Integrin-β5 and zyxin mediate formation of ventral stress fibers in response to transforming growth factor β

Abstract

Cell adhesion to the extracellular matrix is an essential element of various biological processes. TGF-β cytokines regulate the matrix components and cell-matrix adhesions. The present study investigates the molecular organization of TGF-β-induced matrix adhesions. The study demonstrates that in various mouse and human epithelial cells TGF-β induces cellular structures containing 2 matrix adhesions bridged by a stretch of actin fibers. These structures are similar to ventral stress fibers (VSFs). Suppression of integrin-β5 by RNA interference reduces VSFs in majority of cells (> 75%), while overexpression of integrin-β5 fragments revealed a critical role of a distinct sequence in the cytoplasmic domain of integrin-β5 in the VSF structures. In addition, the integrity of actin fibers and Src kinase activity contribute to integrin-β5-mediated signaling and VSF formation. TGF-β-Smad signaling upregulates actin-regulatory proteins, such as caldesmon, zyxin, and zyxin-binding protein Csrp1 in mouse and human epithelial cells. Suppression of zyxin markedly inhibits formation of VSFs in response to TGF-β and integrin-β5. Zyxin is localized at actin fibers and matrix adhesions of VSFs and might bridge integrin-β5-mediated adhesions to actin fibers. These findings provide a platform for defining the molecular mechanism regulating the organization and activities of VSFs in response to TGF-β.

Integrin-mediated traction force enhances paxillin molecular associations and adhesion dynamics that increase the invasiveness of tumor cells into a three-dimensional extracellular matrix

“…Paxillin phosphorylation is mediated predominantly by Src family kinases (Schaller, 2001), and our Bio-ID assay revealed that GIT2, a Src substrate, was enriched proximal to paxillin in TGFβ-treated MCF10A MECs (enrichment factor, ∼4; Yu et al. , 2009, 2010; Bianchi-Smiraglia et al. , 2013; Figure 8b).…”

HECTD1 controls the protein level of IQGAP1 to regulate the dynamics of adhesive structures

“…For instance, paxillin is normally binds to ɑ 5 β 1 , ɑ 4 β 1 , ɑ 5 β 3 and ɑ 4 β 3 integrins [46–49], while zyxin binds to the integrin subtypes ɑ 5 β 1 and ɑ 5 β 5 [50, 51]. Besides, the integrin motifs expressed in different cell types may vary considerably.…”

Cytoskeletal signaling in TGFβ‐induced epithelial–mesenchymal transition

“…These data suggest an important role for tropomyosin in the regulation of TGFβ‐induced cell migration. A recent study has also found that depletion of caldesmon does not impact cell adhesion to fibronectin or the formation of ventral stress fibers during TGFβ‐induced EMT in mammary epithelial cells [Bianchi‐Smiraglia et al, ]. Further experiments are necessary to elucidate the impact of caldesmon expression on other aspects of TGFβ‐induced EMT.…”

“…Zyxin localizes to focal adhesion sites and to stress fibers in response to mechanical cues and has been shown to regulate actin polymerization, generation of traction force, cell movement, and signal transduction [Beckerle, 1998;Kadrmas and Beckerle, 2004]. TGFb promotes the upregulation of zyxin in normal mammary epithelial cells and zyxin expression mediates actin reorganization and the formation of ventral stress fibers [Mori et al, 2009;Bianchi-Smiraglia et al, 2013;Diepenbruck et al, 2014]. During TGFbinduced EMT, zyxin expression is regulated by the transcription factor Twist1 [Mori et al, 2009] and by the canonical Smad pathway [Bianchi-Smiraglia et al, 2013].…”

“…TGFb promotes the upregulation of zyxin in normal mammary epithelial cells and zyxin expression mediates actin reorganization and the formation of ventral stress fibers [Mori et al, 2009;Bianchi-Smiraglia et al, 2013;Diepenbruck et al, 2014]. During TGFbinduced EMT, zyxin expression is regulated by the transcription factor Twist1 [Mori et al, 2009] and by the canonical Smad pathway [Bianchi-Smiraglia et al, 2013]. Zyxin also contributes to the migratory phenotype attained by cells during EMT, as downregulation of zyxin attenuates cell migration and invasion [Diepenbruck et al, 2014;Mori et al, 2009].…”