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Growth factor-induced activation of a kinase activity which causes regulatory phosphorylation of
1Department of Microbiology, University of Virginia, Charlottesville 22908.
Abstract:
p42/microtubule-associated protein kinase (p42mapk) is activated by tyrosine and threonine phosphorylation, and its regulatory phosphorylation is likely to be important in signalling pathways involved in growth control, secretion, and differentiation. Here we show that treatment of quiescent 3T3 cells with diverse agonists results in the appearance of an activity capable of causing the in vitro phosphorylation of p42mapk on the regulatory tyrosine and to a lesser extent on the regulatory threonine, resulting in enzymatic activation of the p42mapk. This p42mapk-activating activity is capable of phosphorylating a kinase-defective p42mapk mutant, thus confirming its activity as a kinase.
Insights
Diverse agonists activate p42/microtubule-associated protein kinase (p42mapk) through regulatory phosphorylation. This kinase activity is crucial for cell signaling pathways controlling growth, secretion, and differentiation.
Area of Science:
- Cellular signaling
- Molecular biology
- Biochemistry
Background:
- p42/microtubule-associated protein kinase (p42mapk) is a key regulator of cellular processes.
- Its activation involves specific tyrosine and threonine phosphorylation events.
- Understanding p42mapk regulation is vital for comprehending cell growth, secretion, and differentiation.
Purpose of the Study:
- To investigate the signaling pathways that activate p42mapk.
- To identify the nature of the activity responsible for p42mapk phosphorylation and activation.
Main Methods:
- Treatment of quiescent 3T3 cells with various agonists.
- In vitro phosphorylation assays using p42mapk and a kinase-defective mutant.
- Analysis of tyrosine and threonine phosphorylation on p42mapk.
Main Results:
- Diverse agonists induced an activity that phosphorylates p42mapk on regulatory tyrosine and threonine residues.
- This phosphorylation resulted in the enzymatic activation of p42mapk.
- The identified activity was confirmed as a kinase by phosphorylating a kinase-defective p42mapk mutant.
Conclusions:
- A novel kinase activity is responsible for the agonist-induced activation of p42mapk.
- This activation mechanism plays a significant role in cellular signaling pathways.
- The findings provide insights into the regulation of cell growth, secretion, and differentiation.