Autophagy induction and bactericidal activity in Dictyostelium discoideum

Abstract

The innate immune system is the body's first line of defense and uses pattern recognition machinery to identify conserved pathogen-associated molecular patterns (PAMPs) to detect and neutralize pathogens. Dictyostelium discoideum is a unique model organism that phagocytizes bacteria for nutritional purposes. We have shown that D. discoideum cells will clear intracellular bacteria faster in the presence of the PAMP, lipopolysaccharide (LPS) suggesting that they may detect and respond to bacterial pathogens through pattern recognition machinery. In this study we extend these findings showing that LPS pre-treatment will stimulate autophagosomal maturation in D. discoideum cells exposed to Staphylococcus aureus. The induction of autophagy by rapamycin causes D. discoideum cells to degrade intracellular bacteria at a faster rate. Here we also show that the increased rate of LPS-stimulated bacterial degradation is dependent upon the autophagy related proteins, Atg1 and Atg9, thus linking D. discoideum pattern recognition and the induction of autophagy.