ECM Substrates Impact RNAi Localization at Adherens Junctions of Colon Epithelial Cells

Abstract

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.

The epithelial adherens junction component PLEKHA7 regulates ECM remodeling and cell behavior through miRNA-mediated regulation of MMP1 and LOX

“…These results outline a potential novel mode of interaction between AJs and ECM, through the RNAi machinery, which could influence epithelial cell behavior. Altogether, our recently published (8,93) and present findings outline a mechanosensitive RNAi machinery that interacts with the ECM to fine-tune the mechanical responses and behavior of the cell. Fully delineating this crosstalk between the AJs and the ECM through RNAi and miRNAs and understanding all the components involved, can provide new insights into tissue homeostasis and disease pathogenesis, and will be the goal of our upcoming studies.…”

“…Due to their actomyosin connections, AJs are known mechanosensitive complexes that respond to mechanical cues, including those that stem from the ECM (78,92). Along these lines, we have previously shown that collagen I and fibronectin negatively affect the localization and complex formation of PLEKHA7 and of the RNAi machinery at adherens junctions and throughout the cell (93). Since collagen I and fibronectin introduce an ECM that exerts stronger forces to cells, which can accordingly alter cytoskeletal dynamics (21), it is likely that the effects of these ECM components to the junctional RNAi machinery and miRNAs are mediated by the actin cytoskeleton, especially since we have shown that the latter is critical for AGO2 localization and miRNA function at AJs.…”

Novel Preoperative Type IV Collagen to Predict the Risk of Hepatocellular Carcinoma in Patients with Hepatitis B Virus-Related Cirrhotic Portal Hypertension After Laparoscopic Splenectomy and Azygoportal Disconnection

“…C-IV will occur in the serum when the basement membrane is formed or destroyed. 23,24 MMP-2 and MMP-9 are the members of the matrix metalloproteinase (MMPs) family. Many studies have shown that MMPs, as important enzymes currently known to degrade ECM, play an important role in promoting tumor angiogenesis, metastasis, and invasion.…”

Actin-dependent recruitment of AGO2 to the zonula adherens

“…, 2015 , 2017b) and to fully reconstruct their regulation and roles in cell and tissue homeostasis and disease. For example, we have recently shown that different extracellular matrix (ECM) components distinctly impact localization and complex formation of RNAi components to the ZA, including not only RISC and AGO2, but also DROSHA and the microprocessor ( Daulagala and Kourtidis, 2022 ). It is well-established that different ECM components exert different mechanical forces in cells, which are primarily transmitted through the actomyosin cytoskeleton ( Janmey et al.…”