Introduction/Overview.

The DJ-1 gene is an oncogene and also causative gene for a familial form of Parkinson disease. Although exits of cancer and neurodegenerative diseases, including Parkinson disease, are completely opposite, there are some common points of view between both diseases, including growth and death signaling pathways, and oxidative stresses affect the onset and pathogenesis of both cancer and neurodegenerative diseases. DJ-1 has versatile functions and plays a role in protection against oxidative stress. Inactivation and/or excess activation of DJ-1 functions, therefore, leads to onsets of oxidative stress-related diseases such as type 2 diabetes and male infertility in addition to cancer and neurodegenerative diseases, and studies about DJ-1 will give rise to the common mechanism among these diseases. Furthermore, secreted DJ-1 levels in serum and DJ-1-binding compounds will be a diagnostic biomarker and therapeutic drug for neurodegenerative diseases, respectively.

Transcriptional Regulation of DJ-1.

DJ-1 is an oncogene and also a causative gene for familial Parkinson's disease. DJ-1 has various functions, and the oxidative status of a cysteine residue at position 106 (C106) is crucial for determination of the activation level of DJ-1.DJ-1 binds to many proteins, including various transcription factors, and acts as a coactivator or corepressor for regulating their target genes without direct binding to DNA, thereby affecting various cell functions. DJ-1-regulating transcription factors and their modified proteins are the androgen receptor and its regulatory proteins, p53; polypyrimidine tract-binding protein-associated splicing factor (PSF); Keap1, an inhibitor for nuclear factor erythroid2-related factor 2 (Nrf2); sterol regulatory element-binding protein (SREBP); Ras-responsive element-binding protein (RREB1); signal transducer and activator of transcription 1 (STAT1); and Nurr1. Considering oxidative stress response and dopamine synthesis, the regulation of Nrf2, p53, and PSF by DJ-1 is especially important. In addition, SREBP1 and RREB1 functions that are positively regulated by DJ-1 may participate in the onset and pathogenesis of metabolic syndrome.DJ-1 is expressed ubiquitously with high levels in the testis and brain and moderate levels in other tissues. Furthermore, DJ-1 is translocated from the cytoplasm to nucleus during the cell cycle after mitogen stimulation, suggesting that DJ-1 has a growth-related function. In this review, we describe how DJ-1 regulates cell growth/death and dopamine synthesis by targeting various transcription factors.

Epidermal Growth Factor-dependent Activation of the Extracellular Signal-regulated Kinase Pathway by DJ-1 Protein through Its Direct Binding to c-Raf Protein.

DJ-1 is an oncogene and also a causative gene for familial Parkinson disease. DJ-1 has various functions, and the oxidative status of cysteine at position 106 (Cys-106) is crucial for determination of the activation level of DJ-1. Although DJ-1 requires activated Ras for its oncogenic activity and although it activates the extracellular signal-regulated kinase (ERK) pathway, a cell growth pathway downstream of Ras, the precise mechanism underlying activation of the ERK pathway by DJ-1 is still not known. In this study, we found that DJ-1 directly bound to the kinase domain of c-Raf but not to Ras and that Cys-106 mutant DJ-1 bound to c-Raf more weakly than did wild-type DJ-1. Co-localization of DJ-1 with c-Raf in the cytoplasm was enhanced in epidermal growth factor (EGF)-treated cells. Knockdown of DJ-1 expression attenuated the phosphorylation level of c-Raf in EGF-treated cells, resulting in reduced activation of MEK and ERK1/2. Although EGF-treated DJ-1 knock-out cells also showed attenuated c-Raf activation, reintroduction of wild-type DJ-1, but not C106S DJ-1, into DJ-1 knock-out cells restored c-Raf activation in a DJ-1 binding activity in a c-Raf-dependent manner. DJ-1 was not responsible for activation of c-Raf in phorbol myristate acetate-treated cells. Furthermore, DJ-1 stimulated self-phosphorylation activity of c-Raf in vitro, but DJ-1 was not a target for Raf kinase. Oxidation of Cys-106 in DJ-1 was not affected by EGF treatment. These findings showed that DJ-1 is a positive regulator of the EGF/Ras/ERK pathway through targeting c-Raf.

DJ-1 activates SIRT1 through its direct binding to SIRT1.

