FIGURE 1:

NHE3-S719A mutant has reduced NHE3 activity due to reduced surface expression. Confluent Caco-2/bbe cells were grown for 12 d and then infected with Ad-HA-NHE3-WT or -S719A. (A) NHE3 activities were measured under basal conditions and with DMAT (30 µM, 30 min) treatment. NHE3-S719A mutant cells decreased basal NHE3 activity by ∼50% and lost the effect of DMAT, a specific inhibitor of CK2. DMAT also reduced the NHE3 activity of NHE3-WT cells by ∼40%. NHE3 activity was measured from the initial rates of Na⁺-dependent intracellular alkalinization. (B) Immuno­fluorescence detection of microvillus WGA and NHE3 colocalization indicates that the presence of NHE3-S719A is ∼50% less in microvillus than is NHE3-WT. Reconstructed xz-images and a single xy-image (0.5 μM) taken at the same distance from initially detected BB image for WT NHE3 and NHE3-S719A. n, number of separate experiments. p values are via paired t tests.