GSK3B and Parkinson disease: To further prove that the phosphorylation of SIRT2 by GSK3β does participate in 6-OHDA-induced SH-SY5Y cell death and that overactivated SIRT2 aggravates PD (Outeiro et al., 2007), we constructed two mutants, GFP-SIRT2SA and GFP-SIRT2-SD, to mimic dephosphorylation and phosphorylation, respectively (Figure 4A).