Figure 6.

Epithelial barrier modulates cell signaling. (A) Epidermal growth factor (EGF) receptor (EGFR) is localized to the basolateral membrane of NHBE cells, and the application of shear stress or the knockdown of septin-2 does not alter its localization. (B) Under static conditions, placement of EGF in the basolateral chamber leads to more phosphorylated–extracellular signal–regulated kinase (ERK) than when placed on the apical membrane. Knockdown of septin-2 does not alter this. (Left) Under shear conditions, placement of EGF in either the apical or basolateral chamber leads to similar p-ERK after septin-2 knockdown (middle), as well as similar p-EGFR (46). However, in cells treated with a nontargeting construct, there is significantly less p-ERK (middle), as well as p-EGFR (46), in cells treated with apical EGF compared with cells treated with basolateral EGF. (C) Bar graph of densitometric analysis from three separate experiments of ERK phosphorylation (S2, septin 2 shRNA; NT, nontargeting shRNA; shaded bars, apically placed ligand; closed bars, basolaterally placed ligand; n = 3; *P < 0.05 with one-way ANOVA).