Integrins complex assembly

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... 

Integrins associate with the membrane protein caveolin.34 Although little is yet known about this particular interaction, it could assist in forming integrin clusters at the plasma membrane which might serve as a scaffold for the assembly of multi-component signalling complexes. This possibility is attractive, because caveolin binds cholesterol and glycosphingolipids and forms membrane rafts , enriched in myristoylated and palmitoy-lated Src-family kinases (Chapter 8).35... 

A functional integrin is a heterodimeric protein complex consisting of an a and a P subunit. So far, the mammalian integrin family consists of 8 P subunits and 18 a subunits, which are known to assemble into 24 distinct integrins (Fig. 1). The different combination of subunits accounts for heterodimer specificity, with certain integrins showing preference for particular ECM... 

Hotchin NA, HaU A. The assembly of integrin adhesion complexes requires both extraceUular matrix and intracellular rho/rac GTPases. J. Cell. Biol. 1995 131 1857-1865. 

Fig. 18. Subunits and assembly of integrins. Seven 3 subunits and fourteen a subunits are shown which can form in various combinations to produce dimeric, non-covalently bonded complexes with various ligand binding properties, some of which are indicated in boxes. Abbreviations Fn, fibronectin Lm, laminin coll, collagen Fb, fibrinogen Op, osteopontin ICAM, ICAM family 1 or 2 BM, unidentified basement membrane component(s). a, is also called pl50 or GDI Ic Ol and are GDI la and GDI lb, respectively 32 is GDIS in the immunological literature.

The process of elastic fiber assembly " is mediated by a non-integrin cell surface complex, named the cell-surface elastin receptor (CSER), which can be captured... 

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