BAY61-3606 Alters snRNP Composition and Enhances Usage of Suboptimal Splice Acceptor Site

Intron recognition by the spliceosome mainly depends on conserved intronic sequences such as 5' splice sites, 3' splice sites, and branch sites. Therefore, even substitution of just a single nucleotide in a 5' or 3' splice site abolishes the splicing at the mutated site and leads to cryptic splice site usage. A number of disease-causative mutations have been found in 5' and 3' splice sites, but the genes with these mutations still maintain the correct protein-coding sequence, so recovery of splicing at the mutated splice site may produce a normal protein. Mutations in the spliceosome components have been shown to change the balance between the conformational transition and disassembly of the spliceosome, which affects the decision about whether the reaction of the incorporated substrate will proceed. In addition, the lower disassembly rate caused by such mutations induces splicing of the mutated splice site. We hypothesized that small compounds targeting the spliceosome may include a compound mimicking the effect of those mutations. Thus, we screened a small-compound library and identified a compound, BAY61-3606, that changed the cellular small nuclear ribonucleoprotein composition and also showed activity of enhancing splicing at the mutated 3' splice site of the reporter gene, as well as splicing at the suboptimal 3' splice site of endogenous cassette exons. These results indicate that further analysis of the mechanism of action of BAY61-3606 could enable modulation of the fidelity of splicing.

Development of a Cell-Based Assay Using a Split-Luciferase Reporter for Compound Screening

Recently, the finding of recurrent mutations in the spliceosome components in cancer has indicated that the spliceosome is a potential target for cancer therapy. However, the number of small molecules known to affect the cellular spliceosome is currently limited probably because of the lack of a robust cell-based approach to identify small molecules that target the spliceosome. We have previously reported the development of a genetic reporter to detect the cellular levels of small nuclear ribonucleoproteins (snRNPs), which are subunits of the spliceosome, using a split luciferase. However, the original protocol was designed for small scale experiments and was not suitable for compound screening. Here, we found that the use of cell lysis buffer used in blue native polyacrylamide gel electrophoresis (BN-PAGE) dramatically improved the sensitivity and the robustness of the assay. Improved assay conditions were used to discover a small molecule that altered the reporter activity. Our method may be used with other cellular macromolecular complexes and may assist in the discovery of small bioactive molecules.

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.

Effects of a DJ-1-Binding Compound on Spatial Learning and Memory Impairment in a Mouse Model of Alzheimer's Disease

Previously, DJ-1 modulator UCP0054278/comp-B was identified by virtual screening, where comp-B interacts with DJ-1 to produce antioxidant and neuroprotective responses in Parkinson's disease models. However, the effect of comp-B in an in vivo Alzheimer's disease (AD) model is yet undetermined. Thus, we examined the effect of comp-B on spatial learning, memory, and amyloid-β (Aβ) clearance in a transgenic mouse model of AD. We found that comp-B resolved the cognitive deficits, reduced insoluble Aβ42 levels, and prevented the degeneration of synaptic functions, thereby suggesting that comp-B may become a major compound for AD treatment.

Protease activity of legumain is inhibited by an increase of cystatin E/M in the DJ-1-knockout mouse spleen, cerebrum and heart

Legumain (EC 3.4.22.34) is an asparaginyl endopeptidase. Legumain activity has been detected in various mouse tissues including the kidney, spleen and epididymis. Legumain is overexpressed in the majority of human solid tumors and transcription of the legumain gene is regulated by the p53 tumor suppressor in HCT116 cells. The legumain activity is also increased under acid conditions in Alzheimer's disease brains. DJ-1/PARK7, a cancer- and Parkinson's disease-associated protein, works as a coactivator to various transcription factors, including the androgen receptor, p53, PSF, Nrf2, SREBP and RREB1. Recently, we found that legumain expression, activation and cleavage of annexin A2 are regulated by DJ-1 through p53. In this study, we found that the expression levels of legumain mRNA were increased in the cerebrum, kidney, spleen, heart, lung, epididymis, stomach, small intestine and pancreas from DJ-1-knockout mice, although legumain activity levels were decreased in the cerebrum, spleen and heart from DJ-1-knockout mice. Furthermore, we found that cystatin E/M expression was increased in the spleen, cerebrum and heart from DJ-1-knockout mice. These results suggest that reduction of legumain activity is caused by an increase of cystatin E/M expression in the spleen, cerebrum and heart from DJ-1-knockout mice.

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Legumain is strongly activated in the epididymis from DJ-1-knockout mice.

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Expression level of legumain mRNA is increased but activity is decreased in the spleen, cerebrum and heart from DJ-1-knockout mice.

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Expression level of cystatin E/M is increased in the spleen, cerebrum and heart from DJ-1-knockout mice.

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.

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.

