FGF1, also known as acidic fibroblast growth factor (aFGF), is a growth factor and signaling protein encoded by the FGF1gene.[1][2] It is synthesized as a 155 amino acid polypeptide, whose mature form is a non-glycosylated 17-18 kDa protein. Fibroblast growth factor protein was first purified in 1975, but soon afterwards others using different conditions isolated acidic FGF, Heparin-binding growth factor-1, and Endothelial cell growth factor-1.[3] Gene sequencing revealed that this group was actually the same growth factor and that FGF1 was a member of a family of FGF proteins.
FGF-1 has no definitive signal sequence and thus is not secreted through classical pathways, but it does appear to form a disulfide linked dimer inside cells that associate with a complex of proteins at the cell membrane (including S100A13 and Syt1) which then help flip it through the membrane to the exterior of the cell.[4][5] Once in the reducing conditions of the surrounding tissue, the dimer dissociates into monomeric FGF1 that can enter systemic circulation or be sequestered in tissues binding to heparan sulfate proteoglycans of the extracellular matrix. FGF1 can then bind to and exert its effects via specific fibroblast growth factor receptor (FGFR) proteins which themselves constitute a family of closely related molecules.[6]
In addition to its extracellular activity, FGF1 can also function intracellularly. The protein has a nuclear localization sequence (NLS) but the route that FGF1 takes to get to the nucleus is unclear and it appears that some sort of cell surface receptor binding is necessary, followed by its internalization and translocation to the nucleus whereupon it can interact with nuclear isoforms of FGFRs.[6] This is different from FGF2 which also can activate nuclear FGFRs but has splicing variants of the protein that never leave the cell and go directly to the nucleus.
FGF family members possess broad mitogenic and cell survival activities, and are involved in a variety of biological processes, including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion. This protein functions as a modifier of endothelial cell migration and proliferation, as well as an angiogenic factor. It acts as a mitogen for a variety of mesoderm- and neuroectoderm-derived cells in vitro, thus is thought to be involved in organogenesis. Three alternatively spliced variants encoding different isoforms have been described.[7]
FGF1 is multifunctional with many reported effects. For one example, in mice with diet-induced diabetes that is an experimental equivalent of type 2 diabetes in humans, a single injection of the FGF1 protein is enough to restore blood sugar levels to a healthy range for > 2 days.[8]
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↑Pellegrini L, Burke DF, von Delft F, Mulloy B, Blundell TL (October 2000). "Crystal structure of fibroblast growth factor receptor ectodomain bound to ligand and heparin". Nature. 407 (6807): 1029–34. doi:10.1038/35039551. PMID11069186.
↑Chellaiah A, Yuan W, Chellaiah M, Ornitz DM (December 1999). "Mapping ligand binding domains in chimeric fibroblast growth factor receptor molecules. Multiple regions determine ligand binding specificity". The Journal of Biological Chemistry. 274 (49): 34785–94. doi:10.1074/jbc.274.49.34785. PMID10574949.
↑Loo BB, Darwish KK, Vainikka SS, Saarikettu JJ, Vihko PP, Hermonen JJ, Goldman AA, Alitalo KK, Jalkanen MM (May 2000). "Production and characterization of the extracellular domain of recombinant human fibroblast growth factor receptor 4". The International Journal of Biochemistry & Cell Biology. 32 (5): 489–97. doi:10.1016/S1357-2725(99)00145-4. PMID10736564.
↑Kan M, Wu X, Wang F, McKeehan WL (May 1999). "Specificity for fibroblast growth factors determined by heparan sulfate in a binary complex with the receptor kinase". The Journal of Biological Chemistry. 274 (22): 15947–52. doi:10.1074/jbc.274.22.15947. PMID10336501.
↑ 19.019.1Mouta Carreira C, LaVallee TM, Tarantini F, Jackson A, Lathrop JT, Hampton B, Burgess WH, Maciag T (August 1998). "S100A13 is involved in the regulation of fibroblast growth factor-1 and p40 synaptotagmin-1 release in vitro". The Journal of Biological Chemistry. 273 (35): 22224–31. doi:10.1074/jbc.273.35.22224. PMID9712836.
↑Landriscina M, Bagalá C, Mandinova A, Soldi R, Micucci I, Bellum S, Prudovsky I, Maciag T (July 2001). "Copper induces the assembly of a multiprotein aggregate implicated in the release of fibroblast growth factor 1 in response to stress". The Journal of Biological Chemistry. 276 (27): 25549–57. doi:10.1074/jbc.M102925200. PMID11432880.
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1jt5: Human Acidic Fibroblast Growth Factor. 141 Amino Acid Form with Amino Terminal His Tag AND LEU 73 REPLACED BY VAL AND VAL 109 REPLACED BY LEU (L73V/V109L)
1jt7: Human Acidic Fibroblast Growth Factor. 141 Amino Acid Form with Amino Terminal His Tag AND LEU 44 REPLACED BY PHE AND LEU 73 REPLACED BY VAL AND VAL 109 REPLACED BY LEU (L44F/L73V/V109L)
1m16: Human Acidic Fibroblast Growth Factor. 141 Amino Acid Form with Amino Terminal His Tag and Leu 44 Replaced with Phe (L44F), Leu 73 Replaced with Val (L73V), Val 109 Replaced with Leu (V109L) and Cys 117 Replaced with Val (C117V).
