Function Of Vinculin Research Articles

Förster resonance energy transfer efficiency of the vinculin tension sensor in cultured primary cortical neuronal growth cones.

.Significance: Interaction of neurons with their extracellular environment and the mechanical forces at focal adhesions and synaptic junctions play important roles in neuronal development.Aim: To advance studies of mechanotransduction, we demonstrate the use of the vinculin tension sensor (VinTS) in primary cultures of cortical neurons. VinTS consists of TS module (TSMod), a Förster resonance energy transfer (FRET)-based tension sensor, inserted between vinculin’s head and tail. FRET efficiency decreases with increased tension across vinculin.Approach: Primary cortical neurons cultured on glass coverslips coated with poly-d-lysine and laminin were transfected with plasmids encoding untargeted TSMod, VinTS, or tail-less vinculinTS (VinTL) lacking the actin-binding domain. The neurons were imaged between day in vitro (DIV) 5 to 8. We detail the image processing steps for calculation of FRET efficiency and use this system to investigate the expression and FRET efficiency of VinTS in growth cones.Results: The distribution of fluorescent constructs was similar within growth cones at DIV 5 to 8. The mean FRET efficiency of TSMod () in growth cones was higher than the mean FRET efficiency of VinTS () and VinTL () (). While small, the difference between the FRET efficiency of VinTS and VinTL was statistically significant (), suggesting that vinculin is under low tension in growth cones. Two-hour treatment with the Rho-associated kinase inhibitor Y-27632 did not affect the mean FRET efficiency. Growth cones exhibited dynamic changes in morphology as observed by time-lapse imaging. VinTS FRET efficiency showed greater variance than TSMod FRET efficiency as a function of time, suggesting a greater dependence of VinTS FRET efficiency on growth cone dynamics compared with TSMod.Conclusions: The results demonstrate the feasibility of using VinTS to probe the function of vinculin in neuronal growth cones and provide a foundation for studies of mechanotransduction in neurons using this tension probe.

Substrate rigidity modulates traction forces and stoichiometry of cell-matrix adhesions.

In cell-matrix adhesions, integrin receptors and associated proteins provide a dynamic coupling of the extracellular matrix (ECM) to the cytoskeleton. This allows bidirectional transmission of forces between the ECM and the cytoskeleton, which tunes intracellular signaling cascades that control survival, proliferation, differentiation, and motility. The quantitative relationships between recruitment of distinct cell-matrix adhesion proteins and local cellular traction forces are not known. Here, we applied quantitative super-resolution microscopy to cell-matrix adhesions formed on fibronectin-stamped elastomeric pillars and developed an approach to relate the number of talin, vinculin, paxillin, and focal adhesion kinase (FAK) molecules to the local cellular traction force. We find that FAK recruitment does not show an association with traction-force application, whereas a ∼60 pN force increase is associated with the recruitment of one talin, two vinculin, and two paxillin molecules on a substrate with an effective stiffness of 47kPa. On a substrate with a fourfold lower effective stiffness, the stoichiometry of talin:vinculin:paxillin changes to 2:12:6 for the same ∼60 pN traction force. The relative change in force-related vinculin recruitment indicates a stiffness-dependent switch in vinculin function in cell-matrix adhesions. Our results reveal a substrate-stiffness-dependent modulation of the relationship between cellular traction-force and the molecular stoichiometry of cell-matrix adhesions.

Mechanical instability of adherens junctions overrides intrinsic quiescence of hair follicle stem cells.

Vinculin, a mechanotransducer associated with both adherens junctions (AJs) and focal adhesions (FAs), plays a central role in force transmission through cell-cell and cell-substratum contacts. We generated the conditional knockout (cKO) of vinculin in murine skin that results in the loss of bulge stem cell (BuSC) quiescence and promotes continual cycling of the hair follicles. Surprisingly, we find that the AJs in vinculin cKO cells are mechanically weak and impaired in force generation despite increased junctional expression of E-cadherin and α-catenin. Mechanistically, we demonstrate that vinculin functions by keeping α-catenin in a stretched/open conformation, which in turn regulates the retention of YAP1, another potent mechanotransducer and regulator of cell proliferation, at the AJs. Altogether, our data provide mechanistic insights into the hitherto-unexplored regulatory link between the mechanical stability of cell junctions and contact-inhibition-mediated maintenance of BuSC quiescence.

