Septins and K63 ubiquitin chains are present in separate bacterial microdomains during autophagy of entrapped Shigella.
Lobato-Márquez, Damián;
Conesa, José Javier;
López-Jiménez, Ana Teresa;
Divine, Michael E;
Pruneda, Jonathan N;
Mostowy, Serge;
(2023)
Septins and K63 ubiquitin chains are present in separate bacterial microdomains during autophagy of entrapped Shigella.
Journal of cell science, 136 (7).
jcs261139-.
ISSN 0021-9533
DOI: https://doi.org/10.1242/jcs.261139
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During host cell invasion, Shigella escapes to the cytosol and polymerizes actin for cell-to-cell spread. To restrict cell-to-cell spread, host cells employ cell-autonomous immune responses including antibacterial autophagy and septin cage entrapment. How septins interact with the autophagy process to target Shigella for destruction is poorly understood. Here, we employed a correlative light and cryo-soft X-ray tomography (cryo-SXT) pipeline to study Shigella septin cage entrapment in its near-native state. Quantitative cryo-SXT showed that Shigella fragments mitochondria and enabled visualization of X-ray-dense structures (∼30 nm resolution) surrounding Shigella entrapped in septin cages. Using Airyscan confocal microscopy, we observed lysine 63 (K63)-linked ubiquitin chains decorating septin-cage-entrapped Shigella. Remarkably, septins and K63 chains are present in separate bacterial microdomains, indicating they are recruited separately during antibacterial autophagy. Cryo-SXT and live-cell imaging revealed an interaction between septins and LC3B-positive membranes during autophagy of Shigella. Together, these findings demonstrate how septin-caged Shigella are targeted for autophagy and provide fundamental insights into autophagy-cytoskeleton interactions.