Xaliproden (SR57746A) induces 5-HT1A receptor-mediated MAP kinase activation in PC12 cells

Neurotrophic growth factors are involved in cell survival. However, natural growth factors have a very limited therapeutic use because of their short half-life. In the present study, we investigated the mechanism of action of a non-peptidic neurotrophic drug, Xaliproden, a potential molecule for the treatment of motoneuron diseases, since the transduction pathways of this synthetic 5-HT1A agonist are very poorly understood. Xaliproden does not activate the Trk receptor but causes a rapid increase in the activities of the ERK1 and ERK2 isoforms of MAP kinase, which then rapidly decrease to the basal level. We demonstrate that isoforms of the SHC adapter protein are phosphorylated independently of each other and are probably not the source of the Xaliproden-induced MAP kinases activation. The inhibitor of Ras farnesylation, FPT-1, and the protein kinase C inhibitors, GF 109203X and chelerythrine, inhibited the Xaliproden-induced MAP kinase activation, suggesting p21Ras and PKC involvement. Moreover, the observations that the 5-HT1A antagonist, pindobind, and pertussis toxin abolished the Xaliproden-induced ERK stimulation suggested that Xaliproden activates the MAP kinase pathways by stimulating the G protein-coupled receptor, 5-HT1A. These results demonstrate clearly that the non-peptidic compound, Xaliproden, exerts its neurotrophic effects through a mechanism of action differing from that of neurotrophins. These findings suggest that this compound does not involve MAPK activation by TrkA receptor stimulation but acts by MAP kinase pathway by a pertussis toxin-sensitive mechanism involving 5-HT1A receptors, p21 Ras and MEK-1 and by PKC and Akt pathways.