Redox priming of the insulin receptor β-chain associated with altered tyrosine kinase activity and insulin responsiveness in the absence of tyrosine autophosphorylation

Induction of tyrosine kinase activity of the insulin receptor (IR) β-chain is believed to require its autophosphorylation at Tyr1162, Tyr1163, and Tyr1158. However, the mechanism of the initial phosphorylation is poorly understood. We show that treatment of IR-transfected Chinese hamster ovary cells with antioxidants inhibits insulin responsiveness. Conversely, partial inhibition of glutathione biosynthesis by buthionine sulfoximine (BSO) and glutathione reductase by 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), i.e., procedures that intracellularly induce mildly oxidative conditions, caused a decrease in IR β-chain sulfhydryl groups and enhanced synergistically the induction of IR tyrosine phosphorylation by insulin. The IR β-chain from cells treated with BSO/BCNU in the absence of insulin was not detectably tyrosine phosphorylated, but nevertheless was functionally altered, as demonstrated in vitro by a moderate kinase activity at low ATP concentrations (5 nM) and a strong kinase activity at 25 μM ATP. ...