Showing papers on "Proteotoxicity published in 2013"

Parkin overexpression during aging reduces proteotoxicity, alters mitochondrial dynamics, and extends lifespan

Abstract: Aberrant protein aggregation and mitochondrial dysfunction have each been linked to aging and a number of age-onset neurodegenerative disorders, including Parkinson disease. Loss-of-function mutations in parkin, an E3 ubiquitin ligase that functions to promote the ubiquitin–proteasome system of protein degradation and also in mitochondrial quality control, have been implicated in heritable forms of Parkinson disease. The question of whether parkin can modulate aging or positively impact longevity, however, has not been addressed. Here, we show that ubiquitous or neuron-specific up-regulation of Parkin, in adult Drosophila melanogaster, increases both mean and maximum lifespan without reducing reproductive output, physical activity, or food intake. Long-lived Parkin-overexpressing flies display an increase in K48-linked polyubiquitin and reduced levels of protein aggregation during aging. Recent evidence suggests that Parkin interacts with the mitochondrial fission/fusion machinery to mediate the turnover of dysfunctional mitochondria. However, the relationships between parkin gene activity, mitochondrial dynamics, and aging have not been explored. We show that the mitochondrial fusion-promoting factor Drosophila Mitofusin, a Parkin substrate, increases in abundance during aging. Parkin overexpression results in reduced Drosophila Mitofusin levels in aging flies, with concomitant changes in mitochondrial morphology and an increase in mitochondrial activity. Together, these findings reveal roles for Parkin in modulating organismal aging and provide insight into the molecular mechanisms linking aging to neurodegeneration.

Proteotoxicity and Cardiac Dysfunction — Alzheimer's Disease of the Heart?

Abstract: Defective disposal of misfolded proteins is involved in the pathogenesis of neurodegenerative diseases, cystic fibrosis, and heart failure. Experimental studies suggest that therapies that target misfolded proteins may have broad clinical application.

The ART-Rsp5 ubiquitin ligase network comprises a plasma membrane quality control system that protects yeast cells from proteotoxic stress

Abstract: Cells have evolved elaborate mechanisms for the detection of misfolded or damaged proteins, and for targeting their degradation Since the accumulation of misfolded proteins is toxic to the cell, these protein quality control systems are critical for the maintenance of normal cellular function over the lifetime of an organism The breakdown of this quality control correlates with the progression of neurodegenerative disorders including Alzheimer's, Huntington's and Parkinson's disease Normal function of the protein quality control machinery can also cause disease: this is the case with channelopathies such as cystic fibrosis, in which mutant ion channels are targeted for degradation and therefore cannot function correctly at the cell surface Understanding how protein quality control systems recognize misfolded proteins and target their degradation, and designing ways to stabilize or destabilize specific targets, particularly at the cell surface, could thus lead to the development of new therapeutic strategies While protein quality control mechanisms in the cytosol and endoplasmic reticulum (ER) have been studied extensively, much less is known about quality control of integral membrane proteins after they exit the ER Maintaining the quality of cell surface proteins impacts many critical biological functions including nutrient uptake, signaling and the functioning of specialized surface structures such as cell junctions Here, Zhao et al describe a new quality control mechanism that prevents misfolded proteins from accumulating in the plasma membrane Building upon earlier work describing a network of adaptor proteins (called ARTs) for the Rsp5 ubiquitin ligase, Zhao et al show that subjecting cells to proteotoxic stress, particularly thermal stress, triggers ART-Rsp5-mediated clearance of misfolded plasma membrane proteins When ART-Rsp5-mediated clearance is abrogated, misfolded proteins accumulate at the cell surface, resulting in a rapid loss of cellular integrity In the brain, such proteotoxicity can lead to cell death and neurodegeneration, thereby highlighting the importance of this plasma membrane quality control system

Stress proteins in aging and life span.

Abstract: Heat shock proteins (HSP) are molecular chaperones and have been implicated in longevity and aging in many species. Their major functions include chaperoning misfolded or newly synthesised polypeptides, protecting cells from proteotoxic stress, and processing of immunogenic agents. These proteins are expressed constitutively and can be induced by stresses such as heat, oxidative stress and many more. The induction of HSP in aging could potentially maintain protein homeostasis and longevity by refolding the damaged proteins which accumulate during aging and are toxic to cells. HSP are shown to increase life span in model organisms such as Caenorhabditis elegans and decrease aging-related proteotoxicity. Thus, decrease in HSP in aging is associated with disruption of cellular homeostasis which causes diseases such as cancer, cell senescence and neurodegeneration. HSP levels are decreased with aging in most organs including neurons. Aging also causes attenuation or alteration of many signalling pathw...

Protein homeostasis as a therapeutic target for diseases of protein conformation.

Abstract: Protein misfolding and aggregation are widely implicated in an increasing number of human diseases providing for new therapeutic opportunities targeting protein homeostasis (proteostasis). The cellular response to proteotoxicity is highly regulated by stress signaling pathways, molecular chaperones, transport and clearance machineries that function as a proteostasis network (PN) to protect the stability and functional properties of the proteome. Consequently, the PN is essential at the cellular and organismal level for development and lifespan. However, when challenged during aging, stress, and disease, the folding and clearance machineries can become compromised leading to both gain-of-function and loss-of-function proteinopathies. Here, we assess the role of small molecules that activate the heat shock response, the unfolded protein response, and clearance mechanisms to increase PN capacity and protect cellular proteostasis against proteotoxicity. We propose that this strategy to enhance cell stress pathways and chaperone activity establishes a cytoprotective state against misfolding and/or aggregation and represents a promising therapeutic avenue to prevent the cellular damage associated with the variety of protein conformational diseases.

Latrepirdine stimulates autophagy and reduces accumulation of α-synuclein in cells and in mouse brain

Abstract: Latrepirdine (Dimebon; dimebolin) is a neuroactive compound that was associated with enhanced cognition, neuroprotection and neurogenesis in laboratory animals, and has entered phase II clinical trials for both Alzheimer's disease and Huntington's disease (HD). Based on recent indications that latrepirdine protects cells against cytotoxicity associated with expression of aggregatable neurodegeneration-related proteins, including Aβ42 and γ-synuclein, we sought to determine whether latrepirdine offers protection to Saccharomyces cerevisiae. We utilized separate and parallel expression in yeast of several neurodegeneration-related proteins, including α-synuclein (α-syn), the amyotrophic lateral sclerosis-associated genes TDP43 and FUS, and the HD-associated protein huntingtin with a 103 copy-polyglutamine expansion (HTT gene; htt-103Q). Latrepirdine effects on α-syn clearance and toxicity were also measured following treatment of SH-SY5Y cells or chronic treatment of wild-type mice. Latrepirdine only protected yeast against the cytotoxicity associated with α-syn, and this appeared to occur via induction of autophagy. We further report that latrepirdine stimulated the degradation of α-syn in differentiated SH-SY5Y neurons, and in mouse brain following chronic administration, in parallel with elevation of the levels of markers of autophagic activity. Ongoing experiments will determine the utility of latrepirdine to abrogate α-syn accumulation in transgenic mouse models of α-syn neuropathology. We propose that latrepirdine may represent a novel scaffold for discovery of robust pro-autophagic/anti-neurodegeneration compounds, which might yield clinical benefit for synucleinopathies including Parkinson's disease, Lewy body dementia, rapid eye movement (REM) sleep disorder and/or multiple system atrophy, following optimization of its pro-autophagic and pro-neurogenic activities.

Modulation of 5-lipoxygenase in proteotoxicity and Alzheimer's disease.

Abstract: The accumulation of intracellular β amyloid (Aβ) may be one of the factors leading to neuronal cell death in Alzheimer's disease (AD). Using a pyrazole called CNB-001, which was selected for its ability to reduce intracellular Aβ, we show that the activation of the eIF2α/ATF4 arm of the unfolded protein response is sufficient to degrade aggregated intracellular Aβ. CNB-001 is a potent inhibitor of 5-lipoxygenase (5-LOX), decreases 5-LOX expression, and increases proteasome activity. 5-LOX inhibition induces eIF2α and PERK (protein kinase R-like extracellular signal-regulated kinase) phosphorylation, and HSP90 and ATF4 levels. When fed to AD transgenic mice, CNB-001 also increases eIF2α phosphorylation and HSP90 and ATF4 levels, and limits the accumulation of soluble Aβ and ubiquitinated aggregated proteins. Finally, CNB-001 maintains the expression of synapse-associated proteins and improves memory. Therefore, 5-LOX metabolism is a key element in the promotion of endoplasmic reticulum dysfunction, and its inhibition under conditions of stress is sufficient to reduce proteotoxicity both in vivo and in vitro.

