Catalytic activation of mitogen-activated protein (MAP) kinase phosphatase-1 by binding to p38 MAP kinase: critical role of the p38 C-terminal domainin its negative regulation

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is the archety pal member of the dual-specificity protein phosphatase family, the expressi on of which can be rapidly induced by a variety of growth factors and cellu lar stress. Since MKP-1 protein localizes in the nucleus, it has been sugge sted to pray an important role in the feedback control of MAP kinase-regula ted gene transcription. Recently it has been demonstrated that the interact ion of several cytosolic MAP kinase phosphatases with MAP kinases can trigg er the catalytic activation of the phosphatases. It is unclear whether such a regulatory mechanism can apply to nuclear MAP kinase phosphatases and se rve as an additional apparatus for the feedback control of MAP kinase-media ted gene expression. Here we have shown that MKP-1 associates directly with p38 MAP kinase both in vitro and in vitro, and that this interaction enhan ces the catalytic activity of MKP-1. The point mutation Asp-316 --> Asn in the C-terminus of p38, analogous to the ERK2 (extracellular-signal-regulate d kinase 2) sevenmaker mutation, dramatically decreases its binding to MKP- 1 and substantially compromises its stimulatory effect on the catalytic act ivity of this phosphatase. Consistent with its defective interaction with M KP-1, this p38 mutant also displays greater resistance to dephosphorylation by the phosphatase. Our studies provide the first example of catalytic act ivation of a nuclear MAP kinase phosphatase through direct binding to a MAP kinase, suggesting that such a regulatory mechanism may play an important role in the feedback control of MAP kinase signalling in the nuclear compar tment.