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1.  Drp1 inhibition attenuates neurotoxicity and dopamine release deficits in vivo 
Nature Communications  2014;5:5244.
Mitochondrial dysfunction has been reported in both familial and sporadic Parkinson’s disease (PD). However, effective therapy targeting this pathway is currently inadequate. Recent studies suggest that manipulating the processes of mitochondrial fission and fusion has considerable potential for treating human diseases. To determine the therapeutic impact of targeting these pathways on PD, we used two complementary mouse models of mitochondrial impairments as seen in PD. We show here that blocking mitochondrial fission is neuroprotective in the PTEN-induced putative kinase-1 deletion (PINK1−/−) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse models. Specifically, we show that inhibition of the mitochondrial fission GTPase dynamin-related protein-1 (Drp1) using gene-based and small-molecule approaches attenuates neurotoxicity and restores pre-existing striatal dopamine release deficits in these animal models. These results suggest Drp1 inhibition as a potential treatment for PD.
Mitochondrial dysfunction has been associated with Parkinson’s disease but effective therapies targeting this pathway are yet to be developed. Here the authors show that inhibition of the mitochondrial fission protein Drp-1 using genetic or small-molecule approaches in mouse models of the disease, leads to improvements in the pathology.
PMCID: PMC4223875  PMID: 25370169
2.  Loss of PINK1 Attenuates HIF-1α Induction by Preventing 4E-BP1-Dependent Switch in Protein Translation under Hypoxia 
The Journal of Neuroscience  2014;34(8):3079-3089.
Parkinson's disease (PD) has multiple proposed etiologies with implication of abnormalities in cellular homeostasis ranging from proteostasis to mitochondrial dynamics to energy metabolism. PINK1 mutations are associated with familial PD and here we discover a novel PINK1 mechanism in cellular stress response. Using hypoxia as a physiological trigger of oxidative stress and disruption in energy metabolism, we demonstrate that PINK1−/− mouse cells exhibited significantly reduced induction of HIF-1α protein, HIF-1α transcriptional activity, and hypoxia-responsive gene upregulation. Loss of PINK1 impairs both hypoxia-induced 4E-BP1 dephosphorylation and increase in the ratio of internal ribosomal entry site (IRES)-dependent to cap-dependent translation. These data suggest that PINK1 mediates adaptive responses by activating IRES-dependent translation, and the impairments in translation and the HIF-1α pathway may contribute to PINK1-associated PD pathogenesis that manifests under cellular stress.
PMCID: PMC3931509  PMID: 24553947
4EBP; hypoxia; IRES; Parkinson's disease; PINK1; translation
3.  Global regulation of mRNA translation and stability in the early Drosophila embryo by the Smaug RNA-binding protein 
Genome Biology  2014;15(1):R4.
Smaug is an RNA-binding protein that induces the degradation and represses the translation of mRNAs in the early Drosophila embryo. Smaug has two identified direct target mRNAs that it differentially regulates: nanos and Hsp83. Smaug represses the translation of nanos mRNA but has only a modest effect on its stability, whereas it destabilizes Hsp83 mRNA but has no detectable effect on Hsp83 translation. Smaug is required to destabilize more than one thousand mRNAs in the early embryo, but whether these transcripts represent direct targets of Smaug is unclear and the extent of Smaug-mediated translational repression is unknown.
To gain a panoramic view of Smaug function in the early embryo, we identified mRNAs that are bound to Smaug using RNA co-immunoprecipitation followed by hybridization to DNA microarrays. We also identified mRNAs that are translationally repressed by Smaug using polysome gradients and microarrays. Comparison of the bound mRNAs to those that are translationally repressed by Smaug and those that require Smaug for their degradation suggests that a large fraction of Smaug’s target mRNAs are both translationally repressed and degraded by Smaug. Smaug directly regulates components of the TRiC/CCT chaperonin, the proteasome regulatory particle and lipid droplets, as well as many metabolic enzymes, including several glycolytic enzymes.
Smaug plays a direct and global role in regulating the translation and stability of a large fraction of the mRNAs in the early Drosophila embryo, and has unanticipated functions in control of protein folding and degradation, lipid droplet function and metabolism.
PMCID: PMC4053848  PMID: 24393533
4.  DJ-1 mRNA anatomical localization and cell type identification in the mouse brain 
Neuroscience letters  2009;465(3):214-219.
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.
PMCID: PMC2852142  PMID: 19766170
5.  Decline in NRF2-regulated Antioxidants in Chronic Obstructive Pulmonary Disease Lungs Due to Loss of Its Positive Regulator, DJ-1 
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.
PMCID: PMC2542433  PMID: 18556627
chronic obstructive pulmonary disease; NRF2; DJ-1; oxidative stress; antioxidants
6.  Parkin, PINK1, and DJ-1 form a ubiquitin E3 ligase complex promoting unfolded protein degradation 
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.
PMCID: PMC2648688  PMID: 19229105
7.  PINK1 Deficiency Attenuates Astrocyte Proliferation Through Mitochondrial Dysfunction, Reduced AKT and Increased p38 MAPK Activation, and Downregulation of EGFR 
Glia  2013;61(5):800-812.
PINK1 (PTEN induced putative kinase 1), a familial Parkinson's disease (PD)-related gene, is expressed in astrocytes, but little is known about its role in this cell type. Here, we found that astrocytes cultured from PINK1-knockout (KO) mice exhibit defective proliferative responses to epidermal growth factor (EGF) and fetal bovine serum. In PINK1-KO astrocytes, basal and EGF-induced p38 activation (phosphorylation) were increased whereas EGF receptor (EGFR) expression and AKT activation were decreased. p38 inhibition (SB203580) or knockdown with small interfering RNA (siRNA) rescued EGFR expression and AKT activation in PINK1-KO astrocytes. Proliferation defects in PINK1-KO astrocytes appeared to be linked to mitochondrial defects, manifesting as decreased mitochondrial mass and membrane potential, increased intracellular reactive oxygen species level, decreased glucose-uptake capacity, and decreased ATP production. Mitochondrial toxin (oligomycin) and a glucose-uptake inhibitor (phloretin) mimicked the PINK1-deficiency phenotype, decreasing astrocyte proliferation, EGFR expression and AKT activation, and increasing p38 activation. In addition, the proliferation defect in PINK1-KO astrocytes resulted in a delay in the wound healing process. Taken together, these results suggest that PINK1 deficiency causes astrocytes dysfunction, which may contribute to the development of PD due to delayed astrocytes-mediated repair of microenvironment in the brain.
PMCID: PMC3657120  PMID: 23440919
PINK1; astrocyte; proliferation; Parkinson's disease

Results 1-7 (7)