RESUMO
Drosophila melanogaster provides a powerful genetic model system in which to investigate the molecular mechanisms underlying neurodegenerative diseases. In this review, we discuss recent progress in Drosophila modeling Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), Huntington's Disease, Ataxia Telangiectasia, and neurodegeneration related to mitochondrial dysfunction or traumatic brain injury. We close by discussing recent progress using Drosophila models of neural regeneration and how these are likely to provide critical insights into future treatments for neurodegenerative disorders.
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Proteínas de Drosophila/genética , Predisposição Genética para Doença/genética , Doenças Neurodegenerativas/patologia , Animais , Animais Geneticamente Modificados , Modelos Animais de Doenças , Drosophila melanogaster , Humanos , Mutação , Regeneração Nervosa , Doenças Neurodegenerativas/genéticaRESUMO
Innate immunity is the first line of defense against invading pathogens and plays an essential role in defending the brain against infection, injury, and disease. It is currently well recognized that central nervous system (CNS) infections can result in long-lasting neurological sequelae and that innate immune and inflammatory reactions are highly implicated in the pathogenesis of neurodegeneration. Due to the conservation of the mechanisms that govern neural development and innate immune activation from flies to mammals, the lack of a classical adaptive immune system and the availability of numerous genetic and genomic tools, the fruit fly Drosophila melanogaster presents opportunities to investigate the cellular and molecular mechanisms associated with immune function in brain tissue and how they relate to infection, injury and neurodegenerative diseases. Here, we present an overview of currently identified innate immune mechanisms specific to the adult Drosophila brain.
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Encéfalo/imunologia , Imunidade Inata/imunologia , Animais , Autofagia/imunologia , Autofagia/fisiologia , Encéfalo/metabolismo , Drosophila , Imunidade Inata/fisiologia , Modelos Animais , Fagocitose/imunologia , Fagocitose/fisiologiaRESUMO
A growing body of evidence in humans implicates chronic activation of the innate immune response in the brain as a major cause of neuropathology in various neurodegenerative conditions, although the mechanisms remain unclear. In an unbiased genetic screen for mutants exhibiting neurodegeneration in Drosophila, we have recovered a mutation of dnr1 (defense repressor 1), a negative regulator of the Imd (immune deficiency) innate immune-response pathway. dnr1 mutants exhibit shortened lifespan and progressive, age-dependent neuropathology associated with activation of the Imd pathway and elevated expression of AMP (antimicrobial peptide) genes. To test the hypothesis that overactivation of innate immune-response pathways in the brain is responsible for neurodegeneration, we demonstrated that direct bacterial infection in the brain of wild-type flies also triggers neurodegeneration. In both cases, neurodegeneration is dependent on the NF-κB transcription factor, Relish. Moreover, we found that neural overexpression of individual AMP genes is sufficient to cause neurodegeneration. These results provide a mechanistic link between innate immune responses and neurodegeneration and may have important implications for the role of neuroinflammation in human neurodegenerative diseases as well.
