Figure 6.

Fluorescent sensor Mag-Fluo-4 reports depletion of ER Ca²⁺ in Jurkat cells as a response to irradiation. (A) Fluorescent images of representative Jurkat cells loaded with Mag-Fluo-4 (green, first column) and stained with ER tracker red (magenta, second column) exhibit colocalization of both fluorescent signals in merged image (third column). (B) In untreated control cells, the Mag-Fluo-4 fluorescence in the ER remains constant. (C) Challenging cells with 2 µM Tg (D) or irradiating cells with 5 Gy x rays elicits progressive decrease in Mag-Fluo-4 fluorescence in ER with concomitant increase in cytosol. Times in images denote time point of imaging after respective treatment. Corresponding mean values of relative Mag-Fluo-4 fluorescence (± SD) in ROI (white circle in C) over ER in untreated control cells (E), cells exposed to 2 μM Tg (F), and cells irradiated with 5 Gy x rays (G). Start of imaging after treatments are indicated by an arrow. Data in E–G were normalized to fluorescence values at start of analysis from ≥35 cells per treatment in ≥7 experiments. Scale bars, 10 µm.