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. 2011 Jul 1;124(13):2143–2152. doi: 10.1242/jcs.080762

Fig. 2.

Fig. 2.

ER–mitochondrial coupling observed during early phases of ER stress. (A) Confocal images of HeLa cells transiently expressing ER-targeted RFP (red) and stained with Mitotracker Green (green), either treated with 0.5 μg/ml tunicamycin (Tun) for 4 hours or left untreated (control). Scale bars: 10 μm. (B,C) Quantification of the Manders' coefficient M1 (fraction of ER in colocalization with mitochondria) or M2 (fraction of mitochondria in colocalization with ER). (D,E) Quantification of the M1 and M2 coefficients within the predefined subcellular regions. (F) Representative transmission electron microscopy images from control cells or cells treated with 0.5 μg/ml tunicamycin for 4 hours. Three different magnifications of the same cell are shown. Close ER–mitochondrial contacts are indicated only in the middle panel by white arrows. Scale bars: 0.5, 1 and 2 μm as indicated. N, nucleus. (G) Quantification of the percentage of mitochondria with close ER contacts per field. Co, control (untreated). Data are means ± s.e.m. *P<0.05; **P<0.01; ***P<0.001 compared with respective controls or controls in the same subcellular zone.