Phosphorylation of Ser-446 determines stability of MKP-7
Phosphorylation of Ser-446 determines stability of MKP-7
复制标题
DOI：
10.1074/jbc.m500200200
复制
发表时间：
2005-04-15
影响因子：
4.8
通讯作者：
Shima, H
中科院分区：
文献类型：
--
作者：
Katagiri, C;Masuda, K;Shima, H
MAPK级联反应可由MAPK磷酸酶（MKP）家族成员负调控。然而，MKP活性是如何调节的还没有很好的表征。MKP-7是一种JNK特异性磷酸酶，除了在MKP家族成员中保守的结构域外，还具有独特的COOH末端延伸（CTS）。CTS包含几个基序，如核定位信号，核输出信号，PEST序列，和丝氨酸残基（Ser-446），可以被激活的ERK磷酸化，表明重要的调节作用。S-35-脉冲标记实验表明，MKP-7的半衰期为1.5小时，删除CTS后该时间段显著延长。我们还表明，过表达的MKP-7是多泛素化的，当与泛素共表达，蛋白酶体抑制剂显着抑制MKP-7降解。我们还确定了在Ser-446处磷酸化的MKP-7具有比野生型蛋白质的未磷酸化形式更长的半衰期，MKP-7的磷酸模拟突变体也是如此。这些结果表明，ERK途径的激活通过磷酸化介导的MKP-7的稳定化强烈阻断JNK激活。
MAPK cascades can be negatively regulated by members of the MAPK phosphatase (MKP) family. However, how MKP activity is regulated is not well characterized. MKP-7, a JNK-specific phosphatase, possesses a unique COOH-terminal stretch (CTS) in addition to domains conserved among MKP family members. The CTS contains several motifs such as a nuclear localization signal, a nuclear export signal, PEST sequences, and a serine residue (Ser-446) that can be phosphorylated by activated ERK, suggesting an important regulatory role(s). S-35-pulse labeling experiments indicate that the half-life of MKP-7 is 1.5 h, a period significantly elongated by deleting the CTS. We also show that overexpressed MKP-7 is polyubiquitinated when co-expressed with ubiquitin and that proteasome inhibitors markedly inhibit MKP-7 degradation. We also determined that MKP-7 phosphorylated at Ser-446 has a longer half-life than unphosphorylated form of the wild type protein, as does a phospho-mimic mutant of MKP-7. These results indicate that activation of the ERK pathway strongly blocks JNK activation through stabilization of MKP-7 mediated by phosphorylation.