MAPK phosphatase-1 facilitates the loss of oxidative myofibers associated with obesity in mice
Rachel J. Roth, … , Gerald I. Shulman, Anton M. Bennett
Rachel J. Roth, … , Gerald I. Shulman, Anton M. Bennett
Published November 16, 2009
Citation Information: J Clin Invest. 2009;119(12):3817-3829. https://doi.org/10.1172/JCI39054.
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Research Article Metabolism

MAPK phosphatase-1 facilitates the loss of oxidative myofibers associated with obesity in mice

Abstract

Oxidative myofibers, also known as slow-twitch myofibers, help maintain the metabolic health of mammals, and it has been proposed that decreased numbers correlate with increased risk of obesity. The transcriptional coactivator PPARγ coactivator 1α (PGC-1α) plays a central role in maintaining levels of oxidative myofibers in skeletal muscle. Indeed, loss of PGC-1α expression has been linked to a reduction in the proportion of oxidative myofibers in the skeletal muscle of obese mice. MAPK phosphatase-1 (MKP-1) is encoded by mkp-1, a stress-responsive immediate-early gene that dephosphorylates MAPKs in the nucleus. Previously we showed that mice deficient in MKP-1 have enhanced energy expenditure and are resistant to diet-induced obesity. Here we show in mice that excess dietary fat induced MKP-1 overexpression in skeletal muscle, and that this resulted in reduced p38 MAPK–mediated phosphorylation of PGC-1α on sites that promoted its stability. Consistent with this, MKP-1–deficient mice expressed higher levels of PGC-1α in skeletal muscle than did wild-type mice and were refractory to the loss of oxidative myofibers when fed a high-fat diet. Collectively, these data demonstrate an essential role for MKP-1 as a regulator of the myofiber composition of skeletal muscle and suggest a potential role for MKP-1 in metabolic syndrome.

Authors

Rachel J. Roth, Annie M. Le, Lei Zhang, Mario Kahn, Varman T. Samuel, Gerald I. Shulman, Anton M. Bennett

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Figure 6

MKP-1 antagonizes PGC-1α phosphorylation and protein stability.

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MKP-1 antagonizes PGC-1α phosphorylation and protein stability. (A) Flag...
(A) Flag-tagged PGC-1α, MKK6EE, MKK7DD, and MKP-1 (10 μg) were transfected into C2C12 myoblasts. Myoblasts were lysed 24 hours later and immunoblotted with PGC-1α, MKP-1, phospho-p38 MAPK, p38 MAPK, phospho-JNK, and JNK antibodies. (B) Flag-tagged PGC-1α was transfected into C2C12 myoblasts along with nontargeting siRNA or MKP-1 siRNA as described in Figure 5B, and pulse-chase metabolic labeling with 35S methionine/cysteine was performed. Densitometric analyses were quantitated as the amount of PGC-1α remaining relative to time 0. The mean t1/2 was calculated from the linear regression derived from 3 independent experiments (nontargeting siRNA, 56.7 minutes; MKP-1 siRNA, 83.5 minutes; P < 0.05). Data are mean ± SEM. (C) Flag-tagged PGC-1α as well as Flag-tagged PGC-1α Ser265A and Thr298A mutants were transfected into C2C12 myoblasts with MKK6EE. Myoblasts were lysed, and PGC-1α was immunoprecipitated with anti-Flag antibodies and immunoblotted with total PGC-1α, phospho-Ser265 PGC-1α, or phospho-Thr298 PGC-1α antibodies. Lanes were run on the same gel but were noncontiguous (white line). (D) Flag-PGC-1α, MKK6EE, and MKP-1 (2 μg) were transfected into C2C12 myoblasts. Myoblasts were lysed, and PGC-1α was immunoprecipitated with anti-Flag antibodies and immunoblotted as in C. Graphs show densitometric measurements of phospho-Ser265 PGC-1α and phospho-Thr298 PGC-1α normalized to total PGC-1α from 3 independent experiments. Data are mean ± SEM. (E) Flag-tagged PGC-1α was transfected into C2C12 myoblasts along with 50 nM nontargeting or MKP-1 siRNA. Myoblasts were starved for 2 hours prior to stimulation with 10 ng/ml TNF-α and 2 ng/ml IL-1β for the indicated times. Myoblasts were lysed, and PGC-1α was immunoprecipitated with anti-Flag antibodies and immunoblotted as in C.