Fyn kinases play a critical role in neuronal apoptosis induced by oxygen and glucose deprivation or amyloid-β peptide treatment.

Aims Src family protein tyrosine kinases (SrcPTKs) have been implicated in the pathogenesis of brain ischemia and Alzheimer's disease (AD). In this study, we investigated whether Src and Fyn kinases, two major members of SrcPTKs in the brain, have distinct roles in the oxygen and glucose deprivation (OGD) and amyloid-beta peptide (A beta)-induced neuronal apoptosis. Methods and results The DAPI staining and caspase-3 activation analysis showed that small interfering RNAs (siRNAs) knockdown of Src or Fyn attenuated SH-SY5Y cells apoptosis after OGD and A beta treatment. Fyn knockdown had a more potent neuroprotective effect than Src knockdown, suggesting a principal pathological significance of Fyn in brain ischemia and AD. Previously, we reported that brain ischemia promotes the phosphorylation of postsynaptic density protein 95 (PSD-95) at tyrosine 523 (Y523), which is associated with postsynaptic mechanisms of excitotoxicity. Here, immunoblot analysis indicated that not only OGD but also A beta incubation increased the PSD-95Y523 phosphorylation. Src knockdown, especially Fyn knockdown, significantly inhibited such phosphorylation. Conclusion Fyn mediates PSD-95Y523 phosphorylation, which may be responsible for the excitotoxic signal cascades and neuronal apoptosis in brain ischemia and A beta neurotoxicity. Fyn is a potential therapeutic target for the treatment of ischemic stroke and AD.