Effectiveness of aronia berries for reduction of mild fibrosis and gene expression analysis in livers from mice fed a high-fat diet with aronia berries

Background: Aronia berries have many potential effects on health, including an antioxidant effect, effect for antimutagenesis, hepatoprotection and cardioprotection, an antidiabetic effect and inhibition of cancer cell proliferation. Previous human studies have shown that aronia juice may be useful for treatment of obesity disorders.Objective: To reveal relationship between beneficial effect and the gene expression change by aronia berries, we analyzed mice livers using RNA sequencing and RT-qPCR.Method: At 28 days after starting a normal diet, a high fat diet and a high-fat diet containing 10% freeze-dried aronia berries, serum was obtained from veins of mice after isoflurane anesthesia, and liver tissues were isolated and weighed. Triglyceride, total cholesterol and LDL cholesterol levels were measured and total RNAs were extracted. cDNA libraries were prepared according to Illumina protocols and sequenced using an Illumina HiSeq2500 to perform 100 paired-end sequencing. RNA-sequence reads mapping was performed using a DNA nexus. Gene expression analysis was performed. The liver tissue specimens were fixed and embedded in paraffin. After 5-mm-thick paraffin sections had been cut, they were stained with hematoxylin-eosin using the standard procedure and also with Sirius Red.Results: In this study, we found that mild fibrosis induced by a high-fat diet was reduced in livers of mice fed a high-fat diet containing aronia berries. RNA sequencing and RT-qPCR analyses revealed that gene expression levels of Igfbp1 and Gadd45g were increased in livers from mice fed a high-fat diet containing aronia berries. Furthermore, results of an enzyme-linked immunoassay showed that a secreted protein levels of FABP1 and FABP4 were reduced in serum from mice fed a high-fat diet containing aronia berries. The results suggest that aronia berries have beneficial effects on mild fibrosis in liver.Conclusion: Aronia berries have a beneficial effect on liver fibrosis. The recovery from liver fibrosis is associated with expression levels of Gadd45g and Igfbp1 in the liver. The beneficial effects of aronia berries on liver fibrosis reduce the risk of liver cancer diseases and insulin resistance, resulting in reduction of serum FABP1 and FABP4 levels.Keywords: aronia; fibrosis; liver; Igfbp1; Gadd45g

Improvement of blood glucose levels and obesity in mice given aronia juice by inhibition of dipeptidyl peptidase IV and α-glucosidase

Aronia berries have many potential effects on health. Previous human studies have shown that aronia juice may be useful for treatment of obesity disorders. Recently, we have reported that aronia juice has an inhibitory effect on dipeptidyl peptidase (DPP IV) activity and that the DPP IV inhibitor in aronia juice was identified as cyanidin 3,5-diglucoside. In this study, we found that body weights and blood glucose levels were reduced in diabetes model KK-Ay mice given aronia juice. We also found that weights of white adipose tissues were reduced in KK-Ay mice given aronia juice. Furthermore, levels of DPP IV activity in the serum and liver from KK-Ay mice were lower than those in the serum and liver from C57BL/6JmsSlc mice. Interestingly, although levels of DPP IV activity were not changed in the serum and liver from aronia-juice-administered KK-Ay mice, levels of DPP IV activity were increased in those from aronia-juice-administered C57BL/6JmsSlc mice. Furthermore, α-glucosidase activity was inhibited in the upper region of the small intestine from aronia-juice-administered KK-Ay mice but not in the lower region. Inhibition of α-glucosidase activity in the upper portion of the small intestine induced a reduction of glucose-dependent insulinotropic polypeptide (GIP) level. The results suggest that DPP IV activity in diabetic mice is inhibited by aronia juice, that the GIP level in the upper region of the small intestine is reduced by inhibition of α-glucosidase activity and that weights of adipose tissues are reduced by aronia juice.

Common mechanisms of onset of cancer and neurodegenerative diseases

Onset of cancer and neurodegenerative disease occurs by abnormal cell growth and neuronal cell death, respectively, and the number of patients with both diseases has been increasing in parallel with an increase in mean lifetime, especially in developed countries. Although both diseases are sporadic, about 10% of the diseases are genetically inherited, and analyses of such familial forms of gene products have contributed to an understanding of the molecular mechanisms underlying the onset and pathogenesis of these diseases. I have been working on c-myc, a protooncogene, for a long time and identified various c-Myc-binding proteins that play roles in c-Myc-derived tumorigenesis. Among these proteins, some proteins have been found to be also responsible for the onset of neurodegenerative diseases, including Parkinson's disease, retinitis pigmentosa and cerebellar atrophy. In this review, I summarize our findings indicating the common mechanisms of onset between cancer and neurodegenerative diseases, with a focus on genes such as DJ-1 and Myc-Modulator 1 (MM-1) and signaling pathways that contribute to the onset and pathogenesis of cancer and neurodegenerative diseases.

Structure determination of the rutile-TiO2(110)-(1 × 2) surface using total-reflection high-energy positron diffraction (TRHEPD)

Detailed structure of the rutile-TiO₂(110)-(1 × 2) has been determined using the newly developed technique of total-reflection high-energy positron diffraction (TRHEPD).

