Figure 8.

Stimulation of basal insulin receptor kinase activity by hydrogen peroxide or a shift in glutathione redox status. (a) Phosphorylation of recombinant IRK protein and myelin basic protein (MBP) substrate. The recombinant IRK protein was incubated at 30 °C for 20 min with or without 60 μM hydrogen peroxide (HP), then for 30 min with MBP and 1 mM ATP, and finally for 20 min with ³²P-ATP and MBP. (b) Intact CHO-HIR cells were cultured with 50 μM hydrogen peroxide (HP), 80 μM 1-(2-chloroethyl)-3-(2-hydroxyethyl)-1-nitrosourea, a specific inhibitor of glutathione reductase (BC), or no additives (Co). The insulin receptor was purified by immunoprecipitation and assayed for autophosphorylation (βIR) or substrate phosphorylation (MBP) by ³²P-incorporation or phosphotyrosine antibody (α-PY; data taken from Schmitt et al. 2005).