title: Involvement of a putative protein-tyrosine phosphatase and I kappa B-alpha serine phosphorylation in nuclear factor kappa B activation by tumor necrosis factor.
abstract: Inhibitors of phosphotyrosyl protein phosphatases, pervanadate and phenylarsine oxide, abrogate tumor necrosis factor (TNF)-induced nuclear factor kappa B (NF-kappa B) nuclear translocation in transformed cell lines (U-937 and Jurkat) and primary fibroblasts (MRC-5 and REF). The inhibitors also abrogate NF-kappa B activation by the phosphoseryl/threonyl protein phosphatase inhibitor okadaic acid in U-937 cells. Inhibition of NF-kappa B activation is not due to a general inhibitory effect since neither pervanadate nor phenylarsine oxide treatment affected the constitutive DNA-binding activity of the transcription factors octamer-1 and cAMP response element-binding protein in U-937 cells, nor did these compounds inhibit the TNF-induced phosphorylation of proteins, viz. hsp-27, eukaryotic initiation factor 4e, and pp19, in MRC-5 fibroblasts. Overexpression of the protein-tyrosine phosphatase HPTP alpha resulted in a constitutive nuclear NF-kappa B-like DNA-binding activity in REF cells. Conversely, treatment of human protein-tyrosine phosphatase alpha-overexpressing cells with phenylarsine oxide led to a loss of the constitutive NF-kappa B activity. The presence of a tyrosine phosphorylation site on the inhibitor of NF-kappa B (I kappa B-alpha) suggested that it could be a target for TNF/okadaic acid-induced tyrosine dephosphorylation. However, no tyrosine phosphorylation was detected on I kappa B-alpha fron unstimulated cells, while TNF/okadaic acid-treated cells showed increased phosphorylation of I kappa B-alpha exclusively at serine residue(s). Treatment of cells with pervanadate inhibited TNF-induced I kappa B-alpha phosphorylation and degradation, whereas the serine protease inhibitors tosylphenylalanyl chloromethyl ketone and N alpha-p-tosyl-L-lysine chloromethyl ketone prevented TNF-induced I kappa B-alpha degradation and NF-kappa B nuclear translocation, but not the TNF-induced phosphorylation of I kappa B-alpha. The data suggest that TNF and okadaic acid induce the activation of a putative protein-tyrosine phosphatase(s), leading to I kappa B-alpha serine phosphorylation and degradation and NF-kappa B nuclear translocation.
authors.affiliation: Institute of Molecular and Cell Biology, National University of Singapore.
authors.forename: S D
authors.initials: SD
authors.lastname: Menon
authors.forename: G R
authors.initials: GR
authors.lastname: Guy
authors.forename: Y H
authors.initials: YH
authors.lastname: Tan
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002461:Cell Line, Transformed; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004988:Ethers, Cyclic / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D019319:Okadaic Acid; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D012694:Serine / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D004988:Ethers, Cyclic; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D015842:Serine Proteinase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D019319:Okadaic Acid; D012694:Serine; D004247:DNA; D017027:Protein Tyrosine Phosphatases