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Epithelial cell adhesion molecule (Ep-CAM) modulates cell-cell interactions mediated by classic cadherins.

Litvinov SV, Balzar M, Winter MJ, Bakker HA, Briaire-de Bruijn IH, Prins F, Fleuren GJ, Warnaar SO - J. Cell Biol. (1997)

Bottom Line: Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM.While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases.The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Leiden University, Leiden 2300 RC, The Netherlands. slitvinov@pathology.medfac.leidenuniv.nl

ABSTRACT
The contribution of noncadherin-type, Ca2+-independent cell-cell adhesion molecules to the organization of epithelial tissues is, as yet, unclear. A homophilic, epithelial Ca2+-independent adhesion molecule (Ep-CAM) is expressed in most epithelia, benign or malignant proliferative lesions, or during embryogenesis. Here we demonstrate that ectopic Ep-CAM, when expressed in cells interconnected by classic cadherins (E- or N-cadherin), induces segregation of the transfectants from the parental cell type in coaggregation assays and in cultured mixed aggregates, respectively. In the latter assay, Ep-CAM-positive transfectants behave like cells with a decreased strength of cell-cell adhesion as compared to the parental cells. Using transfectants with an inducible Ep-CAM-cDNA construct, we demonstrate that increasing expression of Ep-CAM in cadherin-positive cells leads to the gradual abrogation of adherens junctions. Overexpression of Ep-CAM has no influence on the total amount of cellular cadherin, but affects the interaction of cadherins with the cytoskeleton since a substantial decrease in the detergent-insoluble fraction of cadherin molecules was observed. Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM. While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases. As the cadherin-mediated cell-cell adhesions diminish, Ep-CAM-mediated intercellular connections become predominant. An adhesion-defective mutant of Ep-CAM lacking the cytoplasmic domain has no effect on the cadherin-mediated cell-cell adhesions. The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

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Detergent extractability of  catenins in HCA cells and Wt Ep-CAM transfectants. Immunoblotting  was performed on total cell lysates and  on lysates of cells preextracted with  0.5% Triton X-100. The + indicates induction of cells with 50 μM CdCl2 for  24 h before lysis.
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Figure 12: Detergent extractability of catenins in HCA cells and Wt Ep-CAM transfectants. Immunoblotting was performed on total cell lysates and on lysates of cells preextracted with 0.5% Triton X-100. The + indicates induction of cells with 50 μM CdCl2 for 24 h before lysis.

Mentions: Induction of Ep-CAM in cells did not affect either the total level of cell cadherins (as was detected with immunoblotting with pancadherin antibody, (see Fig. 13), or the surface expression of N-cadherin (as was detected with flow cytometry, not shown). The surface expression of E- and P-cadherins in HCA cells was too low to be measured by flow cytometry. However, upon induction of Ep-CAM, the subcellular distribution of cadherins was changed: the typical junctional structures, including cadherins that were present in HCA cells (or control transfectants), were absent in induced (Fig. 11) but not in noninduced Ep-CAM transfectants. The disturbance of cadherin's subcellular localization suggested that the effect of Ep-CAM was similar to that observed for LEC cells. Indeed, the detergent solubility of the cadherins in HCA cells was increased after 24 h of Ep-CAM (see Fig. 13). Induction of Ep-CAM had no effect on total level of cellular β-catenin, but it negatively affected the level of total α-catenin (Fig. 12); the detergent-insoluble fraction for both molecules was reduced in relation to the expression of Ep-CAM (Fig. 12). All observations are based on 24-h induction of Ep-CAM.


Epithelial cell adhesion molecule (Ep-CAM) modulates cell-cell interactions mediated by classic cadherins.

Litvinov SV, Balzar M, Winter MJ, Bakker HA, Briaire-de Bruijn IH, Prins F, Fleuren GJ, Warnaar SO - J. Cell Biol. (1997)

Detergent extractability of  catenins in HCA cells and Wt Ep-CAM transfectants. Immunoblotting  was performed on total cell lysates and  on lysates of cells preextracted with  0.5% Triton X-100. The + indicates induction of cells with 50 μM CdCl2 for  24 h before lysis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2140211&req=5

Figure 12: Detergent extractability of catenins in HCA cells and Wt Ep-CAM transfectants. Immunoblotting was performed on total cell lysates and on lysates of cells preextracted with 0.5% Triton X-100. The + indicates induction of cells with 50 μM CdCl2 for 24 h before lysis.
Mentions: Induction of Ep-CAM in cells did not affect either the total level of cell cadherins (as was detected with immunoblotting with pancadherin antibody, (see Fig. 13), or the surface expression of N-cadherin (as was detected with flow cytometry, not shown). The surface expression of E- and P-cadherins in HCA cells was too low to be measured by flow cytometry. However, upon induction of Ep-CAM, the subcellular distribution of cadherins was changed: the typical junctional structures, including cadherins that were present in HCA cells (or control transfectants), were absent in induced (Fig. 11) but not in noninduced Ep-CAM transfectants. The disturbance of cadherin's subcellular localization suggested that the effect of Ep-CAM was similar to that observed for LEC cells. Indeed, the detergent solubility of the cadherins in HCA cells was increased after 24 h of Ep-CAM (see Fig. 13). Induction of Ep-CAM had no effect on total level of cellular β-catenin, but it negatively affected the level of total α-catenin (Fig. 12); the detergent-insoluble fraction for both molecules was reduced in relation to the expression of Ep-CAM (Fig. 12). All observations are based on 24-h induction of Ep-CAM.

Bottom Line: Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM.While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases.The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Leiden University, Leiden 2300 RC, The Netherlands. slitvinov@pathology.medfac.leidenuniv.nl

ABSTRACT
The contribution of noncadherin-type, Ca2+-independent cell-cell adhesion molecules to the organization of epithelial tissues is, as yet, unclear. A homophilic, epithelial Ca2+-independent adhesion molecule (Ep-CAM) is expressed in most epithelia, benign or malignant proliferative lesions, or during embryogenesis. Here we demonstrate that ectopic Ep-CAM, when expressed in cells interconnected by classic cadherins (E- or N-cadherin), induces segregation of the transfectants from the parental cell type in coaggregation assays and in cultured mixed aggregates, respectively. In the latter assay, Ep-CAM-positive transfectants behave like cells with a decreased strength of cell-cell adhesion as compared to the parental cells. Using transfectants with an inducible Ep-CAM-cDNA construct, we demonstrate that increasing expression of Ep-CAM in cadherin-positive cells leads to the gradual abrogation of adherens junctions. Overexpression of Ep-CAM has no influence on the total amount of cellular cadherin, but affects the interaction of cadherins with the cytoskeleton since a substantial decrease in the detergent-insoluble fraction of cadherin molecules was observed. Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM. While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases. As the cadherin-mediated cell-cell adhesions diminish, Ep-CAM-mediated intercellular connections become predominant. An adhesion-defective mutant of Ep-CAM lacking the cytoplasmic domain has no effect on the cadherin-mediated cell-cell adhesions. The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

Show MeSH
Related in: MedlinePlus