• Neurophilin;
  • FK506;
  • NGF;
  • neurite outgrowth
  • Nerve growth factor (NGF) and other members of the neurotrophin family are critical for the survival and differentiation of neurons within the peripheral and central nervous systems.

  • Neurophilin ligands, including FK506, potentiate NGF-induced neurite outgrowth in several experimental models, although the mechanism of this potentiation is unclear.

  • Therefore, we tested which signaling pathways were involved in FK506-potentiated neurite outgrowth in SH-SY5Y neuroblastoma cells using specific pharmacological inhibitors of various signaling molecules.

  • Inhibitors of Ras (lovastatin), Raf (GW5074), or MAP kinase (PD98059 and U0126) blocked FK506 activity, as did inhibitors of phospholipase C (U73122) and phosphatidylinositol 3′ kinase (LY294002).

  • Protein kinase C inhibitors (Go6983 and Ro31-8220) slightly but significantly inhibited neurite outgrowth, whereas inhibitors of p38 MAPK (SB203580) or c-Jun N-terminal kinase (SP600125) had no effect.

  • These data suggest that FK506 potentiates neurite outgrowth through the Ras/Raf/MAP kinase signaling pathway downstream of phospholipase C and phosphatidylinositol 3′ kinase.

British Journal of Pharmacology (2003) 140, 825–829. doi:10.1038/sj.bjp.0705522