Expression and protease activity of mouse legumain are regulated by the oncogene/transcription co-activator, DJ-1 through p53 and cleavage of annexin A2 is increased in DJ-1-knockout cells

Legumain (EC 3.4.22.34) is an asparaginyl endopeptidase. Strong legumain activity was observed in the mouse kidney, and legumain was highly expressed in tumors. We previously reported that bovine kidney annexin A2 was co-purified with legumain and that legumain cleaved the N-terminal region of annexin A2 at an Asn residue in vitro and in vivo. Recently, we found that transcription of the legumain gene is regulated by the p53 tumor suppressor in HCT116 cells. We and others reported that DJ-1/PARK7, a cancer- and Parkinson's disease-associated protein, works as a coactivator to various transcription factors, including the androgen receptor, p53, PSF, Nrf2, SREBP and RREB1. In this study, we found that expression levels of legumain mRNA and protein and legumain activity were increased in DJ-1-knockout cells. Furthermore, we found that DJ-1 binds to the p53-binding site on intron 1 of the mouse legumain gene in wild-type cells and that cleavage of annexin A2 was increased in DJ-1-knockout cells. These results suggest that legumain expression and activation and cleavage of annexin A2 are regulated by DJ-1 through p53.

DJ-1 Protects Pancreatic Beta Cells from Cytokine- and Streptozotocin-Mediated Cell Death

A hallmark feature of type 1 and type 2 diabetes mellitus is the progressive dysfunction and loss of insulin-producing pancreatic beta cells, and inflammatory cytokines are known to trigger beta cell death. Here we asked whether the anti-oxidant protein DJ-1 encoded by the Parkinson’s disease gene PARK7 protects islet cells from cytokine- and streptozotocin-mediated cell death. Wild type and DJ-1 knockout mice (KO) were treated with multiple low doses of streptozotocin (MLDS) to induce inflammatory beta cell stress and cell death. Subsequently, glucose tolerance tests were performed, and plasma insulin as well as fasting and random blood glucose concentrations were monitored. Mitochondrial morphology and number of insulin granules were quantified in beta cells. Moreover, islet cell damage was determined in vitro after streptozotocin and cytokine treatment of isolated wild type and DJ-1 KO islets using calcein AM/ethidium homodimer-1 staining and TUNEL staining. Compared to wild type mice, DJ-1 KO mice became diabetic following MLDS treatment. Insulin concentrations were substantially reduced, and fasting blood glucose concentrations were significantly higher in MLDS-treated DJ-1 KO mice compared to equally treated wild type mice. Rates of beta cell apoptosis upon MLDS treatment were twofold higher in DJ-1 KO mice compared to wild type mice, and in vitro inflammatory cytokines led to twice as much beta cell death in pancreatic islets from DJ-1 KO mice versus those of wild type mice. In conclusion, this study identified the anti-oxidant protein DJ-1 as being capable of protecting pancreatic islet cells from cell death induced by an inflammatory and cytotoxic setting.

A Splicing Reporter Tuned to Non-AG Acceptor Sites Reveals that Luteolin Enhances the Recognition of Non-canonical Acceptor Sites

Removal of an intron requires precise recognition of the splice donor and acceptor sites located at the 5' and 3' termini of introns. Although the roles of these sequences differ, mutations in both sites easily block normal splicing and produce an aberrant mRNA. For example, many splice-site mutations occur in patients with inherited diseases. Several approaches have been evaluated to restore expression of a functional protein; however, because of the strict requirement for an AG dinucleotide at the 3' terminus of a U2-type intron, no method is available to correct splicing at a mutated sequence. To identify compounds that allow splicing at the non-AG acceptor site, in the present study we constructed a reporter gene with a modified polypyrimidine tract. However, the modified polypyrimidine tract mediated splicing at adjacent non-canonical acceptor sites, including the original mutated site. Further, we show that certain flavones such as luteolin and apigenin enhanced aberrant splicing at the non-canonical acceptor site of the reporter gene. These results suggest that the reporter gene and luteolin may be useful for further screening to identify molecules that correct aberrant splicing caused by a disease-associated splice acceptor site mutation.

Effect of 5-hydroxytryptamine receptor 4 agonist mosapride on human gastric accommodation

BACKGROUND

Impaired gastric accommodation is one of the major features of functional dyspepsia. Mosapride citrate is a 5-hydroxytryptamine receptor 4 (5-HT4) agonist, which is shown to improve upper abdominal symptoms. However, effect of mosapride on gastric accommodation was not clear. We tested the hypothesis that mosapride enhances the gastric accommodation in normal individuals.

METHODS

Fourteen male healthy volunteers completed this study. Single administration of mosapride or placebo was performed randomly with more than 1-week interval. Subjects swallowed a triple-lumen polyvinyl tube with a polyethylene bag. The bag was positioned in the proximal stomach and the minimal distending pressure (MDP) was determined. The ramp distension starting from the MDP was then performed and subjects were instructed to score their perception using ordinate scales. Next the intra-bag pressure was set at MDP + 2 mmHg and a liquid meal was administered 30 min later, and the intra-bag volume was recorded for 60 min. We compared the MDP, perception scores, and the intra-bag volume changes by administering placebo and mosapride.

KEY RESULTS

Minimal distending pressure was not significantly different in subjects receiving mosapride or placebo. Treatment with mosapride had no effect on intra-bag pressures or volumes inducing first sensation or discomfort. Gastric accommodation, expressed as the difference between pre- and postmeal intra-bag volumes, and the percent change of the intra-bag volumes by the meal was significantly enhanced by mosapride compared with placebo.

CONCLUSIONS & INFERENCES

This is the first study clearly demonstrating that single administration of 5-HT4 agonist can enhance gastric accommodation in humans. (Umin.ac.jp, number UMIN000014063).

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.

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.

Rapid and simple purification of lysozyme from the egg shell membrane

Lysozyme (EC 3.2.1.17) is a hydrolytic enzyme that cleaves the β-(1,4)-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, a major bacterial cell wall polymer. In the food industry, lysozyme is used as an additive mainly in the production of wine and beer. Lysozyme was found to be localized in the egg shell membrane. In this study, we found that lysozyme was easily purified from the egg shell membrane and that the enzyme also had antibacterial activity. Furthermore, we found that the antibacterial activity of purified lysozyme from the egg shell membrane was lower than that of purified lysozyme from the egg white at alkaline pH. The method for rapid purification of lysozyme developed in this study should contribute to the food industry.

Deficiency of spermatogenesis and reduced expression of spermatogenesis-related genes in prefoldin 5-mutant mice

MM-1α is a c-Myc-binding protein and acts as a transcriptional co-repressor in the nucleus. MM-1α is also PDF5, a subunit of prefoldin that is chaperon comprised of six subunits and prevents misfolding of newly synthesized nascent polypeptides. Prefoldin also plays a role in quality control against protein aggregation. It has been reported that mice harboring the missense mutation L110R of MM-1α/PFD5 exhibit neurodegeneration in the cerebellum and also male infertility, but the phenotype of infertility has not been fully characterized. In this study, we first analyzed morphology of the testis and epididymis of L110R of MM-1α mice. During differentiation of spermatogenesis, spermatogonia, spermatocytes and round spermatids were formed, but formation of elongated spermatids was compromised in L110R MM-1α mice. Furthermore, reduced number/concentration of sperm in the epididymis was observed. MM-1α was strongly expressed in the round spermatids and sperms with round spermatids, suggesting that MM-1α affects the differentiation and maturation of germ cells. Changes in expression levels of spermatogenesis-related genes in mice testes were then examined. The fatty-acid-binding protein (fabp4) gene was up-regulated and three genes, including sperm-associated glutamate (E)-rich protein 4d (speer-4d), phospholipase A2-Group 3 (pla2g3) and phospholipase A2-Group 10 (pla2g10), were down-regulated in L110R MM-1α mice. L110R MM-1α and wild-type MM-1α bound to regions of up-regulated and down-regulated genes, respectively. Since these gene products are known to play a role in maturation and motility of sperm, a defect of at least MM-1α transcriptional activity is thought to induce expressional changes of these genes, resulting in male infertility.

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.

Serum DJ-1 level is positively associated with improvements in some aspects of metabolic syndrome in Japanese women through lifestyle intervention

DJ-1 is a protein that is associated with Parkinson disease and cancer, and the reduction of DJ-1 function and expression is also thought to be a cause of diabetes and hypertension. However, little is known about the association between the plasma concentration of DJ-1 and risk of metabolic syndrome. We hypothesized that a lifestyle intervention would increase serum DJ-1 and that up-regulated DJ-1 functions will result in the prevention of metabolic syndrome. The objective of our study is to examine whether the level of serum DJ-1 is associated with the risk of metabolic syndrome. Therefore, to reveal the association between DJ-1 and metabolic syndrome, this study investigated lifestyle intervention in a control group (n = 37) and intervention group (n = 45). The results showed that body mass index, body fat ratio, waist-hip ratio, waist circumference, blood pressure, and plasma glucose level were improved in the intervention group, as compared with those in the control group. Furthermore, serum levels of DJ-1 were increased in the intervention group, when compared with those in the control group. These results suggest that serum DJ-1 is increased by lifestyle intervention and that increased serum DJ-1 prevents metabolic syndrome. Thus, the level of serum DJ-1 will become one of the indexes for the risk of metabolic syndrome.

