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. 2004 Apr 19;101(17):6728–6733. doi: 10.1073/pnas.0307606100

Fig. 3.

Fig. 3.

Inhibition of Cdk5 activity abolished the NRG-induced Ser phosphorylation of STAT3. (A) Blockade of STAT3 activity and Cdk5 activity attenuated the NRG-induced c-fos transcription. Northern blot analysis of c-fos transcript after treatment of C2C12 myotubes with NRG (+) for 30 min. The myotubes were pretreated with different inhibitors: 40 μM Ros, 100 μM AG490 for 4 h, or 100 μM STAT3-inhibitory peptide (STAT3 peptide) for 24 h as indicated. (B) Cultured C2C12 myotubes were treated with NRG for 0-30 min. Total cell lysates were subjected to Western blot analysis using Abs specific for P-Ser STAT3, P-Tyr STAT3, and total STAT3 (Upper). Induction of P-ERKs served as positive control for NRG treatment (Lower). (C) Inhibition of Cdk5 activity with Ros abolished the NRG-induced P-Ser STAT3. -, untreated; +, NRG-treated for 15 min. DMSO served as control. (D) Expression of dnCdk5 in C2C12 myotubes attenuated the NRG-induced P-Ser STAT3. (E) Cultured C2C12 myotubes were treated with NRG for 0-30 min with or without Ros pretreatment. Lysates of nuclear (Left) or cytoplasmic (Right) fractions were prepared and were immunoblotted with specific Abs as depicted.