Vinculin Controls Endothelial Cell Junction Dynamics During Vascular Lumen Formation

Blood vessel morphogenesis is driven by coordinated endothelial cell behaviors, which depend on dynamic cell-cell interactions. Remodeling of endothelial cell-cell junctions promote morphogenetic cellular events while preserving vascular integrity. Here, we have analyzed the dynamics of endothelial cell-cell junctions during lumen formation in angiogenic sprouts. By live-imaging of the formation of intersegmental blood vessels in zebrafish, we demonstrate that lumen expansion is accompanied by the formation of transient finger-shaped junctions. Formation and maintenance of these junctional fingers are positively regulated by blood pressure whereas inhibition of blood flow prevents their formation. Using fluorescent reporters, we show that the tension-sensor Vinculin localizes to junctional fingers. Furthermore, loss of vinculin function, in vinculin a and -b double knockouts, prevents junctional finger formation in angiogenic sprouts, whereas endothelial expression of a vinculin transgene is sufficient to restore junctional fingers. Taken together, our findings suggest a mechanism in which lumen expansion during angiogenesis leads to an increase in junctional tension, which triggers recruitment of vinculin and formation of junctional fingers. We propose that endothelial cells may employ force-dependent junctional remodeling to react to changes in external forces to protect cell-cell contacts and to maintain vascular integrity during sprouting angiogenesis.

Mechanical Instability of Adherens Junctions Overrides Intrinsic Quiescence of Hair Follicle Stem Cells

Vinculin, a mechanotransducer associated with both adherens junctions (AJ) and focal adhesions (FA) plays a central role in force transmission through these cell-cell and cell-substratum contacts. The conditional knock out (KO) of vinculin in murine skin results in the loss of bulge stem cell (BuSC) quiescence and hair follicles that cycle continually. Remarkably, we find that the AJs in vinculin KO cells are mechanically weak and impaired in force generation despite increased expression of E-cadherin and α-catenin at the junctions. Mechanistically, vinculin functions by keeping α-catenin in a stretched/open conformation, which in turn regulates the retention of YAP1, another potent mechanotransducer and regulator of cell proliferation, to the junctions. Altogether, our data provides definitive mechanistic insights into the hitherto unexplored regulatory link between the mechanical stability of cell-junctions and the maintenance of BuSC quiescence via contact inhibition.

Nuclear function of vinculin in mouse primary oocytes

Nuclear function of vinculin in mouse primary oocytes

Role of PIP2-Dependent Membrane Interactions in Vinculin Activation, Motility and Force Transmission

Vinculin is an essential and abundant cytoskeletal protein localized to focal adhesions and cell-cell contacts, where it participates in the linkage of transmembrane receptors to the actin cytoskeleton to control cell survival and migration. Loss of vinculin results in increased cell migration, apoptotic resistance, and the acquisition of tumorigenic properties. Mutations in vinculin and its splice variant, metavinculin, are associated with cardiac disease. Vinculin consists of a head domain (Vh) and a tail domain (Vt) that form autoinhibitory interactions in its inactive state, but release upon activation, exposing phosphorylation, protein and phosphoinositol 4,5-bisphosphate (PIP2) binding sites. The interaction of vinculin with PIP2 is believed critical for its function, however, it is currently unclear how vinculin specifically recognizes PIP2 and regulates vinculin. Vt forms an antiparallel five-helix bundle with amino-terminal (NT) and carboxyl terminal (CT) extensions. While a crystal structure of an oligomerized Vt mutant complexed to a short chain PIP2 has recently been published (Chinthalapudi et al. (JCB, 2014)), the structure is incompatible with membrane insertion. We propose an alternative model using experimental data, molecular docking and dynamics simulations and provide validation of the model through biophysical and biochemical analyses. In our model, the PIP2 head group binds to the Vt basic collar, and promotes release of Vt's strap and CT to facilitate membrane insertion. The role of vinculin/PIP2 interaction in mediating vinculin activation, localization, cell migration, force sensing and transmission has also been characterized using cell microscopy, including super-resolution microscopy approaches, by examining WT and PIP2-deficient full length vinculin in knockout cells. Information derived from these analyses will result in an unprecedented understanding of vinculin function from the molecular to the cellular level and will enable us to build more comprehensive models of vinculin membrane interactions.

