GFRA2

GFRA2 is a GPI-anchored cell-surface co-receptor that mediates neurotrophic factor signaling by preferentially binding neurturin and recruiting the RET receptor tyrosine kinase to assemble an active signaling complex (PMID:9182803). Reconstitution in cells co-expressing GFRA2 and RET shows the complex responds to both neurturin and GDNF but is roughly 30-fold more sensitive to neurturin, establishing GFRA2 as the preferred neurturin co-receptor (PMID:9182803). The crystal structure of the neurturin–GFRA2 complex resolves a three-domain architecture in which domain 1 makes no direct contact with neurturin but presents a conserved surface positioned to engage RET and/or NCAM, and identifies heparan sulfate-binding sites on both neurturin and GFRA2 that contribute to assembly and to avidity-driven modulation of functional ligand affinity by GFRA2 surface concentration (PMID:29414779). Beyond the canonical RET pathway, GFRA2 marks cardiac progenitor cells and drives cardiomyocyte differentiation through a RET-independent route (PMID:27396331), and in pancreatic cancer cells neurturin-bound GFRA2 recruits RET to form a heterodimer that phosphorylates hexokinase 2 at Ser122, boosting its activity to enhance aerobic glycolysis and fuel tumor growth (PMID:39988080).

1. 1997 High

   Established that GFRA2 is the molecular co-receptor that confers neurturin responsiveness on RET, resolving how this ligand activates the RET tyrosine kinase.

   Evidence In vitro signaling reconstitution in fibroblasts co-expressing TrnR2 (GFRA2) and RET, with ligand dose-response comparison and GPI-linkage characterization

   PMID:9182803

   Open questions at the time

   • Structural basis of GFRA2-RET assembly not resolved here
   • Does not address GFRA2 signaling independent of RET
   • Downstream signaling effectors not identified
2. 2016 Medium

   Revealed a RET-independent function for GFRA2, showing it marks cardiac progenitors and drives cardiomyocyte differentiation beyond the canonical neurturin/GDNF-RET axis.

   Evidence FACS isolation of GFRA2+ cardiac progenitors from mouse and human pluripotent stem cells with Gfra2 knockout and in vitro/in vivo differentiation readouts

   PMID:27396331

   Open questions at the time

   • Identity of the RET-independent signaling partner/transducer unknown
   • Ligand driving this pathway not defined
   • Single lab; mechanism downstream of GFRA2 uncharacterized
3. 2018 High

   Defined the structural architecture of the neurturin–GFRA2 complex and implicated heparan sulfate in complex assembly, explaining how GFRA2 surface density tunes functional ligand affinity.

   Evidence X-ray crystallography of NRTN alone and in complex with GFRA2, biophysical binding assays, heparan sulfate-binding mutagenesis, and in vivo pharmacokinetics with a binding mutant

   PMID:29414779

   Open questions at the time

   • Direct domain 1 contact with RET/NCAM inferred but not structurally captured
   • Full ternary GFRA2-NRTN-RET complex structure not solved
   • Functional consequence of avidity tuning in vivo not fully mapped
4. 2025 Medium

   Connected GFRA2-RET signaling to tumor metabolism by identifying hexokinase 2 Ser122 as a substrate, linking neurturin signaling to enhanced glycolysis in pancreatic cancer.

   Evidence Co-immunoprecipitation of the GFRA2-RET complex, in vitro kinase and HK2 activity assays, integrated metabolomics, and in vivo tumor models with neurturin blockade and RET inhibition

   PMID:39988080

   Open questions at the time

   • Whether RET directly phosphorylates HK2 versus via an intermediary kinase not fully resolved
   • Single lab; generality across cancer types untested
   • Reciprocal validation of the receptor complex limited

• The molecular identity and mechanism of the RET-independent GFRA2 signaling route remain undefined.
• No transducer identified for RET-independent signaling
• Ligand requirement for the cardiac differentiation pathway unknown
• No structure of the assembled GFRA2-NRTN-RET ternary complex