; 4:e1000031. [PMID: 18369477 PMCID: PMC2265438 DOI: 10.1371/journal.ppat.1000031] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 02/21/2008] [Indexed: 01/13/2023] Open
Abstract
Internalization of the pathogenic bacterium Pseudomonas aeruginosa by non-phagocytic cells is promoted by rearrangements of the actin cytoskeleton, but the host pathways usurped by this bacterium are not clearly understood. We used RNAi-mediated gene inactivation of ∼80 genes known to regulate the actin cytoskeleton in Drosophila S2 cells to identify host molecules essential for entry of P. aeruginosa. This work revealed Abl tyrosine kinase, the adaptor protein Crk, the small GTPases Rac1 and Cdc42, and p21-activated kinase as components of a host signaling pathway that leads to internalization of P. aeruginosa. Using a variety of complementary approaches, we validated the role of this pathway in mammalian cells. Remarkably, ExoS and ExoT, type III secreted toxins of P. aeruginosa, target this pathway by interfering with GTPase function and, in the case of ExoT, by abrogating P. aeruginosa–induced Abl-dependent Crk phosphorylation. Altogether, this work reveals that P. aeruginosa utilizes the Abl pathway for entering host cells and reveals unexpected complexity by which the P. aeruginosa type III secretion system modulates this internalization pathway. Our results furthermore demonstrate the applicability of using RNAi screens to identify host signaling cascades usurped by microbial pathogens that may be potential targets for novel therapies directed against treatment of antibiotic-resistant infections. Mortality from Pseudomonas aeruginosa infections, one of the leading causes of hospital acquired infections, approaches 40%, and multiple drug resistant infections are common and increasing. Internalization of P. aeruginosa by the host cell appears to play a fundamental role in the pathogenesis of this opportunistic bacterium, but the host cell factors involved in this process are incompletely understood. We used a targeted RNAi screen in Drosophila S2 cells to identify a subset of regulators of the host actin cytoskeleton that contribute to bacterial entry and confirmed their involvement in infection of mammalian cells. We found that P. aeruginosa can modulate this internalization pathway in a complex manner by injecting the bacterial toxins ExoS and ExoT into the host cell via its type III secretion system. The identified host cell molecules may serve as targets for novel drugs to treat infections resistant to conventional antibiotics and may be applicable to a wide range of pathogens.
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Affiliation(s)
- Julia F. Pielage
- Program in Microbial Pathogenesis and Host Defense, University of California San Francisco, San Francisco, California, United States of America
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Department of Microbiology & Immunology, University of California San Francisco, San Francisco, California, United States of America
| | - Kimberly R. Powell
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Daniel Kalman
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Joanne N. Engel
- Program in Microbial Pathogenesis and Host Defense, University of California San Francisco, San Francisco, California, United States of America
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Department of Microbiology & Immunology, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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35
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Abstract
Bacterial pathogens utilize toxins to modify or kill host cells. The bacterial ADP-ribosyltransferases are a family of protein toxins that covalently transfer the ADP-ribose portion of NAD to host proteins. Each bacterial ADP-ribosyltransferase toxin modifies a specific host protein(s) that yields a unique pathology. These toxins possess the capacity to enter a host cell or to use a bacterial Type III apparatus for delivery into the host cell. Advances in our understanding of bacterial toxin action parallel the development of biophysical and structural biology as well as our understanding of the mammalian cell. Bacterial toxins have been utilized as vaccines, as tools to dissect host cell physiology, and more recently for the development of novel therapies to treat human disease.
