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Role of AmiA in the morphological transition of Helicobacter pylori and in immune escape.

Chaput C, Ecobichon C, Cayet N, Girardin SE, Werts C, Guadagnini S, Prévost MC, Mengin-Lecreulx D, Labigne A, Boneca IG - PLoS Pathog. (2006)

Bottom Line: Both in vitro and in the human stomach it can be found in two forms, the bacillary and coccoid forms.PG modification and transformation of H. pylori was accompanied by an escape from detection by human Nod1 and the absence of NF-kappaB activation in epithelial cells.Accordingly, coccoids were unable to induce IL-8 secretion by AGS gastric epithelial cells. amiA is, to our knowledge, the first genetic determinant discovered to be required for this morphological transition into the coccoid forms, and therefore contributes to modulation of the host response and participates in the chronicity of H. pylori infection.

View Article: PubMed Central - PubMed

Affiliation: Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, Paris, France.

ABSTRACT
The human gastric pathogen Helicobacter pylori is responsible for peptic ulcers and neoplasia. Both in vitro and in the human stomach it can be found in two forms, the bacillary and coccoid forms. The molecular mechanisms of the morphological transition between these two forms and the role of coccoids remain largely unknown. The peptidoglycan (PG) layer is a major determinant of bacterial cell shape, and therefore we studied H. pylori PG structure during the morphological transition. The transition correlated with an accumulation of the N-acetyl-D-glucosaminyl-beta(1,4)-N-acetylmuramyl-L-Ala-D-Glu (GM-dipeptide) motif. We investigated the molecular mechanisms responsible for the GM-dipeptide motif accumulation, and studied the role of various putative PG hydrolases in this process. Interestingly, a mutant strain with a mutation in the amiA gene, encoding a putative PG hydrolase, was impaired in accumulating the GM-dipeptide motif and transforming into coccoids. We investigated the role of the morphological transition and the PG modification in the biology of H. pylori. PG modification and transformation of H. pylori was accompanied by an escape from detection by human Nod1 and the absence of NF-kappaB activation in epithelial cells. Accordingly, coccoids were unable to induce IL-8 secretion by AGS gastric epithelial cells. amiA is, to our knowledge, the first genetic determinant discovered to be required for this morphological transition into the coccoid forms, and therefore contributes to modulation of the host response and participates in the chronicity of H. pylori infection.

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Muropeptide Profile of H. pylori PGPG from parental strain 26695 (A) and its amiA isogenic mutant (B) were purified and digested with the muramidase M1 (mutanolysin). The generated muropeptides were separated by HPLC. The HPLC profiles show muropeptide composition after 8 h, 24 h, and 48 h of bacterial growth. Each peak structure was assigned by MALDI-TOF mass spectrometry and corresponds to a different muropeptide: (1) GM-tripeptide, (2) GM-tetrapeptide, (3) GM-tetrapeptide-glycine, (4) GM-dipeptide, and (5) GM-pentapeptide. Dimers were then eluted: (6) GM-tetrapeptide-tripeptide-MG, (7) GM-tetrapeptide-tetrapeptide-glycine-MG, (8) GM-tetrapeptide-tetrapeptide-MG, and (9) GM-tetrapeptide-pentapeptide-MG. Finally, anhydromuropeptides were eluted: (10) G(anh)M-pentapeptide, (11) and (12) G(anh)M-tetrapeptide-tripeptide-MG, (13) and (14) G(anh)M-tetrapeptide-tetrapeptide-MG, and (15) G(anh)M-tetrapeptide-pentapeptide-MG.
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ppat-0020097-g001: Muropeptide Profile of H. pylori PGPG from parental strain 26695 (A) and its amiA isogenic mutant (B) were purified and digested with the muramidase M1 (mutanolysin). The generated muropeptides were separated by HPLC. The HPLC profiles show muropeptide composition after 8 h, 24 h, and 48 h of bacterial growth. Each peak structure was assigned by MALDI-TOF mass spectrometry and corresponds to a different muropeptide: (1) GM-tripeptide, (2) GM-tetrapeptide, (3) GM-tetrapeptide-glycine, (4) GM-dipeptide, and (5) GM-pentapeptide. Dimers were then eluted: (6) GM-tetrapeptide-tripeptide-MG, (7) GM-tetrapeptide-tetrapeptide-glycine-MG, (8) GM-tetrapeptide-tetrapeptide-MG, and (9) GM-tetrapeptide-pentapeptide-MG. Finally, anhydromuropeptides were eluted: (10) G(anh)M-pentapeptide, (11) and (12) G(anh)M-tetrapeptide-tripeptide-MG, (13) and (14) G(anh)M-tetrapeptide-tetrapeptide-MG, and (15) G(anh)M-tetrapeptide-pentapeptide-MG.

Mentions: We purified and analyzed the PG from the sequenced strain 26695 and from the strain NCTC11637 used as a control. No major difference between chromatograms of the two strains was observed (Figures 1 and S1). Muropeptide composition analysis of H. pylori PG showed an accumulation of the GM-dipeptide motif in strain 26695 during the stationary phase, as previously observed in strain NCTC11637 (Figures 1 and S1; [27]). Interestingly, the accumulation of the GM-dipeptide (peak 4 in Figures 1 and S1) coincided with a decrease of N-acetyl-D-glucosaminyl-β(1,4)-N-acetylmuramyl-L-Ala–γ-D-Glu-mesoDAP (GM-tripeptide) (peak 1).


