MNK1-induced eIF-4E phosphorylation in myeloma cells: a pathway mediating IL-6-induced expansion and expression of genes involved in metabolic and proteotoxic responses

PLoS One. 2014 Apr 8;9(4):e94011. doi: 10.1371/journal.pone.0094011. eCollection 2014.

Abstract

Because multiple myeloma (MM) cells are at risk for endoplasmic reticulum (ER) stress, they require a carefully regulated mechanism to promote protein translation of selected transcripts when proliferation is stimulated. MAPK-interacting kinases (MNKs) may provide this mechanism by enhancing cap-dependent translation of a small number of critical transcripts. We, thus, tested whether MNKs played a role in MM responses to the myeloma growth factor interleukin-6 (IL-6). IL-6 activated MNK1 phosphorylation and induced phosphorylation of its substrate, eIF-4E, in MM lines and primary specimens. MNK paralysis, achieved pharmacologically or by shRNA, prevented MM expansion stimulated by IL-6. A phosphodefective eIF-4E mutant also prevented the IL-6 response, supporting the notion that MNK's role was via phosphorylation of eIF-4E. Both pharmacological MNK inhibition and expression of the phosphodefective eIF-4E mutant inhibited MM growth in mice. Although critical for IL-6-induced expansion, eIF-4E phosphorylation had no significant effect on global translation or Ig expression. Deep sequencing of ribosome-protected mRNAs revealed a repertoire of genes involved in metabolic processes and ER stress modulation whose translation was regulated by eIF-4E phosphorylation. These data indicate MM cells exploit the MNK/eIF-4E pathway for selective mRNA translation without enhancing global translation and risking ER stress.

Publication types

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

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Endoplasmic Reticulum Stress
  • Eukaryotic Initiation Factor-4E / metabolism*
  • Humans
  • Interleukin-6 / metabolism*
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Mice
  • Multiple Myeloma / metabolism*
  • Phosphorylation
  • Protein Biosynthesis
  • Protein Serine-Threonine Kinases / metabolism*

Substances

  • Eukaryotic Initiation Factor-4E
  • Interleukin-6
  • Intracellular Signaling Peptides and Proteins
  • MKNK1 protein, human
  • Protein Serine-Threonine Kinases