FIG 4.

Inhibiting STAT3 activity reduces SH2B1β-enhanced EGR1 expression and neurite outgrowth. (A) PC12-GFP and PC12-SH2B1β cells were incubated in serum-free medium overnight before being treated with DMSO (−) or with the STAT3 inhibitor STA-21 (20 μM) (+) for 24 h, and then 100 ng/ml FGF1 was added for 2 h. Cell lysates were collected, and equal amounts of proteins were separated by SDS-PAGE and immunoblotted with anti-EGR1, anti-pSTAT3(S727), and anti-STAT3 antibodies. EGR1 expression was normalized to STAT3 levels. Values are the means ± SEM from three independent experiments. (B) PC12-SH2B1β cells were preincubated with DMSO or 20 μM STA-21 for 1 h and then were left untreated or treated with 100 ng/ml FGF1 for 4 days. Live-cell images are shown. Scale bar, 50 μm. (C) The average neurite length of PC12-SH2B1β cells on differentiation day 4 was calculated from three independent experiments. *, P < 0.05 by paired Student's t test.