Related Experiment Videos
Tpl-2 acts in concert with Ras and Raf-1 to activate mitogen-activated protein kinase
C Patriotis1, A Makris, J Chernoff
1Fox Chase Cancer Center, Philadelphia, PA 19111.
Abstract:
Mitogenic signals initiated at the plasma membrane by extracellular factors acting on receptor tyrosine kinases or G protein-coupled receptors are transmitted to the nucleus through an intricate signaling network. Components of this network participate, upon stimulation, in a complex array of phosphorylation-dependent protein-protein interactions which leads to the formation of transient multimolecular complexes. Complexes containing products of the protooncogenes ras and raf-1 and the protein kinase MEK-1 activate the mitogen-activated protein kinases (MAPKs), which play a central role in the integration of different mitogenic signals by directly phosphorylating cytoplasmic and nuclear targets. In this report we present evidence that the kinase encoded by the tumor progression locus 2 gene (Tpl-2) contributes to the activation of the MAPK cascade. MAPK activation induced by the Tpl-2 protein is blocked by dominant negative mutants of Ras and Raf-1, whereas a kinase-deficient Tpl-2 mutant down-regulates mitogenic signals induced by v-Ha-Ras or v-Raf. These data suggest that Tpl-2 activates the MAPK cascade, perhaps through its participation in the assembly of Ras/Raf-1-containing multimolecular complexes.
Insights
The tumor progression locus 2 (Tpl-2) gene product activates the mitogen-activated protein kinase (MAPK) cascade. Tpl-2
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Oncogenesis
Background:
- Mitogenic signals initiate at the plasma membrane via receptors like receptor tyrosine kinases and G protein-coupled receptors.
- These signals transmit to the nucleus through complex signaling networks involving phosphorylation-dependent protein-protein interactions.
- Transient multimolecular complexes form upon stimulation, integrating various signaling components.
Purpose of the Study:
- To investigate the role of the tumor progression locus 2 (Tpl-2) gene product in the activation of the mitogen-activated protein kinase (MAPK) cascade.
- To elucidate the mechanism by which Tpl-2 influences MAPK activation and mitogenic signaling.
Main Methods:
- Utilized dominant-negative mutants of Ras and Raf-1 to block Tpl-2-induced MAPK activation.
- Employed a kinase-deficient Tpl-2 mutant to assess its effect on v-Ha-Ras and v-Raf-induced mitogenic signals.
- Analyzed the formation of multimolecular complexes involving Ras and Raf-1.
Main Results:
- Tpl-2 protein contributes to the activation of the MAPK cascade.
- MAPK activation induced by Tpl-2 was inhibited by dominant-negative Ras and Raf-1 mutants.
- A kinase-deficient Tpl-2 mutant suppressed mitogenic signals induced by v-Ha-Ras or v-Raf.
Conclusions:
- Tpl-2 kinase activates the MAPK cascade.
- Tpl-2 likely participates in the assembly of Ras/Raf-1-containing multimolecular complexes to mediate its effects.
- These findings highlight Tpl-2's role in integrating and propagating mitogenic signals.