Patient-derived organoids and cellular spheroids recapitulate tissue physiology with remarkable fidelity. We investigated how engagement with a reconstituted basement membrane in three dimensions (3D) supports the polarized, stress resilient tissue phenotype of mammary epithelial spheroids. Cells interacting with reconstituted basement membrane in 3D had reduced levels of total and actin-associated filamin and decreased cortical actin tension that increased plasma membrane protrusions to promote negative plasma membrane curvature and plasma membrane protein associations linked to protein secretion. By contrast, cells engaging a reconstituted basement membrane in 2D had high cortical actin tension that forced filamin unfolding and endoplasmic reticulum (ER) associations. Enhanced filamin-ER interactions increased levels of PKR-like ER kinase effectors and ER-plasma membrane contact sites that compromised calcium homeostasis and diminished cell viability. Consequently, cells with decreased cortical actin tension had reduced ER stress and survived better. Consistently, cortical actin tension in cellular spheroids regulated polarized basement membrane membrane deposition and sensitivity to exogenous stress. The findings implicate cortical actin tension-mediated filamin unfolding in ER function and underscore the importance of tissue mechanics in organoid homeostasis.

中文翻译：

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ECM 维度调节肌动蛋白张力以调节乳腺上皮细胞的内质网功能和球体表型

源自患者的类器官和细胞球体以极高的保真度再现了组织生理学。我们研究了与三维 (3D) 重建基底膜的接合如何支持乳腺上皮球体的极化、应力弹性组织表型。与 3D 重建基底膜相互作用的细胞降低了总丝蛋白和肌动蛋白相关丝蛋白的水平，并降低了皮质肌动蛋白张力，从而增加了质膜突出，从而促进负质膜曲率和与蛋白质分泌相关的质膜蛋白关联。相比之下，以二维方式参与重建基底膜的细胞具有高皮质肌动蛋白张力，迫使细丝蛋白展开和内质网（ER）关联。增强的细丝蛋白-ER相互作用增加了PKR样ER激酶效应物和ER-质膜接触位点的水平，从而损害了钙稳态并降低了细胞活力。因此，皮质肌动蛋白张力降低的细胞减少了内质网应激，并且存活得更好。一致地，细胞球体中的皮质肌动蛋白张力调节极化基底膜沉积和对外源应激的敏感性。这些发现表明皮质肌动蛋白张力介导的丝蛋白展开在内质网功能中，并强调了组织力学在类器官稳态中的重要性。