PLK2 and Parkinson disease: In the treatment of protocatechuic aldehyde (PCA) to Parkinson’s disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), PLK2 inhibition or knockdown eliminates the protection of PCA to improve mitochondrial membrane potential (MMP), mitochondrial complex I activity and reactive oxygen species (ROS) level, while overexpression of PLK2 enhances the protection of PCA in PD model (76).