Vinculin b deficiency causes epicardial hyperplasia and coronary vessel disorganization in zebrafish

Coronary vessel development is a highly coordinated process during heart formation. Abnormal development and dysfunction of the coronary network are contributory factors in the majority of heart disease. Understanding the molecular mechanisms that regulate coronary vessel formation is crucial for preventing and treating the disease. We report a zebrafish gene-trap vinculin b (vclb) mutant that displays abnormal coronary vessel development among multiple cardiac defects. The mutant shows overproliferation of epicardium-derived cells and disorganization of coronary vessels, and they eventually die off at juvenile stages. Mechanistically, Vclb deficiency results in the release of another cytoskeletal protein, paxillin, from the Vclb complex and the upregulation of ERK and FAK phosphorylation in epicardium and endocardium, causing disorganization of endothelial cells and pericytes during coronary vessel development. By contrast, cardiac muscle development is relatively normal, probably owing to redundancy with Vcla, a vinculin paralog that is expressed in the myocardium but not epicardium. Together, our results reveal a previously unappreciated function of vinculin in epicardium and endocardium and reinforce the notion that well-balanced FAK activity is essential for coronary vessel development.

Evidence for the mechanosensor function of filamin in tissue development.

Cells integrate mechanical properties of their surroundings to form multicellular, three-dimensional tissues of appropriate size and spatial organisation. Actin cytoskeleton-linked proteins such as talin, vinculin and filamin function as mechanosensors in cells, but it has yet to be tested whether the mechanosensitivity is important for their function in intact tissues. Here we tested, how filamin mechanosensing contributes to oogenesis in Drosophila. Mutations that require more or less force to open the mechanosensor region demonstrate that filamin mechanosensitivity is important for the maturation of actin-rich ring canals that are essential for Drosophila egg development. The open mutant was more tightly bound to the ring canal structure while the closed mutant dissociated more frequently. Thus, our results show that an appropriate level of mechanical sensitivity is required for filamins’ function and dynamics during Drosophila egg growth and support the structure-based model in which the opening and closing of the mechanosensor region regulates filamin binding to cellular components.

Role of PIP2-Dependent Membrane Interactions in Vinculin Activation, Motility and Force Transmission

Vinculin is an essential and abundant cytoskeletal protein localized to focal adhesions and cell-cell contacts, where it participates in the linkage of transmembrane receptors to the actin cytoskeleton to control cell survival and migration. Loss of vinculin results in increased cell migration, apoptotic resistance, and the acquisition of tumorigenic properties. Mutations in vinculin and its splice variant, metavinculin, are associated with cardiac disease. Vinculin consists of a head domain (Vh) and a tail domain (Vt) that form autoinhibitory interactions in its inactive state, but release upon activation, exposing phosphorylation, protein and phosphoinositol 4,5-bisphosphate (PIP2) binding sites. The interaction of vinculin with PIP2 is believed critical for its function, however, it is currently unclear how vinculin specifically recognizes PIP2 and regulates vinculin. Vt forms an antiparallel five-helix bundle with amino-terminal (NT) and carboxyl terminal (CT) extensions. While a crystal structure of an oligomerized Vt mutant complexed to a short chain PIP2 has recently been published (Chinthalapudi et al. (JCB, 2014)), the structure is incompatible with membrane insertion. We propose an alternative model using experimental data, molecular docking and dynamics simulations and provide validation of the model through biophysical and biochemical analyses. In our model, the PIP2 head group binds to the Vt basic collar, and promotes release of Vt's strap and CT to facilitate membrane insertion. The role of vinculin/PIP2 interaction in mediating vinculin activation, localization, cell migration, force sensing and transmission has also been characterized using cell microscopy, including super-resolution microscopy approaches, by examining WT and PIP2-deficient full length vinculin in knockout cells. Information derived from these analyses will result in an unprecedented understanding of vinculin function from the molecular to the cellular level and will enable us to build more comprehensive models of vinculin membrane interactions.

Vinculin b deficiency causes epicardial hyperplasia and coronary vessel disorganization in zebrafish.

