Abstract
Adherens junctions (AJs) are key structures regulating tissue integrity and maintaining adhesion between cells. During morphogenesis, junctional proteins cooperate closely with the actomyosin network to drive cell movement and shape changes. How the junctions integrate the mechanical forces in space and in time during an in vivo morphogenetic event is still largely unknown, due to a lack of quantitative data. To address this issue, we inserted a functional Fluorescence Resonance Energy Transfer (FRET)-based force biosensor within HMP-1/α-catenin of Caenorhabditis elegans. We find that the tension exerted on HMP-1 has a cell-specific distribution, is actomyosin-dependent, but is regulated differently from the tension on the actin cortex during embryonic elongation. By using time-lapse analysis of mutants and tissue-specific rescue experiments, we confirm the role of VAB-9/Claudin as an actin bundle anchor. Nevertheless, the tension exerted on HMP-1 did not increase in the absence of VAB-9/Claudin, suggesting that HMP-1 activity is not upregulated to compensate for loss of VAB-9. Our data indicate that HMP-1 does not modulate HMR-1/E-cadherin turnover, is required to recruit junctional actin but not stress fiber-like actin bundles. Altogether, our data suggest that HMP-1/α-catenin acts to promote the mechanical integrity of adherens junctions.
Highlights
Adherens junctions (AJs) are conserved structures essential to maintain tissue architecture and cell-to-cell communication
We found no significant difference between the Fluorescence Resonance Energy Transfer (FRET) index between these two genotypes for all the junctions of H1, V1 or V3 (Fig 3A– 3C), suggesting that loss of VAB-9 does not reallocate the tension onto HMP-1
By using a FRET-based force sensor integrated in the endogenous HMP-1/αcatenin to assess the tension exerted on AJs and by performing time-lapse fluorescence microscopy we revisited the role of HMP-1 during C. elegans embryonic elongation
Summary
Adherens junctions (AJs) are conserved structures essential to maintain tissue architecture and cell-to-cell communication. They have been the subject of extensive investigation since their discovery many decades ago [1]. Studies in both cell culture and living embryos have identified the core components of AJs, the cadherin-catenin complex (CCC), and their importance in cell physiology, organism development and disease [2, 3]. E-cadherin is a Ca2+ binding transmembrane protein that forms trans-homodimers, bridging the plasma membranes of two adjacent epithelial cells [4]. E-cadherin contains a cytoplasmic tail that binds β-catenin, which in turn binds to α-catenin.
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