LPS stimulates bactericidal activity in the social amoeba Dictyostelium discoideum (37.47)

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Abstract Innate immune cells use evolutionarily-conserved pattern-recognition machinery to detect pathogen-associated molecular patterns (PAMPs). The conservation of pattern-recognition machinery allows for its characterization in various model organisms. The social amoeba Dictyostelium discoideum is a unique model system that can exist as single-celled amoebae that phagocytize bacteria for nutritional uptake. Although D. discoideum has been used to study bacterial phagocytosis, it has not been determined whether D. discoideum uses pattern-recognition machinery to detect bacterial PAMPs. Here we show that D. discoideum mounts responses against the bacterial cell wall PAMP, lipopolysaccharide (LPS). LPS treatment of D. discoideum results in more efficient uptake of bacteria and more efficient clearance of phagocytized bacteria. In addition, as shown by qRT-PCR, D. discoideum treated with LPS upregulate expression of putative pattern-recognition and phago-lysosomal genes. Both LPS-enhanced bactericidal activity and gene expression are dependent on MAPK signaling. We currently are determining the mechanisms by which LPS stimulates D. discoideum by studying intracellular trafficking of phagocytized bacteria and by creating D. discoideum cells that overexpress or are deficient for pattern-recognition and phago-lysosomal genes. The characterization of pattern recognition in D. discoideum should provide insight into conserved molecular mechanisms underlying microbial detection.