Fig. 1. eMTDΔ4 of NOXA induces necrotic cell death via cytosolic Ca²⁺ influx.

a Noxa domains such as MTD, BH3, eMTD, and eMTDΔ4 are indicated. b HeLa cells were treated with full-length (fl) recombinant Noxa protein (20 μM), eMTD (20 μM), and eMTDΔ4 (20 μM), and cell viability was measured by MTS assay. c Images of HeLa cells treated with eMTDΔ4 were obtained using bright-field microscopy. d–f HeLa cells were treated with eMTDΔ4 in the presence of zVAD-fmk (d), Necrostatin 1 (e), and Bafilomycin A1 (f). g Images of HeLa cells with or without eMTDΔ4 were captured by time-lapse confocal microscopy in HBSS buffer containing Ca²⁺. Cytosolic Ca²⁺ concentration was visualized using Fluo-4-AM. The relative fluorescent intensity of Fluo-4-AM in two regions of interest (ROI) was graphed over time. All results are represented as means and standard deviation from triplicate samples. *p < 0.05, **p < 0.005, and ***p < 0.001, samples versus control