Information about Zonula Adherens
Adherens junctions (or zonula adherens) are protein complexes that occur at cell-cell junctions in epithelial tissues, usually more basal than tight junctions.
They can appear as bands encircling the cell (zonula adherens) or as spots of attachment to the extracellular matrix (adhesion plaques).
The accepted model has been that adherens junctions serve as a bridge connecting the actin cytoskeleton of neighboring cells through direct interaction. However, scientists have not been able to isolate the quaternary complex of cadherin-βcatenin-αcatenin-actin in vitro. Recent data (2005) from 2 labs at Stanford University published in the journal Cell demonstrates that membrane associated actin is several fold less stable compared to components of the adherens junctional complex.[1][2]
Additionally, the authors found that monomeric α-catenin preferentially binds to the cadherin junction complex through β-catenin. Dimeric α-catenin preferentially binds to actin and suppresses Arp2/3 complex-mediated actin branching, thus acting as a molecular switch to regulate actin polymerization.
Adherens junctions may serve as a regulatory module to maintain the actin contractile ring with which it is associated in microscopic studies.
They can appear as bands encircling the cell (zonula adherens) or as spots of attachment to the extracellular matrix (adhesion plaques).
Proteins
They are composed of three major proteins:- cadherins. The cadherins are a family of transmembrane proteins that form homodimers in a calcium-dependent manner with other cadherin molecules on adjacent cells.
- β-catenin and α-catenin. The catenins both form a complex with the intracellular portion of the cadherin molecule.
Models
Adherens junctions were, for many years, thought to share the characteristic of anchoring cells through their cytoplasmic actin filaments.The accepted model has been that adherens junctions serve as a bridge connecting the actin cytoskeleton of neighboring cells through direct interaction. However, scientists have not been able to isolate the quaternary complex of cadherin-βcatenin-αcatenin-actin in vitro. Recent data (2005) from 2 labs at Stanford University published in the journal Cell demonstrates that membrane associated actin is several fold less stable compared to components of the adherens junctional complex.[1][2]
Additionally, the authors found that monomeric α-catenin preferentially binds to the cadherin junction complex through β-catenin. Dimeric α-catenin preferentially binds to actin and suppresses Arp2/3 complex-mediated actin branching, thus acting as a molecular switch to regulate actin polymerization.
Adherens junctions may serve as a regulatory module to maintain the actin contractile ring with which it is associated in microscopic studies.
References
1. ^ Yamada S, Pokutta S, Drees F, Weis W, Nelson W (2005). "Deconstructing the cadherin-catenin-actin complex.". Cell 123 (5): 889-901. PMID 16325582.
2. ^ Drees F, Pokutta S, Yamada S, Nelson W, Weis W (2005). "Alpha-catenin is a molecular switch that binds E-cadherin-beta-catenin and regulates actin-filament assembly.". Cell 123 (5): 903-15. PMID 16325583.
2. ^ Drees F, Pokutta S, Yamada S, Nelson W, Weis W (2005). "Alpha-catenin is a molecular switch that binds E-cadherin-beta-catenin and regulates actin-filament assembly.". Cell 123 (5): 903-15. PMID 16325583.
External links
| Cell junctions - [ edit] |
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| Adherens junction | Desmosome | Hemidesmosome | Gap junction | Tight junction |
Tight junctions, or zonula occludens, are the closely associated areas of two cells whose membranes join together forming a virtual impermeable barrier to fluid. It is a type of junctional complex only present in vertebrates.
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Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion whereby they ensure cells within tissues are bound together. They are dependent on calcium (Ca2+) ions to function, hence their name.
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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle. Designs of bridges will vary depending on the function of the bridge and the nature of the terrain where the bridge is to be constructed.
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In vitro (Latin: (with) in the glass) refers to the technique of performing a given experiment in a test tube, or, generally, in a controlled environment outside a living organism. In vitro fertilization is a well-known example of this.
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Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private university located approximately 37 miles (60 kilometers) southeast of San Francisco and approximately 20 miles (32 km) northwest of San Jose in Stanford,
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Arp2/3 complex is a seven-subunit protein that plays a major role in the regulation of the actin cytoskeleton. It is a necessary component of the actin cytoskeleton and is therefore ubiquitous in actin cytoskeleton-containing eukaryotic cells.[1].
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Cytokinesis is the process whereby the cytoplasm of a single cell is divided to spawn two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two to ensure that chromosome number is maintained from one
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Boston University (BU) is a private research university located in Boston, Massachusetts, United States. Although chartered by the Massachusetts Legislature in 1869, Boston University traces its roots to the establishment of the Newbury Biblical Institute in Newbury,
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A cell junction is a structure within a tissue of a multicellular organism. Cell junctions are especially abundant in epithelial tissues. They consist of protein complexes and provide contact between neighbouring cells, between a cell and the extracellular matrix, or they built up
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desmosome, also known as macula adherens (Latin: adhering spot), is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes.
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Hemidesmosomes (HD) are very small stud- or rivet-like structures on the inner basal surface of keratinocytes in the epidermis of skin. They are similar in form to desmosomes.
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A gap junction or nexus is a junction between certain animal cell-types that allows different molecules and ions, mostly small intracellular signaling molecules (intracellular mediators), to pass freely between cells. The junction connects the cytoplasm of cells.
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Tight junctions, or zonula occludens, are the closely associated areas of two cells whose membranes join together forming a virtual impermeable barrier to fluid. It is a type of junctional complex only present in vertebrates.
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