The role of ubiquitin linkages on α-synuclein induced-toxicity in aDrosophilamodel of Parkinson’s disease

Novel Genome-Engineered H Alleles Differentially Affect Lateral Inhibition and Cell Dichotomy Processes during Bristle Organ Development

Hairless (H) encodes the major antagonist in the Notch signaling pathway, which governs cellular differentiation of various tissues in Drosophila. By binding to the Notch signal transducer Suppressor of Hairless (Su(H)), H assembles repressor complexes onto Notch target genes. Using genome engineering, three new H alleles, HFA, HLLAA and HWA were generated and a phenotypic series was established by several parameters, reflecting the residual H-Su(H) binding capacity. Occasionally, homozygous HWA flies develop to adulthood. They were compared with the likewise semi-viable HNN allele affecting H-Su(H) nuclear entry. The H homozygotes were short-lived, sterile and flightless, yet showed largely normal expression of several mitochondrial genes. Typical for H mutants, both HWA and HNN homozygous alleles displayed strong defects in wing venation and mechano-sensory bristle development. Strikingly, however, HWA displayed only a loss of bristles, whereas bristle organs of HNN flies showed a complete shaft-to-socket transformation. Apparently, the impact of HWA is restricted to lateral inhibition, whereas that of HNN also affects the respective cell type specification. Notably, reduction in Su(H) gene dosage only suppressed the HNN bristle phenotype, but amplified that of HWA. We interpret these differences as to the role of H regarding Su(H) stability and availability.

Parkinson's disease neurons exhibit alterations in mitochondrial quality control proteins

Mitochondrial dysfunction has been suggested to contribute to Parkinson's disease pathogenesis, though an understanding of the extent or exact mechanism of this contribution remains elusive. This has been complicated by challenging nature of pathway-based analysis and an inability simultaneously study multiple related proteins within human brain tissue. We used imaging mass cytometry (IMC) to overcome these challenges, measuring multiple protein targets, whilst retaining the spatial relationship between targets in post-mortem midbrain sections. We used IMC to simultaneously interrogate subunits of the mitochondrial oxidative phosphorylation complexes, and several key signalling pathways important for mitochondrial homoeostasis, in a large cohort of PD patient and control cases. We revealed a generalised and synergistic reduction in mitochondrial quality control proteins in dopaminergic neurons from Parkinson's patients. Further, protein-protein abundance relationships appeared significantly different between PD and disease control tissue. Our data showed a significant reduction in the abundance of PINK1, Parkin and phosphorylated ubiquitinSer65, integral to the mitophagy machinery; two mitochondrial chaperones, HSP60 and PHB1; and regulators of mitochondrial protein synthesis and the unfolded protein response, SIRT3 and TFAM. Further, SIRT3 and PINK1 did not show an adaptive response to an ATP synthase defect in the Parkinson's neurons. We also observed intraneuronal aggregates of phosphorylated ubiquitinSer65, alongside increased abundance of mitochondrial proteases, LONP1 and HTRA2, within the Parkinson's neurons with Lewy body pathology, compared to those without. Taken together, these findings suggest an inability to turnover mitochondria and maintain mitochondrial proteostasis in Parkinson's neurons. This may exacerbate the impact of oxidative phosphorylation defects and ageing related oxidative stress, leading to neuronal degeneration. Our data also suggest that that Lewy pathology may affect mitochondrial quality control regulation through the disturbance of mitophagy and intramitochondrial proteostasis.

Inhibition of Protein Aggregation and Endoplasmic Reticulum Stress as a Targeted Therapy for α-Synucleinopathy

α-synuclein (α-syn) is an intrinsically disordered protein abundant in the central nervous system. Physiologically, the protein regulates vesicle trafficking and neurotransmitter release in the presynaptic terminals. Pathologies related to misfolding and aggregation of α-syn are referred to as α-synucleinopathies, and they constitute a frequent cause of neurodegeneration. The most common α-synucleinopathy, Parkinson's disease (PD), is caused by abnormal accumulation of α-syn in the dopaminergic neurons of the midbrain. This results in protein overload, activation of endoplasmic reticulum (ER) stress, and, ultimately, neural cell apoptosis and neurodegeneration. To date, the available treatment options for PD are only symptomatic and rely on dopamine replacement therapy or palliative surgery. As the prevalence of PD has skyrocketed in recent years, there is a pending issue for development of new disease-modifying strategies. These include anti-aggregative agents that target α-syn directly (gene therapy, small molecules and immunization), indirectly (modulators of ER stress, oxidative stress and clearance pathways) or combine both actions (natural compounds). Herein, we provide an overview on the characteristic features of the structure and pathogenic mechanisms of α-syn that could be targeted with novel molecular-based therapies.

Prion therapeutics: Lessons from the past

Prion diseases are a group of incurable zoonotic neurodegenerative diseases (NDDs) in humans and other animals caused by the prion proteins. The abnormal folding and aggregation of the soluble cellular prion proteins (PrPC) into scrapie isoform (PrPSc) in the Central nervous system (CNS) resulted in brain damage and other neurological symptoms. Different therapeutic approaches, including stalling PrPC to PrPSc conversion, increasing PrPSc removal, and PrPC stabilization, for which a spectrum of compounds, ranging from organic compounds to antibodies, have been explored. Additionally, a non-PrP targeted drug strategy using serpin inhibitors has been discussed. Despite numerous scaffolds being screened for anti-prion activity in vitro, only a few were effective in vivo and unfortunately, almost none of them proved effective in the clinical studies, most likely due to toxicity and lack of permeability. Recently, encouraging results from a prion-protein monoclonal antibody, PRN100, were presented in the first human trial on CJD patients, which gives a hope for better future for the discovery of other new molecules to treat prion diseases. In this comprehensive review, we have re-visited the history and discussed various classes of anti-prion agents, their structure, mode of action, and toxicity. Understanding pathogenesis would be vital for developing future treatments for prion diseases. Based on the outcomes of existing therapies, new anti-prion agents could be identified/synthesized/designed with reduced toxicity and increased bioavailability, which could probably be effective in treating prion diseases.

Proteolysis of γ-tubulin small complex proteins is mediated by the ubiquitin-proteasome system

Microtubule nucleation is mainly mediated by the γ-tubulin ring complex (γTuRC), whose core components are γ-tubulin and γ-tubulin complex proteins GCP2-6. A substantial fraction of γ-tubulin also exists with GCP2 and GCP3 in a tetramer called the γ-tubulin small complex (γTuSC). To date, the mechanisms underlying the turnover of γ-tubulin and GCPs have remained unclear. Here, we show that γ-tubulin, GCP2, and GCP3 are proteolyzed by the ubiquitin-proteasome system, and we identify cullin 1, cullin 4A, and cullin 4B as the E3 ligases that mediate the ubiquitination and, consequently, the degradation of γ-tubulin. Notably, we found that γTuSC disassembly promotes the degradation of γ-tubulin, GCP2, and GCP3, which indicates a role for γTuSCs in the stabilization of its components.

