Salmonella type III effectors PipB and PipB2 are targeted to detergent-resistant microdomains on internal host cell membranes.
The intracellular pathogen, Salmonella enterica, translocates type III effectors across its vacuolar membrane into host cells. Herein we describe a new Salmonella effector, PipB2, which has sequence similarity to another type III effector, PipB. In phagocytic cells, PipB2 localizes to the Salmonella-containing vacuole (SCV) and tubular extensions from the SCV, Salmonella-induced filaments (Sifs). We used the specific targeting of PipB2 in macrophages to characterize Sifs in phagocytic cells for the first time. In epithelial cells, PipB2 has a unique localization pattern, localizing to SCVs and Sifs and additionally to vesicles at the periphery of infected cells. We further show that the N-terminal 225-amino-acid residues of PipB2 are sufficient for type III translocation and association with SCVs and Sifs, but not peripheral vesicles. Subcellular fractionation demonstrated that both PipB and PipB2 associate with host cell membranes and resist extraction by high salt, high pH and to a significant extent, non-ionic detergent. Furthermore, PipB and PipB2 are enriched in detergent-resistant microdomains (DRMs), also known as lipid rafts, present on membranes of SCVs and Sifs. The enrichment of Salmonella effectors in DRMs on these intracellular membranes probably permits specific interactions with host cell molecules that are concentrated in these signalling platforms.
Knodler
Leigh A
LA
Biotechnology Laboratory, University of British Columbia, Vancouver, BC, Canada. lknodler@niaid.nih.gov
Vallance
Bruce A
BA
Hensel
Michael
M
Jäckel
Daniela
D
Finlay
B Brett
BB
Steele-Mortimer
Olivia
O
D008841:Actin Cytoskeleton / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line / Q000382:microbiology; D003902:Detergents / Q000494:pharmacology; D005260:Female; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000382:microbiology / Q000648:ultrastructure; D021962:Membrane Microdomains / Q000737:chemistry* / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008870:Microtubules / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D017830:Octoxynol / Q000494:pharmacology; D010587:Phagocytosis; D021381:Protein Transport; D018085:Regulon / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000382:microbiology
D001426:Bacterial Proteins; D003902:Detergents; D008565:Membrane Proteins; C478164:PipB protein, Salmonella enterica; C478165:PipB2 protein, Salmonella enterica; C440638:SPI-2 protein, Salmonella; D007371:Interferon-gamma; D017830:Octoxynol