Prediction of Compound Bioactivities Using Heat-Diffusion Equation

Machine learning is expected to improve low throughput and high assay cost in cell-based phenotypic screening. However, it is still a challenge to apply machine learning to achieving sufficiently complex phenotypic screening due to imbalanced datasets, non-linear prediction, and unpredictability of new chemotypes. Here, we developed a prediction model based on the heat-diffusion equation (PM-HDE) to address this issue. The algorithm was verified as feasible for virtual compound screening using biotest data of 946 assay systems registered with PubChem. PM-HDE was then applied to actual screening. Based on supervised learning of the data of about 50,000 compounds from biological phenotypic screening with motor neurons derived from ALS-patient-induced pluripotent stem cells, virtual screening of >1.6 million compounds was implemented. We confirmed that PM-HDE enriched the hit compounds and identified new chemotypes. This prediction model could overcome the inflexibility in machine learning, and our approach could provide a novel platform for drug discovery.

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Prediction model based on heat-diffusion equation (PM-HDE) was constructed

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PM-HDE succeeded in increasing the hit ratio and identifying potent compounds

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PM-HDE discovered new chemotypes in compound evaluation with an ALS-patient iPSC panel

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PM-HDE could represent an algorithm for future drug discovery with AI

There remain many intractable diseases with no treatment available, including amyotrophic lateral sclerosis (ALS), for which the development of a cure is crucial. However, compound screening for drug development demands time, energy, and cost, and therefore artificial intelligence (AI) is expected to improve the efficiency of drug discovery. We built a novel machine-learning algorithm to predict hit compounds in compound screening using the heat-diffusion equation (HDE). This prediction model harbors the potential to solve issues that have been challenging for conventional machine learning and to exhibit accurate performance leading to the discovery of new drugs. In fact, the HDE model predicted hits with new chemotypes among millions of compounds for ALS therapeutics using a panel of large numbers of ALS patient-derived induced pluripotent stem cell models (ALS-patient iPSC panel). This algorithm could contribute to the acceleration and development of future drug discoveries using AI.

A novel thin section preparation and staining protocol to increase contrast and resolution of cell details for light microscopy

We developed a novel sectioning and staining method to make high contrast, high resolution sections of plant tissue for light microscopy. Specimens of teosinte (Zea mays L., ssp. mexicana) root tips were fixed and embedded in Technovit 7100™ plastic resin. Thin sections, 1-2.5 μm, were cut and mounted on glass slides. The sections were either treated with RNase or not, then stained with 0.1% toluidine blue O and observed through ∞/0 objective lenses. For light microscopy, the enzyme staining procedure increased resolution and contrast. High magnification ∞/0 objective lenses produced high quality images for digital photography without using a coverslip or immersion oil. Our slide preparation and microscopic analysis were less labor intensive and more rapid than previous methods and enabled rapid and precise alignment of serial transverse sections for both tracking cell lineages and tissue measurements.

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.

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.

[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.

Comparison of preoperative chemotherapy using docetaxel, cisplatin and fluorouracil with cisplatin and fluorouracil in patients with advanced carcinoma of the thoracic esophagus

We retrospectively compared preoperative docetaxel, cisplatin, and fluorouracil (DCF) with cisplatin and fluorouracil (CF) in patients with esophageal cancer. The study included patients with advanced thoracic esophageal carcinoma (excluding T4 tumors) receiving preoperative chemotherapy. In the DCF group, five patients received two courses of treatment every 4 weeks, and 33 patients received three courses every 3 weeks. In the CF group, 38 patients received two courses of treatment every 4 weeks. Patients underwent curative surgery 4-5 weeks after completing chemotherapy. Patient demographic characteristics did not differ between the two study groups. The incidence of a grade 3 or 4 hematologic toxicity was significantly higher in the DCF group (33 patients) than in the CF group (five patients; P < 0.001). Curative resection was accomplished in 79% of patients in the DCF group and 66% in the CF group (P = 0.305). There were no in-hospital deaths. The incidence of perioperative complications did not differ between the groups. A grade 2 or 3 histological response was attained in a significantly higher proportion of patients in the DCF group (63%) than in the CF group (5%; P < 0.001). Progression-free survival and overall survival were significantly higher in the DCF group (P = 0.013, hazard ratio 0.473; P = 0.001, hazard ratio 0.344). In conclusion, a grade 3 or 4 hematologic toxicity was common in the DCF group but was managed by supportive therapy. Histological response rate, progression-free survival, and overall survival were significantly higher in the DCF group compared with the CF group.