The DJ-1 gene is a ras-dependent oncogene and also a causative gene for a familial form of Parkinson's disease park7. DJ-1 is a multi-functional protein and plays roles in regulation of cell growth, cells death, metabolism and mitochondrial homeostasis against oxidative stress. To explore various functions, DJ-1 associates with a number of proteins localized in the nucleus, cytoplasm and mitochondria. The oxidative status of a cysteine residue at an amino acid number 106 (C106) of DJ-1 determines the active level of DJ-1. Precise molecular mechanism of exploration of DJ-1 function is, however, not resolved. In this study, we identified Sirtuin family proteins (SIRT1, 2, and 4-6) as DJ-1-binding proteins, and DJ-1 associated with SIRT1 in cells. Sirtuins like DJ-1 also regulates growth, death and metabolism of cells and mitochondrial homeostasis. We found that DJ-1 stimulated deacetylase activity of SIRT1 and that SIRT1-suppressed transcriptional activity of SIRT1-target p53 was further decreased by DJ-1. Furthermore, SIRT1 activity was reduced in DJ-1-knockout cells, and this reduced activity was restored by re-introduction of wild-type DJ-1 but not of C106-mutant DJ-1 into DJ-1-knockout cells. It is first report showing direct connection of DJ-1 with SIRT1.

High levels of DJ-1 protein and isoelectric point 6.3 isoform in sera of breast cancer patients.

In patients with cancer and Parkinson's disease, the DJ-1 protein may be secreted into the serum during the impaired response of the underlying cell-protective mechanisms. In order to determine the clinical significance of DJ-1 protein in the sera of breast cancer patients, we examined blood samples from a breast cancer group (n = 180) and a non-cancerous control group (n = 300). Higher levels of DJ-1 were detected in the breast cancer group (mean level, 42.7 ng/mL) than the control group (28.3 ng/mL) by ELISA (P = 0.019). Higher DJ-1 levels were significantly associated with advanced clinical grade, according to the TNM classification, negative hormone receptor status, and high Ki-67 labeling index, of biopsied materials; samples showed low DJ-1 protein expression despite upregulated DJ-1 mRNA. DJ-1 isoforms could be detected clearly in 17 blood samples (from 11 breast cancer patients, and 6 non-cancerous controls) by 2-D gel electrophoresis and immunoblot analysis. The isoform at the pI of 6.3 showed the highest intensity in all 11 cancer cases. Conversely, in the 6 non-cancerous cases, isoforms other than the pI 6.3 isoform were highly expressed, and there was a significant difference in the isoform pattern between breast cancer cases and controls (P = 0.00025). These data indicate that high levels of DJ-1, probably of isoform at pI 6.3, is a candidate serum marker of breast cancer.

DJ-1-dependent protective activity of DJ-1-binding compound no. 23 against neuronal cell death in MPTP-treated mouse model of Parkinson's disease.

Parkinson's disease (PD) is caused by dopaminergic cell death in the substantia nigra, leading to a reduced level of dopamine in the striatum. Oxidative stress is one of the causes of PD. Since symptomatic PD therapies are used, identification of compounds or proteins that inhibit oxidative stress-induced neuronal cell death is necessary. DJ-1 is a causative gene product of familial PD and plays a role in anti-oxidative stress reaction. We have identified various DJ-1-binding compounds, including compound-23, that restored neuronal cell death and locomotion defects observed in neurotoxin-induced PD models. In this study, wild-type and DJ-1-knockout mice were injected intraperitoneally with 1 mg/kg of compound-23 and then with 30 mg/kg of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at 1 h after injection. Five days after administration, the effects of compound-23 on MPTP-induced locomotion deficits, on dopaminergic cell death and on brain dopamine levels were analyzed by rotor rod tests, by staining cells with an anti-TH antibody and by an HPLC, respectively. The results showed that compound-23 inhibited MPTP-induced reduction of retention time on the rotor rod bar, neuronal cell death in the substantia nigra and striatum and dopamine content in wild-type mice but not in DJ-1-knockout mice, indicating a DJ-1-dependent effect of compound-23.

Prefoldin plays a role as a clearance factor in preventing proteasome inhibitor-induced protein aggregation.

