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Protein tyrosine phosphatase 1B interacts with and is tyrosine phosphorylated by the epidermal growth factor receptor
1Chemistry Department, Temple University, Philadelphia, PA 19122, USA.
Abstract:
We used a substrate-trapping technique to search for substrates of protein tyrosine phosphatase (PTP) 1B. A catalytically inactive form of this enzyme forms a stable, phosphotyrosine-dependent complex with epidermal growth factor receptor (EGFR) both in vitro and in cells. PTP1B also interacts with activated platelet-derived growth factor receptor (PDGFR) but not with colony-stimulating factor 1 receptor (CSF-1R). After binding to EGFR, PTP1B becomes tyrosine-phosphorylated at Tyr-66, a site that conforms to the consensus binding sequence for the Src homology 2 (SH2) domains of the adapter protein Grb2. This tyrosine phosphorylation is correlated with a 3-fold increase in PTP catalytic activity. These findings suggest that PTP1B selectively regulates specific activated receptor protein tyrosine kinases (RPTKs) in vivo and might itself be regulated by such receptors.
Insights
Protein tyrosine phosphatase (PTP) 1B selectively targets activated receptor protein tyrosine kinases (RPTKs), like epidermal growth factor receptor (EGFR). This interaction enhances PTP1B activity, suggesting a feedback mechanism in RPTK signaling.
Area of Science:
- Molecular Biology
- Cell Signaling
- Enzymology
Background:
- Protein tyrosine phosphatases (PTPs) are crucial regulators of cellular signaling pathways.
- PTP1B is a key enzyme implicated in various signaling cascades, including those involving receptor tyrosine kinases.
- Understanding the specific substrates and regulatory mechanisms of PTP1B is essential for deciphering its role in health and disease.
Purpose of the Study:
- To identify novel substrates of protein tyrosine phosphatase (PTP) 1B using a substrate-trapping approach.
- To investigate the interaction between PTP1B and activated receptor protein tyrosine kinases (RPTKs).
- To elucidate the regulatory mechanisms governing PTP1B activity by RPTKs.
Main Methods:
- Employed a substrate-trapping technique utilizing a catalytically inactive mutant of PTP1B.
- Investigated complex formation between PTP1B and various activated RPTKs, including epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), and colony-stimulating factor 1 receptor (CSF-1R) in vitro and in cell-based assays.
- Analyzed tyrosine phosphorylation of PTP1B upon binding to EGFR and assessed the impact on its catalytic activity.
Main Results:
- A catalytically inactive PTP1B formed stable complexes with activated EGFR and PDGFR, but not CSF-1R, indicating substrate specificity.
- PTP1B was tyrosine-phosphorylated at Tyr-66 upon binding to EGFR, a site compatible with Grb2 SH2 domain binding.
- This phosphorylation event correlated with a threefold increase in PTP1B's catalytic activity.
Conclusions:
- PTP1B selectively targets and dephosphorylates specific activated RPTKs in vivo.
- Activated RPTKs, particularly EGFR, can modulate PTP1B activity through tyrosine phosphorylation.
- These findings reveal a novel regulatory feedback loop where RPTKs control PTP1B function, impacting cellular signaling.