Abl and Canoe/Afadin mediate mechanotransduction at tricellular junctions

doi:10.1126/science.aba5528

GSTDTAP > 气候变化

DOI	10.1126/science.aba5528
	Abl and Canoe/Afadin mediate mechanotransduction at tricellular junctions
	Huapeng H. Yu; Jennifer A. Zallen
	2020-11-27
发表期刊	Science
出版年	2020
英文摘要	Cells exist in varying environments and must respond to specific stimuli. During development, epithelial cells need to rapidly reorganize under tension without compromising epithelial integrity. Yu et al. demonstrate that Drosophila epithelial cells achieve this by transiently stabilizing adhesion at tricellular junctions where three cells meet (see the Perspective by Raghavan and Vasioukhin). The conserved adhesion regulator Canoe/Afadin is recruited to tricellular junctions under tension within seconds and dissociates when tension is released through a mechanism that requires Abl-dependent tyrosine phosphorylation. These results identify an in vivo mechanotransduction pathway that dynamically couples tricellular adhesion with physiological forces, allowing cells to rapidly modulate their behavior in response to mechanical changes in their environment. Science , this issue p. [eaba5528][1]; see also p. [1036][2] ### INTRODUCTION The ability to sense and respond to mechanical force is an intrinsic property of cells that is critical for normal cell function and often deregulated in disease. Mechanical forces induce changes in protein conformation, localization, activity, and posttranslational modification in vitro. An outstanding question is how mechanical signals modulate protein function and cell behavior in response to the physiological forces encountered by cells in living organisms. Tyrosine phosphorylation has long been recognized to be enriched at adherens junctions, which detect and transmit forces between epithelial cells, and can be directly enhanced by mechanical forces in vitro. However, whether mechanical forces influence tyrosine kinase signaling in vivo, and the consequences of this regulation for cell behavior, are not known. ### RATIONALE An important step in the development of epithelial organs is the remodeling of cell adhesion in response to mechanical forces, which transforms epithelial sheets into diverse structures. Tricellular junctions (TCJs) where three cells meet are dynamically assembled and disassembled during cell rearrangement and are predicted to be sites of increased tension during epithelial remodeling, providing an opportunity to investigate how cells respond to mechanical forces. However, the mechanisms that allow tricellular junctions to rapidly remodel under tension without disrupting epithelial continuity are not well understood. Identifying and characterizing proteins that localize to tricellular junctions under tension can provide insight into the mechanotransduction pathways that modulate cell adhesion in response to mechanical forces in vivo. ### RESULTS Using time-lapse imaging and a method to directly visualize tyrosine phosphorylation in living embryos, we found that tyrosine phosphorylation is increased at tricellular junctions in a tension-dependent fashion during Drosophila convergent extension. By screening a library of tagged proteins, we identified Canoe as a tyrosine-phosphorylated protein that localizes to tricellular junctions under tension. Canoe recruitment to tricellular junctions dynamically correlated with changes in myosin localization, and Canoe rapidly dissociated from tricellular junctions when tension was released by laser ablation. The enrichment of Canoe at tricellular junctions required Abl-dependent tyrosine phosphorylation of Canoe at Y1987, a conserved site in the Canoe actin-binding domain. Decreasing Abl expression or mutating this tyrosine to an unphosphorylatable amino acid significantly reduced Canoe enrichment at tricellular junctions and disrupted tricellular adhesion in vivo. To determine whether the dynamic recruitment of Canoe to tricellular junctions is important for cell rearrangement, we developed a “vertex trap” method to constitutively target Venus-tagged Canoe to tricellular junctions independently of mechanical inputs. Stably anchoring Canoe at tricellular junctions aberrantly stabilized adhesion at four-way vertices and arrested cell rearrangement. These results suggest that Canoe levels dynamically modulate the strength of cell adhesion at tricellular junctions to facilitate cell rearrangement. ### CONCLUSION These results identify a mechanotransduction pathway that dynamically couples tricellular adhesion with mechanical forces during epithelial remodeling. Canoe recruitment to tricellular junctions requires actomyosin contractility and Abl-dependent phosphorylation of a conserved tyrosine in the Canoe actin-binding domain. Loss of Canoe disrupts tricellular adhesion, and increasing Canoe levels at tricellular junctions slows or arrests cell rearrangement, influencing the rate of epithelial remodeling. In one model, Canoe could act as a mechanosensor, physically stretching under tension to expose a phosphorylation site for Abl. Alternatively, tension could enhance Abl activity or generate a unique configuration of actin or other molecules at tricellular junctions that is recognized by Canoe. Tricellular junctions influence many processes required for epithelial development and homeostasis, including cell rearrangement, cell division, stem cell self-renewal, and barrier function. A better understanding of the composition, organization, and dynamic properties of tricellular junctions will provide insight into how these structures sense and integrate mechanical forces in epithelia. ![Figure][3] Regulation of tricellular adhesion by tension requires Canoe and the Abl tyrosine kinase. (Top) Localization of phosphotyrosine (white), Canoe-Venus (green), and myosin-mCherry (red) in the Drosophila embryo. (Bottom) Canoe localization at tricellular junctions is enhanced by Abl and cytoskeletal tension. This force-sensitive mechanism is important for cell adhesion and epithelial remodeling. Epithelial structure is generated by the dynamic reorganization of cells in response to mechanical forces. Adherens junctions transmit forces between cells, but how cells sense and respond to these forces in vivo is not well understood. We identify a mechanotransduction pathway involving the Abl tyrosine kinase and Canoe/Afadin that stabilizes cell adhesion under tension at tricellular junctions in the Drosophila embryo. Canoe is recruited to tricellular junctions in response to actomyosin contractility, and this mechanosensitivity requires Abl-dependent phosphorylation of a conserved tyrosine in the Canoe actin-binding domain. Preventing Canoe tyrosine phosphorylation destabilizes tricellular adhesion, and anchoring Canoe at tricellular junctions independently of mechanical inputs aberrantly stabilizes adhesion, arresting cell rearrangement. These results identify a force-responsive mechanism that stabilizes tricellular adhesion under tension during epithelial remodeling. [1]: /lookup/doi/10.1126/science.aba5528 [2]: /lookup/doi/10.1126/science.abf2782 [3]: pending:yes
领域	气候变化 ; 资源环境
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引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/304875
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Huapeng H. Yu,Jennifer A. Zallen. Abl and Canoe/Afadin mediate mechanotransduction at tricellular junctions[J]. Science,2020.
APA	Huapeng H. Yu,&Jennifer A. Zallen.(2020).Abl and Canoe/Afadin mediate mechanotransduction at tricellular junctions.Science.
MLA	Huapeng H. Yu,et al."Abl and Canoe/Afadin mediate mechanotransduction at tricellular junctions".Science (2020).