Oxidative modifications of Nm23 regulate cellular functions

Abstract

Nm23 is a housekeeping enzyme having NDP kinase activity, and recently identified having many cellular functions such as metastasis suppressor, transactivation activity on c-myc and DNase. However, the regulatory mechanism of Nm23 was not well understood.In this study, I have examined protein modifications and interacting properties of Nm23 in response to oxidative stress.I have identified the formation of the intra-and inter-disulfide bonds of Nm23 in response to H_(2)O_(2) treatment in vivo and in vitro.The cross-linking sites of Nm23 were mapped using Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS).To investigate how the cross-linking of Nm23 is regulated, I examined the interacting proteins of Nm23 in response to oxidative stress.Thioredoxin reductase 1 (TR1) was identified as an interacting protein with only oxidized Nm23.It turns out that Nm23 is oxidized by reactive oxygen species and reversibly reduced by NADPH-TR1-Thioredoxin oxidoreduction shuttle system.This suggests that Nm23 can be a key molecule regulated by oxidative stress.