L. Monlauzeur et al., PUTATIVE O-GLYCOSYLATION SITES AND A MEMBRANE ANCHOR ARE NECESSARY FOR APICAL DELIVERY OF THE HUMAN NEUROTROPHIN RECEPTOR IN CACO-2 CELLS, The Journal of biological chemistry, 273(46), 1998, pp. 30263-30270
We have expressed the human neurotrophin receptor p75 (p75(NTR)) in th
e intestinal epithelial cell line Caco-2 as a model to study intracell
ular transport and subcellular sorting signals in intestinal cells. p7
5(NTR) was localized at the apical membrane of Caco-2 cells and reache
d this membrane mainly via an indirect pathway. Apical localization, i
ntracellular routing, and basolateral to apical transcytosis were not
affected by truncation of the cytoplasmic domain or replacement of the
transmembrane domain by a glycosyl phosphatidylinositol anchor. Remov
al of membrane anchoring resulted in basolateral secretion of the ecto
domain of p75(NTR) in Caco-2 cells but in apical secretion in Madin-Da
rby canine kidney (MDCK) cells. Substitution of potential O-glycosylat
ion sites present in the stalk of p75NTR led to intracellular cleavage
and secretion of the ectodomain into the basolateral medium both in C
aco-2 and MDCK cells. These results suggest that the stalk of p75NTR c
arries an apical sorting information that is recognized efficiently by
Caco-2 cells only when attached to the membrane. This apical sorting
information is linked to the presence of predicted O-glycosylation sit
es in that region. These putative O-glycosylation sites also play a ro
le in the regulation of p75NTR transport to the cell surface and in th
e prevention of rapid degradation by cleavage of the stalk domain.