The innate immune response requires continuous surveillance of the environment, and the ability to detect and react to pathogens and danger signals. Phagocytosis –the ingestion of particulate matter ≥0.5 µm in diameter– and macropinocytosis –the gulping of large volumes of extracellular fluid– are key components of innate immunity. Both processes are complex and elegant, involving receptors and signal transduction, as well as cytoskeletal and membrane remodeling; a compendium of cell biology! These processes are often subverted by viruses, bacteria and fungi that take advantage of the host cells to establish a niche that favors their growth, replication and dissemination. My presentation will consist of a review of basic aspects of phagocytosis and macropinocytosis, followed by two sections describing recent advances in the field that have revealed the involvement of unique cytoskeletal structures (in the case of phagocytosis) and of ion channels (in macropinocytosis).
1. Understand the stages and functional roles of macropinocytosis and phagocytosis.
2. Appreciate the key role of phosphoinositides and inorganic ions in signaling and driving the formation and maturation of phagosomes and macropinosomes.