SipA Activation of Caspase-3 Is a Decisive Mediator of Host Cell Survival at Early Stages of Salmonella enterica Serovar Typhimurium Infection

McIntosh, Anne; Meikle, Lynsey M.; Ormsby, Michael J.; McCormick, Beth A.; Christie, John M.; Brewer, James M.; Roberts, Mark; Wall, Daniel M.

doi:10.1128/iai.00393-17

Cited by 31 publications

(31 citation statements)

References 49 publications

(80 reference statements)

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“…2015). Other activities that have been attributed to SipA include Caspase-3 cleavage and activation (Cain et al, 2008;McIntosh et al, 2017), induction of CXC chemokine expression through phosphorylation of IL-8-transcription regulatory proteins, JUN and p38MAK (Figueiredo et al, 2009) and promoting fusion with early endosomes (Singh et al, 2018). Of relevance to this study, several groups have shown that SipA is also involved in intracellular replication, with the consensus being that it promotes vacuolar replication (Brawn et al, 2007;Klein et al, 2017;Singh et al, 2018;Zhang et al, 2018).…”

Section: Discussionmentioning

confidence: 90%

“…It displaces host actin‐binding proteins from F‐actin and prevents actin severing, thus contributing to the actin cytoskeleton rearrangements that are required for Salmonella invasion (Zhou et al , ; McGhie et al , ; Higashide et al , ; Lilic et al , ; McGhie et al , ; Lhocine et al , ). Other activities that have been attributed to SipA include Caspase‐3 cleavage and activation (Cain et al , ; McIntosh et al , ), induction of CXC chemokine expression through phosphorylation of IL‐8‐transcription regulatory proteins, JUN and p38MAK (Figueiredo et al , ) and promoting fusion with early endosomes (Singh et al , ). Of relevance to this study, several groups have shown that SipA is also involved in intracellular replication, with the consensus being that it promotes vacuolar replication (Brawn et al , ; Klein et al , ; Singh et al , ; Zhang et al , ).…”

Section: Discussionmentioning

confidence: 99%

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A role for the Salmonella Type III Secretion System 1 in bacterial adaptation to the cytosol of epithelial cells

Chong

Starr

Finn

et al. 2019

Molecular Microbiology

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Summary Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that invades the intestinal epithelium. Following invasion of epithelial cells, Salmonella survives and replicates within two distinct intracellular niches. While all of the bacteria are initially taken up into a membrane bound vacuole, the Salmonella‐containing vacuole or SCV, a significant proportion of them promptly escape into the cytosol. Cytosolic Salmonella replicates more rapidly compared to the vacuolar population, although the reasons for this are not well understood. SipA, a multi‐function effector protein, has been shown to affect intracellular replication and is secreted by cytosolic Salmonella via the invasion‐associated Type III Secretion System 1 (T3SS1). Here, we have used a multipronged microscopy approach to show that SipA does not affect bacterial replication rates per se, but rather mediates intra‐cytosolic survival and/or initiation of replication following bacterial egress from the SCV. Altogether, our findings reveal an important role for SipA in the early survival of cytosolic Salmonella.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

A role for the Salmonella Type III Secretion System 1 in bacterial adaptation to the cytosol of epithelial cells

Chong

Starr

Finn

et al. 2019

Molecular Microbiology

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“…Since sipA was cloned into pUC57-phiLOV using the same cloning sites, the pUC57-SipA-phiLOV plasmid was digested with SacI and XhoI (NEB) to remove sipA, and then gel purified. 19 The sifA PCR product was similarly digested and purified and ligated to pUC57-phiLOV before being transformed in the same manner as pGST-SifA. Plasmid DNA was then isolated from transformants that had ampicillin resistance and transformed into electrocompetent ΔSifA.…”

Section: -δSifamentioning

confidence: 99%

Caspase-3 cleavage of Salmonella type III secreted effector protein SifA is required for localization of functional domains and bacterial dissemination

