Once internalized, S. flexneri quickly disrupts the vacuolar membrane breaking free into the host cell cytosol [5, 6], which is unlike S. Typhimurium where upon entry they occupy a phagosome within the infected cells [9]. S. flexneri then SRT2104 express the IcsA (VirG) protein that

localizes to Ferrostatin-1 ic50 one pole of the bacterial outer membrane. IcsA recruits the actin-associated protein N-WASP, initiating actin polymerization at the bacterial membrane [10]. In a similar manner as during L. monocytogenes infections, actin recruitment at one pole of S. flexneri creates a “”comet tail”" that propels the bacterium throughout the host cell and into neighboring cells [11]. Although those comet tail strategies are similar, L. monocytogenes utilize the bacterial factor ActA

to mimic N-WASP and thus directly recruit the ARP2/3 complex to the bacteria without the need of N-WASP itself [12]. Thus, although S. flexneri adopt similar pathogenic strategies as other enteric bacterial pathogens, there are distinct differences that occur during S. flexneri infections, requiring researchers to investigate these pathogens independently. The spectrin cytoskeleton lies just beneath the plasma membrane of eukaryotic cells, providing structural support and protein-sorting see more capabilities to the membrane [13]. The spectrin sub-membranous scaffold is composed of spectrin heterotetramers, which are interlinked by short actin filaments of 14-16 monomers [14]. Spectrin/actin interactions are facilitated by the spectrin-associated proteins adducin and protein 4.1 (p 4.1), which encourage spectrin-actin binding

and can simultaneously bind a number of membrane-associated proteins [15–18]. acetylcholine Consequently, adducin and p4.1 enable the proper anchoring and sorting of membrane associated proteins at the plasma membrane in conjunction with the spectrin scaffold [15, 19]. The spectrin cytoskeleton has recently been shown to be important for the pathogenesis of the invasive pathogens S. Typhimurium and L. monocytogenes [20]. Spectrin, adducin and p4.1 in conjunction with actin are recruited to sites of bacterial/host cell invasion as well as to structures generated at various stages of those intracellular infections. Knockdown of spectrin cytoskeletal components demonstrated that they were necessary for both S. Typhimurium and L. monocytogenes pathogenesis [20]. Based on these findings, we hypothesized that S. flexneri might also exploit spectrin cytoskeletal components during their infections of host cells. In this study we examined the involvement of the spectrin cytoskeleton during the invasion of S. flexneri into epithelial cells as well as at later time-points, during the formation of comet tails. We demonstrate striking differences in spectrin cytoskeletal involvement in S. flexneri pathogenesis as compared to S. Typhimurium or L. monocytogenes. We show that p4.1, but not spectrin or adducin, is acutely recruited to the ruffles generated during the initial invasion of S.