Overexpression of GFP-ERK1c results in Golgi fragmentation. (A) Localization and effect on Golgi apparatus of the GFP-ERK constructs. HeLa cells were transfected with GFP-ERK1c, GFP-ERK1, GFP-KA-ERK1c, or GFP and grown on microslides in 12-well plates. Fourteen hours after transfection, the cells were fixed and stained with anti-p58 Ab (αp58) and examined with a fluorescence microscope. Fragmentation or lack of Golgi apparatus is indicated by the white arrows. (B) Quantitation of Golgi fragmentation. The HeLa cells (200 cells in each slide) in panel A were counted, and the percentage of cells with fragmented Golgi apparatus out of cells expressing GFP-ERK1c is presented. The values are the means ± standard errors (error bars) for three experiments.