Fig. 4.

Effect of p38 inhibitors on LPS-stimulated phosphorylation of TTP in BMMϕ. BMMϕ labeled with [³²P]orthophosphoric acid were treated as described under “Experimental Procedures,” and cell extracts were immunoprecipitated with a specific anti-TTP antiserum; an autoradiograph of a 12% SDS-PAGE gel containing the immunoprecipitated phosphoprotein is shown. LPS stimulation (1 μg/ml for 30 min) stimulated the phosphorylation of a protein of apparent average M_r 43,000 in the WT cells (lanes 1–4), accompanied by an apparent increase in its average M_r as shown previously (19). Radioactive TTP was absent in the TTPKO cells (lanes 5– 8). The extent of phosphorylation was markedly inhibited by the use of the p38 inhibitors (5 μm), as indicated.