ABSTRACT
Insects are established models for understanding host-pathogen interactions and innate immune mechanisms. The innate immune system in insects is highly efficient in recognizing and opposing pathogens that cause detrimental effects during infection. The cuticular layer which covers the superficial layer of the insect body participates in host defense and wound healing by inducing innate immune responses. Previous studies have started to address the involvement of cuticular genes in conferring resistance to insect pathogens, particularly those that infect by disrupting the insect cuticle. For example, the cuticular gene Transglutaminase (TG) in Drosophila melanogaster plays a structural role in cuticle formation and blood coagulation and also possesses immune properties against pathogenic infection. However, more information is becoming available about the immune function of other cuticular gene families in insects. In this review, we aim to highlight the recent advances in insect cuticular immunity and address the necessity of pursuing further research to fill the existing gaps in this important field of insect immunology. This information will lead to novel strategies for the efficient management of agricultural insect pests and vectors of plant and human disease.
Subject(s)
Immunity, Innate , Insecta , Animals , Insecta/immunology , Insecta/genetics , Immunity, Innate/genetics , Host-Pathogen Interactions/immunology , Host-Pathogen Interactions/genetics , Insect Proteins/genetics , Insect Proteins/immunology , Insect Proteins/metabolism , Drosophila melanogaster/immunology , Drosophila melanogaster/genetics , Drosophila melanogaster/microbiologyABSTRACT
Cell death is an important process in the body, as it occurs throughout every tissue during development, disease, and tissue regeneration. Phagocytes are responsible for clearing away dying cells and are typically characterized as either professional or nonprofessional phagocytes. Professional phagocytes, such as macrophages, are found in nearly every part of the body while nonprofessional phagocytes, such as epithelial cells, are found in every tissue type. However, there are organs that are considered "immune-privileged" as they have little to no immune surveillance and rely on nonprofessional phagocytes to engulf dying cells. These organs are surrounded by barriers to protect the tissue from viruses, bacteria, and perhaps even immune cells. The Drosophila ovary is considered immune-privileged, however the presence of hemocytes, the macrophages of Drosophila, around the ovary suggests they may have a potential function. Here we analyze hemocyte localization and potential functions in response to starvation-induced cell death in the ovary. Hemocytes were found to accumulate in the oviduct in the vicinity of mature eggs and follicle cell debris. Genetic ablation of hemocytes revealed that the presence of hemocytes affects oogenesis and that they phagocytose ovarian cell debris and in their absence fecundity decreases. Unpaired3, an IL-6 like cytokine, was found to be required for the recruitment of hemocytes to the oviduct to clear away obsolete follicle cells. These findings demonstrate a role for hemocytes in the ovary, providing a more thorough understanding of phagocyte communication and cell clearance in a previously thought immune-privileged organ.
Subject(s)
Hemocytes , Ovary , Phagocytes , Phagocytosis , Animals , Female , Ovary/immunology , Hemocytes/immunology , Phagocytes/immunology , Phagocytes/metabolism , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Drosophila melanogaster/immunology , Oogenesis , Drosophila/immunologyABSTRACT
Tauopathies are a group of neurodegenerative diseases characterized by the presence of tau inclusions. We have developed over fifty anti-tau single-domain antibodies (sdAbs) derived from phage display libraries of a llama immunized with recombinant and pathological tau immunogens. We examined the therapeutic potential of four of these sdAbs in a Drosophila tauopathy model following their transgenic expression either in all neurons or neuronal subtypes. Three of these sdAbs showed therapeutic potential in various assays, effectively clearing pathological tau and attenuating or preventing tau-induced phenotypes that typically manifest as defects in neuronal axonal transport, neurodegeneration, functional impairments, and shortened lifespan. Of these three, one sdAb was superior in every assay, which may at least in part be attributed to its tau-binding epitope. These findings support its development as a gene therapy for tauopathies.
Subject(s)
Single-Domain Antibodies , Tauopathies , tau Proteins , tau Proteins/metabolism , tau Proteins/immunology , Animals , Tauopathies/immunology , Tauopathies/pathology , Single-Domain Antibodies/immunology , Single-Domain Antibodies/pharmacology , Humans , Disease Models, Animal , Drosophila , Animals, Genetically Modified , Neurons/metabolism , Neurons/pathology , Camelids, New World/immunology , Drosophila melanogaster/immunologyABSTRACT
Infections and neurodegenerative diseases induce neuroinflammation, but affected individuals often show nonneural symptoms including muscle pain and muscle fatigue. The molecular pathways by which neuroinflammation causes pathologies outside the central nervous system (CNS) are poorly understood. We developed multiple models to investigate the impact of CNS stressors on motor function and found that Escherichia coli infections and SARS-CoV-2 protein expression caused reactive oxygen species (ROS) to accumulate in the brain. ROS induced expression of the cytokine Unpaired 3 (Upd3) in Drosophila and its ortholog, IL-6, in mice. CNS-derived Upd3/IL-6 activated the JAK-STAT pathway in skeletal muscle, which caused muscle mitochondrial dysfunction and impaired motor function. We observed similar phenotypes after expressing toxic amyloid-ß (Aß42) in the CNS. Infection and chronic disease therefore activate a systemic brain-muscle signaling axis in which CNS-derived cytokines bypass the connectome and directly regulate muscle physiology, highlighting IL-6 as a therapeutic target to treat disease-associated muscle dysfunction.
Subject(s)
Brain , COVID-19 , Muscle, Skeletal , Signal Transduction , Animals , Brain/immunology , Brain/metabolism , Signal Transduction/immunology , Mice , Muscle, Skeletal/immunology , Muscle, Skeletal/metabolism , COVID-19/immunology , Chronic Disease , Interleukin-6/metabolism , Interleukin-6/immunology , Escherichia coli Infections/immunology , Reactive Oxygen Species/metabolism , Reactive Oxygen Species/immunology , Drosophila Proteins/metabolism , Drosophila Proteins/immunology , Drosophila Proteins/genetics , SARS-CoV-2/immunology , Drosophila melanogaster/immunology , Amyloid beta-Peptides/metabolism , Humans , Mice, Inbred C57BLABSTRACT
Stimulator of interferon genes (STING) mediates innate immune response upon binding to cyclic GMP-AMP (cGAMP). It recruits tank-binding kinase 1 (TBK1) and transcription factor interferon regulatory factor 3 (IRF3) through its C-terminal tail and facilitates TBK1-dependent phosphorylation of IRF3 via forming STING polymers in mammalian cells. However, the mechanism behind STING-mediated activation of NF-κB transcription factor, Relish, in insect cells is unknown. Our study revealed that insect STING formed oligomers and the cryptic RIP homotypic interaction motif (cRHIM) was required for its oligomerization and its anti-viral functions. Cells expressing cRHIM-deficient mutants exhibited lower levels of anti-viral molecules, higher viral load after viral infection and weak activation of Relish. Moreover, we observed that under cGAMP stimulation, insect STING interacted with IMD, and deletion of the cRHIM motif on either protein prevented this interaction. Finally, we demonstrated that cGAMP enhanced the amyloid-like property of insect STING aggregates by ThT staining. In summary, our research showed that insect STING employed a homotypic motif to form intermolecular interactions that are essential for its antiviral signaling.
Subject(s)
Immunity, Innate , Interferon Regulatory Factor-3 , Membrane Proteins , Signal Transduction , Animals , Membrane Proteins/metabolism , Membrane Proteins/genetics , Signal Transduction/immunology , Interferon Regulatory Factor-3/metabolism , Interferon Regulatory Factor-3/genetics , Nucleotides, Cyclic/metabolism , Protein Serine-Threonine Kinases/metabolism , Protein Serine-Threonine Kinases/genetics , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Transcription Factors/metabolism , Transcription Factors/genetics , Amino Acid Motifs/genetics , Humans , Cell Line , Protein Binding , Phosphorylation , Protein Multimerization , Drosophila melanogaster/immunology , Drosophila melanogaster/virologyABSTRACT
Despite impressive advances in the broad field of innate immunity, our understanding of the molecules and signaling pathways that control the host immune response to nematode infection remains incomplete. We have shown recently that Transforming Growth Factor-ß (TGF-ß) signaling in the fruit fly Drosophila melanogaster is activated by nematode infection and certain TGF-ß superfamily members regulate the D. melanogaster anti-nematode immune response. Here, we investigate the effect of an entomopathogenic nematode infection factor on host TGF-ß pathway regulation and immune function. We find that Heterorhabditis bacteriophora serine carboxypeptidase activates the Activin branch in D. melanogaster adults and the immune deficiency pathway in Activin-deficient flies, it affects hemocyte numbers and survival in flies deficient for Activin signaling, and causes increased intestinal steatosis in Activin-deficient flies. Thus, insights into the D. melanogaster signaling pathways and metabolic processes interacting with H. bacteriophora pathogenicity factors will be applicable to entomopathogenic nematode infection of important agricultural insect pests and vectors of disease.
Subject(s)
Drosophila Proteins , Drosophila melanogaster , Lipid Metabolism , Signal Transduction , Animals , Drosophila melanogaster/parasitology , Drosophila melanogaster/immunology , Drosophila melanogaster/metabolism , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Carboxypeptidases/metabolism , Carboxypeptidases/genetics , Activins/metabolism , Transforming Growth Factor beta/metabolism , Rhabditida/physiology , Immunity, Innate , Carrier ProteinsABSTRACT
Microbial pathogenicity often depends on the route of infection. For instance, P. aeruginosa or S. marcescens cause acute systemic infections when low numbers of bacteria are injected into D. melanogaster flies whereas flies succumb much slower to the continuous ingestion of these pathogens, even though both manage to escape from the gut compartment and reach the hemocoel. Here, we have developed a latent P. aeruginosa infection model by feeding flies on the bacteria for a short period. The bacteria stably colonize internal tissues yet hardly cause any damage since latently-infected flies live almost as long as noninfected control flies. The apparently dormant bacteria display particular characteristics in terms of bacterial colony morphology, composition of the outer cell wall, and motility. The virulence of these bacteria can however be reactivated upon wounding the host. We show that melanization but not the cellular or the systemic humoral response is the predominant host defense that establishes latency and may coerce the bacteria to a dormant state. In addition, the lasting activation of the melanization responses in latently-infected flies provides a degree of protection to the host against a secondary fungal infection. Latent infection by an ingested pathogen protects against a variety of homologous or heterologous systemic secondary infectious challenges, a situation previously described for the endosymbiotic Wolbachia bacteria, a guard against viral infections.
Subject(s)
Drosophila melanogaster , Immunity, Innate , Pseudomonas Infections , Pseudomonas aeruginosa , Animals , Drosophila melanogaster/microbiology , Drosophila melanogaster/immunology , Pseudomonas aeruginosa/pathogenicity , Pseudomonas aeruginosa/immunology , Pseudomonas Infections/immunology , Pseudomonas Infections/microbiology , Virulence , Disease Models, Animal , Host-Pathogen Interactions/immunologyABSTRACT
Invertebrates lack the immune machinery underlying vertebrate-like acquired immunity. However, in many insects past infection by the same pathogen can 'prime' the immune response, resulting in improved survival upon reinfection. Here, we investigated the mechanistic basis and epidemiological consequences of innate immune priming in the fruit fly Drosophila melanogaster when infected with the gram-negative bacterial pathogen Providencia rettgeri. We find that priming in response to P. rettgeri infection is a long-lasting and sexually dimorphic response. We further explore the epidemiological consequences of immune priming and find it has the potential to curtail pathogen transmission by reducing pathogen shedding and spread. The enhanced survival of individuals previously exposed to a non-lethal bacterial inoculum coincided with a transient decrease in bacterial loads, and we provide strong evidence that the effect of priming requires the IMD-responsive antimicrobial-peptide Diptericin-B in the fat body. Further, we show that while Diptericin B is the main effector of bacterial clearance, it is not sufficient for immune priming, which requires regulation of IMD by peptidoglycan recognition proteins. This work underscores the plasticity and complexity of invertebrate responses to infection, providing novel experimental evidence for the effects of innate immune priming on population-level epidemiological outcomes.
Subject(s)
Drosophila Proteins , Drosophila melanogaster , Immunity, Innate , Providencia , Animals , Drosophila melanogaster/microbiology , Drosophila melanogaster/immunology , Providencia/immunology , Drosophila Proteins/immunology , Female , Male , Enterobacteriaceae Infections/immunology , Enterobacteriaceae Infections/transmission , Antimicrobial PeptidesABSTRACT
Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRRs) that recognize invading pathogens and activate downstream signaling pathways. The number of 10 Tolls is found in Litopenaeus vannamei but have not yet been identified as the corresponding Toll homologue of model animal. In this study, we predicted the three-dimensional (3D) structures of 10 LvTolls (LvToll1-10) with AlphaFold2 program. The per-residue local distance difference test (pLDDT) scores of LvTolls showed the predicted structure of LvTolls had high accuracy (pLDDT>70). By structural analysis, 3D structures of LvToll2 and LvToll3 had high similarity with Drosophila melanogaster Toll and Toll7, respectively. 3D structure of LvToll7 and LvToll10 were not similar to that of other LvTolls. Moreover, we also predicted that LvSpätzle4 had high structural similarity to DmSpätzle. There were 9 potential hydrogen bonds in LvToll2-LvSpätzle4 complex. Importantly, co-immunoprecipitation assay showed that LvToll2 could bind with LvSpätzle4. Collectively, this study provides new insight for researching invertebrate immunity by identifying the protein of model animal homologue.
Subject(s)
Penaeidae , Toll-Like Receptors , Animals , Penaeidae/immunology , Toll-Like Receptors/metabolism , Toll-Like Receptors/genetics , Drosophila melanogaster/immunology , Insect Proteins/metabolism , Insect Proteins/genetics , Models, Molecular , Amino Acid Sequence , Immunity, Innate , Protein Binding , Phylogeny , Signal Transduction , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Protein ConformationABSTRACT
Facultative endosymbiotic bacteria, such as Wolbachia and Spiroplasma species, are commonly found in association with insects and can dramatically alter their host physiology. Many endosymbionts are defensive and protect their hosts against parasites or pathogens. Despite the widespread nature of defensive insect symbioses and their importance for the ecology and evolution of insects, the mechanisms of symbiont-mediated host protection remain poorly characterized. Here, we utilized the fruit fly Drosophila melanogaster and its facultative endosymbiont Spiroplasma poulsonii to characterize the mechanisms underlying symbiont-mediated host protection against bacterial and fungal pathogens. Our results indicate a variable effect of S. poulsonii on infection outcome, with endosymbiont-harboring flies being more resistant to Rhyzopus oryzae, Staphylococcus aureus, and Providencia alcalifaciens but more sensitive or as sensitive as endosymbiont-free flies to the infections with Pseudomonas species. Further focusing on the protective effect, we identified Transferrin-mediated iron sequestration induced by Spiroplasma as being crucial for the defense against R. oryzae and P. alcalifaciens. In the case of S. aureus, enhanced melanization in Spiroplasma-harboring flies plays a major role in protection. Both iron sequestration and melanization induced by Spiroplasma require the host immune sensor protease Persephone, suggesting a role of proteases secreted by the symbiont in the activation of host defense reactions. Hence, our work reveals a broader defensive range of Spiroplasma than previously appreciated and adds nutritional immunity and melanization to the defensive arsenal of symbionts. IMPORTANCE: Defensive endosymbiotic bacteria conferring protection to their hosts against parasites and pathogens are widespread in insect populations. However, the mechanisms by which most symbionts confer protection are not fully understood. Here, we studied the mechanisms of protection against bacterial and fungal pathogens mediated by the Drosophila melanogaster endosymbiont Spiroplasma poulsonii. We demonstrate that besides the previously described protection against wasps and nematodes, Spiroplasma also confers increased resistance to pathogenic bacteria and fungi. We identified Spiroplasma-induced iron sequestration and melanization as key defense mechanisms. Our work broadens the known defense spectrum of Spiroplasma and reveals a previously unappreciated role of melanization and iron sequestration in endosymbiont-mediated host protection. We propose that the mechanisms we have identified here may be of broader significance and could apply to other endosymbionts, particularly to Wolbachia, and potentially explain their protective properties.
Subject(s)
Drosophila melanogaster , Iron , Spiroplasma , Symbiosis , Animals , Spiroplasma/physiology , Drosophila melanogaster/microbiology , Drosophila melanogaster/immunology , Iron/metabolism , Melanins/metabolism , Staphylococcus aureus/physiology , Staphylococcus aureus/immunology , Providencia/metabolism , Providencia/physiology , Providencia/genetics , Disease ResistanceABSTRACT
Insect respiration has long been thought to be solely dependent on an elaborate tracheal system without assistance from the circulatory system or immune cells1,2. Here we describe that Drosophila crystal cells-myeloid-like immune cells called haemocytes-control respiration by oxygenating Prophenoloxidase 2 (PPO2) proteins. Crystal cells direct the movement of haemocytes between the trachea of the larval body wall and the circulation to collect oxygen. Aided by copper and a neutral pH, oxygen is trapped in the crystalline structures of PPO2 in crystal cells. Conversely, PPO2 crystals can be dissolved when carbonic anhydrase lowers the intracellular pH and then reassembled into crystals in cellulo by adhering to the trachea. Physiologically, larvae lacking crystal cells or PPO2, or those expressing a copper-binding mutant of PPO2, display hypoxic responses under normoxic conditions and are susceptible to hypoxia. These hypoxic phenotypes can be rescued by hyperoxia, expression of arthropod haemocyanin or prevention of larval burrowing activity to expose their respiratory organs. Thus, we propose that insect immune cells collaborate with the tracheal system to reserve and transport oxygen through the phase transition of PPO2 crystals, facilitating internal oxygen homeostasis in a process that is comparable to vertebrate respiration.
Subject(s)
Catechol Oxidase , Drosophila Proteins , Drosophila melanogaster , Enzyme Precursors , Hemocytes , Oxygen , Phase Transition , Respiration , Animals , Female , Male , Biological Transport , Carbonic Anhydrases/metabolism , Catechol Oxidase/metabolism , Copper/metabolism , Crystallization , Drosophila melanogaster/anatomy & histology , Drosophila melanogaster/cytology , Drosophila melanogaster/enzymology , Drosophila melanogaster/immunology , Drosophila melanogaster/metabolism , Drosophila Proteins/metabolism , Enzyme Precursors/metabolism , Hemocyanins/metabolism , Hemocytes/immunology , Hemocytes/metabolism , Homeostasis , Hydrogen-Ion Concentration , Hyperoxia/metabolism , Hypoxia/metabolism , Larva/anatomy & histology , Larva/cytology , Larva/immunology , Larva/metabolism , Oxygen/metabolismABSTRACT
The dysregulation of intensity and duration in innate immunity can result in detrimental effects on the body, emphasizing the crucial need for precise regulation. However, the intricate and accurate nature of innate immunity implies the existence of numerous undiscovered innate immunomodulators, particularly transcription factors. In this study, we have identified a Drosophila C2H2 zinc finger protein CG18262, named Immune-mediated Zinc Finger protein (IMZF), capable of suppressing immune responses of Imd pathway. Mechanistically, IMZF serves as a transcription factor that represses the expression of Imd and Tak1. Intriguingly, our findings also reveal that Relish, an NF-κB transcription factor, positively regulates the expression of IMZF, consequently inhibiting the activation of Imd and Tak1 to prevent an exaggerated immune response. Additionally, we have elucidated the pivotal role played by the Relish-IMZF-Imd/Tak1 axis in restoring immune homeostasis of Drosophila Imd pathway. In summary, our findings not only unveil a novel C2H2 zinc finger immunoregulatory transcription factor, IMZF, along with its specific mechanism of immune regulation, but also shed light on the dual functionality of Relish in different stages of the immune response by modulating distinct effectors. This discovery provides new insights and enlightenment into the complex regulation of Drosophila innate immunity.
Subject(s)
Drosophila Proteins , Homeostasis , Immunity, Innate , MAP Kinase Kinase Kinases , Transcription Factors , Animals , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Transcription Factors/metabolism , Transcription Factors/genetics , MAP Kinase Kinase Kinases/metabolism , MAP Kinase Kinase Kinases/genetics , Drosophila melanogaster/immunology , Drosophila melanogaster/metabolism , Drosophila melanogaster/genetics , Drosophila/metabolism , Drosophila/genetics , Drosophila/immunology , Zinc FingersABSTRACT
MicroRNAs (miRNAs) play crucial regulatory roles in controlling immune responses, but their dynamic expression mechanisms are poorly understood. Here, we firstly confirm that the conserved miRNA miR-210 negatively regulates innate immune responses of Drosophila and human via targeting Toll and TLR6, respectively. Secondly, our findings demonstrate that the expression of miR-210 is dynamically regulated by NF-κB factor Dorsal in immune response of Drosophila Toll pathway. Thirdly, we find that Dorsal-mediated transcriptional inhibition of miR-210 is dependent on the transcriptional repressor Su(Hw). Mechanistically, Dorsal interacts with Su(Hw) to modulate cooperatively the dynamic expression of miR-210 in a time- and dose-dependent manner, thereby controlling the strength of Drosophila Toll immune response and maintaining immune homeostasis. Fourthly, we reveal a similar mechanism in human cells, where NF-κB/RelA cooperates with E4F1 to regulate the dynamic expression of hsa-miR-210 in the TLR immune response. Overall, our study reveals a conservative regulatory mechanism that maintains animal innate immune homeostasis and provides new insights into the dynamic regulation of miRNA expression in immune response.
Subject(s)
Drosophila Proteins , Immunity, Innate , MicroRNAs , Transcription Factors , MicroRNAs/genetics , MicroRNAs/metabolism , Animals , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Humans , Immunity, Innate/genetics , Transcription Factors/metabolism , Transcription Factors/genetics , Gene Expression Regulation , Drosophila melanogaster/genetics , Drosophila melanogaster/immunology , NF-kappa B/metabolism , Toll-Like Receptor 6/genetics , Toll-Like Receptor 6/metabolism , Transcription Factor RelA/metabolism , Transcription Factor RelA/genetics , Repressor Proteins/metabolism , Repressor Proteins/genetics , Signal Transduction , Cell Line , Drosophila/genetics , Drosophila/immunology , Toll-Like Receptors/genetics , Toll-Like Receptors/metabolism , Nuclear Proteins , PhosphoproteinsABSTRACT
Currently, insecticides that target nicotinic acetylcholine receptors (nAChR) are widely used. Studies on the sublethal effects of insecticides have found that they can affect the amount of virus in insects. The mechanism by which insecticides affect insect virus load remain unclear. Here, we show that nAChR targeting insecticide can affect viral replication through the immune deficiency (IMD) pathway. We demonstrate that a low dose of spinosad (6.8 ng/mL), acting as an antagonist to Drosophila melanogaster nicotinic acetylcholine receptor α6 (Dα6), significantly elevates Drosophila melanogaster sigmavirus (DMelSV) virus titers in adults of Drosophila melanogaster. Conversely, a high dose of spinosad (50 ng/mL), acting as an agonist to Dα6, substantially decreases viral load. This bidirectional regulation of virus levels is absent in Dα6-knockout flies, signifying the specificity of spinosad's action through Dα6. Furthermore, the knockdown of Dα6 results in decreased expression of genes in the IMD pathway, including dredd, imd, relish, and downstream antimicrobial peptide genes AttA and AttB, indicating a reduced innate immune response. Subsequent investigations reveal no significant difference in viral titers between relish mutant flies and Dα6-relish double mutants, suggesting that the IMD pathway's role in antiviral defense is dependent on Dα6. Collectively, our findings shed light on the intricate interplay between nAChR signaling and the IMD pathway in mediating antiviral immunity, highlighting the potential for nAChR-targeting compounds to inadvertently influence viral dynamics in insect hosts. This knowledge may inform the development of integrated pest management strategies that consider the broader ecological impact of insecticide use.
Subject(s)
Drosophila Proteins , Drosophila melanogaster , Receptors, Nicotinic , Animals , Drosophila melanogaster/immunology , Drosophila melanogaster/virology , Receptors, Nicotinic/metabolism , Receptors, Nicotinic/genetics , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Drug Combinations , Macrolides/pharmacology , Virus Replication/drug effects , Immunity, Innate , Insecticides/pharmacology , Viral Load/drug effects , Signal TransductionABSTRACT
BACKGROUND: Innate immune responses can be activated by pathogen-associated molecular patterns (PAMPs), danger signals released by damaged tissues, or the absence of self-molecules that inhibit immunity. As PAMPs are typically conserved across broad groups of pathogens but absent from the host, it is unclear whether they allow hosts to recognize parasites that are phylogenetically similar to themselves, such as parasitoid wasps infecting insects. RESULTS: Parasitoids must penetrate the cuticle of Drosophila larvae to inject their eggs. In line with previous results, we found that the danger signal of wounding triggers the differentiation of specialized immune cells called lamellocytes. However, using oil droplets to mimic infection by a parasitoid wasp egg, we found that this does not activate the melanization response. This aspect of the immune response also requires exposure to parasite molecules. The unidentified factor enhances the transcriptional response in hemocytes and induces a specific response in the fat body. CONCLUSIONS: We conclude that a combination of danger signals and the recognition of nonself molecules is required to activate Drosophila's immune response against parasitic insects.
Subject(s)
Hemocytes , Host-Parasite Interactions , Immunity, Innate , Wasps , Animals , Wasps/physiology , Host-Parasite Interactions/immunology , Hemocytes/immunology , Drosophila melanogaster/parasitology , Drosophila melanogaster/immunology , Drosophila melanogaster/physiology , Larva/immunology , Larva/parasitology , Drosophila/parasitology , Drosophila/immunologyABSTRACT
BACKGROUND: Spinal muscular atrophy (SMA) is a devastating neuromuscular disease caused by hypomorphic loss of function in the survival motor neuron (SMN) protein. SMA presents across a broad spectrum of disease severity. Unfortunately, genetic models of intermediate SMA have been difficult to generate in vertebrates and are thus unable to address key aspects of disease etiology. To address these issues, we developed a Drosophila model system that recapitulates the full range of SMA severity, allowing studies of pre-onset biology as well as late-stage disease processes. RESULTS: Here, we carried out transcriptomic and proteomic profiling of mild and intermediate Drosophila models of SMA to elucidate molecules and pathways that contribute to the disease. Using this approach, we elaborated a role for the SMN complex in the regulation of innate immune signaling. We find that mutation or tissue-specific depletion of SMN induces hyperactivation of the immune deficiency (IMD) and Toll pathways, leading to overexpression of antimicrobial peptides (AMPs) and ectopic formation of melanotic masses in the absence of an external challenge. Furthermore, the knockdown of downstream targets of these signaling pathways reduced melanotic mass formation caused by SMN loss. Importantly, we identify SMN as a negative regulator of a ubiquitylation complex that includes Traf6, Bendless, and Diap2 and plays a pivotal role in several signaling networks. CONCLUSIONS: In alignment with recent research on other neurodegenerative diseases, these findings suggest that hyperactivation of innate immunity contributes to SMA pathology. This work not only provides compelling evidence that hyperactive innate immune signaling is a primary effect of SMN depletion, but it also suggests that the SMN complex plays a regulatory role in this process in vivo. In summary, immune dysfunction in SMA is a consequence of reduced SMN levels and is driven by cellular and molecular mechanisms that are conserved between insects and mammals.
Subject(s)
Disease Models, Animal , Immunity, Innate , Muscular Atrophy, Spinal , Signal Transduction , Animals , Muscular Atrophy, Spinal/genetics , Muscular Atrophy, Spinal/immunology , Drosophila melanogaster/immunology , Drosophila Proteins/genetics , Drosophila Proteins/metabolismABSTRACT
We identified and validated a collection of circular RNAs (circRNAs) in Drosophila melanogaster. We show that depletion of the pro-viral circRNA circATP8B(2), but not its linear siblings, compromises viral infection both in cultured Drosophila cells and in vivo. In addition, circATP8B(2) is enriched in the fly gut, and gut-specific depletion of circATP8B(2) attenuates viral replication in an oral infection model. Furthermore, circATP8B(2) depletion results in increased levels of reactive oxygen species (ROS) and enhanced expression of dual oxidase (Duox), which produces ROS. Genetic and pharmacological manipulations of circATP8B(2)-depleted flies that reduce ROS levels rescue the viral replication defects elicited by circATP8B(2) depletion. Mechanistically, circATP8B(2) associates with Duox, and circATP8B(2)-Duox interaction is crucial for circATP8B(2)-mediated modulation of Duox activity. In addition, Gαq, a G protein subunit required for optimal Duox activity, acts downstream of circATP8B(2). We conclude that circATP8B(2) regulates antiviral defense by modulating Duox expression and Duox-dependent ROS production.
