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Activation of Stat3 by v-Src is through a Ras-independent pathway
J J Liu1, K Nakajima, T Hirano
1Institute of Molecular Medicine, National Taiwan University Medical School, Taipei, Taiwan, ROC.
Abstract:
V-Src induces tyrosine phosphorylation of various cellular proteins and activates a number of signaling molecules including the Jak family of proteins tyrosine kinases and Stat (signal transducers and activators of transcription) proteins. Many cellular effects elicited by v-Src are mediated through Ras, a molecular switch linking growth factor receptors and non-receptor tyrosine kinases to many downstream effectors. In this report, we demonstrated that v-H-Ras and v-Src both induced cellular transformation. However, the activation of Jak1 and Stat3 were only observed in v-Src transformed cells. Using reporter gene assays, we further showed that activation of Stat3 and possibly of Jak1 by v-Src were mediated through a Ras-independent pathway. As Stat3 activation has recently been shown to be required for cellular transformation by v-Src, our results suggest that activation of the Jak-Stat pathway may serve as a modulator in some but not all transformation processes.
Insights
V-Src and V-H-Ras both cause cellular transformation, but only V-Src activates Jak1 and Stat3. This Jak-Stat pathway activation by V-Src is Ras-independent, suggesting it modulates transformation.
Area of Science:
- Cellular biology
- Molecular oncology
- Signal transduction
Background:
- V-Src is a non-receptor tyrosine kinase known to induce cellular transformation.
- V-Src activates signaling molecules like Janus kinases (Jak) and signal transducers and activators of transcription (Stat) proteins.
- Ras proteins act as molecular switches, mediating many cellular effects of V-Src.
Purpose of the Study:
- To investigate the role of Ras in V-Src-induced cellular transformation.
- To determine if V-Src-mediated activation of Jak1 and Stat3 is dependent on Ras.
- To elucidate the contribution of the Jak-Stat pathway to cellular transformation.
Main Methods:
- Cellular transformation assays comparing V-Src and V-H-Ras.
- Analysis of Jak1 and Stat3 activation in transformed cells.
- Reporter gene assays to assess Ras-dependent and independent pathways.
Main Results:
- Both V-Src and V-H-Ras induced cellular transformation.
- Activation of Jak1 and Stat3 was observed exclusively in V-Src-transformed cells.
- V-Src-mediated activation of Stat3 and Jak1 occurred via a Ras-independent pathway.
Conclusions:
- V-Src activates the Jak-Stat pathway independently of Ras.
- The Jak-Stat pathway's activation by V-Src may modulate cellular transformation.
- This suggests the Jak-Stat pathway is not universally required for all transformation processes induced by V-Src.