Interaction Of DJ-1 Research Articles

A Complex Interplay of DJ-1, LRRK2, and Nrf2 in the Regulation of Mitochondrial Function in Cypermethrin-Induced Parkinsonism.

Cypermethrin impairs mitochondrial function, induces redox imbalance, and leads to Parkinsonism in experimental animals. Knockdown of deglycase-1 (DJ-1) gene, which encodes a redox-sensitive antioxidant protein, aggravates cypermethrin-mediated α-synuclein overexpression and oxidative alteration of proteins. DJ-1 is also reported to be essential for maintaining stability of nuclear factor erythroid 2-related factor 2 (Nrf2), shielding cells against oxidative insult. Leucine-rich repeat kinase 2 (LRRK2), another protein associated with Parkinson's disease, is also involved in regulating mitochondrial function. However, underlying molecular mechanisms remain elusive. The study intended to explore an interaction of DJ-1, LRRK2, and Nrf2 in the regulation of mitochondrial function in cypermethrin-induced Parkinsonism. Small interfering RNA-mediated knockdown of DJ-1 and LRRK2 gene and pharmacological activation of Nrf2 were performed in rats and/or human neuroblastoma cells with or without cypermethrin. Indexes of oxidative stress, mitochondrial impairment, and Parkinsonism along with α-synuclein expression, post-translational modification, and aggregation were measured. DJ-1 gene knockdown exacerbated cypermethrin-induced increase in oxidative stress and intrinsic apoptosis and reduction in expression of mitochondrial antioxidant proteins via inhibiting nuclear translocation of Nrf2. Additionally, cypermethrin-induced oxidative stress, mitochondrial impairment, and α-synuclein expression and aggregation were found to be suppressed by LRRK2 gene knockdown, by promoting Nrf2 nuclear translocation and expression of mitochondrial antioxidant proteins. Furthermore, Nrf2 activator, sulforaphane, ameliorated cypermethrin-induced mitochondrial impairment and oxidative stress and provided protection against dopaminergic neuronal death. The findings indicate that DJ-1 and LRRK2 independently alter Nrf2-mediated changes and a complex interplay among DJ-1, LRRK2, and Nrf2 exists in the regulation of mitochondrial function in cypermethrin-induced Parkinsonism.

Anti-Aggregative Effect of the Antioxidant DJ-1 on the TPPP/p25-Derived Pathological Associations of Alpha-Synuclein.

DJ-1, a multi-functional protein with antioxidant properties, protects dopaminergic neurons against Parkinson’s disease (PD). The oligomerization/assembly of alpha-synuclein (SYN), promoted by Tubulin Polymerization Promoting Protein (TPPP/p25), is fatal in the early stage of PD. The pathological assembly of SYN with TPPP/p25 inhibits their proteolytic degradation. In this work, we identified DJ-1 as a new interactive partner of TPPP/p25, and revealed its influence on the association of TPPP/p25 with SYN. DJ-1 did not affect the TPPP/p25-derived tubulin polymerization; however, it did impede the toxic assembly of TPPP/p25 with SYN. The interaction of DJ-1 with TPPP/p25 was visualized in living human cells by fluorescence confocal microscopy coupled with Bifunctional Fluorescence Complementation (BiFC). While the transfected DJ-1 displayed homogeneous intracellular distribution, the TPPP/p25-DJ-1 complex was aligned along the microtubule network. The anti-aggregative effect of DJ-1 on the pathological TPPP/p25-SYN assemblies was established by the decrease in the intensity of their intracellular fluorescence (BiFC signal) and the increase in the proteolytic degradation of SYN complexed with TPPP/p25 due to the DJ-1-derived disassembly of SYN with TPPP/p25. These data obtained with HeLa and SH-SY5Y cells revealed the protective effect of DJ-1 against toxic SYN assemblies, which assigns a new function to the antioxidant sensor DJ-1.

Mitochondrial Translocation of DJ-1 Is Mediated by Grp75: Implication in Cardioprotection of Resveratrol Against Hypoxia/Reoxygenation-Induced Oxidative Stress.

