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Activation of a phosphotyrosine phosphatase by tyrosine phosphorylation
1Department of Molecular Biology, Max-Planck-Institut für Biochemie, Martinsried, Germany.
Abstract:
Regulation of cell proliferation, differentiation, and metabolic homeostasis is associated with the phosphorylation and dephosphorylation of specific tyrosine residues of key regulatory proteins. The phosphotyrosine phosphatase 1D (PTP 1D) contains two amino terminally located Src homology 2 (SH2) domains and is similar to the Drosophila corkscrew gene product, which positively regulates the torso tyrosine kinase signal transduction pathway. PTP activity was found to be regulated by physical interaction with a protein tyrosine kinase. PTP 1D did not dephosphorylate receptor tyrosine kinases, despite the fact that it associated with the epidermal growth factor receptor and chimeric receptors containing the extracellular domain of the epidermal growth factor receptor and the cytoplasmic domain of either the HER2-neu, kit-SCF, or platelet-derived growth factor beta (beta PDGF) receptors. PTP 1D was phosphorylated on tyrosine in cells overexpressing the beta PDGF receptor kinase and this tyrosine phosphorylation correlated with an enhancement of its catalytic activity. Thus, protein tyrosine kinases and phosphatases do not simply oppose each other's action; rather, they may work in concert to maintain a fine balance of effector activation needed for the regulation of cell growth and differentiation.
Insights
Protein tyrosine phosphatases (PTPs) like PTP 1D interact with protein tyrosine kinases, influencing cell signaling. This interaction enhances PTP 1D activity, suggesting a collaborative role in regulating cell growth and differentiation.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Cellular processes like proliferation and differentiation rely on protein phosphorylation and dephosphorylation.
- Phosphotyrosine phosphatase 1D (PTP 1D) shares similarities with Drosophila corkscrew, a regulator of tyrosine kinase pathways.
Purpose of the Study:
- To investigate the regulatory mechanisms of PTP 1D activity.
- To explore the interaction between PTP 1D and protein tyrosine kinases.
Main Methods:
- Studied PTP 1D association with various receptor tyrosine kinases (RTKs).
- Analyzed tyrosine phosphorylation of PTP 1D in cells overexpressing beta PDGF receptor kinase.
Main Results:
- PTP 1D associated with epidermal growth factor receptor and chimeric receptors but did not dephosphorylate RTKs.
- Tyrosine phosphorylation of PTP 1D was observed in cells overexpressing beta PDGF receptor kinase.
- This phosphorylation correlated with enhanced PTP 1D catalytic activity.
Conclusions:
- Protein tyrosine kinases and phosphatases may cooperate rather than oppose each other.
- This coordinated action is crucial for maintaining effector activation balance in cell growth and differentiation regulation.