Prefoldin is a molecular chaperone composed of six subunits, PFD1-6, and prevents misfolding of newly synthesized nascent polypeptides. Although it is predicted that prefoldin, like other chaperones, modulates protein aggregation, the precise function of prefoldin against protein aggregation under physiological conditions has never been elucidated. In this study, we first established an anti-prefoldin monoclonal antibody that recognizes the prefoldin complex but not its subunits. Using this antibody, it was found that prefoldin was localized in the cytoplasm with dots in co-localization with polyubiquitinated proteins and that the number and strength of dots were increased in cells that had been treated with lactacystin, a proteasome inhibitor, and thapsigargin, an inducer of endoplasmic reticulum stress. Knockdown of prefoldin increased the level of SDS-insoluble ubiquitinated protein and reduced cell viability in lactacystin and thapsigargin-treated cells. Opposite results were obtained in prefoldin-overexpressed cells. It has been reported that mice harboring a missense mutation L110R of MM-1α/PFD5 exhibit neurodegeneration in the cerebellum. Although the prefoldin complex containing L110R MM-1α was properly formed in vitro and in cells derived from L110R MM-1α mice, the levels of ubiquitinated proteins and cytotoxicity were higher in L110R MM-1α cells than in wild-type cells under normal conditions and were increased by lactacystin and thapsigargin treatment, and growth of L110R MM-1α cells was attenuated. Furthermore, the polyubiquitinated protein aggregation level was increased in the brains of L110R MM-1α mice. These results suggest that prefoldin plays a role in quality control against protein aggregation and that dysfunction of prefoldin is one of the causes of neurodegenerative diseases.

Prefoldin protects neuronal cells from polyglutamine toxicity by preventing aggregation formation.

Huntington disease is caused by cell death after the expansion of polyglutamine (polyQ) tracts longer than ∼40 repeats encoded by exon 1 of the huntingtin (HTT) gene. Prefoldin is a molecular chaperone composed of six subunits, PFD1-6, and prevents misfolding of newly synthesized nascent polypeptides. In this study, we found that knockdown of PFD2 and PFD5 disrupted prefoldin formation in HTT-expressing cells, resulting in accumulation of aggregates of a pathogenic form of HTT and in induction of cell death. Dead cells, however, did not contain inclusions of HTT, and analysis by a fluorescence correlation spectroscopy indicated that knockdown of PFD2 and PFD5 also increased the size of soluble oligomers of pathogenic HTT in cells. In vitro single molecule observation demonstrated that prefoldin suppressed HTT aggregation at the small oligomer (dimer to tetramer) stage. These results indicate that prefoldin inhibits elongation of large oligomers of pathogenic Htt, thereby inhibiting subsequent inclusion formation, and suggest that soluble oligomers of polyQ-expanded HTT are more toxic than are inclusion to cells.

DJ-1 cooperates with PYCR1 in cell protection against oxidative stress.

DJ-1, a product of the DJ-1/PARK7 gene, has been suggested to play various functions involved in transcriptional regulation, protease activity, anti-oxidative stress activity, and regulation of mitochondrial complex I. Such a variety of functions of DJ-1 are supposed to be realized through interactions with different partner proteins. Among the candidates for DJ-1-partner proteins detected in TOF-MAS analyses of the cellular proteins co-immunoprecipitated with DJ-1, we focused here pyrroline-5-carboxylate reductase 1, PYCR1, a final key enzyme for proline biosynthesis. DJ-1 directly bound to PYCR1 in vivo and in vitro. DJ-1 and PYCR1 colocalized in mitochondria, and both were suggested to be involved in regulation of mitochondrial membrane potential, but differently. DJ-1 enhanced the enzymatic activity of PYCR1 in vitro. The cells knocked down for DJ-1 and PYCR1 showed lower viability under oxidative stress conditions. No additive nor synergistic results were obtained for the cells that had been knocked down for both DJ-1 and PYCR1, suggesting that DJ-1 and PYCR1 are on the same pathway of anti-oxidative stress protection of the cells.

Prefoldin subunits are protected from ubiquitin-proteasome system-mediated degradation by forming complex with other constituent subunits.

The molecular chaperone prefoldin (PFD) is a complex comprised of six different subunits, PFD1-PFD6, and delivers newly synthesized unfolded proteins to cytosolic chaperonin TRiC/CCT to facilitate the folding of proteins. PFD subunits also have functions different from the function of the PFD complex. We previously identified MM-1α/PFD5 as a novel c-Myc-binding protein and found that MM-1α suppresses transformation activity of c-Myc. However, it remains unclear how cells regulate protein levels of individual subunits and what mechanisms alter the ratio of their activities between subunits and their complex. In this study, we found that knockdown of one subunit decreased protein levels of other subunits and that transfection of five subunits other than MM-1α into cells increased the level of endogenous MM-1α. We also found that treatment of cells with MG132, a proteasome inhibitor, increased the level of transfected/overexpressed MM-1α but not that of endogenous MM-1α, indicating that overexpressed MM-1α, but not endogenous MM-1α, was degraded by the ubiquitin proteasome system (UPS). Experiments using other PFD subunits showed that the UPS degraded a monomer of PFD subunits, though extents of degradation varied among subunits. Furthermore, the level of one subunit was increased after co-transfection with the respective subunit, indicating that there are specific combinations between subunits to be stabilized. These results suggest mutual regulation of protein levels among PFD subunits and show how individual subunits form the PFD complex without degradation.

