Reactivation of oxidized PTP1B and PTEN by thioredoxin 1

The transient inactivation of protein phosphatases contributes to the efficiency and temporal control of kinase-dependent signal transduction. In particular, members of the protein tyrosine phosphatase family are known to undergo reversible oxidation of their active site cysteine. The thiol oxidation step requires activation of colocalized NADPH oxidases and is mediated by locally produced reactive oxygen species, in particular H2O 2. How oxidized phosphatases are returned to the reduced active state is less well studied. Both major thiol reductive systems, the thioredoxin and the glutathione systems, have been implicated in the reactivation of phosphatases. Here, we show that the protein tyrosine phosphatase PTP1B and the dual-specificity phosphatase PTEN are preferentially reactivated by the thioredoxin system. We show that inducible depletion of thioredoxin 1(TRX1) slows PTEN reactivation in intact living cells. Finally, using a mechanism-based trapping approach, we demonstrate direct thiol disulphide exchange between the active sites of thioredoxin and either phosphatase. The application of thioredoxin trapping mutants represents a complementary approach to direct assays of PTP oxidation in elucidating the significance of redox regulation of PTP function in the control of cell signaling. Structured digital abstract TRX1 physically interacts with PTP1B by anti tag coimmunoprecipitation (1, 2) The reversible oxidation of the active site cysteine of protein tyrosine phosphatases (PTPs) allows for their transient inactivation and provides an important mechanism for coordinating the amplitude and duration of cellular signaling. However, the precise mechanism by which PTPs are returned to their reduced and active states has remained unknown. In this issue, Schwertassek and colleagues demonstrate that the prototypic PTP1B and the dual-specificity lipid phosphatase PTEN are preferentially reduced by thioredoxin-1. In the process, they develop an approach for determining both the extent and the identity of PTPs oxidized in living cells