Limits...
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.

Show MeSH

Related in: MedlinePlus

Cell segregation directed by Ep-CAM. L cells  were transfected with cDNA  for E-cadherin (LEC) or Ep-CAM (LEp), and the E-cadherin transfectants were additionally supertransfected  with either Ep-CAM cDNA  (LEC-Ep) or the blank vector (LEC-C). (A) Pairs of  transfected cells were tested in coaggregation assays: dispersed  cells of two types (Type1 + Type2), each labeled with a different  fluorescent dye, were mixed at equal concentrations. After 2 h of  culturing in suspension, cell aggregates consisting of >10 cells  were analyzed for the presence of cells of each type. The data is  presented as percentage of aggregates (y-axis) containing the respective percentage of the Type 2 cells (x-axis). (B) Expression  of E-cadherin and Ep-CAM in the transfectants, as determined  by immunoblotting in total cell lysates using antibodies to E-cadherin (36) and to human Ep-CAM (323/A3), respectively.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2140211&req=5

Figure 2: Cell segregation directed by Ep-CAM. L cells were transfected with cDNA for E-cadherin (LEC) or Ep-CAM (LEp), and the E-cadherin transfectants were additionally supertransfected with either Ep-CAM cDNA (LEC-Ep) or the blank vector (LEC-C). (A) Pairs of transfected cells were tested in coaggregation assays: dispersed cells of two types (Type1 + Type2), each labeled with a different fluorescent dye, were mixed at equal concentrations. After 2 h of culturing in suspension, cell aggregates consisting of >10 cells were analyzed for the presence of cells of each type. The data is presented as percentage of aggregates (y-axis) containing the respective percentage of the Type 2 cells (x-axis). (B) Expression of E-cadherin and Ep-CAM in the transfectants, as determined by immunoblotting in total cell lysates using antibodies to E-cadherin (36) and to human Ep-CAM (323/A3), respectively.

Mentions: When mixed in suspension, neither LEC nor LEp cells interacted with the parental L cells. The LEC and LEp cells also did not interact with one another, as was tested in coaggregation assays performed to exclude possible heterotypic interactions between Ep-CAM and E-cadherin (Fig. 2). LEC-C and LEC-Ep cells, when mixed, showed segregation in suspension coaggregation assays (Fig. 2). Although some aggregates contained cells of both types, and the segregation could be described as partial only, the two cell types did show a clear preference for independent aggregation.


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)

Cell segregation directed by Ep-CAM. L cells  were transfected with cDNA  for E-cadherin (LEC) or Ep-CAM (LEp), and the E-cadherin transfectants were additionally supertransfected  with either Ep-CAM cDNA  (LEC-Ep) or the blank vector (LEC-C). (A) Pairs of  transfected cells were tested in coaggregation assays: dispersed  cells of two types (Type1 + Type2), each labeled with a different  fluorescent dye, were mixed at equal concentrations. After 2 h of  culturing in suspension, cell aggregates consisting of >10 cells  were analyzed for the presence of cells of each type. The data is  presented as percentage of aggregates (y-axis) containing the respective percentage of the Type 2 cells (x-axis). (B) Expression  of E-cadherin and Ep-CAM in the transfectants, as determined  by immunoblotting in total cell lysates using antibodies to E-cadherin (36) and to human Ep-CAM (323/A3), respectively.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Cell segregation directed by Ep-CAM. L cells were transfected with cDNA for E-cadherin (LEC) or Ep-CAM (LEp), and the E-cadherin transfectants were additionally supertransfected with either Ep-CAM cDNA (LEC-Ep) or the blank vector (LEC-C). (A) Pairs of transfected cells were tested in coaggregation assays: dispersed cells of two types (Type1 + Type2), each labeled with a different fluorescent dye, were mixed at equal concentrations. After 2 h of culturing in suspension, cell aggregates consisting of >10 cells were analyzed for the presence of cells of each type. The data is presented as percentage of aggregates (y-axis) containing the respective percentage of the Type 2 cells (x-axis). (B) Expression of E-cadherin and Ep-CAM in the transfectants, as determined by immunoblotting in total cell lysates using antibodies to E-cadherin (36) and to human Ep-CAM (323/A3), respectively.
Mentions: When mixed in suspension, neither LEC nor LEp cells interacted with the parental L cells. The LEC and LEp cells also did not interact with one another, as was tested in coaggregation assays performed to exclude possible heterotypic interactions between Ep-CAM and E-cadherin (Fig. 2). LEC-C and LEC-Ep cells, when mixed, showed segregation in suspension coaggregation assays (Fig. 2). Although some aggregates contained cells of both types, and the segregation could be described as partial only, the two cell types did show a clear preference for independent aggregation.

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