Resveratrol (Res) was recently reported to ameliorate hypoxia/reoxygenation (H/R)-caused oxidative stress in H9c2 cardiomyocytes through promoting the mitochondrial translocation of DJ-1 protein and subsequently preserving the activity of mitochondrial complex I. However, it is noteworthy that DJ-1 possesses no mitochondria-targeting sequence. Therefore, how Res induces DJ-1 mitochondrial translocation is an important and interesting question for further exploration. Glucose-regulated protein 75 (Grp75), whose N-terminus contains a 51-amino acid long mitochondrial-targeting signal peptide, is a cytoprotective chaperone that partakes in mitochondrial import of several proteins. Here, the contribution of Grp75 to mitochondrial import of DJ-1 by Res was investigated in a cellular model of H/R. Our results showed that Res upregulated the expression of DJ-1 protein, enhanced the interaction of DJ-1 and Grp75, and promoted DJ-1 translocation to mitochondria from cytosol in H9c2 cardiomyocytes undergoing H/R. Importantly, knockdown of Grp75 markedly reduced the interaction of DJ-1 with Grp75 and subsequent DJ-1 mitochondrial translocation induced by Res. Furthermore, Res pretreatment promoted the association of DJ-1 with ND1 and NDUFA4 subunits of complex I, preserved the activity of complex I, decreased mitochondria-derived reactive oxygen species production, and eventually ameliorated H/R-caused oxidative stress damage. Intriguingly, these effects were largely prevented also by small interfering RNA targeting Grp75. Overall, these results suggested that Grp75 interacts with DJ-1 to facilitate its translocation from cytosol to mitochondria, which is required for Res-mediated preservation of mitochondria complex I and cardioprotection from H/R-caused oxidative stress injury.

Resveratrol attenuates myocardial hypoxia/reoxygenation-induced cell apoptosis through DJ-1-mediated SIRT1-p53 pathway

Resveratrol, a multi-functional phytoalexin, has been well indicated to exert cardioprotective effects by weakening ischemia/reperfusion (I/R) injury, and cell apoptosis is a vital way in I/R injury. SIRT1-p53 pathway has strong significance in regulating cell apoptosis. DJ-1 can directly bind to SIRT1 and stimulate the activity of SIRT1-p53. Therefore, the current study was determined whether Resveratrol attenuates hypoxia/reoxygenation (H/R)-induced cell apoptosis, and whether DJ-1-mediated SIRT1 activation involves in the cardioprotective effects of Resveratrol. The results showed that remarkable decrease in the number of apoptotic cells along with reduction of lactate dehydrogenase release and restoration of cell viability emerged when Resveratrol was applied in the H9c2 cells exposed to H/R. Moreover, Resveratrol increased DJ-1 expression and promoted the interaction of DJ-1 with SIRT1, which further contributed to subsequent restoration of SIRT1 activity and decrease of acetylation level of p53. However, above cardioprotective effects of Resveratrol were abrogated by DJ-1 siRNA and SIRT1 specific inhibitor Sirtinol. In conclusion, the current study demonstrated that Resveratrol suppressed H/R-induced cell apoptosis, which may be conducted by up-regulating DJ-1, and later activating SIRT1 activity and subsequently inhibiting p53 acetylation level in the H9c2 cells.

Interaction of DJ-1 with Lyn is essential for IgE-mediated stimulation of human mast cells

DJ-1 is a redox-sensitive protein with multiple roles in cell homeostasis, levels of which are altered in patients with mast cell (MC)-related disorders. However, whether DJ-1 can regulate human MC function is unknown. We sought to investigate the potential role of DJ-1 in the responses of human MCs to antigen stimulation. DJ-1 was silenced in human CD34+-derived MCs and in the LAD2 MC line by using lentiviral short hairpin RNA constructs. Release of β-hexosaminidase, prostaglandin D2, and GM-CSF and changes in reactive oxygen species levels were measured after FcεRI engagement. Enzymatic assays, sucrose density gradient centrifugation, immunoprecipitation, dot and Western blotting, and confocal imaging were performed for signaling, cellular localization, and coassociation studies. DJ-1 knockdown substantially reduced mediator release, as well as Lyn kinase and spleen tyrosine kinase activation and signaling through mechanisms that appeared largely unrelated to DJ-1 antioxidant activity. Following FcεRI activation, nonoxidized rather than oxidized DJ-1 translocated to lipid rafts, where it associated with Lyn, an interaction that appeared critical for maximal Lyn activation and initiation of signaling. Using purified recombinant proteins, we demonstrated that DJ-1 directly bound to Lyn but not to other Src kinases, and this interaction was specific for human but not mouse proteins. In addition, DJ-1 reduced Src homology 2 domain-containing phosphatase 2 phosphatase activity by scavenging reactive oxygen species, thus preventing spleen tyrosine kinase dephosphorylation and perpetuating MC signaling. We demonstrate a novel role for DJ-1 in the early activation of Lyn by FcεRI, which is essential for human MC responses and provides the basis for an alternative target in allergic disease therapy.

