Zonula adhaerens: Diferenzas entre revisións

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Revisión como estaba o 28 de xuño de 2012 ás 15:35

As zonula adhaerens (tamén escrito zonula adherens) tamén chamdas unións adherentes ou desmosomas en banda^[1]) son complexos proteicos que aparecen nas unións entre as células dos tecidos epiteliais. A cara citoplasmática destas unións está unida ao citoesqueleto de actina. Están situadas xeralmente nunha posición máis basal ca as unións herméticas. Aparecen xeralmente como bandas que rodean a célula.

Unha unión celular parecida que se chama fascia adhaerens aparece en células non epiteliais, como as células musculares cardíacas. É estruturalmente igual, pero aparece formando patróns con forma de fita que non rodean por completo a célula.

Compoñentes proteicos

Adherens junctions are composed of the following 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.
p120 (sometimes called delta catenin) binds the juxtamembrane region of the cadherin.
β-catenin or gamma-catenin (plakoglobin) binds the catenin-binding region of the cadherin.
α-catenin binds the cadherin indirectly via β-catenin or plakoglobin and links the actin cytoskeleton with cadherin.

^[2]

Modelos

Adherens junctions were, for many years, thought to share the characteristic of anchor 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) demonstrate that membrane associated actin is several fold less stable compared to components of the adherens junctional complex.^[3]^[4]

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.

Notas

↑ http://219.221.200.61/ywwy/zbsw%28E%29/edetail4.htm
↑ Ferreri DM, Vincent PA (2008). "Signaling to and through the Endothelial Adherens Junction". En LaFlamme SE, Kowalczyck AP. Cell Junctions: Adhesion, Development, and Disease. Wiley VCH. ISBN 978-3-527-31882-7.
↑ Yamada S, Pokutta S, Drees F, Weis W, Nelson W (2005). "Deconstructing the cadherin-catenin-actin complex.". Cell 123 (5): 889–901. PMID 16325582. doi:10.1016/j.cell.2005.09.020.
↑ 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. doi:10.1016/j.cell.2005.09.021.

Ligazóns externas

MBInfo - Unión adherente (zonula adhaerens)
BUHistology - 20502loa [1]

[1] ttp://219.221.200.61/ywwy/zbsw%28E%29/edetail4.htm

[2] Ferreri DM, Vincent PA (2008). "Signaling to and through the Endothelial Adherens Junction". En LaFlamme SE, Kowalczyck AP. Cell Junctions: Adhesion, Development, and Disease. Wiley VCH. ISBN 978-3-527-31882-7.

[3] Yamada S, Pokutta S, Drees F, Weis W, Nelson W (2005). "Deconstructing the cadherin-catenin-actin complex.". Cell 123 (5): 889–901. PMID 16325582. doi:10.1016/j.cell.2005.09.020.

[4] 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. doi:10.1016/j.cell.2005.09.021.

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