Src phosphorylates Tyr284 in TGF-beta type II receptor and regulates TGF-beta stimulation of p38 MAPK during breast cancer cell proliferation and invasion

Cancer Res. 2007 Apr 15;67(8):3752-8. doi: 10.1158/0008-5472.CAN-06-3851.

Abstract

Genetic and epigenetic events often negate the cytostatic function of transforming growth factor-beta (TGF-beta) in mammary epithelial cells (MEC), which ultimately enables malignant MECs to proliferate, invade, and metastasize when stimulated by TGF-beta. The molecular mechanisms underlying this phenotypic conversion of TGF-beta function during mammary tumorigenesis remain poorly defined. We previously established alpha(v)beta(3) integrin and Src as essential mediators of mitogen-activated protein kinase (MAPK) activation, invasion, and epithelial-to-mesenchymal transition stimulated by TGF-beta in normal and malignant MECs. Mechanistically, beta(3) integrin interacted physically with the TGF-beta type II receptor (TbetaR-II), leading to its tyrosine phosphorylation by Src and the initiation of oncogenic signaling by TGF-beta. We now show herein that Src phosphorylated TbetaR-II on Y284 both in vitro and in vivo. Interestingly, although the expression of Y284F-TbetaR-II mutants in breast cancer cells had no effect on TGF-beta stimulation of Smad2/3, this TbetaR-II mutant completely abrogated p38 MAPK activation by TGF-beta. Accordingly, Src-mediated phosphorylation of Y284 coordinated the docking of the SH2 domains of growth factor receptor binding protein 2 (Grb2) and Src homology domain 2 containing (Shc) TbetaR-II, thereby associating these adapter proteins to MAPK activation by TGF-beta. Importantly, Y284F-TbetaR-II mutants also abrogated breast cancer cell invasion induced by alpha(v)beta(3) integrin and TGF-beta as well as partially restored their cytostatic response to TGF-beta. Our findings have identified a novel alpha(v)beta(3) integrin/Src/Y284/TbetaR-II signaling axis that promotes oncogenic signaling by TGF-beta in malignant MECs and suggest that antagonizing this signaling axis may one day prove beneficial in treating patients with metastatic breast cancers.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Cell Growth Processes / physiology
  • Enzyme Activation
  • GRB2 Adaptor Protein / metabolism
  • Humans
  • Integrin alphaVbeta3 / metabolism
  • MAP Kinase Signaling System
  • Mammary Neoplasms, Experimental / enzymology
  • Mammary Neoplasms, Experimental / metabolism*
  • Mammary Neoplasms, Experimental / pathology
  • Mice
  • Neoplasm Invasiveness
  • Phosphorylation
  • Protein Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / metabolism*
  • Shc Signaling Adaptor Proteins
  • Smad2 Protein / metabolism
  • Smad3 Protein / metabolism
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Transforming Growth Factor beta / metabolism*
  • p38 Mitogen-Activated Protein Kinases / metabolism*
  • src Homology Domains
  • src-Family Kinases / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • GRB2 Adaptor Protein
  • Integrin alphaVbeta3
  • Receptors, Transforming Growth Factor beta
  • SHC1 protein, human
  • Shc Signaling Adaptor Proteins
  • Shc1 protein, mouse
  • Smad2 Protein
  • Smad3 Protein
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Transforming Growth Factor beta
  • src-Family Kinases
  • Protein Serine-Threonine Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Receptor, Transforming Growth Factor-beta Type II