Fibroblast growth factor (FGF) was initially discovered in pituitary extracts in 1973, and then isolated from the brain and pituitary gland. Due to the fibroblast stimulating activities of those isolated factors, scientists described them as "FGFs". Since FGF1 was isolated at acidic pH, it was firstly named "acidic fibroblast growth factor". While FGF2 was originally isolated at basic pH and named "basic fibroblast growth factor". At present, fibroblast growth factors (FGFs) are known as a large family of growth factors that exist in organisms ranging from nematodes to humans, and some of these factors even cannot simulate fibroblasts. The "FGFs" is used to indicate that these proteins are structurally related.
In vertebrates, 22 members of the FGF family are identified, of which the molecular mass is 17-34 kDa and the amino acid identity is 13-71%. Between vertebrate species, both gene structure and amino-acid sequence of FGFs are highly conserved. FGFs can bind to the heparan sulfate proteoglycans (HPSGs) of host cell with high affinity, and they can interact with heparin-like glycosaminoglycans (HLGAGs) of the extracellular matrix (ECM). The formation of the FGF:FGFR:HPSG ternary complex induces the dimerization of FGFRs, which then results in the phosphorylation of the FGFRs at the intracellular tyrosine kinase domain. The signals are further mediated through RAS/MAP kinase pathway, PI3 kinase/AKT pathway, and PLCγ pathway, regulating biological functions such as cellular proliferation, survival, migration, and differentiation.
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