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.

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.

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.

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.

[Aortic root replacement for aortic dissection and aortic regurgitation due to aortitis syndrome]

Aortic aneurysms and aortic regurgitation (AR) with aortitis syndrome are occasionally reported in young women. We report a case of aortic dissection with severe AR in an 8-year-old girl. The patient underwent aortic root replacement with a composite graft. Pathological report revealed aortitis syndrome and steroid therapy was continued to suppress further inflammatory vascular reaction.

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.

Association of DJ-1 with chaperones and enhanced association and colocalization with mitochondrial Hsp70 by oxidative stress

DJ-1 is a novel oncogene and causative gene for familial form of the Parkinson's disease (PD). DJ-1 has been shown to play a role in anti-oxidative stress by eliminating reactive oxygen species (ROS). The onset of PD is thought to be caused by oxidative stress and mitochondrial injury, which leads to protein aggregation that results in neuronal cell death. However, the mechanism by which DJ-1 triggers the onset of PD is still not clear. In this study, we analyzed association and localization of DJ-1 and its mutants with various chaperones. The results showed that DJ-1 and its mutants were associated with Hsp70, CHIP and mtHsp70/Grp75, a mitochondria-resident Hsp70, and that L166P and M26I mutants found in PD patients were strongly associated with Hsp70 and CHIP compared to wild-type and other DJ-1 mutants. DJ-1 and its mutants were colocalized with Hsp70 and CHIP in cells. Furthermore, association and colocalization of wildtype DJ-1 with mtHsp70 in mitochondria were found to be enhanced by treatment of cells with H2O2. These results suggest that translocation of DJ-1 to mitochondria after oxidative stress is carried out in association with chaperones.

Feeding behavior and gene expression of appetite-related neuropeptides in mice lacking for neuropeptide Y Y5 receptor subclass

Neuropeptide Y (NPY) is a potent neurotransmitter for feeding. Besides NPY, orexigenic neuropeptides such as agouti-related protein (AgRP), and anorexigenic neuropeptides such as α-melatonin stimulating hormone (MSH) and cocaine-amphetamine-regulated transcript (CART) are also involved in central feeding regulation. During fasting, NPY and AgRP gene expressions are up-regulated and POMC and CART gene expressions are down-regulated in hypothalamus. Based on the network of peptidergic neurons, the former are involved in positive feeding regulation, and the latter are involved in negative feeding, which exert these feeding-regulated peptides especially in paraventricular nucleus (PVN). To clarify the compensatory mechanism of knock-out of NPY system on feeding, change in gene expressions of appetite-related neuropeptides and the feeding behavior was studied in NPY Y5-KO mice. Food intake was increased in Y5-KO mice. Fasting increased the amounts of food and water intake in the KO mice more profoundly. These data indicated the compensatory phenomenon of feeding behavior in Y5-KO mice. RT-PCR and ISH suggested that the compensation of feeding is due to change in gene expressions of AgRP, CART and POMC in hypothalamus. Thus, these findings indicated that the compensatory mechanism involves change in POMC/CART gene expression in arcuate nucleus (ARC). The POMC/CART gene expression is important for central compensatory regulation in feeding behavior.

DJ-1 degrades transthyretin and an inactive form of DJ-1 is secreted in familial amyloidotic polyneuropathy

DJ-1 plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in the onset of Parkinson's disease. DJ-1 has a protease-like structure and transthyretin (TTR), a protein causing familial amyloidotic polyneuropathy (FAP), was identified as a substrate for DJ-1 protease in this study. Both TTR and DJ-1 were secreted into the culture medium under normal conditions, and secreted TTR was not aggregated. Under oxidative conditions, TTR but not DJ-1 was secreted into the culture medium, resulting in aggregation. Mirror images of both the expression patterns and solubility of DJ-1 and TTR were observed in tissues of FAP patients, and an unoxidized form of DJ-1, an inactive form, was secreted into the serum of FAP patients. These results suggest that oxidative stress to cells abrogates secretion of DJ-1 and that secreted DJ-1 degrades aggregated TTR to protect against the onset of FAP.

