Neurotrophic factor that enhances survival and morphological differentiation of dopaminergic neurons and increases their high-affinity dopamine uptake. May also modulate local neuronal effects in distal regions of the motor neuron. Homodimer; disulfide-linked (PubMed:8493557). 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, including the kidney, lung, bone, heart, liver, spleen, sciatic nerve and blood (PubMed:7696586). Expressed in brain (at protein level) (PubMed:21994944). Localizes at the proximal ligature of the hypoglossal nerve (PubMed:10828539). By melatonin. Belongs to the TGF-beta family. GDNF subfamily.