Abstract

ZO-2 is a tight junction (TJ) protein that shuttles between the plasma membrane and the nucleus. ZO-2 contains several protein binding sites that allow it to function as a scaffold that clusters integral, adaptor and signaling proteins. To gain insight into the role of ZO-2 in epithelial cells, ZO-2 was silenced in MDCK cells with small interference RNA (siRNA). ZO-2 silencing triggered: (A) changes in the gate function of the TJ, determined by an increase in dextran flow through the paracellular route of mature monolayers and achievement of lower transepithelial electrical resistance values upon TJ de novo formation; (B) changes in the fence function of the TJ manifested by a non-polarized distribution of E-cadherin on the plasma membrane; (C) altered expression of TJ and adherens junction proteins, determined by a decreased amount of occludin and E-cadherin in mature monolayers and a delayed arrival to the plasma membrane of ZO-1, occludin and E-cadherin during a calcium switch assay; and (D) an atypical monolayer architecture characterized by the appearance of widened intercellular spaces, multistratification of regions in the culture and an altered pattern of actin at the cellular borders.