Oxidation and interaction of DJ-1 with 20S proteasome in the erythrocytes of early stage Parkinson's disease patients.

Parkinson’s disease (PD) is a progressive, age-related, neurodegenerative disorder, and oxidative stress is an important mediator in its pathogenesis. DJ-1, the product of the causative gene of a familial form of PD, plays a significant role in anti-oxidative defence to protect cells from oxidative stress. DJ-1 undergoes preferential oxidation at the cysteine residue at position 106 (Cys-106) under oxidative stress. Here, using specific antibodies against Cys-106-oxidized DJ-1 (oxDJ-1), it was found that the levels of oxDJ-1 in the erythrocytes of unmedicated PD patients (n = 88) were higher than in those of medicated PD patients (n = 62) and healthy control subjects (n = 33). Elevated oxDJ-1 levels were also observed in a non-human primate PD model. Biochemical analysis of oxDJ-1 in erythrocyte lysates showed that oxDJ-1 formed dimer and polymer forms, and that the latter interacts with 20S proteasome. These results clearly indicate a biochemical alteration in the blood of PD patients, which could be utilized as an early diagnosis marker for PD.

Abstract 19837: DJ-1/Park7 Protects the Heart Against Ischemia-reperfusion Injury Through the Modulation of SUMOylation (Best of Basic Science Abstract)

Background: DJ-1/Park7 is a ubiquitously expressed protein typically associated with the development of early onset Parkinson’s disease. Recent data suggests that it also plays a role in the cellular response to stress. Although much is known about DJ-1 in the brain, very little has been investigated in the heart. Here, we aimed to examine the underlying molecular mechanisms mediating the actions of DJ-1 in the heart following the onset of myocardial ischemia-reperfusion (I/R) injury. Methods and Results: Wild-type (WT) control and DJ-1 deficient (DJ-1 KO) mice were subjected to in vivo myocardial I/R injury. DJ-1 KO mice (n=9) displayed increased areas of infarction (%INF/LV or AAR: 30.2 vs 22.0%, 53.6 vs 39.0%, Troponin-I: 47.4 vs 19.9ng/ml, p<0.05 respectively) and worsened left ventricular function (LVEF: 43.7 vs 58.1%, p<0.001) when compared to WT mice (n=9), confirming a protective role for DJ-1 in the heart. In an effort to evaluate the potential mechanism(s) responsible for the increased injury in DJ-1 KO mice, we focused on SUMOylation, a post-translational modification process which regulates various aspects of protein function, including transcription, subcellular localization, DNA repair, and cell cycle. DJ-1 KO hearts after I/R injury were found to display enhanced accumulation of SUMO-1 modified proteins, (this modification is generally associated with cell injury), and reduced SUMO-2/3 modified proteins (this modification is generally associated with cytoprotection). Further analysis, revealed that the protein expression of the de-SUMOylation enzyme SENP-1 (removes SUMO-1 modifications) was reduced, whereas the expression of SENP-5 (removes SUMO-2/3 modifications) was enhanced in DJ-1 KO hearts after I/R injury. Changes in mRNA levels did not account for the altered protein expression of SENP-1 and SENP-5. So, we evaluated the direct interaction of DJ-1 with both proteins in hearts of WT mice following I/R using co-immunoprecipitation. We found that SENP1 binding with DJ-1 was down-regulated, whereas SENP5 binding with DJ-1 was up-regulated. Conclusion: Our data demonstrated that the activation of DJ-1 in response to myocardial I/R injury protects the heart by the modulation of SUMOylation via direct binding of SENP1 and SENP5.

DJ-1 interacts with RACK1 and protects neurons from oxidative-stress-induced apoptosis.

