Direct inhibition of the signaling functions of the mammalian target of rapamycin by the phosphoinositide 3-kinase inhibitors, wortmannin and LY294002

EMBO J. 1996 Oct 1;15(19):5256-67.

Abstract

The immunosuppressant, rapamycin, inhibits cell growth by interfering with the function of a novel kinase, termed mammalian target of rapamycin (mTOR). The putative catalytic domain of mTOR is similar to those of mammalian and yeast phosphatidylinositol (PI) 3-kinases. This study demonstrates that mTOR is a component of a cytokine-triggered protein kinase cascade leading to the phosphorylation of the eukaryotic initiation factor-4E (eIF-4E) binding protein, PHAS-1, in activated T lymphocytes. This event promotes G1 phase progression by stimulating eIF-4E-dependent translation initiation. A mutant YAC-1 T lymphoma cell line, which was selected for resistance to the growth-inhibitory action of rapamycin, was correspondingly resistant to the suppressive effect of this drug on PHAS-1 phosphorylation. In contrast, the PI 3-kinase inhibitor, wortmannin, reduced the phosphorylation of PHAS-1 in both rapamycin-sensitive and -resistant T cells. At similar drug concentrations (0.1-1 microM), wortmannin irreversibly inhibited the serine-specific autokinase activity of mTOR. The autokinase activity of mTOR was also sensitive to the structurally distinct PI 3-kinase inhibitor, LY294002, at concentrations (1-30 microM) nearly identical to those required for inhibition of the lipid kinase activity of the mammalian p85-p110 heterodimer. These studies indicate that the signaling functions of mTOR, and potentially those of other high molecular weight PI 3-kinase homologs, are directly affected by cellular treatment with wortmannin or LY294002.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / pharmacology
  • Androstadienes / pharmacology*
  • Animals
  • Brain Chemistry
  • Carrier Proteins*
  • Cell Cycle Proteins
  • Cell Line
  • Chromones / pharmacology*
  • Dithiothreitol / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Eukaryotic Initiation Factors
  • Immunosuppressive Agents / pharmacology
  • Interleukin-2 / pharmacology
  • Intracellular Signaling Peptides and Proteins
  • Lymphocyte Activation
  • Lymphoma, T-Cell
  • Mice
  • Morpholines / pharmacology*
  • Phosphatidylinositol 3-Kinases
  • Phosphoproteins / metabolism*
  • Phosphorylation / drug effects
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors*
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / isolation & purification
  • Polyenes / pharmacology
  • Protein Kinases*
  • Rats
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / drug effects
  • Sirolimus
  • T-Lymphocytes / immunology
  • T-Lymphocytes, Cytotoxic
  • TOR Serine-Threonine Kinases
  • Tumor Cells, Cultured
  • Wortmannin

Substances

  • Androstadienes
  • Carrier Proteins
  • Cell Cycle Proteins
  • Chromones
  • Eif4ebp1 protein, mouse
  • Eif4ebp1 protein, rat
  • Enzyme Inhibitors
  • Eukaryotic Initiation Factors
  • Immunosuppressive Agents
  • Interleukin-2
  • Intracellular Signaling Peptides and Proteins
  • Morpholines
  • Phosphoproteins
  • Polyenes
  • Recombinant Fusion Proteins
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • adenosine 5'-O-(3-thiotriphosphate)
  • Adenosine Triphosphate
  • Protein Kinases
  • Phosphotransferases (Alcohol Group Acceptor)
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • mTOR protein, rat
  • Dithiothreitol
  • Sirolimus
  • Wortmannin