Role of Rab5 early endosomes in regulating Drosophila gut antibacterial response

Interactions between prokaryotes and eukaryotes require a dialogue between MAMPs and PRRs. In Drosophila, bacterial peptidoglycan is detected by PGRP receptors. While the components of the signaling cascades activated upon PGN/ PGRP interactions are well characterized, little is known about the subcellular events that translate these early signaling steps into target gene transcription. Using a Drosophila enteric infection model, we show that gut-associated bacteria can induce the formation of intracellular PGRP-LE aggregates which colocalized with the early endosome marker Rab5. Combining microscopic and RNA-seq analysis, we demonstrate that RNAi inactivation of the endocytosis pathway in the Drosophila gut affects the expression of essential regulators of the NF-kB response leading not only to a disruption of the immune response locally in the gut but also at the systemic level. This work sheds new light on the involvement of the endocytosis pathway in the control of the gut response to intestinal bacterial infection

Oligopeptide Transporters of the SLC15 Family Are Dispensable for Peptidoglycan Sensing and Transport in <b><i>Drosophila</i></b>

International audiencePeptidoglycan (PGN) detection by PGN recognition proteins (PGRP) is the main trigger of the antibacterial immune response in Drosophila. Depending on the type of immune cell, PGN can be sensed either at the cell membrane by PGRP-LC or inside the cell by PGRP-LE, which plays a role similar to that of Nod2 in mammals. Previous work, mainly in cell cultures, has shown that oligopeptide transporters of the SLC15 family are essential for the delivery of PGN for Nod2 detection inside of the cells, and that this function might be conserved in flies. By generating and analyzing the immune phenotypes of loss-of-function mutations in 3 SLC15 Drosophila family members, we tested their role in mediating PGRP-LE-dependent PGN activation. Our results show that Yin, CG2930, and CG9444 are required neither for PGRP-LE activation by PGN nor for PGN transport from the gut lumen to the insect blood. These data show that, while intracellular PGN detection is an essential step of the antibacterial response in both insects and mammals, the types of PGN transporters and sensors are different in these animals

Peptidoglycan-dependent NF-κB activation in a small subset of brain octopaminergic neurons controls female oviposition

When facing microbes, animals engage in behaviors that lower the impact of the infection. We previously demonstrated that internal sensing of bacterial peptidoglycan reduces Drosophila female oviposition via NF-kappaB pathway activation in some neurons (Kurz et al., 2017). Although we showed that the neuromodulator octopamine is implicated, the identity of the involved neurons, as well as the physiological mechanism blocking egg-laying, remained unknown. In this study, we identified few ventral nerve cord and brain octopaminergic neurons expressing an NF-kappaB pathway component. We functionally demonstrated that NF-kappaB pathway activation in the brain, but not in the ventral nerve cord octopaminergic neurons, triggers an egg-laying drop in response to infection. Furthermore, we demonstrated via calcium imaging that the activity of these neurons can be directly modulated by peptidoglycan and that these cells do not control other octopamine-dependent behaviors such as female receptivity. This study shows that by sensing peptidoglycan and hence activating NF-kappaB cascade, a couple of brain neurons modulate a specific octopamine-dependent behavior to adapt female physiology status to their infectious state

Cytosolic and Secreted Peptidoglycan-Degrading Enzymes in Drosophila Respectively Control Local and Systemic Immune Responses to Microbiota

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Peptidoglycan-dependent NF-κB activation in a small subset of brain octopaminergic neurons controls female oviposition

Indexation en cours. PMCID: PMC6819134International audienceWhen facing microbes, animals engage in behaviors that lower the impact of the infection. We previously demonstrated that internal sensing of bacterial peptidoglycan reduces Drosophila female oviposition via NF-kB pathway activation in some neurons (Kurz et al., 2017). Although we showed that the neuromodulator octopamine is implicated, the identity of the involved neurons, as well as the physiological mechanism blocking egg-laying, remained unknown. In this study, we identified few ventral nerve cord and brain octopaminergic neurons expressing an NF-kB pathway component. We functionally demonstrated that NF-kB pathway activation in the brain, but not in the ventral nerve cord octopaminergic neurons, triggers an egg-laying drop in response to infection. Furthermore, we demonstrated via calcium imaging that the activity of these neurons can be directly modulated by peptidoglycan and that these cells do not control other octopamine-dependent behaviors such as female receptivity. This study shows that by sensing peptidoglycan and hence activating NF-kB cascade, a couple of brain neurons modulate a specific octopamine-dependent behavior to adapt female physiology status to their infectious state

Activation of 5-HT 2A receptors restores KCC2 function and reduces neuropathic pain after spinal cord injury

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Comment le dialogue moléculaire entre bactéries et neurones change le comportement de l’hôte infecté

National audienceLes eucaryotes vivent dans un environnement contaminé par des microorganismes. Il n'est donc pas surprenant qu'ils aient forgé, au fil du temps, des relations extrêmement complexes et intimes entre eux. Les eucaryotes sont capables de percevoir la présence de bactéries et d’adapter leur réponse immunitaire, leur état physiologique ou même leur comportement en conséquence. Nombreuses sont les études qui ont démontré que les bactéries peuvent interagir avec le système nerveux eucaryote, soit au bénéfice du microbe qui modifie le comportement de l'hôte, soit au bénéfice de l'hôte qui adapte son comportement à l'infection. Dans la plupart des cas, cependant, les molécules et les mécanismes qui sous- tendent le dialogue entre les bactéries et leur système nerveux hôte n'ont pas été identifiés et leur mode d'action mal compris. Je présenterai les données obtenues avec le modèle Drosophile, sur la dissection des mécanismes cellulaires et moléculaires par lesquels un seul composé dérivé de microbiote, appelé peptidoglycane, influence le comportement des hôtes infectés en agissant directement sur certains neurones du cerveau

Cleavage of Na+ channels by calpain increases persistent Na+ current and promotes spasticity after spinal cord injury

International audienceUpregulation of the persistent sodium current (INaP) in motoneurons contributes to spasticity following spinal cord injury (SCI). We investigated the mechanisms that regulate INaP and observed elevated expression of Nav1.6 channels in spinal lumbar motoneurons of adult rats with SCI. Furthermore, immunoblot revealed a proteolysis of Nav channels and biochemical assays identified calpain as the main proteolytic factor. Calpain-dependent cleavage of Nav channels following neonatal SCI was associated with an upregulation of INaP in motoneurons. Likewise, calpain-dependent cleavage of Nav1.6 channels expressed in HEK-293 cells caused elevation of INaP. Pharmacological inhibition of calpain by MDL28170 reduced the cleavage of Nav channels, INaP in motoneurons and spasticity in rats with SCI. Similarly, blockade of INaP by riluzole alleviated spasticity. This study demonstrates that Nav channel expression in lumbar motoneurons is altered after SCI and shows a tight relationship between the calpain-dependent proteolysis of Nav1.6 channels, the upregulation of INaP and spasticity