FIGURE 9.
UTP inhibition of DRA is dependent on PDZK1. A and B, in HEK cells transfected only with EGFP-DRA, there is no inhibition of Cl/HCO3 exchange activity by 100 μm UTP (n = 8–10 for each group) (A) despite a typical peak and plateau-type elevation of intracellular calcium (B). C, lysates from 14-day confluent Caco-2 and Caco-2/BBE cells and from HEK cells were tested for the expression of endogenous NHERF, E3KARP, PDZK1, and IKEPP. Note that in HEK cells E3KARP and PDZK1 are relatively underexpressed. The nature of the upper band detected by the anti-PDZK1 antibody (arrowhead) is unknown. D, UTP inhibits DRA activity (maximal pHi change −18%, p < 0.05; initial slope −25%, p < 0.05; n = 10–11 for each group) in HEK/EGFP-DRA cells that are stably transfected with EGFP-PDZK1.