Assuntos
Encéfalo/patologia , Proteínas de Drosophila/genética , Drosophila melanogaster/imunologia , Imunidade Inata , Mutação , Proteínas Repressoras/genética , Envelhecimento , Animais , Peptídeos Catiônicos Antimicrobianos/genética , Peptídeos Catiônicos Antimicrobianos/metabolismo , Apoptose , Infecções Bacterianas/genética , Infecções Bacterianas/imunologia , Encéfalo/imunologia , Encéfalo/microbiologia , Morte Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/microbiologia , Genótipo , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/imunologia , Doenças Neurodegenerativas/patologia , Neurônios/patologia , Fenótipo , Fatores de Transcrição/metabolismoRESUMO
UNLABELLED: Drosophila C virus (DCV) is a positive-sense RNA virus belonging to the Dicistroviridae family. This natural pathogen of the model organism Drosophila melanogaster is commonly used to investigate antiviral host defense in flies, which involves both RNA interference and inducible responses. Although lethality is used routinely as a readout for the efficiency of the antiviral immune response in these studies, virus-induced pathologies in flies still are poorly understood. Here, we characterize the pathogenesis associated with systemic DCV infection. Comparison of the transcriptome of flies infected with DCV or two other positive-sense RNA viruses, Flock House virus and Sindbis virus, reveals that DCV infection, unlike those of the other two viruses, represses the expression of a large number of genes. Several of these genes are expressed specifically in the midgut and also are repressed by starvation. We show that systemic DCV infection triggers a nutritional stress in Drosophila which results from intestinal obstruction with the accumulation of peritrophic matrix at the entry of the midgut and the accumulation of the food ingested in the crop, a blind muscular food storage organ. The related virus cricket paralysis virus (CrPV), which efficiently grows in Drosophila, does not trigger this pathology. We show that DCV, but not CrPV, infects the smooth muscles surrounding the crop, causing extensive cytopathology and strongly reducing the rate of contractions. We conclude that the pathogenesis associated with systemic DCV infection results from the tropism of the virus for an important organ within the foregut of dipteran insects, the crop. IMPORTANCE: DCV is one of the few identified natural viral pathogens affecting the model organism Drosophila melanogaster. As such, it is an important virus for the deciphering of host-virus interactions in insects. We characterize here the pathogenesis associated with DCV infection in flies and show that it results from the tropism of the virus for an essential but poorly characterized organ in the digestive tract, the crop. Our results may have relevance for other members of the Dicistroviridae, some of which are pathogenic to beneficial or pest insect species.
Assuntos
Dicistroviridae/crescimento & desenvolvimento , Drosophila melanogaster/virologia , Obstrução Intestinal/virologia , Animais , Dicistroviridae/fisiologia , Feminino , Trato Gastrointestinal/patologia , Trato Gastrointestinal/fisiopatologia , Trato Gastrointestinal/virologia , Perfilação da Expressão Gênica , Músculo Liso/virologia , Nodaviridae/crescimento & desenvolvimento , Sindbis virus/crescimento & desenvolvimento , Tropismo ViralRESUMO
The effects of the cellular environment on innate immunity remain poorly characterized. Here, we show that in Drosophila ATP-sensitive potassium channels (K(ATP)) mediate resistance to a cardiotropic RNA virus, Flock House virus (FHV). FHV viral load in the heart rapidly increases in K(ATP) mutant flies, leading to increased viremia and accelerated death. The effect of K(ATP) channels is dependent on the RNA interference genes Dcr-2, AGO2, and r2d2, indicating that an activity associated with this potassium channel participates in this antiviral pathway in Drosophila. Flies treated with the K(ATP) agonist drug pinacidil are protected against FHV infection, thus demonstrating the importance of this regulation of innate immunity by the cellular environment in the heart. In mice, the Coxsackievirus B3 replicates to higher titers in the hearts of mayday mutant animals, which are deficient in the Kir6.1 subunit of K(ATP) channels, than in controls. Together, our data suggest that K(ATP) channel deregulation can have a critical impact on innate antiviral immunity in the heart.
Assuntos
Drosophila/imunologia , Drosophila/virologia , Coração/virologia , Imunidade Inata/imunologia , Canais KATP/metabolismo , Nodaviridae/imunologia , Animais , Células HeLa , Humanos , Immunoblotting , Canais KATP/agonistas , Canais KATP/genética , Camundongos , Camundongos Endogâmicos C57BL , Nodaviridae/efeitos dos fármacos , Pinacidil/farmacologia , Interferência de RNA/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Tolbutamida , Carga Viral/imunologia , ViremiaRESUMO
Viral infection causes an increase in age-related intestinal pathologies. New research finds that oral viral infection leads to intestinal stem-cell proliferation and a decrease in lifespan in Drosophila melanogaster that depends on Sting-NF-κB signaling.
