Fibronectin (
FN) is a high molecular weight,
multidomain glycoprotein, comprising about 5% by weight of carbohydrate.
Fibronectin exhibits diverse recognition functions located on distinct fragments or domains, so FN can interact with a variety of macromolecules including/on :
●
cytoskeleton●
extracellular matrix –
collagen, glycosaminoglycans, proteoglycans, tenascin, fibulin and thrombospondin
● circulating
coagulation factors – Fn is covalently incorporated into fibrin clots through the transglutaminase action of coagulation factor XIII, improving fibroblast adhesion
●
fibrinolytic system●
acute phase proteins●
complement system●
cell-surface receptors on a variety of cells including fibroblasts, neurons, phagocytes and bacteria – integrins (through RGD tripeptide)
● itself, forming fibrillar entities
● small molecules such as gangliosides, sugars, and
Ca ions.
Fibronectin (FN) participates in tissue repair,
embryogenesis,
blood clotting, and cell
migration/
adhesion. Cells of most tissues synthesize fibronectin. Soluble fibronectin is produced by hepatocytes and circulates, in its disulfide-bonded dimeric form, in the plasma. The soluble protomer is a compact, flexible dimer that can be converted into an insoluble, fibrillar network. The soluble-to-fibrillar conversion is a highly regulated process involving
integrins and possibly other cell-surface receptors [
ref] including uPAR (urokinase-type plasminogen activator receptor) [
ref] and a cell-surface proteoglycan [
ref].[
s]
The insoluble fibronectin dimer is synthesized by fibroblasts, chondrocytes, endothelial cells, macrophages, as well as certain epithelial cells. Electron microscopic analyses of natural thin fibrils (5-18nm diameter), made by fibroblasts in culture, clearly indicate an ordered arrangement and suggest a model in which extended protomers (130nm long) are arranged end-to-end with an overlap of about 14 nm [
ref]. As an extracellular adhesion molecule, FN binds to
integrins and participates in wound healing.
Cell-surface receptors or fibrinogen, collagen and fibrin (as extracellular matrix proteins) facilitate the adherence of microorganisms to host tissues [
ref]. The Hep-2 domain of fibronectin interacts with envelope glycoproteins on some
retroviruses. Fibronectin is able to bind both the virus and cell-surface receptors, concentrating viruses on the surface of the cells, enhancing viral uptake by cells.
The structural
isoforms of fibronectin arise from
alternative splicing of a single gene, and possess a variable region plus three types of repeated internal regions (homologous, repeating modules I, II and III) +/- disulfide bonds.
[
more] []
The Type I module of fibronectin []
The Type II module (F2) []
segment of fibronectin ,
four Type III modules []
tags
[Proteins] [fibronectin]Labels: acute phase, cell surface, coagulation, complement system, cytoskeleton, extracellular, fibrinolytic, fibronectin, FN, matrix
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Coagulation factors are synthesized by the liver and their production increases in response to pro-inflammatory cytokines released in the acute phase early in the inflammatory response, in particular:
Coagulation factors are synthesized by the liver and their production increases in response to pro-inflammatory cytokines released in the acute phase early in the inflammatory response, in particular:
