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Does mitogen-activated-protein kinase have a role in insulin action? The cases for and against
1Department of Biochemistry, School of Medical Sciences, University of Bristol, England.
Abstract:
The discovery of the mitogen-activated protein (MAP) kinase family of protein kinases has sparked off an intensive effort to elucidate their role in the regulation of many cellular processes. These protein kinases were originally identified based on their rapid activation by insulin. In this review we concentrate on examining the evidence for and against a role for the MAP kinases Erk-1 and Erk-2 in mediating the effects of insulin. While there is good evidence in favour of a direct role for MAP kinase in the growth-promoting effects of insulin and the regulation of Glut-1 and c-fos expression, and AP-1 transcriptional complex activity, this is by no means conclusive. MAP kinase may also play a role in the control of mRNA translation by insulin. On the other hand, the evidence suggests that MAP kinase is not sufficient for the acute regulation of glucose transport (Glut-4 translocation), glycogen synthesis, acetyl-CoA carboxylase or pyruvate dehydrogenase activity. The findings suggest that insulin may utilise at least three distinct signalling pathways which do not involve MAP kinase.
Insights
Mitogen-activated protein (MAP) kinases, including Erk-1 and Erk-2, are investigated for their role in insulin signaling. While MAP kinases influence some insulin effects like growth and gene expression, they do not mediate all, suggesting alternative insulin pathways.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Endocrinology
Background:
- Mitogen-activated protein (MAP) kinases are crucial regulators of cellular processes.
- These kinases were initially identified by their rapid activation in response to insulin.
- Understanding the precise role of MAP kinases in insulin action is critical.
Purpose of the Study:
- To review and critically evaluate the evidence for and against the involvement of MAP kinases (Erk-1 and Erk-2) in mediating insulin's effects.
- To delineate which specific insulin-induced cellular responses are regulated by MAP kinases.
Main Methods:
- Literature review and critical analysis of existing research findings.
- Examination of studies investigating MAP kinase activation by insulin.
- Assessment of the correlation between MAP kinase activity and various insulin-regulated cellular processes.
Main Results:
- Evidence supports a role for MAP kinase in insulin's growth-promoting effects, regulation of Glut-1 expression, c-fos expression, and AP-1 transcriptional complex activity.
- MAP kinase may also be involved in insulin-mediated control of mRNA translation.
- MAP kinase is insufficient for acute regulation of glucose transport (Glut-4 translocation), glycogen synthesis, acetyl-CoA carboxylase, and pyruvate dehydrogenase activity.
Conclusions:
- Insulin likely employs multiple signaling pathways, with MAP kinase mediating some but not all of its effects.
- At least three distinct insulin signaling pathways independent of MAP kinase are suggested.
- Further research is needed to fully elucidate the complex insulin signaling network.