Growth factor-dependent AKT activation and cell migration requires the function of c-K(B)-Ras versus other cellular ras isoforms

J Biol Chem. 2006 Oct 6;281(40):29730-8. doi: 10.1074/jbc.M600668200. Epub 2006 Aug 14.

Abstract

K-Ras-negative fibroblasts are defective in their steady-state expression of MMP-2. This occurs through c-K(B)-Ras dependent regulation of basal levels of AKT activity. In this report, we have extended those studies to demonstrate that in the absence of K-Ras expression, PDGF-BB fails to induce significant AKT activation, although this was not the case in N-Ras-negative cells. This phenotype was directly linked to PDGF-dependent cell migration. All of the independently immortalized K-Ras-negative cells failed to migrate upon the addition of PDGF. Only ectopic expression of c-K(B)-Ras, not c-K(A)-Ras nor oncogenic N-Ras, could restore both PDGF-dependent AKT activation and cell migration. Since most Ras binding partners can interact with all Ras isoforms, the specificity of PDGF-dependent activation of AKT and enhanced cell migration suggests that these outcomes are likely to be regulated through a c-K(B)-Ras-specific binding partner. Others have published that of the four Ras isoforms, only K(B)-Ras can form a stable complex with calmodulin (CaM). Along those lines, we provide evidence that 1) PDGF addition results in increased levels of a complex between c-K(B)-Ras and CaM and 2) the biological outcomes that are strictly dependent on c-K(B)-Ras (AKT activation and cell migration) are blocked by CaM antagonists. The PDGF-dependent activation of ERK is unaffected by the absence of K(B)-Ras and presence of CaM antagonists. This is the first example of a linkage between a specific biological outcome, cell migration, and the activity of a single Ras isoform, c-K(B)-Ras.

Publication types

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

MeSH terms

  • Animals
  • Becaplermin
  • Calmodulin / physiology
  • Cell Line
  • Cell Movement / physiology*
  • Enzyme Activation / physiology
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Mice
  • Platelet-Derived Growth Factor / physiology*
  • Protein Isoforms / deficiency
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Proto-Oncogene Proteins c-sis
  • ras Proteins / deficiency
  • ras Proteins / genetics
  • ras Proteins / physiology*

Substances

  • Calmodulin
  • Platelet-Derived Growth Factor
  • Protein Isoforms
  • Proto-Oncogene Proteins c-sis
  • Becaplermin
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases
  • ras Proteins