The present results show that the expression of Growth Arrest Specific1 (Gas1) in SH-SY5Y neuroblastoma cells significantly inhibits the increased phosphorylation of tyrosine 1062 of the Ret receptor tyrosine kinase induced by glial-cell-line-derived neurotrophic factor (GDNF). We also observed that Gas1 significantly reduces the activation of Akt. GDNF and members of its family of ligands (GFLs), signal through a molecular complex consisting of one of its receptors (GFRalphas) and the Ret receptor tyrosine kinase. GDNF is a key component to preserve several cell populations in the nervous system, including dopaminergic and motor neurons, and also participates in the survival and differentiation of peripheral neurons such as enteric, sympathetic and parasympathetic. On the other hand, Gas1 is a molecule involved in cell arrest that can induce apoptosis when over-expressed in different cell lines, including cells of neuronal and glial origin. Although, Gas1 is widely expressed during development, its role in vivo has not yet been clearly defined. We recently showed the structural homology between Gas1 and GFRalphas, thus suggesting that the physiological role of Gas1 is that of modulating the biological responses induced by GDNF and/or other members of this family of signaling molecules. The results of this work are consistent with the hypothesis of Gas1 acting as a negative modulator of GDNF signaling.