Integrins assembly

Fibronectin receptor is a two-chain glycoprotein of the integrin family that serves as a transmembrane linker by binding to talin on the cytoplasmic side and to fibronectin on the external side of the membrane. The pull exerted by stress fibers on attached structures may be produced by bipolar assemblies of nonmuscle myosin molecules producing a sliding of actin filaments of opposite polarity. 

Mi LX, Fischer S, Chung B et al (2006) Self-assembling protein hydrogels with modular integrin binding domains. Biomacromolecules 7 38 7... 

Boturyn D, Coll J-L, Garanger E et al (2004) Template assembled cyclopeptides as multimeric system for integrin targeting and endocytosis. J Am Chem Soc 126 5730-5739... 

Fibroblasts and endothelial cells do not assemble hemidesmosomes. Rather, their matrix adhesive devices are so-called focal contacts. Pivotal components of focal contacts are heterodimeric integrins that bind to a... 

Koster, J., Geerts, D., Favre, B., Borradori, L., and Sonnenberg, A. (2003). Analysis of the interactions between BP180, BP230, plectin, and the integrin alpha6beta4 important for hemidesmosome assembly./ Cell Sci. 116, 387-399. 

Koster, J., van Wilpe, S., Kuikman, I., Litjens, S. H., and Sonnenberg, A. (2004b). Role of binding of plectin to the integrin beta4 subunit in the assembly of hemidesmosomes. Mol. Biol. Cell 15, 1211-1223. 

Fig. 1 Downstream effects of integrin activation during outside-in signalling. The ECM properties and the growth factor environment regulate assembly of the ECM-integrin-adhesome-F-actin system, which controls cell activity. The long-term effects of the outside-in signalling (10-60 min) are indicated in italics...

However, unlike other cell surface receptors, integrin tails lack intrinsic catalytic activity. Instead, the tails of integrins recruit a plethora of signalling and adaptor molecules that assemble into FAs to relay intracellular signals, and to engage and remodel the actin cytoskeleton. To date, more than 150 proteins have been identified as being recruited to integrin adhesions and to constitute the adhesome [13-15],... 

Despite this complexity, most integrins share two, key interrelated functions first, to promote the assembly and organization of the actin cytoskeleton [122, 123] and second, to regulate signal transduction cascades [124-126], Spanning the cell membrane, these subunits serve as a communication pathway, linking the actin cytoskeleton and intracellular cytoplasmic proteins involved in focal adhesion complexes (FACs) with the cell s dynamic extracellular environment (Fig. 8) [127-130]. There are at least 50 distinct proteins known to be involved in FACs. Actin [131], vinculin, talin, tensin, a-actinin, and filamin provide a structural role, while focal adhesion kinase [132], integrin-linked kinase, Src-family kinase, PINCH, paxillin... 

Recently, TTR1 fibrils have been decorated with the classic RGD tripeptide motif isolated from fibronectin, which encourages cell adhesion via integrin cell surface receptors (Gras et al., 2008). This bioactive tag was added to the TTR1 sequence which drives fibril assembly and the tag shown to be exposed on the fibril surface and accessible to cells following assembly. The RGD-modified fibrils were bioactive in a cell dissociation assay which measures the ability of fibrils to competitively bind to cells and induce cell detachment from a surface, as illustrated in Figure 19. In... 

Adhesive interactions play critical roles in the migration of cells. These interactions are mediated by cell-surface receptors, the integrins that bind to components of the extra-celluar matrix and/or to ligands presented by adjacent cells. Consequently, these interactions lead to the formation of intracellular cytoskeletal assemblies and actin bundles (Fig. 4.4). 

---