Characterization of two distinct monoclonal antibodies specific for glial cell line-derived neurotrophic factor

Here we report the generation and characterization of two distinct monoclonal antibodies, G-90 and B-1531, specific to glial cell line-derived neurotrophic factor (GDNF). ELISA results confirmed that G-90 and B-1531 both recognize GDNF. Western blots showed that G-90 recognized only the GDNF dimer, whereas B-1531 recognized both the monomer and dimer. Peptide competition ELISA (PCE) and BIAcore data suggested that G-90 and B-1531 recognize different epitopes: PCE confirmed that B-1531 binds to NH2-terminal peptides between amino acids 18 and 37, whereas G-90 does not; BIAcore data showed that B-1531 binds to the NH2 terminus of GDNF, whereas G-90 does not. G-90, in a concentration-dependent manner, completely neutralized the GDNF-induced increases of choline acetyltransferase in cultured motoneuron and of dopamine uptake and morphological differentiation in dopaminergic neuron cultures. B-1531 had no neutralizing effects. GDNF-induced Ret autophosphorylation in NGR-38 cells was completely neutralized by G-90, whereas B-1531 had a moderate effect. These data show that G-90 and B-1531 are specific antibodies to GDNF. The data also suggest that the NH2 terminus of GDNF is not critical for activity. Partial inhibition of Ret phosphorylation is insufficient to down-regulate GDNF-induced biological activity.