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Affiliation(s)
- Qing Deng
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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36
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Colinet D, Schmitz A, Depoix D, Crochard D, Poirié M. Convergent use of RhoGAP toxins by eukaryotic parasites and bacterial pathogens. PLoS Pathog 2007; 3:e203. [PMID: 18166080 PMCID: PMC2156102 DOI: 10.1371/journal.ppat.0030203] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Accepted: 11/15/2007] [Indexed: 01/14/2023] Open
Abstract
Inactivation of host Rho GTPases is a widespread strategy employed by bacterial pathogens to manipulate mammalian cellular functions and avoid immune defenses. Some bacterial toxins mimic eukaryotic Rho GTPase-activating proteins (GAPs) to inactivate mammalian GTPases, probably as a result of evolutionary convergence. An intriguing question remains whether eukaryotic pathogens or parasites may use endogenous GAPs as immune-suppressive toxins to target the same key genes as bacterial pathogens. Interestingly, a RhoGAP domain-containing protein, LbGAP, was recently characterized from the parasitoid wasp Leptopilina boulardi, and shown to protect parasitoid eggs from the immune response of Drosophila host larvae. We demonstrate here that LbGAP has structural characteristics of eukaryotic RhoGAPs but that it acts similarly to bacterial RhoGAP toxins in mammals. First, we show by immunocytochemistry that LbGAP enters Drosophila immune cells, plasmatocytes and lamellocytes, and that morphological changes in lamellocytes are correlated with the quantity of LbGAP they contain. Demonstration that LbGAP displays a GAP activity and specifically interacts with the active, GTP-bound form of the two Drosophila Rho GTPases Rac1 and Rac2, both required for successful encapsulation of Leptopilina eggs, was then achieved using biochemical tests, yeast two-hybrid analysis, and GST pull-down assays. In addition, we show that the overall structure of LbGAP is similar to that of eukaryotic RhoGAP domains, and we identify distinct residues involved in its interaction with Rac GTPases. Altogether, these results show that eukaryotic parasites can use endogenous RhoGAPs as virulence factors and that despite their differences in sequence and structure, eukaryotic and bacterial RhoGAP toxins are similarly used to target the same immune pathways in insects and mammals.
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Affiliation(s)
- Dominique Colinet
- UMR 1112 UNSA-INRA Résponses des Organismes aux Stress Environnementaux, Sophia-Antipolis, France
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37
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Choi S, Choi HH, Lee SH, Ko SH, You HJ, Ye SK, Chung MH. Anti-inflammatory effects of 8-hydroxy-2'-deoxyguanosine on lipopolysaccharide-induced inflammation via Rac suppression in Balb/c mice. Free Radic Biol Med 2007; 43:1594-603. [PMID: 18037125 DOI: 10.1016/j.freeradbiomed.2007.08.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Revised: 08/18/2007] [Accepted: 08/20/2007] [Indexed: 01/03/2023]
Abstract
Recently, we observed that 8-hydroxyguanosine triphosphate and 8-hydroxy-2'-deoxyguanosine (oh(8)dG) inactivate Rac and consequently down-regulate the Rac-linked NADPH oxidase, iNOS, and Cox2. Based on these observations, we tested whether oh(8)dG has anti-inflammatory activity in vivo in lipopolysaccharide (LPS)-treated mice. LPS (1 mg/kg, ip)-treated mice exhibit marked inflammatory responses, including increases in proinflammatory cytokines (TNF-alpha, IL-6, IL-18, and IL-12p70) in serum and infiltration of neutrophils, increased translocation of NF-kappaB p50 from the cytosol to the nucleus, and phosphorylation of c-Jun in lung tissues. Mice were pretreated with oh(8)dG (up to 60 mg/kg, ip) 4 h before LPS injection, and this pretreatment dose-dependently inhibited the inflammatory responses; the inhibitions observed with 60 mg/kg oh(8)dG were statistically significant. At the same time, oh(8)dG pretreatment inactivated Rac in lung tissues. Oh(8)dG pretreatment (50 mg/kg, ip) also significantly protected against LPS-induced septic death. Furthermore, oh(8)dG was more effective than acetyl salicylic acid in inhibiting these inflammatory responses. 8-Hydroxyguanosine also had some effect but was much weaker than oh(8)dG. The effects of normal nucleosides (dG, G, and A) were negligible or not significant. These results support an anti-inflammatory activity for oh(8)dG, which could be ascribed to its Rac-inactivating action.
