Dok-3 sequesters Grb2 and inhibits the Ras-Erk pathway downstream of protein-tyrosine kinases

Genes Cells. 2006 Feb;11(2):143-51. doi: 10.1111/j.1365-2443.2006.00926.x.


Adaptor proteins are essential in coordinating recruitment and, in a few cases, restraint of various effectors during cellular signaling. Dok-1, Dok-2 and Dok-3 comprise a closely related family of adaptor, which negatively regulates mitogen-activated protein kinase Erk downstream of protein-tyrosine kinases (PTKs). Recruitment of p120 rasGAP, a potent inhibitor of Ras, by Dok-1 and Dok-2 appears critical in the negative regulation of the Ras-Erk pathway. However, as Dok-3 does not bind rasGAP, it has been unclear how Dok-3 inhibits Erk downstream of PTKs. Here, we identified Grb2 as a Dok-3-binding protein upon its tyrosine phosphorylation. This interaction required the intact binding motifs of the Grb2 SH2 domain, and a mutant (Dok-3-FF) having a Tyr/Phe substitution at these motifs failed to inhibit Ras and Erk activation downstream of a cytoplasmic PTK Src. Because Grb2 forms a stable complex with Sos, a crucial activator of Ras, these data suggest that Dok-3 restrains Grb2 and inhibits the ability of the Grb2-Sos complex to activate Ras. Indeed, forced expression of Dok-3, but not Dok-3-FF, inhibited the recruitment of the Grb2-Sos complex to Shc downstream of Src, which is an essential event for activation of the Ras-Erk pathway. These findings indicate that Dok-3 sequesters Grb2 from Shc and inhibits the Ras-Erk pathway downstream of PTKs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cells, Cultured
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors*
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • GRB2 Adaptor Protein / chemistry
  • GRB2 Adaptor Protein / metabolism*
  • Humans
  • Mice
  • Molecular Sequence Data
  • Oncogene Protein pp60(v-src) / metabolism
  • Protein Binding
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins p21(ras) / antagonists & inhibitors*
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • Shc Signaling Adaptor Proteins
  • Signal Transduction*
  • Son of Sevenless Proteins / metabolism
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Tyrosine / metabolism


  • Adaptor Proteins, Signal Transducing
  • DOK3 protein, human
  • GRB2 Adaptor Protein
  • SHC1 protein, human
  • Shc Signaling Adaptor Proteins
  • Shc1 protein, mouse
  • Son of Sevenless Proteins
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Tyrosine
  • Protein-Tyrosine Kinases
  • Oncogene Protein pp60(v-src)
  • Extracellular Signal-Regulated MAP Kinases
  • Proto-Oncogene Proteins p21(ras)