Salmonella exploits USP32 to coordinate Rab14 and Rab11 recycling pathways for intracellular survival

Abstract

Many intracellular bacterial pathogens establish membrane-bound niches derived from host material to survive and replicate within host cells. These compartments are carved through subversion of host intracellular trafficking pathways to modulate the composition of the vacuolar membrane. Although recycling-associated small Rab GTPases are frequently observed at infection sites, their role in membrane remodeling and cargo sorting has remained poorly understood. Here, we leverage the extensive early membrane remodeling occurring during Salmonella infection to dissect this process. Using endogenously tagged cell lines, we characterize the dynamics of the recycling small GTPases Rab14 and Rab11 at Salmonella intracellular infection sites. We report that Rab14 recruits its effector Rufy1, which mediates sorting of CI-M6PR through recycling tubules. Subsequently, Rab11 disperses the newly formed recycling endosomes by interacting with its effector Fip3 for retrograde transport. This pathway is controlled by the deubiquitinating enzyme USP32, which targets both Rab14 and Rab11, enhancing their interactions with Rufy1 and Fip3, respectively. We further show that USP32 is recruited to the infection site via local enrichment of phosphatidylserine-positive membranes, a process triggered by the Salmonella effector proteins SopE/E2. Importantly, silencing USP32 significantly impairs intracellular bacterial survival. Our findings reveal a remarkable exploitation of host signaling and trafficking pathways by Salmonella to construct a replication-permissive niche. Targeting these pathways may offer new strategies for therapeutic intervention against intracellular bacterial infections.