The pathogen Legionella pneumophila invades macrophages and replicates intracellularly within specialized phagosomes: membrane-enclosed vacuoles. Usually, an entering phagosome would be directed to fuse with lysosomes, and its contents would be degraded by lysosomal digestive enzymes. How does internalized Legionella avoid this fate?
Kagan and Roy examined membrane trafficking after internalization of L. pneumophila and found that, soon after their formation, the phagosomes intercept and fuse with early secretory vesicles and recruit proteins that were originally destined for the endoplasmic reticulum (ER). This sets up a privileged membrane compartment resistant to fusion with lysosomes and permits the development of an organelle for bacterial multiplication. -- SMH
Nature Cell Biol. 4, 945 (2002).