Overexpression of human a-synuclein in model systems, including cultured neurons, drosophila and mice, leads to biochemical and pathological changes that mimic synucleopathies including Parkinson's disease. We have overexpressed both wild-type (WT) and mutant alanine53 fi threonine (A53T) human a-synuclein by transgenic injection into Caenorhabditis elegans. Motor deficits were observed when either WT or A53T a-synuclein was overexpressed with a pan-neuronal or motor neuron promoter. Neuronal and dendritic loss were accelerated in all three sets of C. elegans dopaminergic neurons when human a-synuclein was overexpressed under the control of a dopaminergic neuron or panneuronal promoter, but not with a motor neuron promoter.There were no significant differences in neuronal loss between overexpressed WT and A53T forms or between worms of different ages (4 days, 10 days or 2 weeks). These results demonstrate neuronal and behavioral perturbations elicited by human a-synuclein in C. elegans that are dependent upon expression in specific neuron subtypes. This transgenic model in C. elegans, an invertebrate organism with excellent experimental resources for further genetic manipulation, may help facilitate dissection of pathophysiologic mechanisms of various synucleopathies. Keywords: a-synuclein, model organism, motor neuron, neurodegeneration, worm transgenic. Synucleopathies represent a large range of neuropathologically defined conditions that include Parkinson's disease (PD), dementia with Lewy bodies, Pick's disease and multiple system atrophy ( Spillantini et al. 1997Spillantini et al. , 1998Baba et al. 1998;Takeda et al. 1998). PD is a neurodegenerative disorder that affects 1% of the population over the age of 50 years. PD neurodegeneration is found predominantly in dopaminergic neurons of the substantia nigra where the pathological hallmark is the appearance of intracellular inclusions termed Lewy bodies. These bodies consist of protein complexes that include neurofilaments, ubiquitin and a-synuclein (Forno 1996 2 ; Spillantini et al. Abbreviations used: A53T, mutant alanine53 fi threonine; ADE, anterior deirid; CEP, cephalic neurons; GFP, green fluorescent protein; PD, Parkinson's disease; PDE, posterior deirid; UCHL1, ubiquitin carboxyl-terminal hydrolase L1; TBSB, Tris-buffered saline with 0.5% bovine serum albumin; WT, wild type.

Defects in mitochondrial OXPHOS are associated with diverse and mostly intractable human disorders. The single-subunit alternative oxidase (AOX) found in many eukaryotes, but not in arthropods or vertebrates, offers a potential bypass of the OXPHOS cytochrome chain under conditions of pathological OXPHOS inhibition. We have engineered Ciona intestinalis AOX for conditional expression in Drosophila melanogaster. Ubiquitous AOX expression produced no detrimental phenotype in wild-type flies. However, mitochondrial suspensions from AOX-expressing flies exhibited a significant cyanide-resistant substrate oxidation, and the flies were partially resistant to both cyanide and antimycin. AOX expression was able to complement the semilethality of partial knockdown of both cyclope (COXVIc) and the complex IV assembly factor Surf1. It also rescued the locomotor defect and excess mitochondrial ROS production of flies mutated in dj-1beta, a Drosophila homolog of the human Parkinson's disease gene DJ1. AOX appears to offer promise as a wide-spectrum therapeutic tool in OXPHOS disorders.

Mutations in mitochondrial oxidative phosphorylation complex I are associated with multiple pathologies, and complex I has been proposed as a crucial regulator of animal longevity. In yeast, the single-subunit NADH dehydrogenase Ndi1 serves as a non-proton-translocating alternative enzyme that replaces complex I, bringing about the reoxidation of intramitochondrial NADH. We have created transgenic strains of Drosophila that express yeast NDI1 ubiquitously. Mitochondrial extracts from NDI1-expressing flies displayed a rotenone-insensitive NADH dehydrogenase activity, and functionality of the enzyme in vivo was confirmed by the rescue of lethality resulting from RNAi knockdown of complex I. NDI1 expression increased median, mean, and maximum lifespan independently of dietary restriction, and with no change in sirtuin activity. NDI1 expression mitigated the aging associated decline in respiratory capacity and the accompanying increase in mitochondrial reactive oxygen species production, and resulted in decreased accumulation of markers of oxidative damage in aged flies. Our results support a central role of mitochondrial oxidative phosphorylation complex I in influencing longevity via oxidative stress, independently of pathways connected to nutrition and growth signaling.aging | mitochondria | respiratory chain | free radicals M itochondria are key metabolic organelles whose oxidative phosphorylation (OXPHOS) system is considered to be one of the most efficient producers of bioenergy. When OX-PHOS function is compromized (e.g., by mutations or toxins), bioenergy supply and cellular homeostasis are seriously disrupted, which can be lethal.OXPHOS complex I plays a central role in the regulation of ATP production, intermediary metabolism, and apoptosis (1, 2), and mutations affecting it cause many human pathologies (3). It has also been proposed as a pacemaker of the aging process (4). Treatments inferred to decrease the production of reactive oxygen species (ROS) at the level of complex I can prolong lifespan in Drosophila (5). All these characteristics make it essential to understand better the role of complex I in vivo and its involvement in aging.Many organisms possess alternative enzymes that can bypass or replace the proton-translocating complexes of the mitochondrial respiratory chain. These include the alternative oxidases (AOX) and the NADH dehydrogenases of the Ndi and Nde families. Together these enzymes provide an alternative respiratory chain that potentially allows the maintenance of redox homeostasis and intermediary metabolism under conditions where flux through the "standard" respiratory chain is limited by high ATP levels, the action of toxins or other physiological restraints (6, 7). AOX acts as a bypass of complexes III and IV, whereas Nde or Ndi can bypass complex I.In previous studies these bypass enzymes were shown to be active when introduced into the mitochondria of higher metazoans such as mammals (8-12), arthropods (13), or nematodes (14), all of which lack endogenous alternative enzymes. Fu...

RNA interference is a new approach to knockdown gene expression, but effectiveness varies depending on the organism, cell type or target sequence. Studies with Caenorhabditis elegans have shown that subsets of cells including neurons are often resistant to RNA interference. We measured RNA interference using green fluorescent protein reporter strains and feeding, soaking and injection delivery methods in a number of Caenorhabditis elegans neuron subtypes (dopaminergic, GABAergic, cholinergic, glutamatergic, touch). The sensitivity to RNA interference varied: GABAergic and dopaminergic neurons showed greater resistance while cholinergic, glutamatergic and touch neurons were more sensitive. Dysfunctional RRF-3, a putative RNA-directed RNA polymerase, had a significant effect on increasing neuron sensitivity in most subtypes. These results demonstrate that Caenorhabditis elegans neurons vary in their sensitivity to RNA interference.