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Fibronectin
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<p>Fibronectin is a high-<a href="/facts/Molecular_weight/FWueGMed">molecular weight</a> (~500-~600 <a href="/facts/Dalton_(unit)/IMATU3vf">kDa</a>) <a href="/facts/Glycoprotein/bKPzzW7m">glycoprotein</a> of the <a href="/facts/Extracellular_matrix/kaHC5Ez8">extracellular matrix</a> that binds to <a href="/facts/Cell_membrane/vAXSD0DT">membrane</a>-spanning <a href="/facts/Receptor_proteins/tjTAC76a">receptor proteins</a> called <a href="/facts/Integrins/DNYUGbBp">integrins</a>. Fibronectin also binds to other extracellular matrix proteins such as <a href="/facts/Collagen/KsyAb72K">collagen</a>, <a href="/facts/Fibrin/BFar47y5">fibrin</a>, and <a href="/facts/Heparan_sulfate/hHBkfU1X">heparan sulfate</a> <a href="/facts/Proteoglycans/SFbGPK0R">proteoglycans</a> (e.g. <a href="/facts/Syndecans/5abdJ7WE">syndecans</a>). </p><p>Fibronectin exists as a <a href="/facts/Protein_dimer/c8LwFJPG">protein dimer</a>, consisting of two nearly identical <a href="/facts/Monomers/Gw3CltMb">monomers</a> linked by a pair of <a href="/facts/Disulfide_bonds/eDx5Xtlg">disulfide bonds</a>. The fibronectin protein is produced from a single gene, but <a href="/facts/Alternative_splicing/nNRwPVNK">alternative splicing</a> of its <a href="/facts/Pre-mRNA/4UXtKPHw">pre-mRNA</a> leads to the creation of several <a href="/facts/Isoforms/oWmzfg4l">isoforms</a>. </p><p>Two types of fibronectin are present in <a href="/facts/Vertebrates/tT54FSTT">vertebrates</a>: </p> <ul><li>soluble plasma fibronectin (formerly called "cold-insoluble globulin", or CIg) is a major protein component of <a href="/facts/Blood_plasma/oHuwwugG">blood plasma</a> (300 μg/ml) and is produced in the <a href="/facts/Liver/Rtp4Fk2b">liver</a> by <a href="/facts/Hepatocytes/USpvDz1n">hepatocytes</a>.</li> <li>insoluble cellular fibronectin is a major component of the extracellular matrix. It is secreted by various <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a>, primarily <a href="/facts/Fibroblasts/n08KsFll">fibroblasts</a>, as a soluble <a href="/facts/Protein_dimer/c8LwFJPG">protein dimer</a> and is then assembled into an insoluble matrix in a complex cell-mediated process.</li></ul> <p>Fibronectin plays a major role in <a href="/facts/Cell_adhesion/Vg4alzxb">cell adhesion</a>, <a href="/facts/Cell_growth/wbArMaJU">growth</a>, <a href="/facts/Cell_migration/5ySAMquQ">migration</a>, and <a href="/facts/Cellular_differentiation/bCVqUG7w">differentiation</a>, and it is important for processes such as <a href="/facts/Wound_healing/3NlzV5Qn">wound healing</a> and <a href="/facts/Embryonic_development/1lFY4EoW">embryonic development</a>. Altered fibronectin <a href="/facts/Gene_expression/alCPohLR">expression</a>, <a href="/facts/Protein_degradation/GtQdv6J7">degradation</a>, and organization has been associated with a number of <a href="/facts/Pathologies/U9b18LJG">pathologies</a>, including cancer, arthritis, and <a href="/facts/Fibrosis/VVSmVgr3">fibrosis</a>. </p>