REDOX PRIMING OF THE INSULIN-RECEPTOR BETA-CHAIN ASSOCIATED WITH ALTERED TYROSINE KINASE-ACTIVITY AND INSULIN RESPONSIVENESS IN THE ABSENCEOF TYROSINE AUTOPHOSPHORYLATION

Induction of tyrosine kinase activity of the insulin receptor (IR) bet a-chain is believed to require its autophosphorylation at Tyr(1162), T yr(1163), and Tyr(1158). However, the mechanism of the initial phospho rylation is poorly understood. We show that treatment of IR-transfecte d Chinese hamster ovary cells with antioxidants inhibits insulin respo nsiveness. Conversely, partial inhibition of glutathione biosynthesis by buthionine sulfoximine (BSO) and glutathione reductase by 1,3-bis- (2-chloroethyl)-l-nitrosourea (BCNU), i.e., procedures that intracellu larly induce mildly oxidative conditions, caused a decrease in IR beta -chain sulfhydryl groups and enhanced synergistically the induction of IR tyrosine phosphorylation by insulin. The IR beta-chain from cells treated with BSO/BCNU in the absence of insulin was not detectably tyr osine phosphorylated, but nevertheless was functionally altered, as de monstrated in vitro by a moderate kinase activity at low ATP concentra tions (5 nM) and a strong kinase activity at 25 mu M ATP. This activit y was found to be specific for tyrosine (not for serine or threonine), and tryptic peptide maps indicated that it is more selective than tha t induced by insulin. Moreover, the kinase activity from BSO/BCNU-trea ted cells showed a spontaneous decay that was not prevented by the pho sphatase inhibitor vanadate. Together, these results suggest that opti mal insulin responsiveness may require a process of 'redox priming' of the IR beta-chain that involves structural and functional changes in the absence of detectable tyrosine phosphorylation of the beta-chain.- Schmid, E., El Benna, J., Gaiter, D., Klein, G., Droge, W. Redox primi ng of the insulin receptor beta-chain associated with altered tyrosine kinase activity and insulin responsiveness in the absence of tyrosine autophosphorylation.