Fig. 5

Knockout of GRASP55 impairs prodigiosin cytotoxicity and alters prodigiosin effects on the Golgi apparatus. A GRASP55 was knocked out in HeLa wt cells and KO was verified by western blot. B HeLa wt and HeLa GRASP55 KO cells were treated with different concentrations of prodigiosin for 24 h. After treatment, cell viability was measured using a thiazolylblue (MTT) assay. Results are shown as the mean ± SEM of three independent experiments performed in triplicates for each treatment. C IC₅₀ values and statistical analysis for MTT assays in HeLa wt and HeLa GRASP55 KO cells after 24 and 72 h treatment with prodigiosin. Please note that the MTT assay for HeLa wt cells was independent from the one shown in Fig. 1B; accordingly, IC₅₀ values slightly differ. (D-H) HeLa wt and HeLa GRASP55 KO cells were treated with DMSO, 10 nM or 100 nM prodigiosin for 24 h and effects on Golgi apparatus structure were investigated by transmission electron microscopy. D Representative electron micrographs are shown. Scale bar: 200 nm. E Cisternae length and F cisternae number per stack were quantified. G Golgi stacks were categorized into organized (stacked structures with three or more cisternae) and disorganized (multiple unstacked cisternae and vesicles). H Stacks were classified as containing mainly flat or mainly bulky/swollen cisternae. At least 50 Golgis per treatment were quantified after blinding and randomization. Bars represent the means ± SD. p values were determined by ordinary one-way ANOVA with Dunnett´s post hoc test. * p < 0.05; ** p < 0.01; *** p < 0.001; **** p < 0.0001