Glial cell line-derived neurotrophic factor (GDNF) plays key roles in the control of vertebrate neuron survival and differentiation. A novel neurotrophic factor was recently cloned from human and mouse and designated neurturin. Physiological responses to neurturin (NTN) require the presence of receptor tyrosine kinase RET and a novel glycosylphosphatidylinositol linked receptor NTNRalpha. The cDNAs encoding NTNRalpha from human, rat, chicken, and mouse have been cloned recently and termed GDNFRβ, Ret ligand 2 (RETL2) or TGF-beta-related neurotrophic factor receptor 2 (TrnR2) and nominated as GFRα-2 recently. NTN binds to and forms a complex with GFRα-2 and the Ret PTK and activates the RET receptor tyrosine kinase pathway. Both NTN and GDNF can activate the MAP kinase and phosphatidylinositol 3-kinase pathways and play a critical role in the development of many neuronal populations. Neurturin and GDNF define a new family of neurotrophic factors.