Ameliorative Role of Nutraceuticals on Neurodegenerative Diseases Using the Drosophila melanogaster as a Discovery Model to Define Bioefficacy

Neurodegeneration is the destruction of neurons, and once the neurons degenerate they can't revive. This is one of the most concerned health conditions among aged population, more than ∼70% of the elderly people are suffering from neurodegeneration. Among all of the neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD) and Poly-glutamine disease (Poly-Q) are the major one and affecting most of the people around the world and posing excessive burden on the society. In order to understand this disease in non-human animal models it is pertinent to examine in model organism and various animal model are being used for such diseases like rat, mice and non-vertebrate model like Drosophila. Drosophila melanogaster is one of the best animal proven by several eminent scientist and had received several Nobel prizes for uncovering mechanism of human related genes and highly efficient model for studying neurodegenerative diseases due to its great affinity with human disease-related genes. Another factor is also employed to act as therapeutic or preventive method that is nutraceuticals. Nutraceuticals are functional natural compounds with antioxidant properties and had extensively showed the neuroprotective effect in different organisms. These nutraceuticals having antioxidant properties act through scavenging free radicals or by increasing endogenous cellular antioxidant defense molecules. For the best benefit, we are trying to utilize these nutraceuticals, which will have no or negligible side effects. In this review, we are dealing with various types of such nutraceuticals which have potent value in the prevention and curing of the diseases related to neurodegeneration.HighlightsNeurodegeneration is the silently progressing disease which shows its symptoms when it is well rooted.Many chemical drugs (almost all) have only symptomatic relief with side effects.Potent mechanism of neurodegeneration and improvement effect by nutraceuticals is proposed.Based on the Indian Cuisine scientists are trying to find the medicine from the food or food components having antioxidant properties.The best model to study the neurodegenerative diseases is Drosophila melanogaster.Many nutraceuticals having antioxidant properties have been studied and attenuated various diseases are discussed.

Xanthohumol prolongs lifespan and decreases stress-induced mortality in Drosophila melanogaster

Aging is a significant risk factor that links to the genesis of human diseases. The capacity to scavenge free radicals and adapt to various stresses is essential for expanding living organisms' lifespan. The evidences on the promotion of longevity by dietary supplementation are growing. Drosophila or fruit fly is one of the most effective models for the evaluation of anti-aging compounds. Xanthohumol (XN) is a potential bioactive substance for the prevention and treatment of many diseases. The previous studies have reported its potent activities as antioxidant, anticancer, anti-inflammatory, antiviral, antibacterial antiplasmodial, and antiobesity. In this study, the effect of XN supplementation on the lifespan extension was investigated in Drosophila melanogaster. The effects of XN on the improvement of the recovery from cold and heat shock, the resistance to starvation stress, and free radical-induced oxidative stress in XN-treated flies were also evaluated. Results showed that supplementation with XN at 0.5 mg/mL diet extended the mean lifespan by 14.89%. This was consistent with a significant improvement of locomotor activity of the Drosophila fed with an XN-mixed diet compared with those fed with a control diet. XN supplementation significantly increased the antioxidant enzyme activities at both 25 and 40 days. Drosophila treated with XN exhibited increased survival after exposure to hydrogen peroxide and paraquat. Finally, XN supplementation improved the recovery from cold and heat shock, the resistance to starvation stress, and acetic acid-induced stress. The present study shows that dietary supplementation with XN revealed the longevity effect and ameliorated stress-induced mortality in Drosophila.

Ethanol extract of Cassia siamea L. increases life span in Drosophila melanogaster

The stem of Cassia siamea L. (Fabaceae) has been used in traditional Thai medicine as a longevity remedy. The objective of this study was to investigate the effect of ethanolic stem extract of C. siamea (CSE) on the life span of Drosophila melanogaster. The results showed that a diet containing 10 mg/mL CSE could significantly extend the mean life span of D. melanogaster by 14% compared with the control diet (P < 0.01). The maximum life span was 74, 78, and 84 days in control, CSE (5 mg/mL) and CSE (10 mg/mL) groups, respectively. Supplementation of CSE at 10 mg/mL also significantly increases the activity of superoxide dismutase (SOD) and catalase (CAT) at days 25 and 40 compared with the control diet. Treatment of CSE at 5 and 10 mg/mL significantly increased the climbing ability of D. melanogaster both on days 25 and 40 compared with the control flies. Paraquat and H₂O₂ challenge test showed that flies fed with CSE at 10 mg/mL had a longer survival time than the control flies (P < 0.01). This study provides supportive evidence that supplementation with CSE prolonged life span and reduced oxidative stress in D. melanogaster.

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Supplementation with Cassia siamea extract extended the lifespan and improved the fly's locomotor activity

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C. siamea extract supplementation increased SOD and CAT activities in the fly.

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C. siamea extract supplementation improved survival after exposure to free radicals in the fly.

Proteostasis of Islet Amyloid Polypeptide: A Molecular Perspective of Risk Factors and Protective Strategies for Type II Diabetes

The possible link between hIAPP accumulation and β-cell death in diabetic patients has inspired numerous studies focusing on amyloid structures and aggregation pathways of this hormone. Recent studies have reported on the importance of early oligomeric intermediates, the many roles of their interactions with lipid membrane, pH, insulin, and zinc on the mechanism of aggregation of hIAPP. The challenges posed by the transient nature of amyloid oligomers, their structural heterogeneity, and the complex nature of their interaction with lipid membranes have resulted in the development of a wide range of biophysical and chemical approaches to characterize the aggregation process. While the cellular processes and factors activating hIAPP-mediated cytotoxicity are still not clear, it has recently been suggested that its impaired turnover and cellular processing by proteasome and autophagy may contribute significantly toward toxic hIAPP accumulation and, eventually, β-cell death. Therefore, studies focusing on the restoration of hIAPP proteostasis may represent a promising arena for the design of effective therapies. In this review we discuss the current knowledge of the structures and pathology associated with hIAPP self-assembly and point out the opportunities for therapy that a detailed biochemical, biophysical, and cellular understanding of its aggregation may unveil.

Targeting α-synuclein for PD Therapeutics: A Pursuit on All Fronts

Parkinson's Disease (PD) is characterized both by the loss of dopaminergic neurons in the substantia nigra and the presence of cytoplasmic inclusions called Lewy Bodies. These Lewy Bodies contain the aggregated α-synuclein (α-syn) protein, which has been shown to be able to propagate from cell to cell and throughout different regions in the brain. Due to its central role in the pathology and the lack of a curative treatment for PD, an increasing number of studies have aimed at targeting this protein for therapeutics. Here, we reviewed and discussed the many different approaches that have been studied to inhibit α-syn accumulation via direct and indirect targeting. These analyses have led to the generation of multiple clinical trials that are either completed or currently active. These clinical trials and the current preclinical studies must still face obstacles ahead, but give hope of finding a therapy for PD with time.

α-Synuclein Trafficking in Parkinson's Disease: Insights From Fly and Mouse Models

Protein aggregation and accumulation are common pathological hallmarks in neurodegenerative diseases. To efficiently clear and eliminate such aggregation becomes an important cellular strategy for cell survival. Lewy bodies inclusion and aggregation of α-Synuclein (α-Syn) during the pathogenesis of Parkinson's disease (PD) serve as a good example and are potentially linked to other pathological PD features such as progressive dopaminergic neuron cell death, behavioral defects, and nonmotor symptoms like anosmia, cognitive impairment, and depression. Years of research have revealed a variety of mechanisms underlying α-Syn aggregation, clearance, and spread. Particularly, vesicular routes associated with the trafficking of α-Syn, leading to its aggregation and accumulation, have been shown to play vital roles in PD pathogenesis. How α-Syn proteins propagate among cells in a prion-like manner, either from or to neurons and glia, via means of uptake or secretion, are questions under active investigation and have been of central interest in the field of PD study. This review covers components and pathways of possible vesicular routes involved in α-Syn trafficking. Events including but not limited to exocytosis and endocytosis will be discussed within the context of an overall cellular trafficking theme. Recent advances on α-Syn trafficking mechanisms and their significance in mediating PD pathogenesis will be thoroughly reviewed, ending with a discussion on the advantages and limitations of different animal PD models.

