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AGR2, an endoplasmic reticulum protein, is secreted into the gastrointestinal mucus.

Bergström JH, Berg KA, Rodríguez-Piñeiro AM, Stecher B, Johansson ME, Hansson GC - PLoS ONE (2014)

Bottom Line: We found relatively high concentrations of Agr2 in secreted mucus throughout the murine gastrointestinal tract, suggesting that Agr2 may play extracellular roles.Replacement of the single Cys in AGR2 with Ser (C81S) allowed secretion, suggesting that modification of this Cys might provide a mechanism for circumventing the KTEL endoplasmic reticulum retention signal.In conclusion, these results suggest that AGR2 has both intracellular and extracellular effects in the intestine.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden.

ABSTRACT
The MUC2 mucin is the major constituent of the two mucus layers in colon. Mice lacking the disulfide isomerase-like protein Agr2 have been shown to be more susceptible to colon inflammation. The Agr2(-/-) mice have less filled goblet cells and were now shown to have a poorly developed inner colon mucus layer. We could not show AGR2 covalently bound to recombinant MUC2 N- and C-termini as have previously been suggested. We found relatively high concentrations of Agr2 in secreted mucus throughout the murine gastrointestinal tract, suggesting that Agr2 may play extracellular roles. In tissue culture (CHO-K1) cells, AGR2 is normally not secreted. Replacement of the single Cys in AGR2 with Ser (C81S) allowed secretion, suggesting that modification of this Cys might provide a mechanism for circumventing the KTEL endoplasmic reticulum retention signal. In conclusion, these results suggest that AGR2 has both intracellular and extracellular effects in the intestine.

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Agr2 is a component of the protective mucus layer in the whole gastrointestinal tract.(A) Boxplot of the relative levels (logarithm of the normalized intensities) of Agr2 in the mucus along the mouse gastrointestinal tract as revealed by proteomics. Sto: stomach; Duo: duodenum; Jej: jejunum; Ile: Ileum; PC: proximal colon; DC: distal colon. (B) Immunoblot detecting AGR2 in mucus from human colonic biopsies mounted in a horizontal perfusion hamber. The first lane (mucus) contains the collected secreted mucus. The second lane (lysate) shows the AGR2 remaining in the biopsy after mucus collection (diluted 1∶100). (C) Molar ratios between Agr2, Muc2, Fcgbp and Clca1 in proximal and distal colonic murine mucus.
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pone-0104186-g005: Agr2 is a component of the protective mucus layer in the whole gastrointestinal tract.(A) Boxplot of the relative levels (logarithm of the normalized intensities) of Agr2 in the mucus along the mouse gastrointestinal tract as revealed by proteomics. Sto: stomach; Duo: duodenum; Jej: jejunum; Ile: Ileum; PC: proximal colon; DC: distal colon. (B) Immunoblot detecting AGR2 in mucus from human colonic biopsies mounted in a horizontal perfusion hamber. The first lane (mucus) contains the collected secreted mucus. The second lane (lysate) shows the AGR2 remaining in the biopsy after mucus collection (diluted 1∶100). (C) Molar ratios between Agr2, Muc2, Fcgbp and Clca1 in proximal and distal colonic murine mucus.

Mentions: In studies of the mouse colonic mucus by proteomics Agr2 was observed to be a relatively abundant protein [2], [22]. We have now expanded our mucus proteomic studies to the whole gastro-intestinal tract and observed that Agr2 was present in the mucus of all parts of the digestive tract reaching the highest concentrations in the proximal colon (Fig. 5A). To further confirm the extracellular localization of also the human AGR2, colonic mucus from human biopsies was carefully collected after mounting it in a horizontal Ussing-type chamber, and both the collected mucus and the remaining intestinal tissue were analyzed by PAGE and Western blot. An AGR2 band at about 18 kDa was found in the collected mucus as well as in the colon tissue (Fig. 5B). It can thus be concluded that both the human AGR2 and the murine Agr2 are not only resident ER proteins, but they are also present in significant amounts in the secreted gastrointestinal mucus.


