Laminin integrins interactions with

The extracellular domains of integrins interact with a variety of profeins of the extracellular matrix. These include fibronectin, fibrinogen, vifronecfin, collagen, and entacfin. Other large cell surface adhesins include laminin and osteopontin (Chapfer 8), thrombospondin, von Willebrand factor, and related proteins. These adhesins appear to depend upon the sequence Arg-Gly-Asp (RGD), which binds nonco-valently to integrins, which act as cell-surface receptors. See also Chapter 12, Section C,9. 

Given that the structural domains of laminin that interact with cellular receptors have polypeptide sequences apparently not shared by other ECM molecules, then it is reasonable to expect that the cellular receptors for laminin might also be unique. Nevertheless, the results of antibody inhibition experiments may be taken together as an indication that at least one site located on the long arm of laminin interacts with integrins or integrin-associated molecules on the membranes of neurons and other cells (Mercurio,... 

Figure 48-4. Schematic representation of a cell interacting through various integrin receptors with collagen, fibronectin, and laminin present in the ECM. (Specific subunits are not indicated.) (Redrawn after Yamada KM Adhesive recognition sequences. J Biol Chem 1991 266 12809.)...

Integrins themselves are found on nearly all cells and mediate several physiological responses, such as cell-cell and cell-matrix interactions. Three families of integrins, each family with a common beta subunit in combination with distinct alpha subunits, have been recognized. The beta 1 family, also called very late lymphocyte-activation antigen or VLA, has receptors mediating extracellular matrix interactions with molecules such as collagen, laminin, and fibronectin. Naturally, platelets contain many of the receptors of the beta 1 family. 

Cells are sometimes cultured in serum-free medium. In this condition, the surface should carry substituents of serum proteins that can directly interact with cells. SAMs of alkanethiols with bioactive ligands have been used to control interactions between the material surface and cells [80-83]. Several bioactive ligands have been tested, including RGD [80], PHSRN [81], and laminin-derived peptides [82, 83]. These ligands were expected to directly interact with cell surface integrins. 

Kawakami Y, Kawakami K, Steelant WFA, Ono M, Baek RC, Handa K, Withers DA, Hakomori S. Tetraspanin CD9 is a Proteolipid, and its interaction with alpha 3 integrin in microdomain is promoted by GM3 ganglioside, leathng to inhibition of laminin-5-dependent cell motility. J. Biol. Chem. 2002 277 34349-34358. 

Skubitz, A.P., Letoumeau, P.C., Wayner, E. and Furcht, L.T. (1991) Synthetic peptides from the carboxy-terminal globular domain of the A chain of laminin their ability to promote cell adhesion and neurite outgrowth, and interact with heparin and the jl-l integrin subunit. J. Cell Biol. 115 1137-1148. 

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