Expression and glycosylation of the filamentous brush border
glycocalyx (fbbg) during rabbit enterocyte differentiation along the
crypt-villus axis.
Maury, J., A. Bernadac, A. Rigal, and S. Maroux.
Laboratoire de Biochimie et Biologie de la Nutrition, CNRS-URA
1820, Facult[acute]e des Sciences de Saint J[acute]er[circumflex]ome,
Case 342, 13397 Marseille Cedex 20, France
APStracts 2:0226L, 1995.
The filamentous brush border glycocalyx forming the "enteric
surface coat" of the intestinal epithelium is composed in rabbits
of a 400 kDa mucin-type glycoprotein which was purified using the 3A4
monoclonal antibody.This monoclonal antibody recognizes a filamentous
brush border glycocalyx specific glycosidic structure containing an
O-acetylated sialic acid, that is absent from all the other
glycoproteins in the epithelium, with the exception of certain goblet
cell mucins (Maury et al., 1995, Eur. J. Biochem. 228, 323-331). Here
we established that only 50% of the rabbits tested synthesized this
glycosidic structure. Upon immunolabeling surface epithelia and
sections of jejunum from these rabbits, the carbohydrate epitope
recognized by the 3A4 mAb was found to be present on the filamentous
brush border glycocalyx of a variable number of enterocytes, which
were patchily distributed over all the villi. This heterogenous
expression of 3A4 antigenicity, which was also observed in the
crypts, suggests the existence of differences between the patterns of
differentiation of enterocytes, which result in the expression of
different pools of glycosyltransferases and/or acetyl transferases.
In mature enterocytes, the 3A4 determinants were present only on the
filamentous brush border glycocalyx, which is anchored solely to the
membrane microdomain at the tip of brush border microvilli. However,
expression of 3A4 antigenicity begins in the median third of crypts,
in enterocytes with a short, thin brush border devoid of apical
filamentous brush border glycocalyx. Here the 3A4 epitopes were
present over the whole brush border membrane. A few cells higher up,
the hyperpolarized expression of filamentous brush border glycocalyx,
i.e., its segregation at the tip of the microvilli, began and both
the apical filamentous brush border glycocalyx and the whole brush
border membrane were labeled with the 3A4 mAb. The labeling of the
lateral membrane of microvilli gradually decreased and then
disappeared during the migration of the cells to the upper part of
the crypts. The 3A4 structure was also detected in some of the
granules of some rare goblet cells in the vicinity of the most deeply
located labeled enterocytes, whereas no labeled goblet cells were
ever observed at higher cell locations.
Received 11 July 1995; accepted in final form 6 December 1995.
APS Manuscript Number L217-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95