Glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) comprise a
family of TGF-beta-related neurotrophic factors (TRNs), which have trophic influences
on a variety of neuronal populations. A receptor complex comprised of TrnR1 (GDNFR
alpha) and Ret was recently identified and found to be capable of mediating both GDNF
and NTN signaling. We have identified a novel receptor based on homology to TrnR1,
called TrnR2, that is 48% identical to TrnR1, and is located on the short arm of chromosome
8. TrnR2 is attached to the cell surface via a GPI-linkage, and can mediate both NTN
and GDNF signaling through Ret in vitro. Fibroblasts expressing TrnR2 and Ret are
approximately 30-fold more sensitive to NTN than to GDNF treatment, whereas those
expressing TrnR1 and Ret respond equivalently to both factors, suggesting the TrnR2-Ret
complex acts preferentially as a receptor for NTN. TrnR2 and Ret are expressed in
neurons of the superior cervical and dorsal root ganglia, and in the adult brain.
Comparative analysis of TrnR1, TrnR2, and Ret expression indicates that multiple receptor
complexes, capable of mediating GDNF and NTN signaling, exist in vivo.