Potentiation by neuropeptide Y of histamine H1 receptor-mediated contraction in rat blood vessels

Histamine-induced contraction and its potentiation by neuropeptide Y were investigated in rat blood vessels. Rat arteries and veins constricted with single concentrations of histamine dose-dependently (0.1-100 microM). This histamine-induced contraction immediately desensitized. Histamine H1 receptor antagonists, 1 microM mepyramine and 1 microM diphenhydramine, abolished this transient contraction completely, whereas cimetidine, phentolamine, reserpine and tetrodotoxin failed to inhibit the contraction. Histamine H1 receptor mRNA level by reverse transcription-polymerase chain reaction was quite parallel to histamine H1 receptor-mediated contraction, indicating that the contraction is mediated through histamine H1 receptors in the smooth muscle. Neuropeptide Y (10 nM in arteries and 3 nM in veins, respectively) significantly potentiated histamine H1 receptor-mediated contraction via neuropeptide Y1 receptors in most of rat blood vessels. Since the phospholipase C inhibitors, neomycin (1 mM) and 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate (NCDC, 10 microM), respectively, specifically abolished the potentiation, the potentiation by neuropeptide Y may depend on activation of phospholipase C.

Cytoplasmic localization of p63 is associated with poor patient survival in lung adenocarcinoma

AIMS

To determine the significance of p63 protein expression in the development and progression of lung adenocarcinoma.

METHODS AND RESULTS

The expression of p63 was immunohistochemically investigated in 92 cases of lung adenocarcinoma with a maximum diameter of 30 mm or less. p63 expression was observed not only in the nuclei (46/92 cases, 50%), but also in the cytoplasm of neoplastic cells (47/92, 51%). Nuclear localization of p63 was correlated with nuclear accumulation of p53 (P=0.0120), whereas the presence of nuclear p63 had no apparent effect on patient survival. Cytoplasmic localization of p63 was found to be correlated with shorter survival periods by univariate and multivariate analyses (P=0.0486 and P=0.0488, respectively) and the relation was independent of clinicopathological factors. Cytoplasmic localization of p63 was further confirmed by immunoblots of the cytoplasmic fraction of HLC-1, a lung adenocarcinoma cell line which predominately expressed DeltaNp63alpha transcript relative to TAp63 transcript by quantitative reverse transcriptase-polymerase chain reaction.

CONCLUSIONS

Cytoplasmic expression of p63 is an adverse prognostic factor in patients with adenocarcinoma of the lung.

Proper SUMO-1 conjugation is essential to DJ-1 to exert its full activities

DJ-1 is a multifunctional protein that plays roles in transcriptional regulation and antioxidative stress, and loss of its function is thought to result in the onset of Parkinson's disease (PD). Here, we report that DJ-1 was sumoylated on a lysine residue at amino-acid number 130 (K130) by PIASxalpha or PIASy. The K130 mutation abrogated all of the functions of DJ-1, including ras-dependent transformation, cell growth promotion and anti-UV-induced apoptosis activities. Sumoylation of DJ-1 was increased after UV irradiation concomitant with a pI shift to an acidic point of DJ-1. Furthermore, L166P, a mutant DJ-1 found in PD patients, and K130RX, an artificial mutant containing four mutations in DJ-1, were improperly sumoylated, and they became insoluble, partly localized in the mitochondria and degraded by the proteasome system. Both L166P-expressing cells and DJ-1-knockdown cells were found to be highly susceptible to UV-induced cell apoptosis.

DJ-1 interacts with HIPK1 and affects H2O2-induced cell death

DJ-1 is a novel oncogene and causative gene for the familial form of Parkinson's disease (PD). DJ-1 has multiple functions, including anti-oxidative stress by eliminating reactive oxygen species (ROS) and transcriptional regulation as a coactivator, and loss of these functions are thought to trigger the onset of PD. The mechanism underlying the prevention of cell death by DJ-1 is, however, not clear. In this study, we found that DJ-1 directly bound to homeodomaininteracting protein kinase 1 (HIPK1) in vitro and in vivo and that these proteins were colocalized in the nucleus. HIPK1 was then found to be degraded in human H1299 cells transfected with wild-type DJ-1 but not with a C106S DJ-1 mutant, a DJ-1 protein disrupting a catalytic domain of the putative protease, in a dose-dependent manner. Furthermore, although knockdown of either DJ-1 or HIPK1 rendered H1299 cells susceptible to H2O2-induced cell death, double-knockdown of DJ-1 and HIPK1 rendered H1299 cells resistant to H2O2-induced cell death, suggesting that the elevated level of HIPK1 induced by a low level of DJ-1 inhibits oxidative stress-induced cell death.

Prevalence of CD99 protein expression in pancreatic endocrine tumours (PETs)

AIMS

To determine the prevalence of CD99 expression in pancreatic endocrine tumours (PETs). We evaluated CD99 expression and analysed Ki67 labelling by immunohistochemistry in PETs.

METHODS AND RESULTS

Thirty-eight PETs from 33 patients were analysed. CD99 immunoreactivity was consistently observed in normal islets of the pancreas, regardless of the cell type. Tumours comprising more than 30% CD99+ cells were defined as positively immunoreactive for CD99. CD99 expression was observed in 20 of the 38 PETs examined, but not in any of the pancreatic tumours of other histological subtypes (10 ductal adenocarcinomas, five intraductal papillary-mucinous tumours, and two acinar cell tumours). Loss of CD99 expression was related to markers of worse prognosis for PET, including gross local invasion, metastasis to the lymph nodes or other organs, lymphatic or blood vessel invasion, and neuroendocrine carcinoma (NEC). Thus, CD99 expression may have an efficiency comparable to that of high Ki67 labelling index (5% or more) for prognostication.

CONCLUSIONS

CD99 expression was observed frequently and exclusively in PETs, and loss of CD99 expression in PETs was found to be associated with ominous prognostic indicators.

DJ-1 restores p53 transcription activity inhibited by Topors/p53BP3

DJ-1 is a multi-functional protein that plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in onset of Parkinson's disease. Here, we report that DJ-1 bound to Topors/p53BP3, a ring finger protein binding to both topoisomerase I and p53, in vitro and in vivo and that both proteins were colocalized in cells. DJ-1 and p53 were then found to be sumoylated by Topors in cells. It was also found that DJ-1 bound to p53 in vitro and in vivo and that colocalization with and its binding to p53 were stimulated by UV irradiation of cells. Transcription activity of p53 was found to be abrogated by Topors concomitant with sumoylation of p53 in a dose-dependent manner, and DJ-1 restored its repressed activity by releasing the sumoylated form of p53. These findings suggest that DJ-1 positively regulates p53 through Topors-mediated sumoylation.

Stimulation of transforming activity of DJ-1 by Abstrakt, a DJ-1-binding protein

DJ-1 was identified by us as a novel oncogene in cooperation with activated ras. Although over-expression of DJ-1 has been reported in several cancer cells, including cells in breast cancer, lung cancer and prostate cancer, the precise mechanism underlying transformation has not been clarified. In this study, we screened proteins by a yeast two-hybrid method and identified Abstrakt as a DJ-1-binding protein. Abstrakt is an RNA helicase, but it has not yet been characterized. Northern blot analysis showed that human Abstrakt was expressed ubiquitously in all tissues. Abstrakt was then found to bind to and to be colocalized in the nucleus with DJ-1 in human cells. Furthermore, Abstrakt was found to stimulate transforming activity of DJ-1 in rat 3Y1 cells transfected with DJ-1 with activated ras. These findings suggest that Abstrakt is a positive regulator for DJ-1.

Reduced anti-oxidative stress activities of DJ-1 mutants found in Parkinson’s disease patients

DJ-1 is a multi-functional protein that plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in onset of Parkinson's disease. We have previously reported that L166P, a mutant DJ-1 found in Parkinson's disease patients, had no activity to prevent hydrogen peroxide (H2O2)-induced cell death. In this study, we analyzed other mutants of DJ-1 found in Parkinson's disease patients, including M26I, R98Q, and D149A, as well as L166P. We first found that all of the mutants made heterodimers with wild-type DJ-1, while all of the mutants except for L166P made homodimers. We then found that M26I and L166P, both of which are derived from homozygous mutations of the DJ-1 gene, were unstable and that their stabilities were recovered, in part, in the presence of proteasome inhibitor, MG132. NIH3T3 cell lines stably expressing these mutants of DJ-1 showed that cell lines of L166P and C106S, a mutant for protease activity (-) of DJ-1, had no activity to scavenge even endogenously producing reactive oxygen species. These cell lines also showed that all of the mutants had reduced activities to eliminate exogenously added H2O2 and that these activities, except for that of D149A, were parallel to those preventing H2O2-induced cell death.

DJ-1 has a role in antioxidative stress to prevent cell death

Deletion and point (L166P) mutations of DJ-1 have recently been shown to be responsible for the onset of familial Parkinson's disease (PD, PARK7). The aim of this study was to determine the role of DJ-1 in PD. We first found that DJ-1 eliminated hydrogen peroxide in vitro by oxidizing itself. We then found that DJ-1 knockdown by short interfering RNA rendered SH-SY5Y neuroblastoma cells susceptible to hydrogen peroxide-, MPP+- or 6-hydroxydopamine-induced cell death and that cells harbouring mutant forms of DJ-1, including L166P, became susceptible to death in parallel with the loss of oxidized forms of DJ-1. These results clearly showed that DJ-1 has a role in the antioxidative stress reaction and that mutations of DJ-1 lead to cell death, which is observed in PD.

