Identification, expression and functional characterization of the GRAL gene.

The glial cell line-derived neurotrophic factor (GDNF) family is a group of neurotrophic factors with diverse biological functions. Members of the GDNF family exert their functions by interacting with a specific GDNF family receptor alpha (GFRalpha) and activation of the cRET. Here we report the identification and characterization of GDNF receptor-alpha-like (GRAL) gene. Sequence analysis indicated that GRAL is a distant homolog of the GFRalpha family, with 30% of its amino acid sequence identical to that of GFRalpha-3. There are two splice variants of GRAL: the full-length form (GRAL-A) represented by a 2080 bp mRNA and a short form (GRAL-B) represented by a 1833 bp mRNA. In adult mouse, GRAL transcripts have been found primarily in the CNS. In the developing mouse brain, the mRNA level of GRAL in the cerebrocortex and hippocampus reached a maximum at birth and declined afterwards. GRAL-A protein was localized predominantly in the plasma membrane. Overexpression of GRAL-A protected PC12 cells and cultured hippocampal neurons from serum starvation-induced cell apoptosis. The neuroprotective effect of GRAL was associated with marked inhibition of the Jun-N-terminal kinase signaling pathway. Our results suggest that GRAL belongs to a superfamily of GFRalpha and might take part in neuroprotection and brain development.