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Proc Natl Acad Sci U S A. 1986 Aug;83(16):5822-4.

Protein kinase C directly phosphorylates the insulin receptor in vitro and reduces its protein-tyrosine kinase activity.


The beta subunit of purified insulin receptor is phosphorylated on a serine residue by purified preparations of protein kinase C (ATP: protein phosphotransferase, EC This phosphorylation is inhibited by antibodies to protein kinase C and stimulated by phospholipids, diacylglycerol, and Ca2+. The phosphorylation of the receptor by protein kinase C does not affect its insulin-binding activity but does inhibit by 65% the receptor's intrinsic tyrosine-specific protein kinase activity (ATP: protein-tyrosine O-phosphotransferase, EC These results indicate that activators of protein kinase C, such as phorbol esters, desensitize cells to insulin by direct protein kinase C action on the insulin receptor.

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