DJ-1, a cancer and Parkinson's disease associated protein, regulates autophagy through JNK pathway in cancer cells

Knockdown of DJ-1 Resulted in a Coordinated Activation of the Innate Immune Antiviral Response in HEK293 Cell Line

PARK7, also known as DJ-1, plays a critical role in protecting cells by functioning as a sensitive oxidation sensor and modulator of antioxidants. DJ-1 acts to maintain mitochondrial function and regulate transcription in response to different stressors. In this study, we showed that cell lines vary based on their antioxidation potential under basal conditions. The transcriptome of HEK293 cells was tested following knockdown (KD) of DJ-1 using siRNAs, which reduced the DJ-1 transcripts to only 12% of the original level. We compared the expression levels of 14k protein-coding transcripts and 4.2k non-coding RNAs relative to cells treated with non-specific siRNAs. Among the coding genes, approximately 200 upregulated differentially expressed genes (DEGs) signified a coordinated antiviral innate immune response. Most genes were associated with the regulation of type 1 interferons (IFN) and the induction of inflammatory cytokines. About a quarter of these genes were also induced in cells treated with non-specific siRNAs that were used as a negative control. Beyond the antiviral-like response, 114 genes were specific to the KD of DJ-1 with enrichment in RNA metabolism and mitochondrial functions. A smaller set of downregulated genes (58 genes) was associated with dysregulation in membrane structure, cell viability, and mitophagy. We propose that the KD DJ-1 perturbation diminishes the protective potency against oxidative stress. Thus, it renders the cells labile and responsive to the dsRNA signal by activating a large number of genes, many of which drive apoptosis, cell death, and inflammatory signatures. The KD of DJ-1 highlights its potency in regulating genes associated with antiviral responses, RNA metabolism, and mitochondrial functions, apparently through alteration in STAT activity and downstream signaling. Given that DJ-1 also acts as an oncogene in metastatic cancers, targeting DJ-1 could be a promising therapeutic strategy where manipulation of the DJ-1 level may reduce cancer cell viability and enhance the efficacy of cancer treatments.

The reversible low-temperature instability of human DJ-1 oxidative states

DJ-1 is a homodimeric protein that is centrally involved in various human diseases including Parkinson disease (PD). DJ-1 protects against oxidative damage and mitochondrial dysfunction through a homeostatic control of reactive oxygen species (ROS). DJ-1 pathology results from a loss of function, where ROS readily oxidizes a highly conserved and functionally essential cysteine (C106). The over-oxidation of DJ-1 C106 leads to a dynamically destabilized and biologically inactivated protein. An analysis of the structural stability of DJ-1 as a function of oxidative state and temperature may provide further insights into the role the protein plays in PD progression. NMR spectroscopy, circular dichroism, analytical ultracentrifugation sedimentation equilibrium, and molecular dynamics simulations were utilized to investigate the structure and dynamics of the reduced, oxidized (C106-SO2 - ), and over-oxidized (C106-SO3 - ) forms of DJ-1 for temperatures ranging from 5°C to 37°C. The three oxidative states of DJ-1 exhibited distinct temperature-dependent structural changes. A cold-induced aggregation occurred for the three DJ-1 oxidative states by 5°C, where the over-oxidized state aggregated at significantly higher temperatures than both the oxidized and reduced forms. Only the oxidized and over-oxidized forms of DJ-1 exhibited a mix state containing both folded and partially denatured protein that likely preserved secondary structure content. The relative amount of this denatured form of DJ-1 increased as the temperature was lowered, consistent with a cold-denaturation. Notably, the cold-induced aggregation and denaturation for the DJ-1 oxidative states were completely reversible. The dramatic changes in the structural stability of DJ-1 as a function of oxidative state and temperature are relevant to its role in PD and its functional response to oxidative stress.

Loss of DJ-1 function contributes to Parkinson's disease pathogenesis in mice via RACK1-mediated PKC activation and MAO-B upregulation

Parkinson's disease (PD) is a common neurodegenerative motor disorder characterized by a dramatic reduction in pars compacta of substantia nigra dopaminergic neurons and striatal dopamine (DA) levels. Mutations or deletions in the PARK7/DJ-1 gene are associated with an early-onset familial form of PD. DJ-1 protein prevents neurodegeneration via its regulation of oxidative stress and mitochondrial function as well as its roles in transcription and signal transduction. In this study, we investigated how loss of DJ-1 function affected DA degradation, ROS generation and mitochondrial dysfunction in neuronal cells. We showed that loss of DJ-1 significantly increased the expression of monoamine oxidase (MAO)-B but not MAO-A in both neuronal cells and primary astrocytes. In DJ-1-knockout (KO) mice, MAO-B protein levels in the substantia nigra (SN) and striatal regions were significantly increased. We demonstrated that the induction of MAO-B expression by DJ-1 deficiency depended on early growth response 1 (EGR1) in N2a cells. By coimmunoprecipitation omics analysis, we found that DJ-1 interacted with receptor of activated protein C kinase 1 (RACK1), a scaffolding protein, and thus inhibited the activity of the PKC/JNK/AP-1/EGR1 cascade. The PKC inhibitor sotrastaurin or the JNK inhibitor SP600125 completely inhibited DJ-1 deficiency-induced EGR1 and MAO-B expression in N2a cells. Moreover, the MAO-B inhibitor rasagiline inhibited mitochondrial ROS generation and rescued neuronal cell death caused by DJ-1 deficiency, especially in response to MPTP stimulation in vitro and in vivo. These results suggest that DJ-1 exerts neuroprotective effects by inhibiting the expression of MAO-B distributed at the mitochondrial outer membrane, which mediates DA degradation, ROS generation and mitochondrial dysfunction. This study reveals a mechanistic link between DJ-1 and MAO-B expression and contributes to understanding the crosslinks among pathogenic factors, mitochondrial dysfunction and oxidative stress in PD pathogenesis.

Importance of DJ-1 in autophagy regulation and disease

Autophagy is a highly conserved biological process that has evolved across evolution. It can be activated by various external stimuli including oxidative stress, amino acid starvation, infection, and hypoxia. Autophagy is the primary mechanism for preserving cellular homeostasis and is implicated in the regulation of metabolism, cell differentiation, tolerance to starvation conditions, and resistance to aging. As a multifunctional protein, DJ-1 is commonly expressed in vivo and is associated with a variety of biological processes. Its most widely studied role is its function as an oxidative stress sensor that inhibits the production of excessive reactive oxygen species (ROS) in the mitochondria and subsequently the cellular damage caused by oxidative stress. In recent years, many studies have identified DJ-1 as another important factor regulating autophagy; it regulates autophagy in various ways, most commonly by regulating the oxidative stress response. In particular, DJ-1-regulated autophagy is involved in cancer progression and plays a key role in alleviating neurodegenerative diseases(NDS) and defective reperfusion diseases. It could serve as a potential target for the regulation of autophagy and participate in disease treatment as a meaningful modality. Therefore, exploring DJ-1-regulated autophagy could provide new avenues for future disease treatment.

Resveratrol inhibits autophagy against myocardial ischemia-reperfusion injury through the DJ-1/MEKK1/JNK pathway

Resveratrol (RES), a natural polyphenolic compound found in red wine and grape skins, has attracted significant attention due to its cardioprotective properties. DJ-1, a multifunctional protein that participated in transcription regulation and antioxidant defense, was shown to provide a significant protective impact in cardiac cells treated with ischemia-reperfusion. We created a myocardial ischemia-reperfusion (I/R) model in vivo and in vitro by ligating the left anterior descending branch of rats and subjecting H9c2 cells to anoxia/reoxygenation (A/R) to investigate whether RES reduces myocardial ischemia-reperfusion injury by upregulating DJ-1. We discovered that RES dramatically enhanced cardiac function in rats with I/R. Subsequently, we found that RES prevented the rise in autophagy (P62 degradation and LC3-II/LC3-I increase) induced by cardiac ischemia-reperfusion in vitro and in vivo. Notably, the autophagic agonist rapamycin (RAPA) eliminated RES-induced cardioprotective effects. In addition, Further data showed that RES significantly increased the expression of DJ-1 in the myocardium with the treatment of I/R. At the same time, pretreatment with RES reduced phosphorylation of MAPK/ERK kinase kinase 1 (MEKK1) and Jun N-terminal Kinase (JNK) stimulated by cardiac ischemia-reperfusion, and Beclin-1 mRNA and protein levels while decreasing lactate dehydrogenase (LDH) and improving cell viability. However, the lentiviral shDJ-1 and JNK agonist anisomycin disrupted the effects of RES. In summary, RES could inhibit autophagy against myocardial ischemia-reperfusion injury through DJ-1 modulation of the MEKK1/JNK pathway, providing a novel therapeutic strategy for cardiac homeostasis.

