Alpha-Synuclein Oligomers Interact with Metal Ions to Induce Oxidative Stress and Neuronal Death in Parkinson's Disease.

Aims: Protein aggregation and oxidative stress are both key pathogenic processes in Parkinson's disease, although the mechanism by which misfolded proteins induce oxidative stress and neuronal death remains unknown. In this study, we describe how aggregation of alpha-synuclein (α-S) from its monomeric form to its soluble oligomeric state results in aberrant free radical production and neuronal toxicity.

Results: We first demonstrate excessive free radical production in a human induced pluripotent stem-derived α-S triplication model at basal levels and on application of picomolar doses of β-sheet-rich α-S oligomers.

Structural characterization of toxic oligomers that are kinetically trapped during α-synuclein fibril formation.

We describe the isolation and detailed structural characterization of stable toxic oligomers of α-synuclein that have accumulated during the process of amyloid formation. Our approach has allowed us to identify distinct subgroups of oligomers and to probe their molecular architectures by using cryo-electron microscopy (cryoEM) image reconstruction techniques. Although the oligomers exist in a range of sizes, with different extents and nature of β-sheet content and exposed hydrophobicity, they all possess a hollow cylindrical architecture with similarities to certain types of amyloid fibril, suggesting that the accumulation of at least some forms of amyloid oligomers is likely to be a consequence of very slow rates of rearrangement of their β-sheet structures.

PINK1 deficiency in β-cells increases basal insulin secretion and improves glucose tolerance in mice.

The Parkinson's disease (PD) gene, PARK6, encodes the PTEN-induced putative kinase 1 (PINK1) mitochondrial kinase, which provides protection against oxidative stress-induced apoptosis. Given the link between glucose metabolism, mitochondrial function and insulin secretion in β-cells, and the reported association of PD with type 2 diabetes, we investigated the response of PINK1-deficient β-cells to glucose stimuli to determine whether loss of PINK1 affected their function. We find that loss of PINK1 significantly impairs the ability of mouse pancreatic β-cells (MIN6 cells) and primary intact islets to take up glucose.

Enhancing nucleotide metabolism protects against mitochondrial dysfunction and neurodegeneration in a PINK1 model of Parkinson's disease.

Mutations in PINK1 cause early-onset Parkinson's disease (PD). Studies in Drosophila melanogaster have highlighted mitochondrial dysfunction on loss of Pink1 as a central mechanism of PD pathogenesis. Here we show that global analysis of transcriptional changes in Drosophila pink1 mutants reveals an upregulation of genes involved in nucleotide metabolism, critical for neuronal mitochondrial DNA synthesis.

Loss of PINK1 increases the heart's vulnerability to ischemia-reperfusion injury.

Objectives: Mutations in PTEN inducible kinase-1 (PINK1) induce mitochondrial dysfunction in dopaminergic neurons resulting in an inherited form of Parkinson's disease. Although PINK1 is present in the heart its exact role there is unclear. We hypothesized that PINK1 protects the heart against acute ischemia reperfusion injury (IRI) by preventing mitochondrial dysfunction.

The glucocerobrosidase E326K variant predisposes to Parkinson's disease, but does not cause Gaucher's disease.

Background: Heterozygous loss-of-function mutations in the acid beta-glucocerebrosidase (GBA1) gene, responsible for the recessive lysosomal storage disorder, Gaucher's disease (GD), are the strongest known risk factor for Parkinson's disease (PD). Our aim was to assess the contribution of GBA1 mutations in a series of early-onset PD.

Methods: One hundred and eighty-five PD patients (with an onset age of ≤50) and 283 age-matched controls were screened for GBA1 mutations by Sanger sequencing.

The role of the mitochondrial NCX in the mechanism of neurodegeneration in Parkinson's disease.

Mitochondrial Na(+)/Ca(2+) exchange (NCXmito) is critical for neuronal Ca(2+) homeostasis and prevention of cell death from excessive mitochondrial Ca(2+) (m[Ca(2+)]) accumulation. The mitochondrial kinase PINK1 appears to regulate the mCa(2+) efflux from dopaminergic (DAergic) neurons, possibly by directly regulating NCXmito. However, the precise molecular identity of NCXmito is unknown and has been the subject of great controversy.

Direct observation of the interconversion of normal and toxic forms of α-synuclein.

Here, we use single-molecule techniques to study the aggregation of α-synuclein, the protein whose misfolding and deposition is associated with Parkinson's disease. We identify a conformational change from the initially formed oligomers to stable, more compact proteinase-K-resistant oligomers as the key step that leads ultimately to fibril formation. The oligomers formed as a result of the structural conversion generate much higher levels of oxidative stress in rat primary neurons than do the oligomers formed initially, showing that they are more damaging to cells.

PINK1 cleavage at position A103 by the mitochondrial protease PARL.

Mutations in PTEN-induced kinase 1 (PINK1) cause early onset autosomal recessive Parkinson's disease (PD). PINK1 is a 63 kDa protein kinase, which exerts a neuroprotective function and is known to localize to mitochondria. Upon entry into the organelle, PINK1 is cleaved to produce a ∼53 kDa protein (ΔN-PINK1).

Mitophagy and Parkinson's disease: the PINK1-parkin link.

The study of rare, inherited mutations underlying familial forms of Parkinson's disease has provided insight into the molecular mechanisms of disease pathogenesis. Mutations in these genes have been functionally linked to several key molecular pathways implicated in other neurodegenerative disorders, including mitochondrial dysfunction, protein accumulation and the autophagic-lysosomal pathway. In particular, the mitochondrial kinase PINK1 and the cytosolic E3 ubiquitin ligase parkin act in a common pathway to regulate mitochondrial function.

Targeting mitochondrial dysfunction in neurodegenerative disease: Part II.

Importance Of The Field: With improvements in life expectancy over the past decades, the incidence of neurodegenerative disease has dramatically increased and new therapeutic strategies are urgently needed. One possible approach is to target mitochondrial dysfunction, which has been implicated in the pathogenesis of numerous neurodegenerative disorders.

Areas Covered In This Review: This review examines the role of mitochondrial dysfunction in neurodegeneration, drawing examples from common diseases such as Alzheimer's disease and rarer familial disorders such as Charcot-Marie-Tooth.

Targeting mitochondrial dysfunction in neurodegenerative disease: Part I.

Importance Of The Field: The socioeconomic burden of an aging population has accelerated the urgency of novel therapeutic strategies for neurodegenerative disease. One possible approach is to target mitochondrial dysfunction, which has been implicated in the pathogenesis of numerous neurodegenerative disorders.

Areas Covered In This Review: This review examines the role of mitochondrial defects in aging and neurodegenerative disease, ranging from common diseases such as Alzheimer's and Parkinson's disease to rare familial disorders such as the spinocerebellar ataxias.

PINK1 function in health and disease.

The role of mitochondria in sporadic Parkinson's disease (PD) has been debated for a little over 20 years since the description of complex I deficiency in the substantia nigra pars compacta (SNpc) of PD patients. However, the identification of recessive pathogenic mutations in the pink1 gene in familial PD cases firmly re-ignited interest in the pathophysiology of mitochondria in PD. PINK1 is a putative mitochondrial serine/threonine kinase, which protects cells against oxidative stress induced apoptosis.

Glucocerebrosidase mutations in clinical and pathologically proven Parkinson's disease.

Mutations in the glucocerebrosidase gene (GBA) are associated with Gaucher's disease, the most common lysosomal storage disorder. Parkinsonism is an established feature of Gaucher's disease and an increased frequency of mutations in GBA has been reported in several different ethnic series with sporadic Parkinson's disease. In this study, we evaluated the frequency of GBA mutations in British patients affected by Parkinson's disease.

PINK1-associated Parkinson's disease is caused by neuronal vulnerability to calcium-induced cell death.