Assuntos
Envelhecimento , Drosophila melanogaster , NF-kappa B , Transdução de Sinais , Animais , NF-kappa B/metabolismo , Drosophila melanogaster/virologia , Drosophila melanogaster/fisiologia , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Intestinos/virologia , Viroses/metabolismo , Viroses/virologia , Viroses/imunologiaRESUMO
Drosophila melanogaster has been used extensively for dissecting the genetic and functional bases of host innate antiviral immunity and virus-induced pathology. Previous studies have shown that the presence of Wolbachia endosymbionts in D. melanogaster confers resistance to infection by certain viral pathogens. Zika virus is an important vector-borne pathogen that has recently expanded its range due to the wide geographical distribution of the mosquito vector. Here, we describe the effect of Wolbachia on the immune response of D. melanogaster adult flies following Zika virus infection. First, we show that the presence of Wolbachia endosymbionts promotes the longevity of uninfected D. melanogaster wild type adults and increases the survival response of flies following Zika virus injection. We find that the latter effect is more pronounced in females rather than in males. Then, we show that the presence of Wolbachia regulates Zika virus replication during Zika virus infection of female flies. In addition, we demonstrate that the antimicrobial peptide-encoding gene Drosocin and the sole Jun N-terminal kinase-specific MAPK phosphatase Puckered are upregulated in female adult flies, whereas the immune and stress response gene TotM is upregulated in male individuals. Finally, we find that the activity of RNA interference and Toll signaling remain unaffected in Zika virus-infected female and male adults containing Wolbachia compared to flies lacking the endosymbionts. Our results reveal that Wolbachia endosymbionts in D. melanogaster affect innate immune signaling activity in a sex-specific manner, which in turn influences host resistance to Zika virus infection. This information contributes to a better understanding of the complex interrelationship between insects, their endosymbiotic bacteria, and viral infection. Interpreting these processes will help us design more effective approaches for controlling insect vectors of infectious disease.
RESUMO
Severe neurological complications affecting brain growth and function have been well documented in newborn and adult patients infected by Zika virus (ZIKV), but the underlying mechanisms remain unknown. Here we use a Drosophila melanogaster mutant, cheesehead (chs), with a mutation in the brain tumor (brat) locus that exhibits both aberrant continued proliferation and progressive neurodegeneration in the adult brain. We report that temperature variability is a key driver of ZIKV pathogenesis, thereby altering host mortality and causing motor dysfunction in a sex-dependent manner. Furthermore, we show that ZIKV is largely localized to the brat chs brain and activates the RNAi and apoptotic immune responses. Our findings establish an in vivo model to study host innate immune responses and highlight the need of evaluating neurodegenerative deficits as a potential comorbidity in ZIKV-infected adults.
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Previous work in our laboratory has shown that mutations in prickle (pk) cause myoclonic-like seizures and ataxia in Drosophila, similar to what is observed in humans carrying mutations in orthologous PRICKLE genes. Here, we show that pk mutant brains show elevated, sustained neuronal cell death that correlates with increasing seizure penetrance, as well as an upregulation of mitochondrial oxidative stress and innate immune response (IIR) genes. Moreover, flies exhibiting more robust seizures show increased levels of IIR-associated target gene expression suggesting they may be linked. Genetic knockdown in glia of either arm of the IIR (Immune Deficiency [Imd] or Toll) leads to a reduction in neuronal death, which in turn suppresses seizure activity, with oxidative stress acting upstream of IIR. These data provide direct genetic evidence that oxidative stress in combination with glial-mediated IIR leads to progression of an epilepsy disorder.