Non-Proteasomal UbL-UbA Family of Proteins in Neurodegeneration

Ubiquitin-like/ubiquitin-associated proteins (UbL-UbA) are a well-studied family of non-proteasomal ubiquitin receptors that are evolutionarily conserved across species. Members of this non-homogenous family facilitate and support proteasomal activity by promoting different effects on proteostasis but exhibit diverse extra-proteasomal activities. Dysfunctional UbL-UbA proteins render cells, particularly neurons, more susceptible to stressors or aging and may cause earlier neurodegeneration. In this review, we summarized the properties and functions of UbL-UbA family members identified to date, with an emphasis on new findings obtained using Drosophila models showing a direct or indirect role in some neurodegenerative diseases.

Efficient brain uptake and distribution of an expanded CAG RNA inhibitor DB213 via intranasal administration

DB213 is an expanded CAG RNA inhibitor targeting polyglutamine diseases. This current study aims to investigate biopharmaceutic characteristics of DB213 as well as its brain uptake and distribution in C57 wild type mice, R6/2 Huntington's disease mice and Sprague-Dawley (SD) rats via intranasal administration. The biopharmaceutic characteristics of DB213 were investigated in vitro using Calu-3/MDCK/HEK293 cell lines and brain slices for its membrane transport, equilibrium dialysis for its plasma protein/brain tissue bindings and liver/brain microsomes incubation for its enzyme kinetics profiles. In vivo study of DB213 brain distribution was conducted in rats via intravenous and intranasal routes at 50 mg/kg followed by its brain uptake evaluation in mice at 25 mg/kg via intranasal route. In vitro membrane transport studies found that DB213 not only had a limited passive diffusion with a P_{app (a→b)} value of 1.75 × 10^-6 cm/s in Calu-3 cell monolayer model but also was substrate of MRP2, MRP3, and amino acid transporter. Furthermore, DB213 demonstrated higher binding towards brain homogenate (80%) than plasma (10%) with limited metabolism in liver and brain. After intranasal administration of DB213, both olfactory bulb and trigeminal nerve served as its entry points to reach brain as demonstrated in rats while efficient brain uptake was observed in mice. In summary, limited nasal epithelium permeability and MRP2/MRP3 mediated efflux transport of DB213 could be overcome by its influx transport via amino acid transporter and minimal liver and brain metabolism, which further contribute to its rapid brain uptake and distribution in mice and rats.

Modeling Parkinson's Disease in Drosophila: What Have We Learned for Dominant Traits?

Parkinson’s disease (PD) is recognized as the second most common neurodegenerative disorder after Alzheimer’s disease. Unfortunately, there is no cure or proven disease modifying therapy for PD. The recent discovery of a number of genes involved in both sporadic and familial forms of PD has enabled disease modeling in easily manipulable model systems. Various model systems have been developed to study the pathobiology of PD and provided tremendous insights into the molecular mechanisms underlying dopaminergic neurodegeneration. Among all the model systems, the power of Drosophila has revealed many genetic factors involved in the various pathways, and provided potential therapeutic targets. This review focuses on Drosophila models of PD, with emphasis on how Drosophila models have provided new insights into the mutations of dominant genes causing PD and what are the convergent mechanisms.

Proteasome Activation by Small Molecules

Drugs that increase 26S proteasome activity have potential therapeutic applications in the treatment of neurodegenerative diseases. A chemical genetics screen of over 2,750 compounds using a proteasome activity probe as a readout in a high-throughput live-cell fluorescence-activated cell sorting-based assay revealed more than ten compounds that increase proteasome activity, with the p38 MAPK inhibitor PD169316 being one of the most potent ones. Genetic and chemical inhibition of either p38 MAPK, its upstream regulators, ASK1 and MKK6, and downstream target, MK2, enhance proteasome activity. Chemical activation of the 26S proteasome increases PROTAC-mediated and ubiquitin-dependent protein degradation and decreases the levels of both overexpressed and endogenous α-synuclein, without affecting the overall protein turnover. In addition, survival of cells overexpressing toxic α-synuclein assemblies is increased in the presence of p38 MAPK inhibitors. These findings highlight the potential of activation of 26S proteasome activity and that this can be achieved through multiple mechanisms by distinct molecules.

Review: Spreading the word: precise animal models and validated methods are vital when evaluating prion-like behaviour of alpha-synuclein

Synucleinopathies are characterized by abnormal proteinaceous aggregates, mainly composed of fibrillar α-synuclein (α-syn). It is now believed that α-syn can form small aggregates in a restricted number of cells, that propagate to neighbouring cells and seed aggregation of endogenous α-syn, in a 'prion-like manner'. This process could underlie the stereotypical progression of Lewy bodies described by Braak and colleagues across different stages of Parkinson's disease (PD). This prion-like behaviour of α-syn has been recently investigated in animal models of PD or multiple system atrophy (MSA). These models investigate the cell-to-cell transfer of α-syn seeds, or the induction and spreading of α-syn pathology in transgenic or wild-type rodent brain. In this review, we first outline the involvement of α-syn in Lewy body diseases and MSA, and discuss how 'prion-like' mechanisms can contribute to disease. Thereon, we debate the relevance of animal models used to study prion-like propagation. Finally, we review current main histological methods used to assess α-syn pathology both in animal models and in human samples and their relevance to the disease. Specifically, we discuss using α-syn phosphorylated at serine 129 as a marker of pathology, and the novel methods available that allow for more sensitive detection of early pathology, which has relevance for modelling synucleinopathies.

Salidroside reduces tau hyperphosphorylation via up-regulating GSK-3β phosphorylation in a tau transgenic Drosophila model of Alzheimer's disease

Background

Alzheimer’s disease (AD) is an age-related and progressive neurodegenerative disease that causes substantial public health care burdens. Intensive efforts have been made to find effective and safe treatment against AD. Salidroside (Sal) is the main effective component of Rhodiola rosea L., which has several pharmacological activities.

The objective of this study was to investigate the efficacy of Sal in the treatment of AD transgenic Drosophila and the associated mechanisms.

Methods

We used tau transgenic Drosophila line (TAU) in which tau protein is expressed in the central nervous system and eyes by the Gal4/UAS system. After feeding flies with Sal, the lifespan and locomotor activity were recorded. We further examined the appearance of vacuoles in the mushroom body using immunohistochemistry, and detected the levels of total glycogen synthase kinase 3β (t-GSK-3β), phosphorylated GSK-3β (p-GSK-3β), t-tau and p-tau in the brain by western blot analysis.

Results

Our results showed that the longevity was improved in salidroside-fed Drosophila groups as well as the locomotor activity. We also observed less vacuoles in the mushroom body, upregulated level of p-GSK-3β and downregulated p-tau following Sal treatment.

Conclusion

Our data presented the evidence that Sal was capable of reducing the neurodegeneration in tau transgenic Drosophila and inhibiting neuronal loss. The neuroprotective effects of Sal were associated with its up-regulation of the p-GSK-3β and down-regulation of the p-tau.

Mechanisms of Parkinson's Disease: Lessons from Drosophila

The power of Drosophila genetics has attracted attention in tackling important biomedical challenges such as the understanding and prevention of neurodegenerative diseases. Parkinson's disease (PD) is the most common neurodegenerative movement disorder which results from the relentless degeneration of midbrain dopaminergic neurons. Over the past two decades tremendous advances have been made in identifying genes responsible for inherited forms of PD. The ease of genetic manipulation in Drosophila has spurred the development of numerous models of PD, including expression of human genes carrying pathogenic mutations or the targeted mutation of conserved orthologs. The genetic and cellular analysis of these models is beginning to reveal fundamental insights into the pathogenic mechanisms. Numerous pathways and processes are disrupted in these models but some common themes are emerging. These often implicate aberrant synaptic function, protein aggregation, autophagy, oxidative stress, and mitochondrial dysfunction. Moreover, an impressive list of small molecule compounds have been identified as effective in reversing pathogenic phenotypes, paving the way to explore these for therapeutic interventions.

Synaptic signalling and its interface with neuropathologies: snapshots from the past, present and future

This 'Past to Future' Review as part of the 60th anniversary year of the Journal of Neurochemistry focuses on synaptic transmission and associated signalling, and seeks to identify seminal progress in neurochemistry over the last 10 years which has advanced our understanding of neuronal communication in brain. The approach adopted analyses neurotransmitters on a case by case basis (i.e. amino acids, monoamines, acetylcholine, neuropeptides, ATP/purines and gasotransmitters) to highlight novel findings that have changed the way we view each type of transmitter, to explore commonalities and interactions, and to note how new insights have changed the way we view the biology of degenerative, psychiatric and behavioural conditions. Across all transmitter systems there was remarkable growth in the identification of targets likely to provide therapeutic benefit and which undoubtedly was driven by the elucidation of circuit function and new vistas of synaptic signalling. There has been an increasing trend to relate signalling to disease, notably for Alzheimer's and Parkinson's disease and related conditions, and which has occurred for each transmitter family. Forebrain circuitry and tonic excitatory control have been the centre of great attention yielding novel findings that will impact upon cognitive, emotional and addictive behaviours. Other impressive insights focus on gasotransmitters integrating activity as volume transmitters. Exciting developments in how serotonin, cholinergic, l-glutamate, galanin and adenosine receptors and their associated signalling can be beneficially targeted should underpin the development of new therapies. Clearly integrated, multifaceted neurochemistry has changed the way we view synaptic signalling and its relevance to pathobiology. Highlighted are important advances in synaptic signalling over the last decade in the Journal of Neurochemistry. Across all transmitter systems elucidation of circuit function, and notably molecular insights, have underpinned remarkable growth in the identification of targets likely to provide therapeutic benefit in neuropathologies. Another commonality was wide interest in forebrain circuitry and its tonic excitatory control. Increasingly observations relate to signalling in disease and behavioural conditions. This article is part of the 60th Anniversary special issue.

Neuroprotective effects of salidroside through PI3K/Akt pathway activation in Alzheimer's disease models

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by deposits of aggregated amyloid-β (Aβ) peptide and neurofibrillary tangles in the brain parenchyma. Despite considerable research to elucidate the pathological mechanisms and identify therapeutic strategies for AD, effective treatments are still lacking. In the present study, we found that salidroside (Sal), a phenylpropanoid glycoside isolated from Rhodiola rosea L., can protect against Aβ-induced neurotoxicity in four transgenic Drosophila AD models. Both longevity and locomotor activity were improved in Sal-fed Drosophila. Sal also decreased Aβ levels and Aβ deposition in brain and ameliorated toxicity in Aβ-treated primary neuronal culture. The neuroprotective effect of Sal was associated with upregulated phosphatidylinositide 3-kinase (PI3K)/Akt signaling. Our findings identify a compound that may possess potential therapeutic benefits for AD and other forms of neurodegeneration.

USP5 Is Dispensable for Monoubiquitin Maintenance in Drosophila

Ubiquitination is a post-translational modification that regulates most cellular pathways and processes, including degradation of proteins by the proteasome. Substrate ubiquitination is controlled at various stages, including through its reversal by deubiquitinases (DUBs). A critical outcome of this process is the recycling of monoubiquitin. One DUB whose function has been proposed to include monoubiquitin recycling is USP5. Here, we investigated whether Drosophila USP5 is important for maintaining monoubiquitin in vivo We found that the fruit fly orthologue of USP5 has catalytic preferences similar to its human counterpart and that this DUB is necessary during fly development. Our biochemical and genetic experiments indicate that reduction of USP5 does not lead to monoubiquitin depletion in developing flies. Also, introduction of exogenous ubiquitin does not suppress developmental lethality caused by loss of endogenous USP5. Our work indicates that a primary physiological role of USP5 is not to recycle monoubiquitin for reutilization, but that it may involve disassembly of conjugated ubiquitin to maintain proteasome function.

UPS Activation in the Battle Against Aging and Aggregation-Related Diseases: An Extended Review

Aging is a biological process accompanied by gradual increase of damage in all cellular macromolecules, i.e., nucleic acids, lipids, and proteins. When the proteostasis network (chaperones and proteolytic systems) cannot reverse the damage load due to its excess as compared to cellular repair/regeneration capacity, failure of homeostasis is established. This failure is a major hallmark of aging and/or aggregation-related diseases. Dysfunction of the major cellular proteolytic machineries, namely the proteasome and the lysosome, has been reported during the progression of aging and aggregation-prone diseases. Therefore, activation of these pathways is considered as a possible preventive or therapeutic approach against the progression of these processes. This chapter focuses on UPS activation studies in cellular and organismal models and the effects of such activation on aging, longevity and disease prevention or reversal.

Inhibition of Protein Ubiquitination by Paraquat and 1-Methyl-4-Phenylpyridinium Impairs Ubiquitin-Dependent Protein Degradation Pathways

Intracytoplasmic inclusions of protein aggregates in dopaminergic cells (Lewy bodies) are the pathological hallmark of Parkinson's disease (PD). Ubiquitin (Ub), alpha (α)-synuclein, p62/sequestosome 1, and oxidized proteins are the major components of Lewy bodies. However, the mechanisms involved in the impairment of misfolded/oxidized protein degradation pathways in PD are still unclear. PD is linked to mitochondrial dysfunction and environmental pesticide exposure. In this work, we evaluated the effects of the pesticide paraquat (PQ) and the mitochondrial toxin 1-methyl-4-phenylpyridinium (MPP(+)) on Ub-dependent protein degradation pathways. No increase in the accumulation of Ub-bound proteins or aggregates was observed in dopaminergic cells (SK-N-SH) treated with PQ or MPP(+), or in mice chronically exposed to PQ. PQ decreased Ub protein content, but not its mRNA transcription. Protein synthesis inhibition with cycloheximide depleted Ub levels and potentiated PQ-induced cell death. The inhibition of proteasomal activity by PQ was found to be a late event in cell death progression and had neither effect on the toxicity of either MPP(+) or PQ, nor on the accumulation of oxidized sulfenylated, sulfonylated (DJ-1/PARK7 and peroxiredoxins), and carbonylated proteins induced by PQ. PQ- and MPP(+)-induced Ub protein depletion prompted the dimerization/inactivation of the Ub-binding protein p62 that regulates the clearance of ubiquitinated proteins by autophagy. We confirmed that PQ and MPP(+) impaired autophagy flux and that the blockage of autophagy by the overexpression of a dominant-negative form of the autophagy protein 5 (dnAtg5) stimulated their toxicity, but there was no additional effect upon inhibition of the proteasome. PQ induced an increase in the accumulation of α-synuclein in dopaminergic cells and membrane-associated foci in yeast cells. Our results demonstrate that the inhibition of protein ubiquitination by PQ and MPP(+) is involved in the dysfunction of Ub-dependent protein degradation pathways.

