Increase of paracellular resistance after CK2-dependent phosphorylation of occludin. Two-path impedance spectroscopy was applied to measure the two components of epithelial resistance (Repi), paracellular resistance (Rpara, reflecting the pathway across the tight junctions) and transcellular resistance (Rtrans, reflecting the pathway across the cell membranes). Measurements were done in MDCK C11 cells, which were stably transfected with the indicated occludin-FLAG3 constructs. In Occ-FLAG3-T400E/T404E/S408E-transfected cells a dramatic increase in Rpara was detectable compared to wildtype occludin and to Occ-FLAG3-T400A/T404A/S408A-transfected cells, while Rtrans was unchanged. Due to the about fourfold increase of Rpara, the overall epithelial resistance Repi was also increased. The figure shows combined results of 6 independent measurements on two clones of each construct. ** p < 0.01.