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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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Changes in the motif structure of the CagY middle repeat region that alter the function of the cagPAI do not affect expression of T4SS pili on the bacterial surface.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1 and imaged by FEG-SEM. T4SS pilus structures were readily apparent in the WT H. pylori J166 but not in the cagPAI deletion mutant (J166▵cagPAI). T4SS pili were also observed in H. pylori J166 in which the WT cagY allele was replaced with that from output strains with a functional (rOut3, mOut3) or a non-functional (rOut2 mOut2) cagPAI. Pili were also seen in H. pylori strains J166 and 26695 with deletions in cagY. Magnification bars indicate 500 nm.
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ppat-1003189-g007: Changes in the motif structure of the CagY middle repeat region that alter the function of the cagPAI do not affect expression of T4SS pili on the bacterial surface.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1 and imaged by FEG-SEM. T4SS pilus structures were readily apparent in the WT H. pylori J166 but not in the cagPAI deletion mutant (J166▵cagPAI). T4SS pili were also observed in H. pylori J166 in which the WT cagY allele was replaced with that from output strains with a functional (rOut3, mOut3) or a non-functional (rOut2 mOut2) cagPAI. Pili were also seen in H. pylori strains J166 and 26695 with deletions in cagY. Magnification bars indicate 500 nm.

Mentions: Output colonies that have variant cagY alleles and no longer induce IL-8 still express CagY (Figures 2 and 4), but they might not make T4SS pili, or the pili might have altered structural features. To test this possibility, we used field emission scanning electron microscopy (FEG-SEM) to image H. pylori strains co-cultured with AGS cells. As expected, WT J166 but not a cagPAI deletion mutant produced pilus-like structures (Figure 7). This is consistent with previous studies demonstrating that the cagPAI is essential for the formation of a T4SS [2], [15], [31], [32]. Pili of similar dimensions were previously reported to be present in WT strain 26695, but absent in H. pylori 26695 with deletions of cagT, cagE, cagL, and cagI, all of which are required for a functional T4SS [15]. Using this imaging approach, we examined isogenic strains of H. pylori J166 in which the cagY gene had been replaced with alleles from strains that did (rOut3, mOut3) or did not (rOut2, mOut2) induce IL-8 and translocate CagA (Figures 2 and 4). Regardless of cagPAI functionality, all strains made pilus structures (Figure 7). Although the pili were less prominent on some strains that had defects in T4SS function, we were unable to identify a reproducible association between cagPAI function and quantitative measures of pilus number or morphology (Table S1).


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)

Changes in the motif structure of the CagY middle repeat region that alter the function of the cagPAI do not affect expression of T4SS pili on the bacterial surface.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1 and imaged by FEG-SEM. T4SS pilus structures were readily apparent in the WT H. pylori J166 but not in the cagPAI deletion mutant (J166▵cagPAI). T4SS pili were also observed in H. pylori J166 in which the WT cagY allele was replaced with that from output strains with a functional (rOut3, mOut3) or a non-functional (rOut2 mOut2) cagPAI. Pili were also seen in H. pylori strains J166 and 26695 with deletions in cagY. Magnification bars indicate 500 nm.
© Copyright Policy
Related In: Results  -  Collection

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

ppat-1003189-g007: Changes in the motif structure of the CagY middle repeat region that alter the function of the cagPAI do not affect expression of T4SS pili on the bacterial surface.H. pylori was co-cultured with AGS gastric cells at an MOI of 100∶1 and imaged by FEG-SEM. T4SS pilus structures were readily apparent in the WT H. pylori J166 but not in the cagPAI deletion mutant (J166▵cagPAI). T4SS pili were also observed in H. pylori J166 in which the WT cagY allele was replaced with that from output strains with a functional (rOut3, mOut3) or a non-functional (rOut2 mOut2) cagPAI. Pili were also seen in H. pylori strains J166 and 26695 with deletions in cagY. Magnification bars indicate 500 nm.
Mentions: Output colonies that have variant cagY alleles and no longer induce IL-8 still express CagY (Figures 2 and 4), but they might not make T4SS pili, or the pili might have altered structural features. To test this possibility, we used field emission scanning electron microscopy (FEG-SEM) to image H. pylori strains co-cultured with AGS cells. As expected, WT J166 but not a cagPAI deletion mutant produced pilus-like structures (Figure 7). This is consistent with previous studies demonstrating that the cagPAI is essential for the formation of a T4SS [2], [15], [31], [32]. Pili of similar dimensions were previously reported to be present in WT strain 26695, but absent in H. pylori 26695 with deletions of cagT, cagE, cagL, and cagI, all of which are required for a functional T4SS [15]. Using this imaging approach, we examined isogenic strains of H. pylori J166 in which the cagY gene had been replaced with alleles from strains that did (rOut3, mOut3) or did not (rOut2, mOut2) induce IL-8 and translocate CagA (Figures 2 and 4). Regardless of cagPAI functionality, all strains made pilus structures (Figure 7). Although the pili were less prominent on some strains that had defects in T4SS function, we were unable to identify a reproducible association between cagPAI function and quantitative measures of pilus number or morphology (Table S1).

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