High Throughput Sequencing Identifies MicroRNAs Mediating α-Synuclein Toxicity by Targeting Neuroactive-Ligand Receptor Interaction Pathway in Early Stage of Drosophila Parkinson's Disease Model

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder with pathological features including death of dopaminergic neurons in the substantia nigra and intraneuronal accumulations of Lewy bodies. As the main component of Lewy bodies, α-synuclein is implicated in PD pathogenesis by aggregation into insoluble filaments. However, the detailed mechanisms underlying α-synuclein induced neurotoxicity in PD are still elusive. MicroRNAs are ~20nt small RNA molecules that fine-tune gene expression at posttranscriptional level. A plethora of miRNAs have been found to be dysregulated in the brain and blood cells of PD patients. Nevertheless, the detailed mechanisms and their in vivo functions in PD still need further investigation. By using Drosophila PD model expressing α-synuclein A30P, we examined brain miRNA expression with high-throughput small RNA sequencing technology. We found that five miRNAs (dme-miR-133-3p, dme-miR-137-3p, dme-miR-13b-3p, dme-miR-932-5p, dme-miR-1008-5p) were upregulated in PD flies. Among them, miR-13b, miR-133, miR-137 are brain enriched and highly conserved from Drosophila to humans. KEGG pathway analysis using DIANA miR-Path demonstrated that neuroactive-ligand receptor interaction pathway was most likely affected by these miRNAs. Interestingly, miR-137 was predicted to regulate most of the identified targets in this pathway, including dopamine receptor (DopR, D2R), γ-aminobutyric acid (GABA) receptor (GABA-B-R1, GABA-B-R3) and N-methyl-D-aspartate (NMDA) receptor (Nmdar2). The validation experiments showed that the expression of miR-137 and its targets was negatively correlated in PD flies. Further experiments using luciferase reporter assay confirmed that miR-137 could act on specific sites in 3’ UTR region of D2R, Nmdar2 and GABA-B-R3, which downregulated significantly in PD flies. Collectively, our findings indicate that α-synuclein could induce the dysregulation of miRNAs, which target neuroactive ligand-receptor interaction pathway in vivo. We believe it will help us further understand the contribution of miRNAs to α-synuclein neurotoxicity and provide new insights into the pathogenesis driving PD.

Proteasome activation: An innovative promising approach for delaying aging and retarding age-related diseases

Aging is a natural process accompanied by a progressive accumulation of damage in all constituent macromolecules (nucleic acids, lipids and proteins). Accumulation of damage in proteins leads to failure of proteostasis (or vice versa) due to increased levels of unfolded, misfolded or aggregated proteins and, in turn, to aging and/or age-related diseases. The major cellular proteolytic machineries, namely the proteasome and the lysosome, have been shown to dysfunction during aging and age-related diseases. Regarding the proteasome, it is well established that it can be activated either through genetic manipulation or through treatment with natural or chemical compounds that eventually result to extension of lifespan or deceleration of the progression of age-related diseases. This review article focuses on proteasome activation studies in several species and cellular models and their effects on aging and longevity. Moreover, it summarizes findings regarding proteasome activation in the major age-related diseases as well as in progeroid syndromes.

Synthetic Proteins and Peptides for the Direct Interrogation of α-Synuclein Posttranslational Modifications

α-Synuclein is the aggregation-prone protein associated with Parkinson’s disease (PD) and related neurodegenerative diseases. Complicating both its biological functions and toxic aggregation are a variety of posttranslational modifications. These modifications have the potential to either positively or negatively affect α-synuclein aggregation, raising the possibility that the enzymes that add or remove these modifications could be therapeutic targets in PD. Synthetic protein chemistry is uniquely positioned to generate site-specifically and homogeneously modified proteins for biochemical study. Here, we review the application of synthetic peptides and proteins towards understanding the effects of α-synuclein posttranslational modifications.

Anchanling reduces pathology in a lactacystin- induced Parkinson's disease model

A rat model of Parkinson's disease was induced by injecting lactacystin stereotaxically into the left mesencephalic ventral tegmental area and substantia nigra pars compacta. After rats were intragastrically perfused with Anchanling, a Chinese medicine, mainly composed of magnolol, for 5 weeks, when compared with Parkinson's disease model rats, tyrosine hydroxylase expression was increased, α-synuclein and ubiquitin expression was decreased, substantia nigra cell apoptosis was reduced, and apomorphine-induced rotational behavior was improved. Results suggested that Anchanling can ameliorate Parkinson's disease pathology possibly by enhancing degradation activity of the ubiquitin-proteasome system.

Protective effects of the thioredoxin and glutaredoxin systems in dopamine-induced cell death

Although the etiology of sporadic Parkinson disease (PD) is unknown, it is well established that oxidative stress plays an important role in the pathogenic mechanism. The thioredoxin (Trx) and glutaredoxin (Grx) systems are two central systems upholding the sulfhydryl homeostasis by reducing disulfides and mixed disulfides within the cell and thereby protecting against oxidative stress. By examining the expression of redox proteins in human postmortem PD brains, we found the levels of Trx1 and thioredoxin reductase 1 (TrxR1) to be significantly decreased. The human neuroblastoma cell line SH-SY5Y and the nematode Caenorhabditis elegans were used as model systems to explore the potential protective effects of the redox proteins against 6-hydroxydopamine (6-OHDA)-induced cytotoxicity. 6-OHDA is highly prone to oxidation, resulting in the formation of the quinone of 6-OHDA, a highly reactive species and powerful neurotoxin. Treatment of human cells with 6-OHDA resulted in an increased expression of Trx1, TrxR1, Grx1, and Grx2, and small interfering RNA for these genes significantly increased the cytotoxic effects exerted by the 6-OHDA neurotoxin. Evaluation of the dopaminergic neurons in C. elegans revealed that nematodes lacking trxr-1 were significantly more sensitive to 6-OHDA, with significantly increased neuronal degradation. Importantly, both the Trx and the Grx systems were also found to directly mediate reduction of the 6-OHDA-quinone in vitro and thus render its cytotoxic effects. In conclusion, our results suggest that the two redox systems are important for neuronal survival in dopamine-induced cell death.

