Post-translational modification of Fibroblast Growth Factor 23.

Fibroblast Growth Factor (FGF) 23 has been shown to play important roles in the development of hypophosphatemic rickets/osteomalacia. Complementary DNA predicts that the FGF23 protein is composed of 251 amino acids and N-terminal 24 amino acids seem to be a signal peptide. In vitro experiments indicate that a part of the FGF23 protein is processed between arginine179 and serine180. When full-length, N-terminal and C-terminal processed fragments of FGF23 were injected into mice, only the full-length FGF23 reduced serum phosphate levels indicating that the processing of FGF23 abolished its effect to cause hypophosphatemia. This processing was shown to be prevented by an inhibitor of furin indicating that the cleavage is mediated by subtilisin-like proprotein convertase. In addition to this processing, FGF23 protein seems to have O-linked glycosylation. Further studies are necessary to clarify the importance of O-glycosylation for FGF23 activity.