DJ-1 Protects Auditory Cells from Cisplatin-induced Ototoxicity via Regulating Apoptosis and Autophagy

AIMS

DJ-1, a multifunctional protein encoded by the Park7 gene, is tightly related to mitochondrial dysfunction, oxidative stress, protein aggregation, and autophagy regulation. The current study was designed to investigate whether DJ-1 is expressed in auditory cells and, if so, to explore the possible correlation between DJ-1 and cisplatin-induced ototoxicity in this type of cells.

METHODS

The location and dynamic expression of DJ-1 in mouse cochlea hair cells (HCs) and House Ear Institute-Organ of Corti 1 (HEI-OC1 cells) were detected by immunofluorescence, real-time PCR, and western blot. The apoptosis of auditory cells was assessed by TUNEL staining and flow cytometry. The levels of ROS were evaluated by MitoSox red staining. The expression of protein cleaved caspase-9, cleaved caspase-3, and LC3B was examined by immunofluorescence and western blot. The expressions of certain key factors relevant to apoptosis (Bcl-2 and Bax) and autophagy (Beclin1, p-JNK, and p-c-Jun) were determined by western blot. The dynamic alterations of those factors in response to DJ-1 knockdown in HEI-OC1 cells (DJ-1-KD) were measured by western blotting and MitoSox red staining.

RESULTS

The expression of DJ-1 was clearly shown in both HCs and HEI-OC1 cells and cisplatin led to the reduction of DJ-1 expression in a concentration and time-dependent manner. Meanwhile, cisplatin-induced apoptotic process was implemented by promoting reactive oxygen species (ROS) production and activating the mitochondrial pathway. Furthermore, DJ-1 explicitly participated in cisplatin-trigged cell damage by regulating autophagy.

CONCLUSIONS

Findings from this work clearly reveal, for the first time, that DJ-1 is expressed in the cochlea. Of particular importance, DJ-1 exerts its protective action against cisplatin-elicited injury on auditory cells via regulating apoptosis and autophagy, which provides a new strategy for the prevention of cisplatin-induced ototoxicity.

DJ-1 promotes energy balance by regulating both mitochondrial and autophagic homeostasis

The protein DJ-1 is mutated in rare familial forms of recessive Parkinson's disease and in parkinsonism accompanied by amyotrophic lateral sclerosis symptoms and dementia. DJ-1 is considered a multitasking protein able to confer protection under various conditions of stress. However, the precise cellular function still remains elusive. In the present work, we evaluated fruit flies lacking the expression of the DJ-1 homolog dj-1β as compared to control aged-matched individuals. Behavioral evaluations included lifespan, locomotion in an open field arena, sensitivity to oxidative insults, and resistance to starvation. Molecular analyses were carried out by analyzing the mitochondrial morphology and functionality, and the autophagic response. We demonstrated that dj-1β null mutant flies are hypoactive and display higher sensitivity to oxidative insults and food deprivation. Analysis of mitochondrial homeostasis revealed that loss of dj-1β leads to larger and more circular mitochondria, characterized by impaired complex-I-linked respiration while preserving ATP production capacity. Additionally, dj-1β null mutant flies present an impaired autophagic response, which is suppressed by treatment with the antioxidant molecule N-Acetyl-L-Cysteine. Overall, our data point to a mechanism whereby DJ-1 plays a critical role in the maintenance of energy homeostasis, by sustaining mitochondrial homeostasis and affecting the autophagic flux through the maintenance of the cellular redox state. In light of the involvement of DJ-1 in neurodegenerative diseases and considering that neurons are highly energy-demanding cells, particularly sensitive to redox stress, our study sheds light on a key role of DJ-1 in the maintenance of cellular homeostasis.

DJ-1 binds to Rubicon to Impair LC-3 Associated Phagocytosis

The ability to effectively clear infection is fundamental to host survival. Sepsis, defined as dysregulated host response to infection, is a heterogenous clinical syndrome that does not uniformly clear intact bacterial or sterile infection (i.e., lipopolysaccharide). These findings were further associated with increased survival in DJ-1 deficient animals exposed to intact bacteria relative to DJ-1 deficient challenged with lipopolysaccharide. We analyzed bacterial and lipopolysaccharide clearance in bone marrow macrophages (BMM) cultured ex vivo from wild-type and DJ-1 deficient mice. Importantly, we demonstrated that DJ-1 deficiency in BMM promotes Rubicon-dependent increase in L3C-associated phagocytosis, non-canonical autophagy pathway used for xenophagy, during bacterial but not lipopolysaccharide infection. In contrast to DJ-1 deficient BMM challenged with lipopolysaccharide, DJ-1 deficient BMM exposed to intact bacteria showed enhanced Rubicon complexing with Beclin-1 and UVRAG and consistently facilitated the assembly of complete autophagolysosomes that were decorated with LC3 molecules. Our data shows DJ-1 impairs or/and delays bacterial clearance and late autophagolysosome formation by binding to Rubicon resulting in Rubicon degradation, decreased L3C-associated phagocytosis, and decreased bacterial clearance in vitro and in vivo - implicating Rubicon and DJ-1 as critical regulators of bacterial clearance in experimental sepsis.

Dync1li1 is required for the survival of mammalian cochlear hair cells by regulating the transportation of autophagosomes

Dync1li1, a subunit of cytoplasmic dynein 1, is reported to play important roles in intracellular retrograde transport in many tissues. However, the roles of Dync1li1 in the mammalian cochlea remain uninvestigated. Here we first studied the expression pattern of Dync1li1 in the mouse cochlea and found that Dync1li1 is highly expressed in hair cells (HCs) in both neonatal and adult mice cochlea. Next, we used Dync1li1 knockout (KO) mice to investigate its effects on hearing and found that deletion of Dync1li1 leads to early onset of progressive HC loss via apoptosis and to subsequent hearing loss. Further studies revealed that loss of Dync1li1 destabilizes dynein and alters the normal function of dynein. In addition, Dync1li1 KO results in a thinner Golgi apparatus and the accumulation of LC3+ autophagic vacuoles, which triggers HC apoptosis. We also knocked down Dync1li1 in the OC1 cells and found that the number of autophagosomes were significantly increased while the number of autolysosomes were decreased, which suggested that Dync1li1 knockdown leads to impaired transportation of autophagosomes to lysosomes and therefore the accumulation of autophagosomes results in HC apoptosis. Our findings demonstrate that Dync1li1 plays important roles in HC survival through the regulation of autophagosome transportation.

Hearing loss is one of the most common sensorial disorders globally. The main reason of hearing loss is the irreversible loss or malfunction of cochlear hair cells. Identifying new hearing loss-related genes and investigating their roles and mechanisms in HC survival are important for the prevention and treatment of hereditary hearing loss. Cytoplasmic dynein 1 is reported to play important roles in in ciliogenesis and protein transport in the mouse photoreceptors. Here, we described the expression pattern of Dyncili1 (a subunit of cytoplasmic dynein 1) in the mouse cochlea and used knockout mice to investigate its specific role in the hair cell of cochlea.

