Cell type-specific expression of the IkappaB kinases determines the significance of phosphatidylinositol 3-kinase/Akt signaling to NF-kappa B activation.
Phosphatidylinositol (PI) 3-kinase/Akt signaling activates NF-kappa B through pleiotropic, cell type-specific mechanisms. This study investigated the significance of PI 3-kinase/Akt signaling to tumor necrosis factor (TNF)-induced NF-kappa B activation in transformed, immortalized, and primary cells. Pharmacological inhibition of PI 3-kinase blocked TNF-induced NF-kappa B DNA binding in the 293 line of embryonic kidney cells, partially affected binding in MCF-7 breast cancer cells, HeLa and ME-180 cervical carcinoma cells, and NIH 3T3 cells but was without significant effect in H1299 and human umbilical vein endothelial cells, cell types in which TNF activated Akt. NF-kappa B is retained in the cytoplasm by inhibitory proteins, I kappa Bs, which are phosphorylated and targeted for degradation by I kappa B kinases (IKK alpha and IKK beta). Expression and the ratios of IKK alpha and IKK beta, which homo- and heterodimerize, varied among cell types. Cells with a high proportion of IKK alpha (the IKK kinase activated by Akt) to IKK beta were most sensitive to PI 3-kinase inhibitors. Consequently, transient expression of IKK beta diminished the capacity of the inhibitors to block NF-kappa B DNA binding in 293 cells. Also, inhibitors of PI 3-kinase blocked NF-kappa B DNA binding in Ikk beta-/- but not Ikk alpha-/- or wild-type cells in which the ratio of IKK alpha to IKK beta is low. Thus, noncoordinate expression of I kappa B kinases plays a role in determining the cell type-specific role of Akt in NF-kappa B activation.
Department of Microbiology and Immunology and Walther Oncology Center, Indiana University School of Medicine, 950 West Walnut Street, Indianapolis, IN 46202, USA.
Jason A
JA
Gustin
Osman N
ON
Ozes
Hakan
H
Akca
Roxana
R
Pincheira
Lindsey D
LD
Mayo
Qiutang
Q
Li
Javier Rivera
JR
Guzman
Chandrashekhar K
CK
Korgaonkar
David B
DB
Donner
D000818:Animals; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D004247:DNA; D051550:I-kappa B Kinase; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D014409:Tumor Necrosis Factor-alpha; C494918:AKT1 protein, human; C496559:CHUK protein, human; C496564:Chuk protein, mouse; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse