S. Kuchler et al., MANNOSE DEPENDENT TIGHTENING OF THE RAT EPENDYMAL CELL BARRIER - IN-VIVO AND IN-VITRO STUDY USING NEOGLYCOPROTEINS, Neurochemistry international, 24(1), 1994, pp. 43-55
The possible role of carbohydrate binding proteins (lectins) and glyco
conjugates in the formation of junctions ensuring tightening between e
pendymal cells was studied using synthetic glycoconjugates, the neogly
coproteins. These compounds are prepared by substituting bovine serum
albumin with sugar residues and additional labelling (or not) with flu
orescein or biotin. Injections of these components into the cerebral v
entricles of adult rats resulted in a binding pattern which could be r
elated to their carbohydrate composition. Mannose-containing neoglycop
roteins were bound to ependymal cell cilia and penetrated rapidly the
brain tissue. Such phenomenon was not seen with glucose- or galactose-
containing neoglycoprotein molecules. In contrast, mannose-, galactose
- and glucose- containing neoglycoproteins bound strongly to some endo
thelial cells around blood vessels. Fluorescent unglycosylated serum a
lbumin did not bind to any brain structures. In contrast, co-injection
of mannose-containing non-fluorescent neoglycoproteins with the other
fluorescent compounds (including fluorescent sugar-free BSA) resulted
in the penetration of the fluorescent compounds into the brain tissue
. This internalization into brain was attributed to disaggregation of
junctions between ependymal cells. Cultured ependymal cells behaved li
kewise. In short term experiments (5 min-1 h), only the mannose-contai
ning neoglycoproteins bound strongly to the ependymal cells, particula
rly to the cilia. In long term experiments (1-9 days), mannose-contain
ing neoglycoproteins specifically induced the disappearance of junctio
ns between the cultured cells. These results emphasize the importance
of mannose-dependent recognition system in the maintenance of junction
s between ependymal cells, where a mannose-binding lectin has been pre
viously detected.