Cytoprotective Mechanisms of DJ-1: Implications in Cardiac Pathophysiology

DJ-1 was originally identified as an oncogene product while mutations of the gene encoding DJ-1/PARK7 were later associated with a recessive form of Parkinson's disease. Its ubiquitous expression and diversity of function suggest that DJ-1 is also involved in mechanisms outside the central nervous system. In the last decade, the contribution of DJ-1 to the protection from ischemia-reperfusion injury has been recognized and its involvement in the pathophysiology of cardiovascular disease is attracting increasing attention. This review describes the current and gaps in our knowledge of DJ-1, focusing on its role in regulating cardiovascular function. In parallel, we present original data showing an association between increased DJ-1 expression and antiapoptotic and anti-inflammatory markers following cardiac and vascular surgical procedures. Future studies should address DJ-1's role as a plausible novel therapeutic target for cardiovascular disease.

The Cross-Links of Endoplasmic Reticulum Stress, Autophagy, and Neurodegeneration in Parkinson's Disease

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, and it is characterized by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc), as well as the presence of intracellular inclusions with α-synuclein as the main component in surviving DA neurons. Emerging evidence suggests that the imbalance of proteostasis is a key pathogenic factor for PD. Endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) and autophagy, two major pathways for maintaining proteostasis, play important roles in PD pathology and are considered as attractive therapeutic targets for PD treatment. However, although ER stress/UPR and autophagy appear to be independent cellular processes, they are closely related to each other. In this review, we focused on the roles and molecular cross-links between ER stress/UPR and autophagy in PD pathology. We systematically reviewed and summarized the most recent advances in regulation of ER stress/UPR and autophagy, and their cross-linking mechanisms. We also reviewed and discussed the mechanisms of the coexisting ER stress/UPR activation and dysregulated autophagy in the lesion regions of PD patients, and the underlying roles and molecular crosslinks between ER stress/UPR activation and the dysregulated autophagy in DA neurodegeneration induced by PD-associated genetic factors and PD-related neurotoxins. Finally, we indicate that the combined regulation of ER stress/UPR and autophagy would be a more effective treatment for PD rather than regulating one of these conditions alone.

DJ-1 Deficiency in Hepatocytes Improves Liver Ischemia-Reperfusion Injury by Enhancing Mitophagy

BACKGROUND & AIMS

DJ-1 is universally expressed in various tissues and organs and is involved in the physiological processes in various liver diseases. However, the role of DJ-1 in liver ischemia-reperfusion (I/R) injury is largely unknown.

METHODS

In this study, we first examined the DJ-1 expression changes in the liver tissues of mice and clinical donor after hepatic I/R by both quantitative polymerase chain reaction and Western blotting assays. Then we investigated the role of DJ-1 in I/R injury by using a murine liver I/R model.

RESULTS

We demonstrated that DJ-1 down-regulation in both human and mouse liver tissues in response to I/R injury and Dj-1 deficiency in hepatocytes but not in myeloid cells could significantly ameliorate I/R induced liver injury and inflammatory responses. This hepatoprotective effect was dependent on enhanced autophagy in Dj-1 knockout mice, because inhibition of autophagy by 3-methyladenine and chloroquine could reverse the protective effect on hepatic I/R injury in Dj-1 knockout mice.

CONCLUSIONS

Dj-1 deficiency in hepatocytes significantly enhanced mitochondrial accumulation and protein stability of PARKIN, which in turn promotes the onset of mitophagy resulting in elevated clearance of damaged mitochondria during I/R injury.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Phosphorylation Modifications Regulating Cardiac Protein Quality Control Mechanisms

Many forms of cardiac disease, including heart failure, present with inadequate protein quality control (PQC). Pathological conditions often involve impaired removal of terminally misfolded proteins. This results in the formation of large protein aggregates, which further reduce cellular viability and cardiac function. Cardiomyocytes have an intricately collaborative PQC system to minimize cellular proteotoxicity. Increased expression of chaperones or enhanced clearance of misfolded proteins either by the proteasome or lysosome has been demonstrated to attenuate disease pathogenesis, whereas reduced PQC exacerbates pathogenesis. Recent studies have revealed that phosphorylation of key proteins has a potent regulatory role, both promoting and hindering the PQC machinery. This review highlights the recent advances in phosphorylations regulating PQC, the impact in cardiac pathology, and the therapeutic opportunities presented by harnessing these modifications.

Methylglyoxal and D-lactate in cisplatin-induced acute kidney injury: Investigation of the potential mechanism via fluorogenic derivatization liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) proteomic analysis

Nephrotoxicity severely limits the chemotherapeutic efficacy of cisplatin (CDDP). Oxidative stress is associated with CDDP-induced acute kidney injury (AKI). Methylglyoxal (MG) forms advanced glycation end products that elevate oxidative stress. We aimed to explore the role of MG and its metabolite D-lactate and identify the proteins involved in CDDP-induced AKI. Six-week-old female BALB/c mice were intraperitoneally administered CDDP (5 mg/kg/day) for 3 or 5 days. Blood urea nitrogen (42.6 ± 7.4 vs. 18.3 ± 2.5; p < 0.05) and urinary N-acetyl-β-D-glucosaminide (NAG; 4.89 ± 0.61 vs. 2.43 ± 0.31 U/L; p < 0.05) were significantly elevated in the CDDP 5-day group compared to control mice. Histological analysis confirmed AKI was successfully induced. Confocal microscopy revealed TNF-α was significantly increased in the CDDP 5-day group. Fluorogenic derivatized liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS) showed the kidney MG (36.25 ± 1.68 vs. 18.95 ± 2.24 mg/g protein, p < 0.05) and D-lactate (1.78 ± 0.29 vs. 1.12 ± 0.06 mol/g protein, p < 0.05) contents were significantly higher in the CDDP 5-day group than control group. FD-LC-MS/MS proteomics identified 33 and nine altered peaks in the CDDP 3-day group and CDDP 5-day group (vs. control group); of the 35 proteins identified using the MOSCOT database, 11 were antioxidant-related. Western blotting confirmed that superoxide dismutase 1 (SOD-1) and parkinson disease protein 7 (DJ-1) are upregulated and may participate with MG in CDDP-induced AKI. This study demonstrates TNF-α, MG, SOD-1 and DJ-1 play crucial roles in CDDP-induced AKI.

Novel Insights into PARK7 (DJ-1), a Potential Anti-Cancer Therapeutic Target, and Implications for Cancer Progression

The expression of PARK7 is upregulated in various types of cancer, suggesting its potential role as a critical regulator of the pathogenesis of cancer and in the treatment of cancer and neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, and Huntington disease. PARK7 activates various intracellular signaling pathways that have been implicated in the induction of tumor progression, which subsequently enhances tumor initiation, continued proliferation, metastasis, recurrence, and resistance to chemotherapy. Additionally, secreted PARK7 has been identified as a high-risk factor for the pathogenesis and survival of various cancers. This review summarizes the current understanding of the correlation between the expression of PARK7 and tumor progression.

Protein Kinase C Isozymes and Autophagy during Neurodegenerative Disease Progression

Protein kinase C (PKC) isozymes are members of the Serine/Threonine kinase family regulating cellular events following activation of membrane bound phospholipids. The breakdown of the downstream signaling pathways of PKC relates to several disease pathogeneses particularly neurodegeneration. PKC isozymes play a critical role in cell death and survival mechanisms, as well as autophagy. Numerous studies have reported that neurodegenerative disease formation is caused by failure of the autophagy mechanism. This review outlines PKC signaling in autophagy and neurodegenerative disease development and introduces some polyphenols as effectors of PKC isozymes for disease therapy.

