Adhesion receptors

The largest numbers of integrins are members of the (31 integrins, also known as the very late antigen (VLA) subfamily because of its late appearance after activation. There are at least seven receptors characterized from this subfamily, each with different ligand specificity. Among the most studied include the 04(31 and a5 31 receptors. The leukocyte integrin a4 31 is a cell adhesion receptor that is predominantly expressed on lymphocytes, monocytes and eosinophils. 

VLA-6 Adhesion receptor Decrease of in vitro invasion and in vivo metastatic ability... 

The leukocyte integrin a 4(3 1 (also known as VLA-4 and CD49d/CD29) is a cell adhesion receptor, which is predominantly expressed on lymphocytes, monocytes and eosinophils. VLA-4 is generally selective for the CS1 domain within fibronectin, with an essential requirement for LDV sequence for binding. VLA-4 also binds to VCAM-1 as a counter receptor. 

In the intact blood vessel, ligands involved in adhesion to platelets, such as collagen, fibronectin, and von Willebrand factor, are sequestered in the subendothelium, thus preventing access to platelet adhesive receptors. Table 1 summarizes the functions of platelet membrane integrin receptors. 

As in any field, extrapolation of in vitro data to the in vivo context warrants caution. Nevertheless, as revealed in this study, experimentally demonstrated down-regulation of ET-1 gene expression by HU corroborates the in vivo findings where ET-1 levels correlate with the clinical stage of SCA. Similarly, the balance between soluble and membrane-bound adhesive receptors of endothelial and other cells may dictate the triggering of acute clinical events. Individualized therapies for... 

Souza, E.D., Ginsberg, M.H., Lam, S., and Plow, E.F. (1988) Chemical cross-linking of arginylglycyl-aspartic acid peptides to an adhesion receptor on platelets./. Biol. Chem. 263, 3943-3951. 

Springer, T. A. Adhesion receptors of the immune system. Nature 346 425-434,1990. 

Takeichi, M. Cadherin cell adhesion receptors as a morphogenetic regulator. Science 25 1451-1455,1993. 

Other adhesion receptors that are structurally and functionally related include the receptors for fibronectin, vitronectin, platelet glycoproteins 13b and Ilia and the VLA (very-late antigen) series. All molecules involved in adhesion recognise the RGD motif and require the divalent cations Ca2+ and Mg2+ for binding. All are dimers of glycosylated proteins with relative molecular masses 95-190 kDa. There is also some sequence homology between the /J-chain (CD18) and one chain of the fibronectin receptor. 

TABLE 2.3 Synthetic and naturally occurring anti-adhesive receptor analogs... 

The interaction of CSN5 to the member of the IkB multigene family Bcl3, the progesterone receptor PR, and the steroid receptor co-activator SRC-1, leads to stabilization of Bcl3-p50 and PR-SRC-1 complexes and enhances transcriptional activity [42, 43]. Whereas AP-1 activity is stimulated by interaction of CSN5 with the integrin adhesion receptor LFA-1 [44], the opposite effect was reported in the... 

SHIP SH2 domain binds to the phosphorylated mM (p-ITIM) of other inhibitory co-receptors (gp49Bl) (Kuroiwa etal, 1998) and to the p-ITIM-like motif of the adhesion receptor, PECAM-1 (Pumphrey et al., 1999), furthermore, in vitro it binds to the phosphorylated immimoreceptor tyrosine based activation motifs (p-TTAM) within the p and y subunits of the high affinity IgE receptor (Kimura et al. 1997)), and the zeta chain of T cell receptor (Osborne et al, 1996). However, in vivo coprecipitation of these molecules was not observed. 

Table L Examples of specific amino acid sequences in extracellular matrix molecules, which represent ligands for cell adhesion receptors and can be used in tissue engineering...

Amino acid sequence Typical for a certain ECM molecule Preferred by a certain cell adhesion receptor Preferred by a certain cell type... 

Figure. 4. Principle of the cell adhesion to artificial materials. In cell culture media or body fluids, the material is spontaneously adsorbed with cell adhesion-mediating extracellular matrix proteins (e g., vitronectin, fibronectin). The cells then adhere to specific amino acid sequences of these proteins by their adhesion receptors of integrin or non-integrin type [38-41].

Although the single amino acids cannot bind the adhesion receptors on cells, they provide other ehemieal functional groups which may improve the adsorption of eell adhesion-mediating molecules on the material surface. Similar efifeet was observed on ion-implanted polyethylene grafted with the Arg-Gly-Asp (RGD)... 

Ulrich H, Magdesian MH, Alves MJ et al (2002) In vitro selection of RNA aptamers that bind to cell adhesion receptors of Trypanosoma cruzi and inhibit cell invasion. J Biol Chem 277 20756-20762... 

Platelets also express adhesion receptors of the selectin gene family (P-selectin) and of the immunoglobulin gene superfamily (PECAM-1 and ICAM-2) (6). Expression of PECAM-1 and ICAM-2 may play a role in platelet interactions with endothelial cells and leukocytes, respectively. 

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