Thioredoxin-1 functions as a molecular switch regulating the oxidative stress-induced activation of MST1

► Thioredoxin-1 (Trx1) physically interacts with the SARAH domain of MST1. ► Trx1 inhibits the reactive oxygen species-induced homodimerization of MST1. ► Trx1 negatively regulates the oxidative stress-induced activation of MST1.