E-cadherin-dependent transcriptional control of apolipoprotein A-IV gene expression in intestinal epithelial cells: a role for the hepatic nuclear factor 4.

Cell-matrix and cell-cell adhesion play a central role in the control of cell proliferation, differentiation, and gene expression. Integrins and E-cadherin are the key components involved in these processes in epithelial cells. We recently showed that integrin-dependent adhesion to the extracellular matrix reinforces the formation of E-cadherin-actin complexes inducing the polarization of Caco-2 enterocytes and increases the expression of a marker of enterocyte differentiation, the apolipoprotein A-IV (apoA-IV) gene. By impairing or enhancing E-cadherin-dependent cell adhesion, we demonstrate in the present study its involvement in the transcriptional activation of the apoA-IV gene in Caco-2 cells. This control requires the regulatory sequence that we have previously identified as necessary and sufficient to drive and restrict apoA-IV gene expression in enterocytes in vivo. Furthermore, using chimeric E-cadherin-Fc homophilic ligand-coated surfaces, we show that a direct activation of E-cadherin triggers the transcriptional activation of the apoA-IV promoter. Finally, E-cadherin-dependent cell-cell adhesion controls the nuclear abundance of the transcription factor hepatic nuclear factor 4alpha, which is involved in the enterocyte-specific expression of apoA-IV gene. Altogether, our results suggest that E-cadherin controls enterocyte-specific expression of genes, such as the apoA-IV gene, through the control of hepatic nuclear factor 4alpha nuclear abundance.

Integrin-mediated functional polarization of Caco-2 cells through E-cadherin--actin complexes.

Enterocyte differentiation is a dynamic process during which reinforcement of cell-cell adhesion favours migration along the crypt-to-villus axis. Functional polarization of Caco-2 cells, the most commonly used model to study intestinal differentiation, is assessed by dome formation and tightness of the monolayer and is under the control of the extracellular matrix (ECM). Furthermore, our biochemical and confocal microscopy data demonstrate that the ECM dramatically reinforces E-cadherin targeting to the upper lateral membrane, formation of the apical actin cytoskeleton and its colocalization with E-cadherin in functional complexes. In our model, these effects were produced by native laminin-5-enriched ECM as well as by type IV collagen or laminin 2, which suggests a common pathway of induction through integrin receptors. Indeed, these effects were antagonized by blocking anti-beta1- and anti-alpha6-integrin antibodies and directly induced by a stimulating anti-beta1-integrin antibody. These results demonstrate that integrin-dependent cell to ECM adhesion reinforces E-cadherin-dependent cell-cell adhesion in Caco-2 cells and further support the notion that enterocyte differentiation is supported by a molecular crosstalk between the two adhesion systems of the cell.