N-myristoylated ubiquitin ligase Cbl-b inhibitor prevents on glucocorticoid-induced atrophy in mouse skeletal muscle

Arch Biochem Biophys. 2015 Mar 15:570:23-31. doi: 10.1016/j.abb.2015.02.006. Epub 2015 Feb 14.


A DGpYMP peptide mimetic of tyrosine(608)-phosphorylated insulin receptor substrate-1 (IRS-1), named Cblin, was previously shown to significantly inhibit Cbl-b-mediated IRS-1 ubiquitination. In the present study, we developed N-myristoylated Cblin and investigated whether it was effective in preventing glucocorticoid-induced muscle atrophy. Using HEK293 cells overexpressing Cbl-b, IRS-1 and ubiquitin, we showed that the 50% inhibitory concentrations of Cbl-b-mediated IRS-1 ubiquitination by N-myristoylated Cblin and Cblin were 30 and 120 μM, respectively. Regarding the DEX-induced atrophy of C2C12 myotubes, N-myristoylated Cblin was more effective than Cblin for inhibiting the DEX-induced decreases in C2C12 myotube diameter and IRS-1 degradation. The inhibitory efficacy of N-myristoylated Cblin on IRS-1 ubiquitination in C2C12 myotubes was approximately fourfold larger than that of Cblin. Furthermore, N-myristoylation increased the incorporation of Cblin into HEK293 cells approximately 10-folds. Finally, we demonstrated that N-myristoylated Cblin prevented the wet weight loss, IRS-1 degradation, and MAFbx/atrogin-1 and MuRF-1 expression in gastrocnemius muscle of DEX-treated mice approximately fourfold more effectively than Cblin. Taken together, these results suggest that N-myristoylated Cblin prevents DEX-induced skeletal muscle atrophy in vitro and in vivo, and that N-myristoylated Cblin more effectively prevents muscle atrophy than unmodified Cblin.

Keywords: Cbl-b; IRS-1; Mice; Skeletal muscle atrophy; Ubiquitin ligase inhibitor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / antagonists & inhibitors
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Cell-Free System
  • Female
  • Glucocorticoids / adverse effects*
  • HEK293 Cells
  • Humans
  • Insulin Receptor Substrate Proteins / chemistry
  • Mice
  • Mice, Inbred C57BL
  • Muscle Fibers, Skeletal / metabolism
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism*
  • Muscular Atrophy / chemically induced
  • Myristic Acid / chemistry
  • Peptides / chemistry*
  • Proto-Oncogene Proteins c-cbl / antagonists & inhibitors
  • Proto-Oncogene Proteins c-cbl / metabolism*
  • Ubiquitin / chemistry


  • Adaptor Proteins, Signal Transducing
  • Cblb protein, mouse
  • Glucocorticoids
  • IRS1 protein, human
  • Insulin Receptor Substrate Proteins
  • Irs1 protein, mouse
  • Peptides
  • Ubiquitin
  • Myristic Acid
  • CBLB protein, human
  • Proto-Oncogene Proteins c-cbl