Tumor necrosis factor‐alpha inhibits myogenic differentiation through MyoD protein destabilization

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Abstract
Tumor necrosis factor α (TNFα) has been implicated as a mediator of muscle wasting through nuclear factor kappa B (NF-κB) -dependent inhibition of myogenic differentiation. The aim of the present study was to identify the regulatory molecule(s) of myogenesis targeted by TNFα/NF-κB signaling. TNFα interfered with cell cycle exit and repressed the accumulation of transcripts encoding muscle-specific genes in differentiating C2C12 myoblasts. Overexpression of a p65 (RelA) mutant lacking the transcriptional activation domain attenuated the TNFα-mediated inhibition of muscle-specific gene transcription. The ability of muscle regulatory factor MyoD to induce muscle-specific transcription in 10T1/2 fibroblasts was also disrupted by wild-type p65, demonstrating that NF-κB transcriptional activity interferes with the function of MyoD. Inhibition of muscle-specific gene expression by TNFα was restored by overexpression of MyoD, whereas endogenous MyoD protein abundance and stability were reduced by TNFα through increased proteolysis of MyoD by the ubiquitin proteasome pathway. Last, the inhibitory effects of TNFα on myogenic differentiation were demonstrated in a mouse model of skeletal muscle regeneration, in which TNFα caused a delay in myoblast cell cycle exit. These results implicate that TNFα inhibits myogenic differentiation through destabilizing MyoD protein in a NF-κB-dependent manner, which interferes with skeletal muscle regeneration and may contribute to muscle wasting.—Langen, R. C. J., van der Velden, J. L. J., Schols, A. M. W. J., Kelders, M. C. J. M., Wouters, E. F. M., Janssen-Heininger, Y. M. W. Tumor necrosis factor-alpha inhibits myogenic differentiation through MyoD protein destabilization.