Stimulation of vesicular monoamine transporter 2 activity by DJ-1 in SH-SY5Y cells.

Loss-of-functional mutation in the DJ-1 gene causes a subset of familial Parkinson's disease. The mechanism underlying DJ-1-related selective vulnerability in the dopaminergic pathway is, however, not known. Dopamine is synthesized by two enzymes and then packed into synaptic vesicles by vesicular monoamine transporter 2 (VMAT2). In this study, we found that knockdown of DJ-1 expression reduced the levels of mRNA and protein of VMAT2, resulting in reduced VMAT2 activity. Co-immunoprecipitation and pull-down experiments revealed that DJ-1 directly bound to VMAT2, and DJ-1 was co-localized with VMAT2 in cells. Furthermore, ectopic expression of wild-type DJ-1, but not that of L166P, M26I and C106S mutants of DJ-1, increased mRNA and protein levels of VMAT2 and VMAT2 activity. Since VMAT2 and a portion of DJ-1 are localized in the synaptic membrane, these results suggest that DJ-1, but not pathogenically mutated DJ-1, stimulates VMAT2 activity in the synapse by transactivation of the VMAT gene and by direct binding to VMAT2 and that cysteine 106 is necessary for the stimulating activity of DJ-1 toward VMAT2.

Human DJ-1-specific transcriptional activation of tyrosine hydroxylase gene.

Loss-of-function mutation in the DJ-1 gene causes a subset of familial Parkinson disease. The mechanism underlying DJ-1-related selective vulnerability in the dopaminergic pathway is, however, not known. DJ-1 has multiple functions, including transcriptional regulation, and one of transcriptional target genes for DJ-1 is the tyrosine hydroxylase (TH) gene, the product of which is a key enzyme for dopamine biosynthesis. It has been reported that DJ-1 is a neuroprotective transcriptional co-activator that sequesters a transcriptional co-repressor polypyrimidine tract-binding protein-associated splicing factor (PSF) from the TH gene promoter. In this study, we found that knockdown of human DJ-1 by small interference RNA in human dopaminergic cell lines attenuated TH gene expression and 4-dihydroxy-L-phenylalanine production but that knockdown or knock-out of mouse DJ-1 in mouse cell lines or in mice did not affect such expression and TH activity. In reporter assays using the human TH gene promoter linked to the luciferase gene, stimulation of TH promoter activity was observed in human cells, but not mouse cells, that had been transfected with DJ-1. Although human DJ-1 and mouse DJ-1 were associated either with human or with mouse PSF, TH promoter activity inhibited by PSF was restored by human DJ-1 but not by mouse DJ-1. Chromatin immunoprecipitation assays revealed that the complex of PSF with DJ-1 bound to the human but not the mouse TH gene promoter. These results suggest a novel species-specific transcriptional regulation of the TH promoter by DJ-1 and one of the mechanisms for no reduction of TH in DJ-1-knock-out mice.

DJ-1-Mediated protective effect of protocatechuic aldehyde against oxidative stress in SH-SY5Y cells.

DJ-1 was identified as a causal gene for a familial form of early onset Parkinson's disease (PD), park 7. DJ-1 plays roles in transcriptional regulation and the anti-oxidative stress reaction. In this study, we found that protocatechuic aldehyde (PAL), a traditional Chinese medicine compound, bound to DJ-1 in vitro and that PAL protected SH-SY5Y cells but not DJ-1-knockdown SH-SY5Y cells from oxidative stress-induced cell death, indicating that the protective effect of PAL is mediated by DJ-1. Furthermore, PAL inhibited production of reactive oxygen species and the inhibition was abated in DJ-1-knockdown cells. PAL increased and decreased phosphorylation of AKT and PTEN, respectively, in SH-SY5Y cells, suggesting that the AKT pathway is one of the specific signaling pathways in PAL-induced neuroprotection. Moreover, PAL prevented superfluous oxidation of cysteine 106 of DJ-1, an essential amino acid for DJ-1's function. The present study demonstrates that PAL has potential neuroprotective effects through DJ-1.