Assuntos
Drosophila melanogaster , Epilepsia , Animais , Humanos , Regulação para Baixo , Drosophila melanogaster/genética , Convulsões/genética , Convulsões/metabolismo , Epilepsia/metabolismo , Neuroglia/metabolismo , Drosophila , Estresse Oxidativo , Imunidade Inata/genéticaRESUMO
Aging is accompanied by increased susceptibility to infections including with viral pathogens resulting in higher morbidity and mortality among the elderly. Significant changes in host metabolism can take place following virus infection. Efficient immune responses are energetically costly, and viruses divert host molecular resources to promote their own replication. Virus-induced metabolic reprogramming could impact infection outcomes, however, how this is affected by aging and impacts organismal survival remains poorly understood. RNA virus infection of Drosophila melanogaster with Flock House virus (FHV) is an effective model to study antiviral responses with age, where older flies die faster than younger flies due to impaired disease tolerance. Using this aged host-virus model, we conducted longitudinal, single-fly respirometry studies to determine if metabolism impacts infection outcomes. Analysis using linear mixed models on Oxygen Consumption Rate (OCR) following the first 72-hours post-infection showed that FHV modulates respiration, but age has no significant effect on OCR. However, the longitudinal assessment revealed that OCR in young flies progressively and significantly decreases, while OCR in aged flies remains constant throughout the three days of the experiment. Furthermore, we found that the OCR signature at 24-hours varied in response to both experimental treatment and survival status. FHV-injected flies that died prior to 48- or 72-hours measurements had a lower OCR compared to survivors at 48-hours. Our findings suggest the host's metabolic profile could influence the outcome of viral infections.
Assuntos
Nodaviridae , Vírus de RNA , Viroses , Animais , Masculino , Drosophila melanogaster/genética , Vírus de RNA/genética , Nodaviridae/genética , Consumo de OxigênioRESUMO
With emerging diseases on the rise, there is an urgent need to identify and understand novel mechanisms of prophylactic protection in vertebrate hosts. Inducing resistance against emerging pathogens through prophylaxis is an ideal management strategy that may impact pathogens and their host-associated microbiome. The host microbiome is recognized as a critical component of immunity, but the effects of prophylactic inoculation on the microbiome are unknown. In this study, we investigate the effects of prophylaxis on host microbiome composition, focusing on the selection of anti-pathogenic microbes contributing to host acquired immunity in a model host-fungal disease system, amphibian chytridiomycosis. We inoculated larval Pseudacris regilla against the fungal pathogen Batrachochytrium dendrobatidis (Bd) with a Bd metabolite-based prophylactic. Increased prophylactic concentration and exposure duration were associated with significant increases in proportions of putatively Bd-inhibitory host-associated bacterial taxa, indicating a protective prophylactic-induced shift towards microbiome members that are antagonistic to Bd. Our findings are in accordance with the adaptive microbiome hypothesis, where exposure to a pathogen alters the microbiome to better cope with subsequent pathogen encounters. Our study advances research on the temporal dynamics of microbiome memory and the role of prophylaxis-induced shifts in microbiomes contributing to prophylaxis effectiveness. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Anuros , Microbiota , Animais , Pele , Larva , Modelos BiológicosRESUMO
Ranges of tardigrade intraspecific and interspecific variability are not precisely defined, both in terms of morphology and genetics, rendering descriptions of new taxa a cumbersome task. This contribution enhances the morphological and molecular dataset available for the heterotardigrade genus Viridiscus by supplying new information on Southern Nearctic populations of V. perviridis, V. viridianus, and a new species from Tennessee. We demonstrate that, putting aside already well-documented cases of significant variability in chaetotaxy, the dorsal plate sculpturing and other useful diagnostic characters, such as morphology of clavae and pedal platelets, may also be more phenotypically plastic characters at the species level than previously assumed. As a result of our integrative analyses, V. viridianus is redescribed, V. celatus sp. nov. described, and V. clavispinosus designated as nomen inquirendum, and its junior synonymy with regard to V. viridianus suggested. Morphs of three Viridiscus species (V. perviridis, V. viridianus, and V. viridissimus) are depicted, and the implications for general echiniscid taxonomy are drawn. We emphasise that taxonomic conclusions reached solely through morphological or molecular analyses lead to a distorted view on tardigrade α-diversity.
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Tardígrados , Animais , Tardígrados/genética , Filogenia , TennesseeRESUMO
The family of Toll-like receptors plays an essential role in the induction of the immune response. These receptors sense the presence of microbial ligands and activate the nuclear factor-κB transcription factor. We review the key studies that led from the formulation of the concept of pattern recognition receptors to the characterization of Toll-like receptors, insisting on the important role played by the model organism Drosophila melanogaster and on the increasing evidence connecting these receptors to cardiovascular disease.
