[Fibronectins: structure and function].

Fibronectins are a class of high-molecular-weight glycoproteins found in a soluble form in blood and other body fluids and in an insoluble form in tissues. Cellular and plasma fibronectins are very similar in structure and properties, but are not identical. Fibronectins are synthesized by a wide variety of cells in vitro including fibroblasts, Schwann cells, chondrocytes, myoblasts, macrophages, hepatocytes and intestinal epithelial cells. They exhibit an affinity for both native and denatured forms of collagen, fibrinogen or fibrin, glycosaminoglycans, proteoglycans and surfaces of many kinds of eukaryotic cells. Fibronectins also bind to bacteria, viral glycoproteins and some protozoan parasites and interact with complement components. As a result of these multiple interactions, fibronectins might act as a non-specific opsonin. Fibronectins have been implicated in a variety of cell functions including cellular adhesion and morphology, cytoskeletal organization, oncogenic transformation, cell migration, phagocytosis, haemostasis and embryonic differentiation.