Sterol scarcity primes p38 immune defenses through a TIR-1/SARM1 phase transition
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ABSTRACT:
PROVIDER: PRJNA739671 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR14871049.fastq.gz | Fastqsanger.gz | |||
| SRR14871050.fastq.gz | Fastqsanger.gz | |||
| SRR14871051.fastq.gz | Fastqsanger.gz | |||
| SRR14871052.fastq.gz | Fastqsanger.gz | |||
| SRR14871053.fastq.gz | Fastqsanger.gz |
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Project description:Intracellular signaling regulators are concentrated into membrane-free, higher-ordered protein assemblies to initiate protective responses during stress — a process known as phase transition. Here, we show that a phase transition of the C. elegans Toll/interleukin-1 receptor domain protein (TIR-1), a homolog of the mammalian sterile alpha and TIR motif-containing 1 (SARM1), primes host immune defenses when dietary sterols are limited to handle subsequent bacterial infection. TIR-1/SARM1 is an upstream component of the p38 PMK-1 pathway in intestinal cells, an innate immune defense and stress response pathway in metazoans. Under conditions of low cholesterol availability, multimerization and precipitation of TIR-1/SARM1 potentiates the intrinsic NAD+ glycohydrolase activity of this protein complex, increases p38 PMK-1 phosphorylation, and promotes pathogen clearance from the intestine. Dietary cholesterol is required for C. elegans to survive infection with pathogenic bacteria and to support development, fecundity, and lifespan. Thus, activation of the p38 PMK-1 pathway in sterol-deficient animals is an adaptive response that allows a metazoan host to anticipate environmental threats under conditions of essential metabolite scarcity.
2022-03-18 | GSE178572 | GEO
Project description:Innate immunity in bacteria, plants and animals requires the specialized subset of TIR-domain proteins that are NAD+ hydrolases. Aggregation of these TIR proteins engages their enzymatic activity, but it is not known how this protein multimerization is regulated. Here, we discovered that TIR oligomerization is exquisitely controlled to prevent immune toxicity. We found that p38 propagates its own activation by promoting the feedforward expression and aggregation of the lone enzymatic TIR protein in the nematode C. elegans, TIR-1/SARM1. We performed a forward genetic screen to determine how the p38 positive feedforward loop is regulated. We discovered that the integrity of the specific lysosomal sub-compartment that expresses TIR-1/SARM1 is actively maintained to limit inappropriate aggregation of this protein and restrain toxic p38 immune activation. Thus, innate immune defenses in intestinal epithelial cells are regulated by specific control of TIR-1/SARM1 multimerization.
2024-09-18 | GSE256356 | GEO
Project description:Intracellular signaling regulators can be concentrated into membrane-free, higher-ordered protein assemblies to initiate protective responses during stress — a process known as phase transition. Here, we show that a phase transition of the Caenorhabditis elegans Toll/interleukin-1 receptor domain protein (TIR-1), an NAD+ glycohydrolase homologous to mammalian sterile alpha and TIR motif-containing 1 (SARM1), underlies p38 PMK-1 immune pathway activation in C. elegans intestinal epithelial cells. Through visualization of fluorescently labeled TIR-1/SARM1 protein, we demonstrate for the first time that physiologic stresses, both pathogen and non-pathogen, induce multimerization of TIR-1/SARM1 into visible puncta within intestinal epithelial cells. In vitro enzyme kinetic analyses revealed that, like mammalian SARM1, the NAD+ glycohydrolase activity of C. elegans TIR-1 is dramatically potentiated by protein oligomerization and a phase transition. Accordingly, C. elegans with genetic mutations that specifically block either multimerization or the NAD+ glycohydrolase activity of TIR-1/SARM1 fail to induce p38 PMK phosphorylation, are unable to increase immune effector expression, and are dramatically susceptible to bacterial infection. Finally, we demonstrate that low cholesterol stress causes TIR-1/SARM1 to oligomerize into puncta in intestinal epithelial cells and engages its NAD+ glycohydrolase activity, which increases p38 PMK-1 phosphorylation, and primes immune effector induction in a manner that leads to reduced pathogen accumulation in the intestine during a subsequent infection. These data reveal a new adaptive response that allows a metazoan host to anticipate pathogen threats during micronutrient deprivation, a time of relative susceptibility to infection. Thus, a phase transition of TIR-1/SARM1 as a prerequisite for its NAD+ glycohydrolase activity is strongly conserved across millions of years of evolution and is essential for diverse physiological processes in multiple cell types.
