ACTIVATION OF PROTEIN-KINASES AND THE INACTIVATION OF PROTEIN PHOSPHATASE 2A IN TUMOR-NECROSIS-FACTOR AND INTERLEUKIN-1 SIGNAL-TRANSDUCTIONPATHWAYS

We report the identification of 16 of the 30 cellular proteins which a re rapidly phosphorylated in tumour-necrosis-factor-(TNF)-treated or i nterleukin-1-(IL-1)-treated primary human fibroblasts. Phosphorylation assays of proteins found in the cytosolic extract of human fibroblast s by in vitro assays indicate that at least 12 of these proteins are l ikely to be substrates for mitogen-activated protein kinase(s) (MAP ki nase), mitogen-activated protein-kinase-activated protein kinase 2 (MA PKAP kinase 2), a pp60(c-src)-like tyrosine kinase as well as for a pu tative dual nucleotide protein kinase (DNK) in TNF-treated or IL-1-tre ated cells. Comparison of the phosphorylation of cytosolic proteins in vitro by exogenously added protein kinases with that observed in cell s treated with TNF or IL-1 enabled the identification of cellular subs trates of TNF-activated and IL-1-activated cellular protein kinases. C omparison of protein kinase activities of cytosolic extracts derived f rom TNF-treated or IL-1-treated and control fibroblasts also show the activation of MAP kinase, MAPKAP kinase 2, a putative DNK and a pp60(s rc)-like tyrosine kinase 3-19 fold. The data suggest TNF or IL-1 signa l transduction may involve the phosphorylation of protein phosphatase type 2A by a pp60(src)-like tyrosine kinase, followed by the activatio n of MAP kinase, MAPKAP kinase 2 and the putative DNK. However, the ac tivation of MAP kinase and MAPKAP kinase 2 may be independent of the e arlier activation of pp60(src)-like tyrosine kinase and the inactivati on of protein phosphatase type 2A.