The Translocated Salmonella Effector Proteins SseF and SseG Interact and Are Required To Establish an Intracellular Replication Niche

Abstract

The facultative intracellular pathogen Salmonella enterica causes a variety of diseases, including gastroenteritis and typhoid fever. Inside epithelial cells, Salmonella replicates in vacuoles, which localize in the perinuclear area in close proximity to the Golgi apparatus. Among the effector proteins translocated by the Salmonella pathogenicity island 2-encoded type III secretion system, SifA and SseG have been shown necessary but not sufficient to ensure the intracellular positioning of Salmonella vacuoles. Hence, we have investigated the involvement of other secreted effector proteins in this process. Here we show that SseF interacts functionally and physically with SseG but not SifA and is also required for the perinuclear localization of Salmonella vacuoles. The observations show that the intracellular positioning of Salmonella vacuoles is a complex phenomenon resulting from the combined action of several effector proteins.

The Salmonella-containing vacuole—Moving with the times

“…Redistribution of SCVs from the cell periphery to the MTOC/juxtanuclear region is mediated at least in part by the small GTP-binding protein rab7 together with its effector RILP, which are required for recruitment of the microtubule-based motor dynein [40][41][42]. Once at the MTOC two T3SS2 effectors that have the ability to interact with one another, SseG and SseF, are required to maintain SCV positioning over longer periods of time [43][44][45]. SseF and SseG, together with SifA, have also been shown to be involved in redirecting exocytic cargo vesicles to the SCV [46].…”

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

“…SopD2 associates to late endosome and can contribute to SIF formation by targeting endocytic vesicles to the SCV and nascent tubules [59]. Finally, SseF and SseG mediate bundling of microtubules near the SCV that can promote fusion of aggregated vesicles into tubules [60]. SISTs also contain SCAMP3 and T3SS2 effectors but lack LAMP1 and other late endocytic markers [58].…”

“…These bundles serve as a scaffold for SIF formation [335]. In addition to its role in SIF formation, SseG and SseF physically interact with each other and have a role in the targeting of the SCV to the vicinity of the Golgi network in infected epithelial cells [60,336,337]. SseG is targeted specifically to the trans-Golgi network through a predicted transmembrane domain located in the middle of the protein.…”

Meeting report: Adaptation and communication of bacterial pathogens

“…Both proteins are located in the Salmonella-containing vacuole (SCV) membrane and interact with each other. 24 SseF and SseG were shown to mediate association of SCVs with the Golgi network within epithelial cells. A yeast 2-hybrid screen identified a host cell Golgi protein that interacts with both SseG and SseF.…”