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Affiliation(s)
- Seongwon Choi
- Department of Pharmacology, Seoul National University College of Medicine, Seoul 110-799, Korea
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38
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Zhang Y, Deng Q, Porath JA, Williams CL, Pederson-Gulrud KJ, Barbieri JT. Plasma membrane localization affects the RhoGAP specificity ofPseudomonasExoS. Cell Microbiol 2007; 9:2192-201. [PMID: 17490406 DOI: 10.1111/j.1462-5822.2007.00949.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pseudomonas aeruginosa ExoS (453 amino acids) is a bifunctional type III cytotoxin, comprising a Rho GTPase-activating protein domain (RhoGAP), and a 14-3-3 dependent ADP-ribosyltransferase domain. In addition, ExoS contains a membrane localization domain (termed MLD, residues 51-77) which localizes and traffics ExoS within intoxicated host cells. While membrane localization has been shown to be essential for ExoS to ADP-ribosylate Ras, the relationship between intracellular localization and expression of RhoGAP activity has not been addressed. In this study, loss of MLD function was observed to abolish expression of ExoS RhoGAP activity in HeLa cells. One mutation within the MLD (R56, R63, D70 mutated to N, RRD-->N) diminished plasma membrane localization and altered the cell rounding phenotype elicited by ExoS RhoGAP. In addition, cell rounding caused by ExoS-MLD(RRD-->N) was reversed by dominant active Rac1, but not dominant active Cdc42, indicating a switch in ExoS RhoGAP substrate specificity. Mutation of the C-terminal polybasic region abolished the ability of dominant active Rac1 to protect HeLa cells from expression of the RhoGAP activity of ExoS-MLD(RRD-->N). This study shows the importance of membrane localization in the targeting of Rho GTPases by ExoS RhoGAP.
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Affiliation(s)
- Yue Zhang
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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39
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Brandt S, Shafikhani S, Balachandran P, Jin S, Hartig R, König W, Engel J, Backert S. Use of a novel coinfection system reveals a role for Rac1, H-Ras, and CrkII phosphorylation in Helicobacter pylori-induced host cell actin cytoskeletal rearrangements. ACTA ACUST UNITED AC 2007; 50:190-205. [PMID: 17428306 DOI: 10.1111/j.1574-695x.2007.00234.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Helicobacter pylori CagA protein induces profound morphological changes in the host cytoskeleton and cell scattering, but the signalling involved is poorly understood. Pseudomonas aeruginosa also affects host actin cytoskeleton in a variety of ways by injecting the ExoS and ExoT toxins which encode N-terminal GTPase activating protein and C-terminal ADP-ribosyltransferase (ADPRT) activities. In this study we developed a novel coinfection assay to gain new insights into CagA effector protein functions. We found that P. aeruginosa injecting either ExoT or ExoS efficiently prevented the H. pylori-induced scattering phenotype. Both the Rho-GAP and the ADPRT domains of ExoS were needed to block the H. pylori-induced actin cytoskeletal rearrangements, whereas either domain of ExoT was sufficient for this activity. This strategy revealed common pathways subverted by different pathogens, and aided in the definition of signalling cascades that control the CagA-mediated cell scattering and elongation. We identified Crk adapter proteins, Rac1 and H-Ras, but not RhoA or Cdc42, which are the ExoS and/or ExoT targets, as crucial components of the CagA-induced phenotype. In addition, we show that ADP-ribosylation of CrkII by ExoT blocks phosphorylation of CrkII at Y-221, which is also important for the CagA-induced signalling.
