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 GFR3, a novel -subunit receptor of the GDNF (i.e. GFR) receptor family. It further relates to an assay for measuring activation of an -subunit receptor by detecting tyrosine kinase receptor activation (i.e., autophosphorylation) or other activities related to ligand-induced -subunit receptor homo-dimerization or homo-oligomerization.