A split luciferase-based reporter for detection of a cellular macromolecular complex

The spliceosome is a highly dynamic macromolecular ribonucleoprotein (RNP) machine that catalyzes pre-mRNA splicing by assembling U1, U2, U4, U5, and U6 small nuclear RNPs (snRNPs). To process large numbers of introns with a limited number of snRNPs, synthesis and recycling of snRNPs must be maintained within an appropriate range to avoid their shortage. However, the mechanism that maintains cellular snRNP levels is unknown. Molecules that modulate cellular snRNP levels may help to define this mechanism but are not available. Therefore, the goal of the current study was to develop a reporter for snRNP levels using split luciferase based on proteomic analysis of snRNPs. We constructed an expression library of a luciferase fragment fused to core components of U5 snRNP and used it to isolate pre-mRNA processing factor 6 (PRPF6) and small nuclear ribonucleoprotein 40 kDa (U5-40K) that specifically reconstitute luciferase activity in the U5 snRNP complex. Here we show that this reporter detects the effects of small molecules on the levels of the U5 snRNP reporter protein complex. Our approach provides an alternative assay to discover small molecules targeting a macromolecular complex when the structure of the complex is not precisely identified.

[Function of DJ-1 in mitochondria]

Parkinson's disease is a degenerative disorder of the central nervous system caused by selective dopamine-generating cell death, and oxidative stress and mitochondrial dysfunction are thought to be responsible for the onset of Parkinson's disease. While most cases of Parkinson's disease are idiopathic, 5-10% of cases are attributed to genetic factors. DJ-1 was first identified as an activated ras-dependent oncogene and later found to be a causative gene for a familial form of Parkinson's disease, PARK7. We and others found that DJ-1 plays roles in transcriptional regulation and anti-oxidative stress function, and loss of its function is thought to affect the onset of Parkinson's disease. DJ-1 is mainly located in the cytoplasma and nucleus and partially in mitochondria. When mice or mouse cells were treated with bisphenol A, an endocrine disruptor and inducer of reactive oxygen species, DJ-1 was translocated into mitochondria to maintain mitochondrial complex I activity. We also found that DJ-1 directly bound to and was co-localized with NDUFA4 and ND1, nuclear and mitochondrial DNA-encoding subunits of mitochondrial complex I, respectively, and that these associations were enhanced by oxidative stress. Furthermore, complex I activity was reduced in two types of DJ-1-knockdown NIH3T3 and HEK293 cells. These findings suggest that DJ-1 is an integral mitochondrial protein and maintains mitochondrial complex I activity to regulate mitochondrial homeostasis.

Prefoldin prevents aggregation of α-synuclein

Protein aggregation is observed in various neurodegeneration diseases, including Parkinson's disease (PD). Alpha-synuclein, a causative gene product of familial PD, is a major component of large aggregates (inclusion bodies) in PD. Prefoldin, a molecular chaperone comprised of six subunits, PFD1~6, prevents misfolding of newly synthesized nascent polypeptides and also prevents aggregation of protein such as a pathogenic form of Huntingtin, a causative gene product of Huntington disease. In this study, we first found that aggregation of TagRFP-tagged wild-type α-synuclein and its pathogenic mutants, but not that of GFP-tagged α-synuclein, occurred in transfected Neuro-2a cells. The fluorescence of GFP is weakened under the condition of pH 4.5-5.0, and TagRFP is a stable red fluorescence protein under an acidic condition. Aggregated TagRFP-wild-type α-synuclein and its pathogenic mutants in Neuro-2a cells were ubiquitinated and were colocalized with the prefoldin complex in the lysosome under this condition. Furthermore, knockdown of PFD2 and PFD5 disrupted prefoldin formation in α-synuclein-expressing cells, resulting in accumulation of aggregates of wild-type and pathogenic α-synuclein and in induction of cell death. The levels of aggregation and cell death in pathogenic α-synuclein-transfected cells tended to be higher than those in wild-type α-synuclein-transfected cells. These results suggest that prefoldin works as a protective factor in aggregated α-synuclein-induced cell death.

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.

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.

Identification of the recognition sequence and target proteins for DJ-1 protease

DJ-1, the product of familial Parkinson's disease gene and an oncogene, is a cysteine protease which plays a role in anti-oxidative stress reaction. In this study, we identified the recognition sequence for DJ-1 protease by using recombinant DJ-1 and a peptide library. Protease activity of DJ-1 lacking C-terminal α-helix (DJ-1ΔH9) was stronger than that of full-sized DJ-1, and the most susceptible sequence digested by DJ-1ΔH9 was valine-lysine-valine-alanine (VKVA) under the optimal conditions of pH 5.5 and 0 mM NaCl. Divalent ions, especially Cu²⁺, were inhibitory to DJ-1's protease activity. c-abl oncogene 1 product (ABL1) and kinesin family member 1B (KIF1B) containing VKVA were digested by DJ-1ΔH9.