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Affiliation(s)
- Sabine Brandt
- Department of Medical Microbiology, Otto von Guericke University, Magdeburg, Germany
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40
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Reddick LE, Vaughn MD, Wright SJ, Campbell IM, Bruce BD. In vitro comparative kinetic analysis of the chloroplast Toc GTPases. J Biol Chem 2007; 282:11410-26. [PMID: 17261588 DOI: 10.1074/jbc.m609491200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A unique aspect of protein transport into plastids is the coordinate involvement of two GTPases in the translocon of the outer chloroplast membrane (Toc). There are two subfamilies in Arabidopsis, the small GTPases (Toc33 and Toc34) and the large acidic GTPases (Toc90, Toc120, Toc132, and Toc159). In chloroplasts, Toc34 and Toc159 are implicated in precursor binding, yet mechanistic details are poorly understood. How the GTPase cycle is modulated by precursor binding is complex and in need of careful dissection. To this end, we have developed novel in vitro assays to quantitate nucleotide binding and hydrolysis of the Toc GTPases. Here we present the first systematic kinetic characterization of four Toc GTPases (cytosolic domains of atToc33, atToc34, psToc34, and the GTPase domain of atToc159) to permit their direct comparison. We report the KM, Vmax, and Ea values for GTP hydrolysis and the Kd value for nucleotide binding for each protein. We demonstrate that GTP hydrolysis by psToc34 is stimulated by chloroplast transit peptides; however, this activity is not stimulated by homodimerization and is abolished by the R133A mutation. Furthermore, we show peptide stimulation of hydrolytic rates are not because of accelerated nucleotide exchange, indicating that transit peptides function as GTPase-activating proteins and not guanine nucleotide exchange factors in modulating the activity of psToc34. Finally, by using the psToc34 structure, we have developed molecular models for atToc33, atToc34, and atToc159G. By combining these models with the measured enzymatic properties of the Toc GTPases, we provide new insights of how the chloroplast protein import cycle may be regulated.
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Affiliation(s)
- L Evan Reddick
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville 37996, USA
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41
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Galán JE, Wolf-Watz H. Protein delivery into eukaryotic cells by type III secretion machines. Nature 2007; 444:567-73. [PMID: 17136086 DOI: 10.1038/nature05272] [Citation(s) in RCA: 757] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacteria that have sustained long-standing close associations with eukaryotic hosts have evolved specific adaptations to survive and replicate in this environment. Perhaps one of the most remarkable of those adaptations is the type III secretion system (T3SS)--a bacterial organelle that has specifically evolved to deliver bacterial proteins into eukaryotic cells. Although originally identified in a handful of pathogenic bacteria, T3SSs are encoded by a large number of bacterial species that are symbiotic or pathogenic for humans, other animals including insects or nematodes, and plants. The study of these systems is leading to unique insights into not only organelle assembly and protein secretion but also mechanisms of symbiosis and pathogenesis.
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Affiliation(s)
- Jorge E Galán
- Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, Connecticut 0636, USA.
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42
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Mishra R, Gara SK, Mishra S, Prakash B. Analysis of GTPases carrying hydrophobic amino acid substitutions in lieu of the catalytic glutamine: implications for GTP hydrolysis. Proteins 2006; 59:332-8. [PMID: 15726588 DOI: 10.1002/prot.20413] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ras superfamily GTP-binding proteins regulate important signaling events in the cell. Ras, which often serves as a prototype, efficiently hydrolyzes GTP in conjunction with its regulator GAP. A conserved glutamine plays a vital role in GTP hydrolysis in most GTP-binding proteins. Mutating this glutamine in Ras has oncogenic effects, since it disrupts GTP hydrolysis. The analysis presented here is of GTP-binding proteins that are a paradox to oncogenic Ras, since they have the catalytic glutamine (Glncat) substituted by a hydrophobic amino acid, yet can hydrolyze GTP efficiently. We term these proteins HAS-GTPases. Analysis of the amino acid sequences of HAS-GTPases reveals prominent presence of insertions around the GTP-binding pocket. Homology modeling studies suggest an interesting means to achieve catalysis despite the drastic hydrophobic substitution replacing the key Glncat of Ras-like GTPases. The substituted hydrophobic residue adopts a "retracted conformation," where it is positioned away from the GTP, as its role in catalysis would be unproductive. This conformation is further stabilized by interactions with hydrophobic residues in its vicinity. These interacting residues are strongly conserved and hydrophobic in all HAS-GTPases, and correspond to residues Asp92 and Tyr96 of Ras. An experimental support for the "retracted conformation" of Switch II arises from the crystal structures of Ylqf and hGBP1. This conformation allows us to hypothesize that, unlike in classical GTPases, catalytic residues could be supplied by regions other than the Switch II (i.e., either the insertions or a neighboring domain).
