TY - JOUR
T1 - Role of protein kinase C isoforms in phorbol ester-induced vascular endothelial growth factor expression in human glioblastoma cells
AU - Shih, Shu Ching
AU - Mullen, Andrew
AU - Abrams, Kristin
AU - Mukhopadhyay, Debabrata
AU - Claffey, Kevin P.
PY - 1999/5/28
Y1 - 1999/5/28
N2 - Aberrant expression of the potent angiogenic cytokine, vascular endothelial growth factor (VEGF), has been demonstrated to be associated with most human solid tumors. Both transcriptional and post-transcriptional mechanisms have been shown to modulate VEGF expression in a multitude of cell types. Here we report that when protein kinase C (PKC) pathways were activated in human glioblastoma U373 cells by phorbol 12-myristate 13- acetate (PMA), VEGF mRNA expression was up-regulated via a post- transcriptional mRNA stabilization mechanism. PMA treatment exhibited no increase in VEGF-specific transcriptional activation as determined by run- off transcription assays and VEGF promoter-luciferase reporter assays. However, PMA increased VEGF mRNA half-life from 0.8 to 3.6 h which was blocked by PKC inhibitors but not by protein kinase A or cyclic nucleotide- dependent protein kinase inhibitors. When U373 cells were transfected with antisense oligonucleotide sequences to the translation start sites of PKC- α, -β, -γ, -δ, -ε, or -ζ isoforms, both PKC-α and -ζ antisense oligonucleotides showed substantial inhibition of PMA-induced VEGF mRNA. In addition, overexpression of PKC-ζ resulted in a strong constitutive upregulation of VEGF mRNA expression. This study demonstrates for the first time that specific PKC isoforms regulate VEGF mRNA expression through posttranscriptional mechanisms.
AB - Aberrant expression of the potent angiogenic cytokine, vascular endothelial growth factor (VEGF), has been demonstrated to be associated with most human solid tumors. Both transcriptional and post-transcriptional mechanisms have been shown to modulate VEGF expression in a multitude of cell types. Here we report that when protein kinase C (PKC) pathways were activated in human glioblastoma U373 cells by phorbol 12-myristate 13- acetate (PMA), VEGF mRNA expression was up-regulated via a post- transcriptional mRNA stabilization mechanism. PMA treatment exhibited no increase in VEGF-specific transcriptional activation as determined by run- off transcription assays and VEGF promoter-luciferase reporter assays. However, PMA increased VEGF mRNA half-life from 0.8 to 3.6 h which was blocked by PKC inhibitors but not by protein kinase A or cyclic nucleotide- dependent protein kinase inhibitors. When U373 cells were transfected with antisense oligonucleotide sequences to the translation start sites of PKC- α, -β, -γ, -δ, -ε, or -ζ isoforms, both PKC-α and -ζ antisense oligonucleotides showed substantial inhibition of PMA-induced VEGF mRNA. In addition, overexpression of PKC-ζ resulted in a strong constitutive upregulation of VEGF mRNA expression. This study demonstrates for the first time that specific PKC isoforms regulate VEGF mRNA expression through posttranscriptional mechanisms.
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U2 - 10.1074/jbc.274.22.15407
DO - 10.1074/jbc.274.22.15407
M3 - Article
C2 - 10336429
AN - SCOPUS:0033056944
SN - 0021-9258
VL - 274
SP - 15407
EP - 15414
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 22
ER -