DJ-1 inhibits autophagy activity of prostate cancer cells by repressing JNK-Bcl2-Beclin1 signaling

The regulation of DJ-1 on AR signaling plays an important role in the pathogenesis of prostate cancer (PCa). DJ-1 could alter autophagy and regulate Beclin1-involved autophagy response through JNK-dependent pathway. JNK is known to mediate autophagy through Bcl2-Beclin1 complex. Therefore, this study aimed to investigate the significance of autophagy in DJ-1-modulated PCa cells. The current studies showed that DJ-1 overexpression in LNCaP decreased LC3 transformation and autophagosome formation. However, DJ-1 knockdown exerted the opposite effect. Moreover, DJ-1 silencing inhibited survival and promoted death in LNCaP, which was recovered by autophagy inhibition with 3-MA. In addition, DJ-1 overexpression inhibited the phosphorylation of JNK and Bcl2, and the dissociation of Beclin1 and Bcl2; while the effect of silencing DJ-1 was completely opposite. More important, JNK activated by anisimycin inhibited the proliferation and promoted death of DJ-1-overexpressed LNCaP while increasing LC3 transformation and LC3-puncta formation, but these results were reversed by the decrease of Beclin1 (by spautin-1). In contrast, when DJ-1 was silenced, the death of LNCaP, LC3 transformation, and LC3-puncta formation were inhibited by JNK inhibitor SP600125, which promoted cell proliferation. However, Bcl2 inhibition (by ABT737) reversed all the effects of SP600125. Our results suggested that DJ-1 in PCa cells could promote the growth of PCa through autophagy inhibition, and JNK-Bcl2-Beclin1 signaling played an important role in it. The study provided new insights into the role of DJ-1 in the development of PCa.

Propofol Attenuates Hypoxia/Reoxygenation-Induced Apoptosis and Autophagy in HK-2 Cells by Inhibiting JNK Activation

PURPOSE

The aim of this study was to investigate whether propofol could attenuate hypoxia/reoxygenation-induced apoptosis and autophagy in human renal proximal tubular cells (HK-2) by inhibiting JNK activation.

MATERIALS AND METHODS

HK-2 cells were treated with or without propofol or JNK inhibitor SP600125 for 1 hour and then subjected to 15 hours of hypoxia and 2 hours of reoxygenation (H/R). Cell viability and LDH release were measured with commercial kits. Cell apoptosis was evaluated by flow cytometry. The expressions of p-JNK, cleaved-caspase-3, Bcl-2, and autophagy markers LC3 and p62 were measured by Western blot or immunofluorescence.

RESULTS

HK-2 cells exposed to H/R insult showed higher cell injury (detected by increased LDH release and decreased cell viability), increased cell apoptosis index and expression of cleaved-caspase-3, a decrease in the expression of Bcl-2 accompanied by increased expression of p-JNK and LC3II, and a decrease in expression of p62. All of these alterations were attenuated by propofol treatment. Similar effects were provoked upon treatment with the JNK inhibitor SP600125. Moreover, the protective effects were more obvious with the combination of propofol and SP600125.

CONCLUSION

These results suggest that propofol could attenuate hypoxia/reoxygenation induced apoptosis and autophagy in HK-2 cells, probably through inhibiting JNK activation.

Anti-Apoptotic and Anti-Oxidant Proteins in Glioblastomas: Immunohistochemical Expression of Beclin and DJ-1 and Its Correlation with Prognosis

DJ-1 deglycase is a protein with anti-oxidative and anti-apoptotic properties and its role in oncogenesis is controversial. Indeed in primary breast cancer and non-small-cell lung carcinoma, its higher expression was shown in more aggressive tumors while in other neoplasms (e.g., pancreatic adenocarcinoma), higher expression was related to better prognosis. Beclin has a relevant role in autophagy and cellular death regulation, processes that are well known to be impaired in neoplastic cells. DJ-1 shows the ability to modulate signal transduction. It can modulate autophagy through many signaling pathways, a process that can mediate either cell survival or cell death depending on the circumstances. Previously, it has been suggested that the involvement of DJ-1 in autophagy regulation may play a role in tumorigenesis. The aim of our study was to investigate the link between DJ-1 and Beclin-1 in glioblastoma through the immunohistochemical expression of such proteins and to correlate the data obtained with prognosis. Protein expression was assessed by immunohistochemistry and the immunoscores were correlated with clinicopathologic parameters. Kaplan–Meier survival curves were generated. A statistically significant association between DJ-1 score and recurrence (p = 0.0189) and between the former and Isocitrate Dehydrogenase 1 (IDH1) mutation (p = 0.0072) was observed. Kaplan–Meier survival curve analysis revealed that a higher DJ-1 score was associated with longer overall survival (p = 0.0253, ĸ2 = 5.005). Furthermore, an unexpected direct correlation (p = 0.0424, r = 0.4009) between DJ-1 and Beclin score was evident. The most significant result of the present study was the evidence of high DJ-1 expression in IDH-mutant tumors and in cases with longer overall survival. This finding could aid, together with IDH1, in the identification of glioblastomas with better prognosis.

RNAi-mediated knockdown of DJ-1 leads to mitochondrial dysfunction via Akt/GSK-3ß and JNK signaling pathways in dopaminergic neuron-like cells

Deletions or some mutations in the gene encoding the multifunctional protein, DJ-1, have been considered to be linked with autosomal recessive early onset Parkinson's disease (PD). Current emerging evidence suggests that DJ-1 is involved in the protection against oxidative stress-induced mitochondrial damage. However, the exact molecular mechanisms underlying this are not completely clear. The aim of this study was to investigate the effects of DJ-1 on the Akt pathway, nuclear factor erythroid 2-related factor (Nrf2), and c-Jun N-terminal kinase (JNK) with regard to modulating mitochondrial function. Here we showed that knockdown of DJ-1 resulted in mitochondrial dysfunction, including a decrease in active mitochondrial mass, complex I deficits, and inhibition of cellular adenosine 5'-triphosphate (ATP) content in the dopaminergic neuron-like cells PC12 and SH-SY5Y. Additionally, loss of DJ-1 impaired Akt signaling, and reduced nuclear translocation of Nrf2, thereby inhibiting activity of Nrf2-regulated downstream antioxidant enzymes such as heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1. Moreover, DJ-1 knockdown also led to a significant increase in the mitochondrial reactive oxygen species, and then promoted the activation of JNK pathways. Furthermore, oxidative stress and mitochondrial dysfunction induced by knockdown of DJ-1 were blocked by a JNK inhibitor, which confirmed the important role of JNK activation in mitochondrial dysfunction. In conclusion, the present study indicates that DJ-1 knockdown leads to mitochondrial dysfunction in dopaminergic neuron-like cells, at least in part, through suppressing the Akt/GSK3β pathway and impairing the oxidative stress response, as well as through the subsequent increased JNK activation in dopaminergic neuron-like cells.

Protocatechuic acid-mediated DJ-1/PARK7 activation followed by PI3K/mTOR signaling pathway activation as a novel mechanism for protection against ketoprofen-induced oxidative damage in the gastrointestinal mucosa

Oxidative stress contributes to the progression of non-steroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) cell apoptosis. In our previous study, we reported that nuclear factor erythroid 2-related factor 2 (Nrf2) plays a protective role against ketoprofen-induced GI mucosal oxidative injury. Recent reports suggest that Nrf2 could exhibit antioxidative and antiapoptosis responses through up-regulation of DJ-1 (PARK7). In the current study, we proposed that induction of DJ-1 expression by protocatechuic acid (PCA) might provide a potential therapeutic approach for treating oxidative stress-associated GI ulcer diseases. The results indicated that PCA increased mRNA expression of glutathione peroxidase and heme oxygenase-1 through up-regulation of DJ-1 followed by Nrf2 translocation. Furthermore, PCA protected Int-407 cells against ketoprofen-induced oxidative stress by regulating the DJ-1, PI3K, and mTOR pathways. Pretreatment with PCA inhibited mitochondrial ROS generation, up-regulated the mitochondrial membrane potential, and down-regulated pro-apoptotic Bax as well as downstream caspase-8, caspase-9, and caspase-3 activity, and reversed impaired DJ-1 and anti-apoptotic Bcl-2 protein expression in Int-407 cells induced by ketoprofen. Similar to the in vitro results, SD rats treated with PCA before administration of ketoprofen exhibited decreased caspase-3 protein expression as well as oxidative damage, and impairment of the antioxidant system and DJ-1 protein expression in the GI mucosa were reversed. The administration of lansoprazole, a type of proton pump inhibitor (PPI), strongly inhibited ketoprofen-induced GI mucosal injuries via up-regulation of DJ-1, indicating that DJ-1 is essential for the dietary antioxidant- and PPI drug-mediated mechanism of ulcer therapy. These results suggest that DJ-1 could be a novel target for protection against ketoprofen-induced GI ulcers due to its antioxidant and anti-apoptosis characteristics.

