Glial Cell Line-Derived Neurotrophic Factor Family Receptor α-1 (GDNFRα1) is a glycosylphosphatidylinositol (GPI) linked cell surface protein belonging to GDNF-family receptor α subtype which consists of at least four members. GFRα1and GFRα2 are the cognate co-receptor for the neurotrophic factor neurturin mediating the NRTN-induced autophosphorylation and activation of the RET tyrosine kinase receptor. Soluble GFRαs released enzymatically from the cell surface by phosphatidylinositol phospholipase C, as well as recombinantly produced soluble GFRα1, can also bind with high affinity to GDNF and trigger the activation of Ret tyrosine kinase. Human GFRα1 shares 93% amino acid identity with mouse GFRα1.The expression of the various GFRαs are differentially regulated in the central and peripheral nervous system, suggesting complementary roles for the GFRαs in mediating the activities of the GDNF family of neurotrophic factors.