PD (Parkinson's disease) is a complex disorder that is associated with neuronal loss or dysfunction caused by genetic risks, environmental factors and advanced aging. It has been reported that DJ-1 mutations rendered neurons sensitive to oxidative damage, which led to the onset of familiar PD. However, the molecular mechanism is still unclear. In the present study we show that DJ-1 interacts with RACK1 (receptor of activated C kinase 1) and increases its dimerization and protein stability. The DJ-1 transgene protects cortical neurons from H2O2-induced apoptosis, and this protective effect is abrogated by knocking down RACK1. Similarly, deletion of DJ-1 in cortical neurons increases the sensitivity to H2O2, and the damage can be significantly rescued by DJ-1 or DJ-1/RACK1 co-transfection, but not by RACK1 alone. We observed further that the interaction of DJ-1 and RACK1 is disrupted by H2O2 or MPP+ (1-methyl-4-phenylpyridinium) treatment, and the protein levels of DJ-1 and RACK1 decreased in neurodegenerative disease models. Taken together, the DJ-1-RACK1 complex protects neurons from oxidative stress-induced apoptosis, with the implication that DJ-1 and RACK1 might be novel targets in the treatment of neurodegenerative diseases.

Transcriptional Activation of the Cholecystokinin Gene by DJ-1 through Interaction of DJ-1 with RREB1 and the Effect of DJ-1 on the Cholecystokinin Level in Mice

DJ-1 is an oncogene and also causative gene for familial Parkinson’s disease. DJ-1 has multiple functions, including transcriptional regulation. DJ-1 acts as a coactivator that binds to various transcription factors, resulting in stimulation or repression of the expression of their target genes. In this study, we found that the cholecystokinin (CCK) gene is a transcriptional target gene for DJ-1. CCK is a peptide hormone and plays roles in contraction of the gallbladder and in promotion of secretion of pancreatic fluid. CCK is co-localized with dopamine in the substantia nigra to regulate release of dopamine. Reduced expression of CCK mRNA was observed in DJ-1-knockdown cells. The Ras-responsive element (RRE) and Sp1 site were essential for promoter activity, and DJ-1 stimulated promoter activity by binding to RRE-binding protein 1 (RREBP1). The complex of DJ-1 with RREB1 but not with Sp1 bound to the RRE. Furthermore, the reduced CCK level in the serum from DJ-1-knockout mice compared to that from wild-type mice was observed. This is the first report showing that DJ-1 participates in peptide hormone synthesis.

Structure of Cu(I)-Bound DJ-1 Reveals a Biscysteinate Metal Binding Site at the Homodimer Interface: Insights into Mutational Inactivation of DJ-1 in Parkinsonism

The Parkinsonism-associated protein DJ-1 has been suggested to activate the Cu-Zn superoxide dismutase (SOD1) by providing its copper cofactor. The structural and chemical means by which DJ-1 could support this function is unknown. In this study, we characterize the molecular interaction of DJ-1 with Cu(I). Mass spectrometric analysis indicates binding of one Cu(I) ion per DJ-1 homodimer. The crystal structure of DJ-1 bound to Cu(I) confirms metal coordination through a docking accessible biscysteinate site formed by juxtaposed cysteine residues at the homodimer interface. Spectroscopy in crystallo validates the identity and oxidation state of the bound metal. The measured subfemtomolar dissociation constant (Kd = 6.41 × 10(-16) M) of DJ-1 for Cu(I) supports the physiological retention of the metal ion. Our results highlight the requirement of a stable homodimer for copper binding by DJ-1. Parkinsonism-linked mutations that weaken homodimer interactions will compromise this capability.

Hyperglycemia-Induced Inhibition of DJ-1 Expression Compromised the Effectiveness of Ischemic Postconditioning Cardioprotection in Rats

Ischemia postconditioning (IpostC) is an effective way to alleviate ischemia and reperfusion injury; however, the protective effects seem to be impaired in candidates with diabetes mellitus. To gain deep insight into this phenomenon, we explored the role of DJ-1, a novel oncogene, that may exhibit powerful antioxidant capacity in postconditioning cardioprotection in a rat model of myocardial ischemia reperfusion injury. Compared with normal group, cardiac DJ-1 was downregulated in diabetes. Larger postischemic infarct size as well as exaggeration of oxidative stress was observed, while IpostC reversed the above changes in normal but not in diabetic rats. DJ-1 was increased after ischemia and postconditioning contributed to a further elevation; however, no alteration of DJ-1 was documented in all subgroups of diabetic rats. Alteration of the cardioprotective PI3K/Akt signaling proteins may be responsible for the ineffectiveness of postconditioning in diabetes. There is a positive correlation relationship between p-Akt and DJ-1 but a negative correlation between infarct size and DJ-1, which may partially explain the interaction of DJ-1 and IpostC cardioprotection. Our result indicates a beneficial role of DJ-1 in myocardial ischemia reperfusion. Downregulation of cardiac DJ-1 may be responsible for the compromised diabetic heart responsiveness to IpostC cardioprotection.

