Pkc Alpha Phosphorylates Cytosolic Nf-Kappab/P65 and Pkc Delta Delays Nuclear Trans Location of Nf-Kappab/P65 in U1242 Glioblastoma Cells

Abstract

AIM: Protein kinase-C (PKC) and NF-kappaB are involved in cell survival, proliferation, migration and radioresistance in glioblastoma multiforme (GBM). We sought to determine the interaction between PKC and NF-kappaB pathways. MATERIAL and METHODS: The activation of NF-kappaB by PKC a and PKC delta was assessed by Western blotting after the stimulation with Phorbol 12-Myristate 13-Acetate (PMA). Gene silencing of PKC alpha, PKC delta and NF-kappaB/p65 with siRNA interference was utilized to evaluate their roles in NF-kB activation and cell proliferation. RESULTS: PMA induced the phosphorylation of NF-kappaB/p65 by PKC alpha. Gene silencing with siRNA against NF-kappaB/p65 inhibited [3H]-thymidine incorporation in U1242 GBM cells. PKC delta decelerated the nuclear translocation of activated NF-kappaB/p65 up to 4 hours after the stimulation. PMA induced death was not observed in PKC delta silenced cells where activated NF-kappaB/p65 was located immediately in the nucleus. CONCLUSION: NF-kappaB/p65 is pro-survival and proliferative factor in U1242 GBM cells. PKC alpha is needed to phosphorylate NF-kappaB/p65. PKC delta delays the translocation of active NF-kappaB/p65 into the nucleus. PMA-induced cell death occurred if the phospho-NF-kappaB/p65 was prohibited from entering the nucleus in PKC delta positive cells. Translocation of phosphorylated form of NF-kappaB into the nucleus is critical in GBM cell proliferation.