title: The inner of the two Muc2 mucin-dependent mucus layers in colon is devoid of bacteria.
abstract: We normally live in symbiosis with approximately 10(13) bacteria present in the colon. Among the several mechanisms maintaining the bacteria/host balance, there is limited understanding of the structure, function, and properties of intestinal mucus. We now demonstrate that the mouse colonic mucus consists of two layers extending 150 mum above the epithelial cells. Proteomics revealed that both of these layers have similar protein composition, with the large gel-forming mucin Muc2 as the major structural component. The inner layer is densely packed, firmly attached to the epithelium, and devoid of bacteria. In contrast, the outer layer is movable, has an expanded volume due to proteolytic cleavages of the Muc2 mucin, and is colonized by bacteria. Muc2(-/-) mice have bacteria in direct contact with the epithelial cells and far down in the crypts, explaining the inflammation and cancer development observed in these animals. These findings show that the Muc2 mucin can build a mucus barrier that separates bacteria from the colon epithelia and suggest that defects in this mucus can cause colon inflammation.
authors.affiliation: Department of Medical Biochemistry, University of Gothenburg, 405 30 Gothenburg, Sweden.
authors.forename: Malin E V
authors.initials: ME
authors.lastname: Johansson
authors.forename: Mia
authors.initials: M
authors.lastname: Phillipson
authors.forename: Joel
authors.initials: J
authors.lastname: Petersson
authors.forename: Anna
authors.initials: A
authors.lastname: Velcich
authors.forename: Lena
authors.initials: L
authors.lastname: Holm
authors.forename: Gunnar C
authors.initials: GC
authors.lastname: Hansson
mesh_terms: D000818:Animals; D003092:Colitis / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D003106:Colon / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D008817:Mice, Mutant Strains; D055262:Mucin-2; D009077:Mucins / Q000235:genetics / Q000502:physiology*; D009093:Mucus / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013559:Symbiosis / Q000235:genetics
chemical_list: C524626:Muc2 protein, mouse; C524628:Muc2 protein, rat; D055262:Mucin-2; D009077:Mucins