Role of AmiA in the morphological transition of Helicobacter pylori and in immune escape.

Chaput C, Ecobichon C, Cayet N, Girardin SE, Werts C, Guadagnini S, Prévost MC, Mengin-Lecreulx D, Labigne A, Boneca IG - PLoS Pathog. (2006)

Muropeptide Profile of H. pylori PGPG from parental strain 26695 (A) and its amiA isogenic mutant (B) were purified and digested with the muramidase M1 (mutanolysin). The generated muropeptides were separated by HPLC. The HPLC profiles show muropeptide composition after 8 h, 24 h, and 48 h of bacterial growth. Each peak structure was assigned by MALDI-TOF mass spectrometry and corresponds to a different muropeptide: (1) GM-tripeptide, (2) GM-tetrapeptide, (3) GM-tetrapeptide-glycine, (4) GM-dipeptide, and (5) GM-pentapeptide. Dimers were then eluted: (6) GM-tetrapeptide-tripeptide-MG, (7) GM-tetrapeptide-tetrapeptide-glycine-MG, (8) GM-tetrapeptide-tetrapeptide-MG, and (9) GM-tetrapeptide-pentapeptide-MG. Finally, anhydromuropeptides were eluted: (10) G(anh)M-pentapeptide, (11) and (12) G(anh)M-tetrapeptide-tripeptide-MG, (13) and (14) G(anh)M-tetrapeptide-tetrapeptide-MG, and (15) G(anh)M-tetrapeptide-pentapeptide-MG.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1574363&req=5

ppat-0020097-g001: Muropeptide Profile of H. pylori PGPG from parental strain 26695 (A) and its amiA isogenic mutant (B) were purified and digested with the muramidase M1 (mutanolysin). The generated muropeptides were separated by HPLC. The HPLC profiles show muropeptide composition after 8 h, 24 h, and 48 h of bacterial growth. Each peak structure was assigned by MALDI-TOF mass spectrometry and corresponds to a different muropeptide: (1) GM-tripeptide, (2) GM-tetrapeptide, (3) GM-tetrapeptide-glycine, (4) GM-dipeptide, and (5) GM-pentapeptide. Dimers were then eluted: (6) GM-tetrapeptide-tripeptide-MG, (7) GM-tetrapeptide-tetrapeptide-glycine-MG, (8) GM-tetrapeptide-tetrapeptide-MG, and (9) GM-tetrapeptide-pentapeptide-MG. Finally, anhydromuropeptides were eluted: (10) G(anh)M-pentapeptide, (11) and (12) G(anh)M-tetrapeptide-tripeptide-MG, (13) and (14) G(anh)M-tetrapeptide-tetrapeptide-MG, and (15) G(anh)M-tetrapeptide-pentapeptide-MG.
Mentions: We purified and analyzed the PG from the sequenced strain 26695 and from the strain NCTC11637 used as a control. No major difference between chromatograms of the two strains was observed (Figures 1 and S1). Muropeptide composition analysis of H. pylori PG showed an accumulation of the GM-dipeptide motif in strain 26695 during the stationary phase, as previously observed in strain NCTC11637 (Figures 1 and S1; [27]). Interestingly, the accumulation of the GM-dipeptide (peak 4 in Figures 1 and S1) coincided with a decrease of N-acetyl-D-glucosaminyl-β(1,4)-N-acetylmuramyl-L-Ala–γ-D-Glu-mesoDAP (GM-tripeptide) (peak 1).

Bottom Line: Both in vitro and in the human stomach it can be found in two forms, the bacillary and coccoid forms.PG modification and transformation of H. pylori was accompanied by an escape from detection by human Nod1 and the absence of NF-kappaB activation in epithelial cells.Accordingly, coccoids were unable to induce IL-8 secretion by AGS gastric epithelial cells. amiA is, to our knowledge, the first genetic determinant discovered to be required for this morphological transition into the coccoid forms, and therefore contributes to modulation of the host response and participates in the chronicity of H. pylori infection.

View Article: PubMed Central - PubMed

Affiliation: Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, Paris, France.

ABSTRACT
The human gastric pathogen Helicobacter pylori is responsible for peptic ulcers and neoplasia. Both in vitro and in the human stomach it can be found in two forms, the bacillary and coccoid forms. The molecular mechanisms of the morphological transition between these two forms and the role of coccoids remain largely unknown. The peptidoglycan (PG) layer is a major determinant of bacterial cell shape, and therefore we studied H. pylori PG structure during the morphological transition. The transition correlated with an accumulation of the N-acetyl-D-glucosaminyl-beta(1,4)-N-acetylmuramyl-L-Ala-D-Glu (GM-dipeptide) motif. We investigated the molecular mechanisms responsible for the GM-dipeptide motif accumulation, and studied the role of various putative PG hydrolases in this process. Interestingly, a mutant strain with a mutation in the amiA gene, encoding a putative PG hydrolase, was impaired in accumulating the GM-dipeptide motif and transforming into coccoids. We investigated the role of the morphological transition and the PG modification in the biology of H. pylori. PG modification and transformation of H. pylori was accompanied by an escape from detection by human Nod1 and the absence of NF-kappaB activation in epithelial cells. Accordingly, coccoids were unable to induce IL-8 secretion by AGS gastric epithelial cells. amiA is, to our knowledge, the first genetic determinant discovered to be required for this morphological transition into the coccoid forms, and therefore contributes to modulation of the host response and participates in the chronicity of H. pylori infection.

Show MeSH
Related in: MedlinePlus