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Receptores Toll-Like/fisiologia , Animais , Doenças Cardiovasculares/imunologia , Proteínas de Drosophila/história , Proteínas de Drosophila/imunologia , Drosophila melanogaster/imunologia , Drosophila melanogaster/metabolismo , História do Século XX , História do Século XXI , Interações Hospedeiro-Patógeno/imunologia , Humanos , Imunidade Inata , Macrófagos/imunologia , Receptores Toll-Like/históriaRESUMO
MicroRNAs (miRNAs) are a class of small non-coding RNAs ~19-22 nt long which post-transcriptionally regulate gene expression. Their ability to exhibit dynamic expression patterns coupled with their wide variety of targets allows miRNAs to regulate many processes, including the innate immune response of Drosophila melanogaster. Recent studies have identified miRNAs in Drosophila which are differentially expressed during infection with different pathogens as well as miRNAs that may affect immune signalling when differentially expressed. This review provides an overview of miRNAswhich have been identified to play a role in the immune response of Drosophila through targeting of the Toll and IMD signalling pathways and other immune processes. It will also explore the role of miRNAs in fine-tuning the immune response in Drosophila and highlight current gaps in knowledge regarding the role of miRNAs in immunity and areas for further research.
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Proteínas de Drosophila , MicroRNAs , Animais , Drosophila/genética , MicroRNAs/genética , Drosophila melanogaster/metabolismo , Imunidade Inata/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismoRESUMO
Genetic analysis of the drosophila antiviral response indicates that RNA interference plays a major role in the control of viral infections. This involves the sensing of viral double stranded RNA by Dicer-2, which generates 21nt small interfering (si)RNAs. These siRNAs are then loaded onto the effector enzyme Argonaute-2, and guides towards RNA molecules containing complementary sequences. An inducible antiviral response also contributes to the control of viral infections in drosophila, and involves the NF-_B pathways Toll and IMD, as well as the JAK/STAT signaling pathway. The effector molecules regulated by these pathways, as well as the sensors of viral infection triggering them remain poorly characterized. In spite of these uncertainties, it is nowwell-established that drosophila is a powerful model to decipher evolutionary conserved mechanisms of antiviral host-defense, in particular in mosquito vectors of arboviruses.
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This review outlines the known cellular pathways and mechanisms involved in Drosophila age-dependent immunity to pathogenic microorganisms such as bacteria and fungi. We discuss the implication of host signaling pathways such as the Toll, Immune Deficiency (IMD), Janus kinase signal transducer and activator of transcription (JAK/STAT), and Insulin/Insulin Growth Factor/Target of Rapamycin (IIS/TOR) on immune function with aging. Additionally, we review the effects that factors such as sexual dimorphism, environmental stress, and cellular physiology exert on age-dependent immunity in Drosophila. We discuss potential tradeoffs between heightened immune function and longevity in the absence of infection, and we provide detailed tables outlining the various assays and pathogens used in the cited studies, as well as the age, sex, and strains of Drosophila used. We also discuss the overlapping effects these pathways and mechanisms have on one another. We highlight the great utility of Drosophila as a model organism and the importance of a greater focus on age-dependent antiviral immunity for future studies.
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Advanced age in humans is associated with greater susceptibility to and higher mortality rates from infections, including infections with some RNA viruses. The underlying innate immune mechanisms, which represent the first line of defense against pathogens, remain incompletely understood. Drosophila melanogaster is able to mount potent and evolutionarily conserved innate immune defenses against a variety of microorganisms including viruses and serves as an excellent model organism for studying host-pathogen interactions. With its relatively short lifespan, Drosophila also is an organism of choice for aging studies. Despite numerous advantages that this model offers, Drosophila has not been used to its full potential to investigate the response of the aged host to viral infection. Here, we show that, in comparison to younger flies, aged Drosophila succumb more rapidly to infection with the RNA-containing Flock House virus due to an age-dependent defect in disease tolerance. Relative to younger individuals, we find that older Drosophila mount transcriptional responses characterized by differential regulation of more genes and genes regulated to a greater extent. We show that loss of disease tolerance to Flock House virus with age associates with a stronger regulation of genes involved in apoptosis, some genes of the Drosophila immune deficiency NF-kB pathway, and genes whose products function in mitochondria and mitochondrial respiration. Our work shows that Drosophila can serve as a model to investigate host-virus interactions during aging and furthermore sets the stage for future analysis of the age-dependent mechanisms that govern survival and control of virus infections at older age.
