Human homolog of disc-large is required for adherens junction assembly and differentiation of human intestinal epithelial cells.
We and others have shown that phosphatidylinositol 3-kinase (PI3K) is recruited to and activated by E-cadherin engagement. This PI3K activation is essential for adherens junction integrity and intestinal epithelial cell differentiation. Here we provide evidence that hDlg, the homolog of disc-large tumor suppressor, is another key regulator of adherens junction integrity and differentiation in mammalian epithelial cells. We report the following. 1) hDlg co-localizes with E-cadherin, but not with ZO-1, at the sites of cell-cell contact in intestinal epithelial cells. 2) Reduction of hDlg expression levels by RNA(i) in intestinal cells not only severely alters adherens junction integrity but also prevents the recruitment of p85/PI3K to E-cadherin-mediated cell-cell contact and inhibits sucrase-isomaltase gene expression. 3) PI3K and hDlg are associated with E-cadherin in a common macromolecular complex in living differentiating intestinal cells. 4) This interaction requires the association of hDlg with E-cadherin and with Src homology domain 2 domains of the p85/PI3K subunit. 5) Phosphorylation of hDlg on serine and threonine residues prevents its interaction with the p85 Src homology domain 2 in subconfluent cells, whereas phosphorylation of hDlg on tyrosine residues is essential. We conclude that hDlg may be a determinant in E-cadherin-mediated adhesion and signaling in mammalian epithelial cells.
Laprise
Patrick
P
Canadian Institutes of Health Research Group on Functional Development and Physiopathology of the Digestive Tract, Département d'Anatomie et Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Québec J1H 5N4, Canada.
Viel
Alain
A
Rivard
Nathalie
N
D048868:Adaptor Proteins, Signal Transducing; D022005:Adherens Junctions / Q000502:physiology*; D001665:Binding Sites; D015153:Blotting, Western; D018938:Caco-2 Cells; D015820:Cadherins / Q000096:biosynthesis; D002448:Cell Adhesion; D002450:Cell Communication; D002454:Cell Differentiation; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism; D000074288:Discs Large Homolog 1 Protein; D004847:Epithelial Cells / Q000166:cytology*; D017930:Genes, Reporter; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology*; D008156:Luciferases / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000096:biosynthesis; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000502:physiology*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013347:Subcellular Fractions; D013912:Threonine / Q000737:chemistry; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D062826:Zonula Occludens-1 Protein; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; D000074288:Discs Large Homolog 1 Protein; D008156:Luciferases; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D011506:Proteins; D012694:Serine; D013912:Threonine; D014443:Tyrosine; D062826:Zonula Occludens-1 Protein; C513314:DLG1 protein, human; C569042:TJP1 protein, human