Poly(ADP-ribose) Polymerase-1 Signaling to Mitochondria in Necrotic Cell Death Requires RIP1/TRAF2-mediated JNK1 Activation

Abstract

Poly(ADP-ribose) polymerase-1 (PARP-1) hyperactivation-induced necrosis has been implicated in several pathophysiological conditions. Although mitochondrial dysfunction and apoptosis-inducing factor translocation from the mitochondria to the nucleus have been suggested to play very important roles in PARP-1-mediated cell death, the signaling events downstream of PARP-1 activation in initiating mitochondria dysfunction are not clear. Here we used the DNA alkylating agent N-methyl-N-nitro-N-nitrosoguanidine, a potent PARP-1 activator, to study PARP-1 activation-mediated cell death. We found, based on genetic knockouts and pharmacological inhibition, that c-Jun N-terminal kinase (JNK), especially JNK1, but not the other groups of mitogen-activated protein kinase, is required for PARP-1-induced mitochondrial dysfunction, apoptosis-inducing factor translocation, and subsequent cell death. We reveal that receptor-interacting protein 1 (RIP1) and tumor necrosis factor receptor-associated factor 2 (TRAF2), are upstream of JNK in PARP-1 hyperactivated cells, because PARP-1-induced JNK activation was attenuated in RIP1؊/؊ and TRAF2؊/؊ mouse embryonic fibroblast cells. Consistently, knockouts of RIP1 and TRAF2 caused a resistance to PARP-1-induced cell death. Therefore, our study uncovers that RIP1, TRAF2, and JNK comprise a pathway to mediate the signaling from PARP-1 overactivation to mitochondrial dysfunction.Poly(ADP-ribose) polymerase-1 (PARP-1) 2 is a nuclear enzyme activated by DNA strand breaks that catalyzes the covalent attachment of long branched chains of poly(ADP-ribose) with NAD ϩ as its substrate to a variety of nuclear DNA-binding proteins, including PARP-1 itself (1). PARP-1 activation plays an essential role in DNA repair under moderate stress (2); however, in several pathological situations that involve massive DNA damage, extensive activation of PARP-1 depletes cellular NAD ϩ and its precursor ATP, leading to irreversible cellular energy failure and necrotic cell death (3-5). The pathophysiological importance of PARP-1-mediated cell death has been suggested by the observation that genetic ablation of PARP-1 and pharmacological inhibition of PARP-1 activity elicit strong protection in several disease models, including ischemia-reperfusion injury after cerebral ischemia and myocardial infarction, inflammatory injury, reactive oxygen species-induced injury, and glutamate excitotoxicity (6 -10). Apoptosis and necrosis are two major forms of cell death with distinct morphological features. Apoptosis is an ordered and regulated process in which the cell actively destroys itself while maintaining plasma membrane integrity, thus permitting non-inflammatory phagocytosis of the dying cell. Necrosis, on the other hand, has traditionally been regarded as a passive and unregulated form of cell death with morphology of cell swelling, loss of plasma membrane integrity, and the release of cellular contents into the extracellular environment, thus triggering an inflammatory response (11). PARP-1-mediated cell death is c...

Poly(ADP-ribose) polymerase-1 protects neurons against apoptosis induced by oxidative stress

“…This sequence of events clearly differs from the more dramatic situation in which excessive PARP-1 activation leads to energy depletion and cell death via a mechanism that is caspase-independent 25 but may involve translocation from the mitochondria to the nucleus of the AIF. 25,27 In our experiments, GCL deficiency did not alter the subcellular localization of AIF, which remained within the perinuclear area, consistent with mitochondrial localization of this transcription factor. 28 This situation may account for the results obtained with PARP-1 inhibitors in the severe model of cerebral infarction in the rat.…”

“…25,26 Furthermore, the expression of PARP-1 at nontoxic concentrations (0.3 mg/10 3 cells) partially prevented GCL RNAi-mediated apoptotic death (Figure 5j). Finally, we investigated whether translocation of apoptosis-inducing factor (AIF) from mitochondria to the nucleus -a typical marker of PARP-1-mediated apoptosis under certain circumstances 25,27,28 -would occur in the GCL RNAi mild oxidative stress model. Immunofluorescence experiments (Figure 6a) revealed that AIF remained in the cytoplasm, preferentially within the perinuclear area, during GCL knockdown (see GFP þ neurons in Figure 6a).…”

A systems level strategy for analyzing the cell death network: implication in exploring the apoptosis/autophagy connection

“…Consistent with this phenotype, molecular analysis indicated that etoposide induced PAR ribosylation of proteins and the release of HMGB1 from the cells into the culture media (Figures 3b and c), two previously characterized hallmarks of programmed necrosis. 4,[18][19][20] In addition, the canonical apoptotic markers developed in response to the drug, including activation of the upstream initiator caspases2 and 9, and of the executioner caspases3 and 7 and the cleavage of their two substrates, PARP-1 and ICAD (Figure 3b and d). Also, fragmented nuclei and the release of cytochrome c from mitochondria to the cytosol were frequently detected (Supplementary Figure S5).…”

TRAIL induces necroptosis involving RIPK1/RIPK3-dependent PARP-1 activation

“…Interestingly, Nec-1 and knockdown of RIPK1 or RIPK3 revealed that TRAIL-induced PARP-1 activation at acidic pHe was dependent on both RIPK1 and RIPK3, suggesting that these two kinases most likely act upstream of PARP-1 and ATP depletion during necroptosis. Until now, RIPK1 activation leading to mitochondrial dysfunction has been shown to occur downstream of PARP-1 activation in DNA alkylating agent-induced necrosis, 34 Figure 7 PARP-1 is activated in Con A-induced hepatitis. WT and CD1d KO C57Bl/6 mice were treated as in Figure 6.…”