Endothelial nitric oxide synthase is involved in calcium-induced Akt signaling in mouse skeletal muscle
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- 作者：Jason A. Drenning ; Vitor A. Lira ; Quinlyn A. Soltow ; Claire N. Canon ; Lauren M. Valera ; Dana L. Brown ; David S. Criswell
- 关键词：Nitric oxide ; Skeletal muscle ; Myotubes ; Protein kinase B ; Fiber type
- 刊名：Nitric Oxide
- 出版年：2009
- 出版时间：15 December 2009
- 年：2009
- 卷：21
- 期：3-4
- 页码：192-200
- 全文大小：941 K
文摘
We hypothesized that targeted mutation of the endothelial nitric oxide synthase (eNOS) gene would reduce Akt-related signaling events in skeletal muscle cells, compared to wild type (WT) controls. Results show that slow myosin heavy chain (type I/β) expression and the abundance of slow-twitch fibers are reduced in plantaris muscle of eNOS−/− mice, compared to WT. Further, basal phosphorylation of Akt (p-Akt (Ser-473)/total Akt) and GSK-3β (GSK-3β (Ser-9)/total GSK-3β) are reduced 60–70 % in primary myotubes from eNOS−/− mice. Treatment with the calcium ionophore, A23187 (0.4 μM, 1 h), increased phosphorylation of Akt and GSK-3β by 2-fold (P < 0.05) in myotubes from WT mice, but had no effect on phosphorylation of these proteins in eNOS−/− myotubes. Additionally, A23187 treatment failed to induce nuclear translocation of the transcription factor, NFATc1, in eNOS−/− myotubes. Treatment with the nitric oxide donor, propylamine propylamine NONOate (PAPA-NO; 1 μM for 1 h) increased Akt and GSK-3β phosphorylation, and induced NFATc1 nuclear translocation in WT and eNOS−/− myotubes, and eliminated differences from WT in the NOS knockout cultures. Parallel experiments in C2C12 myotubes found that Akt phosphorylation induced by NO or the guanylate cyclase activator, YC-1, is prevented by co-treatment with either a guanylate cyclase or PI3K inhibitor (10 μM ODQ or 25 μM LY2904002, respectively). These data suggest that eNOS activity is necessary for calcium-induced activation of the Akt pathway, and that nitric oxide is sufficient to elevate Akt activity in primary myotubes. NO appears to influence Akt signaling through a cGMP, PI3K-dependent pathway.