Protective effects of Tat-DJ-1 protein against streptozotocin-induced diabetes in a mice model

A major feature of type 1 diabetes mellitus (T1DM) is hyperglycemia and dysfunction of pancreatic β-cells. In a previous study, we have shown that Tat-DJ-1 protein inhibits pancreatic RINm5F β-cell death caused by oxidative stress. In this study, we examined effects of Tat-DJ-1 protein on streptozotocin (STZ)-induced diabetic mice. Wild type (WT) Tat-DJ-1 protein transduced into pancreas where it markedly inhibited pancreatic β-cell destruction and regulated levels of serum parameters including insulin, alkaline phosphatase (ALP), and free fatty acid (FFA) secretion. In addition, transduced WT Tat-DJ-1 protein significantly inhibited the activation of NF-κB and MAPK (ERK and p38) expression as well as expression of COX-2 and iNOS in STZ exposed pancreas. In contrast, treatment with C106A mutant Tat-DJ-1 protein showed no protective effects. Collectively, our results indicate that WT Tat-DJ-1 protein can significantly ameliorate pancreatic tissues in STZ-induced diabetes in mice. [BMB Reports 2018; 51(7): 362-367].

Role of Mitogen Activated Protein Kinase Signaling in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by insufficient dopamine production due to the loss of 50% to 70% of dopaminergic neurons. A shortage of dopamine, which is predominantly produced by the dopaminergic neurons within the substantia nigra, causes clinical symptoms such as reduction of muscle mass, impaired body balance, akinesia, bradykinesia, tremors, postural instability, etc. Lastly, this can lead to a total loss of physical movement and death. Since no cure for PD has been developed up to now, researchers using cell cultures and animal models focus their work on searching for potential therapeutic targets in order to develop effective treatments. In recent years, genetic studies have prominently advocated for the role of improper protein phosphorylation caused by a dysfunction in kinases and/or phosphatases as an important player in progression and pathogenesis of PD. Thus, in this review, we focus on the role of selected MAP kinases such as JNKs, ERK1/2, and p38 MAP kinases in PD pathology.

Effect of Zishenpingchan granule prepared from Chinese medicinal substances on the c-Jun N-terminal protein kinase pathway in mice with Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

OBJECTIVE

To investigate the regulatory mechanism of the c-Jun N-terminal protein kinase (JNK) signaling pathway in substantia nigra (SN) dopaminergic neurons inflammation and apoptosis, and the neuroprotective effect of Zishenpingchan granules in mice with Parkinson's disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

METHODS

PD model mice were established by intraperitoneally injecting MPTP. Sixty mice were divided into a model group, Traditional Chinese Medicine (TCM) group and control group. The mice of the TCM group were administered Zishenpingchan granules 7 days before PD induction. Seven days after PD induction, we examined locomotor activity, and performed the rotarod test and swimming test, to evaluate limb movement function. Furthermore, we used immunohistochemistry and western blotting to examine the expression of tyrosine hydroxylase (TH), cyclooxygenase-2 (Cox-2), caspase-3 and p-JNK. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method was used to examine neuron apoptosis in the SN.

RESULTS

Compared with the control group, the mean score of locomotor activity, rotarod test and swimming test was significantly lower in the model group (P < 0.05); the TH-positive neuron expression was significantly decreased in the SN pars compacta (SNpc); the protein expression levels of Cox-2, caspase-3 and p-JNK was obviously increased; and the number of TUNEL-positive neurons in the SN was increased (P < 0.01). Compared with the model group, the mean score of neurobehavioral tests in the TCM group was obviously higher, the loss of TH-positive neurons ignificantly decreased, the protein expression levels of Cox-2, caspase-3 and p-JNK obviously decreased, and the number of TUNEL- positive neurons in the SN clearly decreased (P < 0.01).

CONCLUSION

The JNK pathway plays an important role in the regulation of inflammation and apoptosis in nigral cells in PD mice. TCM can suppress the over-activation of the JNK pathway in the SN, and alleviate the inflammatory response in nigral cells and dopaminergic neuron apoptosis in PD mice.

Overexpression of DJ-1 correlates with aggressive clinicopathological characteristics and poor prognosis in malignant tumors: a meta-analysis

Purpose

A number of studies have investigated the role of DJ-1 in the development and progression of malignant tumors. This meta-analysis aims to systematically estimate the rela-tionship between the expression level of DJ-1 and the malignant biological behaviors of tumors and to assess the clinical significances of DJ-1 in the prognosis and diagnosis of cancer.

Materials and methods

We searched PubMed, Web of Science, China National Knowledge Infrastructure and Wanfang databases from inception to December 1, 2017. Pooled odds ratio (OR) and hazard ratio (HR) with their 95% confidence interval and the diagnostic value of DJ-1 were calculated.

Results

Fourteen eligible studies with a total of 1,947 subjects were enrolled in our meta-analysis. The results showed that DJ-1 was overexpressed in cancer patients compared with noncancer patients (OR = 30.72), and elevated expression of DJ-1 was demonstrated to be closely associated with high tumor-node-metastasis stage (OR = 5.52), poor differentiated degree (OR = 2.46), positive lymph node metastasis (OR = 4.12) and worse overall survival (HR = 2.23). In addition, the combined sensitivity and specificity for DJ-1 to discern malignant tumors were 0.73 and 0.93, respectively. The diagnostic OR was 34.87, and the area under the summary receiver operating characteristic curve was 0.88.

Conclusion

This meta-analysis demonstrated that DJ-1 was an important biomarker in tumor assessment and prognosis prediction.

Inhibition of excessive autophagy and mitophagy mediates neuroprotective effects of URB597 against chronic cerebral hypoperfusion

URB597 (URB) has therapeutic potential for treating chronic cerebral hypoperfusion (CCH)-induced neuronal death. The present study investigated the protective effects of URB on autopahgy and mitophagy in a CCH model as well as the underlying mechanisms. The ultrastructural changes were examined by electron microscopy. The mitochondrial membrane potential was assessed by immunofluorescence. The expressions of autophagy-related proteins (beclin-1, p62, and LC3), lysosome-related proteins (CTSD and LAMP1), and mitophagy-related proteins (BNIP3, cyt C and parkin) were evaluated by western blotting, and the interaction of beclin-1 and Bcl-2 were determined by immunoprecipitation. CCH significantly decreased the protein expression of p62, CTSD, and LAMP1 and increased the protein expression of beclin-1, parkin, and BNIP3, the LC3-II to LC3-I ratio, and the release of cyt C from mitochondria to cytoplasm. Furthermore, CCH induced the accumulation of ubiquitinated proteins in PSDs. However, URB significantly reversed these results. Besides, URB significantly inhibited the beclin-1 from beclin-1/Bcl-2 complex to whole-cell lysates. The above results indicate that URB could inhibit impaired autophagy degradation and the disruption of beclin-1/Bcl-2 complex and subsequently cut off BNIP3-cyt C- and parkin-required mitophagy, finally preventing the abnormal excessive autophagy and mitophagy. These findings provide new insights that URB is a promising agent for therapeutic management of CCH.

