Figure 5. IpgD shapes global Ca²⁺ responses and inhibits InsP₃‐mediated signaling during prolonged infection kinetics.

Cells were loaded with the Ca²⁺ indicators Fura‐2‐AM (A–C) or Fluo‐4‐AM (D, E) and challenged with WT Shigella (red) or the ipgD mutant (blue). Samples were subjected to Ca²⁺ imaging (Materials and Methods). Changes in the ratio of Fura‐2 fluorescence intensity (∆R) were calculated relative to the resting ratio value (R ₀) as ∆R/R ₀.

1. Representative traces of single cell global Ca²⁺ responses are shown for challenge with the indicated strains.
2. Representative traces of infected HeLa cells stimulated with histamine at the indicated concentrations at 90 min post‐infection.
3. Amplitude of Ca²⁺ responses relative to the maximal response upon stimulation at the indicated histamine concentrations of cells infected with the indicated bacteria for 90 min. Wilcoxon test, **P < 0.01.
4. Representative traces of global Ca²⁺ responses are shown for polarized TC7 cells. The arrow indicates stimulation with 30 μM ATP.
5. Dot plot representing the % of polarized TC7 cells challenged with the indicated bacterial strain, showing global Ca²⁺ responses during a 30‐min period, 30 min following infection, and prior to ATP stimulation (dotted line in panel D) (N = 7, > 200 cells). Wilcoxon test: **P = 0.007.