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Affiliation(s)
- Rajeev Mishra
- Bioinformatics Center, School of Information Technology, Jawaharlal Nehru University, New Delhi, India
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43
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Abstract
Bacterial pathogens achieve the internalization of a multitude of virulence factors into eukaryotic cells. Some secrete extracellular toxins which bring about their own entry, usually by hijacking cell surface receptors and endocytic pathways. Others possess specialized secretion and translocation systems to directly inject bacterial proteins into the host cytosol. Recent advances in the structural biology of these virulence factors has begun to reveal at the molecular level how these bacterial proteins are delivered and modulate host activities ranging from cytoskeletal structure to cell cycle progression.
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Affiliation(s)
- C Erec Stebbins
- Laboratory of Structural Microbiology, Rockefeller University, New York, NY 10021, USA.
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44
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Wittinghofer A. Phosphoryl transfer in Ras proteins, conclusive or elusive? Trends Biochem Sci 2005; 31:20-3. [PMID: 16356724 DOI: 10.1016/j.tibs.2005.11.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Revised: 11/02/2005] [Accepted: 11/25/2005] [Indexed: 01/17/2023]
Abstract
The chemical mechanism of GTP hydrolysis by GTP-binding proteins of the Ras superfamily continues to inspire both experimental and computational biologists. The debate centres on the nature of the transition state, with arguments for both dissociative and associative, and whether there is a common GTPase mechanism for these proteins. In a recent structural analysis of Rab11, the product P(i) was found in an unusual configuration. This finding indicates that substrate-assisted catalysis might operate as a mechanism to enable nucleophilic attack in the intrinsic GTPase reaction, and would thus favour a pentavalent phosphorane intermediate. Recent findings on the GAP-mediated reaction of different Ras proteins suggest that a common mechanism might not exist and that G proteins probably show a continuum of electronic configurations in the transition state.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
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45
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Baldwin MR, Barbieri JT. The type III cytotoxins of Yersinia and Pseudomonas aeruginosa that modulate the actin cytoskeleton. Curr Top Microbiol Immunol 2005; 291:147-66. [PMID: 15984080 DOI: 10.1007/3-540-27511-8_8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Initial studies of how bacterial toxins modulate the actin cytoskeleton have focused primarily on the mode of action of these toxins. More recently, studies have addressed the molecular interactions of these toxins with host cell signaling pathways and how toxins modulate cellular physiology. Although each individual toxin has a unique mode of action, general themes have started to emerge between bacterial pathogens. During the course of an infection, many pathogenic bacteria produce toxins that target the actin cytoskeleton and its regulatory proteins. Toxins can either act as positive regulators promoting the assembly of filamentous actin structures or, alternatively, as negative regulators promoting actin filament disassembly. Modulation of the actin cytoskeleton facilitates various infectious processes critical for the success of the pathogen. Intracellular bacteria such as Salmonella typhimurium utilize toxins to promote both assembly and disassembly of the actin cytoskeleton during the infection process. Temporal regulation of toxin activities results in internalization of the bacterium by epithelial cells into specialized vacuoles permissive for growth. In contrast, Yersinia utilizes actin modulating toxins to block internalization by professional antigen-presenting cells such as macrophages and dendritic cells. Modulation of the immune response through the production of actin-regulating toxins appears to be a common approach adopted by several extracellular pathogens. Thus the repertoire of actin-modifying toxins produced by various species is specifically tailored to facilitate the lifestyle of the pathogen. The presence of multiple toxins that modulate the activation state of actin shows the importance of interfering with the cytoskeleton to neutralize the host's innate immune system for the survival and growth of Yersinia and P. aeruginosa.
