S. Pal et al., Role of protein kinase C zeta in Ras-mediated transcriptional activation of vascular permeability factor/vascular endothelial growth factor expression, J BIOL CHEM, 276(4), 2001, pp. 2395-2403
Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF),
a multifunctional cytokine, is regulated by different factors including de
gree of cell differentiation, hypoxia, and certain oncogenes namely, ras an
d src, The up-regulation of VPF/VEGF expression by Ras has been found to be
through both transcription and mRNA stability. The present study investiga
tes a novel pathway whereby Ras promotes the transcription of VPF/VEGF by a
ctivating protein kinase C zeta (PKC zeta), The Res-mediated overexpression
of VPF/VEGF was also found to be inhibited by using the antisense or the d
ominant-negative mutant of PKC zeta In co-transfection assays, by overexpre
ssing oncogenic Ha-Ras (12 V) and PKC zeta, there was an additive effect up
to 4-fold in activation of Spl-mediated VPF/VEGF transcription. It has bee
n shown through electrophoretic mobility shift assay that Ras promoted the
PKC zeta -induced binding of Spl to the VPF/VEGF promoter. In the presence
of PDK-1, a major activating kinase for PKC, the Ras-mediated activation of
VPF/VEGF promoter through PKC zeta was further increased, suggesting that
PKC zeta can serve as an effector for both Ras and PDK-1, In other experime
nts, with the use of a dominant-negative mutant of phosphatidylinositol 3-k
inase, the activation of VPF/VEGF promoter through Ras, PDK-1, and PKC zeta
was completely repressed, indicating phosphatidylinositol 3-kinase as an i
mportant component of this pathway. Taken together, these data elucidate th
e signaling mechanism of Res-mediated VPF/VEGF transcriptional activation t
hrough PKC zeta and also provide insight into PKC zeta and Spl-dependent tr
anscriptional regulation of VPF/VEGF.