Results of chemoradiotherapy for stage I esophageal cancer in medically inoperable patients compared with results in operable patients

The purpose of the present study was to evaluate long-term results of chemoradiotherapy for clinical T1b-2N0M0 esophageal cancer and to compare outcomes for operable and inoperable patients. Patients with stage I esophageal cancer (Union for International Cancer Control [UICC] 2009), excluding patients with cT1a esophageal cancer, were studied. All patients had histologically proven squamous cell carcinoma. Operable patients received cisplatin and 5-fluorouracil with concurrent radiotherapy of 60 Gy including a 2-week break. Inoperable patients received nedaplatin and 5-fluorouracil with concurrent radiotherapy of 60-70 Gy without a pause. End-points were overall survival rate (OS), cause-specific survival rate (CSS), progression-free survival rate (PFS), and locoregional control rate (LC). Thirty-seven operable patients and 30 medically inoperable patients were enrolled. There was a significant difference in only age between the operable group and inoperable group (P = 0.04). The median observation period was 67.9 months. In all patients, 5-year OS, CSS, PFS, and LC were 77.9%, 91.5%, 66.9%, and 80.8%, respectively. Comparison of the operable group and inoperable group showed that there was a significant difference in OS (5-year, 85.5% vs. 68.7%, P = 0.04), but there was no difference in CSS, PFS, or LC. Grade 3 or more late toxicity according to Common Terminology Criteria for Adverse Events v 3.0 was found in seven patients. Even in medically inoperable patients with stage I esophageal cancer, LC of more than 80% can be achieved with chemoradiotherapy. However, OS in medically inoperable patients is significantly worse than that in operable patients.

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 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.

ER-stress-associated functional link between Parkin and DJ-1 via a transcriptional cascade involving the tumor suppressor p53 and the spliced X-box binding protein XBP-1

Parkin and DJ-1 are two multi-functional proteins linked to autosomal recessive early-onset Parkinson's disease (PD) that have been shown to functionally interact by as-yet-unknown mechanisms. We have delineated the mechanisms by which parkin controls DJ-1. Parkin modulates DJ-1 transcription and protein levels via a signaling cascade involving p53 and the endoplasmic reticulum (ER)-stress-induced active X-box-binding protein-1S (XBP-1S). Parkin triggers the transcriptional repression of p53 while p53 downregulates DJ-1 protein and mRNA expressions. We show that parkin-mediated control of DJ-1 is fully p53-dependent. Furthermore, we establish that p53 lowers the protein and mRNA levels of XBP-1S. Accordingly, we show that parkin ultimately upregulates XBP-1 levels. Subsequently, XBP-1S physically interacts with the DJ-1 promoter, thereby enhancing its promoter trans-activation, mRNA levels and protein expression. This data was corroborated by the examination of DJ-1 in both parkin- and p53-null mice brains. This transcriptional cascade is abolished by pathogenic parkin mutations and is independent of its ubiquitin-ligase activity. Our data establish a parkin-dependent ER-stress-associated modulation of DJ-1 and identifies p53 and XBP-1 as two major actors acting downstream of parkin in this signaling cascade in cells and in vivo. This work provides a mechanistic explanation for the increase in the unfolded protein response observed in PD pathology, i.e. that it is due to a defect in parkin-associated control of DJ-1.

Monomer DJ-1 and its N-terminal sequence are necessary for mitochondrial localization of DJ-1 mutants

DJ-1 is a novel oncogene and also a causative gene for familial Parkinson’s disease (park7). DJ-1 has multiple functions that include transcriptional regulation, anti-oxidative reaction and chaperone and mitochondrial regulation. Mitochondrial dysfunction is observed in DJ-1-knockout mice and fry, and mitochondrial DJ-1 is more protective against oxidative stress-induced cell death. Although translocation of DJ-1 into mitochondria is enhanced by oxidative stress that leads to oxidation of cysteine 106 (C106) of DJ-1, the characteristics of mitochondrial DJ-1 and the mechanism by which DJ-1 is translocated into mitochondria are poorly understood. In this study, immunostaining, co-immunoprecipitation, cell fractionation and pull-down experiments showed that mutants of glutamine 18 (E18) DJ-1 are localized in mitochondria and do not make homodimers. Likewise, DJ-1 with mutations of two cysteines located in the dimer interface, C46S and C53A, and pathogenic mutants, M26I and L166P DJ-1, were found to be localized in mitochondria and not to make homodimers. Mutant DJ-1 harboring both E18A and C106S, in which C106 is not oxidized, was also localized in mitochondria, indicating that oxidation of C106 is important but not essential for mitochondrial localization of DJ-1. It should be noted that E18A DJ-1 was translocated from mitochondria to the cytoplasm when mitochondrial membrane potential was reduced by treatment of cells with CCCP, an uncoupler of the oxidative phosphorylation system in mitochondria. Furthermore, deletion or substitution of the N-terminal 12 amino acids in DJ-1 resulted in re-localization of E18A, M26I and L166P DJ-1 from mitochondria into the cytoplasm. These findings suggest that a monomer and the N-terminal 12 amino acids are necessary for mitochondrial localization of DJ-1 mutants and that conformation change induced by C106 oxidation or by E18 mutation leads to translocation of DJ-1 into mitochondria.

