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Differential regulation of MAP kinase, p70S6K, and Akt by contraction and insulin in rat skeletal muscle

Differential regulation of MAP kinase, p70S6K, and Akt by contraction and insulin in rat skeletal... Abstract To study the effects of contractile activity on mitogen-activated protein kinase (MAP kinase), p70 S6 kinase (p70 S6K ), and Akt kinase signaling in rat skeletal muscle, hindlimb muscles were contracted by electrical stimulation of the sciatic nerve for periods of 15 s to 60 min. Contraction resulted in a rapid and transient activation of Raf-1 and MAP kinase kinase 1, a rapid and more sustained activation of MAP kinase and the 90-kDa ribosomal S6 kinase 2, and a dramatic increase in c- fos mRNA expression. Contraction also resulted in an apparent increase in the association of Raf-1 with p21Ras, although stimulation of MAP kinase signaling occurred independent of Shc, IRS1, and IRS2 tyrosine phosphorylation or the formation of Shc/Grb2 or IRS1/Grb2 complexes. Insulin was considerably less effective than contraction in stimulating the MAP kinase pathway. However, insulin, but not contraction, increased p70 S6K and Akt activities in the muscle. These results demonstrate that contraction-induced activation of the MAP kinase pathway is independent of proximal steps in insulin and/or growth factor-mediated signaling, and that contraction and insulin have discordant effects with respect to the activation of the MAP kinase pathway vs. p70 S6K and Akt. Of the numerous stimulators of MAP kinase in skeletal muscle, contractile activity emerges as a potent and physiologically relevant activator of MAP kinase signaling, and thus activation of this pathway is likely to be an important molecular mechanism by which skeletal muscle cells transduce mechanical and/or biochemical signals into downstream biological responses. signal transduction muscle contraction exercise Footnotes This work was supported by National Institute on Aging Grant AR-42238 and a grant from the Juvenile Diabetes Foundation International (both to L. J. Goodyear). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 1999 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Endocrinology and Metabolism The American Physiological Society

Differential regulation of MAP kinase, p70S6K, and Akt by contraction and insulin in rat skeletal muscle

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Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0193-1849
eISSN
1522-1555
Publisher site
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Abstract

Abstract To study the effects of contractile activity on mitogen-activated protein kinase (MAP kinase), p70 S6 kinase (p70 S6K ), and Akt kinase signaling in rat skeletal muscle, hindlimb muscles were contracted by electrical stimulation of the sciatic nerve for periods of 15 s to 60 min. Contraction resulted in a rapid and transient activation of Raf-1 and MAP kinase kinase 1, a rapid and more sustained activation of MAP kinase and the 90-kDa ribosomal S6 kinase 2, and a dramatic increase in c- fos mRNA expression. Contraction also resulted in an apparent increase in the association of Raf-1 with p21Ras, although stimulation of MAP kinase signaling occurred independent of Shc, IRS1, and IRS2 tyrosine phosphorylation or the formation of Shc/Grb2 or IRS1/Grb2 complexes. Insulin was considerably less effective than contraction in stimulating the MAP kinase pathway. However, insulin, but not contraction, increased p70 S6K and Akt activities in the muscle. These results demonstrate that contraction-induced activation of the MAP kinase pathway is independent of proximal steps in insulin and/or growth factor-mediated signaling, and that contraction and insulin have discordant effects with respect to the activation of the MAP kinase pathway vs. p70 S6K and Akt. Of the numerous stimulators of MAP kinase in skeletal muscle, contractile activity emerges as a potent and physiologically relevant activator of MAP kinase signaling, and thus activation of this pathway is likely to be an important molecular mechanism by which skeletal muscle cells transduce mechanical and/or biochemical signals into downstream biological responses. signal transduction muscle contraction exercise Footnotes This work was supported by National Institute on Aging Grant AR-42238 and a grant from the Juvenile Diabetes Foundation International (both to L. J. Goodyear). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 1999 the American Physiological Society

Journal

AJP - Endocrinology and Metabolism – The American Physiological Society

Published: May 1, 1999

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