The filamentous brush border glycocalyx, a mucin-like marker of enterocyte hyper-polarization.
The probably sole constituent of the filamentous brush border glycocalyx, which has been defined on the basis of electron microscopic data as a set of filaments radiating from the tip of rabbit intestinal brush border microvilli, has been purified. It consists of a mucin-type glycoprotein that can be solubilized by either Triton extraction or papain treatment of the brush border membrane vesicles but is insensitive to phosphatidylinositol phospholipase C. The detergent- and papain-solubilized forms both have the same apparent molecular mass of 400 kDa (SDS/PAGE). This suggests that the filamentous brush border glycocalyx may be anchored to the membrane by a small hydrophobic peptidic tail. Ser, Thr, Pro and Ala amount to 65% of the protein core amino acid residues. The glycosidic moiety, which amounts to 73% of the molecular mass, has high O-acetylated sialic acid contents. A monoclonal antibody (3A4) raised against the purified material was produced which specifically recognized the 400-kDa band by immunoprecipitation and immunoblotting, and the filamentous brush border glycocalyx of villus enterocytes when jejunum sections were immunolabelled. The 3A4 determinant was identified with a filamentous brush border glycocalyx-specific carbohydrate structure containing an O-acetylated sialic acid. The fact that the labeled glycocalyx was anchored entirely in a membrane microdomain at the tip of the microvilli shows that mature enterocytes are hyper-polarized epithelial cells.
Maury
J
J
Laboratoire de Biochimie et Biologie de la Nutrition, CNRS-URA 1820, Faculté des Sciences de Saint Jérôme, Marseille, France.
Nicoletti
C
C
Guzzo-Chambraud
L
L
Maroux
S
S
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000939:Epitopes; D006001:Glycoconjugates / Q000302:isolation & purification; D006023:Glycoproteins / Q000032:analysis / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D009077:Mucins / Q000032:analysis; D011134:Polysaccharides / Q000032:analysis / Q000276:immunology / Q000302:isolation & purification*; D011817:Rabbits
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D000939:Epitopes; D006001:Glycoconjugates; D006023:Glycoproteins; D009077:Mucins; D011134:Polysaccharides