G₁ Cell Cycle Arrest Is Induced by the Fourth Extracellular Loop of Meningococcal PorA in Epithelial and Endothelial Cells

Figure 1

Neisseria meningitidis recruits the 37 kDa laminin receptor precursor and this is mediated by extracellular Loop4 of the outer membrane protein PorA. (a) HBMECs were infected with either wild-type N. meningitidis MC58 or its isogenic derivative MC58 ΔPorA-Loop4 and fixed and stained to measure colocalization of 37LRP (red) and 67LR (green) with bacterial colonies (stained with DAPI; blue). Representative confocal images are shown; white arrow indicates a meningococcal colony on the cell surface. Scale bar represents 20 μm. (b) Colocalization coefficient (%) of N. meningitidis MC58 wild-type microcolonies with either 37LRP (black bar) or 67LR (grey bar) ( value ≤ 0.001; -test). (c) The effect of LamR siRNA treatment or antibody inhibition on the invasion of N. meningitidis MC58 into HBMECs. Prior to infection, cells were treated with either nontargeting siRNA or LamR siRNA (for 48 h), or monoclonal antibody directed towards a specific LamR population for one hour (A7 for 37LRP or Mluc5 for 67LR; both at 25 μg ml^-1). The number of bacteria per cell was determined by counting colony-forming units after overnight incubation. Bacterial invasion is expressed as a percentage normalized to the untreated control. Assays were carried out in triplicate in three independent experiments (; one-way ANOVA with Dunnett’s test applied post hoc).

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