Familial Parkinson's Disease-Associated L166P Mutant DJ-1 is Cleaved by Mitochondrial Serine Protease Omi/HtrA2

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Mutations in the DJ-1, including L166P, are responsible for recessive early-onset PD. Many lines of evidence have shown that L166P is not only a loss-of-function mutant, but also a pro-apoptotic-like protein that results in mitochondrial dysfunction. L166P has been reported to be unstable and to mislocalize to mitochondria. However, the mechanisms underlying the instability of L166P compared to wild-type DJ-1 remain largely unknown. Here, we showed that Omi/HtrA2, a mitochondrial serine protease that has also been linked to the pathogenesis of PD, contributed to L166P instability. Omi directly interacted with and cleaved L166P in mitochondria to decrease the L166P level. However, Omi did not bind and cleave wild-type DJ-1. Moreover, Omi cleaved L166P at both serine residues 3 and 121, while L166P-induced cell death under H₂O₂ treatment was alleviated by over-expression of Omi. Our data reveal a bridge between DJ-1 and Omi, two PD-associated genetic factors, which contributes to our understanding of the pathogenesis of PD.

Cytoprotective mechanisms of DJ-1 against oxidative stress through modulating ERK1/2 and ASK1 signal transduction

DJ-1 is a highly conserved multifunctional protein linked to both neurodegeneration and neoplasia. Among its various activities is an antioxidant property leading to cytoprotection under oxidative stress conditions. This is associated with the ability to modulate signal transduction events that determine how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy in order to adapt to environmental stimuli and stresses. Alterations in DJ-1 expression or function can disrupt homeostatic signaling networks and initiate cascades that play a role in the pathogenesis of conditions such as Parkinson's disease and cancer.

DJ-1 plays a major role in various signaling pathways. Related to its anti-oxidant properties, it mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation. Here, we review the ways through which DJ-1 regulates these pathways, focusing on how its regulation of signal transduction contributes to cellular homeostasis and the pathologic states that result from their dysregulation.

Progression of pathology in PINK1-deficient mouse brain from splicing via ubiquitination, ER stress, and mitophagy changes to neuroinflammation

Background

PINK1 deficiency causes the autosomal recessive PARK6 variant of Parkinson’s disease. PINK1 activates ubiquitin by phosphorylation and cooperates with the downstream ubiquitin ligase PARKIN, to exert quality control and control autophagic degradation of mitochondria and of misfolded proteins in all cell types.

Methods

Global transcriptome profiling of mouse brain and neuron cultures were assessed in protein-protein interaction diagrams and by pathway enrichment algorithms. Validation by quantitative reverse transcriptase polymerase chain reaction and immunoblots was performed, including human neuroblastoma cells and patient primary skin fibroblasts.

Results

In a first approach, we documented Pink1-deleted mice across the lifespan regarding brain mRNAs. The expression changes were always subtle, consistently affecting “intracellular membrane-bounded organelles”. Significant anomalies involved about 250 factors at age 6 weeks, 1300 at 6 months, and more than 3500 at age 18 months in the cerebellar tissue, including Srsf10, Ube3a, Mapk8, Creb3, and Nfkbia. Initially, mildly significant pathway enrichment for the spliceosome was apparent. Later, highly significant networks of ubiquitin-mediated proteolysis and endoplasmic reticulum protein processing occurred. Finally, an enrichment of neuroinflammation factors appeared, together with profiles of bacterial invasion and MAPK signaling changes—while mitophagy had minor significance. Immunohistochemistry showed pronounced cellular response of Iba1-positive microglia and GFAP-positive astrocytes; brain lipidomics observed increases of ceramides as neuroinflammatory signs at old age.

In a second approach, we assessed PINK1 deficiency in the presence of a stressor. Marked dysregulations of microbial defense factors Ifit3 and Rsad2 were consistently observed upon five analyses: (1) Pink1^−/− primary neurons in the first weeks after brain dissociation, (2) aged Pink1^−/− midbrain with transgenic A53T-alpha-synuclein overexpression, (3) human neuroblastoma cells with PINK1-knockdown and murine Pink1^−/− embryonal fibroblasts undergoing acute starvation, (4) triggering mitophagy in these cells with trifluoromethoxy carbonylcyanide phenylhydrazone (FCCP), and (5) subjecting them to pathogenic RNA-analogue poly(I:C). The stress regulation of MAVS, RSAD2, DDX58, IFIT3, IFIT1, and LRRK2 was PINK1 dependent. Dysregulation of some innate immunity genes was also found in skin fibroblast cells from PARK6 patients.

Conclusions

Thus, an individual biomarker with expression correlating to progression was not identified. Instead, more advanced disease stages involved additional pathways. Hence, our results identify PINK1 deficiency as an early modulator of innate immunity in neurons, which precedes late stages of neuroinflammation during alpha-synuclein spreading.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0928-0) contains supplementary material, which is available to authorized users.

Selenium Deficiency Induces Autophagy in Immune Organs of Chickens

The aim of the present study was to investigate the effects of selenium (Se) deficiency on autophagy-related genes and on ultrastructural changes in the spleen, bursa of Fabricius, and thymus of chickens. The Se deficiency group was fed a basal diet containing Se at 0.033 mg/kg and the control group was fed the same basal diet containing Se at 0.15 mg/kg. The messenger RNA (mRNA) levels of the autophagy genes microtubule-associated protein 1 light chain 3 (LC3)-I, LC3-II, Beclin 1, dynein, autophagy associated gene 5 (ATG5), and target of rapamycin complex 1 (TORC1) were assessed using real-time qPCR. The protein levels of LC3-II, Beclin 1, and dynein were investigated using western blot analysis. Furthermore, the ultrastructure was observed using an electron microscope. The results indicated that spleen mRNA levels of LC3-I, LC3-II, Beclin 1, dynein, ATG5, and TORC1 and the protein levels of LC3-II, Beclin 1, and dynein were increased in the Se deficiency group compared with the control group. In the bursa of Fabricius, the mRNA levels of LC3-I, LC3-II, Beclin 1, dynein, ATG5, and TORC1 and the protein levels of Beclin 1 and dynein were increased; furthermore, the protein level of LC3-II was decreased in the Se deficiency group compared to the control group. In the thymus, the mRNA levels of LC3-I, Beclin 1, and ATG5 increased; the levels of LC3-II, dynein, and TORC1 were decreased; the protein level of Beclin 1 increased; and the levels of LC3-II and dynein decreased in the Se deficiency group compared to those in the control group. Further cellular morphological changes, such as autophagy vacuoles, autolysosomes, and lysosomal degradation, were observed in the spleen, bursa of Fabricius, and thymus of the Se-deficiency group. In summary, Se deficiency caused changes in autophagy-related genes, which increased the autophagic process and also caused structural damages to the immune organs of chickens.

Trumping neurodegeneration: Targeting common pathways regulated by autosomal recessive Parkinson's disease genes

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by the progressive loss of dopaminergic (DA) neurons. Most PD cases are sporadic; however, rare familial forms have been identified. Autosomal recessive PD (ARPD) results from mutations in Parkin, PINK1, DJ-1, and ATP13A2, while rare, atypical juvenile ARPD result from mutations in FBXO7, DNAJC6, SYNJ1, and PLA2G6. Studying these genes and their function has revealed mitochondrial quality control, protein degradation processes, and oxidative stress responses as common pathways underlying PD pathogenesis. Understanding how aberrancy in these common processes leads to neurodegeneration has provided the field with numerous targets that may be therapeutically relevant to the development of disease-modifying treatments.

Regulation of Signal Transduction by DJ-1

The ability of DJ-1 to modulate signal transduction has significant effects on how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy to adapt to changing environmental stimuli and stresses. Perturbations of DJ-1 levels or function can disrupt the equilibrium of homeostatic signaling networks and set off cascades that play a role in the pathogenesis of conditions such as cancer and Parkinson's disease.DJ-1 plays a major role in various pathways. It mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and the phosphatidylinositol-3-kinase (PI3K)/Akt pathway. It attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation as well as by inhibiting mitogen-activated protein kinase kinase kinase 1 (MEKK1/MAP3K1) activation of downstream apoptotic cascades. It also modulates autophagy through the ERK, Akt, or the JNK/Beclin1 pathways. In addition, DJ-1 regulates the transcription of genes essential for male reproductive function, such as spermatogenesis, by relaying nuclear receptor androgen receptor (AR) signaling. In this chapter, we summarize the ways that DJ-1 regulates these pathways, focusing on how its role in signal transduction contributes to cellular homeostasis and the pathologic states that result from dysregulation.