Oxidative status of DJ-1-dependent activation of dopamine synthesis through interaction of tyrosine hydroxylase and 4-dihydroxy-L-phenylalanine (L-DOPA) decarboxylase with DJ-1.

Parkinson disease (PD) is caused by loss of dopamine, which is synthesized from tyrosine by two enzymes, tyrosine hydroxylase (TH) and 4-dihydroxy-L-phenylalanine decarboxylase (DDC). DJ-1 is a causative gene for the familial form of PD, but little is known about the roles of DJ-1 in dopamine synthesis. In this study, we found that DJ-1 directly bound to TH and DDC and positively regulated their activities in human dopaminergic cells. Mutants of DJ-1 found in PD patients, including heterozygous mutants, lost their activity and worked as dominant-negative forms toward wild-type DJ-1. When cells were treated with H(2)O(2), 6-hydroxydopamine, or 1-methyl-4-phenylpyridinium, changes in activities of TH and DDC accompanied by oxidation of cysteine 106 of DJ-1 occurred. It was found that DJ-1 possessing Cys-106 with SH and SOH forms was active and that DJ-1 possessing Cys-106 with SO(2)H and SO(3)H forms was inactive in terms of stimulation of TH and DDC activities. These findings indicate an essential role of DJ-1 in dopamine synthesis and contribution of DJ-1 to the sporadic form of PD.

DJ-1 is indispensable for the S-nitrosylation of Parkin, which maintains function of mitochondria.

The DJ-1 gene, a causative gene for familial Parkinson's disease (PD), has been reported to have various functions, including transcriptional regulation, antioxidant response, and chaperone and protease functions; however, the molecular mechanism associated with the pathogenesis of PD remains elusive. To further explore the molecular function of DJ-1 in the pathogenesis of PD, we compared protein expression profiles in brain tissues from wild-type and DJ-1-deficient mice. Two-dimensional difference gel electrophoresis analysis and subsequent analysis using data mining methods revealed alterations in the expression of molecules associated with energy production. We demonstrated that DJ-1 deletion inhibited S-nitrosylation of endogenous Parkin as well as overexpressed Parkin in neuroblastoma cells and mouse brain tissues. Thus, we used genome editing to generate neuroblastoma cells with DJ-1 deletion or S-nitrosylated cysteine mutation in Parkin and demonstrated that these cells exhibited similar phenotypes characterized by enhancement of cell death under mitochondrial depolarization and dysfunction of mitochondria. Our data indicate that DJ-1 is required for the S-nitrosylation of Parkin, which positively affects mitochondrial function, and suggest that the denitrosylation of Parkin via DJ-1 inactivation might contribute to PD pathogenesis and act as a therapeutic target.

DJ-1-binding compound B enhances Nrf2 activity through the PI3-kinase-Akt pathway by DJ-1-dependent inactivation of PTEN.

DJ-1 was identified as an oncogene and also as a causative gene for a familial form of Parkinson disease (PD). DJ-1 plays various roles in anti-oxidative stress response. Superfluous oxidation of DJ-1 at cysteine residue 106 (C106), an inactive form of DJ-1, was observed in PD patients. DJ-1-binding compound B, which specifically bound to the C106 region of DJ-1, has been isolated and it has been shown to prevent oxidative stress-induced cell death through maintaining active forms of DJ-1 by inhibiting its superfluous oxidation. The molecular mechanism of the action of compound B, however, has not been fully elucidated. In this study, we found that compound B stimulated transcriptional activity of Nrf2 in H2O2-treated SH-SY5Y cells by inhibiting its degradation through the ubiquitin-proteasome system. Although Keap 1 is a major negative regulator of Nrf2, compound B strongly increased Nrf2 activity in Keap1-mutant A549 cells but not in PTEN-null PC3 and PTEN-knockout SH-SY5Y cells. Furthermore, treatment of cells with inhibitors of the PI3-kinase/Akt pathway inhibited the effect of compound B, and compound B increased the binding of PTEN to DJ-1 and decreased lipid phosphatase activity of PTEN concomitantly with increased oxidation of PTEN, an inactive form of PTEN. These results suggest that compound B enhances transcriptional activity of Nrf2 under an oxidative stress condition in a Keap1-independent manner and that its activity is elicited by activation of the PI3Kinase/Akt pathway with DJ-1-dependent inactivation of PTEN, leading to protection of oxidative stress-induced cell death.

