Fig. 9. Efects of latrunculin B on the mobility of NHE3-EGFP and NHE3585-EGFP. OK cells transfected with NHE3-EGFP or OK/NHERF2 cells transfected with NHE3585-EGFP were incubated with latrunculin B (0.1 or 0.05 µM) at 37°C for 30 minutes. Latrunculin B (1 µM, 30 minutes) completely abolished the presence of microvilli (data not shown). F-actin distribution at the apical microvilli was partially disrupted with 0.1 µM latrunculin B for 30 minutes (A). In most of the cells, the apical NHE3-EGFP moved intracellularly as shown in (B). Cell exposed to latrunculin B (0.05 µM for 30 minutes) still had microvilli and NHE3-EGFP remained in the microvilli (C). OK/NHE3-EGFP cells exposed to latrunculin B (0.05 µM) for 30 minutes at 37°C had fluorescence recovery analyzed in the apical plasma membrane non-JN and in the intracellular JN domains. There was no change in M_f or D_eff of NHE3-EGFP in the intracellular JN domain (M_f=37.0±8.3% and D_eff=(3.9±1.3) x10^–10 cm²/second; n=6). Apical non-JN NHE3-EGFP had decreased M_f compared with cells not treated with latrunculin B (D, left). Similar studies of apical surface non-JN NHE3585-EGFP in OK/NHERF2/NHE3585-EGFP cells also showed a large decrease in mobile fraction (M_f) caused by this latrunculin B treatment (D, right). The effective diffusion coefficients with and without latrunculin B (0.05 µM) are shown in (E) and did not significantly change with latrunculin B. Data are mean±s.e.m. 7 cells studied for latrunculin B treatment in D and E.