Mutations in DJ-1 cause familial Parkinson’s disease (PD). The expression pattern of DJ-1 in the brain remains controversial. In the present study, we used DJ-1 deficient mice as negative controls and examined DJ-1 mRNA expression in mouse brains. By sequential double labeling on the same sections, in situ hybridization of DJ-1 mRNA was followed by immunofluorescence detection for cell type markers. We found that DJ-1 mRNA was expressed in the majority of neurons in all brain areas examined. In particular, all dopamine neurons in the ventral midbrain expressed DJ-1 mRNA. Interestingly, the choroid plexus and ependymal cells lining the ventricles were the only non-neuronal regions strongly expressing DJ-1 mRNA. However, DJ-1 mRNA was not detected in astrocytes. DJ-1 mRNA expression in all nigra dopamine neurons but not in astrocytes suggests that its potential neuroprotective role could be cell-autonomous. The fact that DJ-1 expression is not restricted to substantia nigra dopamine neurons suggests that DJ-1 mutations may collaborate with other predisposing factors to cause the relatively selective dopamine neuron degeneration in Parkinson’s disease.

Rationale: Oxidative stress is a key contributor in chronic obstructive pulmonary disease (COPD) pathogenesis caused by cigarette smoking. NRF2, a redox-sensitive transcription factor, dissociates from its inhibitor, KEAP1, to induce antioxidant expression that inhibits oxidative stress.

Objectives: To determine the link between severity of COPD, oxidative stress, and NRF2-dependent antioxidant levels in the peripheral lung tissue of patients with COPD.

Methods: We assessed the expression of NRF2, NRF2-dependent antioxidants, regulators of NRF2 activity, and oxidative damage in non-COPD (smokers and former smokers) and smoker COPD lungs (mild and advanced). Cigarette smoke–exposed human lung epithelial cells (Beas2B) and mice were used to understand the mechanisms.

Measurements and Main Results: When compared with non-COPD lungs, the COPD patient lungs showed (1) marked decline in NRF2-dependent antioxidants and glutathione levels, (2) increased oxidative stress markers, (3) significant decrease in NRF2 protein with no change in NRF2 mRNA levels, and (4) similar KEAP1 but significantly decreased DJ-1 levels (a protein that stabilizes NRF2 protein by impairing KEAP1-dependent proteasomal degradation of NRF2). Exposure of Bea2B cells to cigarette smoke caused oxidative modification and enhanced proteasomal degradation of DJ-1 protein. Disruption of DJ-1 in mouse lungs, mouse embryonic fibroblasts, and Beas2B cells lowered NRF2 protein stability and impaired antioxidant induction in response to cigarette smoke. Interestingly, targeting KEAP1 by siRNA or the small-molecule activator sulforaphane restored induction of NRF2-dependent antioxidants in DJ-1–disrupted cells in response to cigarette smoke.

Conclusions: NRF2-dependent antioxidants and DJ-1 expression was negatively associated with severity of COPD. Therapy directed toward enhancing NRF2-regulated antioxidants may be a novel strategy for attenuating the effects of oxidative stress in the pathogenesis of COPD.

Mutations in PARKIN, pten-induced putative kinase 1 (PINK1), and DJ-1 are individually linked to autosomal recessive early-onset familial forms of Parkinson disease (PD). Although mutations in these genes lead to the same disease state, the functional relationships between them and how their respective disease-associated mutations cause PD are largely unknown. Here, we show that Parkin, PINK1, and DJ-1 formed a complex (termed PPD complex) to promote ubiquitination and degradation of Parkin substrates, including Parkin itself and Synphilin-1 in neuroblastoma cells and human brain lysates. Genetic ablation of either Pink1 or Dj-1 resulted in reduced ubiquitination of endogenous Parkin as well as decreased degradation and increased accumulation of aberrantly expressed Parkin substrates. Expression of PINK1 enhanced Parkin-mediated degradation of heat shock–induced misfolded protein. In contrast, PD-pathogenic Parkin and PINK1 mutations showed reduced ability to promote degradation of Parkin substrates. This study identified a functional ubiquitin E3 ligase complex consisting of PD-associated Parkin, PINK1, and DJ-1 to promote degradation of un-/misfolded proteins and suggests that their PD-pathogenic mutations impair E3 ligase activity of the complex, which may constitute a mechanism underlying PD pathogenesis.