Oxidative damage of DJ-1 is linked to sporadic Parkinson and Alzheimer diseases.

Mutations in DJ-1 cause an autosomal recessive, early onset familial form of Parkinson disease (PD). However, little is presently known about the role of DJ-1 in the more common sporadic form of PD and in other age-related neurodegenerative diseases, such as Alzheimer disease (AD). Here we report that DJ-1 is oxidatively damaged in the brains of patients with idiopathic PD and AD. By using a combination of two-dimensional gel electrophoresis and mass spectrometry, we have identified 10 different DJ-1 isoforms, of which the acidic isoforms (pI 5.5 and 5.7) of DJ-1 monomer and the basic isoforms (pI 8.0 and 8.4) of SDS-resistant DJ-1 dimer are selectively accumulated in PD and AD frontal cortex tissues compared with age-matched controls. Quantitative Western blot analysis shows that the total level of DJ-1 protein is significantly increased in PD and AD brains. Mass spectrometry analyses reveal that DJ-1 is not only susceptible to cysteine oxidation but also to previously unsuspected methionine oxidation. Furthermore, we show that DJ-1 protein is irreversibly oxidized by carbonylation as well as by methionine oxidation to methionine sulfone in PD and AD. Our study provides new insights into the oxidative modifications of DJ-1 and indicates association of oxidative damage to DJ-1 with sporadic PD and AD.