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Specific inhibition of insulin-like growth factor-1 and insulin receptor tyrosine kinase activity and biological
M Párrizas1, A Gazit, A Levitzki
1Diabetes Branch, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, Maryland 20892, USA.
Abstract:
A series of the synthetic protein tyrosine kinase inhibitors known as tyrphostins were studied for their effect on insulin-like growth factor-1 and insulin-stimulated cellular proliferation on NIH-3T3 fibroblasts overexpressing either receptor, as well as for their ability to inhibit ligand-stimulated receptor autophosphorylation and tyrosine kinase activity toward exogenous substrates. Several of the tyrphostins tested demonstrated a dramatic effect by inhibiting hormone-stimulated cell proliferation, with IC50s in the submicromolar range, while being unable to block serum-stimulated cell proliferation. The tyrphostins also inhibited receptor autophosphorylation and tyrosine kinase activity, with a higher IC50, in the micromolar range. Most of the tyrphostins tested presented no clear preference for either receptor, although two of them (AG1024 and AG1034) showed significantly lower IC50s for IGF-1 than for insulin receptors. These results suggest that, in spite of the high homology of the kinase regions of both receptors, it could be possible to design and synthesize small molecules capable of discriminating between them. The synthesis of such specific inhibitors could be an excellent tool to establish the precise signalling mechanisms that distinguish between the different effects of these two hormones.
Insights
Tyrphostins, inhibitors of protein tyrosine kinases, effectively block insulin-like growth factor-1 and insulin signaling. Some tyrphostins show selectivity, offering potential for targeted therapies.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Protein tyrosine kinases are crucial in cellular signaling pathways.
- Insulin-like growth factor-1 (IGF-1) and insulin receptors share high homology in their kinase regions.
- Developing selective inhibitors for these receptors is challenging but important for understanding distinct hormonal effects.
Purpose of the Study:
- To investigate the effects of synthetic tyrphostins on IGF-1 and insulin signaling.
- To assess the ability of tyrphostins to inhibit receptor autophosphorylation and kinase activity.
- To explore the potential for designing selective inhibitors targeting either IGF-1 or insulin receptors.
Main Methods:
- Utilized NIH-3T3 fibroblasts overexpressing IGF-1 or insulin receptors.
- Tested tyrphostins for inhibition of hormone-stimulated cellular proliferation.
- Assessed inhibition of ligand-stimulated receptor autophosphorylation and tyrosine kinase activity.
- Determined IC50 values for proliferation and kinase inhibition.
Main Results:
- Several tyrphostins potently inhibited IGF-1 and insulin-stimulated proliferation (submicromolar IC50s).
- Tyrphostins were less effective at inhibiting serum-stimulated proliferation.
- Receptor autophosphorylation and kinase activity were inhibited in the micromolar range.
- Two compounds, AG1024 and AG1034, showed preferential inhibition of the IGF-1 receptor over the insulin receptor.
Conclusions:
- Tyrphostins can effectively inhibit IGF-1 and insulin signaling pathways.
- Selective inhibition of IGF-1 and insulin receptors is achievable despite kinase domain homology.
- Specific tyrphostin inhibitors could be valuable tools for elucidating distinct roles of IGF-1 and insulin.