Intracellular signal transduction pathways induced by leptin in C2C12 cells.
As experimental evidence suggests that leptin may have direct effects on peripheral tissues, we investigated some of the transductional molecules induced by leptin in C2C12 cells. In immunoprecipitation experiments using anti-p85 antibodies (a regulatory subunit of phosphatidylinositol-3-kinase; PI3K), we observed a significant increase in PI3K activity. Immunoblot analyses showed that Akt, GSK3, ERK1, ERK2, and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation significantly increased after leptin treatment. Protein kinase C (PKC)-zeta was also activated by leptin, as documented by an immunocomplex kinase assay and immunoblotting experiments. The treatment of C2C12 cells with Wortmannin before leptin administration inhibited induction of the phosphorylation of ERKs (extracellular signal-regulated kinases) but not that of p38 MAPK, whereas pre-treatment with a PKC-zeta inhibitor partially decreased ERK phosphorylation. Taken together, our in vitro results further support the hypothesis that leptin acts acutely on skeletal muscle tissue through some of the components of insulin signalling, including PKC-zeta.
Maroni
Paola
P
Istituto di Patologia Generale, Università degli Studi di Milano, Via Mangiagalli, 31 20133 Milano, Italy.
Bendinelli
Paola
P
Piccoletti
Roberta
R
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D051379:Mice; D032446:Myoblasts / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000730:Androstadienes; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3; D020738:Leptin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases