Social amoebae trap and kill bacteria by casting DNA nets.

Nature communications (2016-03-02)
Xuezhi Zhang, Olga Zhuchenko, Adam Kuspa, Thierry Soldati
ABSTRACT

Extracellular traps (ETs) from neutrophils are reticulated nets of DNA decorated with anti-microbial granules, and are capable of trapping and killing extracellular pathogens. Various phagocytes of mammals and invertebrates produce ETs, however, the evolutionary history of this DNA-based host defence strategy is unclear. Here we report that Sentinel (S) cells of the multicellular slug stage of the social amoeba Dictyostelium discoideum produce ETs upon stimulation with bacteria or lipopolysaccharide in a reactive oxygen species-dependent manner. The production of ETs by S cells requires a Toll/Interleukin-1 receptor domain-containing protein TirA and reactive oxygen species-generating NADPH oxidases. Disruption of these genes results in decreased clearance of bacterial infections. Our results demonstrate that D. discoideum is a powerful model organism to study the evolution and conservation of mechanisms of cell-intrinsic immunity, and suggest that the origin of DNA-based ETs as an innate immune defence predates the emergence of metazoans.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Lucifer Yellow CH dilithium salt, fluorescent stain
Sigma-Aldrich
Lipopolysaccharides from Pseudomonas aeruginosa 10, purified by phenol extraction
Sigma-Aldrich
Dihydroethidium, BioReagent, suitable for fluorescence, ≥95% (HPCE)
Roche
Peroxidase (POD), grade I, from horseradish