The vinculin binding sites of talin and alpha-actinin are sufficient to activate vinculin.
ABSTRACT Vinculin regulates both cell-cell and cell-matrix junctions and anchors adhesion complexes to the actin cytoskeleton through its interactions with the vinculin binding sites of alpha-actinin or talin. Activation of vinculin requires a severing of the intramolecular interactions between its N- and C-terminal domains, which is necessary for vinculin to bind to F-actin; yet how this occurs in cells is not resolved. We tested the hypothesis that talin and alpha-actinin activate vinculin through their vinculin binding sites. Indeed, we show that these vinculin binding sites have a high affinity for full-length vinculin, are sufficient to sever the head-tail interactions of vinculin, and they induce conformational changes that allow vinculin to bind to F-actin. Finally, microinjection of these vinculin binding sites specifically targets vinculin in cells, disrupting its interactions with talin and alpha-actinin and disassembling focal adhesions. In their native (inactive) states the vinculin binding sites of talin and alpha-actinin are buried within helical bundles present in their central rod domains. Collectively, these results support a model where the engagement of adhesion receptors first activates talin or alpha-actinin, by provoking structural changes that allow their vinculin binding sites to swing out, which are then sufficient to bind to and activate vinculin.
Article: Vinculin Regulates the Recruitment and Release of Core Focal Adhesion Proteins in a Force-Dependent Manner.[show abstract] [hide abstract]
ABSTRACT: BACKGROUND: Cells sense the extracellular environment using adhesion receptors (integrins) linked to the intracellular actin cytoskeleton through a complex network of regulatory proteins that, all together, form focal adhesions (FAs). The molecular basis of how these sensing units are regulated, how they are implicated in transducing mechanical stimuli, and how this leads to a spatiotemporal coordination of FAs is unclear. RESULTS: Here we show that vinculin, through its links to the talin-integrin complex and F-actin, regulates the transmission of mechanical signals from the extracellular matrix to the actomyosin machinery. We demonstrate that the vinculin interaction with the talin-integrin complex drives the recruitment and release of core FA components. The activation state of vinculin is itself regulated by force, as underscored by our observation that vinculin localization to FAs is dependent on actomyosin contraction. Using a variety of vinculin mutants, we establish which components of the cell-matrix adhesion network are coordinated through direct and indirect associations with vinculin. Moreover, using cyclic stretching, we demonstrate that vinculin plays a key role in the transmission of extracellular mechanical stimuli leading to the reorganization of cell polarity. Of particular importance is the actin-binding tail region of vinculin, without which the cell's ability to repolarize in response to cyclic stretching is perturbed. CONCLUSIONS: Overall our data promote a model whereby vinculin controls the transmission of intracellular and extracellular mechanical cues that are important for the spatiotemporal assembly, disassembly, and reorganization of FAs to coordinate polarized cell motility.Current Biology 01/2013; · 9.65 Impact Factor
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ABSTRACT: Dental implants are a suitable option for the replacement of some or all missing teeth. Their main function is to secure the stability of the artificial tooth. The implant material interacts with several cell types including osteoblasts, gingival fibroblasts, periodontal ligament fibroblasts and monocytes. The most common material used is pure titanium which is corrosion resistant and has an elasticity modulus similar to that of bone. In recent years, diverse modified titanium surfaces have also been developed. The wound healing around the implant is a complex process that determines how well the host can heal and accept the implanted material. For this reason, search for markers of the biocompatibility of these new materials is paramount. To identify markers found to be suitable for studying the biocompatibility of dental implants. Review of Pubmed and Web of Science databases for the years 1958-2010. The surface of dental implant material should enhance firm attachment of the implant to junctional epithelium, soft connective tissue and bone. For the purposes of dental implant biocompatibility studies, a number of markers produced by osteoblasts or by cells of periodontal ligament have been proposed. In general, the most typical markers for osteoblasts and fibroblasts are alkaline phosphatase and collagen I, respectively. The involvement of both cell types in the inflammatory response is primarily evaluated by determination of tumour necrosis factor α and proinflammatory interleukins.Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia 06/2011; 155(2):109-16.
Article: Myosin II activity dependent and independent vinculin recruitment to the sites of E-cadherin-mediated cell-cell adhesion.[show abstract] [hide abstract]
ABSTRACT: Maintaining proper adhesion between neighboring cells depends on the ability of cells to mechanically respond to tension at cell-cell junctions through the actin cytoskeleton. Thus, identifying the molecules involved in responding to cell tension would provide insight into the maintenance, regulation, and breakdown of cell-cell junctions during various biological processes. Vinculin, an actin-binding protein that associates with the cadherin complex, is recruited to cell-cell contacts under increased tension in a myosin II-dependent manner. However, the precise role of vinculin at force-bearing cell-cell junctions and how myosin II activity alters the recruitment of vinculin at quiescent cell-cell contacts have not been demonstrated. We generated vinculin knockdown cells using shRNA specific to vinculin and MDCK epithelial cells. These vinculin-deficient MDCK cells form smaller cell clusters in a suspension than wild-type cells. In wound healing assays, GFP-vinculin accumulated at cell-cell junctions along the wound edge while vinculin-deficient cells displayed a slower wound closure rate compared to vinculin-expressing cells. In the presence of blebbistatin (myosin II inhibitor), vinculin localization at quiescent cell-cell contacts was unaffected while in the presence of jasplakinolide (F-actin stabilizer), vinculin recruitment increased in mature MDCK cell monolayers. These results demonstrate that vinculin plays an active role at adherens junctions under increased tension at cell-cell contacts where vinculin recruitment occurs in a myosin II activity-dependent manner, whereas vinculin recruitment to the quiescent cell-cell junctions depends on F-actin stabilization.BMC Cell Biology 11/2011; 12:48. · 2.59 Impact Factor