Actomyosin-generated tension on cadherin is similar between dividing and non-dividing epithelial cells in early Xenopus laevis embryos

Abstract

Epithelia represent a unique situation where polarized cells must maintain sufficiently strong cell-cell contacts to guarantee the epithelial integrity indispensable for barrier functions. Nevertheless, epithelia must also keep sufficient plasticity which is crucial during development and morphogenesis. Adherens junctions and mechanical forces produced by the actomyosin cytoskeleton are major players for epithelial integrity maintenance and plasticity regulations. To understand how the epithelium is able to meet such a challenge, it is indispensable to determine how cellular junctions and mechanical forces acting at adherens junctions are regulated. Here, we investigate the tensile forces acting on adherens junctions via cadherin during cell division in the Xenopus embryos epithelium. Using the recently developed E-cadherin FRET tension sensor and a fastFLIM prototype microscope, we were able to measure mechanical forces applied on cadherin at cell-cell junctions. We have shown that the Xenopus epithelium is under tension, approximately 3 pN which remains stable, indicating that tensile forces acting on cadherin at the adherens junction are at equilibrium. Unexpectedly, mechanical tension across cadherin was similar between dividing and non-dividing epithelial cells.

Tight junctions negatively regulate mechanical forces applied to adherens junctions in vertebrate epithelial tissue

“…5F-H). The absence of any effect on the tensile force could be explained by the fact that in Xenopus epithelium tensile forces applied on cadherin at the adherens junctions are at equilibrium; they are ∼3 pN (Herbomel et al, 2017), which is below the 5 pN required to unfold α-catenin and recruit vinculin (Yao et al, 2014). Expression of VinD1 suppressed the ring shape defect (Fig.…”

“…To test this assumption, we used CcadTSMod, a FRET tension-sensing probe. It consists of a tensile force-sensitive module (TSMod) integrated into the cytosolic domain of C-cadherin (Herbomel et al, 2017) (Fig. 3B).…”

“…pCS2-GFP-GPI (GFP-membrane) and pCS2-mRFP-GPI (RFPmembrane) plasmids were kindly provided by Michael Brand (Dresden University of Technology, Germany), pCS2-mCherry-Utr-CH was a gift from William M. Bement (Burkel et al, 2007), pCS2-Life-act-GFP was a gift from Ulrike Engel (Marx et al, 2013). For tension measurements, pT7T-CcadherinTSMod (Herbomel et al, 2017) was used. The CcadherinTSMod contains the entire FRET tension module created by Grashoff et al (2010) composed of an elastic linker interspaced between the fluorescence proteins mTFP1 and YFP integrated into the cytosolic cadherin domain.…”

“…This led to the hypothesis that constriction of the cytokinetic ring would induce variation of tensile forces applied on adherens junctions. Recently, we used a cadherin tension biosensor to investigate how mechanical forces acting at adherens junctions are regulated during cell division in the epithelium of Xenopus embryos (Herbomel et al, 2017). Using this approach, we have shown that the epithelium is under stable tension.…”

FRET-Based Biosensors: Genetically Encoded Tools to Track Kinase Activity in Living Cells

“…FRET is a nonradiative transfer of energy of one donor fluorophore to an acceptor fluorophore and relies on (i) an overlap of the emission spectrum of the donor with the excitation spectrum of the acceptor, (ii) an adequate orientation between the two fluorophores, and (iii) a distance less than 10 nm between the two [5]. This feature has been used to investigate various cellular events such as protein-protein interactions by genetically tagging the two proteins of interest with a donor and an acceptor fluorescent protein [6], the intra-cellular Ca 2+ signal by using calmodulin biosensor [7], proteases activity where the substrate is flanked by two fluorescent proteins, and the decrease of FRET indicates a cleavage of the protein [8], Rho GTPases for cytoskeleton dynamics [9,10], and mechanical forces at adherent junctions [11,12,13]. The first kinase biosensor has been developed for cAMP-dependant protein kinase A (PKA) [14].…”