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Protein tyrosine kinases and phosphatases control apoptosis induced by extracellular adenosine 5'-triphosphate
1Institute of Oncology, Inter-University Center for Cancer Research, Padova, Italy.
Abstract:
Extracellular ATP (ATPo) induces apoptosis and osmotic lysis in several cell lines. We investigated the role of protein tyrosine kinases (PTKs) and phosphatases (PTPases) in ATPo-induced apoptosis. The PTK inhibitor genistein prevented DNA fragmentation due to ATPo without affecting cell lysis. Comparison of western blot analysis and in vitro kinase assays of anti-phosphotyrosine immunoprecipitates indicated that ATPo activated PTKs whose activity was tightly regulated by PTPases. In fact, an early increase in tyrosine kinase activity was observed after ATPo-treatment and was prevented by specific PTPase inhibitors. In addition, a rapid dephosphorylation of phosphotyrosyl residues on several proteins was detected in ATPo-treated cells. Accordingly, inhibitors of PTPases, but not of serine/threonine phosphatases, were as effective as PTK-inhibitors in blocking ATPo-mediated DNA fragmentation. We describe the early events occurring in ATPo-induced apoptosis and suggest a role for PTPases in cell death.
Insights
Extracellular ATP (ATPo) triggers cell death pathways. Protein tyrosine phosphatases (PTPases) play a crucial role in regulating ATPo-induced apoptosis by controlling protein tyrosine kinase (PTK) activity, suggesting PTPases are key to cell death.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Extracellular ATP (ATPo) is known to induce apoptosis and osmotic lysis in various cell lines.
- The precise molecular mechanisms underlying ATPo-induced apoptosis are not fully elucidated.
- The roles of protein tyrosine kinases (PTKs) and phosphatases (PTPases) in this process require further investigation.
Purpose of the Study:
- To investigate the involvement of PTKs and PTPases in ATPo-induced apoptosis.
- To elucidate the early molecular events and signaling pathways activated by extracellular ATP.
- To determine the regulatory role of PTPases in ATPo-mediated cell death.
Main Methods:
- Utilized genistein, a PTK inhibitor, to assess its effect on ATPo-induced DNA fragmentation and cell lysis.
- Employed western blot analysis and in vitro kinase assays on anti-phosphotyrosine immunoprecipitates to measure PTK activity.
- Investigated the impact of specific PTPase inhibitors and serine/threonine phosphatase inhibitors on ATPo-treated cells.
Main Results:
- Genistein inhibited DNA fragmentation but not cell lysis, indicating a specific role in apoptosis.
- ATPo treatment led to an early activation of PTKs, which was suppressed by PTPase inhibitors.
- A rapid dephosphorylation of phosphotyrosyl residues on multiple proteins was observed in ATPo-treated cells.
- PTPase inhibitors, but not serine/threonine phosphatase inhibitors, effectively blocked ATPo-mediated DNA fragmentation.
Conclusions:
- Protein tyrosine kinases (PTKs) are activated early in extracellular ATP (ATPo)-induced apoptosis.
- Protein tyrosine phosphatases (PTPases) play a critical regulatory role in controlling PTK activity during ATPo-induced cell death.
- PTPases are implicated as key mediators in the early events of ATPo-induced apoptosis.