The Hsp70/90 cochaperone, Sti1, suppresses proteotoxicity by regulating spatial quality control of amyloid-like proteins.

Abstract: Conformational diseases are associated with the conversion of normal proteins into aggregation-prone toxic conformers with structures similar to that of β-amyloid. Spatial distribution of amyloid-like proteins into intracellular quality control centers can be beneficial, but cellular mechanisms for protective aggregation remain unclear. We used a high-copy suppressor screen in yeast to identify roles for the Hsp70 system in spatial organization of toxic polyglutamine-expanded Huntingtin (Huntingtin with 103Q glutamine stretch [Htt103Q]) into benign assemblies. Under toxic conditions, Htt103Q accumulates in unassembled states and speckled cytosolic foci. Subtle modulation of Sti1 activity reciprocally affects Htt toxicity and the packaging of Htt103Q into foci. Loss of Sti1 exacerbates Htt toxicity and hinders foci formation, whereas elevation of Sti1 suppresses Htt toxicity while organizing small Htt103Q foci into larger assemblies. Sti1 also suppresses cytotoxicity of the glutamine-rich yeast prion [RNQ+] while reorganizing speckled Rnq1–monomeric red fluorescent protein into distinct foci. Sti1-inducible foci are perinuclear and contain proteins that are bound by the amyloid indicator dye thioflavin-T. Sti1 is an Hsp70 cochaperone that regulates the spatial organization of amyloid-like proteins in the cytosol and thereby buffers proteotoxicity caused by amyloid-like proteins.

A Neuronal GPCR is Critical for the Induction of the Heat Shock Response in the Nematode C. elegans

Abstract: In the nematode Caenorhabditis elegans, the heat shock response (HSR) is regulated at the organismal level by a network of thermosensory neurons that senses elevated temperatures and activates the HSR in remote tissues. Which neuronal receptors are required for this signaling mechanism and in which neurons they function are largely unanswered questions. Here we used worms that were engineered to exhibit RNA interference hypersensitivity in neurons to screen for neuronal receptors that are required for the activation of the HSR and identified a putative G-protein coupled receptor (GPCR) as a novel key component of this mechanism. This gene, which we termed GPCR thermal receptor 1 (gtr-1), is expressed in chemosensory neurons and has no role in heat sensing but is critically required for the induction of genes that encode heat shock proteins in non-neural tissues upon exposure to heat. Surprisingly, the knock-down of gtr-1 by RNA interference protected worms expressing the Alzheimer's-disease-linked aggregative peptide Aβ3-42 from proteotoxicity but had no effect on lifespan. This study provides several novel insights: (1) it shows that chemosensory neurons play important roles in the nematode's HSR-regulating mechanism, (2) it shows that lifespan and heat stress resistance are separable, and (3) it strengthens the emerging notion that the ability to respond to heat comes at the expense of protein homeostasis (proteostasis).

NAD+ salvage pathway proteins suppress proteotoxicity in yeast models of neurodegeneration by promoting the clearance of misfolded/oligomerized proteins.

Abstract: Increased levels of nicotinamide/nicotinic acid mononucleotide adenylyltransferase (NMNAT) act as a powerful suppressor of Wallerian degeneration and ataxin- and tau-induced neurodegeneration in flies and mice. However, the nature of the suppression mechanism/s remains controversial. Here, we show that in yeast models of proteinopathies, overexpression of the NMNAT yeast homologs, NMA1 and NMA2, suppresses polyglutamine (PolyQ) and α-synuclein-induced cytotoxicities. Unexpectedly, overexpression of other genes in the salvage pathway for NAD(+) biosynthesis, including QNS1, NPT1 and PNC1 also protected against proteotoxicity. Our data revealed that in all cases, this mechanism involves extensive clearance of the non-native protein. Importantly, we demonstrate that suppression by NMA1 does not require the presence of a functional salvage pathway for NAD(+) biosynthesis, SIR2 or an active mitochondrial oxidative phosphorylation (OXPHOS) system. Our results imply the existence of histone deacetylase- and OXPHOS-independent crosstalk between the proteins in the salvage pathway for NAD(+) biosynthesis and the proteasome that can be manipulated to achieve cellular protection against proteotoxic stress.

