FIGURE 2.

PMA- but not EGF-stimulated phosphorylation of β4 depends on PKC. PA-JEB/β4 keratinocytes, starved overnight in growth factor-free medium and pretreated for 1 h with the PKC inhibitor Gö6983 (100 nm), were left unstimulated or stimulated with PMA or EGF for 10 min. Additionally growth factor-starved PA-JEB/β4 keratinocytes were pretreated with (+) or without (−) 100 nm PMA for 24 h to deplete the activity of PKC and then stimulated. Cell lysates were analyzed by immunoblotting with antibodies specific to phosphorylated β4 (Ser-1356 and Ser-1364), total β4, phospho-ERK1/2, and total ERK1/2. Note that both EGF-stimulated phosphorylation of β4 and ERK1/2 do not depend on PKC.