Guan K L, Butch E
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606, USA.
J Biol Chem. 1995 Mar 31;270(13):7197-203. doi: 10.1074/jbc.270.13.7197.
The mitogen-activated protein kinase (MAPK) also known as extracellular signal-regulated kinase (ERK) plays a crucial role in various signal transduction pathways. ERK is activated by its upstream activator, MEK, via threonine and tyrosine phosphorylation. ERK activity in the cell is tightly regulated by phosphorylation and dephosphorylation. Here we report the cloning and characterization of a novel dual specific phosphatase, HVH2, which may function in vivo as a MAP kinase phosphatase. The deduced amino acid sequence of HVH2 shows significant identity to the VH1-related dual specific phosphatase family. In addition, the N-terminal region of HVH2 also displays sequence identity to the cell cycle regulator, Cdc25 phosphatase. Recombinant HVH2 phosphatase exhibited a high substrate specificity toward activated ERK and dephosphorylated both threonine and tyrosine residues of activated ERK1 and ERK2. Immunofluorescence studies with an epitope-tagged HVH2 showed that the enzyme was localized in cell nucleus. Transfection of HVH2 into NIH3T3 cells inhibited the v-src and MEK-induced transcriptional activation of serum-responsive element containing promoter, consistent with the notion that HVH2 promotes the inactivation of MAP kinase. HVH2 mRNA showed an expression pattern distinct from CL100 (human homologue of mouse MKP1) and PAC1, two previously identified MAP kinase phosphatases. Our data suggest a possible role of HVH2 in MAP kinase regulation.
丝裂原活化蛋白激酶（MAPK）也被称为细胞外信号调节激酶（ERK），在各种信号转导途径中起着关键作用。ERK通过其上游激活剂MEK，经苏氨酸和酪氨酸磷酸化而被激活。细胞内的ERK活性受到磷酸化和去磷酸化的严格调控。在此，我们报告了一种新型双特异性磷酸酶H VH2的克隆与特性，它在体内可能作为一种MAP激酶磷酸酶发挥作用。H VH2推导的氨基酸序列与VH1相关双特异性磷酸酶家族具有显著的同源性。此外，H VH2的N端区域与细胞周期调节因子Cdc25磷酸酶也显示出序列同源性。重组H VH2磷酸酶对活化的ERK表现出高底物特异性，并使活化的ERK1和ERK2的苏氨酸和酪氨酸残基去磷酸化。用表位标记的H VH2进行的免疫荧光研究表明，该酶定位于细胞核。将H VH2转染到NIH3T3细胞中可抑制v-src和MEK诱导的含血清反应元件启动子的转录激活，这与H VH2促进MAP激酶失活的观点一致。H VH2 mRNA的表达模式与CL100（小鼠MKP1的人类同源物）和PAC1这两种先前鉴定的MAP激酶磷酸酶不同。我们的数据表明H VH2在MAP激酶调节中可能发挥作用。
