Activation of mitogen-activated protein kinase by arachidonic acid in rat liver epithelial WB cells by a protein kinase C-dependent mechanism

J Biol Chem. 1995 Mar 3;270(9):4201-4. doi: 10.1074/jbc.270.9.4201.


Arachidonic acid (20:4(n-6)), which is released by cells responding to a wide range of stimuli, may play an important role in intracellular signaling. We now report that incubation of WB cells with 20:4(n-6) resulted in the appearance of several tyrosine-phosphorylated cytosolic proteins. Two of the phosphotyrosine-containing proteins, migrating in SDS-polyacrylamide gels of approximately 43 and 45 kDa, corresponded in mobility to phosphorylated species of the 42- and 44-kDa mitogen-activated protein kinase (MAPK) isoforms. Immunoblots of soluble fractions from unstimulated WB cells with anti-MAPK antibodies revealed the presence of the 42- and 44-kDa isoforms of MAPK. Upon incubation with 20:4(n-6), the mobility of both isoforms was retarded, consistent with their activation by phosphorylation. Chromatography of soluble fractions from these cells on Mono Q columns revealed early and late eluting peaks of myelin basic protein kinase activity, which contained the 42- and 44-kDa MAPK isoforms, respectively. Activation of MAPK was transient, peaking at 5 min, and was detectable at 5 microM 20:4(n-6). Further studies into the mechanisms by which MAPK was activated by 20:4(n-6) strongly suggested the involvement of protein kinase C (PKC). Not only did incubation of WB cells with 20:4(n-6) result in the translocation of PKC alpha, delta, and epsilon to a particulate fraction, it was found that the fatty acid failed to activate MAPK in cells pretreated for 26 h with phorbol 12-myristate 13-acetate, which depleted WB cells of PKC alpha, delta and epsilon. In addition, fatty acids of the n-3 series were effective activators of MAPK. The present study, to our knowledge, is the first to report that polyunsaturated fatty acids can cause the activation of MAPK.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arachidonic Acid / pharmacology*
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cells, Cultured
  • Enzyme Activation
  • Epithelial Cells
  • Epithelium / drug effects
  • Epithelium / enzymology
  • Fatty Acids, Unsaturated / pharmacology
  • Liver / cytology
  • Liver / drug effects*
  • Liver / enzymology
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases*
  • Protein Kinase C / metabolism*
  • Protein-Tyrosine Kinases / metabolism*
  • Rats
  • Tetradecanoylphorbol Acetate / pharmacology


  • Fatty Acids, Unsaturated
  • Arachidonic Acid
  • Protein-Tyrosine Kinases
  • Protein Kinase C
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • Tetradecanoylphorbol Acetate