Related Experiment Videos
Isolation and characterization of a novel dual specific phosphatase, HVH2, which selectively dephosphorylates the
1Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606, USA.
Abstract:
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.
Insights
Researchers identified a new phosphatase, HVH2, that specifically dephosphorylates and inactivates mitogen-activated protein kinase (MAPK) or extracellular signal-regulated kinase (ERK). This discovery sheds light on MAPK regulation within the cell nucleus.
Area of Science:
- Cellular signaling
- Molecular biology
- Enzymology
Background:
- Mitogen-activated protein kinase (MAPK), also known as extracellular signal-regulated kinase (ERK), is vital for signal transduction.
- ERK activation involves MEK-mediated phosphorylation on threonine and tyrosine residues.
- Tight regulation of ERK activity is achieved through phosphorylation and dephosphorylation.
Purpose of the Study:
- To clone and characterize a novel dual-specific phosphatase, HVH2.
- To investigate HVH2's potential role as a MAP kinase phosphatase in vivo.
- To understand HVH2's substrate specificity and cellular localization.
Main Methods:
- Cloning and sequence analysis of the HVH2 gene.
- Recombinant HVH2 phosphatase activity assays using activated ERK1 and ERK2.
- Immunofluorescence studies to determine HVH2 subcellular localization.
- Cell transfection assays to assess HVH2's effect on transcriptional activation.
Main Results:
- HVH2 dephosphorylates both threonine and tyrosine residues of activated ERK1 and ERK2 with high specificity.
- HVH2 localizes to the cell nucleus.
- HVH2 transfection inhibits v-src and MEK-induced transcriptional activation, indicating MAP kinase inactivation.
- HVH2 exhibits a distinct mRNA expression pattern compared to other known MAP kinase phosphatases.
Conclusions:
- HVH2 functions as a novel MAP kinase phosphatase.
- HVH2 plays a role in regulating MAP kinase signaling pathways.
- HVH2's nuclear localization and specific phosphatase activity suggest a key role in controlling cellular responses mediated by MAPKs.