The keratinocyte growth factor (KGF), also known as FGF7 , is a growth factor present in the epithelialization-phase of wound healing. In this phase, keratinocytes are covering the wound, forming the epithelium.
KGF is a small signaling molecule that binds to fibroblast growth factor receptor 2b (FGFR2b). [1] For signalling to occur, a dimer is required between two FGF:FGFR complexes that is linked together by a molecule of heparin.
There are 23 known FGFs, and 4 FGF receptors. FGF:FGFR binding is complex and regulated by a variety of mechanisms in a tissue specific manner.
A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.
Paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance, as opposed to cell signaling by endocrine factors, hormones which travel considerably longer distances via the circulatory system; juxtacrine interactions; and autocrine signaling. Cells that produce paracrine factors secrete them into the immediate extracellular environment. Factors then travel to nearby cells in which the gradient of factor received determines the outcome. However, the exact distance that paracrine factors can travel is not certain.
Fibroblast growth factor 2, also known as basic fibroblast growth factor (bFGF) and FGF-β, is a growth factor and signaling protein encoded by the FGF2 gene. It binds to and exerts effects via specific fibroblast growth factor receptor (FGFR) proteins, themselves a family of closely related molecules. Fibroblast growth factor protein was first purified in 1975; soon thereafter three variants were isolated: 'basic FGF' (FGF2); Heparin-binding growth factor-2; and Endothelial cell growth factor-2. Gene sequencing revealed that this group is the same FGF2 protein and is a member of a family of FGF proteins.
Fibroblast growth factors (FGF) are a family of cell signalling proteins produced by macrophages; they are involved in a wide variety of processes, most notably as crucial elements for normal development in animal cells. Any irregularities in their function lead to a range of developmental defects. These growth factors typically act as systemic or locally circulating molecules of extracellular origin that activate cell surface receptors. A defining property of FGFs is that they bind to heparin and to heparan sulfate. Thus, some are sequestered in the extracellular matrix of tissues that contains heparan sulfate proteoglycans and are released locally upon injury or tissue remodeling.
Fibroblast growth factor 1, (FGF-1) also known as acidic fibroblast growth factor (aFGF), is a growth factor and signaling protein encoded by the FGF1 gene. 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. Gene sequencing revealed that this group was actually the same growth factor and that FGF1 was a member of a family of FGF proteins.
Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins. Receptor tyrosine kinases have been shown not only to be key regulators of normal cellular processes but also to have a critical role in the development and progression of many types of cancer. Mutations in receptor tyrosine kinases lead to activation of a series of signalling cascades which have numerous effects on protein expression. Receptor tyrosine kinases are part of the larger family of protein tyrosine kinases, encompassing the receptor tyrosine kinase proteins which contain a transmembrane domain, as well as the non-receptor tyrosine kinases which do not possess transmembrane domains.
The fibroblast growth factor receptors (FGFR) are, as their name implies, receptors that bind to members of the fibroblast growth factor (FGF) family of proteins. Some of these receptors are involved in pathological conditions. For example, a point mutation in FGFR3 can lead to achondroplasia.
Fibroblast growth factor receptor 2 (FGFR2) also known as CD332 is a protein that in humans is encoded by the FGFR2 gene residing on chromosome 10. FGFR2 is a receptor for fibroblast growth factor.
Fibroblast growth factor receptor 1 (FGFR1), also known as basic fibroblast growth factor receptor 1, fms-related tyrosine kinase-2 / Pfeiffer syndrome, and CD331, is a receptor tyrosine kinase whose ligands are specific members of the fibroblast growth factor family. FGFR1 has been shown to be associated with Pfeiffer syndrome, and clonal eosinophilias.
Fibroblast growth factor receptor 3 is a protein that in humans is encoded by the FGFR3 gene. FGFR3 has also been designated as CD333. The gene, which is located on chromosome 4, location q16.3, is expressed in tissues such as the cartilage, brain, intestine, and kidneys.
Heparin-binding EGF-like growth factor (HB-EGF) is a member of the EGF family of proteins that in humans is encoded by the HBEGF gene.
Fibroblast growth factor receptor 4 is a protein that in humans is encoded by the FGFR4 gene. FGFR4 has also been designated as CD334.
Keratinocyte growth factor is a protein that in humans is encoded by the FGF7 gene.
Fibroblast growth factor 10 is a protein that in humans is encoded by the FGF10 gene.
Glia-activating factor is a protein that in humans is encoded by the FGF9 gene.
Fibroblast growth factor 4 is a protein that in humans is encoded by the FGF4 gene.
Fibroblast growth factor 5 is a protein that in humans is encoded by the FGF5 gene.
Fibroblast growth factor 19 is a protein that in humans is encoded by the FGF19 gene. It functions as a hormone, regulating bile acid synthesis, with effects on glucose and lipid metabolism. Reduced synthesis, and blood levels, may be a factor in chronic bile acid diarrhea and in certain metabolic disorders.
Sulfatase 1, also known as SULF1, is an enzyme which in humans is encoded by the SULF1 gene.
Fibroblast growth factor 21 is a liver-secreted peptide hormone that in humans is encoded by the FGF21 gene. Together with FGF19 and FGF23, this protein is a member of the endocrine subgroup within the fibroblast growth factor (FGF) family. FGF21 is a potent, extracellularly acting metabolic regulator, whose action was discovered through in vitro phenotypic screening and diet manipulation studies in rodents., unlike canonical growth-stimulating FGFs known to stimulate mitosis, differentiation and angiogenesis in their target tissues, FGF21 exerts its action by activating FGF21 receptors located in the cell membrane of target cells. Each FGF21 receptor is composed of a transmembrane FGF receptor protein, and its complexing co-receptor β-Klotho. Loss of β-Klotho abolishes all effects of FGF21 in vitro and in vivo. In addition to its action as a hormone, FGF21 may be able to act in an autocrine fashion, or possibly also in a paracrine manner in the pancreas.