Fig. 5. Regulation of distal splice-site selection by p38 MAPK and p42/p44 MAPK, and Clk1 and Clk4. Podocytes were treated with the p38 MAPK inhibitor SB203580 (10 µM), the p42/p44 MAPK inhibitor PD98059 (10 µM) or the Clk/Sty inhibitor TG003 (1 µM) in the presence or absence of 1 nM TGF1. (A) mRNA from cells treated as above were subjected to RT-PCR using primers that detect both isoform families of VEGF, ^*P<0.05 compared with control, ⁺P<0.05 compared with TGF alone. (B) Proteins were resolved by immunoblotting. (C) Quantitative ELISA for VEGF_xxxb and VEGF_total. TGF1-mediated upregulation of distal splicing was not seen in the presence of SB203580, DN-p38MAPK or TG003 but was present during PD98059 treatment. ^***P<0.001 compared with vehicle, ^*P<0.05 compared with drug control. (D) TGFβ1 induces phosphorylation of p38 MAPK and p42/p44 MAPK in human podocytes was inhibited by SB203580 and PD98059, respectively.