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The MPM-2 antibody inhibits mitogen-activated protein kinase activity by binding to an epitope containing
1Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville 22908.
Abstract:
Mitogen-activated protein (MAP) kinases are a family of serine/threonine kinases implicated in the control of cell proliferation and differentiation. We have found that activated p42mapk is a target for the phosphoepitope antibody MPM-2, a monoclonal antibody that recognizes a cell cycle-regulated phosphoepitope. We have determined that the MPM-2 antibody recognizes the regulatory region of p42mapk. Binding of the MPM-2 antibody to active p42mapk in vitro results in a decrease in p42mapk enzymatic activity. The MPM-2 phosphoepitope can be generated in vitro on bacterially expressed p42mapk by phosphorylation with either isoform of MAP kinase kinase (MKK), MKK1, or MKK2. Analysis of p42mapk proteins mutated in their regulatory sites shows that phosphorylated Thr-183 is essential for the binding of the MPM-2 antibody. MPM-2 binding to Thr-183 is affected by the amino acid present in the other regulatory site, Tyr-185. Substitution of Tyr-185 with phenylalanine results in strong binding of the MPM-2 antibody, whereas substitution with glutamic acid substantially diminishes MPM-2 antibody binding. The MPM-2 phosphoepitope antibody recognizes an amino acid domain incorporating the regulatory phosphothreonine on activated p42mapk in eggs during meiosis and in mammalian cultured cells during the G0 to G1 transition.
Insights
The MPM-2 antibody targets activated p42mapk, a key regulator of cell growth. This antibody binding inhibits p42mapk activity, offering insights into cell cycle control.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mitogen-activated protein (MAP) kinases, including p42mapk, are crucial for regulating cell proliferation and differentiation.
- The MPM-2 antibody recognizes a specific phosphoepitope that appears during the cell cycle.
Purpose of the Study:
- To investigate the interaction between the MPM-2 antibody and activated p42mapk.
- To characterize the epitope recognized by MPM-2 and its effect on p42mapk activity.
Main Methods:
- In vitro binding assays using bacterially expressed p42mapk.
- Phosphorylation of p42mapk using MAP kinase kinase (MKK) isoforms.
- Analysis of p42mapk mutants to identify key regulatory sites.
Main Results:
- Activated p42mapk is recognized by the MPM-2 antibody, which binds to its regulatory region.
- MPM-2 binding inhibits p42mapk enzymatic activity.
- Phosphorylation of Thr-183 is essential for MPM-2 binding, which is modulated by Tyr-185.
Conclusions:
- The MPM-2 antibody recognizes a specific phosphoepitope on activated p42mapk involving Thr-183.
- This interaction impacts p42mapk activity and is relevant in cell cycle transitions like meiosis and G0 to G1.
- MPM-2 serves as a valuable tool for studying activated MAP kinases in various cellular contexts.