Quantification of real-time Salmonella effector type III secretion kinetics reveals differential secretion rates for SopE2 and SptP.
Gram-negative pathogenic bacteria such as Salmonella utilize the type III secretion system to inject bacterial effector proteins into a host cell. Upon entry, these effectors bind mammalian cell proteins, hijack cellular signaling pathways, and redirect cellular function, thus enabling bacterial infection. In this study we use the FlAsH/tetracysteine labeling system to fluorescently tag specific effectors in Salmonella to observe real-time secretion of these proteins into a mammalian host cell. The tetracysteine tag is genomically incorporated, thus preserving endogenous control of bacterial effectors. We demonstrate that two effectors, SopE2 and SptP, exhibit different secretion kinetics, as well as different rates of degradation within the host cell. These proteins respectively activate and suppress GTPase Cdc42, suggesting that there is a temporal hierarchy for effector delivery and persistence within the cell that is directly related to effector function.
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.
Schuyler B
SB
Van Engelenburg
Amy E
AE
Palmer
D001426:Bacterial Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D007700:Kinetics; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000378:metabolism*
D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D020662:Guanine Nucleotide Exchange Factors; C436324:SopE2 protein, Salmonella typhimurium; D017027:Protein Tyrosine Phosphatases; C439890:sptP protein, Salmonella typhimurium