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Project description:Lysosomal integrity suppresses TIR-1/SARM1 aggregation to restrain toxic propagation of p38 innate immunity
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Project description:Upon axonal injury, Sterile alpha (SAM) and Toll/interleukin-1 receptor (TIR) motif containing 1 (SARM1) is activated by nicotinamide mononucleotide (NMN) to deplete NAD and consequently promote the process of axon degeneration (AxD). Currently, only the inactive form of SARM1 in its auto-inhibitory conformation has been resolved. The flexibility of the enzymatically active form of SARM1 has so far precluded its structural determination. To solve the problem, we generated a stabilizing nanobody, Nb-C6, that specifically recognized 30 only the NMN-activated form of SARM1. The conformation specificity was verified by immunoprecipitation and surface plasmon resonance. Fluorescently labeled Nb-C6 could immunostain only the activated SARM1 in cells stimulated with CZ-48, a permeant mimetic of NMN. Expression of Nb-C6 in live cells resulted in stabilization of the active form of the endogenous and exogenous SARM1, producing and elevating cellular levels of cyclic ADP-ribose, a calcium messenger. Cryo-EM of the NMN-activated SARM1 complexed by Nb-C6 showed an octameric structure resembling a “blooming lotus” with the ARM domains bending significantly inward and swinging out together with the TIR domains to form the “petals of the lotus”. Nb-C6 bound to the SAM domain of the activated SARM1 and stabilized its Armadillo repeat motif domain. Analyses using hydrogen-deuterium exchange mass spectrometry (HDX-MS), and cross-linking MS (XL-MS) indicate that the activated SARM1 is highly dynamic and flexible and the neighboring TIRs form dimers via the surface close to one BB loop. The Nanobody is thus a valuable tool for delineating the mechanism of activation of SARM1 in AxD and other cellular processes.
2022-11-29 | PXD033528 | Pride
Project description:Diabetic patients have a high risk of developing skeletal diseases accompanied by diabetic peripheral neuropathy (DPN). In this study, we isolated the role of DPN in skeletal disease with global and conditional knockout models of sterile-α and TIR-motif-containing protein-1 (Sarm1). SARM1, an NADase highly expressed in the nervous system, regulates axon degeneration upon a range of insults, including DPN. Global knockout of Sarm1 prevented DPN, but not skeletal disease, in male mice with type 1 diabetes (T1D). Female wild type mice also developed diabetic bone disease, but without DPN. Unexpectedly, global Sarm1 knockout completely protected female mice from T1D-associated bone suppression and skeletal fragility despite comparable muscle atrophy and hyperglycemia. Global Sarm1 knockout rescued bone health through sustained osteoblast function with abrogation of local oxidative stress responses. This was independent of the neural actions of SARM1, as beneficial effects on bone were lost with neural conditional Sarm1 knockout. This study demonstrates that the onset of skeletal disease occurs rapidly in both male and female mice with T1D completely independent of DPN. In addition, this reveals that clinical SARM1 inhibitors, currently being developed for treatment of neuropathy, may also have benefits for diabetic bone through actions outside of the nervous system.
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Project description:Pathogen infection and cholesterol deficiency activate the C. elegans p38 immune pathway through a TIR-1/SARM1 phase transition
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Project description:Programmed cell suicide of infected bacteria, known as abortive infection (Abi), serves as a central immune defense strategy to prevent the spread of bacteriophage viruses and other invasive genetic elements across a population. Many Abi systems utilize bespoke cyclic nucleotide immune messengers generated upon infection to rapidly mobilize cognate death effectors. Here, we identify a large family of bacteriophage nucleotidyltransferases (NTases) which synthesize competitor cyclic dinucleotide (CDN) ligands and inhibit NAD-depleting TIR effectors activated through a linked STING CDN sensor domain (TIR-STING). Through a functional screen of NTase-adjacent phage genes, we uncover candidate inhibitors of host TIR-STING suicide signaling. Among these, we demonstrate that a virus MazG-like nucleotide pyrophosphatase, Atd1, depletes the starvation alarmone (p)ppGpp, revealing a role for the alarmone-activated host toxin MazF as a key executioner of TIR-driven abortive infection. Phage NTases and counter-defenses like Atd1 preserve host viability to ensure virus propagation, and may be exploited as tools to modulate TIR and STING immune responses.
2023-03-27 | GSE222071 | GEO
Project description:Axon loss contributes to many common neurodegenerative disorders. In healthy axons, the axon survival factor NMNAT2 inhibits SARM1, the central executioner of programmed axon degeneration. We identified two rare NMNAT2 missense variants in two brothers afflicted with a progressive neuropathy syndrome. The polymorphisms result in amino acid substitutions, V98M and R232Q, which reduce NMNAT2 NAD+-synthetase activity. We generated a mouse model of the human syndrome and found that Nmnat2V98M/Nmnat2R232Q compound-heterozygous CRISPR mice survive to adulthood but develop progressive motor dysfunction, peripheral axon loss, and macrophage infiltration. These disease phenotypes are all SARM1-dependent. Remarkably, macrophage depletion therapy blocks and reverses neuropathic phenotypes in Nmnat2V98M/R232Q mice, identifying a SARM1-dependent neuroimmune mechanism as a key driver of disease pathogenesis. These findings demonstrate that SARM1 induces an inflammatory neuropathy and highlight the potential of immune therapy to treat this rare syndrome and other neurodegenerative conditions associated with NMNAT2 loss and SARM1 activation.
2022-10-25 | GSE210403 | GEO
Project description:To study the effect of SARM1 deficiency on brain transcriptome, we performed RNAsequencing of the brain of SARM1-/- mice and their wild type (C57BL/6J) littermates with or without prion infection. We analyzed differential gene expression.
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