title: Adherens junction-dependent PI3K/Akt activation induces resistance to genotoxin-induced cell death in differentiated intestinal epithelial cells.
abstract: The crypt-villi axis of intestinal mucosa maintains homeostasis by renewal of epithelia, and also exhibits different properties from undifferentiated to terminally differentiated cells. We investigated differential susceptibility to genotoxin-induced cell death, based on the degree of differentiation of epithelial cells, and its mechanism. Differentiation was induced by post-confluence culture in Caco-2 cells. Methyl methanesulfonate (MMS), a direct-acting DNA alkylating agent, was used for genotoxin-induced cell death. Compared to subconfluent Caco-2 cells, 7 days post-confluent cells showed resistance to MMS-induced cell death. With increasing expression of adherens junction components of E-cadherin and beta-catenin, E-cadherin and p-Akt expression increased in 7 days post-confluent Caco-2 cells, and in human intestinal tissue, expression of E-cadherin and p-Akt also increased in the upper portion of villi, compared to the crypt. Inhibition of cell-cell adhesion using EGTA decreased Akt phosphorylation, which was reversed by calcium restoration. Akt phosphorylation by calcium-mediated cell-cell adhesion was more prominent in differentiated cells. In addition, treatment of a PI3K inhibitor, LY294002, inhibited Akt phosphorylation by calcium-mediated cell-cell adhesion. Finally, the differential sensitivity to MMS-induced cell death between subconfluent and 7 days post-confluent Caco-2 cells was eliminated by inhibiting cell-cell adhesion or PI3K. Our data demonstrated that cell adhesion-mediated PI3K/Akt activation could be one of the important mechanisms of resistance to genotoxin-induced cell death in differentiated epithelial cells.
authors.affiliation: Department of Internal Medicine and Institute of Gastroenterology, Yonsei University College of Medicine, Seodaemun-gu, Seoul, Republic of Korea.
authors.forename: Boah
authors.initials: B
authors.lastname: Chae
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Yang
authors.forename: Tae Il
authors.initials: TI
authors.lastname: Kim
authors.forename: Won Ho
authors.initials: WH
authors.lastname: Kim
mesh_terms: D022005:Adherens Junctions / Q000201:enzymology*; D017209:Apoptosis; D018938:Caco-2 Cells; D015820:Cadherins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation; D002867:Chromones / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis; D004351:Drug Resistance; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000819:agonists / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D015820:Cadherins; D002118:Calcium; D002867:Chromones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D008741:Methyl Methanesulfonate; D009025:Morpholines; D009153:Mutagens; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D051176:beta Catenin; C493956:CDKN1A protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one