Signal transduction for nuclear factor-kappa B activation. Proposed location of antioxidant-inhibitable step.
Reactive oxygen species are thought to be messengers for nuclear factor (NF)-kappa B activation because its activation can be abrogated by antioxidants. However, this study identifies, for the first time, NF-kappa B activators that are insensitive to antioxidants. NF-kappa B activation that is induced by either calyculin A or okadaic acid (inhibitors of serine/threonine protein phosphatases 1 and 2A) is not blocked by N-acetylcysteine or dihydrolipoate in Jurkat and U937 cells. Nonetheless, these antioxidants block induction by TNF-alpha, lymphotoxin, and PMA. Unlike okadaic acid and calyculin A, neither TNF-alpha, lymphotoxin, nor PMA inhibited activities of phosphatases 1 and 2A. NF-kappa B activation induced by okadaic acid or calyculin A was not blocked by a myosin light chain kinase inhibitor, but was prevented by a protease inhibitor. The mitochondrial inhibitor, rotenone, also inhibited NF-kappa B activation by calyculin A; however, this inhibition was accompanied by a depletion of cellular ATP. These results suggest that 1) phosphatase inhibitors either target a component of signal transduction, which occurs downstream to an antioxidant-sensitive step or use distinct signaling pathways; 2) inhibition of phosphatases 1 and 2A is not a step in the pathway of TNF-alpha-, lymphotoxin-, or PMA-induced NF-kappa B activation; 3) myosin light chain kinase does not participate in NF-kappa B activation; and 4) activation of NF-kappa B by phosphatase inhibitors is controlled by proteases.
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Y J
YJ
Suzuki
M
M
Mizuno
L
L
Packer
D000975:Antioxidants / Q000494:pharmacology*; D001483:Base Sequence; D002460:Cell Line; D004988:Ethers, Cyclic / Q000494:pharmacology; D006801:Humans; D008387:Marine Toxins; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000975:Antioxidants; D004988:Ethers, Cyclic; D008387:Marine Toxins; D016328:NF-kappa B; D010080:Oxazoles; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D019319:Okadaic Acid; C059041:calyculin A; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases