摘要Glial cell line-derived neurotrophic factor(GDNF)was originally recognized for its ability to promote survival of midbrain dopaminergic neurons,but it has since been demonstrated to be crucial for the survival and differentiation of many neuronal subpopulations,including motor neurons,sympathetic neurons,sensory neurons and enteric neurons.To identify possible effectors or regulators of GDNF signaling,we performed a yeast two-hybrid screen using the intracellular domain of RET,the common signaling receptor of the GDNF family,as bait.Using this approach,we identified RaplGAP,a GTPase-activating protein(GAP)for Rap1,as a novel RET-binding protein.Endogenous RaplGAP co-immunoprecipitated with RET in neural tissues,and RET and RaplGAP were co-expressed in dopaminergic neurons of the mesencephalon,in addition,overexpression of RaplGAP attenuated GDNF-induced neurite outgrowth,whereas suppressing the expression of endogenous RaplGAP by RNAi enhanced neurite outgrowth.Furthermore,using co-immunoprecipitation analyses,we found that the interaction between RET and RaplGAP was enhanced following GDNF treatment.Mutagenesis analysis revealed that Tyr981 in the intracellular domain of RET was crucial for the interaction with RapiGAP.Moreover,we found that RaplGAP negatively regulatedGNDFinduced ERK activation and neurite outgrowth.Taken together,our results suggest the involvement of a novel interaction of RET with Rap l GAP in the regulation of GDNF-mediated neurite outgrowth.