FGFR-1

FGFR1, also known as Fms-related tyrosine kinase 2 (FLT2), is a receptor tyrosine kinase that binds multiple FGF ligands, notably FGF1, FGF2 and FGF8, in complexes with heparan sulfate proteoglycans or Klotho co-receptors. Alternative splicing of the third immunoglobulin-like domain generates IIIb and IIIc variants that dictate ligand specificity, and FGFR1 signals mainly through the mesenchymal IIIc form. Ligand-induced dimerization activates downstream RAS-MAPK, PI3K-Akt and PLCγ pathways controlling proliferation, migration and development. FGFR1 is essential for mesoderm, limb and brain patterning; loss-of-function mutations cause Kallmann syndrome while gain-of-function changes underlie Pfeiffer syndrome. FGFR1 amplification occurs in breast and squamous lung cancers, making it an oncology target.