The structural basis for the negative regulation of thioredoxin by thioredoxin-interacting protein

Abstract

The redox-dependent inhibition of thioredoxin (TRX) by thioredoxin-interacting protein (TXNIP) plays a pivotal role in various cancers and metabolic syndromes. However, the molecular mechanism of this regulation is largely unknown. Here, we present the crystal structure of the TRX–TXNIP complex and demonstrate that the inhibition of TRX by TXNIP is mediated by an intermolecular disulphide interaction resulting from a novel disulphide bond-switching mechanism. Upon binding to TRX, TXNIP undergoes a structural rearrangement that involves switching of a head-to-tail interprotomer Cys63-Cys247 disulphide between TXNIP molecules to an interdomain Cys63-Cys190 disulphide, and the formation of a de novo intermolecular TXNIP Cys247-TRX Cys32 disulphide. This disulphide-switching event unexpectedly results in a domain arrangement of TXNIP that is entirely different from those of other arrestin family proteins. We further show that the intermolecular disulphide bond between TRX and TXNIP dissociates in the presence of high concentrations of reactive oxygen species. This study provides insight into TRX and TXNIP-dependent cellular regulation.

A unique PDZ domain and arrestin-like fold interaction reveals mechanistic details of endocytic recycling by SNX27-retromer

“…Thus, our structure presents a unique example of a PDZ domain insertion mediating the interaction with a distinct protein family. In addition, our structure adds to recent insights into arrestin family ligand interactions that have revealed how different members of the arrestin-like protein family provide distinct surfaces for binding their respective partners by apparently diverse mechanisms (34,35). As shown in Fig.…”

mTOR and HDAC Inhibitors Converge on the TXNIP/Thioredoxin Pathway to Cause Catastrophic Oxidative Stress and Regression of RAS-Driven Tumors

“…3A). Interestingly, the TXNIP protein binds and inhibits thioredoxin (TRX), a second major cellular anti-oxidant (37). Moreover, the TRX/TXNIP system plays a major role in regulation of redox homeostasis and TXNIP has been shown to mediate cell death caused by oxidative stress in some settings (38,39).…”

Crystal structure of fully oxidized human thioredoxin

“…Although our original aim to solve the structure of the N-terminal domain of TXNIP complexed with TRX failed due to the transient nature of the interaction between the two proteins [11], we were fortunate to be able to determine the structure of the fully oxidized TRX.…”

“…The plasmid co-expressing TRX and the N-terminal domain of TXNIP (residues 3-156) was constructed using a two-promoter vector system as described in a previous study [11].…”

“…Recently, we reported the molecular mechanism of the negative regulation of TRX by the TRX-interacting protein (TXNIP), the only known endogenous inhibitor of TRX [11,12].…”