DJ-1 binds to mitochondrial complex I and maintains its activity.

Parkinson's disease (PD) is caused by neuronal cell death, and oxidative stress and mitochondrial dysfunction are thought to be responsible for onset of PD. DJ-1, a causative gene product of a familial form of Parkinson's disease, PARK7, plays roles in transcriptional regulation and anti-oxidative stress. The possible mitochondrial function of DJ-1 has been proposed, but its exact function remains unclear. In this study, we found that DJ-1 directly bound to NDUFA4 and ND1, nuclear and mitochondrial DNA-encoding subunits of mitochondrial complex I, respectively, and was colocalized with complex I and that complex I activity was reduced in DJ-1-knockdown NIH3T3 and HEK293 cells. These findings suggest that DJ-1 is an integral mitochondrial protein and that DJ-1 plays a role in maintenance of mitochondrial complex I activity.

DJ-1 protects against neurodegeneration caused by focal cerebral ischemia and reperfusion in rats.

Reactive oxygen species (ROS) is massively produced in the brain after cerebral ischemia and reperfusion. It reacts strongly with cellular components, which has detrimental effects and leads to neuronal cell death. DJ-1, which was found to be the causative gene of familial Parkinson's disease PARK7, is a multifunction protein, which plays a key role in transcriptional regulation, and a molecular chaperone. In this study, we investigated the neuroprotective effect of DJ-1 against neurodegeneration caused by ischemia/reperfusion injury. Cerebral ischemia was induced in rats by 120 mins of middle cerebral artery occlusion (MCAO) using an intraluminal introduction method. The intrastriatal injection of recombinant glutathione S-transferase-tagged human DJ-1 (GST-DJ-1) markedly reduced infarct size in 2,3,5-triphenyltetrazolium chloride staining at 3 days after MCAO. In addition, we performed a noninvasive evaluation of ischemic size using magnetic resonance imaging and found a significant reduction of infarct size with the administration of GST-DJ-1. In GST-DJ-1-treated rats, behavioral dysfunction and nitrotyrosine formation were significantly inhibited. Furthermore, GST-DJ-1 markedly inhibited H(2)O(2)-mediated ROS production in SH-SY5Y cells. These results indicate that GST-DJ-1 exerts a neuroprotective effect by reducing ROS-mediated neuronal injury, suggesting that DJ-1 may be a useful therapeutic target for ischemic neurodegeneration.

DJ-1-binding compounds prevent oxidative stress-induced cell death and movement defect in Parkinson's disease model rats.

Parkinson's disease (PD) is caused by neuronal cell death. Although a precursor of dopamine and inhibitors of dopamine degradation have been used for PD therapy, cell death progresses during treatment. DJ-1, a causative gene product of a familial form of PD, PARK7, plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 has been observed in patients with the sporadic form of PD. In this study, we isolated compounds that bind to the region at C106 by a virtual screening. These compounds prevented oxidative stress-induced death of SH-SY5Y cells, embryonic stem cell-derived dopaminergic cells and primary neuronal cells of the ventral mesencephalon, but not that of DJ-1-knockdown cells of SH-SY5Y and NIH3T3 cells, indicating that the effect of the compounds is specific to DJ-1. These compounds inhibited production of reactive oxygen species and restored activities of mitochondrial complex I and tyrosine hydroxylase that had been compromised by oxidative stress. These compounds prevented dopaminergic cell death in the substantia nigra and restored movement abnormality in 6-hydroxyldopamine-injected PD model rats. One mechanism of action of these compounds is prevention of superfluous oxidation of DJ-1, and the compounds passed through the blood-brain barrier in vitro. Taken together, the results indicate that these compounds should become fundamental drugs for PD therapy.

DJ-1, a causative gene product of a familial form of Parkinson's disease, is secreted through microdomains.

DJ-1 is secreted into the serum and plasma of patients with various diseases. In this study, DJ-1 was found to be secreted into culture media of various cells and the amount of wild-type DJ-1 secreted was two-fold greater than that of mutant DJ-1 of cysteine at 106 (C106). Furthermore, the oxidative status of more than 90% of the DJ-1 secreted from HeLa cells was SOH and SO2H forms of C106. A portion of DJ-1 in cells was localized in microdomains of the membrane. These findings suggest that DJ-1 is secreted through microdomains and that oxidation of DJ-1 at C106 facilitates the secretion.