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The intestinal T cell response to alpha-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase.

Arentz-Hansen H, Körner R, Molberg O, Quarsten H, Vader W, Kooy YM, Lundin KE, Koning F, Roepstorff P, Sollid LM, McAdam SN - J. Exp. Med. (2000)

Bottom Line: These two class II molecules are chiefly responsible for the presentation of gluten peptides to the gluten-specific T cells that are found only in the gut of CD patients but not of controls.Interestingly, the modified glutamine is accommodated in different pockets of DQ2 for the different epitopes.These results suggest modifications of anchor residues that lead to an improved affinity for major histocompatibility complex (MHC), and altered conformation of the peptide-MHC complex may be a critical factor leading to T cell responses to gliadin and the oral intolerance of gluten found in CD.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Rikshospitalet, University of Oslo, N-0027 Oslo, Norway.

ABSTRACT
The great majority of patients that are intolerant of wheat gluten protein due to celiac disease (CD) are human histocompatibility leukocyte antigen (HLA)-DQ2(+), and the remaining few normally express HLA-DQ8. These two class II molecules are chiefly responsible for the presentation of gluten peptides to the gluten-specific T cells that are found only in the gut of CD patients but not of controls. Interestingly, tissue transglutaminase (tTG)-mediated deamidation of gliadin plays an important role in recognition of this food antigen by intestinal T cells. Here we have used recombinant antigens to demonstrate that the intestinal T cell response to alpha-gliadin in adult CD is focused on two immunodominant, DQ2-restricted peptides that overlap by a seven-residue fragment of gliadin. We show that tTG converts a glutamine residue within this fragment into glutamic acid and that this process is critical for T cell recognition. Gluten-specific T cell lines from 16 different adult patients all responded to one or both of these deamidated peptides, indicating that these epitopes are highly relevant to disease pathology. Binding studies showed that the deamidated peptides displayed an increased affinity for DQ2, a molecule known to preferentially bind peptides containing negatively charged residues. Interestingly, the modified glutamine is accommodated in different pockets of DQ2 for the different epitopes. These results suggest modifications of anchor residues that lead to an improved affinity for major histocompatibility complex (MHC), and altered conformation of the peptide-MHC complex may be a critical factor leading to T cell responses to gliadin and the oral intolerance of gluten found in CD.

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Related in: MedlinePlus

Testing of synthetic glutamine to glutamic acid–substituted peptides for their ability to stimulate TCCs. TCC CD387 E34 (A) and TCC CD412 R5.32 (B) were tested for recognition of a set of singly substituted peptides that had the glutamine residues substituted for glutamic acid residues.
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Figure 3: Testing of synthetic glutamine to glutamic acid–substituted peptides for their ability to stimulate TCCs. TCC CD387 E34 (A) and TCC CD412 R5.32 (B) were tested for recognition of a set of singly substituted peptides that had the glutamine residues substituted for glutamic acid residues.

Mentions: The α-2(62–75) and α-9(57–68) peptides were only recognized by the TCC after deamidation with tTG or in conditions known to promote nonenzymatic deamidation (i.e., heating in an acidic environment). To identify the number and position of glutamine residues targeted by tTG, we separated the α-2(62–75) and α-9(57–68) peptides by Mono-Q chromatography after first treating them with recombinant human tTG. Analysis of the α-9(57–68) peptide indicated that a single new peptide peak had been created by treatment with tTG. Mono-Q fractions containing this peak efficiently stimulated TCC CD387 E34 (Fig. 1 C). This fraction was methyl-esterified to label the deamidation site with a methyl-ester group, and this position was identified as residue 65 by MS/MS analysis (peptide α-9[57–68]E65; reference 25). Two peaks were created by the tTG treatment of the α-2(62–75) peptide, both of which were stimulatory for the TCC CD412 R5.32 (data not shown). Mass spectrometry analysis revealed that the least acidic of these two peaks contained a peptide in which the glutamine at position 65 had been deamidated (peptide α-2[62–75]E65). The more acidic peak contained a peptide with glutamines deamidated at residues 65 and 72. Confirmation that the deamidation of glutamine at position 65 was critical for T cell recognition of both peptides was given by testing synthetic peptides with glutamines substituted with glutamic acid. Peptides containing glutamic acid at position 65 stimulated TCCs CD412 R5.32 and CD387 E34 extremely efficiently; the remaining peptides could, at best, only stimulate the TCCs very weakly when high concentrations of peptide were used (Fig. 3). Testing for recognition of both the α-9(57–68)E65 and α-2(62–75)E65 peptides demonstrated that these epitopes were not cross-reactive for this panel of TCCs (data not shown).


