Neurotrophic factor that enhances survival and morphological differentiation of dopaminergic neurons and increases their high-affinity dopamine uptake. Homodimer; disulfide-linked (By similarity). Interacts with RET (By similarity). Interacts (via propeptide) with SORL1 (via N-terminal ectodomain), either alone or in complex with GFRA1; interaction with SORL1 affects GDNF-regulated, but not constitutive secretion (PubMed:21994944). Also interacts with SORL1 in complex with GFRA1; this interaction leads to GDNF endocytosis and lysosomal degradation (By similarity). Expressed in both the central nervous system (CNS) and in non-CNS tissues. Expressed in a highly dynamic pattern in the anterior neuroectoderm during the early stages of neurogenesis between 7.5 dpc and 10.5 dpc. Beginning at 10.5 dpc, expression begins in mesenchymal tissues of several organs including the digestive tract, kidney, testis, frontonasal mass, tooth primordium, tongue, mandible, whisker follicles, ear, eye, limb bud and in distinct regions of the brain. Also expressed in the heart, ileum, liver and muscle. First detected at 7.5 dpc, reaches its peak around 9.5 dpc and declines considerably after 10.5 dpc. Expression in C6 glioma cells was transiently induced by treatment with phorbol myristate acetate (PMA), but not by forskolin. Belongs to the TGF-beta family. GDNF subfamily.