Role of lipid-mediated signal transduction in bacterial internalization

Abstract
Receptor‐mediated phagocytosis normally represents an important first line of immune defence. Invading microbes are internalized into phagosomes and are typically killed by exposure to a battery of microbicidal agents. To some intracellular pathogens, however, receptor‐mediated phagocytosis represents an opportunity to access a protected niche within the host cell. Another type of intracellular pathogen, including Salmonella enterica serovar Typhimurium and Shigella flexneri, invade host cells in a more direct manner. These pathogens deliver effectors into the host cell via a type III secretion apparatus, initiating a ruffling response that leads to their uptake into intracellular vacuoles. Recent studies have demonstrated the importance of lipid signal transduction events in the uptake of pathogenic bacteria by both receptor‐mediated phagocytosis and type III secretion‐mediated invasion. In this review we highlight some of these discoveries, with a focus on phospholipid‐dependent signalling events.