PP1/PP2A phosphatases inhibitors okadaic acid and calyculin A block ERK5 activation by growth factors and oxidative stress

FEBS Lett. 2002 Jul 17;523(1-3):90-4. doi: 10.1016/s0014-5793(02)02950-2.


Okadaic acid is an inhibitor of the protein Ser/Thr phosphatases PP1 and PP2A, which blocks the activation of extracellular signal-regulated protein kinase 5 (ERK5), a member of the MAP kinase family activated by growth factors and several types of stressors. The blocking of ERK5 activation by okadaic acid was observed in HeLa cells exposed to epidermal growth factor and H(2)O(2) as well as in PC12 cells stimulated by nerve growth factor and H(2)O(2). Calyculin A, another PP1 and PP2A inhibitor, behaved similarly although these compounds are not structurally related. This suggests that either PP1 or PP2A or both are necessary for ERK5 activation. Protein kinase C (PKC) acts as a negative regulator of the ERK5 activation pathway, however our data suggest that the effects of PKC and the phosphatase are unrelated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Epidermal Growth Factor / metabolism*
  • Epidermal Growth Factor / pharmacology
  • HeLa Cells / drug effects
  • HeLa Cells / metabolism
  • Humans
  • Hydrogen Peroxide / pharmacology*
  • Marine Toxins
  • Mitogen-Activated Protein Kinase 7
  • Mitogen-Activated Protein Kinases / metabolism*
  • Nerve Growth Factor / metabolism*
  • Nerve Growth Factor / pharmacology
  • Okadaic Acid / pharmacology*
  • Oxazoles / pharmacology*
  • Oxidative Stress / physiology
  • PC12 Cells / drug effects
  • PC12 Cells / metabolism
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Protein Kinase C / metabolism
  • Rats


  • Enzyme Inhibitors
  • Marine Toxins
  • Oxazoles
  • Okadaic Acid
  • Epidermal Growth Factor
  • calyculin A
  • Nerve Growth Factor
  • Hydrogen Peroxide
  • Protein Kinase C
  • Mitogen-Activated Protein Kinase 7
  • Mitogen-Activated Protein Kinases
  • Phosphoprotein Phosphatases