Receptor for neurturin. Mediates the NRTN-induced autophosphorylation and activation of the RET receptor. Also able to mediate GDNF signaling through the RET tyrosine kinase receptor. Participates in NRTN-induced 'Ser-727' phosphorylation of STAT3. Interacts with SORL1. Additional isoforms seem to exist. Neurons of the superior cervical and dorsal root ganglia, and adult brain and testis. Low level in the substantia nigra, spleen and adrenal gland (PubMed:9182803). Isoform 1, isoform 2 and isoform 3 are all expressed in brain, liver, ileum, spleen, heart and kidney (PubMed:9875703). In brain, isoform 1 is most abundant, isoform 2 slightly less and isoform 3 is lowest. No significant levels of isoform 1, isoform 2 or isoform 3 expression in testis (PubMed:12829325). Expressed at low level in the ventral mesencephalon at 14 dpc. Highly expressed in the developing dorsal root ganglia (PubMed:9182803). Isoform 1, isoform 2 and isoform 3 are all highly expressed in the late embryonic development (15 dpc and 17 dpc) (PubMed:12829325). Belongs to the GDNFR family. Truncated C-terminus. Truncated C-terminus. Truncated C-terminus. Truncated C-terminus.