Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The low-molecular-weight compound APR-246 (PRIMA-1(MET)) restores wild-type conformation and function to mutant p53, and triggers apoptosis in tumor cells. We show here that APR-246 also targets the selenoprotein thioredoxin reductase 1 (TrxR1), a key regulator of cellular redox balance. APR-246 inhibited both recombinant TrxR1 in vitro and TrxR1 in cells. A Sec-to-Cys mutant of TrxR1 was not inhibited by APR-246, suggesting targeting of the selenocysteine residue in wild-type TrxR1. Preheated APR-246 and its conversion product methylene quinuclidinone (MQ) were much more efficient TrxR1 inhibitors than APR-246 itself, indicating that MQ is the active compound responsible for TrxR1 enzyme inhibition. TrxR1 inhibited by MQ was still functional as a pro-oxidant NADPH oxidase. Knockdown of TrxR1 caused a partial and reproducible attenuation of APR-246-induced tumor cell death independently of p53 status. Cellular TrxR1 activity was also inhibited by APR-246 irrespective of p53 status. We show that APR-246 can directly affect cellular redox status via targeting of TrxR1. Our findings provide an explanation for the previously observed effects of APR-246 on tumor cells lacking mutant p53.
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PMID:APR-246/PRIMA-1MET inhibits thioredoxin reductase 1 and converts the enzyme to a dedicated NADPH oxidase. 2840 83

The mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a key enzyme in redox regulation, antioxidant defense, and cellular growth. TrxR1 can catalyze efficient reduction of juglone (5-hydroxy-1,4-naphthoquinone; walnut toxin) in a reaction which, in contrast to reduction of most other substrates of TrxR1, is not dependent upon an intact selenocysteine (Sec, U) residue of the enzyme. Using a number of TrxR1 mutant variants, we here found that a sole Cys residue at the C-terminal tail of TrxR1 is required for high-efficiency juglone-coupled NADPH oxidase activity of Sec-deficient enzyme, occurring with mixed one- and two-electron reactions producing superoxide. The activity also utilizes the FAD and the N-terminal redox active disulfide/dithiol motif of TrxR1. If a sole Cys residue at the C-terminal tail of TrxR1, in the absence of Sec, was moved further towards the C-terminal end of the protein compared to its natural position at residue 497, juglone reduction was, surprisingly, further increased. Ala substitutions of Trp407, Asn418 and Asn419 in a previously described "guiding bar", thought to mediate interactions of the C-terminal tail of TrxR1 with the FAD/dithiol site at the N-terminal domain of the other subunit in the dimeric enzyme, lowered turnover with juglone about 4.5-fold. Four residues of Sec-deficient TrxR1 were found to be easily arylated by juglone, including the Cys residue at position 497. Based upon our observations we suggest a model for involvement of the juglone-arylated C-terminal motif of TrxR1 to explain its high activity with juglone. This study thus provides novel insights into the catalytic mechanisms of TrxR1. One-electron juglone reduction by TrxR1 producing superoxide should furthermore contribute to the well-known prooxidant cytotoxicity of juglone.
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PMID:Details in the catalytic mechanism of mammalian thioredoxin reductase 1 revealed using point mutations and juglone-coupled enzyme activities. 2689 1