Mechanisms of Fc receptor and dectin-1 activation for phagocytosis.

Phagocytosis is a key cellular process, both during homeostasis and upon infection or tissue damage. Receptors on the surface of professional phagocytic cells bind to target particles either directly or through opsonizing ligands, and trigger actin-mediated ingestion of the particles. The process must be carefully controlled to ensure that phagocytosis is triggered efficiently and specifically, and that the antimicrobial cytotoxic responses that often accompany it are initiated only when required. In this review, we will describe and compare the molecular mechanisms that regulate phagocytosis triggered by Fcγ receptors, which mediate the uptake of immunoglobulin G-opsonized targets, and Dectin-1, which is responsible for internalization of fungi with exposed cell wall β-glucan. We will examine how these receptors detect their ligands, how signal transduction is initiated and regulated, and how internalization is instructed to achieve rapid and yet controlled uptake of their targets.