Oxidation of DJ-1-dependent cell transformation through direct binding of DJ-1 to PTEN

DJ-1 is an oncogene and also a causative gene for a familial form of Parkinson's disease. DJ-1 has multiple functions, including anti-oxidative stress reaction and cysteine 106 (C106) of DJ-1 is an essential amino acid for DJ-1 to exert its function. While increased expression and secretion of DJ-1 into serum in patients with various cancers and regulation of p53 and PTEN by DJ-1 have been reported, the molecular mechanism underlying oncogenicity of DJ-1 is poorly understood. Here, we analyzed the function of DJ-1 in the PI3'K signaling pathway under an oxidative stress condition, focusing on the interaction of DJ-1 with PTEN. We found that both wild-type (wt) and C106S-DJ-1, a substitution mutant of DJ-1, directly bound to PTEN and inhibited PTEN phosphatase activity but that C106S-DJ-1 more strongly inhibited the activity than did wt-DJ-1. When NIH3T3 cells were treated with H2O2, oxidation of C106 of wt-DJ-1 occurred, accompanied by increased binding of wt-DJ-1 to PTEN, decreased PTEN activity and increased phosphorylation of AKT. C106S-DJ-1 transformed cells more strongly than did wt-DJ-1 and the transforming activity of DJ-1 was enhanced by H2O2 treatment of cells in which increased binding of DJ-1 to PTEN and decreased PTEN activity were observed. Furthermore, TOF-MS analysis of the oxidative status of C106 suggested that DJ-1 activity requires the presence of the reduced form of C106, which accounts for >50% of the total form. These results suggest that the oxidative status of DJ-1 regulates PTEN activity, leading to cell proliferation and transformation.

Oxidizable Residues Mediating Protein Stability and Cytoprotective Interaction of DJ-1 with Apoptosis Signal-regulating Kinase 1

Parkinson disease (PD)-associated genomic deletions and the destabilizing L166P point mutation lead to loss of the cytoprotective DJ-1 protein. The effects of other PD-associated point mutations are less clear. Here we demonstrate that the M26I mutation reduces DJ-1 expression, particularly in a null background (knockout mouse embryonic fibroblasts). Thus, homozygous M26I mutation causes loss of DJ-1 protein. To determine the cellular consequences, we measured suppression of apoptosis signal-regulating kinase 1 (ASK1) and cytotoxicity for [M26I]DJ-1, and systematically all other DJ-1 methionine and cysteine mutants. C106A mutation of the central redox site specifically abolished binding to ASK1 and the cytoprotective activity of DJ-1. DJ-1 was apparently recruited into the ASK1 signalosome via Cys-106-linked mixed disulfides. The designed higher order oxidation mimicking [C106DD]DJ-1 non-covalently bound to ASK1 even in the absence of hydrogen peroxide and conferred partial cytoprotection. Interestingly, mutations of peripheral redox sites (C46A and C53A) and M26I also led to constitutive ASK1 binding. Cytoprotective [wt]DJ-1 bound to the ASK1 N terminus (which is known to bind another negative regulator, thioredoxin 1), whereas [M26I]DJ-1 bound to aberrant C-terminal site(s). Consequently, the peripheral cysteine mutants retained cytoprotective activity, whereas the PD-associated mutant [M26I]DJ-1 failed to suppress ASK1 activity and nuclear export of the death domain-associated protein Daxx and did not promote cytoprotection. Thus, cytoprotective binding of DJ-1 to ASK1 depends on the central redox-sensitive Cys-106 and may be modulated by peripheral cysteine residues. We suggest that impairments in oxidative conformation changes of DJ-1 might contribute to PD neurodegeneration.

