Figure 1.

Mkp-1 deficiency results in prolonged p38 and JNK activation. (A) The kinetics of MAP kinase activation in Mkp-1 ^+/+ and Mkp-1 ^−/− macrophages after LPS stimulation. Elicited peritoneal macrophages from both Mkp-1 ^+/+ and Mkp-1 ^−/− mice were stimulated with 100 ng/ml LPS for the indicated times, and cell lysates were analyzed for phospho-p38, phospho-JNK, phospho-ERK, phospho-MK2, and MKP-1 using Western blotting. (B) Detailed kinetics of p38, JNK, and ERK inactivation after LPS challenge. Mkp-1 ^+/+ and Mkp-1 ^−/− samples were processed together, with the exception of the initial electrophoresis in which Mkp-1 ^+/+ and Mkp-1 ^−/− samples were run on different gels. (C) Comparison of MK2 activities between Mkp-1 ^+/+ and Mkp-1 ^−/− macrophages using immune complex kinase assays. Peritoneal macrophages were treated with 100 ng/ml LPS for the indicated times, and MK-2 kinase activity was examined by immune complex kinase assays using [γ-³²P]ATP and a mouse Hsp25 as substrate. Kinase activities were quantitated using a phosphorImager and expressed as fold-activation relative to controls.