Figure 2(A) Confocal microscopy images of ECs silenced with a control siRNA (siCTL) or one targeting STIM1 (siSTIM1) and stained for endogenous LAMP-1 (in green) to visualize LEs and DAPI (in blue) to highlight the nucleus. The yellow line is drawn to define cell periphery. Scale bar = 20 μm. On the right, inset panels to highlight respective perinuclear and peripheral area of the cell. Scale bar = 5 μm. (B) Distribution of size, normalized on cell size, quantified by image (as in a) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are from three independent experiments for a total of 249 endosomes (15 siCTL cells) and 441 endosomes (13 siSTIM1 cells). In the right inset, the cumulative distribution used for the Kolmogorov-Smirnov test, p≤ 0,001 ***, is shown. The p-value refers to the rejection of the null hypothesis in favor of the alternative hypothesis that siCTL LE distribution has longer tail than siSTIM1 LE one. (C) Average number, normalized on cell size, quantified by image (as in a) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are the average ± SEM of three independent experiments for a total of 249 late endosomes in 15 siCTL cells (16 ± 2 endosomes per cell) and 441 late endosomes in 13 siSTIM1 cells (34 ± 3 endosomes per cell) and analyzed by a two-tailed heteroscedastic Student's t-test, p≤ 0,001 ***. (D) Distribution of distance to nucleus, normalized on cell size, quantified by image (as in a) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are from three independent experiments for a total of 249 late endosomes in 15 siCTL cells (16 ± 2 endosomes per cell) and 441 late endosomes in 13 siSTIM1 cells (34 ± 3 endosomes per cell) and analyzed by a two-tailed heteroscedastic Student's t-test, p≤ 0,001 ***. (E) Confocal microscopy images of ECs silenced with a control shRNA (shCTL) or one targeting STIM1 (shSTIM1), rescued for GFP expression alone (shCTL/GFP and shSTIM1/GFP) or for GFP- STIM1 WT (shSTIM1/GFP-STIM1 WT), GFP- STIM1 NN (shSTIM1/GFP-STIM1 NN) or GFP- STIM1 AA (shSTIM1/GFP-STIM1 AA) and stained for endogenous LAMP-1 (in red) to visualize LEs and DAPI (in blue) to highlight the nucleus. The yellow line is drawn to define cell periphery. Scale bar = 20 μm. On the right, inset panels to highlight respective perinuclear and peripheral area of the cell. Scale bar = 5 μm. (F) Upper panel, Distribution of distance to nucleus, normalized on cell size, quantified by image (as in e) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are from of two independent experiments for a total of 436 late endosomes in 13 shCTL/GFP cells (34 ± 6 endosomes per cell), 1452 late endosomes in 12 shSTIM1/GFP cells (121 ± 13 endosomes per cell) and 498 late endosomes in 10 shSTIM1/GFP-STIM1 WT cells (50 ± 5 endosomes per cell) and analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,01; Bonferroni for shCTL/GFP and shSTIM1/GFP p≤ 0,001 *** (orange) and for shSTIM1/GFP and shSTIM1/GFP-STIM1 WT p≤ 0,001 *** (green). Lower panel, Distribution of distance to nucleus, normalized on cell size, quantified by image (as in e) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are from of two independent experiments for a total of 498 late endosomes in 10 shSTIM1/GFP-STIM1 WT cells (50 ± 5 endosomes per cell), 1057 late endosomes in 11 shSTIM1/GFP-STIM1 NN cells (96 ± 12 endosomes per cell) and 346 late endosomes in 10 shSTIM1/GFP-STIM1 AA cells (35 ± 2 endosomes per cell) and analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,01; Bonferroni for shSTIM1/GFP-STIM1 WT and shSTIM1/GFP-STIM1 NN p≤ 0,05 * (orange) and for shSTIM1/GFP-STIM1 NN and shSTIM1/GFP-STIM1 AA p≤ 0,05 * (green). (G) Average size, normalized on cell size, quantified by image (as in e) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are the average ± SEM of two independent experiments for a total of 436 late endosomes in 13 shCTL/GFP cells (34 ± 6 endosomes per cell), 1452 late endosomes in 12 shSTIM1/GFP cells (121 ± 13 endosomes per cell), 615 late endosomes in 12 shSTIM1/GFP-STIM1 WT cells (51 ± 5 endosomes per cell), 1278 late endosomes in 12 shSTIM1/GFP-STIM1 NN cells (106 ± 15 endosomes per cell) and 506 late endosomes in 12 shSTIM1/GFP-STIM1 AA cells (42 ± 7 endosomes per cell) and analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for shCTL/GFP and shSTIM1/GFP p≤ 0,001 ***, for shCTL/GFP and shSTIM1/GFP-STIM1 WT p> 0.05 not significant (ns), for shSTIM1/GFP-STIM WT and shSTIM1/GFP-STIM1 NN p≤ 0,001 ***, for shSTIM1/GFP and shSTIM1/GFP-STIM1 NN p≤ 0,001 *** and for shSTIM1/GFP-STIM WT and shSTIM1/GFP-STIM1 AA p> 0.05 not significant (ns). (H) Average number, normalized on cell size, quantified by image (as in e) segmentation (see Material and Method, Confocal microscopy and early/late quantification) of LAMP-1+ endosomes. Results are the average ± SEM of two independent experiments for a total of 436 late endosomes in 13 shCTL/GFP cells (34 ± 6 endosomes per cell), 1452 late endosomes in 12 shSTIM1/GFP cells (121 ± 13 endosomes per cell), 615 late endosomes in 12 shSTIM1/GFP-STIM1 WT cells (51 ± 5 endosomes per cell), 1278 late endosomes in 12 shSTIM1/GFP-STIM1 NN cells (106 ± 15 endosomes per cell) and 506 late endosomes in 12 shSTIM1/GFP-STIM1 AA cells (42 ± 7 endosomes per cell) and analyzed by a parametric two-tailed analysis of variance (ANOVA) with Bonferroni post hoc analysis. ANOVA p≤ 0,001; Bonferroni for shCTL/GFP and shSTIM1/GFP p≤ 0,001 ***, for shCTL/GFP and shSTIM1/GFP-STIM1 WT p≤ 0,001 ***, for shSTIM1/GFP-STIM WT and shSTIM1/GFP-STIM1 NN p≤ 0,05 *, for shSTIM1/GFP and shSTIM1/GFP-STIM1 NN p≤ 0,01 ** and for shSTIM1/GFP-STIM WT and shSTIM1/GFP-STIM1 AA p> 0.05 not significant (ns).