Figure 5.

TrxR1 activity protects PTP1B inactivation during exposure to H₂O₂. A, protection of PTP1B from H₂O₂ requires only TrxR1 and NADPH. PTP1B was treated with H₂O₂ in the presence of various components of the Trx system and assayed for PTP activity as shown in Fig. 3B. Rates of inactivation with Trx1/TrxR1 or TrxR1 without NADPH were indistinguishable from that with PTP1B alone (Fig. 3B) (n = 3; mean ± S.E.; *, p < 0.05). B, reduced PTP1B cleaved and PTP1B catalytic domain variant (600 nm) were treated with the indicated concentrations of TrxR1 (0.5 μm) and 200 μm NADPH and exposed to 100 μm H₂O₂ for 5, 15, and 30 min (n = 3; mean ± S.E.; *, p < 0.05). C, concentration-dependent protection of PTP1B activity by TrxR1. Reduced PTP1B (600 nm) was treated with the indicated concentrations of TrxR1 and 200 μm NADPH and exposed to 100 μm H₂O₂ for 5 min (n = 3; mean ± S.E.; *, p < 0.05). D, reduced DEP-1 (80 nm) was treated with the indicated concentrations of TrxR1 (0.5 μm) and 200 μm NADPH, exposed to 150 μm H₂O₂ for 5 min, and then assayed for PTP activity as in panel A (n = 3; mean ± S.E.; *, p < 0.05).