Differential regulation of phagosome maturation in macrophages and dendritic cells mediated by Rho GTPases and ezrin-radixin-moesin (ERM) proteins

Deletion of apoptotic cells from tissues involves their phagocytosis by macrophages, dendritic cells, and tissue cells. Although much attention has been focused on the participating ligands, receptors, and mechanisms of uptake, little is known of the disposition of the ingested cell within the phagosome. Here we show that uptake of apoptotic cells by macrophages or fibroblasts results in rapid phagosome maturation, whereas macrophage phagosomes containing 1g-opsonized target cells mature at a slower rate. The early maturation was shown to depend on activation of Rho acting through Rho kinase on ezrin-radixin-moesin proteins. Blockade of Rho signaling or inhibition of moesin both delayed maturation rates to those seen with opsonized targets. By contrast, phagosome maturation in dendritic cells was slower, similar between apoptotic and opsonized target cells, and unaffected by Rho inhibition. These observations have direct implications for the clearance of dying cells and the roles played by different phagocytes in antigen digestion and presentation.