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Functional plasticity in the type IV secretion system of Helicobacter pylori.

Barrozo RM, Cooke CL, Hansen LM, Lam AM, Gaddy JA, Johnson EM, Cariaga TA, Suarez G, Peek RM, Cover TL, Solnick JV - PLoS Pathog. (2013)

Bottom Line: CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions.Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS.We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

ABSTRACT
Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

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CagY decorates the H. pylori bacterial surface but is not associated with T4SS pili.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1, incubated with antibodies to the CagY MRR or CagA, and imaged by FEG-SEM in the environmental mode. CagY was detected on the bacterial surface of the WT strain but was not associated with pili. CagA was detected both on the bacterial surface and in close approximation to the tips of the pili of the WT strain. There was markedly reduced CagA labeling on the surface of ▵cagY mutant strain compared to the WT strain. No staining was seen when primary antibody was omitted. Pili are sometimes not as well visualized and more often appear broken in these images compared to Figure 7 due to the lack of metal coating and more frequent washes. Magnification bars indicate 500 nm.
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ppat-1003189-g008: CagY decorates the H. pylori bacterial surface but is not associated with T4SS pili.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1, incubated with antibodies to the CagY MRR or CagA, and imaged by FEG-SEM in the environmental mode. CagY was detected on the bacterial surface of the WT strain but was not associated with pili. CagA was detected both on the bacterial surface and in close approximation to the tips of the pili of the WT strain. There was markedly reduced CagA labeling on the surface of ▵cagY mutant strain compared to the WT strain. No staining was seen when primary antibody was omitted. Pili are sometimes not as well visualized and more often appear broken in these images compared to Figure 7 due to the lack of metal coating and more frequent washes. Magnification bars indicate 500 nm.

Mentions: Pilus structures were also seen in H. pylori J166 with a deletion of cagY (Figure 7); similar results were obtained with a cagY deletion in H. pylori strain 26695 (Figure 7). To investigate the cellular localization of CagY, we performed immunogold SEM using antibody to the CagY MRR to stain H. pylori co-cultured with AGS cells. Antibody to CagA was used as a positive control. Although CagY label was seen scattered over the bacterial cells in WT H. pylori, no staining was found on or near the pilus structure (Figure 8). In contrast, CagA was identified both on the cell surface and closely approximated to the tips of pili in WT H. pylori, which has been reported previously [2]. CagA was not detected in association with pili in a cagY deletion mutant, in which the T4SS is not functional, and there was markedly reduced CagA labeling on the surface of the cagY mutant bacteria compared to WT (Figure 8). The absence of detectable CagY in association with pili is consistent with the finding that a ΔcagY mutant produces pili that are indistinguishable from those in the WT strain. Together, the EM results suggest that the loss of function that occurs with changes in CagY results from a functional change in the T4SS without any detectable structural defect in the T4SS pilus.


Functional plasticity in the type IV secretion system of Helicobacter pylori.

Barrozo RM, Cooke CL, Hansen LM, Lam AM, Gaddy JA, Johnson EM, Cariaga TA, Suarez G, Peek RM, Cover TL, Solnick JV - PLoS Pathog. (2013)

CagY decorates the H. pylori bacterial surface but is not associated with T4SS pili.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1, incubated with antibodies to the CagY MRR or CagA, and imaged by FEG-SEM in the environmental mode. CagY was detected on the bacterial surface of the WT strain but was not associated with pili. CagA was detected both on the bacterial surface and in close approximation to the tips of the pili of the WT strain. There was markedly reduced CagA labeling on the surface of ▵cagY mutant strain compared to the WT strain. No staining was seen when primary antibody was omitted. Pili are sometimes not as well visualized and more often appear broken in these images compared to Figure 7 due to the lack of metal coating and more frequent washes. Magnification bars indicate 500 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585145&req=5

ppat-1003189-g008: CagY decorates the H. pylori bacterial surface but is not associated with T4SS pili.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1, incubated with antibodies to the CagY MRR or CagA, and imaged by FEG-SEM in the environmental mode. CagY was detected on the bacterial surface of the WT strain but was not associated with pili. CagA was detected both on the bacterial surface and in close approximation to the tips of the pili of the WT strain. There was markedly reduced CagA labeling on the surface of ▵cagY mutant strain compared to the WT strain. No staining was seen when primary antibody was omitted. Pili are sometimes not as well visualized and more often appear broken in these images compared to Figure 7 due to the lack of metal coating and more frequent washes. Magnification bars indicate 500 nm.
Mentions: Pilus structures were also seen in H. pylori J166 with a deletion of cagY (Figure 7); similar results were obtained with a cagY deletion in H. pylori strain 26695 (Figure 7). To investigate the cellular localization of CagY, we performed immunogold SEM using antibody to the CagY MRR to stain H. pylori co-cultured with AGS cells. Antibody to CagA was used as a positive control. Although CagY label was seen scattered over the bacterial cells in WT H. pylori, no staining was found on or near the pilus structure (Figure 8). In contrast, CagA was identified both on the cell surface and closely approximated to the tips of pili in WT H. pylori, which has been reported previously [2]. CagA was not detected in association with pili in a cagY deletion mutant, in which the T4SS is not functional, and there was markedly reduced CagA labeling on the surface of the cagY mutant bacteria compared to WT (Figure 8). The absence of detectable CagY in association with pili is consistent with the finding that a ΔcagY mutant produces pili that are indistinguishable from those in the WT strain. Together, the EM results suggest that the loss of function that occurs with changes in CagY results from a functional change in the T4SS without any detectable structural defect in the T4SS pilus.

Bottom Line: CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions.Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS.We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

ABSTRACT
Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

Show MeSH
Related in: MedlinePlus