Chk1 phosphorylates the tumour suppressor Mig-6, regulating the activation of EGF signalling

EMBO J. 2012 May 16;31(10):2365-77. doi: 10.1038/emboj.2012.88. Epub 2012 Apr 13.

Abstract

The tumour suppressor gene product Mig-6 acts as an inhibitor of epidermal growth factor (EGF) signalling. However, its posttranslational modifications and regulatory mechanisms have not been elucidated. Here, we investigated the phosphorylation of human Mig-6 and found that Chk1 phosphorylated Mig-6 in vivo as well as in vitro. Moreover, EGF stimulation promoted phosphorylation of Mig-6 without DNA damage and the phosphorylation was inhibited by depletion of Chk1. EGF also increased Ser280-phosphorylated Chk1, a cytoplasmic-tethering form, via PI3K pathway. Mass spectrometric analyses suggested that Ser 251 of Mig-6 was a major phosphorylation site by Chk1 in vitro and in vivo. Substitution of Ser 251 to alanine increased inhibitory activity of Mig-6 against EGF receptor (EGFR) activation. Moreover, EGF-dependent activation of EGFR and cell growth were inhibited by Chk1 depletion, and were rescued by co-depletion of Mig-6. Our results suggest that Chk1 phosphorylates Mig-6 on Ser 251, resulting in the inhibition of Mig-6, and that Chk1 acts as a positive regulator of EGF signalling. This is a novel function of Chk1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / chemistry
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Substitution
  • Checkpoint Kinase 1
  • Epidermal Growth Factor / metabolism*
  • Gene Expression Regulation
  • Humans
  • Mass Spectrometry
  • Mutagenesis, Site-Directed
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Serine / genetics
  • Serine / metabolism
  • Signal Transduction*
  • Tumor Suppressor Proteins / chemistry
  • Tumor Suppressor Proteins / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • MIG-6 protein, human
  • Tumor Suppressor Proteins
  • Serine
  • Epidermal Growth Factor
  • Protein Kinases
  • CHEK1 protein, human
  • Checkpoint Kinase 1