Dataset Information

Predominant Distribution of the RNAi Machinery at Apical Adherens Junctions in Colonic Epithelia Is Disrupted in Cancer.

ABSTRACT: The RNA interference (RNAi) machinery is an essential component of the cell, regulating miRNA biogenesis and function. RNAi complexes were thought to localize either in the nucleus, such as the microprocessor, or in the cytoplasm, such as the RNA-induced silencing complex (RISC). We recently revealed that the core microprocessor components DROSHA and DGCR8, as well as the main components of RISC, including Ago2, also associate with the apical adherens junctions of well-differentiated cultured epithelial cells. Here, we demonstrate that the localization of the core RNAi components is specific and predominant at apical areas of cell-cell contact of human normal colon epithelial tissues and normal primary colon epithelial cells. Importantly, the apical junctional localization of RNAi proteins is disrupted or lost in human colon tumors and in poorly differentiated colon cancer cell lines, correlating with the dysregulation of the adherens junction component PLEKHA7. We show that the restoration of PLEKHA7 expression at adherens junctions of aggressively tumorigenic colon cancer cells restores the junctional localization of RNAi components and suppresses cancer cell growth in vitro and in vivo. In summary, this work identifies the apical junctional localization of the RNAi machinery as a key feature of the differentiated colonic epithelium, with a putative tumor suppressing function.

SUBMITTER: Nair-Menon J

PROVIDER: S-EPMC7177752 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Predominant Distribution of the RNAi Machinery at Apical Adherens Junctions in Colonic Epithelia Is Disrupted in Cancer.

Nair-Menon Joyce J Daulagala Amanda C AC Connor Dean M DM Rutledge Lauren L Penix Trevor T Bridges Mary Catherine MC Wellslager Bridgette B Spyropoulos Demetri D DD Timmers Cynthia D CD Broome Ann-Marie AM Kourtidis Antonis A

International journal of molecular sciences 20200407 7

The RNA interference (RNAi) machinery is an essential component of the cell, regulating miRNA biogenesis and function. RNAi complexes were thought to localize either in the nucleus, such as the microprocessor, or in the cytoplasm, such as the RNA-induced silencing complex (RISC). We recently revealed that the core microprocessor components DROSHA and DGCR8, as well as the main components of RISC, including Ago2, also associate with the apical adherens junctions of well-differentiated cultured ep ...[more]

PMID: 32272708

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Project description:The shaping of a multicellular body, and the maintenance and repair of adult tissues require fine-tuning of cell adhesion responses and the transmission of mechanical load between the cell, its neighbors and the underlying extracellular matrix. A growing field of research is focused on how single cells sense mechanical properties of their micro-environment (extracellular matrix, other cells), and on how mechanotransduction pathways affect cell shape, migration, survival as well as differentiation. Within multicellular assemblies, the mechanical load imposed by the physical properties of the environment is transmitted to neighboring cells. Force imbalance at cell-cell contacts induces essential morphogenetic processes such as cell-cell junction remodeling, cell polarization and migration, cell extrusion and cell intercalation. However, how cells respond and adapt to the mechanical properties of neighboring cells, transmit forces, and transform mechanical signals into chemical signals remain open questions. A defining feature of compact tissues is adhesion between cells at the specialized adherens junction (AJ) involving the cadherin super-family of Ca(2+)-dependent cell-cell adhesion proteins (e.g., E-cadherin in epithelia). Cadherins bind to the cytoplasmic protein ?-catenin, which in turn binds to the filamentous (F)-actin binding adaptor protein ?-catenin, which can also recruit vinculin, making the mechanical connection between cell-cell adhesion proteins and the contractile actomyosin cytoskeleton. The cadherin-catenin adhesion complex is a key component of the AJ, and contributes to cell assembly stability and dynamic cell movements. It has also emerged as the main route of propagation of forces within epithelial and non-epithelial tissues. Here, we discuss recent molecular studies that point toward force-dependent conformational changes in ?-catenin that regulate protein interactions in the cadherin-catenin adhesion complex, and show that ?-catenin is the core mechanosensor that allows cells to locally sense, transduce and adapt to environmental mechanical constrains.

Project description: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.

Project description:Adherens junctions (AJs), together with tight junctions (TJs), form an apical junctional complex that regulates intestinal epithelial cell-to-cell adherence and barrier homeostasis. Within the AJ, membrane-bound E-cadherin binds β-catenin, which functions as an essential intracellular signaling molecule. We have previously identified a novel protein in the region of the apical junction complex, chloride channel protein-2 (ClC-2), that we have used to study TJ regulation. In this study, we investigated the possible effects of ClC-2 on the regulation of AJs in intestinal mucosal epithelial homeostasis and tumorigenicity. Mucosal homeostasis and junctional proteins were examined in wild-type (WT) and ClC-2 knockout (KO) mice as well as associated colonoids. Tumorigenicity and AJ-associated signaling were evaluated in a murine colitis-associated tumor model and in a colorectal cancer cell line (HT-29). Colonic tissues from ClC-2 KO mice had altered ultrastructural morphology of intercellular junctions with reduced colonocyte differentiation, whereas jejunal tissues had minimal changes. Colonic crypts from ClC-2 KO mice had significantly higher numbers of less-differentiated forms of colonoids compared with WT. Furthermore, the absence of ClC-2 resulted in redistribution of AJ proteins and increased β-catenin activity. Downregulation of ClC-2 in colorectal cells resulted in significant increases in proliferation associated with disruption of AJs. Colitis-associated tumors in ClC-2 KO mice were significantly increased, associated with β-catenin transcription factor activation. The absence of ClC-2 results in less differentiated colonic crypts and increased tumorigenicity associated with colitis via dysregulation of AJ proteins and activation of β-catenin-associated signaling. NEW & NOTEWORTHY Disruption of adherens junctions in the absence of chloride channel protein-2 revealed critical functions of these junctional structures, including maintenance of colonic homeostasis and differentiation as well as driving tumorigenicity by regulating β-catenin signaling.

Dataset Information

Predominant Distribution of the RNAi Machinery at Apical Adherens Junctions in Colonic Epithelia Is Disrupted in Cancer.

Publications

Predominant Distribution of the RNAi Machinery at Apical Adherens Junctions in Colonic Epithelia Is Disrupted in Cancer.

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