Septins and K63 ubiquitin chains are present in separate bacterial microdomains during autophagy of entrapped Shigella

J Cell Sci. 2023 Apr 1;136(7):jcs261139. doi: 10.1242/jcs.261139. Epub 2023 Apr 13.


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.

Keywords: Shigella; Autophagy; Cryo-SXT; Cytoskeleton; Septin; Ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Autophagy / physiology
  • Cytoskeleton / metabolism
  • Septins* / metabolism
  • Shigella* / metabolism
  • Ubiquitins / metabolism


  • Septins
  • Ubiquitins