Expression of GFR alpha 1 receptor splicing variants with different biochemical properties is modulated during kidney development

The glial cell line-derived neurotrophic factor (GDNF) family coreceptor alpha1 (GFRalpha1) is a critical component of the RET receptor kinase signal-transducing complex. The activity of this multicomponent receptor is stimulated by the glial cell line-derived neurotrophic factor (GDNF) and is involved in neuronal cells survival and kidney development. GFRalpha1 pre-mRNA is alternatively spliced and produces two isoforms: GFRalpha1a, which includes the exon 5; and GFRalpha1b, which excludes it. Here we show that the Gfralpha1a isoform is predominantly expressed in neuronal tissues and in PC 12 cells differentiated toward a neuronal phenotype. GFRalpha1 splicing is also regulated during kidney development, GFRalpha1a is the minor isoform before birth and then rapidly becomes the major form after birth. We established cell lines expressing either GFRalpha1 isoforms and demonstrated that the GFRalpha1b isoform binds GDNF more efficiently than GFRalpha1a. Consistently, GFRalpha1b promotes a stronger RET phosphorylation than GFRalpha1a. These results indicate that specific inclusion of the GFRalpha1 exon 5 in neuronal tissues or during kidney development may alter the binding properties of GDNF to GFRalpha1, and thus could constitute an additional regulatory mechanism of the RET signaling pathway.