Therapeutic effects of human mesenchymal and hematopoietic stem cells on rotenone-treated parkinsonian mice

To appreciate the potential applications of stem cell technology in neurodegenerative diseases, including Parkinson's disease (PD), it is important to understand the characteristics of the various types of stem cells. In this study, we designed a set of experiments to compare the ability of three types of human stem cells--mesenchymal stem cells (MSCs), bone marrow CD34(+) cells (BM), and cord blood CD34(+) cells (CB)--using rotenone-treated NOD/SCID mice. Rotenone was orally administered once daily at a dose of 30 mg/kg for 56 days to induce a parkinsonian phenotype. Intravenous delivery of CB into rotenone-treated mice was slightly more beneficial than that of MSCs or BM according to both histological and behavioral analyses. Human nucleus (hNu)(+) cells, which are a specific marker of human cells, were observed in the striatum of rotenone-treated mice transplanted with stem cells. These hNu(+) cells expressed tyrosine hydroxylase (TH). Additionally, α-synuclein(+)/TH(+) cells in the substantia nigra pars compacta decreased significantly following stem cell transplantation. Immunohistochemical analysis also revealed that chronic exposure to rotenone decreased glial cell line-derived neurotrophic factor immunoreactivity and that the reduction was improved by each stem cell transplantation. Gene expression analyses revealed that MSCs, BM, and CB expressed several neurotrophic factors. These results suggest that the beneficial effects of intravenous delivery of stem cells into rotenone-treated mice may result not only from a neurotrophic effect but also from endogenous brain repair mechanisms and the potential of intravenous delivery of stem cells derived from an autologous source for clinical applications in PD.

Rabring7 degrades c-Myc through complex formation with MM-1

We have reported that a novel c-Myc-binding protein, MM-1, repressed E-box-dependent transcription and transforming activities of c-Myc and that a mutation of A157R in MM-1, which is often observed in patients with leukemia or lymphoma, abrogated all of the repressive activities of MM-1 toward c-Myc, indicating that MM-1 is a novel tumor suppressor. MM-1 also binds to the ubiquitin-proteasome system, leading to degradation of c-Myc. In this study, we identified Rabring7, a Rab7-binding and RING finger-containing protein, as an MM-1-binding protein, and we found that Rabring7 mono-ubiquitinated MM-1 in the cytoplasm without degradation of MM-1. Rabring7 was also found to bind to c-Myc and to ubiquitinate c-Myc in a threonine 58-dependent manner. When c-Myc was co-transfected with MM-1 and Rabring7, c-Myc was degraded. Furthermore, it was found that c-Myc was stabilized in MM-1-knockdown cells even when Rabring7 was transfected and that Rabring7 was bound to and co-localized with MM-1 and c-Myc after MM-1 and Rabring7 had been translocated from the cytoplasm to the nucleus. These results suggest that Rabring7 stimulates c-Myc degradation via mono-ubiquitination of MM-1.

Transcriptional activation of low-density lipoprotein receptor gene by DJ-1 and effect of DJ-1 on cholesterol homeostasis

DJ-1 is a novel oncogene and also causative gene for familial Parkinson’s disease park7. DJ-1 has multiple functions that include transcriptional regulation, anti-oxidative reaction and chaperone and mitochondrial regulation. For 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 the low-density lipoprotein receptor (LDLR) gene is a transcriptional target gene for DJ-1. Reduced expression of LDLR mRNA and protein was observed in DJ-1-knockdown cells and DJ-1-knockout mice and this occurred at the transcription level. Reporter gene assays using various deletion and point mutations of the LDLR promoter showed that DJ-1 stimulated promoter activity by binding to the sterol regulatory element (SRE) with sterol regulatory element binding protein (SREBP) and that stimulating activity of DJ-1 toward LDLR promoter activity was enhanced by oxidation of DJ-1. Chromatin immunoprecipitation, gel-mobility shift and co-immunoprecipitation assays showed that DJ-1 made a complex with SREBP on the SRE. Furthermore, it was found that serum LDL cholesterol level was increased in DJ-1-knockout male, but not female, mice and that the increased serum LDL cholesterol level in DJ-1-knockout male mice was cancelled by administration with estrogen, suggesting that estrogen compensates the increased level of serum LDL cholesterol in DJ-1-knockout female mice. This is the first report that DJ-1 participates in metabolism of fatty acid synthesis through transcriptional regulation of the LDLR gene.

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.

