Oxidative Stress-Induced Degradation of Thioredoxin-1 and Apoptosis Is Inhibited by Thioredoxin-1-Actin Interaction in Endothelial Cells

Objective-Thioredoxin-1 (Trx-1), one important antioxidative enzyme in endothelial cells, is required for apoptosis inhibition. Apoptosis induction is dependent on cytoskeletal changes, which depend on actin rearrangements. Therefore, we wanted to elucidate whether a physical interaction exists between Trx-1 and actin and what the functional consequences are. Methods and Results-Combined immunoprecipitation/mass spectrometry identified actin as a new binding partner for Trx-1. A separate pool of Trx-1 forms a complex with apoptosis signaling kinase 1. Actin is required for stress fiber formation; thus, the interaction of actin with Trx-1 might interfere with this process. Stress fiber formation, which is directly linked to the phosphorylation of focal adhesion kinase (FAK), occurs as early as 1 hour after H2O2 treatment. It is inhibited by Trx-1 overexpression, treatment with exogenous Trx-1, or inhibition of FAK. Prolonged incubation with H2O2 induced stress fiber formation, reduced Trx-1 protein levels, and increased apoptosis. All these processes were inhibited by preincubation with the FAK inhibitor PF573228. On the contrary, incubation with PF573228 1 hour after H2O2 treatment did not block stress fiber formation, degradation of Trx-1, or apoptosis. Conclusion-These data demonstrate that the actin-Trx-1 complex protects Trx-1 from degradation and, thus, endothelial cells from apoptosis. Reciprocally, Trx-1 prevents stress fiber formation. (Arterioscler Thromb Vasc Biol. 2011;31:650-656.)