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pp54 microtubule-associated protein-2 kinase requires both tyrosine and serine/threonine phosphorylation for activity
J M Kyriakis1, D L Brautigan, T S Ingebritsen
1Diabetes Unit and Medical Services, Massachusetts General Hospital, Boston.
Abstract:
pp54 microtubule-associated protein-2 (MAP-2) kinase, a recently discovered protein serine/threonine kinase (Kyriakis, J., and Avruch, J. (1990) J. Biol. Chem. 265, 17355-17363), is shown to contain immunoreactive phosphotyrosine residues. Treatment with recombinant rat brain protein tyrosine phosphatase-1 deactivates pp54 MAP-2 kinase, concomitant with the removal of phosphotyrosine residues. Protein (serine/threonine) phosphatase-1 also deactivates pp54 MAP-2 kinase in a specific fashion. pp54 MAP-2 kinase joins pp42 MAP-2 kinase and cdc2/maturation-promoting factor as one of only three serine/threonine protein kinases known to be regulated by phosphorylation at both tyrosine and, independently, at serine/threonine residues. In view of these shared regulatory properties, a role for pp54 MAP-2 kinase in the control of cell division is likely.
Insights
pp54 microtubule-associated protein-2 (MAP-2) kinase is regulated by phosphorylation on both tyrosine and serine/threonine residues. This dual regulation suggests a role for this kinase in controlling cell division.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Microtubule-associated protein-2 (MAP-2) kinases are crucial regulators of cellular processes.
- pp54 MAP-2 kinase is a recently identified serine/threonine protein kinase.
- Understanding the regulatory mechanisms of pp54 MAP-2 kinase is essential for elucidating its cellular functions.
Purpose of the Study:
- To investigate the regulatory mechanisms of pp54 MAP-2 kinase.
- To determine if pp54 MAP-2 kinase is regulated by tyrosine phosphorylation.
- To identify phosphatases that can deactivate pp54 MAP-2 kinase.
Main Methods:
- Immunoreactivity assays were used to detect phosphotyrosine residues on pp54 MAP-2 kinase.
- Recombinant rat brain protein tyrosine phosphatase-1 was used to treat pp54 MAP-2 kinase.
- Protein (serine/threonine) phosphatase-1 was employed to assess its effect on pp54 MAP-2 kinase activity.
Main Results:
- pp54 MAP-2 kinase was found to contain immunoreactive phosphotyrosine residues.
- Treatment with protein tyrosine phosphatase-1 deactivated pp54 MAP-2 kinase and removed phosphotyrosine residues.
- Protein (serine/threonine) phosphatase-1 also specifically deactivated pp54 MAP-2 kinase.
Conclusions:
- pp54 MAP-2 kinase is regulated by phosphorylation at both tyrosine and serine/threonine residues.
- This dual phosphorylation regulation is similar to that of pp42 MAP-2 kinase and cdc2/maturation-promoting factor.
- pp54 MAP-2 kinase likely plays a role in the control of cell division due to its shared regulatory properties.