Natural genetic variation determines susceptibility to aggregation or toxicity in a C. elegans model for polyglutamine disease

Abstract: Monogenic gain-of-function protein aggregation diseases, including Huntington’s disease, exhibit substantial variability in age of onset, penetrance, and clinical symptoms, even between individuals with similar or identical mutations. This difference in phenotypic expression of proteotoxic mutations is proposed to be due, at least in part, to the variability in genetic background. To address this, we examined the role of natural variation in defining the susceptibility of genetically diverse individuals to protein aggregation and toxicity, using the Caenorhabditis elegans polyglutamine model. Introgression of polyQ40 into three wild genetic backgrounds uncovered wide variation in onset of aggregation and corresponding toxicity, as well as alteration in the cell-specific susceptibility to aggregation. To further dissect these relationships, we established a panel of 21 recombinant inbred lines that showed a broad range of aggregation phenotypes, independent of differences in expression levels. We found that aggregation is a transgressive trait, and does not always correlate with measures of toxicity, such as early onset of muscle dysfunction, egg-laying deficits, or reduced lifespan. Moreover, distinct measures of proteotoxicity were independently modified by the genetic background. Resistance to protein aggregation and the ability to restrict its associated cellular dysfunction are independently controlled by the natural variation in genetic background, revealing important new considerations in the search for targets for therapeutic intervention in conformational diseases. Thus, our C. elegans model can serve as a powerful tool to dissect the contribution of natural variation to individual susceptibility to proteotoxicity. Please see related commentary by Kaeberlein, http://www.biomedcentral.com/1741-7007/11/102 .

Nutrient-driven O-GlcNAc cycling influences autophagic flux and neurodegenerative proteotoxicity

Abstract: O-GlcNAcylation is an abundant post-translational modification implicated in human neurodegenerative diseases. We showed that loss-of-function of OGT (O-linked GlcNAc transferase) alleviated, while loss of OGA (O-GlcNAc selective β-N-acetyl-D-glucosaminidase) enhanced, the proteotoxicity of C. elegans neurodegenerative disease models including tauopathy, β-amyloid peptide and polyglutamine expansion. The O-GlcNAc cycling mutants act, in part, by altering insulin signaling, proteasome activity and autophagy. In mutants lacking either of these enzymes of O-GlcNAc cycling, there is a striking accumulation of GFP::LGG-1 (C. elegans homolog of Atg8 and LC3) and increased phosphatidylethanolamine (PE)-modified GFP::LGG-1 upon starvation. We speculate that O-GlcNAc cycling is a key nutrient-responsive regulator of autophagic flux acting at multiple levels including direct modification of BECN1 and BCL2.

Motoneuronal and muscle-selective removal of ALS-related misfolded proteins

Abstract: ALS (amyotrophic lateral sclerosis), a fatal motoneuron (motor neuron) disease, occurs in clinically indistinguishable sporadic (sALS) or familial (fALS) forms. Most fALS-related mutant proteins identified so far are prone to misfolding, and must be degraded in order to protect motoneurons from their toxicity. This process, mediated by molecular chaperones, requires proteasome or autophagic systems. Motoneurons are particularly sensitive to misfolded protein toxicity, but other cell types such as the muscle cells could also be affected. Muscle-restricted expression of the fALS protein mutSOD1 (mutant superoxide dismutase 1) induces muscle atrophy and motoneuron death. We found that several genes have an altered expression in muscles of transgenic ALS mice at different stages of disease. MyoD, myogenin, atrogin-1, TGFβ1 (transforming growth factor β1) and components of the cell response to proteotoxicity [HSPB8 (heat shock 22 kDa protein 8), Bag3 (Bcl-2-associated athanogene 3) and p62] are all up-regulated by mutSOD1 in skeletal muscle. When we compared the potential mutSOD1 toxicity in motoneuron (NSC34) and muscle (C2C12) cells, we found that muscle ALS models possess much higher chymotryptic proteasome activity and autophagy power than motoneuron ALS models. As a result, mutSOD1 molecular behaviour was found to be very different. MutSOD1 clearance was found to be much higher in muscle than in motoneurons. MutSOD1 aggregated and impaired proteasomes only in motoneurons, which were particularly sensitive to superoxide-induced oxidative stress. Moreover, in muscle cells, mutSOD1 was found to be soluble even after proteasome inhibition. This effect could be associated with a higher mutSOD1 autophagic clearance. Therefore muscle cells seem to manage misfolded mutSOD1 more efficiently than motoneurons, thus mutSOD1 toxicity in muscle may not directly depend on aggregation.

