Dynamic actin remodeling during epithelial–mesenchymal transition depends on increased moesin expression

Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA.
Molecular biology of the cell (Impact Factor: 4.47). 12/2011; 22(24):4750-64. DOI: 10.1091/mbc.E11-02-0119
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Remodeling of actin filaments is necessary for epithelial-mesenchymal transition (EMT); however, understanding of how this is regulated in real time is limited. We used an actin filament reporter and high-resolution live-cell imaging to analyze the regulated dynamics of actin filaments during transforming growth factor-β-induced EMT of mammary epithelial cells. Progressive changes in cell morphology were accompanied by reorganization of actin filaments from thin cortical bundles in epithelial cells to thick, parallel, contractile bundles that disassembled more slowly but remained dynamic in transdifferentiated cells. We show that efficient actin filament remodeling during EMT depends on increased expression of the ezrin/radixin/moesin (ERM) protein moesin. Cells suppressed for moesin expression by short hairpin RNA had fewer, thinner, and less stable actin bundles, incomplete morphological transition, and decreased invasive capacity. These cells also had less α-smooth muscle actin and phosphorylated myosin light chain in cortical patches, decreased abundance of the adhesion receptor CD44 at membrane protrusions, and attenuated autophosphorylation of focal adhesion kinase. Our findings suggest that increased moesin expression promotes EMT by regulating adhesion and contractile elements for changes in actin filament organization. We propose that the transciptional program driving EMT controls progressive remodeling of actin filament architectures.

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Available from: Jyoti Srivastava, Nov 26, 2014
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    • "- actin remodeling can affect the integrity of cell - cell junctions and destabilize the epithelial barrier , rendering leukocytes access to surrounding tissues . Reorganization of the actin cytoskeleton and loss of cell - cell adhesions are also seen in epithelial - mesenchymal transition , a phenomenon that occurs in fibrosis and wound healing ( Haynes et al . , 2011 ) . A significant reduction in f - actin levels in lateral wall , spiral ganglion and cochlear nerve at 3 – 7 days in vivo contrasts with an increase on this stress fibers component in the area where the electrode - analog was placed ( Figures 4 , 6 ) ."
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    ABSTRACT: Conservation of a patient's residual hearing and prevention of fibrous tissue/new bone formation around an electrode array are some of the major challenges in cochlear implant (CI) surgery. Although it is well-known that fibrotic tissue formation around the electrode array can interfere with hearing performance in implanted patients, and that associated intracochlear inflammation can initiate loss of residual hearing, little is known about the molecular and cellular mechanisms that promote this response in the cochlea. In vitro studies in neonatal rats and in vivo studies in adult mice were performed to gain insight into the pro-inflammatory, proliferative, and remodeling phases of pathological wound healing that occur in the cochlea following an electrode analog insertion. Resident Schwann cells (SC), macrophages, and fibroblasts had a prominent role in the inflammatory process in the cochlea. Leukocytes were recruited to the cochlea following insertion of a nylon filament in adult mice, where contributed to the inflammatory response. The reparative stages in wound healing are characterized by persistent neuro-inflammation of spiral ganglion neurons (SGN) and expression of regenerative monocytes/macrophages in the cochlea. Accordingly, genes involved in extracellular matrix (ECM) deposition and remodeling were up-regulated in implanted cochleae. Maturation of scar tissue occurs in the remodeling phase of wound healing in the cochlea. Similar to other damaged peripheral nerves, M2 macrophages and de-differentiated SC were observed in damaged cochleae and may play a role in cell survival and axonal regeneration. In conclusion, the insertion of an electrode analog into the cochlea is associated with robust early and chronic inflammatory responses characterized by recruitment of leukocytes and expression of pro-inflammatory cytokines that promote intracochlear fibrosis and loss of the auditory hair cells (HC) and SGN important for hearing after CI surgery.
    Frontiers in Cellular Neuroscience 08/2015; 1(9). DOI:10.3389/fncel.2015.00303 · 4.29 Impact Factor
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    • "Reduced levels of E-cadherin are balanced by increasing levels of N-cadherin, resulting in an overall weakening of cell–cell interactions (Wheelock et al., 2008). Rearrangements of the actin cytoskeleton, probably via moesin mediation (Haynes et al., 2011), activate a motile status of the cell (Thiery and Sleeman, 2006). "
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    ABSTRACT: Malignant pleural effusions (MPEs) are a common manifestation found in patients with lung cancer. After cytological and histological confirmation of malignancy, talc pleurodesis still remains the treatment of choice in patients with MPEs resistant to chemotherapy. Despite this, primary challenges include reduced quality of life and life expectancy in general. Therefore, a better understanding of the cell biology of MPEs, along with improvements in treatment is greatly needed. It has recently been demonstrated that malignant pleural effusions (MPEs) may represent an excellent source for identification of molecular mechanisms within the tumor and its environment. The present review summarizes the current understanding of MPEs cells and tumor microenvironment, and particularly focuses on dissecting the cross-talk between MPEs and epithelial to mesenchymal transition (EMT), inflammation and cancer stem cells. J. Cell. Physiol. © 2014 Wiley Periodicals, Inc.
    Journal of Cellular Physiology 02/2015; 230(2). DOI:10.1002/jcp.24806 · 3.84 Impact Factor
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    • "However, in the basal region there was an increased prominence of stress fibers (Figure 2b) suggesting that basal contractility and traction forces (driven by Rho signalling) might be potentiated. Similar thickening and lengthening of actin stress fibres have been observed in mouse mammary epithelial, NMuMG cells following TGF-β induced EMT [39]. Associated transcriptional changes in the E-cadherin-deficient cells, included upregulation of RhoA, RhoB and RhoC, although their downstream effectors ROCK1 and ROCK2 were downregulated. "
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    ABSTRACT: E-cadherin is an adherens junction protein that forms homophilic intercellular contacts in epithelial cells while also interacting with the intracellular cytoskeletal networks. It has roles including establishment and maintenance of cell polarity, differentiation, migration and signalling in cell proliferation pathways. Its downregulation is commonly observed in epithelial tumours and is a hallmark of the epithelial to mesenchymal transition (EMT). To improve our understanding of how E-cadherin loss contributes to tumorigenicity, we investigated the impact of its elimination from the non-tumorigenic breast cell line MCF10A. We performed cell-based assays and whole genome RNAseq to characterize an isogenic MCF10A cell line that is devoid of CDH1 expression due to an engineered homozygous 4 bp deletion in CDH1 exon 11. The E-cadherin-deficient line, MCF10A CDH1-/- showed subtle morphological changes, weaker cell-substrate adhesion, delayed migration, but retained cell-cell contact, contact growth inhibition and anchorage-dependent growth. Within the cytoskeleton, the apical microtubule network in the CDH1-deficient cells lacked the radial pattern of organization present in the MCF10A cells and F-actin formed thicker, more numerous stress fibres in the basal part of the cell. Whole genome RNAseq identified compensatory changes in the genes involved in cell-cell adhesion while genes involved in cell-substrate adhesion, notably ITGA1, COL8A1, COL4A2 and COL12A1, were significantly downregulated. Key EMT markers including CDH2, FN1, VIM and VTN were not upregulated although increased expression of proteolytic matrix metalloprotease and kallikrein genes was observed. Overall, our results demonstrated that E-cadherin loss alone was insufficient to induce an EMT or enhance transforming potential in the non-tumorigenic MCF10A cells but was associated with broad transcriptional changes associated with tissue remodelling.
    BMC Cancer 07/2014; 14(1):552. DOI:10.1186/1471-2407-14-552 · 3.36 Impact Factor
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