Platelet-derived-growth-factor stimulation of the p42/p44 mitogen-activated protein kinase pathway in airway smooth muscle: role of pertussis-toxin-sensitive G-proteins, c-Src tyrosine kinases and phosphoinositide 3-kinase

A M Conway, S Rakhit, S Pyne, N J Pyne

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115 Citations (Scopus)

Abstract

The mechanism used by the platelet-derived growth factor receptor (PDGFR) to activate the mitogen-activated- protein-kinase (p42/p44 MAPK) pathway was investigated in cultured airway smooth muscle (ASM) cells. We have found that pertussis toxin (PTX, which was used to inactivate the heterotrimeric G-protein Gi) induced an approx. 40-50% decrease in the activation of c-Src and p42/p44 MAPK by PDGF. An essential role for c-Src was confirmed using the c-Src inhibitor, PP1, which abolished p42/p44 MAPK activation (PP1 and PTX were without effect on PDGFR tyrosine phosphorylation). Furthermore, the PTX-dependent decrease in c-Src and p42/p44 MAPK activation appeared correlated. These findings suggest that the PDGFR can utilize the PTX-sensitive G-protein, Gi, to regulate c-Src and subsequent p42/p44 MAPK activation. Phosphoinositide 3-kinase (PI3K) has been shown by others to be involved in p42/p44 MAPK activation. This is confirmed here by experiments which showed that PI3K inhibitors (wortmannin and LY294002) reduced the activation of p42/p44 MAPK by PDGF. PI3K activity was increased in Grb-2 immunoprecipitates from PDGF-stimulated cells and was decreased by pretreating these cells with PTX. These findings show that Gi might also promote Grb-2-PI3K complex formation and that Grb-2 may be a site at which PI3K is integrated into the p42/p44 MAPK cascade. In conclusion, our results demonstrate that Gi enables the PDGFR to signal more efficiently to p42/p44 MAPK, and this appears to be achieved through the regulation of c-Src and Grb-2/PI3K, which are intermediates in the p42/p44 MAPK cascade.
Original languageEnglish
Pages (from-to)171-177
Number of pages7
JournalBiochemical journal
Volume337
Issue number2
DOIs
Publication statusPublished - 15 Jan 1999

Keywords

  • adenosine diphosphate ribose
  • animals
  • calcium-calmodulin-dependent protein kinases
  • cells, cultured
  • enzyme activation
  • GTP-binding protein alpha subunits, Gi-Go
  • guinea pigs
  • mitogen-activated protein kinase 1
  • mitogen-activated protein kinase 3
  • mitogen-activated protein kinases
  • models, biological
  • muscle, smooth
  • pertussis toxin
  • phosphatidylinositol 3-kinases
  • phosphorylation
  • platelet-derived growth factor
  • receptors, platelet-derived growth factor
  • respiratory system
  • signal transduction
  • virulence factors, bordetella
  • src-family kinases

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