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SifA, a Type III Secreted Effector of Salmonella typhimurium , Directs Salmonella ‐Induced Filament (Sif) Formation Along Microtubules
Author(s) -
Brumell John H.,
Goosney Danika L.,
Finlay B. Brett
Publication year - 2002
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1034/j.1600-0854.2002.30604.x
Subject(s) - biology , microtubule , microbiology and biotechnology , vacuole , effector , type three secretion system , salmonella enterica , secretion , salmonella , nocodazole , virulence , cytoplasm , cytoskeleton , biochemistry , cell , bacteria , genetics , gene
A unique feature of Salmonella enterica serovar typhimurium ( S. typhimurium ) is its ability to enter into (invade) epithelial cells and elongate the vacuole it occupies into tubular structures called Salmonella ‐induced filaments (Sifs). This phenotype is dependent on SifA, a Salmonella virulence factor that requires the SPI‐2‐encoded type III secretion system for delivery into host cells. Previous attempts to study SifA and other type III secreted proteins have been limited by a lack of suitable reagents. We examined SifA function by expressing SifA with two internal hemagglutinin epitope tags. By employing subcellular fractionation techniques, we determined that translocated SifA was membrane associated in infected HeLa cells. Confocal microscopy revealed that SifA associated with the Salmonella vacuole and with Sifs. Our analysis also revealed that microtubules serve as a scaffold for Sifs, and that SifA colocalizes with microtubules at sites of interaction between lysosomal glycoprotein‐containing vesicles and Sifs. Treatment with the microtubule inhibitor nocodazole blocked Sif formation but did not prevent SifA translocation into the Salmonella vacuole. While polymerized actin has been observed on Sifs, this phenotype was transient and did not play a role in promoting or maintaining Sif formation. Our findings demonstrate the essential role of microtubule dynamics in the formation of Sifs and the utility of this epitope tagging strategy for the study of bacterial type III secreted proteins.