Fig. 4.

In MDCK cells the AQP2-L137P mutant does not traffic to the apical plasma membrane following forskolin stimulation. a AQP2-expressing MDCK cells grown on semi-permeable supports were stimulated with forskolin (for), to increase intracellular cAMP levels, and surface proteins biotinylated from the apical side. Representative immunoblotting from one of four experiments is shown. To assess the purity of the biotin isolation, biotin was omitted from some samples (− b) and immunoblotting with proteasome 20S (P20S) was used to determine if biotin passed the cell membrane. b Quantification of accumulated data from four independent biotinylation experiments. The biotinylated (surface) pool of AQP2 was normalized to total cellular AQP2 levels for each individual sample followed by normalization to first control within either AQP2-WT group or AQP2-L137P group. Each group was analysed by unpaired t test to determine significant difference between control and forskolin treatment. A significant effect of forskolin on surface AQP2 levels was observed in AQP2-WT-expressing cells that was not apparent in AQP2-L137P-expressing cells. *p < 0.05