Methylprednisolone (MPD) is a synthetic glucocorticoid drug used in treatment of many neurological diseases and neurotraumas, including spinal cord injuries. Little is known of the mechanism of MPD in neuronal cells, particularly the genetic expression aspect. DD-PCR was used in identification of genes expressed during MPD treatment of PC12 cells. We have isolated 3 predicted up- or down-regulated genes, which are differentially expressed in neurons by MPD. One of these genes, USP16 (ubiquitin specific protease 16), is the deubiquitinating enzyme that is up-regulated by MPD in neurons. In order to observe the effect of MPD on USP16 gene expression, PC12 cells were treated under several experimental conditions, including endoplasmic reticulum stress drugs. We have isolated the total RNAs in PC12 cells and detected USP16 and ER related genes by RT-PCR. Because its expression pattern is similar to expression of ER chaperons, USP16 gene expression is strongly associated with unfolded protein response. A meaningful negative effect on each tissue treated by methylprednisolone is not shown in vivo. USP16 gene expression is suppressed by LY294002 (phosphatidylinositol 3-kinase inhibitor), which suggests that USP16 gene expression is regulated by the phosphatidylinositol 3-kinase pathway.