NF kappa B is a critical determinant in NMDA receptor mediated neuroprotection

One of the molecular mechanisms of NMDA receptor-mediated neuroprotection involves the release of brain-derived neurotrophic factor (BDNF) and activation of its cognate trkB receptor on cerebellar granule cells via an autocrine mechanism. Subsequent events leading to neuroprotection are not clear. At least four promoters are active in the rat BDNF gene. Two of these contain at least one Nuclear Factor kappa B (NF- B) candidate sequence in their 5′ flanking regions. We sought to determine the role of NF- B in NMDA receptor-mediated neuroprotection. Exposure of rat cerebellar granule cells to 100 M NMDA activated a specific DNA binding activity using a rat BDNF gene-derived DNA target. Induction of NF- B DNA binding activity was blocked by the NMDA receptor MK-801. Incubation of nuclear extracts with either anti-p65 antibody or anti-p50 antibody "supershifted" the DNA binding activity, suggesting that the DNA-protein complex was composed of p65 and p50 subunits. NMDA receptor-mediated neuroprotection was blocked when cerebellar granule cells were transfected with a double stranded oligonucleotide containing the BDNF gene NF- B sequence. Furthermore, nuclear extracts prepared from NMDA-treated, and the double stranded NF- B oligonucleotide showed reduced DNA binding activity to the target sequence. Taken together, these results support the idea that NF-kB is part of the survival pathway for NMDA receptor- mediated neuroprotection and that NF-kB may be involved in the transcriptional activation of the BDNF gene.