Fig. 4

Involvement of p38 MAPK, PKC and PKA in EGFR signaling and EGF-stimulated activin subunit expression. (A) Effects of SB203580 (p38 MAPK inhibitor) on EGF-stimulated expression of inhbaa, inhbab and inhbb in cultured follicle cells. The cells were treated with EGF at 20 nM for 2 h and the inhibitor was added 30 min earlier. (B) Effects of GF109203X (PKC inhibitor) on EGF-stimulated expression of inhbaa, inhbab and inhbb in cultured follicle cells. (C) Combined effects of U0126, SB203580 and GF109203X on the expression of activin subunits. The cells were pre-treated with the three inhibitors for 30 min followed by treatment with EGF at 20 nM for 2 h. (D) Involvement of PKA in basal and EGF-stimulated expression of activin subunits. The follicle cells were treated with EGF at 20 nM for 2 h in the presence or absence of H89 (PKA inhibitor), which was added 30 min earlier. The expression values are the mean ± SEM (n = 3–4). **P < 0.01; ***P < 0.001 vs. respective control of each gene. Each graph is representative of four independent experiments. (E) EGF-induced p38 MAPK phosphorylation (p-p38 MAPK) in the follicle cells. β-actin was used as the loading control. The phosphorylation could be abolished by EGFR inhibitor AG1478. (F) Effects of U0126, SB203580 and GF109203X on basal and EGF-induced Akt phosphorylation in cultured follicle cells. (G–I) Effects of SB203580, H89 and GF109203X on basal and EGF-stimulated Akt and MAPK3/1 phosphorylation. The zebrafish follicle cells were pre-treated with each inhibitor for 30 min before treatment with EGF for 5 min.