Figure 4
β3 Integrin enhances MAPK activation by TGF-β in NMuMG cells. (a) Control or β3 integrin expressing NMuMG cells were serum starved for 4 hours prior to TGF-β1 stimulation (5 ng/ml) for 0–120 min. Afterward, the activation status of Smad2, ERK1/2, and p38 MAPK was determined by immunoblot analysis using phospho-specific antibodies. Reprobing stripped membranes with anti-ERK1/2 antibodies monitored differences in protein loading. (b) Control or β3 integrin-expressing NMuMG cells were serum starved for 4 hours before stimulation with TGF-β1 (5 ng/ml), prolactin (100 ng/ml), PMA (10 ng/ml), or EGF (100 ng/ml) for 30 min. Afterward, the activation status of p38 MAPK was determined by immunoblot analysis using phospho-specific antibodies. Reprobing stripped membranes with anti-pan p38 MAPK antibodies was used to monitor differences in protein loading. Accompanying graphs depict the mean (± standard error) fold increase of p38 MAPK stimulation observed in three independent experiments (*P < 0.05). EGF, epidermal growth factor; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; PMA, 4α-phorbol 12-myristate 13-acetate; TGF, transforming growth factor.