The ubiquitin-proteasome system in neurodegenerative diseases: precipitating factor, yet part of the solution

The ubiquitin-proteasome system (UPS) has been implicated in neurodegenerative diseases based on the presence of deposits consisting of ubiquitylated proteins in affected neurons. It has been postulated that aggregation-prone proteins associated with these disorders, such as α-synuclein, β-amyloid peptide, and polyglutamine proteins, compromise UPS function, and delay the degradation of other proteasome substrates. Many of these substrates play important regulatory roles in signaling, cell cycle progression, or apoptosis, and their inadvertent stabilization due to an overloaded and improperly functioning UPS may thus be responsible for cellular demise in neurodegeneration. Over the past decade, numerous studies have addressed the UPS dysfunction hypothesis using various model systems and techniques that differ in their readout and sensitivity. While an inhibitory effect of some disease proteins on the UPS has been demonstrated, increasing evidence attests that the UPS remains operative in many disease models, which opens new possibilities for treatment. In this review, we will discuss the paradigm shift that repositioned the UPS from being a prime suspect in the pathophysiology of neurodegeneration to an attractive therapeutic target that can be harnessed to accelerate the clearance of disease-linked proteins.

Biology of ageing and role of dietary antioxidants

Interest in relationship between diet and ageing is growing. Research has shown that dietary calorie restriction and some antioxidants extend lifespan in various ageing models. On the one hand, oxygen is essential to aerobic organisms because it is a final electron acceptor in mitochondria. On the other hand, oxygen is harmful because it can continuously generate reactive oxygen species (ROS), which are believed to be the factors causing ageing of an organism. To remove these ROS in cells, aerobic organisms possess an antioxidant defense system which consists of a series of enzymes, namely, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR). In addition, dietary antioxidants including ascorbic acid, vitamin A, vitamin C, α-tocopherol, and plant flavonoids are also able to scavenge ROS in cells and therefore theoretically can extend the lifespan of organisms. In this connection, various antioxidants including tea catechins, theaflavins, apple polyphenols, black rice anthocyanins, and blueberry polyphenols have been shown to be capable of extending the lifespan of fruit flies. The purpose of this review is to brief the literature on modern biological theories of ageing and role of dietary antioxidants in ageing as well as underlying mechanisms by which antioxidants can prolong the lifespan with focus on fruit flies as an model.

Autophagy and apoptosis dysfunction in neurodegenerative disorders

Autophagy and apoptosis are basic physiologic processes contributing to the maintenance of cellular homeostasis. Autophagy encompasses pathways that target long-lived cytosolic proteins and damaged organelles. It involves a sequential set of events including double membrane formation, elongation, vesicle maturation and finally delivery of the targeted materials to the lysosome. Apoptotic cell death is best described through its morphology. It is characterized by cell rounding, membrane blebbing, cytoskeletal collapse, cytoplasmic condensation, and fragmentation, nuclear pyknosis, chromatin condensation/fragmentation, and formation of membrane-enveloped apoptotic bodies, that are rapidly phagocytosed by macrophages or neighboring cells. Neurodegenerative disorders are becoming increasingly prevalent, especially in the Western societies, with larger percentage of members living to an older age. They have to be seen not only as a health problem, but since they are care-intensive, they also carry a significant economic burden. Deregulation of autophagy plays a pivotal role in the etiology and/or progress of many of these diseases. Herein, we briefly review the latest findings that indicate the involvement of autophagy in neurodegenerative diseases. We provide a brief introduction to autophagy and apoptosis pathways focusing on the role of mitochondria and lysosomes. We then briefly highlight pathophysiology of common neurodegenerative disorders like Alzheimer's diseases, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Then, we describe functions of autophagy and apoptosis in brain homeostasis, especially in the context of the aforementioned disorders. Finally, we discuss different ways that autophagy and apoptosis modulation may be employed for therapeutic intervention during the maintenance of neurodegenerative disorders.

The Aqueous Extract of Rhizome of Gastrodia elata Protected Drosophila and PC12 Cells against Beta-Amyloid-Induced Neurotoxicity

This study aims to investigate the neuroprotective effect of the rhizome of Gastrodia elata (GE) aqueous extract on beta-amyloid(Aβ)-induced toxicity in vivo and in vitro. Transgenic Drosophila mutants with Aβ-induced neurodegeneration in pan-neuron and ommatidia were used to determine the efficacy of GE. The antiapoptotic and antioxidative mechanisms of GE were also studied in Aβ-treated pheochromocytoma (PC12) cells. In vivo studies demonstrated that GE (5 mg/g Drosophila media)-treated Drosophila possessed a longer lifespan, better locomotor function, and less-degenerated ommatidia when compared with the Aβ-expressing control (all P < 0.05). In vitro studies illustrated that GE increased the cell viability of Aβ-treated PC12 cells in dose-dependent manner, probably through attenuation of Aβ-induced oxidative and apoptotic stress. GE also significantly upregulated the enzymatic activities of catalase, superoxide dismutase, and glutathione peroxidase, leading to the decrease of reactive oxidation species production and apoptotic marker caspase-3 activity. In conclusion, our current data presented the first evidence that the aqueous extract of GE was capable of reducing the Aβ-induced neurodegeneration in Drosophila, possibly through inhibition of apoptosis and reduction of oxidative stress. GE aqueous extract could be developed as a promising herbal agent for neuroprotection and novel adjuvant therapies for Alzheimer's disease.

Phospho-dependent ubiquitination and degradation of PAR-1 regulates synaptic morphology and tau-mediated Aβ toxicity in Drosophila

The conserved kinases PAR-1/MARK are critically involved in processes such as asymmetric cell division, cell polarity and neuronal differentiation. Their deregulation has been implicated in diseases including Alzheimer's disease and cancer. Given the importance of PAR-1/MARK in health and disease, their activities need to be tightly controlled. However, little is known about the molecular mechanisms underlying their regulation in vivo. Here we show that in Drosophila, a phosphorylation-dependent ubiquitination mechanism restrains PAR-1 activation. Active PAR-1 generated by LKB1-controlled phosphorylation is targeted for ubiquitination and degradation by SCF (Skp, Cullin, F-box containing complex) (Slimb), whose action is antagonized by the deubiquitinating enzyme fat facets. This newly identified PAR-1-modifying module critically regulates synaptic morphology and tau-mediated postsynaptic toxicity of amyloid precursor protein (APP)/Aβ-42, the causative agents of Alzheimer's disease, at the Drosophila neuromuscular junction. Our results provide new insights into the regulation of PAR-1 in various physiological processes and offer new therapeutic strategies for diseases involving PAR-1/MARK deregulation.

Effect of trehalose on PC12 cells overexpressing wild-type or A53T mutant α-synuclein

Accumulation of α-synuclein (α-Syn) is a common pathology for both familiar and sporadic Parkinson's disease (PD), enhancing its clearance might be a promising strategy for treating PD. To assess the potential of trehalose in this regard, we investigated its effect on the PC12 cells overexpressing wild type (WT) or A53T mutant α-Syn and the implicated pathway it might mediated. We observed that trehalose promoted the clearance of A53T α-Syn but not WT α-Syn in PC12 cells, and confirmed the increased LC3 and Lysotracker RED positive autolysosomes by using lysotracker and LC3 staining, the enhanced expression of LC3-II in Western blot, and more autophagosomes under Transmission Electron Microscope in a dose dependent manner after the trehalose treatment. The activation of autophagy can be alleviated by applying macroautophagy inhibitor 3-methyladenine (3-MA). In addition, degradation of A53T and WT α-Syn was blocked after Ubiquitin Proteasome System (UPS) inhibitor (MG132) was applied in those PC12 cells overexpressing A53T or WT α-Syn, suggesting that A53T α-Syn could be degraded by both UPS and macroautophagy. But the effect of trehalose on A53T α-Syn is mainly mediated through the macroautophagy pathway, which is not a dominant way for WT α-Syn clearance. Further in vivo research will be needed to verify the effectiveness of trehalose in treating PD.