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Envelhecimento , Nodaviridae , Infecções por Vírus de RNA , Animais , Drosophila melanogaster/genética , Infecções por Vírus de RNA/genéticaRESUMO
Parkinson's disease (PD) is a progressive, neurodegenerative movement disorder characterized by the loss of dopaminergic (DA) neurons. Limited understanding of the early molecular pathways associated with the demise of DA neurons, including those of inflammatory exacerbation of neurodegeneration, is a major impediment to therapeutic development. Recent studies have implicated gene-environment interactions in PD susceptibility. We used transcriptomic profiling in a Drosophila PD model in response to paraquat (PQ)-induced oxidative stress to identify pre-symptomatic signatures of impending neuron dysfunction. Our RNAseq data analysis revealed extensive regulation of innate immune response genes following PQ ingestion. We found that PQ exposure leads to the activation of the NF-κB transcription factor, Relish, and the stress signaling factor JNK, encoded by the gene basket in Drosophila. Relish knockdown in the dopaminergic neurons confers PQ resistance and rescues mobility defects and DA neuron loss. Furthermore, PQ-induced toxicity is mediated through the immune deficiency signaling pathway. Surprisingly, the expression of Relish-dependent anti-microbial peptide (AMPs) genes is suppressed upon PQ exposure causing increased sensitivity to Gram-negative bacterial infection. This work provides a novel link between PQ exposure and innate immune system modulation underlying environmental toxin-induced neurodegeneration, thereby underscoring the role of the innate immune system in PD pathogenesis.
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Perfilação da Expressão Gênica , Imunidade Inata , Paraquat/toxicidade , Doença de Parkinson Secundária , Transdução de Sinais/imunologia , Animais , Proteínas de Drosophila , Drosophila melanogaster , Humanos , Doença de Parkinson Secundária/induzido quimicamente , Doença de Parkinson Secundária/imunologia , Transdução de Sinais/efeitos dos fármacosRESUMO
There is much to understand about the onset and progression of neurodegenerative diseases, including the underlying genes responsible. Forward genetic screening using chemical mutagens is a useful strategy for mapping mutant phenotypes to genes among Drosophila and other model organisms that share conserved cellular pathways with humans. If the mutated gene of interest is not lethal in early developmental stages of flies, a climbing assay can be conducted to screen for phenotypic indicators of decreased brain functioning, such as low climbing rates. Subsequently, secondary histological analysis of brain tissue can be performed in order to verify the neuroprotective function of the gene by scoring neurodegeneration phenotypes. Gene mapping strategies include meiotic and deficiency mapping that rely on these same assays can be followed by DNA sequencing to identify possible nucleotide changes in the gene of interest.
Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Animais , Humanos , NeuroproteçãoRESUMO
Increasing body of evidence indicates that proper glial function plays an important role in neuroprotection and in organismal physiology throughout lifespan. Work done in the model organism Drosophila melanogaster has revealed important aspects of glial cell biology in the contexts of longevity and neurodegeneration. In this mini review, we summarize recent findings from work done in the fruit fly Drosophila about the role of glia in maintaining a healthy status during animal's life and discuss the involvement of glial innate immune pathways in lifespan and neurodegeneration. Overactive nuclear factor kappa B (NF-κB) pathways and defective phagocytosis appear to be major contributors to lifespan shortening and neuropathology. Glial NF-κB silencing on the other hand, extends lifespan possibly through an immune-neuroendocrine axis. Given the evolutionary conservation of NF-κB innate immune signaling and of macrophage ontogeny across fruit flies, rodents, and humans, the above observations in glia could potentially support efforts for therapeutic interventions targeting to ameliorate age-related pathologies.