Subject(s)
Drosophila Proteins , Drosophila melanogaster , RNA, Circular , Reactive Oxygen Species , Animals , Reactive Oxygen Species/metabolism , RNA, Circular/genetics , RNA, Circular/metabolism , Drosophila melanogaster/immunology , Drosophila melanogaster/genetics , Drosophila melanogaster/metabolism , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , Virus Replication , RNA/metabolism , RNA/genetics , NADPH Oxidases/metabolism , NADPH Oxidases/genetics , Dual Oxidases/metabolism , Dual Oxidases/geneticsABSTRACT
The proteins that coordinate the complex transcriptional networks of aging have not been completely documented. Protein 14-3-3zeta is an adaptor protein that coordinates signaling and transcription factor networks, but its function in aging is not fully understood. Here, we showed that the protein expression of 14-3-3zeta gradually increased during aging. High levels of 14-3-3zeta led to shortened lifespan and imbalance of intestinal immune homeostasis in Drosophila, but the decrease in 14-3-3zeta protein levels by RNAi was able to significantly promote the longevity and intestinal immune homeostasis of fruit flies. Importantly, we demonstrate that adult-onset administration of TIC10, a compound that reduces the aging-related AKT and extracellular signal-regulated kinase (ERK) signaling pathways, rescues the shortened lifespan of 14-3-3zeta-overexpressing flies. This finding suggests that 14-3-3zeta plays a critical role in regulating the aging process. Our study elucidates the role of 14-3-3zeta in natural aging and provides the rationale for subsequent 14-3-3zeta-based antiaging research.
Subject(s)
14-3-3 Proteins , Aging , Drosophila Proteins , Drosophila melanogaster , Intestines , Animals , 14-3-3 Proteins/genetics , 14-3-3 Proteins/metabolism , Aging/genetics , Drosophila melanogaster/growth & development , Drosophila melanogaster/immunology , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Longevity , Signal Transduction , Intestines/immunologyABSTRACT
IMPORTANCE: Arboviruses, particularly those transmitted by mosquitoes, pose a significant threat to humans and are an increasing concern because of climate change, human activity, and expanding vector-competent populations. West Nile virus is of significant concern as the most frequent mosquito-borne disease transmitted annually within the continental United States. Here, we identify a previously uncharacterized signaling pathway that impacts West Nile virus infection, namely endothelin signaling. Additionally, we demonstrate that we can successfully translate results obtained from D. melanogaster into the more relevant human system. Our results add to the growing field of insulin-mediated antiviral immunity and identify potential biomarkers or intervention targets to better address West Nile virus infection and severe disease.
Subject(s)
Endothelins , Insulin , West Nile Fever , Animals , Humans , Drosophila melanogaster/immunology , Drosophila melanogaster/metabolism , Drosophila melanogaster/virology , Insulin/metabolism , Signal Transduction , West Nile Fever/immunology , West Nile Fever/metabolism , West Nile Fever/virology , West Nile virus/immunology , West Nile virus/physiology , Endothelins/immunology , Endothelins/metabolismABSTRACT
Antimicrobial peptides are host-encoded immune effectors that combat pathogens and shape the microbiome in plants and animals. However, little is known about how the host antimicrobial peptide repertoire is adapted to its microbiome. Here, we characterized the function and evolution of the Diptericin antimicrobial peptide family of Diptera. Using mutations affecting the two Diptericins (Dpt) of Drosophila melanogaster, we reveal the specific role of DptA for the pathogen Providencia rettgeri and DptB for the gut mutualist Acetobacter. The presence of DptA- or DptB-like genes across Diptera correlates with the presence of Providencia and Acetobacter in their environment. Moreover, DptA- and DptB-like sequences predict host resistance against infection by these bacteria across the genus Drosophila. Our study explains the evolutionary logic behind the bursts of rapid evolution of an antimicrobial peptide family and reveals how the host immune repertoire adapts to changing microbial environments.