title: Multiple signaling pathways mediate LIF-induced skeletal muscle satellite cell proliferation.
abstract: There are many known growth factors/cytokines that induce skeletal muscle satellite cell proliferation. Currently, the signaling mechanisms in which these growth factors/cytokines activate satellite cell proliferation are not completely understood. Here, we sought to determine signaling mechanisms by which leukemia inhibitory factor (LIF) induces satellite cell proliferation in culture. First, we confirmed that LIF induces proliferation of C2C12 immortalized myoblasts and cultured primary rat satellite cells. In addition, we also found that this increase in proliferation can be inhibited by incubation of the cells in tyrphostin AG 490, a specific inhibitor of Janus-activated kinase (JAK) 2 activity. Furthermore, we also found that incubation of the cells at various time points with LIF (10 ng/ml) induces a significant, transient increase in JAK2 phosphorylation, signal transducers and activators of transcription (STAT3) phosphorylation, and STAT3 transcriptional activity. Increases in the STAT3-sensitive endogenous SOC3 protein followed these transient increases in STAT3 activation. In addition, AG 490 inhibited the increase in STAT3 phosphorylation. Finally, LIF did not change the phosphorylation status of extracellular signal-regulated protein kinase (ERK)1/2 or affect the phosphorylation status of Akt/protein kinase B. However, LY-294002, an inhibitor of phosphoinositide 3-kinase, blocked LIF-induced proliferation of satellite cells. These data suggest that LIF induces satellite cell proliferation by activation of the JAK2-STAT3 signaling pathway, suggesting that this may be an important pathway in muscle growth and/or hypertrophy.
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
authors.forename: Espen E
authors.initials: EE
authors.lastname: Spangenburg
authors.forename: Frank W
authors.initials: FW
authors.lastname: Booth
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006131:Growth Inhibitors / Q000502:physiology*; D015850:Interleukin-6; D053614:Janus Kinase 2; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000502:physiology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D050796:STAT3 Transcription Factor; D027161:Satellite Cells, Perineuronal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D015534:Trans-Activators; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D011505:Protein-Tyrosine Kinases; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases