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39-459: 7414 22330 ENSG00000035403 ENSMUSG00000021823 P18206 Q64727 NM_003373 NM_014000 NM_009502 NP_003364 NP_054706 NP_033528 In mammalian cells, vinculin is a membrane-cytoskeletal protein in focal adhesion plaques that is involved in linkage of integrin adhesion molecules to the actin cytoskeleton . Vinculin is a cytoskeletal protein associated with cell-cell and cell-matrix junctions, where it

78-517: A splice variant carrying an extra exon in the 3' coding region, thus encoding a longer isoform meta-vinculin (meta VCL) of ~150KD molecular weight — a protein whose existence has been known since the 1980s. Translation of the extra exon causes a 68- to 79-amino acid acid-rich insert between helices I and II within the C-terminal tail domain. Mutations within the insert region correlate with hereditary idiopathic dilated cardiomyopathy . The length of

117-535: A cell in response to ECM adhesion. Focal adhesions serve as the mechanical linkages to the ECM, and as a biochemical signaling hub to concentrate and direct numerous signaling proteins at sites of integrin binding and clustering. Focal adhesions are integrin-containing, multi-protein structures that form mechanical links between intracellular actin bundles and the extracellular substrate in many cell types. Focal adhesions are large, dynamic protein complexes through which

156-433: A central role in cell migration . During cell migration, both the composition and the morphology of the focal adhesion change. Initially, small (0.25μm ) focal adhesions called focal complexes (FXs) are formed at the leading edge of the cell in lamellipodia : they consist of integrin, and some of the adapter proteins, such as talin , paxillin and tensin . Many of these focal complexes fail to mature and are disassembled as

195-428: A considerable functional diversity. More than anchoring the cell, they function as signal carriers (sensors), which inform the cell about the condition of the ECM and thus affect their behavior. In sessile cells, focal adhesions are quite stable under normal conditions, while in moving cells their stability is diminished: this is because in motile cells, focal adhesions are being constantly assembled and disassembled as

234-465: A globular head domain that contains binding sites for talin and α-actinin as well as a tyrosine phosphorylation site, while the tail region contains binding sites for F-actin , paxillin , and lipids . Essentially, there is an 835 amino acid N-terminal head, which is split into four domains. This is linked to the C-terminal tail with a linker region. The recent discovery of the 3D structure sheds light on how this protein tailors its shape to perform

273-540: A lower affinity for the head as compared with the vinculin tail. In case of metavinculin, unfurling of the C-terminal hydrophobic hairpin loop of tail domain is impaired by the negative charges of the 68-amino acid insert, thus requiring phospholipid-activated regular isoform of vinculin to fully activate the metavinculin molecule. Vinculin has been shown to interact with: In cases of Small Intestinal Bacterial Overgrowth presented as IBS symptoms, anti-CdtB antibodies have been identified to affect vinculin function, which

312-518: A migrating cell where actin filaments polymerize at the leading edge and flow back towards the cell body. This is the source of traction required for migration; the focal adhesion acts as a molecular clutch when it tethers to the ECM and impedes the retrograde movement of actin, thus generating the pulling (traction) force at the site of the adhesion that is necessary for the cell to move forward. This traction can be visualized with traction force microscopy . A common metaphor to explain actin retrograde flow

351-426: A single copy and what appears to be no close relative to take over functions in its absence. Its splice variant metavinculin (see below) also needs vinculin to heterodimerize and work in a dependent fashion. Vinculin is a 117-kDa cytoskeletal protein with 1066 amino acids . The protein contains an acidic N-terminal domain and a basic C-terminal domain separated by a proline -rich middle segment. Vinculin consists of

390-403: A variety of functions. For example, vinculin is able to control the cell's motility by simply altering its shape from active to inactive. When in its ‘inactive’ state, vinculin's conformation is characterized by the interaction between its head and tail domains. And, when transforming to the ‘active’ form, such as when talin triggers binding, the intramolecular interaction between the tail and head

429-563: Is cortactin , which appears to link tyrosine kinase signalling to cytoskeletal reorganization in the lamellipodium and its associated structures. Rac and Cdc42 are two Rho -family GTPases which are normally cytosolic but can also be found in the cell membrane under certain conditions. When Cdc42 is activated, it can interact with Wiskott–Aldrich syndrome protein (WASp) family receptors, in particular N-WASp , which then activates Arp2/3. This stimulates actin branching and increases cell motility . Rac1 induces cortactin to localize to

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468-482: Is LxxAAxxVAxxVxxLIxxA, with a secondary structure prediction of four amphipathic helices . The hydrophobic residues that define the VBS are themselves 'masked' and are buried in the core of a series of helical bundles that make up the talin rod. Smooth muscles and skeletal muscles (and probably to a lower extent in cardiac muscle ) in their well- differentiated (contractile) state co-express (along with vinculin)

507-466: Is a large number of people being washed downriver, and as they do so, some of them hang on to rocks and branches along the bank to stop their downriver motion. Thus, a pulling force is generated onto the rock or branch that they are hanging on to. These forces are necessary for the successful assembly, growth, and maturation of focal adhesions. Extracellular mechanical forces, which are exerted through focal adhesions, can activate Src kinase and stimulate

546-408: Is also the site from which particles or aggregates attached to the cell surface migrate in a process known as cap formation . Structurally, the barbed ends of the microfilaments (localized actin monomers in an ATP -bound form) face the "seeking" edge of the cell, while the pointed ends (localized actin monomers in an ADP -bound form) face the lamella behind. This creates treadmilling throughout

585-450: Is important for durotaxis . Lamellipodia The lamellipodium ( pl. : lamellipodia ) (from Latin lamella , related to lamina , "thin sheet", and the Greek radical pod- , "foot") is a cytoskeletal protein actin projection on the leading edge of the cell . It contains a quasi-two-dimensional actin mesh; the whole structure propels the cell across a substrate. Within

624-412: Is involved: it has been shown that the inhibition of calpain leads to the inhibition of focal adhesion-ECM separation. Focal adhesion components are amongst the known calpain substrates, and it is possible that calpain degrades these components to aid in focal adhesion disassembly The assembly of nascent focal adhesions is highly dependent on the process of retrograde actin flow. This is the phenomenon in

663-438: Is required in gut motility. Focal adhesion In cell biology , focal adhesions (also cell–matrix adhesions or FAs ) are large macromolecular assemblies through which mechanical force and regulatory signals are transmitted between the extracellular matrix (ECM) and an interacting cell . More precisely, focal adhesions are the sub-cellular structures that mediate the regulatory effects (i.e., signaling events) of

702-424: Is severed. In other words, when talin's binding sites (VBS) of α-helices bind to a helical bundle structure in vinculin's head domain, the ‘helical bundle conversion’ is initiated, which leads to the reorganization of the α-helices (α1- α-4), resulting in an entirely new five-helical bundle structure. This function also extends to cancer cells, and regulating their movement and proliferation of cancer to other parts of

741-405: Is thought to function as one of several interacting proteins involved in anchoring F-actin to the membrane. Discovered independently by Benny Geiger and Keith Burridge , its sequence is 20%–30% similar to α- catenin , which serves a similar function. Binding alternately to talin or α-actinin, vinculin's shape and, as a consequence, its binding properties are changed. The vinculin gene occurs as

780-552: Is triggered upon binding to its designated partner. These changes occur when vinculin interacts with focal adhesion points to which it is binding to. When vinculin resides in its inactive form, the protein is kept designated to the cytoplasm unlike the focal adhesion points bound from the active state. The molecule talin is thought to be the major initiator of vinculin activation due to its presence in focal complexes. The combinatorial model of vinculin states that either α-actinin or talin can activate vinculin either alone or with

819-525: The RGD motif (found in proteins such as fibronectin , laminin , or vitronectin ), or the DGEA and GFOGER motifs found in collagen . Integrins are heterodimers which are formed from one beta and one alpha subunit. These subunits are present in different forms, their corresponding ligands classify these receptors into four groups: RGD receptors, laminin receptors, leukocyte-specific receptors and collagen receptors. Within

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858-476: The cytoskeleton of a cell connects to the ECM. They are limited to clearly defined ranges of the cell, at which the plasma membrane closes to within 15 nm of the ECM substrate. Focal adhesions are in a state of constant flux: proteins associate and disassociate with it continually as signals are transmitted to other parts of the cell, relating to anything from cell motility to cell cycle . Focal adhesions can contain over 100 different proteins, which suggests

897-418: The ECM. As the cell progresses along its chosen path, a given focal adhesion moves closer and closer to the trailing edge of the cell. At the trailing edge of the cell the focal adhesion must be dissolved. The mechanism of this is poorly understood and is probably instigated by a variety of different methods depending on the circumstances of the cell. One possibility is that the calcium-dependent protease calpain

936-432: The assistance of PIP2 or actin . This activation takes place by separation of the head-tail connection within inactive vinculin. Vinculin binding sites are predominantly found in talin and talin-like molecules, enabling binding of vinculin to talin, stabilising integrin-mediated cell-matrix junctions. Talin, in turn, links integrins to the actin cytoskeleton . The consensus sequence for Vinculin binding sites

975-431: The body. Cell spreading and movement occur through the process of binding of cell surface integrin receptors to extracellular matrix adhesion molecules. Vinculin is associated with focal adhesion and adherens junctions , resulting in significant protein dynamics . These are complexes that nucleate actin filaments and crosslinkers between the external medium, plasma membrane , and actin cytoskeleton. The complex at

1014-500: The cell establishes new contacts at the leading edge, and breaks old contacts at the trailing edge of the cell. One example of their important role is in the immune system , in which white blood cells migrate along the connective endothelium following cellular signals to damaged biological tissue . Connection between focal adhesions and proteins of the extracellular matrix generally involves integrins . Integrins bind to extra-cellular proteins via short amino acid sequences, such as

1053-403: The cell forward during the process of cell migration . The tip of the lamellipodium is the site where exocytosis occurs in migrating mammalian cells as part of their clathrin -mediated endocytic cycle . This, together with actin-polymerisation there, helps extend the lamella forward and thus advance the cell's front. It thus acts as a steering device for cells in the process of chemotaxis . It

1092-409: The cell membrane, where it simultaneously binds F-actin and Arp2/3. The result is a structural reorganization of the lamellipodium and ensuing cell motility. Rac promotes lamellipodia while cdc42 promotes filopodia. Ena/VASP proteins are found at the leading edge of lamellipodia, where they promote actin polymerization necessary for lamellipodial protrusion and chemotaxis. Further, Ena/VASP prevents

1131-427: The cell, the intracellular domain of integrin binds to the cytoskeleton via adapter proteins such as talin , α-actinin , filamin , vinculin and tensin . Many other intracellular signalling proteins, such as focal adhesion kinase , bind to and associate with this integrin-adapter protein–cytoskeleton complex, and this forms the basis of a focal adhesion. The dynamic assembly and disassembly of focal adhesions plays

1170-478: The focal adhesion complex at the site of integrin binding. Vinculin's ability to interact with integrins to the cytoskeleton at the focal adhesion appears to be critical for control of cytoskeletal mechanics, cell spreading, and lamellipodia formation. Thus, vinculin appears to play a key role in shape control based on its ability to modulate focal adhesion structure and function. Vinculin is present in equilibrium between an active and inactive state. The active state

1209-521: The focal adhesions consists of several proteins such as vinculin, α-actinin, paxillin, and talin, at the intracellular face of the plasma membrane. In more specific terms, the amino-terminus of vinculin binds to talin, which, in turn, binds to β-integrins, and the carboxy-terminus binds to actin, phospholipids, and paxillin-forming homodimers. The binding of vinculin to talin and actin is regulated by polyphosphoinositides and inhibited by acidic phospholipids. The complex then serves to anchor actin filaments to

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1248-866: The growth of the adhesions. This indicates that focal adhesions may function as mechanical sensors, and suggests that force generated from myosin fibers could contribute to maturing the focal complexes. This gains further support from the fact that inhibition of myosin-generated forces leads to slow disassembly of focal adhesions, by changing the turnover kinetics of the focal adhesion proteins. The relationship between forces on focal adhesions and their compositional maturation, however, remains unclear. For instance, preventing focal adhesion maturation by inhibiting myosin activity or stress fiber assembly does not prevent forces sustained by focal adhesions, nor does it prevent cells from migrating. Thus force propagation through focal adhesions may not be sensed directly by cells at all time and force scales. Their role in mechanosensing

1287-445: The insert in metavinculin is 68 AA in mammals and 79 in frog. Compared metavinculin sequences from pig, man, chicken, and frog, and found the insert to be bipartite: the first part variable and the second highly conserved. Both vinculin isoforms co-localize in muscular adhesive structures, such as dense plaques in smooth muscles , intercalated discs in cardiomyocytes , and costameres in skeletal muscles . Metavinculin tail domain has

1326-440: The lamellipodia are ribs of actin called microspikes , which, when they spread beyond the lamellipodium frontier, are called filopodia . The lamellipodium is born of actin nucleation in the plasma membrane of the cell and is the primary area of actin incorporation or microfilament formation of the cell. Lamellipodia are found primarily in all mobile cells, such as the keratinocytes of fish and frogs, which are involved in

1365-411: The lamellipodia withdraw. However, some focal complexes mature into larger and stable focal adhesions, and recruit many more proteins such as zyxin . Recruitment of components to the focal adhesion occurs in an ordered, sequential manner. Once in place, a focal adhesion remains stationary with respect to the extracellular matrix, and the cell uses this as an anchor on which it can push or pull itself over

1404-438: The lamellipodium, which aids in the retrograde flow of particles throughout. Arp2/3 complexes are present at microfilament-microfilament junctions in lamellipodia, and help create the actin meshwork. Arp2/3 can only join onto previously existing microfilaments, but once bound it creates a site for the extension of new microfilaments, which creates branching. Another molecule that is often found in polymerizing actin with Arp2/3

1443-432: The membrane and thus, helps to reinforce force on talin within the focal adhesions. The loss of vinculin impacts a variety of cell functions; it disrupts the formation of the complex, and prevents cell adhesion and spreading. The absence of the protein demonstrates a decrease in spreading of cells, accompanied by reduced stress fiber formation, formation of fewer focal adhesions, and inhibition of lamellipodia extension. It

1482-403: The quick repair of wounds . The lamellipodia of these keratinocytes allow them to move at speeds of 10–20 μm / min over epithelial surfaces. When separated from the main part of a cell, a lamellipodium can still crawl about freely on its own. Lamellipodia are a characteristic feature at the front, leading edge, of motile cells. They are believed to be the actual motor which pulls

1521-486: Was discovered that cells that are deficient in vinculin have growth cones that advance more slowly, as well as filopodia and lamellipodia that were less stable than the wild-type. Based on research, it has been postulated that the lack of vinculin may decrease cell adhesion by inhibiting focal adhesion assembly and preventing actin polymerization. On the other hand, overexpression of vinculin may restore adhesion and spreading by promoting recruitment of cytoskeletal proteins to

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