Roles of phosphatidylinositol 3-kinase and Rac in the nuclear signaling by tumor necrosis factor-alpha in rat-2 fibroblasts.
We investigated the extent to which phosphatidylinositol 3-kinase (PI 3-kinase) and Rac, a member of the Rho family of small GTPases, are involved in the signaling cascade triggered by tumor necrosis factor (TNF)-alpha leading to activation of c-fos serum response element (SRE) and c-Jun amino-terminal kinase (JNK) in Rat-2 fibroblasts. Inhibition of PI 3-kinase by LY294002 or wortmannin, two specific PI 3-kinase antagonists, or co-transfection with a dominant negative mutant of PI 3-kinase dose-dependently blocked stimulation of c-fos SRE by TNF-alpha. Similarly, LY294002 significantly diminished TNF-alpha-induced activation of JNK, suggesting that nuclear signaling triggered by TNF-alpha is dependent on PI 3-kinase-mediated activation of both c-fos SRE and JNK. We also found nuclear signaling by TNF-alpha to be Rac-dependent, as demonstrated by the inhibitory effect of transient co-transfection with a dominant negative Rac mutant, RacN17. Our findings suggest that Rac is situated downstream of PI 3-kinase in the TNF-alpha signaling pathway to the nucleus, and we conclude that PI 3-kinase and Rac each plays a pivotal role in the nuclear signaling cascade triggered by TNF-alpha.
Kim
B C
BC
Department of Life Science, Kwang-Ju Institute of Science and Technology, Kwang-Ju 500-712, Korea.
Lee
M N
MN
Kim
J Y
JY
Lee
S S
SS
Chang
J D
JD
Kim
S S
SS
Lee
S Y
SY
Kim
J H
JH
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002518:Ceramides / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D016762:Genes, fos; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010741:Phospholipases A / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D020218:Response Elements; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D020744:rac GTP-Binding Proteins
D002518:Ceramides; D002867:Chromones; D009025:Morpholines; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D010741:Phospholipases A; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins