Phosphatidylinositol 3-kinase as a mediator of TNF-induced NF-kappa B activation.
The activation of transcription factor NF-kappa B by TNF involves the stimulation of a novel signaling cascade. In this paper we show that phosphatidylinositol 3-kinase (PI 3-kinase) may play a pivotal role in TNF-mediated activation of NF-kappa B-dependent genes. Consistent with its involvement in TNF signaling, PI 3-kinase activities in HepG2 and U937 cells can be stimulated by TNF in a rapid but transient manner through a mechanism that may involve its association with the insulin receptor substrate-1. A dominant-negative mutant of the p85 regulatory subunit of PI 3-kinase, which is a potent inhibitor of PI 3-kinase signaling, effectively blocked the TNF-induced expression of an NF-kappa B-dependent reporter gene. Although PI 3-kinase may be required for NF-kappa B activation, overexpression of its p110 catalytic subunit alone was unable to induce an NF-kappa B/chloramphenicol acetyltransferase (CAT) reporter gene. However, when TNF was added to p110-overexpressing cells, there was a synergistic activation of the NF-kappa B/CAT reporter, suggesting that other TNF-inducible signals may cooperate with PI 3-kinase to activate NF-kappa B. Consistent with its role in NF-kappa B activation, inhibition of PI 3-kinase activity by wortmannin or LY294002 greatly potentiated TNF-induced apoptosis. This TNF/wortmannin-induced apoptosis was markedly prevented in cells overexpressing Rel A. Taken together, our results indicate that a PI 3-kinase-regulated step in TNF-signaling is critical for the expression of NF-kappa B-dependent genes.
Reddy
S A
SA
Department of Biochemistry, University of Texas, M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Huang
J H
JH
Liao
W S
WS
D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D020134:Catalytic Domain / Q000502:physiology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D002867:Chromones / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000235:genetics; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051058:Oncogene Protein v-akt; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D020298:U937 Cells; D000077191:Wortmannin
D000730:Androstadienes; D015500:Chloramphenicol O-Acetyltransferase; D002867:Chromones; D004268:DNA-Binding Proteins; D009025:Morpholines; D016328:NF-kappa B; D051058:Oncogene Protein v-akt; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D015682:Retroviridae Proteins, Oncogenic; D014409:Tumor Necrosis Factor-alpha; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one