title: Lipopolysaccharide surface structure does not influence IcsA polarity.
abstract: Shigella species are the causative agents of human bacillary dysentery. These bacteria spread within the lining of the gut via a process termed actin-based motility whereby an actin 'tail' is formed at the bacterial pole. The bacterial outer membrane protein IcsA initiates this process, and crucially is precisely positioned on the bacterial polar surface. Lipopolysaccharide (LPS) O-antigen surface structure has been implicated as an augmenting factor of polarity maintenance due to the apparent dysregulation of IcsA polarity in O-antigen deficient strains. Due to Shigellae having long and short O-antigen chains on their surfaces, it has been proposed that O-antigen chain lengths are asymmetrically distributed to optimize IcsA exposure at the pole and mask exposure laterally. Additionally, it has been proposed that LPS O-antigen restricts IcsA diffusion from the pole by maintaining minimal membrane fluidity. This study utilizes minicells and quantitative microscopy providing data refuting the models of asymmetric masking and membrane diffusion, and supporting a model of symmetric masking of IcsA. We contend that IcsA surface distribution is equivalent between wild-type and O-antigen deficient strains, and that differences in cellular IcsA levels have confounded previous conclusions.
authors.affiliation: Department of Molecular and Cellular Biology, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Matthew Thomas
authors.initials: MT
authors.lastname: Doyle
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton 08544-1014, USA.
authors.forename: Marcin
authors.initials: M
authors.lastname: Grabowicz
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton 08544-1014, USA.
authors.forename: Kerrie Leanne
authors.initials: KL
authors.lastname: May
authors.affiliation: Department of Molecular and Cellular Biology, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia renato.morona@adelaide.edu.au.
authors.forename: Renato
authors.initials: R
authors.lastname: Morona
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008560:Membrane Fluidity; D016254:Mutagenesis, Insertional; D019081:O Antigens / Q000737:chemistry* / Q000235:genetics; D012763:Shigella flexneri / Q000737:chemistry* / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics; D000069320:Type V Secretion Systems / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D019081:O Antigens; D014157:Transcription Factors; D000069320:Type V Secretion Systems; C058483:virG protein, Shigella flexneri
keywords: Shigella; autotransporter; bacterial pole; lipopolysaccharide; minicell; outer membrane