Protein phosphatase 2Cα inhibits the human stress-responsive p38 and JNK MAPK pathways
Protein phosphatase 2Cα inhibits the human stress-responsive p38 and JNK MAPK pathways
复制标题
DOI：
10.1093/emboj/17.16.4744
复制
发表时间：
1998-08-17
期刊：
影响因子：
11.4
通讯作者：
Saito, H
中科院分区：
文献类型：
--
作者：
Takekawa, M;Maeda, T;Saito, H
MAPK（丝裂原激活蛋白激酶）级联是常见的真核信号传导模块，由 MAPK、MAPKK 激酶 (MAPKK) 和 MAPKK 激酶 (MAPKKK) 组成。由于磷酸化对于 MAPKK 和 MAPK 的激活至关重要，因此蛋白磷酸酶可能是 MAPK 级联信号传导的重要调节剂。为了鉴定负向调节应激反应性 p38 和 JNK MAPK 级联的蛋白磷酸酶，我们使用过度激活的酵母突变体筛选了人类 cDNA 文库中下调酵母 HOG1 MAPK 途径的基因，该途径与 p38 和 JNK 途径具有相似性。在此筛选中，发现人蛋白磷酸酶 2C α 型 (PP2C α) 对酵母中的 HOG1 途径具有负调节作用。此外，当在哺乳动物细胞中表达时，PP2C α 抑制环境应激诱导的 p38 和 JNK 级联的激活。体内和体外观察均表明，PP2C α 使应激反应性 MAPK 级联中的 MAPKK（MKK6 和 SEK1）和 MAPK (p38) 去磷酸化并失活。此外，免疫共沉淀测定证实了 PP2C α 和 p38 的直接相互作用。仅当细胞受到应激刺激或使用催化失活的 PP2C α 突变体时才能观察到这种相互作用，这表明只有 p38 的磷酸化形式与 PP2C α 相互作用。
MAPK (mitogen-activated protein kinase) cascades are common eukaryotic signaling modules that consist of a MAPK, a MAPK kinase (MAPKK) and a MAPKK kinase (MAPKKK). Because phosphorylation is essential for the activation of both MAPKKs and MAPKs, protein phosphatases are likely to be important regulators of signaling through MAPK cascades. To identify protein phosphatases that negatively regulate the stress-responsive p38 and JNK MAPK cascades, we screened human cDNA libraries for genes that downregulated the yeast HOG1 MAPK pathway, which shares similarities with the p38 and JNK pathways, using a hyperactivating yeast mutant. In this screen, the human protein phosphatase type 2C alpha (PP2C alpha) was found to negatively regulate the HOG1 pathway in yeast. Moreover, when expressed in mammalian cells, PP2C alpha inhibited the activation of the p38 and JNK cascades induced by environmental stresses. Both in vivo and in vitro observations indicated that PP2C alpha dephosphorylated and inactivated MAPKKs (MKK6 and SEK1) and a MAPK (p38) in the stress-responsive MAPK cascades. Furthermore, a direct interaction of PP2C alpha and p38 was demonstrated by a co-immunoprecipitation assay. This interaction was observed only when cells were stimulated with stresses or when a catalytically inactive PP2C alpha mutant was used, suggesting that only the phosphorylated form of p38 interacts with PP2C alpha.