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TPCK and quercetin act synergistically with vanadate to increase protein-tyrosine phosphorylation in avian cells
J E Van Wart-Hood1, M E Linder, J G Burr
1Program in Molecular Biology, University of Texas, Dallas, Richardson 75080.
Abstract:
We have found four compounds that act synergistically with the phosphotyrosine phosphatase inhibitor sodium orthovanadate (Na3VO4) to greatly increase the extent of protein-tyrosine phosphorylation in both uninfected chick embryo fibroblasts (CEF) and their Rous sarcoma virus-transformed counterparts (RSV-CEF). These four inhibitors fall into two categories: the chymotrypsin-specific protease inhibitors, tosyl-phenylalanine-chloromethyl ketone (TPCK) and N-carbobenzoxy-1-phenylalanine-chloromethyl ketone (ZPCK); and certain bioflavonoids which can competitively inhibit ATP-binding, quercetin and phloretin.
Insights
Researchers identified four compounds that enhance protein-tyrosine phosphorylation when combined with sodium orthovanadate. These compounds include protease inhibitors and bioflavonoids, offering new insights into cellular signaling pathways.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Protein-tyrosine phosphorylation is a critical cellular signaling mechanism.
- Dysregulation of this process is implicated in various diseases, including cancer.
- Sodium orthovanadate is a known inhibitor of phosphotyrosine phosphatases.
Purpose of the Study:
- To identify compounds that synergistically enhance protein-tyrosine phosphorylation with sodium orthovanadate.
- To investigate the mechanisms of action of these synergistic compounds.
Main Methods:
- Experiments were conducted using uninfected chick embryo fibroblasts (CEF) and Rous sarcoma virus-transformed chick embryo fibroblasts (RSV-CEF).
- The effects of sodium orthovanadate in combination with various inhibitors were assessed.
- Compounds were categorized based on their known inhibitory mechanisms.
Main Results:
- Four compounds were found to significantly increase protein-tyrosine phosphorylation in synergy with sodium orthovanadate.
- These compounds included two chymotrypsin-specific protease inhibitors: tosyl-phenylalanine-chloromethyl ketone (TPCK) and N-carbobenzoxy-1-phenylalanine-chloromethyl ketone (ZPCK).
- Two bioflavonoids, quercetin and phloretin, which competitively inhibit ATP-binding, also demonstrated synergistic effects.
Conclusions:
- TPCK, ZPCK, quercetin, and phloretin act synergistically with sodium orthovanadate to enhance protein-tyrosine phosphorylation.
- These findings suggest potential therapeutic strategies targeting protein-tyrosine phosphorylation pathways.
- The identified compounds offer valuable tools for studying cellular signaling in both normal and transformed cells.