Vitamin D-3 up-regulated protein 1 mediates oxidative stress via suppressing the thioredoxin function

As a result of identifying the regulatory proteins of thioredoxin (TRX), a murine homologue for human vitamin D-3 up-regulated protein 1 (VDUP1) was i dentified from a yeast two-hybrid screen. Cotransfection into 293 cells and precipitation assays confirmed that mouse VDUP1 (mVDUP1) bound to TRX, but it failed to bind to a Cys(32) and Cys(35) mutant TRX, suggesting the redo x-active site Is critical for binding. mVDUP1 was ubiquitously expressed in various tissues and located in the cytoplasm, Biochemical analysis showed that mVDUP1 inhibited the insulin-reducing activity of TRX, When cells were treated with various stress stimuli such as H2O2 and heat shock, mVDUP1 wa s significantly induced. TRX is known to interact with other proteins such as proliferation-associated gene and apoptosis signal-regulating kinase 1, Coexpression of mVDUP1 interfered with the interaction between TRX and prol iferation-associated gene or TRX and ASK-I, suggesting its roles in cell pr oliferation and oxidative stress, To investigate the roles of mVDUP1 in oxi dative stress, mVDUP1 was overexpressed in NIH 3T3 cells. When cells were e xposed to stress, cell proliferation was declined with elevated apoptotic c ell death compared with control cells, In addition, c-Jun N-terminal kinase activation and IL-6 expression were elevated. Taken together, these result s demonstrate that mVDUP1 functions as an oxidative stress mediator by inhi biting TRX activity.