Melatonin attenuates kainic acid-induced neurotoxicity in mouse hippocampus via inhibition of autophagy and α-synuclein aggregation

In this study, the protective effect of melatonin on kainic acid (KA)-induced neurotoxicity involving autophagy and α-synuclein aggregation was investigated in the hippocampus of C57/BL6 mice. Our data showed that intraperitoneal injection of KA (20 mg/kg) increased LC3-II levels (a hallmark protein of autophagy) and reduced mitochondrial DNA content and cytochrome c oxidase levels (a protein marker of mitochondria). Atg7 siRNA transfection prevented KA-induced LC3-II elevations and mitochondria loss. Furthermore, Atg7 siRNA attenuated KA-induced activation of caspases 3/12 (biomarkers of apoptosis) and hippocampal neuronal loss, suggesting a pro-apoptotic role of autophagy in the KA-induced neurotoxicity. Nevertheless, KA-induced α-synuclein aggregation was not affected in the Atg7 siRNA-transfected hippocampus. The neuroprotective effect of melatonin (50 mg/kg) orally administered 1 hr prior to KA injection was studied. Melatonin was found to inhibit KA-induced autophagy-lysosomal activation by reducing KA-induced increases in LC3-II, lysosomal-associated membrane protein 2 (a biomarker of lysosomes) and cathepsin B (a lysosomal cysteine protease). Subsequently, KA-induced mitochondria loss was prevented in the melatonin-treated mice. At the same time, melatonin reduced KA-increased HO-1 levels and α-synuclein aggregation. Our immunoprecipitation study showed that melatonin enhanced ubiquitination of α-synuclein monomers and aggregates. The anti-apoptotic effect of melatonin was demonstrated by attenuating KA-induced DNA fragmentation, activation of caspases 3/12, and neuronal loss. Taken together, our study suggests that KA-induced neurotoxicity may be mediated by autophagy and α-synuclein aggregation. Moreover, melatonin may exert its neuroprotection via inhibiting KA-induced autophagy and a subsequent mitochondrial loss as well as reducing α-synuclein aggregation by enhancing α-synuclein ubiquitination in the CNS.

Molecular insights into Parkinson's disease

Mutations in SNCA, PINK1, parkin, and DJ-1 are associated with autosomal-dominant or autosomal-recessive forms of Parkinson's disease (PD), the second most common neurodegenerative disorder. Studies on the structural and functional properties of the corresponding gene products have provided significant insights into the molecular underpinnings of familial PD and the much more common sporadic forms of the disease. Here, we review recent advances in our understanding of four PD-related gene products: α-synuclein, parkin, PINK1, and DJ-1. In Part 1, we review new insights into the role of α-synuclein in PD. In Part 2, we summarize the latest developments in understanding the role of mitochondrial dysfunction in PD, emphasizing the role of the PINK1/parkin pathway in regulating mitochondrial dynamics and mitophagy. The role of DJ-1 is also discussed. In Part 3, we point out converging pathways and future directions.

Structure and recognition of polyubiquitin chains of different lengths and linkage

The polyubiquitin signal is post-translationally attached to a large number of proteins, often directing formation of macromolecular complexes resulting in the translocation, assembly or degradation of the attached protein. Recent structural and functional studies reveal general mechanisms by which different architectures and length of the signal are distinguished.

Α-synuclein misfolding and Parkinson's disease

Substantial evidence links α-synuclein, a small highly conserved presynaptic protein with unknown function, to both familial and sporadic Parkinson's disease (PD). α-Synuclein has been identified as the major component of Lewy bodies and Lewy neurites, the characteristic proteinaceous deposits that are the hallmarks of PD. α-Synuclein is a typical intrinsically disordered protein, but can adopt a number of different conformational states depending on conditions and cofactors. These include the helical membrane-bound form, a partially-folded state that is a key intermediate in aggregation and fibrillation, various oligomeric species, and fibrillar and amorphous aggregates. The molecular basis of PD appears to be tightly coupled to the aggregation of α-synuclein and the factors that affect its conformation. This review examines the different aggregation states of α-synuclein, the molecular mechanism of its aggregation, and the influence of environmental and genetic factors on this process.

Neuropathology in mice expressing mouse alpha-synuclein

α-Synuclein (αSN) in human is tightly linked both neuropathologically and genetically to Parkinson's disease (PD) and related disorders. Disease-causing properties in vivo of the wildtype mouse ortholog (mαSN), which carries a threonine at position 53 like the A53T human mutant version that is genetically linked to PD, were never reported. To this end we generated mouse lines that express mαSN in central neurons at levels reaching up to six-fold compared to endogenous mαSN. Unlike transgenic mice expressing human wildtype or mutant forms of αSN, these mαSN transgenic mice showed pronounced ubiquitin immunopathology in spinal cord and brainstem. Isoelectric separation of mαSN species revealed multiple isoforms including two Ser129-phosphorylated species in the most severely affected brain regions. Neuronal Ser129-phosphorylated αSN occured in granular and small fibrillar aggregates and pathological staining patterns in neurites occasionally revealed a striking ladder of small alternating segments staining either for Ser129-phosphorylated αSN or ubiquitin but not both. Axonal degeneration in long white matter tracts of the spinal cord, with breakdown of myelin sheaths and degeneration of neuromuscular junctions with loss of integrity of the presynaptic neurofilament network in mαSN transgenic mice, was similar to what we have reported for mice expressing human αSN wildtype or mutant forms. In hippocampal neurons, the mαSN protein accumulated and was phosphorylated but these neurons showed no ubiquitin immunopathology. In contrast to the early-onset motor abnormalities and muscle weakness observed in mice expressing human αSN, mαSN transgenic mice displayed only end-stage phenotypic alterations that manifested alongside with neuropathology. Altogether these findings show that increased levels of wildtype mαSN does not induce early-onset behavior changes, but drives end-stage pathophysiological changes in murine neurons that are strikingly similar to those evoked by expression of human wildtype or mutant forms.

Apple polyphenols extend the mean lifespan of Drosophila melanogaster

Apple polyphenols (AP) are an excellent source of dietary antioxidants. The present study investigated the effect of AP on the lifespan of fruit flies and their interaction with gene expressions of superoxide dismutase (SOD), catalase (CAT), methuselah (MTH), Rpn11, and cytochrome c oxidase (CcO) subunits III and VIb. Results showed the mean lifespan was significantly extended by 10% in fruit flies fed the AP diet. This was accompanied by up-regulation of genes SOD1, SOD2, and CAT and down-regulation of MTH in the aged fruit flies. Paraquat and H(2)O(2) challenge tests demonstrated that AP prolonged the survival time only for Oregon R wild type flies but not for SOD(n108) or Cat(n1) mutants, in which either SOD or CAT was knocked out. Chronic paraquat exposure could shorten the maximum lifespan from 68 to 31 days and reduce the climbing ability by 60%, whereas AP could partially reverse the paraquat-induced mortality and decline in climbing ability. AP could up-regulate Rpn11 at day 30, whereas it appeared to have no significant effect on gene expression of ubiquitinated protein, CcO subunits III and VIb. These AP-induced changes were unlikely associated with caloric restriction as the gustatory assay found no difference in average body weight and stomach redness index between the control and AP fruit flies. It was therefore concluded that the antiaging activity of AP was, at least in part, mediated by its interaction with genes SOD, CAT, MTH, and Rpn11.

