The Effect Of Protein Tyrosine Nitration On Phosphorylation Involved In Insulin Signaling

Diabetes is a disease that seriously threaten human health, and usually accompanied with many complications that make it more difficult to cure. Insulin resistance, which a certain dose of insulin can not produce the expected biological effects, is the key feature of Type II diabetes. Reactive nitrogen species (RNS) can induce chronic inflammation and insulin resistance when the individual was challenged with oxidative stress. Peroxinitrite ions (ONOOˉ), a species of RNS, can cause the nitration of tyrosine residual of proteins. The effect of tyrosine nitration on phosphorylation signaling is likely to be the mechanism how RNS induce insulin resistance.In this paper, the effect of protein tyrosine nitration induced by peroxinitrite ions on the whole level of phosphorylation signaling in HepG2 cells was investigated by western blotting. Our results are as follows:Low concentration of peroxinitrite ions (10 to 50μM) can significantly inhibit the phosphorylation of insulin signaling proeins, while high concentration of peroxinitrite ions (higher than 200μM) promote the phosphorylation. Exogenetic nitration reagent such as peroxinitrite ions mainly cause the nitration of membrane proteins, and downregulate phosphorylation of proteins in cytosol. In addtion, our results demonstrate that selenite supplementation can evidently inhibit nitration.In vivo study showed that normal mouse liver presents the basic level of nitraiton, while in diabetic mouse liver the level of nitration has significantly increased.Sum up, low concentration of peroxinitrite ions nitrated membrane proteins in a dose dependent manner. Consequently, membrane signal transduction was attenuated, and phosphorylation level of tyrosine in cytosol was subsequently downregulated, finally induced insulin resistance. selenite supplementation can inhibit nitration, hence improve insulin sigaling and inhibit insulin resistance. High concentration of peroxinitrite ions can cause redox sigaling in addiotn to nitration, and its effect on phosphorylation signaling network may contribute to the increment of tyrosine phosphorylation level.