Interaction of the insulin receptor kinase with serine/threonine kinases in vitro

Hans U. Haring, Morris F. White, C. Ronald Kahn, Zafeer Ahmad, Anna A. DePaoli‐Roach, Peter J. Roach

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Abstract

Insulin causes rapid phosphorylation of the β subunit (Mr = 95,000) of its receptor in broken cell preparations. This occurs on tyrosine residues and is due to activation of a protein kinase which is contained in the receptor itself. In the intact cell, insulin also stimulates the phosphorylation of the receptor and other cellular proteins on serine and threonine residues. In an attempt to find a protein that might link the receptor tyrosine kinase to these serine/threonine phosphorylation reactions, we have studied the interaction of a partially purified preparation of insulin receptor with purified preparations of serine/threoine kinases known to phosphorylate glycogen synthase. No insulin‐dependent phosphorylation was ob served when casein kinases I and II, phosphorylase kinase, or glycogen synthase kinase 3 was incubated in vitro with the insulin receptor. These kinases also failed to phosphorylate the receptor. By contrast, the insulin receptor kinase catalyzed the phosphorylation of the calmodulin‐dependent kinase and addition of insulin in vitro resulted in a 40% increase in this phosphorylation. In the presence of calmodulin‐dependent kinase and the insulin receptor kinase, insulin also stimulated the phosphorylation of calmodulin. Phosphoamino acid analysis showed an increase of phosphotyrosine content in both calmodulin and calmodulindependent protein kinase. These data suggest that the insulin receptor kinase may interact directly and specifically with the calmodulin‐dependent kinase and calmodulin. Further studies will be required to determine if these phosphorylations modify the action of these regulatory proteins.

Original languageEnglish (US)
Pages (from-to)171-182
Number of pages12
JournalJournal of Cellular Biochemistry
Volume28
Issue number2
DOIs
StatePublished - 1985

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Keywords

  • insulin receptor
  • serine kinases
  • tyrosine phosphorylation

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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