Glial Cell-Derived Neurotrophic Factor (GDNF)
A neurotrophic factor that promotes survival of dopaminergic neurons and motor neurons. GDNF deficiency is implicated in Parkinson's disease and motor neuron disease. Delivery of GDNF to the brain (bypassing the BBB) is an active area of peptide and gene therapy research.
Technical Context
GDNF (134 amino acids, dimeric) is the most potent known survival factor for dopaminergic neurons — the neurons whose degeneration causes Parkinson's disease. GDNF signals through GFRα1 co-receptor → RET receptor tyrosine kinase → PI3K/Akt and MAPK survival pathways. Therapeutic development has been challenging: GDNF does not cross the BBB (requiring direct brain delivery), clinical trials of intraputamenal GDNF infusion in Parkinson's disease showed mixed results (possible efficacy confounded by delivery inconsistencies, placebo effects, and anti-GDNF antibody formation), and gene therapy approaches (AAV2-GDNF) are in clinical trials. GDNF also supports motor neurons (relevant to ALS research), enteric neurons (relevant to gut motility), and kidney development. The GDNF story illustrates both the therapeutic promise and the delivery challenges of neurotrophic factor-based therapies.