Regulating the ubiquitin/proteasome pathway via cAMP-signaling: neuroprotective potential

Abstract: The cAMP-signaling pathway has been under intensive investigation for decades. It is a wonder that such a small simple molecule like cAMP can modulate a vast number of diverse processes in different types of cells. The ubiquitous involvement of cAMP-signaling in a variety of cellular events requires tight spatial and temporal control of its generation, propagation, compartmentalization, and elimination. Among the various steps of the cAMP-signaling pathway, G-protein-coupled receptors, adenylate cyclases, phosphodiesterases, the two major cAMP targets, i.e., protein kinase A and exchange protein activated by cAMP, as well as the A-kinase anchoring proteins, are potential targets for drug development. Herein we review the recent progress on the regulation and manipulation of different steps of the cAMP-signaling pathway. We end by focusing on the emerging role of cAMP-signaling in modulating protein degradation via the ubiquitin/proteasome pathway. New discoveries on the regulation of the ubiquitin/proteasome pathway by cAMP-signaling support the development of new therapeutic approaches to prevent proteotoxicity in chronic neurodegenerative disorders and other human disease conditions associated with impaired protein turnover by the ubiquitin/proteasome pathway and the accumulation of ubiquitin-protein aggregates.

Astrocyte plasticity revealed by adaptations to severe proteotoxic stress

Abstract: Neurodegeneration is characterized by an accumulation of misfolded proteins in neurons. It is less well appreciated that glia often also accumulate misfolded proteins. However, glia are highly plastic and may adapt to stress readily. Endogenous adaptations to stress can be measured by challenging stressed cells with a second hit and then measuring viability. For example, subtoxic stress can elicit preconditioning or tolerance against second hits. However, it is not known if severe stress that kills half the population can elicit endogenous adaptations in the remaining survivors. Glia, with their resilient nature, offer an ideal model in which to test this new hypothesis. The present study is the first demonstration that astrocytes surviving one LC50 hit of the proteasome inhibitor MG132 were protected against a second MG132 hit. ATP loss in response to the second hit was also prevented. MG132 caused compensatory rises in stress-sensitive heat shock proteins. However, stressed astrocytes exhibited an even greater rise in ubiquitin-conjugated proteins upon the second hit, illustrating the severity of the proteotoxicity and verifying the continued impact of MG132. Despite this stress, MG132-pretreated astrocytes were completely prevented from losing glutathione with the second hit. Furthermore, inhibiting glutathione synthesis rendered astrocytes sensitive to the second hit, unmasking the cumulative impact of two hits by removal of an endogenous adaptation. These findings suggest that stressed astrocytes become progressively harder to kill by virtue of antioxidant defenses. Such plasticity may permit astrocytes under severe stress to better support neurons and help explain the protracted nature of neurodegeneration.

A novel Rac1 GAP splice variant relays poly-Ub accumulation signals to mediate Rac1 inactivation

Abstract: Spatial control of RhoGTPase-inactivating GAP components remains largely enigmatic. We describe a brain-specific RhoGAP splice variant, BARGIN (BGIN), which comprises a combination of BAR, GAP, and partial CIN phosphatase domains spliced from adjacent SH3BP1 and CIN gene loci. Excision of BGIN exon 2 results in recoding of a 42–amino acid N-terminal stretch. The partial CIN domain is a poly-ubiquitin (poly-Ub)–binding module that facilitates BGIN distribution to membranous and detergent-insoluble fractions. Poly-Ub/BGIN interactions support BGIN-mediated inactivation of a membranous Rac1 population, which consequently inactivates membrane-localized Rac1 effector systems such as reactive oxygen species (ROS) generation by the Nox1 complex. Given that Ub aggregate pathology and proteotoxicity are central themes in various neurodegenerative disorders, we investigated whether BGIN/Rac1 signaling could be involved in neurodegenerative proteotoxicity. BGIN/Ub interactions are observed through colocalization in tangle aggregates in the Alzheimer’s disease (AD) brain. Moreover, enhanced BGIN membrane distribution correlates with reduced Rac1 activity in AD brain tissue. Finally, BGIN contributes to Rac1 inhibition and ROS generation in an amyloid precursor protein (APP) proteotoxicity model. These results suggest that BGIN/poly-Ub interactions enhance BGIN membrane distribution and relay poly-Ub signals to enact Rac1 inactivation, and attenuation of Rac1 signaling is partially dependent on BGIN in a proteotoxic APP context.

