Neuronal Ca2+‐dependent activator protein 1 (NCDAP1) induces neuronal cell death by activating p53 pathway following traumatic brain injury

Overactivation of N-methyl-d-aspartate glutamate receptors (NMDARs) after traumatic brain injury (TBI) contributes to excitotoxic cell death. The hyperactivation of NMDARs results in toxic levels of intracellular Ca(2+) and in the activation of p53-mediated apoptosis pathway. Neuronal Ca(2+) -dependent activator protein 1 (NCDAP1) was identified as an epileptogenic gene of unknown function in our laboratory. In this study, we investigated the expression and cellular localization of NCDAP1 in rat models of fluid percussion-induced TBI. NCDAP1 expression increased in the ipsilateral cortex and hippocampus adjacent to the lesion of the TBI rats compared with that in the sham-operated controls. In addition, NCDAP1 was co-expressed with neuronal marker (NeuN), and the results of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining suggest that NCDAP1 is involved in neuronal apoptosis that occurs after brain injury. In addition, the expression levels of p53, Bax, and active caspase-3 correlated with those of NCDAP1. To further investigate the function of NCDAP1, primary cultured neurons were employed to establish an apoptosis model. The expression of NCDAP1 was induced by NMDA-induced Ca(2+) influx, and the knockdown of NCDAP1 by siRNA decreased apoptosis caused by treatment with NMDA. Silencing of NCDAP1 also reduced p53 expression, whereas the over-expression of NCDAP1 induced cell death and up-regulated the expression of p53. The inhibition of p53 with pifithrin alpha or siRNA counteracted the effects of NCDAP1. Based on our data, we suggest that NCDAP1 plays an important role in p53-mediated neuronal apoptosis following TBI.