bims-nocaut 2023-07-09 papers

Issue of 2023–07–09
three papers selected by
Quentin Frenger, University of Strasbourg

Nat Commun. 2023 07 04. 14(1): 3945

Macrophage lineage cells-derived migrasomes activate complement-dependent blood-brain barrier damage in cerebral amyloid angiopathy mouse model.

Accumulation of amyloid beta protein (Aβ) in brain vessels damages blood brain barrier (BBB) integrity in cerebral amyloid angiopathy (CAA). Macrophage lineage cells scavenge Aβ and produce disease-modifying mediators. Herein, we report that Aβ40-induced macrophage-derived migrasomes are sticky to blood vessels in skin biopsy samples from CAA patients and brain tissue from CAA mouse models (Tg-SwDI/B and 5xFAD mice). We show that CD5L is packed in migrasomes and docked to blood vessels, and that enrichment of CD5L impairs the resistance to complement activation. Increased migrasome-producing capacity of macrophages and membrane attack complex (MAC) in blood are associated with disease severity in both patients and Tg-SwDI/B mice. Of note, complement inhibitory treatment protects against migrasomes-mediated blood-brain barrier injury in Tg-SwDI/B mice. We thus propose that macrophage-derived migrasomes and the consequent complement activation are potential biomarkers and therapeutic targets in CAA.

DOI: https://doi.org/10.1038/s41467-023-39693-x

EMBO J. 2023 Jul 06. e113012

TECPR1 conjugates LC3 to damaged endomembranes upon detection of sphingomyelin exposure.

Keith B Boyle, Cara J Ellison, Paul R Elliott, Martina Schuschnig, Krista Grimes, Marc S Dionne, Chihiro Sasakawa, Sean Munro, Sascha Martens, Felix Randow.

Invasive bacteria enter the cytosol of host cells through initial uptake into bacteria-containing vacuoles (BCVs) and subsequent rupture of the BCV membrane, thereby exposing to the cytosol intraluminal, otherwise shielded danger signals such as glycans and sphingomyelin. The detection of glycans by galectin-8 triggers anti-bacterial autophagy, but how cells sense and respond to cytosolically exposed sphingomyelin remains unknown. Here, we identify TECPR1 (tectonin beta-propeller repeat containing 1) as a receptor for cytosolically exposed sphingomyelin, which recruits ATG5 into an E3 ligase complex that mediates lipid conjugation of LC3 independently of ATG16L1. TECPR1 binds sphingomyelin through its N-terminal DysF domain (N'DysF), a feature not shared by other mammalian DysF domains. Solving the crystal structure of N'DysF, we identified key residues required for the interaction, including a solvent-exposed tryptophan (W154) essential for binding to sphingomyelin-positive membranes and the conjugation of LC3 to lipids. Specificity of the ATG5/ATG12-E3 ligase responsible for the conjugation of LC3 is therefore conferred by interchangeable receptor subunits, that is, the canonical ATG16L1 and the sphingomyelin-specific TECPR1, in an arrangement reminiscent of certain multi-subunit ubiquitin E3 ligases.

Keywords: ATG5-ATG12 E3 ligase; DysF; autophagy; membrane damage; sphingomyelin

DOI: https://doi.org/10.15252/embj.2022113012

EMBO J. 2023 Jul 06. e113105

TECPR1 is activated by damage-induced sphingomyelin exposure to mediate noncanonical autophagy.

Namrita Kaur, Laura Rodriguez de la Ballina, Håvard Styrkestad Haukaas, Maria Lyngaas Torgersen, Maja Radulovic, Michael J Munson, Alan Sabirsh, Harald Stenmark, Anne Simonsen, Sven R Carlsson, Alf Håkon Lystad.

Cells use noncanonical autophagy, also called conjugation of ATG8 to single membranes (CASM), to label damaged intracellular compartments with ubiquitin-like ATG8 family proteins in order to signal danger caused by pathogens or toxic compounds. CASM relies on E3 complexes to sense membrane damage, but so far, only the mechanism to activate ATG16L1-containing E3 complexes, associated with proton gradient loss, has been described. Here, we show that TECPR1-containing E3 complexes are key mediators of CASM in cells treated with a variety of pharmacological drugs, including clinically relevant nanoparticles, transfection reagents, antihistamines, lysosomotropic compounds, and detergents. Interestingly, TECPR1 retains E3 activity when ATG16L1 CASM activity is obstructed by the Salmonella Typhimurium pathogenicity factor SopF. Mechanistically, TECPR1 is recruited by damage-induced sphingomyelin (SM) exposure using two DysF domains, resulting in its activation and ATG8 lipidation. In vitro assays using purified human TECPR1-ATG5-ATG12 complex show direct activation of its E3 activity by SM, whereas SM has no effect on ATG16L1-ATG5-ATG12. We conclude that TECPR1 is a key activator of CASM downstream of SM exposure.

Keywords: CASM; DysF; membrane damage; noncanonical autophagy; sphingomyelin

DOI: https://doi.org/10.15252/embj.2022113105