title: Cingulin regulates claudin-2 expression and cell proliferation through the small GTPase RhoA.
abstract: In mouse embryoid bodies, mutation of the tight junction protein cingulin results in changes in gene expression. Here, we studied the function of cingulin using a gene silencing approach in Madin-Darby canine kidney (MDCK) cells. Cingulin-depleted cells show higher protein and mRNA levels of claudin-2 and ZO-3, increased RhoA activity, activation of G1/S phase transition, and increased cell density. The effects of cingulin depletion on claudin-2 expression, cell proliferation, and density are reversed by coexpression of either a dominant-negative form of RhoA (RhoAN19) or the Rho-inhibiting enzyme C3 transferase. However, the increase in ZO-3 protein and mRNA levels is not reversed by inhibition of either RhoA, p38, extracellular signal-regulated kinase (ERK), or c-Jun NH2-terminal kinase (JNK), suggesting that cingulin modulates ZO-3 expression by a different mechanism. JNK is implicated in the regulation of claudin-2 levels independently of cingulin depletion and RhoA activity, indicating distinct roles of RhoA- and JNK-dependent pathways in the control of claudin-2 expression. Finally, cingulin depletion does not significantly alter the barrier function of monolayers and the overall molecular organization of tight junctions. These results provide novel insights about the mechanisms of cingulin function and the signaling pathways controlling claudin-2 expression in MDCK cells.
authors.affiliation: Department of Molecular Biology, University of Geneva, CH-1211 Geneva, Switzerland.
authors.forename: Laurent
authors.initials: L
authors.lastname: Guillemot
authors.forename: Sandra
authors.initials: S
authors.lastname: Citi
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002452:Cell Count; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology; D016193:G1 Phase; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000172:deficiency / Q000378:metabolism*; D021381:Protein Transport; D016196:S Phase; D019108:Tight Junctions / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics; D062825:Zonula Occludens Proteins; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D062825:Zonula Occludens Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020742:rhoA GTP-Binding Protein