Growth factor-dependent AKT activation and cell migration requires the function of c-K(B)-Ras versus other cellular ras isoforms.
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.
Liao
Jinhui
J
Department of Cell Biology, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland, Ohio 44195, USA.
Planchon
Sarah M
SM
Wolfman
Janice C
JC
Wolfman
Alan
A
D000818:Animals; D000077214:Becaplermin; D002147:Calmodulin / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D018631:ras Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
D002147:Calmodulin; D010982:Platelet-Derived Growth Factor; D020033:Protein Isoforms; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins