H oxidase?X Peng1,4, M-Q-Z Zhang2,4, F Conserva2,four, G Hosny2, G Selivanova3, VJN Bykov2, ESJ Arner*,1 and KG Wiman*,The low-molecular-weight compound APR-246 (PRIMA-1MET) restores wild-type conformation and function to mutant p53, and triggers apoptosis in tumor cells. We show right here that APR-246 also targets the selenoprotein thioredoxin reductase 1 (TrxR1), a essential regulator of cellular redox balance. APR-246 inhibited each recombinant TrxR1 in vitro and TrxR1 in cells. A Sec-to-Cys mutant of TrxR1 was not inhibited by APR-246, suggesting targeting on the selenocysteine residue in wild-type TrxR1. Preheated APR-246 and its conversion product methylene quinuclidinone (MQ) have been a lot far more efficient TrxR1 inhibitors than APR-246 itself, indicating that MQ could be the active compound accountable for TrxR1 enzyme inhibition. TrxR1 inhibited by MQ was nevertheless functional as a pro-oxidant NADPH oxidase. Knockdown of TrxR1 brought on a partial and reproducible attenuation of APR-246induced 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 by means of targeting of TrxR1. Our findings offer an explanation for the previously observed effects of APR-246 on tumor cells lacking mutant p53. Cell Death and Disease (2013) four, e881; doi:10.1038/cddis.2013.417; published online 24 OctoberSubject Category: CancerThe tumor suppressor p53 is often inactivated by missense or nonsense mutations in human tumors,1? permitting tumor cell survival and progression to additional malignant variants.5-Oxaspiro[3.5]nonan-8-amine Order Additionally, p53 mutation is amongst the key causes behind resistance to chemotherapy and radiotherapy.four,5 Restoration of wild-type p53 function triggers speedy tumor regression in vivo.6? Thus, mutant p53 is really a promising target for novel enhanced cancer therapy. Quite a few smaller molecules happen to be shown to restore wild-type activity to mutant p53, like CP-31398,9 PRIMA-1 and APR-246 (PRIMA-1MET),10?two MIRA,13 STIMA,14 PhiKan-08315 and NSC319726,16 but in most instances their mechanisms of action are poorly understood. PRIMA-1 and its methylated analog APR-246 market correct folding of mutant p53, induce cell death by apoptosis, and inhibit tumor growth in mice.10,12,17 APR-246 has also been shown to reactivate mutant types of your p63 and p73 proteins that share high structural homology with p53.1301214-72-1 structure 18,19 APR-246 has been tested in a phase I/II clinical trial in sufferers with hematological malignancies or hormonerefractory prostate cancer.PMID:23543429 20 PRIMA-1 and APR-246 are both converted to methylene quinuclidinone (MQ), a Michael acceptor that covalently binds to cysteine (Cys) residues in p53 (wild-type or mutant), and such modification per se is adequate to reactivate mutant p53.21 MIRA-1 and STIMA-also have Michael acceptor activity, even though their covalent modification of p53 has not yet been confirmed. The observation that MQ binds covalently to Cys residues in p53 raises the query no matter whether MQ also has other targets in tumor cells. Thioredoxin reductase 1 (TrxR1), which catalyzes the reduction of thioredoxin employing NADPH, is definitely an important regulator of redox balance in cells.22 TrxR1 is expressed as a homodimer in mammalian cells with a selenocysteine (Sec)containing C-terminal active site motif and a dithiol motif at the N terminus in each and every subunit. Within the catalytic reaction, NADPH transfers electrons to the N-terminal motif of each and every subunit and subsequently t.
