Regulation of Interferon and Retinoic Acid-induced Cell Death Activation through Thioredoxin Reductase

Abstract

Interferons (IFNs) and retinoids are potent biological response modifiers. The IFN-␤ and all-trans-retinoic acid combination, but not these single agents individually, induces death in several tumor cell lines. To elucidate the molecular basis for these actions, we have employed an antisense knockout approach to identify the gene products that mediate cell death and isolated several genes associated with retinoid-IFN-induced mortality (GRIMs). One of the GRIM cDNAs, GRIM-12, was identical to human thioredoxin reductase (TR). To define the functional relevance of TR to cell death and to define its mechanism of death-modulating functions, we generated mutants of TR and studied their influence on the IFN/RA-induced death regulatory functions of caspases. Wild-type TR activates cell death that was inhibited in the presence of caspase inhibitors or catalytically inactive caspases. A mutant TR, lacking the active site cysteines, inhibits the cell death induced by caspase 8. IFN/all-trans-retinoic acid-induced cytochrome c release from the mitochondrion was promoted in the presence of wild type and was inhibited in the presence of mutant TR. We find that TR modulates the activity of caspase 8 to promote death. This effect is in part caused by the stimulation of death receptor gene expression. These studies identify a new mechanism of cell death regulation by the IFN/all-trans-retinoic acid combination involving redox enzymes.

RETRACTED: Identification and characterization of GRIM-1, a cell-death-associated gene product

“…Loss of permeability of the mitochondrial membrane results in a release of apoptogenic proteins -including cytochrome c (Kluck et al, 1997;Liu et al, 1996), which is required for the activation of caspase-9. In our earlier studies, we have shown activation of caspase-9 (Angell et al, 2000;Ma et al, 2007) and cytochrome-c release in response to IFN/RA (Ma et al, 2001). In this study, we have shown that mutant caspase-9 and Bcl2 block the processing of GRIM-1.…”

“…GRIM-12 was required for keeping the active sites of caspases in reduced state through its substrate thioredoxin (Ma et al, 2001). The second protein, GRIM-19, inhibits transcription factor STAT3 (Zhang et al, 2003), a protein known to upregulate the expression of mitochondrial antiapoptotic regulators Bcl2, Bcl-X L and Mcl-1.…”

“…Consistent with these observations, Bcl2 blocked and Bax enhanced IFN/RA-induced and GRIM-1-dependent apoptosis. Indeed, our earlier studies have shown caspase-9 activation and release of cytochrome c in response to IFN/RA (Angell et al, 2000;Ma et al, 2001). Caspases specifically cleave peptides after aspartic-acid residues (Nicholson and Thornberry, 1997).…”

“…Mitochondrial damage followed by apoptosome formation promotes the cleavage of GRIM-1. GRIM-12 activity maintains caspase-9 in an active state by providing the reducing power (Ma et al, 2001), promoting caspase-9 activity during IFN/RA treatment.…”

Tumor-Suppressive Activity of the Cell Death Activator GRIM-19 on a Constitutively Active Signal Transducer and Activator of Transcription 3

“…Because STAT3 is known to activate the genes involved in cell proliferation and inhibition of apoptosis, the GRIM-19 effects on STAT3C-induced cell growth are probably exerted through an inhibition of these processes. These results are consistent with other reports that the fas gene is repressed by STAT3 (36) and IFN/RA treatment induces Fas and Fas ligand expression in cells (37), which can suppress tumor growth. Indeed, the presence of GRIM-19 augmented Fas-mediated apoptosis in the S3C-expressing cells (see Supplementary Fig.…”