Fibronectin extracellular matrix

It is of interest that proteins termed motility factors (55-70 kD) are secreted by fetal cells and some tumor cells. These proteins act as autocrine factors and stimulate rapid movement by these cells. Motility factors induce the formation of cell processes that are packed with actin filaments and have an increased number of receptors for the matrix proteins laminin and fibronectin. The latter enhance the ability of the cells to bind to the extracellular matrix. Thus, it is likely that motility factors influence the organization of the cytoskeleton through changes taking place at the cell surface (reviewed by Warn and Dowrick, 1989). 

F9 embryonal carcinoma cells have a simple set of growth supplements which are required for growth in serum-free medium insulin, transferrin, and fibronectin (Rizzino and Sato, 1978). Fibronectin is a component of the extracellular matrix and facilitates the attachment of the cells to the culture dish. In addition, high density lipoprotein (HDL) has been observed to promote the growth of F9 cells serum-free. 

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... 

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. 

Fibronectin is an extracellular matrix protein that mediates a variety of cellular effects. It is important in cell-cell and cell-substratum interactions ( 3.9), mediates reticuloendothelial cell activity and binds both to Clq (the first component of complement) and to bacteria. It also increases the tu-mouricidal activity of macrophages and activates complement receptors, by regulating the binding of C3b-coated particles to neutrophils. It may mediate attachment of Staphylococcus aureus to neutrophils and may also play a role as an adhesion factor, promoting the adhesion of neutrophils to surfaces. Fibronectin mRNA (8.7-8.8 kb) is detected only at low levels in... 

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].

Transforming growth factor beta TGEP many cells stimulates deposition of extracellular matrix, by increasing synthesis of proteins such as fibronectin and the integrins ... 

Gateau E, Levasseur P, Borgonovi M, Imbert C. (2007) The effect of aminocandin (HMR 3270) on the in vitro adherence of Candida Albicans to polystyrene surfaces coated with extracellular matrix proteins or fibronectin. Clin Microbiol Infec 13 311-315. 

Targeting to SECs should be directed at specific receptors present on this ceU type. A wide range of proteins and other molecules can be taken up by SECs through receptor-mediated endocytosis. For example, SECs play an important role in the uptake of degradation prodncts of the extracellular matrix. For this purpose they have hyaluronan [6], (pro)coUagen, and fi-bronectin receptors [7]. The first two receptors are nniqnely located on SECs. Elevated levels of serum hyaluronan and fibronectin, that are often fonnd in Uver disease [8], are nsnally the result of dysfunction of the clearance capacity of SECs combined with an increased production by HSCs [9]. 

Adhesive proteins provide the connections between the various components of the extracellular matrix. Important representatives include laminin and fibronectin (see B). These multifunctional proteins simultaneously bind to several other types of matrix component. Cells attach to the cell surface receptors in the ECM with the help of the adhesive proteins. 

Hematopoiesis, the process of generating mature blood cells, is mainly located in the red bone marrow, predominantly in the sternum, femur and pelvic bones [1]. In the marrow the hematopoietic cells are embedded in stromal tissue. This consists of different cell types (e.g., fibroblasts, endothehal cells, adipocytes, macrophages) that provide soluble and membrane-bound growth factors and produce an extracellular matrix consisting of collagen, laminin, fibronectin, and glycosaminoglycans [2, 3]. The interactions between hematopoietic cells, stromal cells and extracellular matrix are indicated in Fig. 1 [4,5]. 

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