Dysregulation of autophagy and mitochondrial function in Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Increasing evidence supports that dysregulation of autophagy and mitochondrial function are closely related with PD pathogenesis. In this review, we briefly summarized autophagy pathway, which consists of macroautophagy, microautophagy and chaperone-mediated autophagy (CMA). Then, we discussed the involvement of mitochondrial dysfunction in PD pathogenesis. We specifically reviewed the recent developments in the relationship among several PD related genes, autophagy and mitochondrial dysfunction, followed by the therapeutic implications of these pathways. In conclusion, we propose that autophagy activity and mitochondrial homeostasis are of high importance in the pathogenesis of PD. Better understanding of these pathways can shed light on the novel therapeutic methods for PD prevention and amelioration.

Deconvoluting the complexity of autophagy and Parkinson's disease for potential therapeutic purpose

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the preferential death of dopaminergic neurons. In the past two decades, great progress has been made toward understanding the pathogenesis of PD; however, its precise pathogenesis still remains unclear. Recently, accumulating evidence has suggested that macroautophagy (herein referred to as autophagy) is tightly linked to PD. Dysregulation of autophagic pathways has been observed in the brains of PD patients and in animal models of PD. More importantly, a number of PD-associated proteins, such as α-synuclein, LRRK2, Parkin and PINK1 have been further revealed to be involved in autophagy. Thus, it is now acknowledged that constitutive autophagy is essential for neuronal survival and that dysregulation of autophagy leads to PD. In this review, we focus on summarizing the relationships amongst PD-associated proteins, autophagy and PD. Moreover, we also demonstrate some autophagy-modulating compounds and autophagic microRNAs in PD models, which may provide better promising strategies for potential PD therapy.

Schizosaccharomyces pombe Homologs of Human DJ-1 Are Stationary Phase-Associated Proteins That Are Involved in Autophagy and Oxidative Stress Resistance

The Parkinson′s disease protein DJ-1 is involved in various cellular functions including detoxification of dicarbonyl compounds, autophagy and oxidative stress response. DJ-1 homologs are widely found in both prokaryotes and eukaryotes, constituting a superfamily of proteins that appear to be involved in stress response. Schizosaccharomyces pombe contains six DJ-1 homologs, designated Hsp3101-Hsp3105 and Sdj1 (previously named SpDJ-1). Here we show that deletion of any one of these six genes somehow affects autophagy during prolonged stationary phase. Furthermore, deletions of each of these DJ-1 homologs result in reduced stationary phase survival. Deletion of sdj1 also increases the sensitivity of stationary-phase cells to oxidative stress induced by hydrogen peroxide (H₂O₂) whereas overexpression of sdj1 has the opposite effect. Consistent with their role in stationary phase, expression of hsp3101, hsp3102, hsp3105 and sdj1, and to a lesser extent hsp3103 and hsp3104, is increased in stationary phase. The induction of hsp3101, hsp3102, hsp3105 and sdj1 involves the Sty1-regulated transcription factor Atf1 but not the transcription factor Pap1. Our results firmly establish that S. pombe homologs of DJ-1 are stationary-phase associated proteins and are likely involved in autophagy and antioxidant defense in stationary phase of S. pombe cells.

The association between Parkinson's disease and melanoma: a systematic review and meta-analysis

Objective

To assess the association between Parkinson’s disease (PD) and melanoma via systematic review and meta-analysis.

Methods

Comprehensive search in PubMed, Web of Science, Embase and four China databases (SinoMed, WanFang data, CNKI and VIP database) of epidemiologic evidences on PD and melanoma published before April 30, 2015. Studies which reported risk estimates of melanoma among PD patients or risk estimates of PD in patients with melanoma were included. Pooled odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated by random-effects models. Heterogeneity across studies was assessed using Cochran Q and I² statistics. Subgroup analyses and sensitivity analyses were conducted to evaluate sources of heterogeneity. Subgroup analyses were done according to temporal relationship, geographic region and gender respectively. We assessed publication bias using the Begg and Egger test. In addition, study appraisal was done using a scale for observational studies to ensure the quality of evidence.

Results

We identified 24 eligible studies on PD and melanoma with a total number of 292,275 PD patients: the pooled OR was 1.83 (95 % CI 1.46–2.30) overall, subgroup analyses by temporal relationship showed that risk of melanoma after PD diagnosis was significantly higher (OR 2.43, 95 % CI 1.77–3.32), but not before the diagnosis of PD (OR 1.09, 95 % CI 0.78–1.54). Subgroup analysis by geographic region showed that increased risk of melanoma in PD was found both in Europe (OR 1.44, 95 % CI 1.22–1.70) and in North America (OR 2.64, 95 % CI 1.63–4.28). Gender-specific subgroup analyses did not show difference between men (OR 1.64, 95 % CI 1.27–2.13) and women (OR 1.38, 95 % CI 1.04–1.82) in the risk of melanoma. In addition, we found the risk of non-melanoma skin cancers in PD was slightly higher (OR 1.20, 95 % CI 1.11–1.29) than general population. It was impossible to evaluate the association between PD and melanoma according to use of levodopa or gene polymorphism via meta-analysis since few observational or cohort studies have focused on it.

Conclusions

An association between PD and melanoma was confirmed. Most of the evidences were of high quality, and the conclusion was robust. Further research is needed to explore the mechanisms underlying this relationship.

Electronic supplementary material

The online version of this article (doi:10.1186/s40035-015-0044-y) contains supplementary material, which is available to authorized users.

Parkin represses 6-hydroxydopamine-induced apoptosis via stabilizing scaffold protein p62 in PC12 cells

AIM

Parkin has been shown to exert protective effects against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in different models of Parkinson disease. In the present study we investigated the molecular mechanisms underlying the neuroprotective action of parkin in vitro.

METHODS

HEK293, HeLa and PC12 cells were transfected with parkin, parkin mutants, p62 or si-p62. Protein expression and ubiquitination were assessed using immunoblot analysis. Immunoprecipitation assay was performed to identify the interaction between parkin and scaffold protein p62. PC12 and SH-SY5Y cells were treated with 6-OHDA (200 μmol/L), and cell apoptosis was detected using PI and Hoechst staining.

RESULTS

In HEK293 cells co-transfected with parkin and p62, parkin was co-immunoprecipitated with p62, and parkin overexpression increased p62 protein levels. In parkin-deficient HeLa cells, transfection with wild-type pakin, but not with ligase activity-deficient pakin mutants, significantly increased p62 levels, suggesting that parkin stabilized p62 through its E3 ligase activity. Transfection with parkin or p62 significantly repressed ERK1/2 phosphorylation in HeLa cells, but transfection with parkin did not repress ERK1/2 phosphorylation in p62-knockdown HeLa cells, suggesting that p62 was involved in parkin-induced inhibition on ERK1/2 phosphorylation. Overexpression of parkin or p62 significantly repressed 6-OHDA-induced ERK1/2 phosphorylation in PC12 cells, and parkin overexpression inhibited 6-OHDA-induced apoptosis in PC12 and SH-SY5Y cells.

CONCLUSION

Parkin protects PC12 cells against 6-OHDA-induced apoptosis via ubiquitinating and stabilizing scaffold protein p62, and repressing ERK1/2 activation.