Coronary vessel development is a highly coordinated process during heart formation. Abnormal development and dysfunction of the coronary network are contributory factors in the majority of heart disease. Understanding the molecular mechanisms that regulate coronary vessel formation is crucial for preventing and treating the disease. We report a zebrafish gene-trap vinculin b (vclb) mutant that displays abnormal coronary vessel development among multiple cardiac defects. The mutant shows overproliferation of epicardium-derived cells and disorganization of coronary vessels, and they eventually die off at juvenile stages. Mechanistically, Vclb deficiency results in the release of another cytoskeletal protein, paxillin, from the Vclb complex and the upregulation of ERK and FAK phosphorylation in epicardium and endocardium, causing disorganization of endothelial cells and pericytes during coronary vessel development. By contrast, cardiac muscle development is relatively normal, probably owing to redundancy with Vcla, a vinculin paralog that is expressed in the myocardium but not epicardium. Together, our results reveal a previously unappreciated function of vinculin in epicardium and endocardium and reinforce the notion that well-balanced FAK activity is essential for coronary vessel development.

Molecular mechanism of vinculin activation and nanoscale spatial organization in focal adhesions.

Focal adhesions (FAs) link the extracellular matrix (ECM) to the actin cytoskeleton to mediate cell adhesion, migration, mechanosensing and signaling. FAs have conserved nanoscale protein organization, suggesting that the position of proteins within FAs regulates their activity and function. Vinculin binds different FA proteins to mediate distinct cellular functions, but how vinculin’s interactions are spatiotemporally organized within FA is unknown. Using interferometric photo-activation localization (iPALM) super-resolution microscopy to assay vinculin nanoscale localization and a FRET biosensor to assay vinculin conformation, we found that upward repositioning within the FA during FA maturation facilitates vinculin activation and mechanical reinforcement of FA. Inactive vinculin localizes to the lower integrin signaling layer in FA by binding to phospho-paxillin. Talin binding activates vinculin and targets active vinculin higher in FA where vinculin can engage retrograde actin flow. Thus, specific protein interactions are spatially segregated within FA at the nano-scale to regulate vinculin activation and function.

New Models for Regulation of Vinculin by Actin and Phospholipids

Vinculin is an essential cytoskeletal protein that is a prominent component of focal adhesions and adherens junctions. It exists in an autoinhibited conformation that masks interactions of ligands with the head (Vh) and tail (Vt) domain. Upon activation, vinculin functions as a scaffold to regulate cellular events resulting in cell migration, cell survival and embryogenesis. Vinculin null cells display tumorigenic properties and mutation or loss of vinculin is associated with cardiac disease. The interaction between vinculin and actin plays a pivotal role in linking transmembrane receptors to the cytoskeleton, which, in turn, is important for controlling cellular cell morphology, force transmission and motility. Binding of F-actin to Vt causes a conformational change that induces formation of a cryptic dimer necessary for actin filament bundling, however, the conformational change that occurs and dimer that is formed is unknown. It is also unclear how vinculin recognizes PIP2, inserts into membranes and is regulated by this interaction. We have now obtained a sub-nanometer resolution reconstruction of the Vt/actin complex which sheds light on actin-induced conformational changes necessary for vinculin dimerization and actin filament bundling, and have integrated computational and experimental approaches to generate and test models for the actin-induced vinculin dimer and vinculin/PIP2 membrane interaction and assess their significance in vinculin function both in vitro and in cells.

Loss of vinculin and membrane-bound β-catenin promotes metastasis and predicts poor prognosis in colorectal cancer.

BackgroundLoss of cell-cell adhesion is important for the development of cancer invasion and metastasis. Vinculin, a key adhesion-related protein, can affect metastasis and prognosis in several tumours. Here, we determined the biological roles of vinculin in the metastasis of colorectal cancer (CRC) and evaluated its clinical significance as a potential disease biomarker.MethodsThe expression level of vinculin in CRC cell lines and tissues was measured using Real-Time PCR and western blotting. Moreover, vinculin function was analysed using Transwell assays and in vivo metastasis assays in gain- and loss-of-function experiments. Furthermore, the impact of vinculin together with membrane-bound β-catenin on the prognosis of 228 CRC patients was investigated by immunohistochemistry. Additionally, the expression of epithelial-mesenchymal transition (EMT) indicators was verified by immunohistochemistry in CRC tissues obtained from these patients.ResultVinculin expression was found to be significantly downregulated in highly metastatic CRC cell lines and metastatic tissues. Both in vitro and in vivo experiments showed that vinculin suppressed invasion, migration and metastasis in CRC cells and that this suppression could be attenuated by silencing β-catenin. Moreover, the expression of vinculin and membrane-bound β-catenin were positively correlated in CRC tissues, and lack of vinculin expression emerged as an independent prognostic factor in patients with CRC. Finally, the loss of vinculin and membrane-bound β-catenin was associated with node metastasis, organ metastasis and expression of EMT indicators.ConclusionOur results suggest that vinculin may play specific roles in the EMT and metastasis of CRC and that loss of vinculin could be used as a prognostic factor for CRC.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-263) contains supplementary material, which is available to authorized users.

Vinculin phosphorylation differentially regulates mechanotransduction at cell-cell and cell-matrix adhesions.

Cells experience mechanical forces throughout their lifetimes. Vinculin is critical for transmitting these forces, yet how it achieves its distinct functions at cell-cell and cell-matrix adhesions remains unanswered. Here, we show vinculin is phosphorylated at Y822 in cell-cell, but not cell-matrix, adhesions. Phosphorylation at Y822 was elevated when forces were applied to E-cadherin and was required for vinculin to integrate into the cadherin complex. The mutation Y822F ablated these activities and prevented cells from stiffening in response to forces on E-cadherin. In contrast, Y822 phosphorylation was not required for vinculin functions in cell-matrix adhesions, including integrin-induced cell stiffening. Finally, forces applied to E-cadherin activated Abelson (Abl) tyrosine kinase to phosphorylate vinculin; Abl inhibition mimicked the loss of vinculin phosphorylation. These data reveal an unexpected regulatory mechanism in which vinculin Y822 phosphorylation determines whether cadherins transmit force and provides a paradigm for how a shared component of adhesions can produce biologically distinct functions.

Vinculin Phosphorylation at Tyr1065 Regulates Vinculin Conformation and Tension Development in Airway Smooth Muscle Tissues

Vinculin localizes to membrane adhesion junctions in smooth muscle tissues, where its head domain binds to talin and its tail domain binds to filamentous actin, thus linking actin filaments to the extracellular matrix. Vinculin can assume a closed conformation, in which the head and tail domains bind to each other and mask the binding sites for actin and talin, and an open activated conformation that exposes the binding sites for talin and actin. Acetylcholine stimulation of tracheal smooth muscle tissues induces the recruitment of vinculin to the cell membrane and its interaction with talin and actin, which is required for active tension development. Vinculin phosphorylation at Tyr(1065) on its C terminus increases concurrently with tension development in tracheal smooth muscle tissues. In the present study, the role of vinculin phosphorylation at Tyr(1065) in regulating the conformation and function of vinculin during airway smooth muscle contraction was evaluated. Vinculin constructs with point mutations at Tyr(1065) (vinculin Y1065F and vinculin Y1065E) and vinculin conformation-sensitive FRET probes were expressed in smooth muscle tissues to determine how Tyr(1065) phosphorylation affects smooth muscle contraction and the conformation and cellular functions of vinculin. The results show that vinculin phosphorylation at tyrosine 1065 is required for normal tension generation in airway smooth muscle during contractile stimulation and that Tyr(1065) phosphorylation regulates the conformation and scaffolding activity of the vinculin molecule. We conclude that the phosphorylation of vinculin at tyrosine 1065 provides a mechanism for regulating the function of vinculin in airway smooth muscle in response to contractile stimulation.

Deletion of the cell adhesion adaptor protein vinculin disturbs the localization of GFAP in Bergmann glial cells

Astrocytes operate in close spatial relationship to other cells including neurons. Structural interaction is controlled by a dynamic interplay between actin-based cell motility and contact formation via cell-cell and cell-extracellular matrix adhesions. A central player in the control of cell adhesion is the cytoskeletal adaptor protein Vinculin. Incorporation of Vinculin affects mechanical properties and turnover of cell adhesion sites. To study the in vivo function of Vinculin in astrocytes, a mouse line with astrocyte specific and inducible deletion of vinculin was generated. Deletion of vinculin decreased the expression of the glial acidic fibrillary protein (GFAP) in Bergmann glial cells in the cerebellum. In addition, localization of GFAP to Bergmann glial endfeet was disturbed, indicating a role for vinculin in controlling its expression and localization. In contrast, vimentin expression, morphology, activation state and polarity of the targeted cells as well as the localization of the extracellular matrix protein laminin was not compromised. Furthermore, stab wound lesions were performed in the cerebellar cortex. In both wildtype and vinculin knockout mice GFAP expression was upregulated in Bergmann glial cells of the lesioned area with no differences observed between genotypes in expression and localization of GFAP. These results propose a selective requirement for vinculin in cellular events related to cell adhesion in vivo. As in vitro data suggested a major role for vinculin in the control of the cytoskeletal connection affecting mechanical stability and cell motility, our data add a note of caution to the extrapolation of in vitro data to in vivo function.

The C-terminal tail domain of metavinculin, vinculin’s splice variant, severs actin filaments

Vinculin and its splice variant, metavinculin (MV), are key elements of multiple protein assemblies linking the extracellular matrix to the actin cytoskeleton. Vinculin is expressed ubiquitously, whereas MV is mainly expressed in smooth and cardiac muscle tissue. The only difference in amino acid sequence between the isoforms is a 68-residue insert in the C-terminal tail domain of MV (MVt). Although the functional role of this insert remains elusive, its importance is exemplified by point mutations that are associated with dilated and hypertrophic cardiomyopathy. In vinculin, the actin binding site resides in the tail domain. In this paper, we show that MVt binds actin filaments similarly to the vinculin tail domain. Unlike its splice variant, MVt did not bundle actin filaments. Instead, MVt promoted severing of actin filaments, most efficiently at substoichiometric concentrations. This surprising and seemingly contradictory alteration of vinculin function by the 68-residue insert may be essential for modulating compliance of vinculin-induced actin bundles when exposed to rapidly increasing external forces.

Vinculin Functions as Regulator of Chondrogenesis

To identify the genes involved in chondrocytic differentiation, we applied gene trap mutagenesis to a murine mesenchymal chondrogenic cell line ATDC5 and isolated a clone in which the gene encoding vinculin was trapped. The trapped allele was assumed to express a fusion protein containing a truncated vinculin lacking the tail domain and the geo product derived from the trap vector. The truncated vinculin was suggested to exert a dominant negative effect. Impaired functioning of vinculin caused by gene trapping in ATDC5 cells or knockdown in primary chondrocytes resulted in the reduced expression of chondrocyte-specific genes, including Col2a1, aggrecan, and Col10a1. The expression of Runx2 also was suppressed by the dysfunctional vinculin. On the other hand, the expression of Sox9, encoding a key transcription factor for chondrogenesis, was retained. Knockdown of vinculin in metatarsal organ cultures impaired the growth of the explants and reduced the expression of Col2a1 and aggrecan. Gene trapping or knockdown of vinculin decreased the phosphorylation of ERK1/2 but increased that of Src homology 2 domain-containing tyrosine phosphatase 2 (SHP2) and Akt during chondrocytic differentiation, suggesting a disturbance of signaling by insulin-like growth factor I (IGF-I). Knockdown of vinculin in the metatarsal organ culture abrogated the IGF-I-induced growth and inhibited the up-regulation of Col2a1 and aggrecan expression by IGF-I. Loss of vinculin function in differentiating chondrocytes impaired the activation of the p38 MAPK pathway also, suggesting its involvement in the regulation of chondrogenesis by vinculin. Our results indicate a tissue-specific function of vinculin in cartilage whereby it controls chondrocytic differentiation.

Cell–cell and cell–matrix interactions

Molecular Biology of the CellVol. 23, No. 6 ASCB Annual Meeting HighlightsFree AccessCell–cell and cell–matrix interactionsKris A. DeMali, and Josephine C. AdamsKris A. DeMaliDepartment of Biochemistry, University of Iowa, Iowa City, IA 52242-1109Search for more papers by this author, and Josephine C. AdamsSchool of Biochemistry, University of Bristol, Bristol BS8 1TD, United KingdomSearch for more papers by this authorPublished Online:13 Oct 2017https://doi.org/10.1091/mbc.e11-12-0967AboutSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cell–cell and cell–extracellular matrix (ECM) interactions are fundamental to the complexity of multicellularity achieved in the metazoa. These interactions share many conceptual similarities, the most prominent being a dependence on transmembrane adhesion receptors, binding of adhesion receptors to specific extracellular ligand partners, and the linkage of receptor cytoplasmic domains to intracellular cytoskeletal systems via protein complexes. In both cases, these protein complexes also integrate intracellular signaling, cytoskeletal organization, and regulation of multiple cellular functions.The 2011 Minisymposium on Cell–Cell and Cell–Matrix Interactions brought together current topics and model systems within this broad area of cell biology.Molecular mechanisms that coordinate assembly and function of cell–cell and cell–ECM adhesionsTwo presentations addressed how integrin- and cadherin-dependent adhesions intersect. Kris DeMali (University of Iowa) showed that the function of vinculin, a shared cytoplasmic component of both adhesions, is differentially regulated in cell–cell and cell–ECM adhesions. Data were presented showing that ablation of a single tyrosine residue in vinculin resulted in opposite effects on cell–cell and cell–ECM adhesions. Fangliang Zhang from Anna Kashina's laboratory (University of Pennsylvania) presented his research on talin, a protein that historically has been thought to be present only in integrin-based adhesions as a proximal mediator of integrin activation and of focal adhesion assembly in integrin outside–in signaling. Data were presented on a novel proteolytic processing of talin that is associated with its recruitment and function in cadherin-mediated adhesions.Roles of cell protrusions as initial and dynamic mediators of cell–cell and cell–ECM interactionsFilopodia have well-established roles in sampling the local environment and making initial cell–ECM contacts at the leading edge of many cell types. Filopodial-like structures, termed “epithelial zippers,” can mediate initial contacts between epithelial cells that culminate in assembly of cell–cell junctions. However, the molecular composition of these structures and their relationship to filopodia has remained unclear. Katy Liu from Richard Cheney's laboratory (University of North Carolina at Chapel Hill) showed localization of myosin-X in initial, filopodial contacts between epithelial cells. Whereas myosin-X has a known role in filopodial assembly, the data presented revealed additional important functions in assembly of cell–cell junctions and epithelial morphogenesis. Brad Davidson (University of Arizona) presented data from Ciona intestinalis embryos, a tractable system for the analysis of cell specification in an intact organism (Cooley et al., 2011). Specification of precardiac cells is directed by polarized, invasive filopodial protrusions that localize their response to an ungraded signal.Cell–ECM mechanisms that modulate cell motilitySyndecan-4 is a transmembrane proteoglycan that functions in cell–ECM interactions through its glycosaminoglycan side chains and by activating intracellular signaling that reinforces integrin-dependent focal adhesion assembly (Couchman, 2010). John Couchman (University of Copenhagen, Denmark) presented data on a new role for syndecan-4 in the protrusive invadopodia of breast carcinoma cells that regulate invasive behavior. Jo Adams (University of Bristol, United Kingdom) described recent phylogenetic studies that show components of the ECM (unlike integrins and cadherins) to be specific to the metazoa (Ozbek et al., 2010). Among the most conserved ECM components are the thrombospondins, which participate in ECM homeostasis and remodeling processes. ECM accumulation of thrombospondin-1 facilitates migration of multiple cell types. Data were presented on l-lectin domain-dependent mechanisms that mediate ECM accumulation of thrombospondins.FOOTNOTESDOI: 10.1091/mbc.E11-12-0967REFERENCES Cooley J, Whitaker S, Sweeney S, Fraser S, Davidson B (2011). Cytoskeletal polarity mediates localized induction of the heart progenitor lineage. Nat Cell Biol 13, 952-957. Crossref, Medline, Google Scholar Couchman JR (2010). Transmembrane signaling proteoglycans. Annu Rev Cell Dev Biol 26, 89-114. Crossref, Medline, Google Scholar Ozbek S, Balasubramanian PG, Chiquet-Ehrismann R, Tucker RP, Adams JC (2010). The evolution of extracellular matrix. Mol Biol Cell 21, 4300-4305. Link, Google ScholarFiguresReferencesRelatedDetailsCited byMorphological and Functional Remodeling of Vascular Endothelium in Cardiovascular Diseases19 January 2023 | International Journal of Molecular Sciences, Vol. 24, No. 3Cardiac Patch-Based Therapies of Ischemic Heart Injuries30 June 2019 Vol. 23, No. 6 March 15, 2012965-1140 Metrics Downloads & Citations Downloads: 195Citations: 2 History Information© 2012 DeMali and Adams. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).PDF download