Insulin-like growth factor-II, phosphatidylinositol 3-kinase, nuclear factor-kappaB and inducible nitric-oxide synthase define a common myogenic signaling pathway.
Insulin-like growth factors (IGFs) are potent inducers of skeletal muscle differentiation and phosphatidylinositol (PI) 3-kinase activity is essential for this process. Here we show that IGF-II induces nuclear factor-kappaB (NF-kappaB) and nitric-oxide synthase (NOS) activities downstream from PI 3-kinase and that these events are critical for myogenesis. Differentiation of rat L6E9 myoblasts with IGF-II transiently induced NF-kappaB DNA binding activity, inducible nitric-oxide synthase (iNOS) expression, and nitric oxide (NO) production. IGF-II-induced iNOS expression and NO production were blocked by NF-kappaB inhibition. Both NF-kappaB and NOS activities were essential for IGF-II-induced terminal differentiation (myotube formation and expression of skeletal muscle proteins: myosin heavy chain, GLUT 4, and caveolin 3), which was totally blocked by NF-kappaB or NOS inhibitors in rat and human myoblasts. Moreover, the NOS substrate L-Arg induced myogenesis in the absence of IGFs in both rat and human myoblasts, and this effect was blocked by NOS inhibition. Regarding the mechanisms involved in IGF-II activation of NF-kappaB, PI 3-kinase inhibition prevented NF-kappaB activation, iNOS expression, and NO production. Moreover, IGF-II induced, through a PI 3-kinase-dependent pathway, a decrease in IkappaB-alpha protein content that correlated with a decrease in the amount of IkappaB-alpha associated with p65 NF-kappaB.
Kaliman
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P
Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona, Spain. perlak@porthos.bio.ub.es
Canicio
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Testar
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Palacín
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Zorzano
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D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020672:I-kappa B Proteins; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D019335:Nitroarginine / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011392:Proline / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction; D013859:Thiocarbamates / Q000494:pharmacology
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D009124:Muscle Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; D013859:Thiocarbamates; C066229:prolinedithiocarbamate; D000072000:NF-KappaB Inhibitor alpha; D019335:Nitroarginine; D009569:Nitric Oxide; D007335:Insulin-Like Growth Factor II; D001120:Arginine; D011392:Proline; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D019869:Phosphatidylinositol 3-Kinases