et al. 2019

Self Cite

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SifA is a bi-functional Type III Secretion System (T3SS) effector protein that plays an important role in Salmonella virulence. The N-terminal domain of SifA binds SifA-Kinesin-Interacting-Protein (SKIP), and via an interaction with kinesin, forms tubular membrane extensions called Sif filaments (Sifs) that emanate from the Salmonella Containing Vacuole (SCV). The C-terminal domain of SifA harbors a WxxxE motif that functions to mimic active host cell GTPases. Taken together, SifA functions in inducing endosomal tubulation in order to maintain the integrity of the SCV and promote bacterial dissemination. Since SifA performs multiple, unrelated functions, the objective of this study was to determine how each functional domain of SifA becomes processed. Our work demonstrates that a linker region containing a caspase-3 cleavage motif separates the two functional domains of SifA. To test the hypothesis that processing of SifA by caspase-3 at this particular site is required for function and proper localization of the effector protein domains, we developed two tracking methods to analyze the intracellular localization of SifA. We first adapted a fluorescent tag called phiLOV that allowed for type-III secretion system (T3SS) mediated delivery of SifA and observation of its intracellular colocalization with caspase-3. Additionally, we created a dual-tagging strategy that permitted tracking of each of the SifA functional domains following caspase-3 cleavage to different subcellular locations. The results of this study reveal that caspase-3 cleavage of SifA is required for the proper localization of functional domains and bacterial dissemination. Considering the importance of these events in Salmonella pathogenesis, we conclude that caspase-3 cleavage of effector proteins is a more broadly applicable effector processing mechanism utilized by Salmonella to invade and persist during infection.

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“…Moreover, research had shown that the cAMP receptor protein of S. Typhimurium could induce the macrophage apoptosis [32]. Based on previous functional studies of Salmonella genes in macrophages [15,25,[33][34][35], we used the WT, ΔsseK3 mutant, and sseK3-complemented strains to infect the macrophages to determine the relationship between S. Typhimurium sseK3 and macrophages apoptosis. We found that the adherence and invasion percentages in the ΔsseK3 mutant group were similar to those of WT group and sseK3-complemented group during the infecting period (P > 0.05), which con rmed that the WT, ΔsseK3 mutant, and sseK3complemented strains had the same level going through into the macrophages.…”

Section: Discussionmentioning

confidence: 99%

Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages

Chen

Zhang

et al. 2020

Preprint

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Background: Salmonella enterica serovar Typhimurium ( S. Typhimurium) is an important infectious disease pathogen that can survive and replicate in macrophages. Glycolysis is essential for immune responses against S. Typhimurium infection in macrophages, and is also associated with apoptosis. S. Typhimurium secreted effector K3 (SseK3) was recently identified as a novel translated and secreted protein. However, there is no study about the role of sseK3 in the relationship between apoptosis and glycolysis in cells infected with S. Typhimurium. It is unclear whether this protein exerts a significant role in the progress of apoptosis and glycolysis in S. Typhimurium-infected macrophages. Results: Macrophages were infected with S. Typhimurium SL1344 wild-type (WT), Δ sseK3 mutant or sseK3 -complemented strain, and the effects of sseK3 on apoptosis and glycolysis were determined. The adherence and invasion in the Δ sseK3 mutant group were similar to that in the WT and sseK3 -complemented groups, indicating that SseK3 was not essential for the adherence and invasion of S. Typhimurium in macrophages. However, the percentage of apoptosis in the Δ sseK3 mutant group was much lower than that in the WT and sseK3 -complemented groups. Caspase-3, caspase-8, and caspase-9 enzyme activity in the Δ sseK3 mutant group were significantly lower than in the WT group and sseK3 -complemented groups, indicating that sseK3 could improve the caspase-3, caspase-8, and caspase-9 enzyme activity. We also found that there were no significant differences in pyruvic acid levels between the three groups, but the lactic acid level in the Δ sseK3 mutant group was much lower than that in the WT and sseK3 -complemented groups. The ATP levels in the Δ sseK3 mutant group were remarkably higher than those in the WT and sseK3 -complemented groups. These indicated that the sseK3 enhanced the level of glycolysis in macrophages infected by S. Typhimurium. Conclusions: S. Typhimurium sseK3 is likely involved in promoting macrophage apoptosis and modulating glycolysis in macrophages. Our results could improve our understanding of the relationship between apoptosis and glycolysis in macrophages induced by S. Typhimurium sseK3 .

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SipA Activation of Caspase-3 Is a Decisive Mediator of Host Cell Survival at Early Stages of Salmonella enterica Serovar Typhimurium Infection

Cited by 31 publications

References 49 publications

A role for the Salmonella Type III Secretion System 1 in bacterial adaptation to the cytosol of epithelial cells

A role for the Salmonella Type III Secretion System 1 in bacterial adaptation to the cytosol of epithelial cells

Caspase-3 cleavage of Salmonella type III secreted effector protein SifA is required for localization of functional domains and bacterial dissemination

Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages

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