Liang Xuan, Kiru Sajini, Gomez Guillermo A, Yap Alpha S
Division of Cell Biology and Molecular Medicine, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, South Australia 5000, Australia.
Cytoskeleton (Hoboken). 2018 Feb;75(2):61-69. doi: 10.1002/cm.21420. Epub 2017 Dec 5.
Adherens junctions in epithelia are contractile structures, where coupling of adhesion to the actomyosin cytoskeleton generates mechanical tension for morphogenesis and homeostasis. In established monolayers, junctional contractility is supported by the interplay between cell signals and scaffolding proteins. However, less is known about how contractile junctions develop, especially during the establishment of epithelial monolayers. Here, we show that junctional tension increases concomitant with accumulation of actomyosin networks as Caco-2 epithelia become confluent. This is associated with development of a zone of RhoA signaling at junctions. Further, we find that the low levels of RhoA signaling and contractility found in subconfluent cultures reflect a mechanism for their active suppression. Specifically, the RhoA antagonist, SRGAP1, is present at subconfluent junctions to a greater extent than in confluent cultures and SRGAP1 RNAi restores RhoA signaling and contractility in subconfluent cultures to levels seen in confluent cells. Overall, these observations suggest that regulated changes in junctional contractility mediated by modulation of RhoA signaling occur as epithelial monolayers mature.
上皮细胞中的黏附连接是收缩性结构，其中黏附与肌动球蛋白细胞骨架的偶联为形态发生和体内平衡产生机械张力。在已建立的单层细胞中，细胞信号和支架蛋白之间的相互作用支持着连接收缩性。然而，关于收缩性连接如何形成，尤其是在上皮单层细胞形成过程中，人们了解较少。在这里，我们表明，随着Caco-2上皮细胞汇合，连接张力增加，同时肌动球蛋白网络积累。这与连接处RhoA信号区的形成有关。此外，我们发现，在亚汇合培养物中发现的低水平RhoA信号和收缩性反映了一种主动抑制机制。具体而言，RhoA拮抗剂SRGAP1在亚汇合连接处的存在程度高于汇合培养物，并且SRGAP1 RNA干扰可将亚汇合培养物中的RhoA信号和收缩性恢复到汇合细胞中的水平。总体而言，这些观察结果表明，随着上皮单层细胞成熟，由RhoA信号调节介导的连接收缩性发生有规律的变化。