The crystal structure of DJ-1, a protein related to male fertility and Parkinson's disease

DJ-1 is a multifunctional protein that plays essential roles in tissues with higher order biological functions such as the testis and brain. DJ-1 is related to male fertility, and its level in sperm decreases in response to exposure to sperm toxicants. DJ-1 has also been identified as a hydroperoxide-responsive protein. Recently, a mutation of DJ-1 was found to be responsible for familial Parkinson's disease. Here, we present the crystal structure of DJ-1 refined to 1.95-A resolution. DJ-1 forms a dimer in the crystal, and the monomer takes a flavodoxin-like Rossmann-fold. DJ-1 is structurally most similar to the monomer subunit of protease I, the intracellular cysteine protease from Pyrococcus horikoshii, and belongs to the Class I glutamine amidotransferase-like superfamily. However, DJ-1 contains an additional alpha-helix at the C-terminal region, which blocks the putative catalytic site of DJ-1 and appears to regulate the enzymatic activity. DJ-1 may induce conformational changes to acquire catalytic activity in response to oxidative stress.

Crystallization and preliminary crystallographic analysis of DJ-1, a protein associated with male fertility and parkinsonism

DJ-1 was identified as a novel oncogene product that transformed mouse NIH3T3 cells in cooperation with activated Ras. DJ-1 was also correlated with male infertility and parkinsonism. DJ-1 was crystallized using sodium citrate and HEPES at pH 7.5. The crystal belongs to space group P3(1) or P3(2), with unit-cell parameters a = 75.04, c = 74.88 A and contains two molecules in an asymmetric unit. An intensity data set was collected to 2.00 A resolution.

DJBP: a novel DJ-1-binding protein, negatively regulates the androgen receptor by recruiting histone deacetylase complex, and DJ-1 antagonizes this inhibition by abrogation of this complex

DJ-1 was identified by us as a novel oncogene that transforms mouse NIH3T3 cells in cooperation with ras. We later identified PIAS (protein inhibitor of activated STAT)xalpha as a DJ-1-binding protein, and found that DJ-1 restored androgen receptor (AR) transcription activity that was repressed by PIASxalpha. To further characterize the function of DJ-1, we cloned cDNA encoding a novel DJ-1-binding protein, DJBP, by a yeast two-hybrid system. DJBP mRNA was found to be specifically expressed in the testis. In addition to the binding of DJBP to the COOH-terminal region of DJ-1, DJBP was also found to bind in vitro and in vivo to the DNA-binding domain of the AR in a testosterone-dependent manner and to be colocalized with DJ-1 or AR in the nucleus. Furthermore, a co-immunoprecipitation assay showed that the formation of a ternary complex between DJ-1, DJBP, and AR occurred in cells in which DJ-1 bound to the AR via DJBP. It was found that DJBP repressed a testosterone-dependent AR transactivation activity in monkey Cos1 cells by recruiting histone deacetylase (HDAC) complex, including HDAC1 and mSin3, and that DJ-1 partially restored its repressed activity by abrogating DJBP-HDAC complex. These results suggest that AR is positively regulated by DJ-1, which antagonizes the function of negative regulators, including DJBP.

DJ-1, a target protein for an endocrine disrupter, participates in the fertilization in mice

DJ-1 was first identified as an activated ras-dependent oncogene product and was later also found to be an infertility-related protein affected by sperm toxicants such as ornidazole (OR) and epichlorohydrin. These findings suggest that DJ-1 has functions in both somatic cells and sperm. In this study, to determine the relationship between DJ-1 and an endocrine disrupter and to determine the functions of DJ-1 in sperm, in vitro fertilization experiments were carried out using eggs and sperm extracted from mice that had or had not been treated with OR. We found that the amount of DJ-1 in sperm and the efficiency of fertilization decreased with the increasing dose of OR to which the mice were exposed. The addition of an anti-mouse DJ-1 serum to sperm solution before the in vitro fertilization reaction with eggs resulted in a decrease in the efficiency of fertilization to about one-third of that when pre-immune serum was added to sperm solution, indicating that DJ-1 participates in the fertilization.