Saturday, May 4, 2024
5/4/2024
PROJECT SUMMARY Colorectal abnormalities such as pre-cancerous fibrotic disease and colon cancer are prevalent. However, the mechanisms that link the extensive extracellular matrix (ECM) remodeling that occurs during fibrosis to pro- tumorigenic cell transformation are still poorly understood. Compromised epithelial integrity is a common feature of these colorectal conditions. Recently, we discovered a mechanism that links epithelial tissue integrity with the RNA interference (RNAi) machinery, miRNA regulation, and colon cell behavior. We have shown that the adherens junctions, which is an essential architectural component of the cell, recruit the microprocessor and the RNAi-induced silencing complex (RISC), the core components of the RNAi machinery, as well as a specific set of miRNAs and mRNAs, in colon epithelial cells. This interaction occurs through PLEKHA7, a member of the E- cadherin cell-cell adhesion complex. PLEKHA7 loss results in compromised epithelial integrity, decreased levels and silencing activity of a set of miRNAs, increased oncogene expression and pro-tumorigenic cell transformation. We have also found extensive dysregulation of PLEKHA7 and of the junctional RNAi machinery in colon cancer cell lines and tumor patient samples. Colon epithelial tissues undergo abnormal physical stress during fibrosis and colon cancer due to excessive ECM remodeling, which promotes disease progression. Interestingly, our preliminary data reveal that application of physical stress to colon epithelial cells through the ECM results in mis-localization of the junctional RNAi machinery. We also have preliminary evidence that disruption of the junctional RNAi results in overexpression of ECM remodeling regulators and promotes ECM remodeling and cell migration. We hypothesize that biomechanical cues from the ECM result in dysregulation of PLEKHA7 and its associated RNAi machinery at the adherens junctions, promoting oncogene expression, further ECM remodeling, and pro-tumorigenic cell behavior. We will examine our hypothesis under two specific Aims: 1) Physical cues from the ECM regulate PLEKHA7-RNAi complex formation and function at adherens junctions; 2) PLEKHA7-associated miRNAs regulate ECM remodeling and pro-tumorigenic cell behavior. This study is significant, since it investigates a novel mechanistic link between physical changes in the ECM, epithelial integrity, and colon epithelial cell behavior through a localized function of the RNAi machinery. The proposed work is innovative by introducing the concept of a mechanosensitive RNAi machinery at adherens junctions. The impact of the study is that it will advance our understanding of the underlying mechanistic causes of intestinal diseases, particularly those connecting fibrotic conditions to pro-tumorigenic cell transformation. Since this involves miRNA regulation as the focal point in the crosstalk between ECM and colon cell behavior, the study can lead to future development of RNA-based therapeutics.
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