Legionella pneumophila regulates host cell motility by targeting Phldb2 with a 14-3-3ζ-dependent protease effector

The cytoskeleton network of eukaryotic cells is essential for diverse cellular processes, including vesicle trafficking, cell motility and immunity, thus is a common target for bacterial virulence factors. A number of effectors from the bacterial pathogen Legionella pneumophila have been shown to modulate the function of host actin cytoskeleton to construct the Legionella-containing vacuole (LCV) permissive for its intracellular replication. In this study, we identified the Dot/Icm effector Lem8 (Lpg1290) as a protease that interferes with host motility. We show that the protease activity of Lem8 is catalyzed by a Cys-His-Asp motif known to be associated with diverse biochemical activities. Intriguingly, we found that Lem8 interacts with the host regulatory protein 14-3-3ζ, which activates its protease activity. Furthermore, Lem8 undergoes self-cleavage in a process that requires 14-3-3ζ. We identified the PH domain-containing protein Phldb2 involved in cell migration as a target of Lem8 and demonstrate that Lem8 plays a role in the inhibition of host cell migration. Our results reveal a novel mechanism of inhibiting host cell motility by L. pneumophila for its virulence.