Chaperone-mediated autophagy: dedicated saviour and unfortunate victim in the neurodegeneration arena

Abstract: The importance of cellular quality-control systems in the maintenance of neuronal homoeostasis and in the defence against neurodegeneration is well recognized. Chaperones and proteolytic systems, the main components of these cellular surveillance mechanisms, are key in the fight against the proteotoxicity that is often associated with severe neurodegenerative diseases. However, in recent years, a new theme has emerged which suggests that components of protein quality-control pathways are often targets of the toxic effects of pathogenic proteins and that their failure to function properly contributes to pathogenesis and disease progression. In the present mini-review, we describe this dual role as 'saviour' and 'victim' in the context of neurodegeneration for chaperone-mediated autophagy, a cellular pathway involved in the selective degradation of cytosolic proteins in lysosomes.

Pathways to decoding the clinical potential of stress response FOXO-interaction networks for Huntington's disease: of gene prioritization and context dependence

Abstract: The FOXO family of transcription factors is central to the regulation of organismal longevity and cellular survival. Several studies have indicated that FOXO factors lie at the center of a complex network of upstream pathways, cofactors and downstream targets (FOXO-interaction networks), which may have developmental and post-developmental roles in the regulation of chronic-stress response in normal and diseased cells. Noticeably, FOXO factors are important for the regulation of proteotoxicity and neuron survival in several models of neurodegenerative disease, suggesting that FOXO-interaction networks may have therapeutic potential. However, the status of FOXO-interaction networks in neurodegenerative disease remains largely unknown. Systems modeling is anticipated to provide a comprehensive assessment of this question. In particular, interrogating the context-dependent variability of FOXO-interaction networks could predict the clinical potential of cellular-stress response genes and aging regulators for tackling brain and peripheral pathology in neurodegenerative disease. Using published transcriptomic data obtained from murine models of Huntington's disease (HD) and post-mortem brains, blood samples and induced-pluripotent-stem cells from HD carriers as a case example, this review briefly highlights how the biological status and clinical potential of FOXO-interaction networks for HD may be decoded by developing network and entropy based feature selection across heterogeneous datasets.

Using Caenorhabditis elegans to fight human neurodegenerative diseases

Abstract: Debilitating age-associated neurodegenerative disorders (NDs) are a major public health challenge in increasingly ageing societies. Currently approved therapeutics are successful in slowing the progression of NDs but not in reversing or preventing the symptoms. A major goal of neurodegeneration research is therefore to identify potential new therapies for these devastating and eventually fatal disorders. In this study, multiple well-defined C. elegans neurodegeneration models were integrated to uncover effective therapeutic interventions that target shared pathogenic pathways. Using locomotion behaviour and lifespan as phenotypic readouts, the well-established anti-epileptic drug ethosuximide was identified as a promising compound with the potential to combat more than one ND. It not only rescued the short lifespan and chemosensory defects of a C. elegans null mutant model of the rare autosomal dominant human ND known as adult-onset neuronal ceroid lipofuscinosis (ANCL), but also ameliorated the mobility defect and short lifespan of worm tauopathy and polyglutamine models based on transgenic expression of mutant human disease proteins. The ability of ethosuximide to rescue these phenotypes did not correlate well with levels of aggregated Tau and polyglutamine protein, suggesting that ethosuximide suppresses proteotoxicity without preventing protein aggregation. Although the main proposed therapeutic target of ethosuximide in epilepsy is the T-type calcium channel, deletion of its worm homologue, cca-1, did not affect the increase in locomotion and lifespan in the tauopathy model. This suggests that ethosuximide counteracts proteotoxicity via a novel mechanism. To further investigate how ethosuximide might exert its neuroprotective properties, we conducted global gene expression analyses using the Affymetrix C. elegans whole genome microarray platform and compared the transcriptome of ethosuximide-treated ANCL models and wild-type worms to that of unexposed controls. Various downstream bioinformatic investigations including gene ontology analyses, regulatory motif discovery, publication enrichment analysis, comparative analyses with curated data sources and literature were performed and revealed a wide range of DAF-16-dependent transcriptional alterations. C. elegans DAF-16 is the sole orthologue of the mammalian FOXO family of transcription factors (TFs) that are implicated in the regulation of a wide range of physiological processes. Genes commonly regulated in ethosuximide-treated animals have varied roles in lipid metabolism, redox homeostasis, longevity/ageing, chromatin remodelling and ubiquitination. Many ethosuximide-responsive genes also contained DAF-16 regulatory elements within their promoter regions and were known to be among the top most responsive DAF-16 TF targets. The importance of DAF-16 in ethosuximide-mediated protection was further substantiated by RNA interference and cell culture experiments. Ethosuximide was shown to consistently induce the transcriptional activity of a subset of mammalian FOXO target genes and conferred protection against expanded polyglutamine peptides-induced aggregation in mammalian neuronal cells. These findings should encourage further screening and characterisation of other neuroprotective compounds, and ultimately may assist in expediting translational drug research and clinical testing for new therapeutic targets to combat protein conformational disorders in general.

