Deconstructing the Cadherin-Catenin-Actin Complex

Protein interaction networks and protein compartmentalization underlie all signaling and regulatory processes in cells. Enzyme-catalyzed proximity labeling (PL) has emerged as a new approach to study the spatial and interaction characteristics of proteins in living cells. However, current PL methods require over 18 h of labeling time or utilize chemicals with limited cell permeability or high toxicity. We used yeast display-based directed evolution to engineer two promiscuous mutants of biotin ligase, TurboID and miniTurbo, which catalyze PL with much greater efficiency than BioID or BioID2, and enable 10-min PL in cells with non-toxic and easily deliverable biotin. Furthermore, TurboID extends biotin-based PL to flies and worms.

Efficient proximity labeling in living cells and organisms with TurboID.

How adhesive interactions between cells generate and maintain animal tissue structure remains one of the most challenging and long-standing questions in cell and developmental biology. Adherens junctions (AJs) and the cadherin-catenin complexes at their core are therefore the subjects of intense research. Recent work has greatly advanced our understanding of the molecular organization of AJs and how cadherin-catenin complexes engage actin, microtubules and the endocytic machinery. As a result, we have gained important insights into the molecular mechanisms of tissue morphogenesis.

Adherens junctions: from molecules to morphogenesis

Introduction Cell-cell fusion is a key event in fertilization and during differentiation of muscle, bone and trophoblast cells, and possibly also in stem-cell plasticity, carcinogenesis and tumor progression (Chen et al. Earlier work on fusion mechanisms has been focused on the earliest stages of the fusion pathways, which bring about the first measurable indications of fusion: lipid mixing and the opening of a narrow fusion pore – an aqueous connection between the membranes (Earp et al. Weissenhorn et al., 2007). At later stages of cell-cell fusion, these initial pores of a few nanometers in diameter expand to pores that are readily detectable by fluorescence microscopy (diameter >~0.2 μm) and finally yield an open lumen of cell-size diameter (~10-15 μm). Little is known about the properties of these larger pores and the mechanisms that underlie the enlargement of cytoplasmic bridges from early fusion pores to syncytia (Gattegno et al. For instance, we still do not know whether this enlargement proceeds spontaneously and, if not, whether it is driven by the cytoskeleton (Podbilewicz and White, 1994; Zheng and Chang, 1991), membrane tension (Knutton, 1980) or another, as-yet unidentified, cell machinery. The role of the actin cytoskeleton in cell-cell fusion has drawn special attention in many recent studies. Syncytium formation,

Technical Summary

Sticky Business: Orchestrating Cellular Signals at Adherens Junctions

During morphogenesis of the Caenorhabditis elegans embryo, hypodermal (or epidermal) cells migrate to enclose the embryo in an epithelium and, subsequently, change shape coordinately to elongate the body (Priess, J.R., and D.I. Hirsh. 1986. Dev. Biol. 117:156– 173; Williams-Masson, E.M., A.N. Malik, and J. Hardin. 1997. Development [Camb.]. 124:2889–2901). We have isolated mutants defective in morphogenesis that identify three genes required for both cell migration during body enclosure and cell shape change during body elongation. Analyses of hmp-1 , hmp-2 , and hmr-1 mutants suggest that products of these genes anchor contractile actin filament bundles at the adherens junctions between hypodermal cells and, thereby, transmit the force of bundle contraction into cell shape change. The protein products of all three genes localize to hypodermal adherens junctions in embryos. The sequences of the predicted HMP-1, HMP-2, and HMR-1 proteins are related to the cell adhesion proteins α-catenin, β-catenin/Armadillo, and classical cadherin, respectively. This putative catenin–cadherin system is not essential for general cell adhesion in the C. elegans embryo, but rather mediates specific aspects of morphogenetic cell shape change and cytoskeletal organization.

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A Putative Catenin–Cadherin System Mediates Morphogenesis of the Caenorhabditis elegans Embryo

http://worms.zoology.wisc.edu/pdfs/leung-DB.pdf

Ben Leung

Papers

A Putative Catenin–Cadherin System Mediates Morphogenesis of the Caenorhabditis elegans Embryo

Organogenesis of the Caenorhabditis elegans intestine.