CYTOSKELETAL ARCHITECTURE IN MOUSE LUNG EPITHELIAL-CELLS IS REGULATEDBY PROTEIN-KINASE C-ALPHA AND CALPAIN-II

Brief exposure to 12-O-tetradecanoylphorbol 13-acetate (TPA) caused a uniformly flattened population of mouse lung epithelial cells to becom e more heterogeneous; some cells rounded up, and others detached to ov erlap with flatter cells. Actin stress fiber organization was disrupte d, and F-actin accumulated in lamellipodia. Vinculin dissociated from the focal adhesion plaques to diffuse throughout the cytoplasm. Inhibi tion of protein kinase C (PKC) activity blocked these effects of TPA. After 8 h of TPA exposure, actin filaments reassembled and vinculin ag ain localized to the cell periphery. Calpain inhibition attenuated the decrease of PKC-alpha protein and PKC activity from the membrane frac tion, and prevented the redistribution of cytoskeletal elements. Talin immunostaining was widespread throughout control cells but was locali zed to the periphery 8 h after treatment with TPA or with inhibitors o f PKC and calpain. Both vinculin and talin concentrations increased wi th prolonged TPA treatment. PKC-zeta and calpain II were not appreciab ly affected by TPA exposure. Translocation of PKC-alpha to the membran e, followed by its calpain-induced downmodulation, is apparently requi red for the reversible pattern of cytoskeletal changes caused by TPA.