FGFR-5 beta

Fibroblast growth factor receptor 5 (FGF R5), also known as FGRL1, is a 65 kDa transmembrane member of the FGF receptor family. Mature mouse FGF R5 consists of a 354 amino acid (aa) extracellular domain (ECD) with three immunoglobulinlike domains, a 21 aa transmembrane segment, and a 134 aa cytoplasmic domain. FGF R5 is distinct from other FGF receptor family members in that it does not contain a cytoplasmic tyrosine kinase domain. Within the ECD, mouse FGF R5 shares 94% and 98% aa sequence identity with human and rat FGF R5, respectively. Alternate splicing results in an isoform that lacks the first Ig-like domain. FGF R5 is widely expressed, and expression of two species of mRNA in cartilage and pancreas may indicate the presence of both splice forms. Both the full length and truncated isoforms of FGF R5 bind FGF basic; the full length form additionally binds to heparin. FGF R5 may function as a decoy receptor by binding FGF but not transducing its mitogenic signals.