Hutter D, Chen P, Barnes J, Liu Y
Stress Signaling Unit, Laboratory of Cellular and Molecular Biology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
Biochem J. 2000 Nov 15;352 Pt 1(Pt 1):155-63.
Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is the archetypal member of the dual-specificity protein phosphatase family, the expression of which can be rapidly induced by a variety of growth factors and cellular stress. Since MKP-1 protein localizes in the nucleus, it has been suggested to play an important role in the feedback control of MAP kinase-regulated gene transcription. Recently it has been demonstrated that the interaction of several cytosolic MAP kinase phosphatases with MAP kinases can trigger the catalytic activation of the phosphatases. It is unclear whether such a regulatory mechanism can apply to nuclear MAP kinase phosphatases and serve as an additional apparatus for the feedback control of MAP kinase-mediated gene expression. Here we have shown that MKP-1 associates directly with p38 MAP kinase both in vivo and in vitro, and that this interaction enhances the catalytic activity of MKP-1. The point mutation Asp-316-->Asn in the C-terminus of p38, analogous to the ERK2 (extracellular-signal-regulated kinase 2) sevenmaker mutation, dramatically decreases its binding to MKP-1 and substantially compromises its stimulatory effect on the catalytic activity of this phosphatase. Consistent with its defective interaction with MKP-1, this p38 mutant also displays greater resistance to dephosphorylation by the phosphatase. Our studies provide the first example of catalytic activation 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 compartment.
丝裂原活化蛋白（MAP）激酶磷酸酶-1（MKP-1）是双特异性蛋白磷酸酶家族的典型成员，其表达可被多种生长因子和细胞应激快速诱导。由于MKP-1蛋白定位于细胞核，因此有人认为它在MAP激酶调节的基因转录的反馈控制中起重要作用。最近有研究表明，几种胞质MAP激酶磷酸酶与MAP激酶的相互作用可触发磷酸酶的催化激活。目前尚不清楚这种调节机制是否适用于核MAP激酶磷酸酶，并作为MAP激酶介导的基因表达反馈控制的额外机制。在这里，我们已经表明，MKP-1在体内和体外都直接与p38 MAP激酶结合，并且这种相互作用增强了MKP-1的催化活性。p38 C末端的点突变Asp-316→Asn，类似于ERK2（细胞外信号调节激酶2）的七maker突变，显著降低了其与MKP-1的结合，并大大损害了其对该磷酸酶催化活性的刺激作用。与其与MKP-1的缺陷相互作用一致，这种p38突变体也表现出对该磷酸酶去磷酸化的更大抗性。我们的研究提供了通过直接与MAP激酶结合来催化激活核MAP激酶磷酸酶的第一个例子，表明这种调节机制可能在核区室中MAP激酶信号传导的反馈控制中起重要作用。
