PP2Ac demethylation is regulated by LCMT(a specific leucine carboxyl methyltransferase catalyzing methylation of PP2A)and PME(a specific methylesterase catalyzing demethylation of PP2A. Objective:The aim of the present study was to investigate the mechanism of Cel iridoid glycoside(CIG)on PP2A catalytic subunit C(PP2Ac). Methods:We used recombined lentivirus vector to deliver PME-1 genetic materials into N2a cells or transfected LCMT-1 siRNA into N2a cells to block the expression of LCMT-1. Twenty-four hours later,cells were rinsed twice with cold PBS(pH 7.4)and CIG at different concentrations(50,100,and 200 μg·mL-1,respectively)were added for 24 h. West blotting was used to PP2Ac、demethylaion/methylation PP2Ac、LCMT-1 and PME-1. The activity of PP2A was detected by a biochemical assay. Results:①Lentivirus transferred PME-1 was expressed at high level in the N2a cells after transduction. Correspondingly,the demethylation of PP2Ac was increasing and PP2A activity was decreasing after transduction. Treatment with CIG for 24 h reversed the increase of PME-1 and demethylation of PP2Ac without influencing LCMT-1 expression. PP2A activity was also significantly enhanced in CIG treatment group,compared with the cells after PME-1 transduction. ②LCMT-1 siRNA significantly decreased LCMT-1 expression. CIG did not affect LCMT-1expression. however,demethylation of PP2Ac is increased in siRNA-transfected cells and CIG could reversed the high demethylation of PP2Ac and PP2A activity. Conclusion:CIG increases methylation of PP2A subunit C by inhibiting PME-1.