Glycoproteins fibronectin

Fibronectin Glycoprotein Amino acids and monosaccharides Attachment factor between collagen fibers and fibroblasts... 

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. 

The same ceUs that secrete collagen also secrete fi-bronectin, a large glycoprotein present on cell surfaces, in the extracellular matrix, and in blood (see below). Fi-bronectin binds to aggregating precollagen fibers and alters the kinetics of fiber formation in the pericellular matrix. Associated with fibronectin and procollagen in... 

FIBRONECTIN IS AN IMPORTANT GLYCOPROTEIN INVOLVED IN CELL ADHESION MIGRATION... 

Glycoprotein llb/llla Platelets allbps ICAM-2 Fibrinogen, fibronectin, von Willebrand factor Platelet adhesion and aggregation... 

Thus, while glycoprotein Ia/IIa (a2Pj) binds to collagen, glycoprotein Ic/IIa (a ) binds to fibronectin (5). The other integrin belonging to the beta 1 family that is involved in platelet adhesion is ct6P, which binds laminin. 

It has been shown that cell adhesion highly depends on the outermost functional groups on SAMs however, cells do not directly interact with the SAMs. Instead, they interact with proteins adsorbed on SAMs. Cell adherence requires an interaction between integral molecules in the cell membrane and glycoproteins specialized for cell adhesion, like fibronectin (Fn) and vitronectin (Vn), which are adsorbed on the artificial material. Thus, the presence of glycoproteins in serum plays a crucial role in cell adherence to artificial materials. In the first part of this review (Sect. 2), we will briefly survey recent studies of cell adhesion on SAMs with different functional groups and discuss the mechanisms involved. 

FIGURE 7-1 The immunoglobulin (Ig) gene family of molecules. Several varieties of Ig domain-containing molecules are contained within the Ig gene superfamily. Most are type I membrane proteins some have only Ig domains or other moieties that may convey function (see text). V, variable Ig domain C, constant Ig domain MAG, myelin-associated glycoprotein NCAM, neural cell adhesion molecule GPI, glycosylphosphatidyl-inositol EC, extracellular domain FN, fibronectin. 

Brummendorf, T. and Rathjen, F. G. Axonal glycoproteins with immunoglobulin and fibronectin type II-related domains in vertebrates Structural features, binding activities and signal transduction. /. Neurochem. 61 1207-1219, 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. 

The carboxy-terminal region in apolipoprotein (a) closely resembles the protease domain in plasminogen [eight amino acid substitutions, nine amino acid deletions, and one insertion in apo(a) relative to plasminogen, with 94% overall nucleotide sequence identity] (G28). The most important difference is the substitution of arginine by serine in the site responsible for proteolytic activity (position 4308) (G28). As a result, Lp(a) has no protease activity towards substrates for plasmin (J3). Salonen (SI) reported a serine-protease activity of Lp(a) towards fibronectin, a glycoprotein present in connective tissue matrices. 

Unlike the acellular basement membranes, the interstitial connective tissue consists of cells distributed in meshwork of collagen fibers, glycoproteins (e.g., fibronectin), proteoglycans, and hyaluronic acid. The main forms of collagen found in interstitial connective tissue are known as type I, II, and III or interstitial collagen. 

Sazuka, M., Itoi, T., Suzuki, Y., Odani, S., Koide, T., and Isemura, M., Evidence for the interaction between (—)-epigallocatechin gallate and human plasma proteins fibronectin, fibrinogen, and histidine-rich glycoprotein, Biosci. Biotechnol. Biochem., 60, 1317, 1996. 

A prominent finding in transformed cells has been the absence, or marked lessening of the content, of a high-molecular-weight, cell-surface glycoprotein known as LETS protein, or fibronectin, that is involved in the attachment of the cells to the substratum (for a review, see Hynes and coworkers538). 

Cultured BHK cells that had heen maintained in a medium containing tunicamycin still shed various membrane glycoproteins into the medium,539 and this is in keeping with observations mentioned in Section IV,4. However, the proportion of fibronectin found in the medium appeared to he lessened.540-541 Cells kept in the presence of tunicamycin showed profound morphological changes, from epitheloid to elongated, spindle-shaped morphology, and lowered adhesion to the substratum. 

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