Growth Factor-dependent AKT Activation and Cell Migration Requires the Function of c-K(B)-Ras Versus Other Cellular Ras Isoforms

• Published in: The Journal of biological chemistry 2006-10, Vol.281 (40), p.29730-29738
• Main Authors: Liao, Jinhui, Planchon, Sarah M., Wolfman, Janice C., Wolfman, Alan
• Format: Article
• Language: English
• Subjects: 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
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M600668200

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.