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Affiliation(s)
- M R Baldwin
- Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53225, USA
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46
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Abstract
Recent structural analysis of crystalline beta2-chimaerin shows the central protein kinase C-like, diacylglycerol (DAG)-binding C1 domain to be masked by its intramolecular interactions with the N-terminal SH2 and GAP domains, and linker regions. A mechanism of activation has been derived from modelling of a GAP-Rac GTPase complex--the auto-inhibitory constraints are released via membrane engagement, unmasking the C1 domain to enable DAG binding and subsequent GAP stimulation of Rac GTPase catalytic activity.
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Affiliation(s)
- Christine Hall
- Department of Molecular Neuroscience, Institute of Neurology, University College London, 1 Wakefield Street, London WC1N 1PJ, UK
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47
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Rocha CL, Rucks EA, Vincent DM, Olson JC. Examination of the coordinate effects of Pseudomonas aeruginosa ExoS on Rac1. Infect Immun 2005; 73:5458-67. [PMID: 16113262 PMCID: PMC1231149 DOI: 10.1128/iai.73.9.5458-5467.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Revised: 02/01/2005] [Accepted: 05/09/2005] [Indexed: 11/20/2022] Open
Abstract
Exoenzyme S (ExoS) is a bifunctional toxin directly translocated into eukaryotic cells by the Pseudomonas aeruginosa type III secretory (TTS) process. The amino-terminal GTPase-activating (GAP) activity and the carboxy-terminal ADP-ribosyltransferase (ADPRT) activity of ExoS have been found to target but exert opposite effects on the same low-molecular-weight G protein, Rac1. ExoS ADP-ribosylation of Rac1 is cell line dependent. In HT-29 human epithelial cells, where Rac1 is ADP-ribosylated by TTS-ExoS, Rac1 was activated and relocalized to the membrane fraction. Arg66 and Arg68 within the GTPase-binding region of Rac1 were identified as preferred sites of ExoS ADP-ribosylation. The modification of these residues by ExoS would be predicted to interfere with Rac1 inactivation and explain the increase in active Rac1 caused by ExoS ADPRT activity. Using ExoS-GAP and ADPRT mutants to examine the coordinate effects of the two domains on Rac1 function, limited effects of ExoS-GAP on Rac1 inactivation were evident in HT-29 cells. In J774A.1 macrophages, where Rac1 was not ADP-ribosylated, ExoS caused a decrease in the levels of active Rac1, and this decrease was linked to ExoS-GAP. Using immunofluorescence staining of Rac1 to understand the cellular basis for the targeting of ExoS ADPRT activity to Rac1, an inverse relationship was observed between Rac1 plasma membrane localization and Rac1 ADP-ribosylation. The results obtained from these studies have allowed the development of a model to explain the differential targeting and coordinate effects of ExoS GAP and ADPRT activity on Rac1 within the host cell.
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Affiliation(s)
- Claudia L Rocha
- Department of Microbiology, Immunology and Cell Biology, Robert C. Byrd Health Sciences Center, PO Box 9177, West Virginia University, Morgantown, WV 26506-9177, USA
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48
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Dvorsky R, Ahmadian MR. Always look on the bright site of Rho: structural implications for a conserved intermolecular interface. EMBO Rep 2005; 5:1130-6. [PMID: 15577926 PMCID: PMC1299188 DOI: 10.1038/sj.embor.7400293] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Accepted: 10/08/2004] [Indexed: 01/30/2023] Open
Abstract
The signalling functions of Rho-family GTPases are based on the formation of distinctive protein-protein complexes. Invaluable insights into the structure-function relationships of the Rho GTPases have been obtained through the resolution of several of their structures in complex with regulators and downstream effectors. In this review, we use these complexes to compare the binding and specificity-determining sites of the Rho GTPases. Although the properties that characterize these sites are diverse, some fundamental conserved principles that govern their intermolecular interactions have emerged. Notably, all of the interacting partners of the Rho GTPases, irrespective of their function, bind to a common set of conserved amino acids that are clustered on the surface of the switch regions. This conserved region and its specific structural characteristics exemplify the convergence of the Rho GTPases on a consensus binding site.
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Affiliation(s)
- Radovan Dvorsky
- Department of Structural Biology, Max Planck Institute for Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Mohammad Reza Ahmadian
- Department of Structural Biology, Max Planck Institute for Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
- Tel: +49 231 133 2105; Fax: +49 231 133 2199;
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49
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Vance RE, Rietsch A, Mekalanos JJ. Role of the type III secreted exoenzymes S, T, and Y in systemic spread of Pseudomonas aeruginosa PAO1 in vivo. Infect Immun 2005; 73:1706-13. [PMID: 15731071 PMCID: PMC1064930 DOI: 10.1128/iai.73.3.1706-1713.2005] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Pseudomonas aeruginosa uses a dedicated type III secretion system to deliver toxins directly into the cytoplasm of host cells. While progress has been made in elucidating the function of type III-secreted toxins in vitro, the in vivo functions of the type III-secreted exoenzymes are less well understood, particularly for the sequenced strain PAO1. Therefore, we have systematically deleted the genes for the three known type III effector molecules (exoS, exoT, and exoY) in P. aeruginosa PAO1 and assayed the effect of the deletions, both singly and in combination, on cytotoxicity in vitro and in vivo. We found that the type III secretion system acts differently on different cell types, causing an exoST-dependent rounding of a lung epithelial-like cell line in contrast to causing an exoSTY-independent but translocase (popB)-dependent lysis of a macrophage cell line. We utilized an in vivo competitive infection model to test each of our mutants, examining replication in the lung and spread to secondary sites such as the blood and spleen. Type III mutants inoculated intranasally exhibited only a minor defect in replication and survival in the lung, but popB and exoSTY triple mutants were profoundly defective in their ability to spread systemically. Intravenous injection of the mutants indicated that the type III secretion machinery is required for survival in the blood. Furthermore, our findings suggest that the effector-independent popB-dependent cytotoxicity that we and others have observed in vitro in macrophage cell lines may not be of great importance in vivo.
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Affiliation(s)
- Russell E Vance
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
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50
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Wulf J, Pascuzzi PE, Fahmy A, Martin GB, Nicholson LK. The solution structure of type III effector protein AvrPto reveals conformational and dynamic features important for plant pathogenesis. Structure 2005; 12:1257-68. [PMID: 15242602 DOI: 10.1016/j.str.2004.04.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2004] [Revised: 04/28/2004] [Accepted: 04/28/2004] [Indexed: 12/01/2022]
Abstract
Pseudomonas syringae pv. tomato, the causative agent of bacterial speck disease of tomato, uses a type III secretion system (TTSS) to deliver effector proteins into the host cell. In resistant plants, the bacterial effector protein AvrPto physically interacts with the host Pto kinase and elicits antibacterial defense responses. In susceptible plants, which lack the Pto kinase, AvrPto acts as a virulence factor to promote bacterial growth. The solution structure of AvrPto reveals a functional core consisting of a three-helix bundle motif flanked by disordered N- and C-terminal tails. Residues required for Pto binding lie in a 19 residue Omega loop. Modeling suggests a hydrophobic patch involving the activation loop of Pto forms a contact surface with the AvrPto Omega loop and that helix packing mediates interactions between AvrPto and putative virulence targets Api2 and Api3. The AvrPto structure has a low stability that may facilitate chaperone-independent secretion by the TTSS.
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Affiliation(s)
- Jennifer Wulf
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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