Activation of the Unfolded Protein Response Is Required for Defenses against Bacterial Pore-Forming Toxin In Vivo
Figure 2
Loss of specific UPR pathways cause hypersensitivity to PFT but not other toxins or a pathogenic bacteria.
(A) Comparison of ER stress response mutants to wild-type N2 on 25% Cry5B-expressing E. coli plates indicate ire-1(v33) and xbp-1(zc12) are hypersensitive to Cry5B intoxication. Two representative worms are shown for each strain 48 hours after feeding either on E. coli without Cry5B or on E. coli of which 25% expressed Cry5B. Scale bar is 0.2 mm. (B) A lethal concentration assay was performed using purified Cry5B toxin to quantitatively compare sensitivities of wild-type N2 and the ER stress mutants. Lethality was determined after 8 days. This semi-log graph represents three independent experiments, and each data point is the mean and standard deviations of the experiments. (C) A Cry5B developmental inhibition assay was performed beginning with synchronized worms at the first larval stage. Worms were grown on plates containing different percentages of Cry5B-expressing E. coli (% Cry5B as indicated under the figure), and the percent of worms reaching the L4 stage or adulthood 72 hours later is indicated. ire-1(v33) was included only on the plates with 0% Cry5B. Data are presented as mean and standard deviation. (D) A lethal concentration assay comparing sensitivity to CuSO4 revealed xbp-1(zc12) is not hypersensitive compared to wild-type N2. Lethality was determined after 8 days of CuSO4 exposure, the same time frame as the Cry5B lethality assay. Data, plotted semi-log, are the mean and standard deviation of three independent experiments. (E) A lethal concentration assay comparing sensitivity to H2O2 revealed xbp-1(zc12) is not hypersensitive compared to wild-type N2. Lethality was determined after 4 hours of H2O2 exposure. Data, plotted semi-log, are the mean and standard deviation of three independent experiments. (F) A lifespan assay was used to compare the ER stress mutants to slow killing by P. aeruginosa PA14. This graph represents combined data from three experiments.