bFGF and LIF signaling activates STAT3 in proliferating myoblasts.
Different mitogens elicit similar effects on growth and differentiation of skeletal muscle, suggesting that potential overlap exists in the signaling cascades activated by such factors. To investigate this possibility, we examined the status of STAT and ERK proteins in C2C12 myoblasts and myotubes following stimulation with bFGF or LIF. Both STAT1 and STAT3 as well as ERK1 and ERK2 proteins were detectable in extracts of myoblasts. LIF stimulation of myoblasts lead to rapid phosphorylation on tyrosine of STAT3 and of ERKs 1 and 2. Similarly, bFGF stimulation of myoblasts resulted in the tyrosine phosphorylation of STAT3. However, unlike LIF, the bFGF induced tyrosine phosphorylation of STAT3 appeared cyclical, with recurrent peaks of phosphorylation even after prolonged exposure. By contrast, STAT1 remained unphosphorylated in myoblasts treated with bFGF or LIF. In differentiated myotubes, LIF treatment resulted in the tyrosine phosphorylation of both STAT3 and STAT1, but ERK phosphorylation was not detectable, and bFGF treatment did not lead to STAT1 or STAT3 tyrosine phosphorylation. Therefore these observations suggest that disparate mitogens car activate similar downstream effectors in proliferating myoblasts.
Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada.
L A
LA
Megeney
R L
RL
Perry
J E
JE
LeCouter
M A
MA
Rudnicki
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000494:pharmacology*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D008934:Mitogens / Q000494:pharmacology; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*
D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D008222:Lymphokines; D008934:Mitogens; D009124:Muscle Proteins; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D016222:Fibroblast Growth Factor 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases