Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
Cells. 2022 Nov 23;11(23):3740. doi: 10.3390/cells11233740.
The extracellular matrix (ECM) plays crucial roles in tissue homeostasis. Abnormalities in ECM composition are associated with pathological conditions, such as fibrosis and cancer. These ECM alterations are sensed by the epithelium and can influence its behavior through crosstalk with other mechanosensitive complexes, including the adherens junctions (AJs). We have previously shown that the AJs, through their component PLEKHA7, recruit the RNAi machinery to regulate miRNA levels and function. We have particularly shown that the junctional localization of RNAi components is critical for their function. Here, we investigated whether different ECM substrates can influence the junctional localization of RNAi complexes. To do this, we plated colon epithelial Caco2 cells on four key ECM substrates found in the colon under normal or pathogenic conditions, namely laminin, fibronectin, collagen I, and collagen IV, and we examined the subcellular distribution of PLEKHA7, and of the key RNAi components AGO2 and DROSHA. Fibronectin and collagen I negatively impacted the junctional localization of PLEKHA7, AGO2, and DROSHA when compared to laminin. Furthermore, fibronectin, collagen I, and collagen IV disrupted interactions of AGO2 and DROSHA with their essential partners GW182 and DGCR8, respectively, both at AJs and throughout the cell. Combinations of all substrates with fibronectin also negatively impacted junctional localization of PLEKHA7 and AGO2. Additionally, collagen I triggered accumulation of DROSHA at tri-cellular junctions, while both collagen I and collagen IV resulted in DROSHA accumulation at basal areas of cell-cell contact. Altogether, fibronectin and collagens I and IV, which are elevated in the stroma of fibrotic and cancerous tissues, altered localization patterns and disrupted complex formation of PLEKHA7 and RNAi components. Combined with our prior studies showing that apical junctional localization of the PLEKHA7-RNAi complex is critical for regulating tumor-suppressing miRNAs, this work points to a yet unstudied mechanism that could contribute to epithelial cell transformation.
细胞外基质 (ECM) 在组织稳态中发挥着关键作用。ECM 组成的异常与纤维化和癌症等病理状况有关。上皮细胞可以感知这些 ECM 的改变，并通过与其他机械敏感复合物（包括黏着连接 (AJs)）的相互作用来影响其行为。我们之前已经表明，AJs 通过其组成蛋白 PLEKHA7 招募 RNAi 机制来调节 miRNA 的水平和功能。我们特别表明，RNAi 成分的连接定位对于它们的功能至关重要。在这里，我们研究了不同的 ECM 基质是否会影响 RNAi 复合物的连接定位。为此，我们将结肠上皮细胞 Caco2 种植在正常或病理条件下结肠中存在的四种关键 ECM 基质上，即层粘连蛋白、纤连蛋白、I 型胶原和 IV 型胶原，并检查了 PLEKHA7 的亚细胞分布以及关键的 RNAi 成分 AGO2 和 DROSHA。与层粘连蛋白相比，纤连蛋白和 I 型胶原会负向影响 PLEKHA7、AGO2 和 DROSHA 的连接定位。此外，纤连蛋白、I 型胶原和 IV 型胶原分别破坏了 AGO2 和 DROSHA 与其必需伴侣 GW182 和 DGCR8 的相互作用，无论是在 AJs 还是在整个细胞中。所有基质与纤连蛋白的组合也会负向影响 PLEKHA7 和 AGO2 的连接定位。此外，I 型胶原会导致 DROSHA 在三叉细胞连接处聚集，而 I 型胶原和 IV 型胶原都会导致 DROSHA 在细胞-细胞接触的基底区域聚集。总的来说，在纤维化和癌症组织的基质中升高的纤连蛋白和 I 型和 IV 型胶原改变了 PLEKHA7 和 RNAi 成分的定位模式并破坏了复合物的形成。结合我们之前的研究表明，PLEKHA7-RNAi 复合物的顶端连接定位对于调节肿瘤抑制 miRNA 至关重要，这项工作指出了一种尚未研究的机制，可能有助于上皮细胞转化。
