Mechanistic insight into bacterial entrapment by septin cage reconstitution

Nat Commun. 2021 Jul 23;12(1):4511. doi: 10.1038/s41467-021-24721-5.


Septins are cytoskeletal proteins that assemble into hetero-oligomeric complexes and sense micron-scale membrane curvature. During infection with Shigella flexneri, an invasive enteropathogen, septins restrict actin tail formation by entrapping bacteria in cage-like structures. Here, we reconstitute septin cages in vitro using purified recombinant septin complexes (SEPT2-SEPT6-SEPT7), and study how these recognize bacterial cells and assemble on their surface. We show that septin complexes recognize the pole of growing Shigella cells. An amphipathic helix domain in human SEPT6 enables septins to sense positively curved membranes and entrap bacterial cells. Shigella strains lacking lipopolysaccharide components are more efficiently entrapped in septin cages. Finally, cryo-electron tomography of in vitro cages reveals how septins assemble as filaments on the bacterial cell surface.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cell Membrane / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Dysentery, Bacillary / metabolism*
  • Dysentery, Bacillary / microbiology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Lipopolysaccharides / metabolism
  • Microscopy, Fluorescence
  • Mutation
  • Protein Binding
  • Recombinant Proteins / metabolism*
  • Septins / genetics
  • Septins / metabolism*
  • Shigella flexneri / genetics
  • Shigella flexneri / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism


  • Actins
  • Bacterial Proteins
  • DNA-Binding Proteins
  • Lipopolysaccharides
  • Recombinant Proteins
  • Transcription Factors
  • virG protein, Shigella flexneri
  • Green Fluorescent Proteins
  • SEPTIN6 protein, human
  • Septins