胶质细胞源性神经营养因子(GDNF) (Lin et al. 1993)和神经蛋白(NRTN) (Kotzbauer et al. 1996)是GDNF家族受体- α (GFRA) 1和2的配体(Jing et al. 1996, 1997, Creedon et al. 1997, Baloh et al. 1997)。尽管在体外存在交叉激活,但GDNF优先通过RET作用:GFRA1 (Schuchardt et al. 1994, Moore et al. 1996, Pichel et al. 1996, Sanchez et al. 1996, Calcano et al. 1998, Endomoto et al. 1998,而NRTN优先通过RET作用:GFRA2 (Heuckeroth et al. 1999, Rossi et al. 1999, Luo et al. 2004, 2009, Lindfors et al. 2006)。