Post-transcriptional regulation of mRNA associated with DJ-1 in sporadic Parkinson disease

Mutations in DJ-1 lead to a monogenic form of early onset recessive parkinsonism. DJ-1 can respond to oxidative stress, which has been proposed to be involved in the pathogenesis of sporadic Parkinson disease (PD). We have recently reported that DJ-1 interacts with mRNA in an oxidation-dependent manner. Here, we confirm interaction of DJ-1 and RNA in human brain using immunoprecipitation followed by quantitative real time PCR. We confirmed previous reports that DJ-1 is more oxidized in cortex from cases of sporadic PD compared to controls. In the same samples, protein and RNA expression was measured for four DJ-1 target genes GPx4, MAPK8IP1, ND2 and ND5. While no alterations in mRNA expression were observed, an increase in protein expression was observed in PD cases for GPx4 and MAPK8IP1. In the same patients, we saw decreased mRNA and protein levels of two mitochondrial targets, ND2 and ND5. These results suggest that these proteins undergo regulation at the post-transcriptional level that may involve translational regulation by DJ-1.

Inhibition of PTEN phosphatase activity by the direct interaction of DJ-1 with PTEN under the oxidative conditions

Inhibition of PTEN phosphatase activity by the direct interaction of DJ-1 with PTEN under the oxidative conditions

DJ-1 Decreases Bax Expression through Repressing p53 Transcriptional Activity

DJ-1, originally identified as an oncogene product, is a protein with various functions in cellular transformation, oxidative stress response, and transcriptional regulation. Although previous studies suggest that DJ-1 is cytoprotective, the mechanism by which DJ-1 exerts its survival functions remains largely unknown. Here we show that DJ-1 exerts its cytoprotection through inhibiting p53-Bax-caspase pathway. DJ-1 interacts with p53 in vitro and in vivo. Overexpression of DJ-1 decreases the expression of Bax and inhibits caspase activation, whereas knockdown of DJ-1 increases Bax protein levels and accelerates caspase-3 activation and cell death induced by UV exposure. Our data provide evidence that the protective effects of DJ-1 on apoptosis are associated with its ability of decreasing Bax level through inhibiting p53 transcriptional activity.

DJ-1: A New Comer in Parkinsons Disease Pathology

Parkinson's disease (PD) is a movement disorder of high prevalence in the elderly. It is characterized by a loss of dopaminergic neurons and the presence of intracytoplasmic inclusions named Lewy bodies. To date six familial PD-associated proteins have been identified so far. Some of them are implicated in the development of either autosomal dominant (alpha-synuclein and LRRK2 (leucine-rich repeat kinase 2/dardarin) or early-onset recessive (parkin, DJ-1, PINK1 (PTEN-induced kinase-1) and ATP13A2) PD forms. A number of genetic studies have shown that 50% of the recessive forms are linked to mutations on parkin gene, followed by PINK1 (8-15%) and DJ-1 (1%). The purpose of this review is to provide an overview of the emerging data on the cellular and molecular biology of DJ-1. DJ-1 is a ubiquitous protein that was first described as an oncogene. Nevertheless, after its association to monogenic PD a number considerable data aiming at understanding its implication in the physiopathology of PD was produced. This review will describe the main advances concerning the function of DJ-1. A considerable progress that was only possible due to a better understanding of DJ-1 structure, genetics, distribution and development of in vivo models. All these points along with the description of recent data showing the interaction of DJ-1 with other PD-associated proteins will be given.

Interaction of DJ-1 with Daxx inhibits apoptosis signal-regulating kinase 1 activity and cell death

Investigations into the cellular and molecular biology of genes that cause inherited forms of Parkinson's disease, as well as the downstream pathways that they trigger, shed considerable light on our understanding the fundamental determinants of life and death in dopaminergic neurons. Homozygous deletion or missense mutation in DJ-1 results in autosomal recessively inherited Parkinson's disease, suggesting that wild-type DJ-1 has a favorable role in maintaining these neurons. Here, we show that DJ-1 protects against oxidative stress-induced cell death, but that its relatively modest ability to quench reactive oxygen species is insufficient to account for its more robust cytoprotective effect. To elucidate the mechanism of this cell-preserving function, we have screened out the death protein Daxx as a DJ-1-interacting partner. We demonstrate that wild-type DJ-1 sequesters Daxx in the nucleus, prevents it from gaining access to the cytoplasm, from binding to and activating its effector kinase apoptosis signal-regulating kinase 1, and therefore, from triggering the ensuing death pathway. All these steps are impaired by the disease-causing L166P mutant isoform of DJ-1. These findings suggest that the regulated sequestration of Daxx in the nucleus and keeping apoptosis signal-regulating kinase 1 activation in check is a critical mechanism by which DJ-1 exerts its cytoprotective function.