DJ-1 knock-down impairs astrocyte mitochondrial function

Abstract

Mitochondrial dysfunction has long been implicated in the pathogenesis of Parkinson’s disease (PD). PD brain tissues show evidence for mitochondrial respiratory chain Complex I deficiency. Pharmacological inhibitors of Complex I, such as rotenone, cause experimental parkinsonism. The cytoprotective protein DJ-1, whose deletion is sufficient to cause genetic PD, is also known to have mitochondria-stabilizing properties. We have previously shown that DJ-1 is over-expressed in PD astrocytes, and that DJ-1 deficiency impairs the capacity of astrocytes to protect co-cultured neurons against rotenone. Since DJ-1 modulated, astrocyte-mediated neuroprotection against rotenone may depend upon proper astrocytic mitochondrial functioning, we hypothesized that DJ-1 deficiency would impair astrocyte mitochondrial motility, fission/fusion dynamics, membrane potential maintenance, and respiration, both at baseline and as an enhancement of rotenone-induced mitochondrial dysfunction. In astrocyte-enriched cultures, we observed that DJ-1 knock-down reduced mitochondrial motility primarily in the cellular processes of both untreated and rotenone treated cells. In these same cultures, DJ-1 knock-down did not appreciably affect mitochondrial fission, fusion, or respiration, but did enhance rotenone-induced reductions in the mitochondrial membrane potential. In neuron–astrocyte co-cultures, astrocytic DJ-1 knock-down reduced astrocyte process mitochondrial motility in untreated cells, but this effect was not maintained in the presence of rotenone. In the same co-cultures, astrocytic DJ-1 knock-down significantly reduced mitochondrial fusion in the astrocyte cell bodies, but not the processes, under the same conditions of rotenone treatment in which DJ-1 deficiency is known to impair astrocyte-mediated neuroprotection. Our studies therefore demonstrated the following new findings: (i) DJ-1 deficiency can impair astrocyte mitochondrial physiology at multiple levels, (ii) astrocyte mitochondrial dynamics vary with sub-cellular region, and (iii) the physical presence of neurons can affect astrocyte mitochondrial behavior.

Products of the Parkinson’s-disease related glyoxalase DJ-1, D-lactate and glycolate, support mitochondrial membrane potential and neuronal survival

“…In HeLa cells, DJ-1 RNAi specifically decreased expression of DJ-1 protein (Figure 2-figure supplement 1) and decreased mitochondrial membrane potential as probed with a J-aggregate forming lipophilic dye JC-1 ( Figure 2B) (Smiley et al, 1991), consistent with the previous reports (Larsen et al, 2011; peer-reviewed) is the author/funder. All rights reserved.…”

Adaptive regulation of glucose transport, glycolysis and respiration for cell proliferation

“…Surprisingly, a number of these genes are linked to mitochondrial activity, the centres for energy production through aerobic glucose catabolism (48); these genes include PTEN-induced putative kinase (PINK1/ PARK6), an E3 ubiquitin ligase Parkin/PARK2 (49-51), LRRK2/PARK8 kinase controlling mitochondrial dynamics (52) and DJ-1/PARK7. Deficiency in DJ-1/PARK7, which causes early-onset Parkinson's disease, was reported to lead to abnormal mitochondrial morphology and dynamics, increased sensitivity to oxidative stress and impaired mitochondrial function (53)(54)(55)(56)(57). Functions of DJ-1 are further described below, as this protein can be viewed as a unique coordinator of glucose metabolism, mitochondrial function and Parkinson's disease.…”

DJ-1 Protects Dopaminergic Neurons against Rotenone-Induced Apoptosis by Enhancing ERK-Dependent Mitophagy

“…2b). Several recent studies have reported that DJ-1 overexpression in astrocytes augments the capacity to protect neurons against rotenone and that DJ-1 knockdown impairs astrocyte-mediated neuroprotection against rotenone, 30,31 suggesting that DJ-1 may be involved in the neuroprotective effect of astrocytes on neurons. We quantified the number of THpositive neurons by immunofluorescence in the SN of control rats and rats overexpressing GFP-DJ-1.…”