Abstract
Salmonella is an intracellular bacterial pathogen that replicates within a membrane-bound vacuole in host cells. The major lysosomal membrane proteins 1 and 2 (LAMP-1 and LAMP-2) are recruited to the Salmonella-containing vacuole as well as Salmonella- associated filaments (Sifs) that emerge from the vacuole. LAMP-1 is a dominant membrane marker for the vacuole and Sifs. Its colocalization with both is dependent on a major secreted bacterial virulence protein, SifA. Here, we show that SifA is required for the recruitment of LAMP-2 and can be used as a second independent marker for both the bacterial vacuolar membrane and Sifs. Further, RNAi studies revealed that in LAMP-1 depleted cells, the bacteria remain membrane bound as measured by their association with LAMP-2 protein. In contrast, LAMP-2 depletion increased the amount of LAMP-1 free bacteria. Together, the data suggests that despite its abundance, LAMP-1 is not essential, but LAMP-2 may be partially important for the Salmonella-containing vacuolar membrane.
Highlights
Salmonella infection causes millions of infections each year resulting in hundreds of thousands of deaths [1]
Multiple studies have shown that lysosome-associated membrane protein-1 (LAMP-1) is recruited by the Salmonella containing vacuole (SCV) and that LAMP-1 is localized to Salmonella- associated filaments (Sifs) [2,8,9]
Several papers have indicated that LAMP-2 is localized to the SCV, but a comparative, side-by-side analysis of LAMP-2 and LAMP-1 recruitment to the SCV and Sifs has not been undertaken
Summary
Salmonella infection causes millions of infections each year resulting in hundreds of thousands of deaths [1]. Serovar S. typhimurium, in particular, causes gastroenteritis in humans and enteric fever in animal hosts [2]. It is classified as a biodefense agent because it has the potential, and has been used to deliberately contaminate the food and water supply [3]. Salmonella is a facultative, intracellular, bacterial pathogen that replicates within a membrane-bound vacuole in both epithelial cells and in macrophages [4]. Infection initially occurs in the gastrointestinal tract as a result of ingesting contaminated foods. Salmonella serovars capable of causing systemic infection survive and replicates inside macrophages of the spleen and liver [5]
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