Figure 1: attaching and
effacing (A/E) lesions caused
Translocated T3SS effectors of EPEC/EHEC, Shigella and Salmonella
The subversion of host cell processes by microbial pathogens is an intrinsic part of the host-pathogen interaction. Many bacterial pathogens have the ability to transport virulence proteins, termed effector proteins, into host cells via specialized protein secretion systems. Bacterial effectors have been identified that interfere with, among other things, actin filament dynamics, microtubule function, cytoskeletal organization and host cell GTPase function. We work on a range of virulence effectors that are translocated into cells by the LEE-encoded type III secretion system. We recently identified NleE, NleB and NleC as translocated effectors that interfere with the host innate immune signaling. Homologues of NleE and NleB are also found in Shigella and Salmonella respectively. The aim of this work is to investigate the manipulation of host cell processes by effector protein families to understand their influence on host cell function, inflammatory signaling and the immune response.
Translocated Dot/Icm effectors of Legionella
Figure 2: Transmission
electron micrograph of
Legionella pneumophila is the major cause of Legionnaire’s Disease, an acute form of pneumonia. The bacterial genome encodes around 300 proteins that are translocated into eukaryotic cells by the Dot/Icm type IV secretion system. Many of the effector proteins comprise families of paralogues and the function of the vast majority of these proteins is unknown. Many effectors also share similarity with eukaryotic proteins and these are predicted to allow L. pneumophila to manipulate host cell processes by functional mimicry of eukaryotic proteins. Our goal is to identify the biochemical function of Dot/Icm effector proteins by using biological screens to identify host cell interacting partners and eukaryotic organelles, processes and signaling pathways that are affected by the activity of the bacterial protein. Ultimately this will allow us to understand the molecular mechanisms by which strains of Legionella replicate in the human lung and cause disease.
Immune responses in Legionnaire’s disease
Infection with L. pneumophila elicits a strong inflammatory response in the lung. This initial inflammation is important for subsequent recruitment and activation of immune responses necessary to control and clear the infection. We have discovered that plasmacytoid dendritic cells (pDC) play a role in limiting bacterial replication in the lung. The aim of this work is to understand the mechanisms by which pDC contribute to resistance to infection with Legionella and other bacterial pathogens. This work will not only contribute to our understanding of the pathogenesis of Legionnaire’s disease but will also provide novel information on the functions of pDC.
Mucosal immune responses during bacterial diarrhoea
Susceptibility to gastrointestinal pathogens is the result of complex interplay between bacterial and host factors. Attaching and effacing pathogens interfere with inflammatory and cell death signalling to overcome the host response. At the same time, multiple immune receptors attempt to activate the host response. We have discovered that cell death pathways in particular play a critical role in clearing bacterial infection and eliciting a productive immune response. We are using mice deficient in certain cell death signalling proteins and a mouse specific attaching and effacing pathogen to understand which host factors play a critical role in fighting bacterial diarrhoea.
Intracellular replication of Coxiella burnetii (led by Dr Hayley Newton)
Figure 3: The large Coxiella-containing
vacuole (*) and an effector (green) that is
translocated into the host and recruited to
Coxiella burnetii is a category B bioterrorism agent and the cause of the human disease Q fever. C. burnetii is an intracellular pathogen that replicates to very high numbers within a specialized vacuole derived from host lysosomes. C. burnetii encodes a Dot/Icm type IV secretion system that is essential for intracellular replication. Our research focuses on characterizing the biochemical functions and relative importance of effector proteins of this system. Together, this cohort of ~70 effectors facilitate the rapid expansion and fusogenicity of the Coxiella-containing vacuole and provide the environment required for bacterial replication while blocking host cell death signalling. We aim to understand how these unique bacterial proteins manipulate various aspects of eukaryotic cell biology to benefit the bacterium.
email: Professor Elizabeth Hartland
Dr Ralf Schuelein, NHMRC Postdoctoral Research Officer
Dr Sabrina Muehlen, NHMRC Postdoctoral Research Officer
Dr Tina Creuzburg, DFG Fellow
Dr Catherine Kennedy, ARC DECRA Fellow
Dr Hayley Newton, NHMRC Australian Training Fellow
Dr Patrice Riedmaier, ARC Research Officer
Dr Yogitha Srikhanta, NHMRC Australian Training Fellow
Ms Clare Oates, NHMRC Research Assistant
Ms Vicki Bennett-Wood, NHMRC Research Assistant
Ms Jaclyn Pearson, NHMRC Research Assistant
Ms Sze Ying Ong, PhD student
Mr Simon Belluzzo, MPhil student
Ms Bettina Wright, MPhil student
Ms Tania Wong, PhD student
Ms Ying Zhang, PhD student
Ms Cristina Ciogha, PhD student
- Vivian JP, Riedmaier P, Ge H, Le Nours J, Sansom FM, Wilce MCJ, Byres E, Dias M, Cowan PJ, d'Apice AJF, Hartland EL, Rossjohn J, Beddoe T. Crystal structure of a Legionella pneumophilia ecto-triphosphate diphosphohydrolase, a structural and functional homolog of the eukaryotic NTPDases. Structure 2010: 18: 228-238.
- Cazalet C, Gomez-Valero L, Rusniok C, Lomma M, Dervins-Ravault D, Newton HJ, Sansom FM, Jarraud S, Zidane N, Ma L, Bouchier C, Etienne J, Hartland EL, Buchrieser C. The Legionella longbeachae genome and transcriptome uncovers unique strategies to cause Legionnaires’ disease. PLoS Genetics 2010; 6: e1000851.
- Grubman A, Kaparakis M, Viala J, Allison C, Badea L, Karrar A, Boneca IG, Le Bourhis L, Reeve S, Smith IA, Hartland EL, Philpott DJ, Ferrero RL. The innate immune molecule, NOD1, regulates direct killing of Helicobacter pylori by antimicrobial peptides. Cell Microbiol 2010; 12: 626–639.
