Plakoglobin regulates cell motility through Rho- and fibronectin-dependent Src signaling

Abstract

SummaryWe previously showed that the cell-cell junction protein plakoglobin (PG) not only suppresses motility of keratinocytes in contact with each other, but also, unexpectedly, of single cells. Here keratinocytes. PG -/-cells also exhibited Src-independent activation of the small GTPases Rac1 and RhoA. Both Src and RhoA inhibition attenuated PG -/-keratinocyte motility. We propose a novel role for PG in regulating cell motility through distinct ECM-Src and RhoGTPase-dependent pathways, influenced in part by PG-dependent regulation of FN mRNA stability. Key words: Armadillo protein, Desmosome, Extracellular matrix, KeratinocyteJournal of Cell Science (Caldelari et al., 2001) and adhesive strength (Acehan et al., 2008) in keratinocytes lacking PG. Moreover, PG-null mice and patients with pathogenic homozygous PG mutations have impaired tissue integrity associated with skin and heart defects (Aberle et al., 1995;Bierkamp et al., 1996;McKoy et al., 2000;Ruiz et al., 1996). PG is also found in the cytoplasm and nucleus (Green and Simpson, 2007;Schmidt and Koch, 2007), where it is able to act independently of its function in intercellular adhesion. Its adhesionindependent functions are still not well defined, but the data suggest that PG can regulate gene expression and protein stability (Aktary et al., 2010;Hakimelahi et al., 2000;Shimizu et al., 2008) in both a -catenin-dependent and -independent manner (Raurell et al., 2006;Teuliere et al., 2004;Yin and Green, 2004;Zhurinsky et al., 2000).Recently we demonstrated that PG not only inhibits motility of keratinocytes in contact, but also inhibits Src-dependent single cell motility (Yin et al., 2005b). The observed changes in motility and altered cell morphology of PG -/-keratinocytes suggested to us that PG could be regulating cell-substrate interactions by modulating components of the extracellular matrix (ECM), its integrin receptors and/or the molecules involved in ECM-triggered motility cues. Using a combination of live cell imaging and cross plating, we show here that PG expression has a potent impact on the organization of actin, its associated membrane protrusions, focal adhesions and Src-dependent motility, in large part through regulation of the expression levels of the underlying ECM components. In particular, the ability of PG to regulate fibronectin (FN; also know as Fn1) mRNA stability was identified as a novel mechanism contributing to PG-dependent suppression of keratinocyte motility. Further analysis indicated that PG-dependent alterations in activity of the small GTPases Rac1 and RhoA act in parallel with FN/Src-dependent regulation of cortical actin 3577 Plakoglobin regulates motility via ECM structures to fine tune the motile behavior of keratinocytes. Collectively, these results indicate that a desmosomal molecule, PG, is capable of regulating single cell motility through matrix deposition in concert with Rho GTPases, independently of its role as a cell-cell adhesion molecule. Results PG regulates keratinocyte cell polarity and single-cell ...

High Motility of Triple-negative Breast Cancer Cells Is Due to Repression of Plakoglobin Gene by Metastasis Modulator Protein SLUG

“…Out of several epithelial cell molecules implicated in the direct or indirect regulation of cellular motility, the catenin molecule plakoglobin stands out as a major player in negatively regulating the motility of these cells (17)(18)(19)(20)(21)(22)(23). Plakoglobin (also known as junction plakoglobin (JUP)) is a member of the armadillo family of proteins and a close relative of ␤-catenin (24).…”

“…Plakoglobin (also known as junction plakoglobin (JUP)) is a member of the armadillo family of proteins and a close relative of ␤-catenin (24). Plakoglobin comprises 12 central armadillo repeats, which are flanked by N-and C-terminal domains (17)(18)(19). By interacting with both the desmosomal cadherins and the N terminus of desmoplakin, plakoglobin is positioned to play a role in linking intermediate filaments to the desmosomal plaque (17)(18)(19).…”

“…Plakoglobin comprises 12 central armadillo repeats, which are flanked by N-and C-terminal domains (17)(18)(19). By interacting with both the desmosomal cadherins and the N terminus of desmoplakin, plakoglobin is positioned to play a role in linking intermediate filaments to the desmosomal plaque (17)(18)(19). Recent report indicates that plakoglobin not only inhibits motility of keratinocytes in contact but also inhibits Src-dependent single cell motility (17).…”

Expression of growth hormone receptor, plakoglobin and NEDD9 protein in association with tumour progression and metastasis in human breast cancer

“…through inhibition of the c-Myc gene expression [26] or indirectly, through regulation of tumour suppressor genes expression, including PML in renal cells [27] and modulation of the cytoskeleton and RhoGTPase signalization [28]. Indeed, several independent clinical examinations of plakoglobin expression patterns in primary breast carcinoma detected reduced expression of plakoglobin [23], [24], [29], [30].…”

“…Downregulation of plakoglobin expression detected in metastatic tissues in comparison with primary tumours from breast cancer patients indicates that plakoglobin might play a different role in metastatic lesions than in primary tumours [6]. Plakoglobin has a recognised role in controlling the motility of epithelial cells, where its high levels are associated with lower motility and vice versa [7,8]. More insights into how plakoglobin contributes to the aggressiveness of breast cancer cells were provided by Bailey et al [9], who showed that metastasis regulator protein SLUG represses plakoglobin gene expression in the triple negative (negative in the expression of estrogen, progesterone, and ERBB2 receptors) breast cancer cells resulting in their increased motility.…”