Role of glycogen synthase kinase 3 in squamous differentiation of pig airway epithelial cells: A primary study.

To investigate if glycogen synthase kinase 3 (GSK3) is involved in squamous differentiation of airway (tracheobronchial) epithelial cells, primary pig airway epithelial cells were treated with lithium chloride, a highly selective inhibitor of GSK3. Change in morphology of cells was monitored under microscopy, and expression of beta-catenin, phosphorylated GSK3 and involucrin, a squamous differentiation marker, were dectected by Western blotting, while expression of mRNA of another squamous differentiation marker, small proline-rich protein, was detected by RT-PCR. Further, luciferase reporter assay was used to assess the activation of beta-catenin/Tcf signaling. The results demonstrated that lithium was able to induce a squamous morphology of the cells, and to enhance the expression of involucrin and small proline-rich protein mRNA. Moreover, lithium increased inhibitory phosphorylation of GSK3, augmented nuclear translocation of beta-catenin in a dose- and time-dependent manner. Activation of beta-catenin/Tcf signaling was observed after the elevation of squamous differentiation markers. Taken together, these data suggest that GSK3 is possibly involved in squamous differentiation of pig airway epithelial cells.