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Pertussis toxin inhibits autophosphorylation and activation of the insulin receptor kinase
D Müller-Wieland1, M F White, B Behnke
1Klinik II und Poliklinik für Innere Medizin Universität zu Köln, FRG.
Abstract:
Pertussis toxin is an ADP-ribosyltransferase which alters the function of some of the GTP-binding proteins and inhibits some actions of insulin. In vivo, pertussis toxin (2 micrograms/ml/2h) inhibited insulin-stimulated tyrosyl autophosphorylation of the insulin receptor by 50% in FaO cells, and nearly completely inhibited phosphorylation of the cellular insulin receptor substrate pp185. Similarly, insulin-stimulated autophosphorylation and kinase activity of the insulin receptor purified on wheat germ agglutinin-agarose from pertussis toxin-treated FaO cells was diminished 50%; however, treatment of cells with the catalytically inactive B-oligomer of the toxin had no effect on receptor tyrosine kinase activity in vitro. Pertussis toxin did not alter insulin binding or the cellular levels of ATP, cAMP, and cGMP. Furthermore, immunoprecipitation of the insulin receptor from intact cells with anti-insulin receptor antibodies showed that pertussis toxin did not increase the phosphorylation of serine or threonine residues in the insulin receptor. These results suggest that pertussis toxin can modulate signal transduction of insulin at the level of the insulin receptor kinase.
Insights
Pertussis toxin inhibits insulin signaling by affecting the insulin receptor kinase activity. This toxin modulates insulin receptor autophosphorylation and substrate phosphorylation, impacting cellular responses.
Area of Science:
- Biochemistry
- Cellular Biology
- Molecular Endocrinology
Background:
- Pertussis toxin is an ADP-ribosyltransferase known to affect GTP-binding proteins.
- Insulin signaling is crucial for glucose metabolism and cellular function.
- Pertussis toxin has been observed to inhibit certain insulin actions.
Purpose of the Study:
- To investigate the effect of pertussis toxin on insulin receptor function.
- To determine the specific mechanism by which pertussis toxin interferes with insulin signaling.
Main Methods:
- Treatment of FaO cells with pertussis toxin in vivo.
- Analysis of insulin receptor autophosphorylation and substrate phosphorylation.
- Purification and in vitro kinase activity assays of the insulin receptor.
- Assessment of insulin binding and cellular energy levels (ATP, cAMP, cGMP).
Main Results:
- Pertussis toxin significantly inhibited insulin-stimulated tyrosyl autophosphorylation of the insulin receptor by 50% in FaO cells.
- Phosphorylation of the insulin receptor substrate pp185 was nearly completely inhibited by pertussis toxin.
- Insulin receptor kinase activity was diminished in cells treated with pertussis toxin, but not by its inactive B-oligomer.
- Pertussis toxin did not affect insulin binding, ATP, cAMP, or cGMP levels, nor did it increase serine/threonine phosphorylation of the insulin receptor.
Conclusions:
- Pertussis toxin modulates insulin signal transduction at the level of the insulin receptor kinase.
- The toxin's inhibitory effect on insulin signaling is mediated through its action on the receptor's tyrosine kinase activity.