Septin barriers protect mammalian host cells against Pseudomonas aeruginosa invasion

Septin GTPases polymerize into higher-ordered structures as a part of the cytoskeleton and are involved in interactions of the host with a wide spectrum of pathogens. Many pathogens foster an ambiguous relation-ship with septins. They exploit septins for uptake, but septins also prevent their intracellular replication and target them for autophagy. We demonstrate that septins are involved in a defense mechanism against the pathogen Pseudomonas aeruginosa, which enters cells via a lipid zippering mechanism relying on interaction of the lectin LecA with the glycosphingolipid Gb3 on the host membrane. LecA-dependent invagination of the plasma membrane triggers septin recruitment to the site of bacterial attachment. We also find a septin-dependent reinforcement of cortical actin at attachment sites. Atomic force microscopy reveals formation of a septin-dependent rigid barrier below the membrane, preventing bacterial penetration. Our data suggest that septin barriers represent a cellular defense against bacteria inducing membrane curvature for invasion.

Automated summary

Septin GTPases are involved in host-pathogen interactions and can prevent the invasion of bacteria by forming a rigid barrier.