TorsinA is a static ER resident and is excluded from ERES. (A, B) Epifluorescence microscopy of U2OS cells expressing VSVG-(ts045)–GFP (at 39.5°C) or torsinA–mGFP (at 37°C). (A′, B′) Costaining with βCOP after 2 h incubation at 15°C. (C–F) Confocal microscopy of cells expressing VSVG-(ts045)–GFP (at 39.5°C), NPY–GFP, ER–GFP, or torsinA–mGFP (at 37°C). (C′–F′) Costaining with Sec31A after 2 h incubation at 10°C. Scale bars, 10 μm. (G) Quantification of colocalization of the indicated GFP-tagged proteins with Sec31A. N>20 cells for each condition. Bars indicate standard error of the mean. *Significant difference between conditions (P<0.05).