CHFR protein regulates mitotic checkpoint by targeting PARP-1 protein for ubiquitination and degradation

The mitotic checkpoint gene CHFR (checkpoint with forkhead-associated (FHA) and RING finger domains) is silenced by promoter hypermethylation or mutated in various human cancers, suggesting that CHFR is an important tumor suppressor. Recent studies have reported that CHFR functions as an E3 ubiquitin ligase, resulting in the degradation of target proteins. To better understand how CHFR suppresses cell cycle progression and tumorigenesis, we sought to identify CHFR-interacting proteins using affinity purification combined with mass spectrometry. Here we show poly(ADP-ribose) polymerase 1 (PARP-1) to be a novel CHFR-interacting protein. In CHFR-expressing cells, mitotic stress induced the autoPARylation of PARP-1, resulting in an enhanced interaction between CHFR and PARP-1 and an increase in the polyubiquitination/degradation of PARP-1. The decrease in PARP-1 protein levels promoted cell cycle arrest at prophase, supporting that the cells expressing CHFR were resistant to microtubule inhibitors. In contrast, in CHFR-silenced cells, polyubiquitination was not induced in response to mitotic stress. Thus, PARP-1 protein levels did not decrease, and cells progressed into mitosis under mitotic stress, suggesting that CHFR-silenced cancer cells were sensitized to microtubule inhibitors. Furthermore, we found that cells from Chfr knockout mice and CHFR-silenced primary gastric cancer tissues expressed higher levels of PARP-1 protein, strongly supporting our data that the interaction between CHFR and PARP-1 plays an important role in cell cycle regulation and cancer therapeutic strategies. On the basis of our studies, we demonstrate a significant advantage for use of combinational chemotherapy with PARP inhibitors for cancer cells resistant to microtubule inhibitors.

Neuroprotective effect of a new DJ-1-binding compound against neurodegeneration in Parkinson's disease and stroke model rats

Background

Parkinson's disease (PD) and cerebral ischemia are chronic and acute neurodegenerative diseases, respectively, and onsets of these diseases are thought to be induced at least by oxidative stress. PD is caused by decreased dopamine levels in the substantia nigra and striatum, and cerebral ischemia occurs as a result of local reduction or arrest of blood supply. Although a precursor of dopamine and inhibitors of dopamine degradation have been used for PD therapy and an anti-oxidant have been used for cerebral ischemia therapy, cell death progresses during treatment. Reagents that prevent oxidative stress-induced cell death are therefore necessary for fundamental therapies for PD and cerebral ischemia. 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.

Results

In this study, a compound, comp-23, that binds to DJ-1 was isolated by virtual screening. Comp-23 prevented oxidative stress-induced death of SH-SY5Y cells and primary neuronal cells of the ventral mesencephalon but not that of DJ-1-knockdown SH-SY5Y cells, indicating that the effect of the compound is specific to DJ-1. Comp-23 inhibited the production of reactive oxygen species (ROS) induced by oxidative stress and prevented excess oxidation of DJ-1. Furthermore, comp-23 prevented dopaminergic cell death in the substantia nigra and restored movement abnormality in 6-hydroxyldopamine-injected and rotenone-treated PD model rats and mice. Comp-23 also reduced infarct size of cerebral ischemia in rats that had been induced by middle cerebral artery occlusion. Protective activity of comp-23 seemed to be stronger than that of previously identified compound B.

Conclusions

The results indicate that comp-23 exerts a neuroprotective effect by reducing ROS-mediated neuronal injury, suggesting that comp-23 becomes a lead compound for PD and ischemic neurodegeneration therapies.

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.

Oxidative stress induction of DJ-1 protein in reactive astrocytes scavenges free radicals and reduces cell injury

Astrocytes, one of the predominant types of glial cells, function as both supportive and metabolic cells for the brain. Under cerebral ischemia/reperfusion-induced oxidative conditions, astrocytes accumulate and activate in the ischemic region. DJ-1 has recently been shown to be a sensor of oxidative stress in living cells. However, the function of astrocytic DJ-1 is still unknown. In the present study, to clarify the effect of astrocytic DJ-1 protein under massive oxidative insult, we used a focal ischemic rat model that had been subjected to middle cerebral artery occlusion (MCAO) and reperfusion. We then investigated changes in the distribution of DJ-1 in astrocytes, DJ-1 release from cultured astrocytes, and the effects of recombinant DJ-1 protein on hydrogen peroxide (H(2)O(2))-induced death in normal and DJ-1-knockdown SH-SY5Y cells and on in vitro scavenging of hydroxyl radicals ((*)OH) by electron spin resonance spectrometry. At 24 h after 2-h MCAO and reperfusion, an infarct lesion was markedly observed using magnetic resonance imaging and 2,3,5-triphenyltetrazolium chloride staining. In addition, reactive astrocytes enhanced DJ-1 expression in the penumbral zone of the ischemic core and that DJ-1 protein was extracellularly released from astrocytes by H2O2 in in vitro primary cultures. Although DJ-1-knockdown SH-SY5Y cells were markedly vulnerable to oxidative stress, treatment with glutathione S-transferase-tagged recombinant human DJ-1 protein (GST-DJ-1) significantly inhibited H(2)O(2)-induced cell death. In addition, GST-DJ-1 protein directly scavenged (*)OH. These results suggest that oxidative stress induces the release of astrocytic DJ-1 protein, which may contribute to astrocyte-mediated neuroprotection.