Inhibition of caspase-9 through phosphorylation at Thr 125 by ERK MAPK

Nat Cell Biol. 2003 Jul;5(7):647-54. doi: 10.1038/ncb1005.

Abstract

Many pro-apoptotic signals activate caspase-9, an initiator protease that activates caspase-3 and downstream caspases to initiate cellular destruction. However, survival signals can impinge on this pathway and suppress apoptosis. Activation of the Ras-Raf-MEK-ERK mitogen-activated protein kinase (MAPK) pathway is associated with protection of cells from apoptosis and inhibition of caspase-3 activation, although the targets are unknown. Here, we show that the ERK MAPK pathway inhibits caspase-9 activity by direct phosphorylation. In mammalian cell extracts, cytochrome c-induced activation of caspases-9 and -3 requires okadaic-acid-sensitive protein phosphatase activity. The opposing protein kinase activity is overcome by treatment with the broad-specificity kinase inhibitor staurosporine or with inhibitors of MEK1/2. Caspase-9 is phosphorylated at Thr 125, a conserved MAPK consensus site targeted by ERK2 in vitro, in a MEK-dependent manner in cells stimulated with epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol-13-acetate (TPA). Phosphorylation at Thr 125 is sufficient to block caspase-9 processing and subsequent caspase-3 activation. We suggest that phosphorylation and inhibition of caspase-9 by ERK promotes cell survival during development and tissue homeostasis. This mechanism may also contribute to tumorigenesis when the ERK MAPK pathway is constitutively activated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Base Sequence / genetics
  • Caspase 3
  • Caspase 9
  • Caspases / metabolism*
  • Cell Survival / drug effects
  • Cell Survival / physiology*
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / metabolism*
  • Cytochrome c Group / drug effects
  • Cytochrome c Group / metabolism
  • Enzyme Inhibitors / pharmacology
  • Epidermal Growth Factor / pharmacology
  • Eukaryotic Cells / drug effects
  • Eukaryotic Cells / enzymology*
  • HeLa Cells
  • Humans
  • MAP Kinase Kinase 1
  • Mice
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism*
  • Molecular Sequence Data
  • Phosphorylation / drug effects
  • Protein-Serine-Threonine Kinases / metabolism
  • Pyridines / pharmacology
  • Recombinant Fusion Proteins
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Threonine / metabolism

Substances

  • Cytochrome c Group
  • Enzyme Inhibitors
  • Pyridines
  • Recombinant Fusion Proteins
  • tris(2-pyridylmethyl)amine
  • Threonine
  • Epidermal Growth Factor
  • Protein-Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 1
  • MAP2K1 protein, human
  • Map2k1 protein, mouse
  • Mitogen-Activated Protein Kinase Kinases
  • CASP3 protein, human
  • CASP9 protein, human
  • Casp3 protein, mouse
  • Casp9 protein, mouse
  • Caspase 3
  • Caspase 9
  • Caspases