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Vol. 16, Issue 9, 4108-4123, September 2005
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Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840
Submitted April 29, 2005;
Revised June 16, 2005;
Accepted June 17, 2005
Monitoring Editor: Ralph Isberg
After internalization into mammalian cells, the bacterial pathogen Salmonella enterica resides within a membrane-bound compartment, the Salmonella-containing vacuole (SCV). During its maturation process, the SCV interacts extensively with host cell endocytic compartments, especially late endosomes/lysosomes (LE/Lys) at later stages. These interactions are mediated by the activities of multiple bacterial and host cell proteins. Here, we show that the Salmonella type III effector PipB2 reorganizes LE/Lys compartments in mammalian cells. This activity results in the centrifugal extension of lysosomal glycoprotein-rich membrane tubules, known as Salmonella-induced filaments, away from the SCV along microtubules. Salmonella overexpressing pipB2 induce the peripheral accumulation of LE/Lys compartments, reducing the frequency of LE/Lys tubulation. Furthermore, ectopic expression of pipB2 redistributes LE/Lys, but not other cellular organelles, to the cell periphery. In coexpression studies, PipB2 can overcome the effects of dominant-active Rab7 or Rab34 on LE/Lys positioning. Deletion of a C-terminal pentapeptide motif of PipB2, LFNEF, prevents its peripheral targeting and effect on organelle positioning. The PipB2 homologue PipB does not possess this motif or the same biological activity as PipB2. Therefore, it seems that a divergence in the biological functions of these two effectors can be accounted for by sequence divergence in their C termini.
Abbreviations used: GFP, green fluorescent protein; HA, hemagglutinin; LAMP, lysosomal-associated membrane protein; LBPA, lysobisphosphatidic acid; LE/Lys, late endosomes/lysosomes; lgp, lysosomal glycoprotein; LPS, lipopolysaccharide; NDZ, nocodazole; PFA, paraformaldehyde; p.i., postinfection; RILP, Rab-interacting lysosomal protein; SCV, Salmonella-containing vacuole; Sif, Salmonella-induced filament; SPI, Salmonella pathogenicity island; TTSS, type III secretion system.
The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).
Address correspondence to: Leigh A. Knodler (lknodler{at}niaid.nih.gov).
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