Inactivation of the mTORC1-eukaryotic translation initiation factor 4E pathway alters stress granule formation

Mol Cell Biol. 2013 Jun;33(11):2285-301. doi: 10.1128/MCB.01517-12. Epub 2013 Apr 1.

Abstract

Stress granules (SG) are cytoplasmic multimeric RNA bodies that form under stress conditions known to inhibit cap-dependent translation. SG contain translation initiation factors, RNA binding proteins, and signaling molecules. SG are known to inhibit apoptotic pathways, thus contributing to chemo- and radioresistance in tumor cells. However, whether stress granule formation involves oncogenic signaling pathways is currently unknown. Here, we report a novel role of the mTORC1-eukaryotic translation initiation factor 4E (eIF4E) pathway, a key regulator of cap-dependent translation initiation of oncogenic factors, in SG formation. mTORC1 specifically drives the eIF4E-mediated formation of SG through the phosphorylation of 4E-BP1, a key factor known to inhibit formation of the mTORC1-dependent eIF4E-eIF4GI interactions. Disrupting formation of SG by inactivation of mTOR with its specific inhibitor pp242 or by depletion of eIF4E or eIF4GI blocks the SG-associated antiapoptotic p21 pathway. Finally, pp242 sensitizes cancer cells to death in vitro and inhibits the growth of chemoresistant tumors in vivo. This work therefore highlights a novel role of the oncogenic mTORC1-eIF4E pathway, namely, the promotion of formation of antiapoptotic SG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Boronic Acids / pharmacology
  • Bortezomib
  • Cell Cycle Proteins
  • Chick Embryo
  • Cytoplasmic Granules / metabolism*
  • Eukaryotic Initiation Factor-4E / genetics
  • Eukaryotic Initiation Factor-4E / metabolism*
  • HeLa Cells / drug effects
  • Humans
  • Indoles / pharmacology
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Purines / pharmacology
  • Pyrazines / pharmacology
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Boronic Acids
  • Cell Cycle Proteins
  • EIF4EBP1 protein, human
  • Eukaryotic Initiation Factor-4E
  • Indoles
  • Multiprotein Complexes
  • Phosphoproteins
  • Purines
  • Pyrazines
  • Bortezomib
  • MTOR protein, human
  • Mechanistic Target of Rapamycin Complex 1
  • TOR Serine-Threonine Kinases
  • PP242