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Contortrostatin activates ERK2 and tyrosine phosphorylation events via distinct pathways
1Department of Biochemistry and Molecular Biology and Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California 90033, USA.
Abstract:
We report that cells adhering to contortrostatin show transient increases in activation of Extracellular signal Regulated Kinase 2 (ERK2). The kinetics and degree of activation are similar to cells adhering to fibronectin or vitronectin. We have recently shown that contortrostatin induces tyrosine phosphorylation in tumor cells. Contortrostatin is shown here to stimulate activation of ERK2 in suspended cells, but this activation follows a different dose-response pattern than contortrostatin-induced tyrosine phosphorylation. Since contortrostatin induces tyrosine phosphorylation via alphavbeta3, we explored the effects of an alphavbeta3-blocking antibody, 7E3, on contortrostatin-stimulated ERK2 activation. While 7E3 completely blocks the effect of contortrostatin on tyrosine phosphorylation, this antibody had no effect on activation of ERK2. In cells lacking expression of alphavbeta3, tyrosine phosphorylation was unaffected by contortrostatin treatment, but ERK2 was activated. This is strong evidence that contortrostatin is regulating tyrosine phosphorylation events and ERK2 activation via separate pathways and through different integrin receptors.
Insights
Contortrostatin binding to cells activates Extracellular signal Regulated Kinase 2 (ERK2) and tyrosine phosphorylation through distinct pathways. These processes involve different integrin receptors, indicating separate signaling mechanisms.
Area of Science:
- Cell biology
- Molecular signaling
- Integrin biology
Background:
- Contortrostatin is known to induce tyrosine phosphorylation in tumor cells.
- Integrins, such as alphavbeta3, are critical mediators of cell adhesion and signaling.
- Extracellular signal Regulated Kinase 2 (ERK2) is a key regulator of cellular processes.
Purpose of the Study:
- To investigate the signaling pathways activated by contortrostatin.
- To determine the role of the alphavbeta3 integrin in contortrostatin-induced ERK2 activation.
- To elucidate whether contortrostatin-induced tyrosine phosphorylation and ERK2 activation share common pathways.
Main Methods:
- Cell adhesion assays with contortrostatin, fibronectin, and vitronectin.
- Western blotting to assess ERK2 activation and tyrosine phosphorylation.
- Use of alphavbeta3-blocking antibody (7E3).
- Experiments with cells lacking alphavbeta3 expression.
Main Results:
- Cell adhesion to contortrostatin transiently increased ERK2 activation, similar to fibronectin or vitronectin.
- Contortrostatin activated ERK2 in suspended cells, but with a different dose-response than tyrosine phosphorylation.
- The alphavbeta3-blocking antibody 7E3 blocked contortrostatin-induced tyrosine phosphorylation but not ERK2 activation.
- In cells lacking alphavbeta3, contortrostatin still activated ERK2, while tyrosine phosphorylation remained unaffected.
Conclusions:
- Contortrostatin regulates tyrosine phosphorylation and ERK2 activation via separate signaling pathways.
- Different integrin receptors are likely involved in mediating these distinct cellular responses.
- The findings highlight the complex and divergent signaling initiated by contortrostatin binding to cell surface receptors.