Bovine FGF acidic/FGF1 Protein

FGF acidic, also known as FGF1, ECGF, and HBGF-1, is a 17 kDa nonglycosylated member of the FGF family of mitogenic peptides. FGF acidic, which is produced by multiple cell types, stimulates the proliferation of all cells of mesodermal origin and many cells of neuroectodermal, ectodermal, and endodermal origin. It plays a number of roles in development, regeneration, and angiogenesis (1-3). Bovine FGF acidic shares 53% amino acid sequence identity with FGF basic and 11%-31% with other bovine FGFs. It shares 92%, 91%, 88%, and 91% aa sequence identity with human, mouse, porcine, and rat FGF acidic, respectively, and exhibits considerable species crossreactivity. During its nonclassical secretion, FGF acidic associates with S100A13, copper ions, and the C2A domain of synaptotagmin 1 (4). It is released extracellularly as a disulfide-linked homodimer and is stored in complex with extracellular heparan sulfate (5). The ability of heparan sulfate to bind FGF acidic is determined by its pattern of sulfation, and alterations in this pattern during embryognesis thereby regulate FGF acidic bioactivity (6). The association of FGF acidic with heparan sulfate is a prerequisite for its subsequent interaction with FGF receptors (7, 8). Ligation triggers receptor dimerization, transphosphorylation, and internalization of receptor/FGF complexes (9). Internalized FGF acidic can translocate to the cytosol with the assistance of Hsp90 and then migrate to the nucleus by means of its two nuclear localization signals (10-12). The phosphorylation of FGF acidic by nuclear PKC delta triggers its active export to the cytosol where it is dephosphorylated and degraded (13, 14). Intracellular FGF acidic functions as a survival factor by inhibiting p53 activity and proapoptotic signaling (15).