Neurotoxin-mediated potent activation of the axon degeneration regulator SARM1
- University of Cambridge, United Kingdom
- Polytechnic University of Marche, Italy
- University of Queensland, Australia
- Griffith University, Australia
- AstraZeneca, United States
- The University of Queensland, Australia
Abstract
Axon loss underlies symptom onset and progression in many neurodegenerative disorders. Axon degeneration in injury and disease is promoted by activation of the nicotinamide adenine dinucleotide (NAD)-consuming enzyme SARM1. Here, we report a novel activator of SARM1, a metabolite of the pesticide and neurotoxin vacor. Removal of SARM1 completely rescues mouse neurons from vacor-induced neuron and axon death in vitro and in vivo. We present the crystal structure the Drosophila SARM1 regulatory domain complexed with this activator, the vacor metabolite VMN, which as the most potent activator yet know is likely to support drug development for human SARM1 and NMNAT2 disorders. This study indicates the mechanism of neurotoxicity and pesticide action by vacor, raises important questions about other pyridines in wider use today, provides important new tools for drug discovery, and demonstrates that removing SARM1 can robustly block programmed axon death induced by toxicity as well as genetic mutation.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting file; Source Data files have been provided for Figures 1-7 and figure supplements. VMN-bound dSARM1ARM crystal structure has been deposited in the Protein Data Bank (PDB: 7M6K).
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VMN-bound dSARM1ARM crystal structureProtein Data Bank, 7M6K.
Article and author information
Author details
Peter Arthur-Farraj
Funding
Wellcome Trust (210904/Z/18/Z)
- Andrea Loreto
Wellcome Trust (206634)
- Peter Arthur-Farraj
Biotechnology and Biological Sciences Research Council (BB/S009582/1)
- Andrea Loreto
- Jonathan Gilley
- Michael P Coleman
UNIVPM (RSA 2016-18 and 2017-19)
- Giuseppe Orsomando
Australian National Health and Medical Research Council (NHMRC 1160570)
- Bostjan Kobe
Sight Research UK (SAC 041)
- Andrew Osborne
- Bart Nieuwenhuis
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All studies conformed to the institution's ethical requirements in accordance with the 1986 Animals (Scientific Procedures) Act under Project Licences PPL P98A03BF9 and PP1824519, and in accordance with the Association for Research in Vision and Ophthalmology's Statement for the Use of Animals in Ophthalmic and Visual Research.
Copyright
© 2021, Loreto et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Neurotoxin-mediated potent activation of the axon degeneration regulator SARM1
eLife 10:e72823.
https://doi.org/10.7554/eLife.72823
Further reading
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- Biochemistry and Chemical Biology
N 6,2’-O-dimethyladenosine (m6Am) is a modified nucleotide located at the first transcribed position in mRNA and snRNA that is essential for diverse physiological processes. m6Am mapping methods assume each gene uses a single start nucleotide. However, gene transcription usually involves multiple start sites, generating numerous 5’ isoforms. Thus, gene-level annotations cannot capture the diversity of m6Am modification in the transcriptome. Here, we describe CROWN-seq, which simultaneously identifies transcription-start nucleotides and quantifies m6Am stoichiometry for each 5’ isoform that initiates with adenosine. Using CROWN-seq, we map the m6Am landscape in nine human cell lines. Our findings reveal that m6Am is nearly always a high stoichiometry modification, with only a small subset of cellular mRNAs showing lower m6Am stoichiometry. We find that m6Am is associated with increased transcript expression and provide evidence that m6Am may be linked to transcription initiation associated with specific promoter sequences and initiation mechanisms. These data suggest a potential new function for m6Am in influencing transcription.
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- Biochemistry and Chemical Biology
- Microbiology and Infectious Disease
Glutamine synthetases (GS) are central enzymes essential for the nitrogen metabolism across all domains of life. Consequently, they have been extensively studied for more than half a century. Based on the ATP-dependent ammonium assimilation generating glutamine, GS expression and activity are strictly regulated in all organisms. In the methanogenic archaeon Methanosarcina mazei, it has been shown that the metabolite 2-oxoglutarate (2-OG) directly induces the GS activity. Besides, modulation of the activity by interaction with small proteins (GlnK1 and sP26) has been reported. Here, we show that the strong activation of M. mazei GS (GlnA1) by 2-OG is based on the 2-OG dependent dodecamer assembly of GlnA1 by using mass photometry (MP) and single particle cryo-electron microscopy (cryo-EM) analysis of purified strep-tagged GlnA1. The dodecamer assembly from dimers occurred without any detectable intermediate oligomeric state and was not affected in the presence of GlnK1. The 2.39 Å cryo-EM structure of the dodecameric complex in the presence of 12.5 mM 2-OG demonstrated that 2-OG is binding between two monomers. Thereby, 2-OG appears to induce the dodecameric assembly in a cooperative way. Furthermore, the active site is primed by an allosteric interaction cascade caused by 2-OG-binding towards an adaption of an open active state conformation. In the presence of additional glutamine, strong feedback inhibition of GS activity was observed. Since glutamine dependent disassembly of the dodecamer was excluded by MP, feedback inhibition most likely relies on the binding of glutamine to the catalytic site. Based on our findings, we propose that under nitrogen limitation the induction of M. mazei GS into a catalytically active dodecamer is not affected by GlnK1 and crucially depends on the presence of 2-OG.