5th Conference on Advances in Molecular Mechanisms Underlying Neurological Disorders

Abstract: The importance of cellular quality-control systems in the maintenance of neuronal homoeostasis and in the defence against neurodegeneration is well recognized. Chaperones and proteolytic systems, the main components of these cellular surveillance mechanisms, are key in the fight against the proteotoxicity that is often associated with severe neurodegenerative diseases. However, in recent years, a new theme has emerged which suggests that components of protein quality-control pathways are often targets of the toxic effects of pathogenic proteins and that their failure to function properly contributes to pathogenesis and disease progression. In the present mini-review, we describe this dual role as ‘saviour’ and ‘victim’ in the context of neurodegeneration for chaperone-mediated autophagy, a cellular pathway involved in the selective degradation of cytosolic proteins in lysosomes. Proteotoxicity and autophagy: two sides of the same coin Intracellular accumulation of aberrant proteins is a feature shared by the group of human disorders known as proteinconformational diseases. The best known among these diseases are neurodegenerative conditions in which abnormal proteins accumulate in the form of inclusions in the affected neurons. It is well accepted that neurons utilize systems present in all cells to fight against the toxic effects of these aberrant proteins. A network of chaperones and proteolytic systems are at the forefront of the cellular response to protect against

Systemic Regulation of Cellular Stress Responses to Proteotoxicity by Neuroendocrine Signaling

Abstract: The proper regulation and function of cellular stress resistance pathways are essential to the maintenance of the proteome Impairment of these pathways leads to the accumulation of aggregates and misfolded proteins, resulting in age-associated neurodegenerative diseases Subsequent age-onset proteotoxic damage often is accompanied by widespread changes in peripheral metabolism Endocrine-based communication of cellular stress may play a causative role in the extensive metabolic changes seen in neurodegenerative disease Using C elegans models of proteotoxic stress, the impact of neuronal specific toxicity on peripheral cellular stress responses was assessed Proposed is a neuroendocrine system of regulation on the distal response of the mitochondrial unfolded protein response (UPRmt) Genetic loss in UPRmt function blocks the response in distal mitochondria, and both neurosecretion and the nutrient- responsive neurotransmitter serotonin are required for the signal's propagation This model of systemic stress regulation is used to evaluate the impact of other metabolic pathways in proteotoxicity and to identify novel signaling components that may play a role in the widespread pathology associated with neurodegenerative disease

Sex differences in the induced expression of Hsp70 and Hsp27 in the brain and heart of rats

Abstract: Permission is herewith granted to Dalhousie University to circulate and to have copied for non-commercial purposes, at its discretion, the above title upon the request of individuals or institutions. I understand that my thesis will be electronically available to the public. The author reserves other publication rights, and neither the thesis nor extensive extracts from it may be printed or otherwise reproduced without the author's written permission. The author attests that permission has been obtained for the use of any copyrighted material appearing in the thesis (other than the brief excerpts requiring only proper acknowledgement in scholarly writing), and that all such use is clearly acknowledged. _______________________________ Signature of Author iv I dedicate this thesis to my parents and my sisters whom provided me with, and continue to provide me with, enthusiasm to pursue my dreams.