Vitamin D3 Up-Regulated Protein 1 Mediates Oxidative Stress Via Suppressing the Thioredoxin Function

Abstract

As a result of identifying the regulatory proteins of thioredoxin (TRX), a murine homologue for human vitamin D3 up-regulated protein 1 (VDUP1) was identified 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 Cys32 and Cys35 mutant TRX, suggesting the redox-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 was 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 proliferation-associated gene or TRX and ASK-1, suggesting its roles in cell proliferation and oxidative stress. To investigate the roles of mVDUP1 in oxidative stress, mVDUP1 was overexpressed in NIH 3T3 cells. When cells were exposed to stress, cell proliferation was declined with elevated apoptotic cell death compared with control cells. In addition, c-Jun N-terminal kinase activation and IL-6 expression were elevated. Taken together, these results demonstrate that mVDUP1 functions as an oxidative stress mediator by inhibiting TRX activity.

Two distinct mechanisms for loss of thioredoxin-binding protein-2 in oxidative stress-induced renal carcinogenesis

“…We believe that this is due to the fact that most of the previous studies assessed only TBP-2 mRNA, not protein. Studies showed increased levels of TBP-2 mRNA after oxidative stress 37 or glucose loading, 38 and a decrease in the mRNA level in several human [39][40][41] and animal tumors. 42 Re-evaluation of these experiments may be necessary because of the inconsistency between the mRNA and protein levels of TBP-2.…”

Thioredoxin-interacting protein mediates dysfunction of tubular autophagy in diabetic kidneys through inhibiting autophagic flux

“…[9][10][11][12] Thioredoxin-interacting protein (TXNIP) is a negative regulator of thioredoxin function, inhibiting its reducing capacity 13 and promoting cellular oxidative stress. TXNIP expression is ubiquitous and is induced by a variety of cellular stresses, including high intracellular glucose.…”

Thioredoxin-mediated Negative Autoregulation of Peroxisome Proliferator-activated Receptor α Transcriptional Activity

“…Inability of the overexpressed redox-inactive Trx in suppressing PPAR␣ activity ( Figure 6, A and B) suggests a critical role for the redox-active site (Cys32 and Cys35) of Trx. This conclusion was further supported by increased suppression of the binding activity of PPAR␣ to PPRE in vitro in the presence of TrxR, the primary enzyme catalyzing Trx reduction (Figure 8), and an increased inhibition of PPAR␣ transcriptional activity in the cells having Txnip, the endogenous redox inhibitor of Trx (Junn et al, 2000), knocked down by Txnip siRNA. Because TrxR and Txnip have been reported to be involved in promoting and blocking nuclear localization of Trx, respectively (Karimpour et al, 2002;Schulze et al, 2002), the observed enhanced inhibition PPAR␣ activity by TrxR and Txnip siRNA may be also due to an alteration of subcellular distribution of Trx.…”

“…It was found that the resulted PPAR␣ activity increased as goldthioglucose concentration increased ( Figure 6C). Furthermore, it was also investigated if Txnip, the negative modulator of Trx (Junn et al, 2000), affects the Trx-regulated PPAR␣ activity. Txnip siRNA was used to knockdown the endogenous Txnip.…”