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Selective phosphotyrosine phosphatase inhibition and increased ceramide formation is associated with B-cell death by
G Dawson1, J Kilkus, G L Schieven
1Department of Pediatrics, University of Chicago, IL 60637, USA. dawg@midway.uchicago.edu
Abstract:
Bis(maltolato)oxovanadium(IV) (BMOV), a protein phosphotyrosine phosphatase inhibitor, selectively induced apoptosis (as quantitated by TUNEL staining) in a B-cell line (Ramos) but not in a T-cell line (Jurkat). The pattern of BMOV-induced protein tyrosine phosphorylation was different in B-cells versus T-cells. Further, BMOV induced a 2-fold increase in ceramide levels in B-cells but not in T-cells and this resembled the ceramide increase following activation of the B-cell antigen receptor. A 2-fold increase in the ratio of ceramide to sphingomyelin in B-cells treated with BMOV suggested that sphingomyelinase activation was the result of the sustained tyrosine phosphorylation of specific proteins and activated the cell death pathway.
Insights
Bis(maltolato)oxovanadium(IV) (BMOV) selectively triggers apoptosis in B-cells, not T-cells, by increasing ceramide levels. This suggests BMOV activates cell death pathways via sphingomyelinase in B-cells.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Protein phosphotyrosine phosphatases (PTPs) regulate crucial cellular processes.
- Dysregulation of PTPs is implicated in various diseases, including cancer.
- Vanadium compounds, like Bis(maltolato)oxovanadium(IV) (BMOV), are known PTP inhibitors.
Purpose of the Study:
- To investigate the selective effects of BMOV on apoptosis in different immune cell types.
- To elucidate the molecular mechanisms underlying BMOV-induced apoptosis.
- To explore the role of ceramide and sphingomyelinase in BMOV's action.
Main Methods:
- Utilized TUNEL staining to quantify apoptosis in B-cell (Ramos) and T-cell (Jurkat) lines.
- Analyzed protein tyrosine phosphorylation patterns in response to BMOV.
- Measured ceramide and sphingomyelin levels in B-cells and T-cells treated with BMOV.
Main Results:
- BMOV selectively induced apoptosis in Ramos B-cells but not in Jurkat T-cells.
- Distinct patterns of protein tyrosine phosphorylation were observed between B-cells and T-cells upon BMOV treatment.
- BMOV caused a twofold increase in ceramide levels and the ceramide/sphingomyelin ratio in B-cells, but not T-cells.
Conclusions:
- BMOV-induced apoptosis in B-cells is mediated by increased ceramide levels, likely through sphingomyelinase activation.
- Sustained tyrosine phosphorylation of specific proteins appears to trigger sphingomyelinase activation and the subsequent cell death pathway in B-cells.
- BMOV exhibits selective cytotoxicity towards B-cells, highlighting its potential as a targeted therapeutic agent.