Phagocytosis: A (Sphingo)Lipid Story

Phagocytosis is an evolutionary conserved innate immunological response, critical for fighting off pathogens and/or infections in higher organisms, including humans. During this process, any detrimental foreign particles (e.g. bacteria, virus, dead cells) are engulfed by immune cells called phagocytes (e.g. macrophages, monocytes), and packaged in an intracellular entity (or organelle) called the phagosome. The phagosome then undergoes a well-choreographed sequence of changes in protein and lipid composition termed "phagosomal maturation", eventually fuses with the lysosome to form the phagolysosome, and thus marks the end of phagocytosis. While a lot is known of the proteomic changes during phagosomal maturation, in comparison, till recently, little remained known of the lipidomic changes during this process. Here, we review the current knowledge of the lipid changes on purified phagosomes, namely early and late phagosomes, during phagosomal maturation, with a special focus on sphingolipid metabolism during this important immune response.