Folliculin, a tumor suppressor associated with Birt-Hogg-Dubé (BHD) syndrome, is a novel modifier of TDP-43 cytoplasmic translocation and aggregation

TDP-43 was identified as the major component of ubiquitin and autophagosome-positive cytoplasmic inclusions in neurons in the large majority of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD) patients. It has been shown that a loss of nuclear TDP-43 in combination with enhanced cytoplasmic mislocalization of TDP-43, which is associated with accumulation of TDP-43 aggregates in the cytosol, is an early and key event in TDP-43-mediated neurodegeneration. However, the mechanism underlying TDP-43 nucleocytoplasmic shuttling is still not clear. Here, we show that the tumor suppressor folliculin (FLCN) is a novel positive regulator of TDP-43 cytoplasmic translocation. FLCN directly interacts with TDP-43. The amino acids 202-299 of FLCN and RNA-recognition motif domains of TDP-43 are necessary for their interaction. In addition, both exogenous and endogenous FLCNs are required for TDP-43 cytoplasmic accumulation, protein aggregation and stress granule formation. Overall, our study suggests that FLCN may play an important role in the regulation of TDP-43 nucleocytoplasmic shuttling and TDP-43-mediated proteinopathy.

MiR-26a enhances autophagy to protect against ethanol-induced acute liver injury

Abstract

Autophagy is a process for the turnover of intracellular organelles and molecules during stress responses. microRNAs (miRNAs) are small, non-coding endogenous RNAs that may regulate almost every cellular process. However, the roles of miRNAs in autophagy are still poorly understood. In this study, we show that miR-26a enhances autophagy in both culture cells and the mouse liver. Hepatic overexpression of miR-26a in mice alleviated ethanol-induced hepatic steatosis and liver injury. Overexpression of miR-26a increased the expression of the autophagy mediator Beclin-1, which is regulated by mitogen-activated protein kinases (MAPKs). We identified DUSP4 and DUSP5, two MAPKs inhibitors, as direct targets of miR-26a. We further demonstrated that miR-26a targeted the 3′-UTRs of several other negative regulators of autophagy. Our results thus identify a novel miRNA-mediated mechanism that enhances cytoprotective autophagy in the liver.

Key messages

• miR-26a enhances autophagy in liver cells.

• Hepatic overexpression of miR-26a in mice alleviates ethanol-induced liver injury.

• Overexpression of miR-26a increases the expression of autophagy mediator Beclin-1.

• DUSP4 and DUSP5, two MAPKs inhibitors, were identified as direct targets of miR-26a.

Electronic supplementary material

The online version of this article (doi:10.1007/s00109-015-1282-2) contains supplementary material, which is available to authorized users.

DJ-1 as a human oncogene and potential therapeutic target

DJ-1 is a cancer- and Parkinson's disease-associated protein that participates in different intracellular signaling pathways to protect cells from toxic stresses. DJ-1 expression, oxidation, localization, and phosphorylation are often altered in human tumors, and DJ-1 has been implicated in various aspects of transformation, including uncontrolled proliferation, invasion, metastasis, and resistance to chemotherapy and apoptosis. Despite the strong relationship between DJ-1 and cancer, which made it a particularly attractive therapeutic target for cancer treatment, the detailed mechanisms of how this oncogene coordinates altered signaling with cell survival remains elusive. In this commentary, we discuss the role of DJ-1 in transformation, highlight some of the significant aspects of and prospects for therapeutically targeting the DJ-1 signaling in cancer, and describe what the future may hold.

A new split-GFP-based probe reveals DJ-1 translocation into the mitochondrial matrix to sustain ATP synthesis upon nutrient deprivation

The Parkinson's disease-related protein DJ-1 has a role in the protection against oxidative stress and maintenance of mitochondria structure. Whether this action depends on its localization and activity within the mitochondria is not clear. Here we develop an approach to resolve intra-mitochondrial distribution of DJ-1 and monitor its translocation under specific conditions. By a new split-green fluorescent protein (GFP)-based tool, we can observe that a small DJ-1 fraction is located within the mitochondrial matrix and that it consistently increases upon nutrient depletion. We also find that the targeting of DJ-1 to the mitochondrial matrix enhances mitochondrial and cytosolic adenosine triphosphate levels. Intriguingly, DJ-1 pathogenic mutants fail to improve bioenergetics and translocate within the mitochondrial matrix, suggesting that the DJ-1 protective role requires both these actions. By this new split-GFP-based tool, we can resolve mitochondrial compartmentalization of proteins which are not constitutively resident in mitochondria but translocate to them in response to specific stimuli.

The oxidation states of DJ-1 dictate the cell fate in response to oxidative stress triggered by 4-hpr: autophagy or apoptosis?

AIM

Chemotherapy-induced reactive oxygen species (ROS) not only contribute to apoptosis, but also trigger autophagy. Since autophagy is reported to protect cancer cells from apoptosis, this weakens the therapeutic effect of chemotherapy. This study aimed at identifying the key molecules that determine the cellular response to ROS and, therefore, provide better strategies to increase chemotherapeutic efficiency.

RESULTS

Increasing concentrations of N-(4-hydroxyphenyl) retinamide (4-HPR)-treatment pushed autophagy down to apoptosis in a dose-dependent manner, and 4-HPR-induced ROS contribute to this process. Since we found that ASK1-regulated JNK1 and p38 are responsible for 4-HPR-induced autophagy and apoptosis, respectively, we further utilized co-immunoprecipitation followed by liquid chromatography-tandem mass spectrometry analysis to identify proteins that specifically bind to ASK1 under different oxidative states. Of note, DJ-1, a crucial antioxidant protein, was identified. Interestingly, DJ-1 functions as a redox sensor that senses ROS levels and determines the cellular response to 4-HPR: Under mild oxidative stress, moderate oxidation of DJ-1 is recruited to inhibit the activity of ASK1 and maintain cell viability by activating autophagy; under a lethal level of oxidative stress, excessive oxidized DJ-1 dissociates from ASK1 and activates it, thereby initiating p38 activation and enabling the cells to commit to apoptosis. Moreover, the depletion of DJ-1 increases the sensitivity of tumor cells to 4-HPR both in vitro and in vivo.

INNOVATION

Our results reveal that the different oxidation states of DJ-1 function as a cellular redox sensor of ROS caused by 4-HPR and determine the cell fate of autophagy or apoptosis. Moreover, the results suggest that DJ-1 might be a potent therapeutic target for cancer treatment.

CONCLUSION

ROS-mediated changes in the oxidation state of DJ-1 are involved in 4-HPR's effect on pushing autophagy down to apoptosis. Consequently, this change mediates ASK1 activation by regulating DJ-1-ASK1 complex formation and determines the cell fate of autophagy or apoptosis.

p62/sequestosome 1 regulates aggresome formation of pathogenic ataxin-3 with expanded polyglutamine

The cellular protein quality control system in association with aggresome formation contributes to protecting cells against aggregation-prone protein-induced toxicity. p62/Sequestosome 1 (p62) is a multifunctional protein which plays an important role in protein degradation and aggregation. Although poly-ubiquitination is usually required for p62-mediated protein degradation and aggresome formation, several p62 substrates are processed to form aggregate in an ubiquitination-independent manner. In this study we demonstrate that p62 directly interacts with pathogenic Machado Joseph Disease (MJD)-associated protein ataxin-3 with polyglutamine (polyQ) expansion. Moreover, p62 could regulate the aggresome formation of pathogenic ataxin-3 and protect cells against pathogenic ataxin-3-induced cell death.

Defective autophagy in Parkinson's disease: lessons from genetics

Parkinson's disease (PD) is the most prevalent neurodegenerative movement disorder. Genetic studies over the past two decades have greatly advanced our understanding of the etiological basis of PD and elucidated pathways leading to neuronal degeneration. Recent studies have suggested that abnormal autophagy, a well conserved homeostatic process for protein and organelle turnover, may contribute to neurodegeneration in PD. Moreover, many of the proteins related to both autosomal dominant and autosomal recessive PD, such as α-synuclein, PINK1, Parkin, LRRK2, DJ-1, GBA, and ATPA13A2, are also involved in the regulation of autophagy. We propose that reduced autophagy enhances the accumulation of α-synuclein, other pathogenic proteins, and dysfunctional mitochondria in PD, leading to oxidative stress and neuronal death.