involvement of glyceraldehyde3phosphate dehydrogenase gapdh and p53 in neuronal apoptosis evidence that gapdh is upregulated by p53 we recently reported that cytosine arabinoside aracinduced apoptosis of cerebellar neurons involves the overexpression of glyceraldehyde3phosphate dehydrogenase gapdh the present study was undertaken to investigate whether p53 andor bax overexpression participates in the aracinduced apoptosis of cerebellar granule cells and if so the relationship between p53 induction and gapdh overexpression in these cells aracinduced apoptosis of cerebellar granule cells was preceded by an increase in levels of p53 mrna and protein detected between 1 and 8 hr after treatment the mrna level for a p53 target gene bax was also increased the increase in gapdh mrna lasted longer than that of either p53 or bax and the level of gapdh protein in the particulate fraction increased after induction of gapdh mrna the antisense oligonucleotide to p53 protected granule cells from aracinduced chromatin condensation internucleosomal cleavage and apoptotic death the inhibition of p53 expression by the p53 antisense oligonucleotide not only blocked the expression of bax but also partially suppressed the increased gapdh mrna and protein levels conversely the suppression of gapdh expression and subsequent attenuation of apoptosis of granule cells by gapdh antisense oligonucleotide did not influence the expression of p53 or bax cerebellar granule cells prepared from p53 knockout mice were resistant to arac toxicity and the p53 gene knockout suppressed aracupregulated gapdh expression moreover infection of pc12 cells with an adenoviral vector containing p53 gene dramatically increased gapdh expression and triggered cell apoptosis these results suggest that aracinduced apoptosis of cerebellar granule cells involves the expression of both gapdh and p53 and that similar to bax gapdh is upregulated by p53 after exposure to the apoptotic insult