RESUMO
While aggregation-prone proteins are known to accelerate aging and cause age-related diseases, the cellular mechanisms that drive their cytotoxicity remain unresolved. The orthologous proteins MOAG-4, SERF1A, and SERF2 have recently been identified as cellular modifiers of such proteotoxicity. Using a peptide array screening approach on human amyloidogenic proteins, we found that SERF2 interacted with protein segments enriched in negatively charged and hydrophobic, aromatic amino acids. The absence of such segments, or the neutralization of the positive charge in SERF2, prevented these interactions and abolished the amyloid-promoting activity of SERF2. In protein aggregation models in the nematode worm Caenorhabditis elegans, protein aggregation and toxicity were suppressed by mutating the endogenous locus of MOAG-4 to neutralize charge. Our data indicate that MOAG-4 and SERF2 drive protein aggregation and toxicity by interactions with negatively charged segments in aggregation-prone proteins. Such charge interactions might accelerate primary nucleation of amyloid by initiating structural changes and by decreasing colloidal stability. Our study points at charge interactions between cellular modifiers and amyloidogenic proteins as potential targets for interventions to reduce age-related protein toxicity.
Assuntos
Amiloide/química , Proteínas Amiloidogênicas/química , Proteínas de Caenorhabditis elegans/química , Caenorhabditis elegans/genética , Peptídeos e Proteínas de Sinalização Intracelular/química , Proteínas do Tecido Nervoso/química , alfa-Sinucleína/química , Sequência de Aminoácidos , Amiloide/genética , Amiloide/metabolismo , Proteínas Amiloidogênicas/genética , Proteínas Amiloidogênicas/metabolismo , Animais , Sítios de Ligação , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Regulação da Expressão Gênica , Células HEK293 , Humanos , Interações Hidrofóbicas e Hidrofílicas , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Peptídeos/genética , Peptídeos/metabolismo , Agregados Proteicos , Análise Serial de Proteínas , Ligação Proteica , Transdução de Sinais , Eletricidade Estática , alfa-Sinucleína/genética , alfa-Sinucleína/metabolismoRESUMO
Protein aggregation is associated with age-related neurodegenerative disorders, such as Alzheimer's and polyglutamine diseases. As a causal relationship between protein aggregation and neurodegeneration remains elusive, understanding the cellular mechanisms regulating protein aggregation will help develop future treatments. To identify such mechanisms, we conducted a forward genetic screen in a C. elegans model of polyglutamine aggregation and identified the protein MOAG-2/LIR-3 as a driver of protein aggregation. In the absence of polyglutamine, MOAG-2/LIR-3 regulates the RNA polymerase III-associated transcription of small non-coding RNAs. This regulation is lost in the presence of polyglutamine, which mislocalizes MOAG-2/LIR-3 from the nucleus to the cytosol. We then show biochemically that MOAG-2/LIR-3 can also catalyze the aggregation of polyglutamine-expanded huntingtin. These results suggest that polyglutamine can induce an aggregation-promoting activity of MOAG-2/LIR-3 in the cytosol. The concept that certain aggregation-prone proteins can convert other endogenous proteins into drivers of aggregation and toxicity adds to the understanding of how cellular homeostasis can be deteriorated in protein misfolding diseases.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/enzimologia , Doenças Neurodegenerativas/enzimologia , Peptídeos/metabolismo , Agregados Proteicos , Agregação Patológica de Proteínas , RNA Polimerase III/metabolismo , Fatores de Transcrição/metabolismo , Transporte Ativo do Núcleo Celular , Animais , Animais Geneticamente Modificados , Sítios de Ligação , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Núcleo Celular/enzimologia , Citosol/enzimologia , Modelos Animais de Doenças , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/patologia , Regiões Promotoras Genéticas , Ligação Proteica , Interferência de RNA , RNA Polimerase III/genética , Pequeno RNA não Traduzido/genética , Pequeno RNA não Traduzido/metabolismo , Fatores de Transcrição/genética , Transcrição GênicaRESUMO
Toxicity of aggregation-prone proteins is thought to play an important role in aging and age-related neurological diseases like Parkinson and Alzheimer's diseases. Here, we identify tryptophan 2,3-dioxygenase (tdo-2), the first enzyme in the kynurenine pathway of tryptophan degradation, as a metabolic regulator of age-related α-synuclein toxicity in a Caenorhabditis elegans model. Depletion of tdo-2 also suppresses toxicity of other heterologous aggregation-prone proteins, including amyloid-ß and polyglutamine proteins, and endogenous metastable proteins that are sensors of normal protein homeostasis. This finding suggests that tdo-2 functions as a general regulator of protein homeostasis. Analysis of metabolite levels in C. elegans strains with mutations in enzymes that act downstream of tdo-2 indicates that this suppression of toxicity is independent of downstream metabolites in the kynurenine pathway. Depletion of tdo-2 increases tryptophan levels, and feeding worms with extra L-tryptophan also suppresses toxicity, suggesting that tdo-2 regulates proteotoxicity through tryptophan. Depletion of tdo-2 extends lifespan in these worms. Together, these results implicate tdo-2 as a metabolic switch of age-related protein homeostasis and lifespan. With TDO and Indoleamine 2,3-dioxygenase as evolutionarily conserved human orthologs of TDO-2, intervening with tryptophan metabolism may offer avenues to reducing proteotoxicity in aging and age-related diseases.
Assuntos
Envelhecimento/fisiologia , Homeostase/fisiologia , Triptofano Oxigenase/metabolismo , Triptofano/metabolismo , alfa-Sinucleína/toxicidade , Envelhecimento/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans , Cromatografia Líquida , Biologia Computacional , Primers do DNA/genética , Fertilidade/genética , Immunoblotting , Longevidade/genética , Peptídeos/metabolismo , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Espectrometria de Massas em Tandem , Triptofano/química , Triptofano Oxigenase/antagonistas & inibidoresRESUMO
Amyotrophic lateral sclerosis can be caused by abnormal accumulation of TAR DNA-binding protein 43 (TDP-43) in the cytoplasm of neurons. Here, we use a C. elegans model for TDP-43-induced toxicity to identify the biological mechanisms that lead to disease-related phenotypes. By applying deep behavioral phenotyping and subsequent dissection of the neuromuscular circuit, we show that TDP-43 worms have profound defects in GABA neurons. Moreover, acetylcholine neurons appear functionally silenced. Enhancing functional output of repressed acetylcholine neurons at the level of, among others, G-protein-coupled receptors restores neurotransmission, but inefficiently rescues locomotion. Rebalancing the excitatory-to-inhibitory ratio in the neuromuscular system by simultaneous stimulation of the affected GABA- and acetylcholine neurons, however, not only synergizes the effects of boosting individual neurotransmitter systems, but instantaneously improves movement. Our results suggest that interventions accounting for the altered connectome may be more efficient in restoring motor function than those solely focusing on diseased neuron populations.
Assuntos
Caenorhabditis elegans , Proteínas de Ligação a DNA , Modelos Animais de Doenças , Animais , Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Neurônios GABAérgicos/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Neurônios Motores/metabolismo , Locomoção , Transmissão Sináptica , Movimento , Neurônios Colinérgicos/metabolismoRESUMO
Transactive response DNA binding-protein 43 (TDP-43) is a conserved RNA/DNA-binding protein with a role in RNA metabolism and homeostasis. Aberrant TDP-43 functioning has been considered a major culprit in amyotrophic lateral sclerosis (ALS). Caenorhabditis elegans can be used to phenocopy ALS in vivo . Since disrupted locomotion is a strong readout of toxicity, we examined multiple motor phenotypes of a C. elegans model expressing human wild-type TDP-43 ( hTDP-43 ) pan-neuronally. Our data reveal that impaired locomotion includes more than the common deficits in crawling capacity and the presence of early-onset paralysis. We show that reduced thrashing, abnormal coiling, and decreased pharyngeal pumping are also observed, in a temperature-dependent fashion.
RESUMO
Cytoplasmic inclusions consisting of transactive response DNA-binding protein 43 (TDP-43) are a key hallmark of TDP-43 proteinopathies like amyotrophic lateral sclerosis (ALS). Caenorhabditis elegans is considered a useful model for studying the molecular mechanisms underlying TDP-43 toxicity in vivo . Here, we assessed different neuronal systems through established behavioral assays and extended the phenotypic characterisation of a C. elegans model expressing wildtype human TDP-43 ( hTDP-43 ) pan-neuronally. Our data show that neuronal expression of hTDP-43 in C. elegans disrupts chemotaxis and decreases fecundity. The basal slowing response, on the other hand, appears to be preserved in the presence of hTDP-43.
RESUMO
Inclusions consisting of transactive response DNA-binding protein 43 (TDP-43) are a characteristic feature of amyotrophic lateral sclerosis (ALS). Caenorhabditis elegans has been instrumental in studying the underlying mechanisms of TDP-43 pathology. Here, we extend the possibilities of previous studies by examining a C. elegans model expressing human wild-type TDP-43 ( hTDP-43 ) pan-neuronally. We show that disease-related (hyper)phosphorylation and cytosolic localisation of hTDP-43 are present in hTDP-43 worms and that these features can be enhanced by adjusting the environmental temperature.
RESUMO
The aggregation of α-synuclein is a hallmark of Parkinson's disease (PD) and a variety of related neurological disorders. A number of mutations in this protein, including A30P and A53T, are associated with familial forms of the disease. Patients carrying the A30P mutation typically exhibit a similar age of onset and symptoms as sporadic PD, while those carrying the A53T mutation generally have an earlier age of onset and an accelerated progression. We report two C. elegans models of PD (PDA30P and PDA53T), which express these mutational variants in the muscle cells, and probed their behavior relative to animals expressing the wild-type protein (PDWT). PDA30P worms showed a reduced speed of movement and an increased paralysis rate, control worms, but no change in the frequency of body bends. By contrast, in PDA53T worms both speed and frequency of body bends were significantly decreased, and paralysis rate was increased. α-Synuclein was also observed to be less well localized into aggregates in PDA30P worms compared to PDA53T and PDWT worms, and amyloid-like features were evident later in the life of the animals, despite comparable levels of expression of α-synuclein. Furthermore, squalamine, a natural product currently in clinical trials for treating symptomatic aspects of PD, was found to reduce significantly the aggregation of α-synuclein and its associated toxicity in PDA53T and PDWT worms, but had less marked effects in PDA30P. In addition, using an antibody that targets the N-terminal region of α-synuclein, we observed a suppression of toxicity in PDA30P, PDA53T and PDWT worms. These results illustrate the use of these two C. elegans models in fundamental and applied PD research.
RESUMO
Caenorhabditis elegans is a valuable model organism in biomedical research that has led to major discoveries in the fields of neurodegeneration, cancer and aging. Because movement phenotypes are commonly used and represent strong indicators of C. elegans fitness, there is an increasing need to replace manual assessments of worm motility with automated measurements to increase throughput and minimize observer biases. Here, we provide a protocol for the implementation of the improved wide field-of-view nematode tracking platform (WF-NTP), which enables the simultaneous analysis of hundreds of worms with respect to multiple behavioral parameters. The protocol takes only a few hours to complete, excluding the time spent culturing C. elegans, and includes (i) experimental design and preparation of samples, (ii) data recording, (iii) software management with appropriate parameter choices and (iv) post-experimental data analysis. We compare the WF-NTP with other existing worm trackers, including those having high spatial resolution. The main benefits of WF-NTP relate to the high number of worms that can be assessed at the same time on a whole-plate basis and the number of phenotypes that can be screened for simultaneously.
Assuntos
Bioensaio/instrumentação , Caenorhabditis elegans/fisiologia , Movimento , Fenótipo , AnimaisRESUMO
Caenorhabditis elegans is widely used to investigate biological processes related to health and disease. Multiple C. elegans models for human neurodegenerative diseases do exist, including those expressing human α-synuclein. Even though these models do not feature all pathological and molecular hallmarks of the disease they mimic, they allow for the identification and dissection of molecular pathways that are involved. In line with this, genetic screens have yielded multiple modifiers of proteotoxicity in C. elegans models for neurodegenerative diseases. Here, we describe a set of common screening approaches and tools that can be used to study synucleinopathies and other neurodegenerative diseases in C. elegans. RNA interference and mutagenesis screens can be used to find genes that affect proteotoxicity, while relatively simple molecular, cellular (fractionation studies), metabolic (respiration studies), and behavioral (thrashing and crawling) readouts can be used to study the effects of disease proteins and modifiers more closely.
Assuntos
Doenças Neurodegenerativas/metabolismo , alfa-Sinucleína/metabolismo , Animais , Caenorhabditis elegans , Núcleo Celular/metabolismo , Citosol/metabolismo , Modelos Animais de Doenças , Humanos , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/patologia , Dobramento de Proteína , Transporte Proteico , Interferência de RNA , alfa-Sinucleína/química , alfa-Sinucleína/genéticaRESUMO
Aging strongly influences human morbidity and mortality. Thus, aging-preventive compounds could greatly improve our health and lifespan. Here we screened for such compounds, known as geroprotectors, employing the power of transcriptomics to predict biological age. Using age-stratified human tissue transcriptomes and machine learning, we generated age classifiers and applied these to transcriptomic changes induced by 1,309 different compounds in human cells, ranking these compounds by their ability to induce a "youthful" transcriptional state. Testing the top candidates in C. elegans, we identified two Hsp90 inhibitors, monorden and tanespimycin, which extended the animals' lifespan and improved their health. Hsp90 inhibition induces expression of heat shock proteins known to improve protein homeostasis. Consistently, monorden treatment improved the survival of C. elegans under proteotoxic stress, and its benefits depended on the cytosolic unfolded protein response-inducing transcription factor HSF-1. Taken together, our method represents an innovative geroprotector screening approach and was able to identify a class that acts by improving protein homeostasis.
Assuntos
Envelhecimento/efeitos dos fármacos , Benzoquinonas/farmacologia , Proteínas de Choque Térmico HSP90/antagonistas & inibidores , Lactamas Macrocíclicas/farmacologia , Macrolídeos/farmacologia , Envelhecimento/genética , Animais , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/antagonistas & inibidores , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Fatores de Transcrição de Choque Térmico/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/metabolismo , TranscriptomaRESUMO
C. elegans is widely used to investigate biological processes related to health and disease. To study protein localization, fluorescently-tagged proteins can be used in vivo or immunohistochemistry can be performed in whole worms. Here, we describe a technique to localize a protein of interest at a subcellular level in C. elegans lysates, which can give insight into the location, function and/or toxicity of proteins.
RESUMO
Protein aggregation is a hallmark of several neurodegenerative diseases and is associated with impaired protein homeostasis. This imbalance is caused by the loss of the protein's native conformation, which ultimately results in its aggregation or abnormal localization within the cell. Using a C. elegans model of polyglutamine diseases, we describe in detail the filter retardation assay, a method that captures protein aggregates in a cellulose acetate membrane and allows its detection and quantification by immunoblotting.
RESUMO
BACKGROUND: Whole-exome sequencing (WES) has been successful in identifying genes that cause familial Parkinson's disease (PD). However, until now this approach has not been deployed to study large cohorts of unrelated participants. To discover rare PD susceptibility variants, we performed WES in 1148 unrelated cases and 503 control participants. Candidate genes were subsequently validated for functions relevant to PD based on parallel RNA-interference (RNAi) screens in human cell culture and Drosophila and C. elegans models. RESULTS: Assuming autosomal recessive inheritance, we identify 27 genes that have homozygous or compound heterozygous loss-of-function variants in PD cases. Definitive replication and confirmation of these findings were hindered by potential heterogeneity and by the rarity of the implicated alleles. We therefore looked for potential genetic interactions with established PD mechanisms. Following RNAi-mediated knockdown, 15 of the genes modulated mitochondrial dynamics in human neuronal cultures and four candidates enhanced α-synuclein-induced neurodegeneration in Drosophila. Based on complementary analyses in independent human datasets, five functionally validated genes-GPATCH2L, UHRF1BP1L, PTPRH, ARSB, and VPS13C-also showed evidence consistent with genetic replication. CONCLUSIONS: By integrating human genetic and functional evidence, we identify several PD susceptibility gene candidates for further investigation. Our approach highlights a powerful experimental strategy with broad applicability for future studies of disorders with complex genetic etiologies.
Assuntos
Predisposição Genética para Doença , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Doença de Parkinson/genética , Análise de Sequência de DNA/métodos , alfa-Sinucleína/genética , Adolescente , Adulto , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/genética , Estudos de Casos e Controles , Células Cultivadas , Criança , Modelos Animais de Doenças , Drosophila melanogaster/genética , Exoma , Humanos , Pessoa de Meia-Idade , Interferência de RNA , Adulto JovemRESUMO
The enzyme TDO (tryptophan 2,3-dioxygenase; TDO-2 in Caenorhabditis elegans) is a potential therapeutic target to cancer but is also thought to regulate proteotoxic events seen in the progression of neurodegenerative diseases. To better understand its function and develop specific compounds that target TDO we need to understand the structure of this molecule. In C. elegans we compared multiple different CRISPR/Cas9-induced tdo-2 deletion mutants and identified a motif of three amino acids (PLD) that is required for the enzymatic conversion of tryptophan to N-formylkynurenine. Loss of TDO-2's enzymatic activity in PDL deletion mutants was accompanied by an increase in motility during aging and a prolonged lifespan, which is in line with the previously observed phenotypes induced by a knockdown of the full enzyme. Comparison of sequence structures suggests that blocking this motif might interfere with haem binding, which is essential for the enzyme's activity. The fact that these three residues are situated in an evolutionary conserved structural loop of the enzyme suggests that the findings can be translated to humans. The identification of this specific loop region in TDO-2-essential for its catalytic function-will aid in the design of novel inhibitors to treat diseases in which the TDO enzyme is overexpressed or hyperactive.