- Newton HJ*, Pearson JS* Badea L, Kelly M, Lucas M, Holloway G, Wagstaff KM, Dunstone MA, Sloan J, Whisstock JC, Kaper JB, Robins-Browne RM, Jans DA, Frankel G, Phillips A, Coulson BS, Hartland EL. The type III effectors NleE and NleB from enteropathogenic E. coli and OspZ from Shigella block nuclear translocation of NF-κB p65. PLoS Pathogens 2010; 6: e1000898. *joint first authors
- Ang DKY, Oates CVL, Schuelein R, Kelly M, Sansom FM, Bourges D, Boon L, Hertzog P, Hartland EL*, van Driel IR*. Cutting edge: Pulmonary Legionella pneumophila is controlled by plasmacytoid dendritic cells but not type I interferon. J Immunol 2010; 184: 5429-33 *joint senior authors
- Gao W, Chua K, Davies JK, Newton HJ, Seeman T, Harrison PF, Holmes NE, Rhee HW, Hong JI, Hartland EL, Stinear TP, Howden BP. Two novel point mutations in clinical Staphylococcus aureus reduce linezolid susceptibility and switch on the stringent response to promote persistent infection. PLoS Pathogens 2010; 6: e1000944.
- Lomma M, Dervins-Ravault D, Rolando M, Newton HJ, Samson FA, Nora T, Sahr T, Gomez-Valero L, Jules M, Hartland EL, Buchrieser C. The Legionella pneumophila F-box protein Lpp2082 (AnkB) modulates ubiquitination of the host protein parvin B and promotes intracellular replication. Cell Microbiol 2010; 12: 1272-91.
- Martinez E, Schroeder GN, Berger CN, Lee SF, Robinson KS, Badea L, Simpson N, Hall R, Hartland EL, Crepin VF, Frankel G. Binding to Na+/H+ exchanger regulatory factor 2 (NHERF2) affects trafficking and function of the enteropathogenic Escherichia coli type III secretion system effectors Map, EspI and NleH1. Cell Microbiol 2010; 12: 1718-31.
- Schroeder G, Petty N, Mousnier A, Harding CR, Vogrin AJ, Wee B, Fry NK, Harrison TG, Newton HJ, Thomson R, Beatson SA, Dougan G, Hartland EL, Frankel G. Legionella pneumophila strain 130b possesses a unique combination of type IV secretion systems and novel Dot/Icm type IV secretion system effector proteins. J Bacteriol 2010; 192: 6001-16.
- Yong SFY, Tan SH, Wee EL, Tee JJ, Sansom FM, Newton HJ, Hartland EL. Molecular detection of Legionella: moving on from mip. Front Microbiol 2010; 1: 123.
- Arbeloa A, Marches O, Oates CV, Hartland EL and Frankel G. The enteropathogenic Escherichia coli type III secretion effector EspV induces radical morphological changes in eukaryotic cells. Infect Immun 2011; 79: 1067-1076.
- Pearson JS, Riedmaier P, Marches O, Frankel G and Hartland EL. A type III effector protease NleC from enteropathogenic Escherichia coli targets NF-κB for degradation. Mol Microbiol 2011; 80: 219-30.
- Clements A, Smollett K, Lee SF, Hartland EL, Lowe M, Frankel G. EspG of enteropathogenic and enterohemorrhagic E. coli binds the Golgi matrix protein GM130 and disrupts Golgi structure and function. Cell Microbiol 2011; 13: 1429–1439.
- Dolezal P, Aili M, Tong J, Jiang JH, Marobbio CMT, Lee SF Schuelein R, Belluzzo S, Binova E, Mousnier A, Frankel G, Giannuzzi G, Palmieri F, Gabriel K, Naderer T, Hartland EL*, Lithgow T*. Legionella pneumophila secretes a mitochondrial carrier protein during infection. PLoS Pathogens 2012; 8: e1002459 *joint senior authors
- Selkrig J, Mosbahi K, Webb CT, Wells TJ, Morris F, Totsika M, Phan MD, Perry AJ, Celik N, Kelly M, Oates C, Hartland EL, Robins-Browne RM, Ramarathinam SH, Purcell AW, Schembri MA, Strugnell RA, Henderson IR, Walker D, Lithgow T. Discovery of an archetypal protein transport system in bacterial outer membranes. Nat Struct Mol Biol 2012; 19: 506-510.
- Ang DKY, Ong SZ, Brown AS, Hartland EL, van Driel IR. A method for quantifying pulmonary Legionella pneumophila infection in mouse lungs by flow cytometry. BMC Research Notes 2012; 5: 448.
- Vogrin AJ, Mousnier A, Frankel G and Hartland EL. Subcellular localization of Legionella Dot/Icm effectors. Methods Mol Biol 2013; 954: 333-44.
- Newton H, Ang D, van Driel IR, Hartland EL. The molecular pathogenesis of infections caused by Legionella pneumophila. Clin Microbiol Rev 2010; 23: 274-98.
- Yang J, Tauschek M, Hart E, Hartland EL, Robins-Browne RM. Virulence regulation in Citrobacter rodentium: the art of timing. Microbial Biotech 2010; 3: 259–268.
- Wong A, Pearson J, Robinson KS, Bright M, Munera D, Lee SF, Frankel G, Hartland EL. Enteropathogenic and enterohemorrhagic Escherichia coli: even more subversive elements. Mol Microbiol 2011; 80: 1420-1438.
- Schuelein R, Ang D, van Driel IR, Hartland EL. Immune control of Legionella infection: an in vivo perspective. Front Microbiol 2011; 2: 126.