title: Bacillus anthracis TIR Domain-Containing Protein Localises to Cellular Microtubule Structures and Induces Autophagy.
abstract: Toll-like receptors (TLRs) recognise invading pathogens and mediate downstream immune signalling via Toll/IL-1 receptor (TIR) domains. TIR domain proteins (Tdps) have been identified in multiple pathogenic bacteria and have recently been implicated as negative regulators of host innate immune activation. A Tdp has been identified in Bacillus anthracis, the causative agent of anthrax. Here we present the first study of this protein, designated BaTdp. Recombinantly expressed and purified BaTdp TIR domain interacted with several human TIR domains, including that of the key TLR adaptor MyD88, although BaTdp expression in cultured HEK293 cells had no effect on TLR4- or TLR2- mediated immune activation. During expression in mammalian cells, BaTdp localised to microtubular networks and caused an increase in lipidated cytosolic microtubule-associated protein 1A/1B-light chain 3 (LC3), indicative of autophagosome formation. In vivo intra-nasal infection experiments in mice showed that a BaTdp knockout strain colonised host tissue faster with higher bacterial load within 4 days post-infection compared to the wild type B. anthracis. Taken together, these findings indicate that BaTdp does not play an immune suppressive role, but rather, its absence increases virulence. BaTdp present in wild type B. anthracis plausibly interact with the infected host cell, which undergoes autophagy in self-defence.
authors.affiliation: Department of Life Sciences, Imperial College London, London, United Kingdom.|Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore.
authors.forename: Emil
authors.initials: E
authors.lastname: Carlsson
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom.
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Thwaite
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom.
authors.forename: Dominic C
authors.initials: DC
authors.lastname: Jenner
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom.
authors.forename: Abigail M
authors.initials: AM
authors.lastname: Spear
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Flick-Smith
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom.
authors.forename: Helen S
authors.initials: HS
authors.lastname: Atkins
authors.affiliation: Department of Life Sciences, Imperial College London, London, United Kingdom.
authors.forename: Bernadette
authors.identifier: http://orcid.org/0000-0001-9598-9832
authors.initials: B
authors.lastname: Byrne
authors.affiliation: Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore.
authors.forename: Jeak Ling
authors.initials: JL
authors.lastname: Ding
mesh_terms: D000818:Animals; D000881:Anthrax / Q000382:microbiology; D001343:Autophagy / Q000235:genetics / Q000502:physiology*; D001408:Bacillus anthracis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D008870:Microtubules / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D015398:Signal Transduction; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins