GFRα-4 and the tyrosine kinase Ret form a functional receptor complex for persephin

Glial-cell-line derived neurotrophic factor (GDNF) [1], neurturin [2] and persephin [3] are structurally related, secreted proteins that are widely expressed in the nervous system and other tissues [1-5] and promote the survival of a variety of neurons during development [1-12], GDNF and neurturin signal through multicomponent receptors that consist of the net receptor tyrosine kinase and one of two structurally related glycosyl-phosphatidylinositol (GPI)-linked ligand-binding subunits: GFR alpha-1 is the preferred ligand-binding subunit for GDNF, and GFR alpha-2 is the preferred ligand-binding subunit for neurturin [13-21]. Two additional members of the GFR alpha family of GPI linked proteins have recently been cloned: GFR alpha-3 [21-23] and GFR alpha-4 [24], We have shown that persephin binds efficiently only to GFR alpha-4, and labelled persephin is effectively displaced from cells expressing GFR alpha-4 by persephin but not by GDNF or neurturin, Using microinjection to introduce expression plasmids into cultured neurons, we have also shown that coexpression of net with GFR alpha-4 confers a marked survival response to persephin but not to GDNF or neurturin, These results demonstrate that GFR alpha-4 is the ligand-binding subunit for persephin and that persephin, like GDNF and neurturin, also requires net for signalling.