The intestinal T cell response to alpha-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase.

Arentz-Hansen H, Körner R, Molberg O, Quarsten H, Vader W, Kooy YM, Lundin KE, Koning F, Roepstorff P, Sollid LM, McAdam SN - J. Exp. Med. (2000)

Testing of synthetic glutamine to glutamic acid–substituted peptides for their ability to stimulate TCCs. TCC CD387 E34 (A) and TCC CD412 R5.32 (B) were tested for recognition of a set of singly substituted peptides that had the glutamine residues substituted for glutamic acid residues.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2195837&req=5

Figure 3: Testing of synthetic glutamine to glutamic acid–substituted peptides for their ability to stimulate TCCs. TCC CD387 E34 (A) and TCC CD412 R5.32 (B) were tested for recognition of a set of singly substituted peptides that had the glutamine residues substituted for glutamic acid residues.
Mentions: The α-2(62–75) and α-9(57–68) peptides were only recognized by the TCC after deamidation with tTG or in conditions known to promote nonenzymatic deamidation (i.e., heating in an acidic environment). To identify the number and position of glutamine residues targeted by tTG, we separated the α-2(62–75) and α-9(57–68) peptides by Mono-Q chromatography after first treating them with recombinant human tTG. Analysis of the α-9(57–68) peptide indicated that a single new peptide peak had been created by treatment with tTG. Mono-Q fractions containing this peak efficiently stimulated TCC CD387 E34 (Fig. 1 C). This fraction was methyl-esterified to label the deamidation site with a methyl-ester group, and this position was identified as residue 65 by MS/MS analysis (peptide α-9[57–68]E65; reference 25). Two peaks were created by the tTG treatment of the α-2(62–75) peptide, both of which were stimulatory for the TCC CD412 R5.32 (data not shown). Mass spectrometry analysis revealed that the least acidic of these two peaks contained a peptide in which the glutamine at position 65 had been deamidated (peptide α-2[62–75]E65). The more acidic peak contained a peptide with glutamines deamidated at residues 65 and 72. Confirmation that the deamidation of glutamine at position 65 was critical for T cell recognition of both peptides was given by testing synthetic peptides with glutamines substituted with glutamic acid. Peptides containing glutamic acid at position 65 stimulated TCCs CD412 R5.32 and CD387 E34 extremely efficiently; the remaining peptides could, at best, only stimulate the TCCs very weakly when high concentrations of peptide were used (Fig. 3). Testing for recognition of both the α-9(57–68)E65 and α-2(62–75)E65 peptides demonstrated that these epitopes were not cross-reactive for this panel of TCCs (data not shown).

Bottom Line: These two class II molecules are chiefly responsible for the presentation of gluten peptides to the gluten-specific T cells that are found only in the gut of CD patients but not of controls.Interestingly, the modified glutamine is accommodated in different pockets of DQ2 for the different epitopes.These results suggest modifications of anchor residues that lead to an improved affinity for major histocompatibility complex (MHC), and altered conformation of the peptide-MHC complex may be a critical factor leading to T cell responses to gliadin and the oral intolerance of gluten found in CD.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Rikshospitalet, University of Oslo, N-0027 Oslo, Norway.

ABSTRACT
The great majority of patients that are intolerant of wheat gluten protein due to celiac disease (CD) are human histocompatibility leukocyte antigen (HLA)-DQ2(+), and the remaining few normally express HLA-DQ8. These two class II molecules are chiefly responsible for the presentation of gluten peptides to the gluten-specific T cells that are found only in the gut of CD patients but not of controls. Interestingly, tissue transglutaminase (tTG)-mediated deamidation of gliadin plays an important role in recognition of this food antigen by intestinal T cells. Here we have used recombinant antigens to demonstrate that the intestinal T cell response to alpha-gliadin in adult CD is focused on two immunodominant, DQ2-restricted peptides that overlap by a seven-residue fragment of gliadin. We show that tTG converts a glutamine residue within this fragment into glutamic acid and that this process is critical for T cell recognition. Gluten-specific T cell lines from 16 different adult patients all responded to one or both of these deamidated peptides, indicating that these epitopes are highly relevant to disease pathology. Binding studies showed that the deamidated peptides displayed an increased affinity for DQ2, a molecule known to preferentially bind peptides containing negatively charged residues. Interestingly, the modified glutamine is accommodated in different pockets of DQ2 for the different epitopes. These results suggest modifications of anchor residues that lead to an improved affinity for major histocompatibility complex (MHC), and altered conformation of the peptide-MHC complex may be a critical factor leading to T cell responses to gliadin and the oral intolerance of gluten found in CD.

Show MeSH
Related in: MedlinePlus