Mammalian Diaphanous 1 Mediates a Pathway for E-cadherin to Stabilize Epithelial Barriers through Junctional Contractility

Abstract

Formins are a diverse class of actin regulators that influence filament dynamics and organization. Several formins have been identified at epithelial adherens junctions, but their functional impact remains incompletely understood. Here, we tested the hypothesis that formins might affect epithelial interactions through junctional contractility. We focused on mDia1, which was recruited to the zonula adherens (ZA) of established Caco-2 monolayers in response to E-cadherin and RhoA. mDia1 was necessary for contractility at the ZA, measured by assays that include a FRET-based sensor that reports molecular-level tension across αE-catenin. This reflected a role in reorganizing F-actin networks to form stable bundles that resisted myosin-induced stress. Finally, we found that the impact of mDia1 ramified beyond adherens junctions to stabilize tight junctions and maintain the epithelial permeability barrier. Therefore, control of tissue barrier function constitutes a pathway for cadherin-based contractility to contribute to the physiology of established epithelia.

A mechanosensitive RhoA pathway that protects epithelia against acute tensile stress

“…Turnover studies suggest that this reflects a failure to stabilize Ecadherin, which may be due to a concomitant failure of F-actin dynamics to respond to the stress. This is consistent with earlier evidence that RhoA stimulates actin regulators, such as mDia1, which promote filament assembly and regulate F-actin network organization to stabilize E-cadherin at the ZA (Acharya, et al, 2017;Rao and Zaidel-Bar, 2016;Carramusa, et al, 2007).…”

“…The junctional tautening was consistent with our recent observation that calyculin increases junctional tension, as measured by their recoil following laser ablation (Acharya, et al, 2017). We further confirmed this at the molecular level using a FRET-based tension sensor incorporated into αcatenin (αCat-TS) (Acharya, et al, 2017). Calyculin decreased energy transfer across αCat-TS ( Figure 1E and S1C), consistent with an increase in tension.…”

“…Consistent with predictions of the model, little movement of the cells was observed, but junctions appeared to tauten almost immediately after adding calyculin (Movie S2) and remained intact for ~12 min, until they fractured at the very end of the movies. The junctional tautening was consistent with our recent observation that calyculin increases junctional tension, as measured by their recoil following laser ablation (Acharya, et al, 2017). We further confirmed this at the molecular level using a FRET-based tension sensor incorporated into αcatenin (αCat-TS) (Acharya, et al, 2017).…”

Caveolae set levels of epithelial monolayer tension to eliminate tumor cells

“…This increase in recoil was attributable to an increase in junctional tension, junctional friction being unchanged, as inferred from k-values when recoil was modelled as a Kelvin-Vogt fiber (Table S1). To corroborate this, we measured molecular level-tension at AJ using an a-catenin transgene that incorporates a FRET-based tensionsensor (TS) module (a-cat-TS) (Acharya et al, 2017). Energy transfer across a-cat-TS was reduced in CAV1 KD cells compared with controls (Fig 3e), indicating an increase in molecular-level tension.…”

Quantifying Tensile Forces at Cell–Cell Junctions with a DNA-based Fluorescent Probe

“…Intercellular mechanical forces, especially tensile forces, play important roles in development, tissue healing and cancer invasion [1][2][3] . These tensile forces at cell-cell junctions actively reshape the tissues during morphogenesis in embryos, and are also evident in quiescent adult tissues [4][5][6] , especially epithelial and endothelial monolayers 7,8 . Cadherins constitute a superfamily of cell-cell adhesion molecules that are expressed in various types of cells 9,10 .…”