The Tight Junction Protein ZO-1 Establishes a Link between the Transmembrane Protein Occludin and the Actin Cytoskeleton

Abstract

The tight junction protein ZO-1 belongs to a family of multidomain proteins known as the membrane-associated guanylate kinase homologs (MAGUKs). ZO-1 has been demonstrated to interact with the transmembrane protein occludin, a second tight junction-specific MAGUK, ZO-2, and F-actin, although the nature and functional significance of these interactions is poorly understood. To further elucidate the role of ZO-1 within the epithelial tight junction, we have introduced epitope-tagged fragments of ZO-1 into cultured MDCK cells and identified domains critical for the interaction with ZO-2, occludin, and F-actin. A combination of in vitro and in vivo binding assays indicate that both ZO-2 and occludin interact with specific domains within the N-terminal (MAGUK-like) half of ZO-1, whereas the unique proline-rich C-terminal half of ZO-1 cosediments with F-actin. Consistent with these observations, we found that a construct encoding the N-terminal half of ZO-1 is specifically associated with tight junctions, whereas the unique C-terminal half of ZO-1 is distributed over the entire lateral surface of the plasma membrane and other actin-rich structures. In addition, we have identified a 244-amino acid domain within the Nterminal half of ZO-1, which is required for the stable incorporation of ZO-1 into the junctional complex of polarized MDCK cells. These observations suggest that one functional role of ZO-1 is to organize components of the tight junction and link them to the cortical actin cytoskeleton.

Low doses of microencapsulated zinc oxide improve performance and modulate the ileum architecture, inflammatory cytokines and tight junctions expression of weaned pigs

“…filaments of the cell cytoskeleton (Fanning et al, 1998). In this study, ZO-1 protein content was higher in pigs fed with the highest dose of mZnO compared with control and pZnO and this confirms the protective role of Zn from ZnO in preventing TNF-α and IFN-γ-mediated increase in para-cellular permeability and alteration of TJ functionality.…”

Distinct effects of Vibrio cholerae haemagglutinin/protease on the structure and localization of the tight junction-associated proteins occludin and ZO-1

“…Our previous experiments (Wu et al, 1996) have shown that HA /P rearranged ZO-1, which is localized beneath the cell membrane inside the cells and is a direct link between occludin and the F-actin cytoskeleton (Fanning et al, 1998). We therefore investigated whether HA /P can induce degradation of ZO-1 as well.…”

Cleavage of MAGI-1, a tight junction PDZ protein, by caspases is an important step for cell-cell detachment in apoptosis

“…This is a function for which MAGUKs are extremely well adapted: mediating such protein-protein interactions [17]. Indeed, several MAGUKs have been found to bind to components of the cadherin-actin system [55][56][57][58][59] and it has also been suggested that they link the tight junction constituents, occludin and claudins, with actin filaments [39]. MAGI-1 itself has been shown to localise to tight and adherens junctions [28], where it interacts with the β-catenin-E-cadherin complex [26], with the synaptopodin and alphaactinin-4 actin binding proteins [28], and with the JAM4 cell adhesion protein [29].…”