G238V is degraded by proteasomes in MDCK cells. MDCK cells were transiently transfected with wild-type Bsep-GFP (bottom row) or G238V (top row) for 48 hours. The transfected cells were then either treated with 5 μmol/ml MG-132 for an additional 2, 8, or 12 hours or left untreated (controls, indicated as 0 h). All images were acquired under identical conditions, in which gain was optimized for the treated cells in order to avoid saturation of the signal. Under these conditions, G238V was barely detectable in MDCK cells not treated with MG-132 (G238V, 0 h). Protein aggregates were seen as a number of signals at perinuclear positions in the cytoplasm. In each panel, the top part shows the en face image and the bottom part shows the Z-sectioning image.