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. 2005 Aug;73(8):5115–5126. doi: 10.1128/IAI.73.8.5115-5126.2005

FIG. 8.

FIG. 8.

Requirement for Stx1 enzymatic activity and the ribotoxic stress response in Stx1-induced apoptosis of THP-1 cells. Cells were incubated with Stx1 or Stx1A− (E167Q-R170L) or Stx1 B-subunits (400 ng/ml and 800 ng/ml, respectively) for 6 h. (A) Percent apoptosis was analyzed by flow cytometry following Annexin V and PI staining. Data shown are means ± standard errors of the means from at least two independent experiments. (B) Caspase-3, -8 and -9 activities were measured using specific colorimetric substrates as described in Materials and Methods. Control cells were not treated with Stx1, Stx1A−, or Stx1 B-subunits. Data shown are means ± standard errors of the means from three independent experiments. *, **, and ***, significant differences (P < 0.01) within treatment groups relative to Stx1-treated cells. (C) Cells were treated with Stx1, cycloheximide (10 to 200 μM), or anisomycin (0.1 to 10 μg/ml) for 5 h, and apoptosis was measured by flow cytometry following Annexin V and PI staining. CHX, cycloheximide; Aniso, anisomycin.