Nitric oxide activation of TrkB through peroxynitrite

NIH-3T3 cells stably transfected with TrkB, the receptor for brain-derived neurotrophic factor (BDNF), were used to study the effects of NO and peroxy nitrite on TrkB. 3-Morpholinosydnonimine (SIN-I), a donor of NO and O-2(-) which immediately react to form peroxynitrite, induced TrkB tyrosine phosph orylation in a dose-dependent relationship from 2 to 40 mM, TrkB phosphoryl ation by SIN-I was blocked by superoxide dismutase, which convects O-2(-) t o H2O2 and prevents its reaction with NO to form peroxynitrite, and by K252 a, an inhibitor of TrkB phosphorylation by BDNF. Treatment with NO or O-2(- ) alone did not activate TrkB. Treatment directly with 1-4 mM peroxynitrite resulted-in a dose-dependent increase in tyrosine phosphorylation of TrkB. SIN-I treatment induced tyrosine phosphorylation of phospholipase C-gamma lf (PLC-gammal) and induced its binding with activated TrkB, similar to tha t seen with BDNF downstream signaling pathways. These studies demonstrate a ctivation of TrkB through peroxynitrite. NeuroReport 11:3593-3597 (C) 2000 Lippincott Williams & Wilkins.