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The role of insulin receptor autophosphorylation in signal transduction
1Sloan Kettering Institute, Cornell Graduate School of Medical Sciences, New York, New York 10021.
Abstract:
We have examined the role of autophosphorylation in insulin signal transmission by oligonucleotide directed mutagenesis of seven potential tyrosine autophosphorylation sites in the human insulin receptor. Chinese hamster ovary cells transfected with these receptors were analyzed for insulin stimulated 2-deoxyglucose uptake, thymidine incorporation, endogenous substrate phosphorylation, and in vitro kinase activity. We found that phosphorylation on tyrosine residues 953, 1316, and 1322 were not necessary for receptor-mediated signal transduction. Mutation of tyrosine 960 reduced but did not abolish the signaling capabilities of the receptor. Finally, the simultaneous mutation of tyrosine residues 1146, 1150, and 1151 (the numbering system is that of Ullrich et al. (Ullrich, A., Bell, J. R., Chen, E. Y., Herrera, R., Petruzzelli, L. M., Dull, T. J., Gray, A., Coussens, L., Liao, Y. C., Tsubokawa, M., Mason, A., Seeburg, P.H., Grunfeld, C., Rosen, O. M., and Ramachandran, J. (1985) Nature 313, 756-761) resulted in a biologically inactive receptor, suggesting that the insulin receptor can be inactivated by removal of key autophosphorylation sites.
Insights
Autophosphorylation sites on the insulin receptor are crucial for signal transmission. Mutating key tyrosine residues (1146, 1150, 1151) inactivates the receptor, highlighting their importance in insulin signaling pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Insulin receptor (IR) autophosphorylation is essential for signal transduction.
- Specific tyrosine residues within the IR are implicated in its kinase activity and signaling.
- Understanding these sites is key to deciphering insulin action.
Purpose of the Study:
- To investigate the role of specific tyrosine autophosphorylation sites in human insulin receptor signaling.
- To determine which autophosphorylation sites are critical for insulin-mediated cellular responses.
Main Methods:
- Oligonucleotide-directed mutagenesis was used to alter seven potential tyrosine autophosphorylation sites in the human insulin receptor.
- Chinese hamster ovary (CHO) cells expressing mutated receptors were analyzed.
- Assays included insulin-stimulated 2-deoxyglucose uptake, thymidine incorporation, substrate phosphorylation, and in vitro kinase activity.
Main Results:
- Phosphorylation at tyrosine residues 953, 1316, and 1322 was not essential for insulin receptor-mediated signal transduction.
- Mutation of tyrosine 960 partially reduced but did not abolish signaling.
- Simultaneous mutation of tyrosine residues 1146, 1150, and 1151 resulted in a biologically inactive receptor.
Conclusions:
- Specific tyrosine autophosphorylation sites are critical for insulin receptor function.
- The cluster of tyrosine residues 1146, 1150, and 1151 appears to be essential for maintaining receptor activity.
- Removal of these key sites leads to receptor inactivation, underscoring their importance in insulin signal transmission.