Salmonella trafficking is defined by continuous dynamic interactions with the endolysosomal system.
Following invasion of non-phagocytic host cells, Salmonella enterica survives and replicates within a phagosome-like compartment known as the Salmonella-containing vacuole (SCV). It is now well established that SCV biogenesis, like phagosome biogenesis, involves sequential interactions with the endocytic pathway. However, Salmonella is believed to limit these interactions and, in particular, to avoid fusion of terminal lysosomes with the SCV. In this study, we reassessed this process using a high-resolution live-cell imaging approach and found an unanticipated level of interaction between the SCV and the endocytic pathway. Direct interactions, in which late endosomal/lysosomal content was transferred to SCVs, were detected within 30 min of invasion and continued for several hours. Mechanistically, these interactions were very similar to phagosome-lysosome fusion because they were accompanied by rapid acidification of the SCV, could be blocked by chemical perturbation of microtubules or vacuolar acidification and involved the smallGTPase Rab7. In comparison with vacuoles containing internalized Escherichia coli or heat-killed Salmonella, SCVs did show some delay of fusion and acidification, although, this appeared to be independent of either type III secretion system. These results provide compelling evidence that inhibition of SCV-lysosome fusion is not the major determinant in establishment of the Salmonella replicative niche in epithelial cells.
Drecktrah
Dan
D
Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA.
Knodler
Leigh A
LA
Howe
Dale
D
Steele-Mortimer
Olivia
O
D015415:Biomarkers; D045744:Cell Line, Tumor; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism; D012486:Salmonella typhimurium / Q000378:metabolism*; D014617:Vacuoles / Q000382:microbiology*; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D015415:Biomarkers; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; D020691:rab GTP-Binding Proteins