Methyltransferase-like 21e inhibits 26S proteasome activity to facilitate hypertrophy of type IIb myofibers

FASEB J. 2019 Aug;33(8):9672-9684. doi: 10.1096/fj.201900582R. Epub 2019 Jun 4.


Skeletal muscles contain heterogeneous myofibers that are different in size and contractile speed, with type IIb myofiber being the largest and fastest. Here, we identify methyltransferase-like 21e (Mettl21e), a member of newly classified nonhistone methyltransferases, as a gene enriched in type IIb myofibers. The expression of Mettl21e was strikingly up-regulated in hypertrophic muscles and during myogenic differentiation in vitro and in vivo. Knockdown (KD) of Mettl21e led to atrophy of cultured myotubes, and targeted mutation of Mettl21e in mice reduced the size of IIb myofibers without affecting the composition of myofiber types. Mass spectrometry and methyltransferase assay revealed that Mettl21e methylated valosin-containing protein (Vcp/p97), a key component of the ubiquitin-proteasome system. KD or knockout of Mettl21e resulted in elevated 26S proteasome activity, and inhibition of proteasome activity prevented atrophy of Mettl21e KD myotubes. These results demonstrate that Mettl21e functions to maintain myofiber size through inhibiting proteasome-mediated protein degradation.-Wang, C., Zhang, B., Ratliff, A. C., Arrington, J., Chen, J., Xiong, Y., Yue, F., Nie, Y., Hu, K., Jin, W., Tao, W. A., Hrycyna, C. A., Sun, X., Kuang, S. Methyltransferase-like 21e inhibits 26S proteasome activity to facilitate hypertrophy of type IIb myofibers.

Keywords: Mettl21e; Myostatin; VCP/p97; muscle atrophy; non-histone methylation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Bortezomib / therapeutic use
  • Cell Differentiation / drug effects*
  • Cell Differentiation / genetics
  • Cells, Cultured
  • Female
  • Immunoprecipitation
  • Methyltransferases / genetics
  • Methyltransferases / metabolism*
  • Mice
  • Mice, Knockout
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / metabolism
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / metabolism
  • Muscular Atrophy / metabolism*
  • Muscular Atrophy / pathology
  • Mutation / genetics
  • Myoblasts / drug effects
  • Myoblasts / metabolism
  • Myofibrils / drug effects
  • Myofibrils / metabolism*
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism
  • Real-Time Polymerase Chain Reaction
  • Sequence Analysis, RNA


  • Bortezomib
  • Methyltransferases
  • Proteasome Endopeptidase Complex
  • ATP dependent 26S protease