Vinculin

Vinculin
PDB rendering based on 1qkr.
Available structures PDB Ortholog search: PDBe, RCSB List of PDB id codes 1RKC, 1RKE, 1SYQ, 1TR2, 1YDI, 2GWW, 2HSQ, 2IBF, 3H2U, 3H2V, 3MYI, 3RF3, 3S90, 3TJ5, 3TJ6, 3VF0, 4DJ9, 4EHP
Identifiers
Symbols	VCL; CMD1W; CMH15; MVCL
External IDs	OMIM: 193065 MGI: 98927 HomoloGene: 7594 GeneCards: VCL Gene
Gene Ontology Molecular function • dystroglycan binding • actin binding • structural molecule activity • protein binding • beta-catenin binding • Rho GTPase binding • alpha-catenin binding • cadherin binding Cellular component • extracellular region • cytosol • cytoskeleton • cell-cell junction • adherens junction • cell-cell adherens junction • fascia adherens • focal adhesion • actin cytoskeleton • Z disc • cell-substrate junction • sarcolemma • costamere • protein complex Biological process • morphogenesis of an epithelium • platelet degranulation • cellular component movement • muscle contraction • cell adhesion • cell-matrix adhesion • blood coagulation • lamellipodium assembly • platelet activation • negative regulation of cell migration • adherens junction assembly • protein localization to cell surface • apical junction assembly • epithelial cell-cell adhesion Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	7414	22330
Ensembl	ENSG00000035403	ENSMUSG00000021823
UniProt	P18206	Q64727
RefSeq (mRNA)	NM_003373	NM_009502
RefSeq (protein)	NP_003364	NP_033528
Location (UCSC)	Chr 10: 75.76 – 75.88 Mb	Chr 14: 20.93 – 21.03 Mb
PubMed search	[1]	[2]
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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. Discovered independently by Benny Geiger^[1] and Keith Burridge,^[2] 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 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 cytoskeletal protein associated with cell-cell and cell-matrix junctions, where it is thought to function as one of several interacting proteins involved in anchoring F-actin to the membrane. Multiple alternatively-spliced transcript variants have been found for this gene, but the biological validity of some variants has not been determined. Human vinculin protein exhibits a greater-than-95% sequence identity to the chicken vinculin protein.^[3]

Structure [edit]

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 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 (Goldman et al. 2001).

Essentially, there is a 835 amino acid N-terminal head, which is split into four domains. This is linked to the C-terminal head with a linker region.

Conformation [edit]

The recent discovery of the 3D structure sheds light on how this protein tailors its shape to perform 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 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 the body.

Mechanism and Function [edit]

Background

Cell spreading and movement occur though the process of binding of cell surface integrin receptors to extracellular matrix adhesion molecules. Vinculin is associated with focal adhesion and adherens junctions, which are complexes that nucleate actin filaments and crosslinkers between the external medium, plasma membrane, and actin cytoskeleton^[4](Xu et al. 1998). The complex at the focal adhesions consists of several proteins such as vinculin, α-actin, paxillin, and talin, at the intracellular face of the plasma membrane.

In more specific terms, the amino-terminal of vinculin binds to talin, which, in turn, binds to β-integrins, and the carboxy-terminal 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 the membrane^[5](Ezzell et al. 1997).

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^[6] (Goldman et al. 2001). It was discovered that cells that are deficient in vinculin have growth cones that advance more slowly, as well as filopodia and lamellipoida 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 the focal adhesion complex at the site of integrin binding^[5](Ezzell et al. 1997). 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 binding site [edit]

VBS
human vinculin head (1-258) in complex with talin's vinculin binding site 3 (residues 1944-1969)
Identifiers
Symbol	VBS
Pfam	PF08913
InterPro	IPR015009
Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary

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 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.^[7]

Splice variant: Metavinculin [edit]

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) 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 1980s.^[8] 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^[9]

Length of the insert in metavinculin is 68AA in mammals 79 in frog. Strasser et al.^[10] 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.^[11] Metavinculin tail domain has 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.

Interactions [edit]

Vinculin has been shown to interact with SORBS1,^[12] CDH1^[13][14] and Paxillin.^[15][16][17]

References [edit]

Further reading [edit]

v t e PDB gallery 1qkr: CRYSTAL STRUCTURE OF THE VINCULIN TAIL AND A PATHWAY FOR ACTIVATION  1rkc: Human vinculin head (1-258) in complex with talin's vinculin binding site 3 (residues 1944-1969)  1rke: Human vinculin head (1-258) in complex with human vinculin tail (879-1066)  1st6: Crystal structure of a cytoskeletal protein  1syq: Human vinculin head domain VH1, residues 1-258, in complex with humantalin's vinculin binding site 1, residues 607-636  1t01: Vinculin complexed with the VBS1 helix from talin  1tr2: Crystal structure of human full-length vinculin (residues 1-1066)  1u6h: Vinculin head (0-258) in complex with the talin vinculin binding site 2 (849-879)  1xwj: Vinculin head (1-258) in complex with the talin vinculin binding site 3 (1945-1969)  1ydi: Human Vinculin Head Domain (VH1, 1-258) in Complex with Human Alpha-Actinin's Vinculin-Binding Site (Residues 731-760)  1zvz: Vinculin Head (0-258) in Complex with the Talin Rod Residue 820-844  1zw2: Vinculin Head (0-258) in Complex with the Talin Rod residues 2345-2369  1zw3: Vinculin Head (0-258) in Complex with the Talin Rod residues 1630-1652  2gdc: Structure of Vinculin VD1 / IpaA560-633 complex  2gww: Human vinculin (head domain, Vh1, residues 1-258) in complex with Shigella's IpaA vinculin binding site (residues 602-633)  2hsq: Human vinculin (head domain, Vh1, residues 1-258) in complex with Shigella's IpaA vinculin binding site 2 (residues 565-587)

External links [edit]

• MBInfo - Vinculin
• http://www.stjude.org/media/0,2561,453_5297_9660,00.html
• http://www.medicalnewstoday.com/medicalnews.php?newsid=5196
• http://www.olympusmicro.com/primer/techniques/fluorescence/gallery/cells/bpae/images/bpaelarge.jpg
• Vinculin Info with links in the Cell Migration Gateway