The present invention relates to nucleotide sequences, including expressed sequence tags (ESTs), oligonucleotide probes, polypeptides, vectors and host cells expressing, and immunoadhesions and antibodies to mammalian GFR.alpha.3, a novel .alpha.-subunit receptor of the GDNF (i.e. GFR) receptor family. It further relates to an assay for measuring activation of an .alpha.-subunit receptor by detecting tyrosine kinase receptor activation (i.e., autophosphorylation) or other activities related to ligand-induced .alpha.-subunit receptor homo-dimerization or homo-oligomerization.