AGR2, an endoplasmic reticulum protein, is secreted into the gastrointestinal mucus.

Bergström JH, Berg KA, Rodríguez-Piñeiro AM, Stecher B, Johansson ME, Hansson GC - PLoS ONE (2014)

Agr2 is a component of the protective mucus layer in the whole gastrointestinal tract.(A) Boxplot of the relative levels (logarithm of the normalized intensities) of Agr2 in the mucus along the mouse gastrointestinal tract as revealed by proteomics. Sto: stomach; Duo: duodenum; Jej: jejunum; Ile: Ileum; PC: proximal colon; DC: distal colon. (B) Immunoblot detecting AGR2 in mucus from human colonic biopsies mounted in a horizontal perfusion hamber. The first lane (mucus) contains the collected secreted mucus. The second lane (lysate) shows the AGR2 remaining in the biopsy after mucus collection (diluted 1∶100). (C) Molar ratios between Agr2, Muc2, Fcgbp and Clca1 in proximal and distal colonic murine mucus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4128659&req=5

pone-0104186-g005: Agr2 is a component of the protective mucus layer in the whole gastrointestinal tract.(A) Boxplot of the relative levels (logarithm of the normalized intensities) of Agr2 in the mucus along the mouse gastrointestinal tract as revealed by proteomics. Sto: stomach; Duo: duodenum; Jej: jejunum; Ile: Ileum; PC: proximal colon; DC: distal colon. (B) Immunoblot detecting AGR2 in mucus from human colonic biopsies mounted in a horizontal perfusion hamber. The first lane (mucus) contains the collected secreted mucus. The second lane (lysate) shows the AGR2 remaining in the biopsy after mucus collection (diluted 1∶100). (C) Molar ratios between Agr2, Muc2, Fcgbp and Clca1 in proximal and distal colonic murine mucus.
Mentions: In studies of the mouse colonic mucus by proteomics Agr2 was observed to be a relatively abundant protein [2], [22]. We have now expanded our mucus proteomic studies to the whole gastro-intestinal tract and observed that Agr2 was present in the mucus of all parts of the digestive tract reaching the highest concentrations in the proximal colon (Fig. 5A). To further confirm the extracellular localization of also the human AGR2, colonic mucus from human biopsies was carefully collected after mounting it in a horizontal Ussing-type chamber, and both the collected mucus and the remaining intestinal tissue were analyzed by PAGE and Western blot. An AGR2 band at about 18 kDa was found in the collected mucus as well as in the colon tissue (Fig. 5B). It can thus be concluded that both the human AGR2 and the murine Agr2 are not only resident ER proteins, but they are also present in significant amounts in the secreted gastrointestinal mucus.

Bottom Line: We found relatively high concentrations of Agr2 in secreted mucus throughout the murine gastrointestinal tract, suggesting that Agr2 may play extracellular roles.Replacement of the single Cys in AGR2 with Ser (C81S) allowed secretion, suggesting that modification of this Cys might provide a mechanism for circumventing the KTEL endoplasmic reticulum retention signal.In conclusion, these results suggest that AGR2 has both intracellular and extracellular effects in the intestine.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden.

ABSTRACT
The MUC2 mucin is the major constituent of the two mucus layers in colon. Mice lacking the disulfide isomerase-like protein Agr2 have been shown to be more susceptible to colon inflammation. The Agr2(-/-) mice have less filled goblet cells and were now shown to have a poorly developed inner colon mucus layer. We could not show AGR2 covalently bound to recombinant MUC2 N- and C-termini as have previously been suggested. We found relatively high concentrations of Agr2 in secreted mucus throughout the murine gastrointestinal tract, suggesting that Agr2 may play extracellular roles. In tissue culture (CHO-K1) cells, AGR2 is normally not secreted. Replacement of the single Cys in AGR2 with Ser (C81S) allowed secretion, suggesting that modification of this Cys might provide a mechanism for circumventing the KTEL endoplasmic reticulum retention signal. In conclusion, these results suggest that AGR2 has both intracellular and extracellular effects in the intestine.

Show MeSH
Related in: MedlinePlus