Neurturin and glial-cell-line-derived neurotrophic factor (GDNF) promote the survival and maintenance of different types of neuronal cells and signal through a receptor complex composed of a Iigand binding subunit, either GDNF family receptor alpha-1(GFR alpha-1) or alpha-2 (GFR Alpha alpha-2), together with the cRET membrane-bound protein tyrosine kinase. We have cloned GFR alpha-3. a novel receptor belonging to the GFR alpha family that is 35% identical by amino acid sequence to both GFR alpha-1 and GFR alpha-2, GFR alpha-3 is a protein composed of 400 amino acid residues with three potential N-linked gIycosylation sites together with the features characteristic of a glycosyl-phosphatidylinositol-anchored membrane protein, The hetrologous expression of a FLAG-tagged GFR alpha-3 in human embryonic kidney cells showed that the protein tagged is bound to the cell surface via a glycasyl-PtdIns anchor and is glycosylated, with different glycoforms migrating on SDS/PAGE with apparent molecular masses ranging over 43-62 kDa, The gene for GFR alpha-3 was mapped to human chromosome 5 in a region (q31.1-q31.3) where several disease loci, growth factor and growth factor receptor genes have been localized, Using northern blot analysis reverse-transcription PCR. GFR alpha-3 was shown to be expressed within the nervous system predominantly in the cerebellum and the spinal cord while in peripheral tissues GFR alpha-3 was found to be expressed mostly in the colon, small intestine, pancreas. heart. testis and prostate, Using a GFR alpha-3-specific [S-35]cRNA[gamma S] probe, in situ hybridization histochemistry experiments confirmed the expression in the cerebellum.
