Glial Cell Line-Derived Neurotrophic Factor (GDNF) is a neurotrophic factor that is closely related to other neurotrophic factors, such as Neurturin, Persephin, and Artemin, by a common structural feature called the cysteine-knot. GDNF signals through a multicomponent system of receptors that includes RET and GFR alpha 1-4, to promote dopamine uptake, survival and differentiation of neurons. Recombinant GDNF is a non-glycosylated homodimer, containing two 135 amino acid chains, with a total molecular weight of 30.4 kDa