Mutations in PINK1 cause autosomal recessive Parkinson's disease. PINK1 is a mitochondrial kinase of unknown function. We investigated calcium homeostasis and mitochondrial function in PINK1-deficient mammalian neurons.

What have PINK1 and HtrA2 genes told us about the role of mitochondria in Parkinson's disease?

Parkinson's disease (PD) is a common, disabling, neurodegenerative disease. Our knowledge of the molecular events leading to PD is being greatly enhanced by the study of relatively rare familial form of the disease. Nevertheless, the pathways leading from the genetic mutations to nigral cell degeneration and the other features in PD remain poorly understood.

A balanced chromosomal translocation disrupting ARHGEF9 is associated with epilepsy, anxiety, aggression, and mental retardation.

Clustering of inhibitory gamma-aminobutyric acid(A) (GABA(A)) and glycine receptors at synapses is thought to involve key interactions between the receptors, a "scaffolding" protein known as gephyrin and the RhoGEF collybistin. We report the identification of a balanced chromosomal translocation in a female patient presenting with a disturbed sleep-wake cycle, late-onset epileptic seizures, increased anxiety, aggressive behavior, and mental retardation, but not hyperekplexia. Fine mapping of the breakpoint indicates disruption of the collybistin gene (ARHGEF9) on chromosome Xq11, while the other breakpoint lies in a region of 18q11 that lacks any known or predicted genes.

PINK1 is necessary for long term survival and mitochondrial function in human dopaminergic neurons.

Parkinson's disease (PD) is a common age-related neurodegenerative disease and it is critical to develop models which recapitulate the pathogenic process including the effect of the ageing process. Although the pathogenesis of sporadic PD is unknown, the identification of the mendelian genetic factor PINK1 has provided new mechanistic insights. In order to investigate the role of PINK1 in Parkinson's disease, we studied PINK1 loss of function in human and primary mouse neurons.

The mitochondrial protease HtrA2 is regulated by Parkinson's disease-associated kinase PINK1.

In mice, targeted deletion of the serine protease HtrA2 (also known as Omi) causes mitochondrial dysfunction leading to a neurodegenerative disorder with parkinsonian features. In humans, point mutations in HtrA2 are a susceptibility factor for Parkinson's disease (PARK13 locus). Mutations in PINK1, a putative mitochondrial protein kinase, are associated with the PARK6 autosomal recessive locus for susceptibility to early-onset Parkinson's disease.

A heterozygous effect for PINK1 mutations in Parkinson's disease?

Objective: To investigate the significance of PINK1 mutations in sporadic Parkinson's disease (PD).

Methods: We determined the frequency of PINK1 mutations by direct sequencing in a large series of PD patients with apparently sporadic disease (n = 768).

Results: Twelve heterozygous mutations were identified, nine in PD patients and three in control subjects.

Altered cleavage and localization of PINK1 to aggresomes in the presence of proteasomal stress.

Following our identification of PTEN-induced putative kinase 1 (PINK1) gene mutations in PARK6-linked Parkinson's disease (PD), we have recently reported that PINK1 protein localizes to Lewy bodies (LBs) in PD brains. We have used a cellular model system of LBs, namely induction of aggresomes, to determine how a mitochondrial protein, such as PINK1, can localize to aggregates. Using specific polyclonal antibodies, we firstly demonstrated that human PINK1 was cleaved and localized to mitochondria.

Degradation of DIAP1 by the N-end rule pathway is essential for regulating apoptosis.

Some members of the inhibitor of apoptosis (IAP) protein family block apoptosis by binding to and neutralizing active caspases. We recently demonstrated that a physical association between IAP and caspases alone is insufficient to regulate caspases in vivo and that an additional level of control is provided by IAP-mediated ubiquitination of both itself and the associated caspases. Here we show that Drosophila IAP 1 (DIAP1) is degraded by the 'N-end rule' pathway and that this process is indispensable for regulating apoptosis.