Mutations in Pink1, a gene encoding a Ser͞Thr kinase with a mitochondrial-targeting signal, are associated with Parkinson's disease (PD), the most common movement disorder characterized by selective loss of dopaminergic neurons. The mechanism by which loss of Pink1 leads to neurodegeneration is not understood. Here we show that inhibition of Drosophila Pink1 (dPink1) function results in energy depletion, shortened lifespan, and degeneration of select indirect flight muscles and dopaminergic neurons. The muscle pathology was preceded by mitochondrial enlargement and disintegration. These phenotypes could be rescued by the wild type but not the pathogenic C-terminal deleted form of human Pink1 (hPink1). The muscle and dopaminergic phenotypes associated with dPink1 inactivation show similarity to that seen in parkin mutant flies and could be suppressed by the overexpression of Parkin but not DJ-1. Consistent with the genetic rescue results, we find that, in dPink1 RNA interference (RNAi) animals, the level of Parkin protein is significantly reduced. Together, these results implicate Pink1 and Parkin in a common pathway that regulates mitochondrial physiology and cell survival in Drosophila.mitochondria ͉ Parkinson's disease ͉ Pten-induced kinase 1 ͉ indirect flight muscle P arkinson's disease (PD) is the most common movement disorder characterized pathologically by the deficiency of brain dopamine content and the selective degeneration of dopaminergic neurons in the substantia nigra. The most common forms of PD are sporadic with no known cause. Nevertheless, postmortem studies have identified common features associated with sporadic PD, such as mitochondrial complex I dysfunction, oxidative stress, and aggregation of abnormal proteins (1, 2).Although initial studies on the etiology of PD have focused on environmental factors, recent genetic studies have firmly established the contribution of inheritable factors in PD pathogenesis (2, 3). At least ten distinct loci have been associated with rare familial forms of PD (FPD). It is anticipated that understanding the molecular lesions associated with these FPD genes will shed light on the pathogenesis of the more common forms of the disease. Dominant mutations in ␣-Synuclein (␣-Syn) and LRRK2͞dardarin and recessive mutations in parkin, DJ-1, and Pink1 have been associated with FPD (4-10). Of these five genes, ␣-Syn, parkin, and DJ-1 have been most intensively studied. Studies using in vivo animal models and in vitro cell culture have linked mutations of these genes to impairments of mitochondrial structure and function and oxidative stress response, reinforcing the general involvement of mitochondrial dysfunction and oxidative stress in PD pathogenesis (11-21). Consistent with this notion, these proteins have been shown to be present in mitochondria or interact with mitochondrial proteins (8,(22)(23)(24), suggesting that they may directly regulate mitochondria function.A further link between mitochondria and PD was supported by the fact that Pink1 encodes a predicted Se...

Mitochondria form dynamic tubular networks that undergo frequent morphological changes through fission and fusion, the imbalance of which can affect cell survival in general and impact synaptic transmission and plasticity in neurons in particular. Some core components of the mitochondrial fission/fusion machinery, including the dynamin-like GTPases Drp1, Mitofusin, Opa1, and the Drp1-interacting protein Fis1, have been identified. How the fission and fusion processes are regulated under normal conditions and the extent to which defects in mitochondrial fission/fusion are involved in various disease conditions are poorly understood. Mitochondrial malfunction tends to cause diseases with brain and skeletal muscle manifestations and has been implicated in neurodegenerative diseases such as Parkinson's disease (PD). Whether abnormal mitochondrial fission or fusion plays a role in PD pathogenesis has not been shown. Here, we show that Pink1, a mitochondria-targeted Ser/Thr kinase linked to familial PD, genetically interacts with the mitochondrial fission/fusion machinery and modulates mitochondrial dynamics. Genetic manipulations that promote mitochondrial fission suppress Drosophila Pink1 mutant phenotypes in indirect flight muscle and dopamine neurons, whereas decreased fission has opposite effects. In Drosophila and mammalian cells, overexpression of Pink1 promotes mitochondrial fission, whereas inhibition of Pink1 leads to excessive fusion. Our genetic interaction results suggest that Fis1 may act in-between Pink1 and Drp1 in controlling mitochondrial fission. These results reveal a cell biological role for Pink1 and establish mitochondrial fission/fusion as a paradigm for PD research. Compounds that modulate mitochondrial fission/fusion could have therapeutic value in PD intervention.

Multisite hyperphosphorylation of tau has been implicated in the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD). However, the phosphorylation events critical for tau toxicity and mechanisms regulating these events are largely unknown. Here we show that Drosophila PAR-1 kinase initiates tau toxicity by triggering a temporally ordered phosphorylation process. PAR-1 directly phosphorylates tau at S262 and S356. This phosphorylation event is a prerequisite for the action of downstream kinases, including glycogen synthase kinase 3 (GSK-3) and cyclin-dependent kinase-5 (Cdk5), to phosphorylate several other sites and generate disease-associated phospho-epitopes. The initiator role of PAR-1 is further underscored by the fact that mutating PAR-1 phosphorylation sites causes a much greater reduction of overall tau phosphorylation and toxicity than mutating S202, one of the downstream sites whose phosphorylation depends on prior PAR-1 action. These findings begin to differentiate the effects of various phosphorylation events on tau toxicity and provide potential therapeutic targets.