Drosophila models of Parkinson's disease: discovering relevant pathways and novel therapeutic strategies

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is mainly characterized by the selective and progressive loss of dopaminergic neurons, accompanied by locomotor defects. Although most PD cases are sporadic, several genes are associated with rare familial forms of the disease. Analyses of their function have provided important insights into the disease process, demonstrating that three types of cellular defects are mainly involved in the formation and/or progression of PD: abnormal protein aggregation, oxidative damage, and mitochondrial dysfunction. These studies have been mainly performed in PD models created in mice, fruit flies, and worms. Among them, Drosophila has emerged as a very valuable model organism in the study of either toxin-induced or genetically linked PD. Indeed, many of the existing fly PD models exhibit key features of the disease and have been instrumental to discover pathways relevant for PD pathogenesis, which could facilitate the development of therapeutic strategies.

Protein aggregation in Parkinson's disease

Parkinson's disease (PD) is a primary neurodegenerative movement disorder. In most cases it occurs as a sporadic type of disease, but there are also rare familial forms. Pathologically Parkinson's disease is characterized by loss of dopaminergic neurons in the compact part of substantia nigra. As a part of the neurodegenerative process protein aggregates will accumulate as Lewy bodies in dopaminergic neurons (1). In addition, non-dopaminergic neurons are known to be affected in Parkinsons's disease, for example, in several brain stem nuclei and the olfactoric bulb (2-4). The pathogenic process underlying the death of dopaminergic neurons is far from fully understood. Along with mitochondrial dysfunction, excitotoxicity, neuroinflammation and oxidative stress (5-8), recent evidence indicates that accumulation of protein filaments in Lewy bodies actively takes part in the degeneration of neurons. This will be further discussed below.

Drosophila models of Parkinson's disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder principally affecting the dopaminergic neurons of the substantia nigra. The pathogenic mechanisms are unknown and there are currently no cure or disease-modifying therapies. Recent genetic linkage studies have begun to identify single-gene mutations responsible for rare heritable forms of PD and define genetic risk factors contributing to disease prevalence in sporadic cases. These findings provide an opportunity to gain insight into the molecular mechanisms of this disorder through the creation and analysis of appropriate genetic models. One model system that has proven surprisingly tractable for these studies is the fruit fly, Drosophila melanogaster. Analysis of a number of Drosophila models of PD has revealed some profound and sometimes surprising insights into PD pathogenesis. Moreover, these models can be used to investigate potential therapeutic strategies that may be effective in vivo, and tests have highlighted the efficacy of a number of neuroprotective compounds. Here, I review the methodologies employed in developing the various Drosophila models, and the recent advances that these models in particular have contributed to our understanding of the mechanisms that underlie PD pathogenesis and possible treatment strategies.

α-Synuclein Transgenic Drosophila As a Model of Parkinson's Disease and Related Synucleinopathies

α-Synuclein (α-Syn) is a major component of protein inclusions known as Lewy bodies, which are hallmarks of synucleinopathies such as Parkinson's disease (PD). The α-Syn gene is one of the familial PD-causing genes and is also associated with an increased risk of sporadic PD. Numerous studies using α-Syn expressing transgenic animals have indicated that α-Syn plays a critical role in the common pathogenesis of synucleinopathies. Drosophila melanogaster has several advantages for modeling human neurodegenerative diseases and is widely used for studying their pathomechanisms and therapies. In fact, Drosophila models expressing α-Syn have already been established and proven to replicate several features of human PD. In this paper, we review the current research on synucleinopathies using α-Syn Drosophila models and, moreover, explore the possibilities of these models for comprehensive genetic analyses and large-scale drug screening towards elucidating the molecular pathogenesis and developing therapies for synucleinopathies.

New insights into the role of mitochondrial dysfunction and protein aggregation in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative movement disorder that affects increasing number of elderly in the world population. The disease is caused by a selective degeneration of dopaminergic neurons in the substantia nigra pars compacta with the molecular mechanism underlying this neurodegeneration still not fully understood. However, various studies have shown that mitochondrial dysfunction and abnormal protein aggregation are two of the major contributors for PD. In fact this notion has been supported by recent studies on genes that are linked to familial PD (FPD). For instance, FPD linked gene products such as PINK1 and parkin have been shown to play critical roles in the quality control of mitochondria, whereas α-synuclein has been found to be the major protein aggregates accumulated in PD patients. These findings suggest that further understanding of how dysfunction of these pathways in PD will help develop new approaches for the treatment of this neurodegenerative disorder.

Review: the ubiquitin-proteasome system: contributions to cell death or survival in neurodegeneration

The significance of the accumulation of ubiquitin-positive intraneuronal inclusions in the brains of those affected with different neurodegenerative diseases is currently unclear. While one interpretation is that the disease mechanism(s) involves dysfunction of an ubiquitin-mediated process, such as the ubiquitin-proteasome system, the inclusions are also found in surviving neurones, suggesting a possible neuroprotective role. Here we review recent evidence in support of these seemingly opposing notions gleaned from cell and animal models as well as investigations of patient samples, with particular emphasis on studies relevant to Parkinson's disease.

Role of post-translational modifications in modulating the structure, function and toxicity of alpha-synuclein: implications for Parkinson's disease pathogenesis and therapies

A better understanding of the molecular and cellular determinants that influence the pathology of Parkinson's disease (PD) is essential for developing effective diagnostic, preventative and therapeutic strategies to treat this devastating disease. A number of post-translational modifications to alpha-syn are present within the Lewy bodies in the brains of affected patients and transgenic models of PD and related disorders. However, whether disease-associated alpha-syn post-translational modifications promote or inhibit alpha-syn aggregation and neurotoxicity in vivo remains unknown. Herein, we summarize and discuss the major disease-associated post-translational modifications (phosphorylation, truncation and ubiquitination) and present our current understanding of the effect of these modifications on alpha-syn aggregation and toxicity. Elucidating the molecular mechanisms underlying post-translation modifications of alpha-syn and the consequences of such modifications on the biochemical, structural, aggregation and toxic properties of the protein is essential for unravelling the molecular basis of its function(s) in health and disease. Furthermore, the identification of the natural enzymes involved in regulating the post-translational modifications of alpha-synuclein will yield novel and more tractable therapeutic targets to treat PD and related synucleinopathies.

Degradation of TDP-43 and its pathogenic form by autophagy and the ubiquitin-proteasome system

TAR DNA-binding protein-43 (TDP-43) is a nuclear protein functioning in the regulation of transcription and mRNA splicing. TDP-43 is accumulated in ubiquitinated inclusions in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS) diseased brains. However, the pathways involved in the clearance of TDP-43 and its pathogenic form (TDP-25), a truncated form of TDP-43, are still not elucidated. In this study, we demonstrated that the protein levels of TDP-43 and TDP-25 were increased in cells treated with a proteasome inhibitor, MG132, or an autophagy inhibitor, 3-MA, whereas, they were decreased in cells treated with an enhancer of autophagy, trehalose. Furthermore, more protein level changes of TDP-25 than TDP-43 were observed in cells treated with above inhibitors or enhancer. Thus, our data suggest that TDP-43 and TDP-25 are degraded by both proteasome and autophagy with TDP-25 being more regulated.