Increase in constitutively active MEK1 species by introduction of MEK1 mutations identified in cancers

Biochim Biophys Acta Proteins Proteom. 2019 Jan;1867(1):62-70. doi: 10.1016/j.bbapap.2018.05.004. Epub 2018 May 9.


The kinase MEK1 is an essential component of the mitogen-activated protein kinase cascades. Somatic mutations that have been identified in the MEK1-coding gene generally enhance kinase activity. Consequently, MEK1 has attracted much interest as a target for cancer therapy to block the aberrant activity. By using Phos-tag affinity electrophoresis, we found that the introduction of mutations detected in certain sporadic cancers or in MEK-inhibitor-resistant cancer cells produced constitutively active MEK1 species containing phosphorylated Ser-218 and Ser-222 residues; it also enhanced the constitutive activity of the kinase. Phosphorylation profiling of the mutants in the presence of inhibitors of RAF/MEK demonstrated that several mutations conferred resistance to multiple inhibitors as a result of an increase in the quantity of active MEK1 species containing the two phosphorylated Ser-218 and Ser-222 residues. Phos-tag-based phosphorylation profiling of MEK1 can therefore provide clinical insights into characteristics of individual mutations in the MEK1-coding gene.

Keywords: MEK1; Phos-tag SDS-PAGE; Phosphoproteomics; Phosphorylation; Somatic mutation; Sporadic cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Electrophoresis, Gel, Two-Dimensional / methods
  • Electrophoresis, Polyacrylamide Gel
  • HEK293 Cells
  • Humans
  • MAP Kinase Kinase 1 / genetics*
  • MAP Kinase Kinase 1 / metabolism
  • MAP Kinase Signaling System
  • Mutagenesis, Site-Directed
  • Mutation
  • Neoplasms / enzymology
  • Neoplasms / genetics*
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology


  • Phosphoproteins
  • Protein Kinase Inhibitors
  • MAP Kinase Kinase 1