PDGF‐induced Akt phosphorylation does not activate NF‐κB in human vascular smooth muscle cells and fibroblasts

Abstract
A recent report suggested that platelet‐derived growth factor (PDGF) activates nuclear factor‐κB (NF‐κB) by phosphorylation of the protein kinase Akt [Romashkova and Makarov, Nature 401 (1999) 86–90]. The present study investigates the role of Akt in the activation of NF‐κB by tumor necrosis factor‐α (TNFα, 10 ng/ml) and PDGF‐BB (20 ng/ml) in human vascular smooth muscle cells (SMC), skin and foreskin fibroblasts. TNFα stimulated serine phosphorylation and degradation of the inhibitory protein IκBα and strongly induced nuclear NF‐κB translocation and binding activity. PDGF did not induce serine phosphorylation or degradation of IκBα and did not enhance binding activity of NF‐κB. In contrast, stimulation with PDGF resulted in a marked phosphorylation of Akt, but no Akt phosphorylation occurred after stimulation with TNFα. These data suggest that Akt phosphorylation is not involved in NF‐κB activation in human SMC and fibroblasts.