ABSTRACT
Parkinsonian-pyramidal syndrome (PPS) is an early onset form of Parkinson's disease (PD) that shows degeneration of the extrapyramidal region of the brain to result in a severe form of PD. The toxic protein build-up has been implicated in the onset of PPS. Protein removal is mediated by an intracellular proteasome complex: an E3 ubiquitin ligase, the targeting component, is essential for function. FBXO7 encodes the F-box component of the SCF E3 ubiquitin ligase linked to familial forms of PPS. The Drosophila melanogaster homologue nutcracker (ntc) and a binding partner, PI31, have been shown to be active in proteasome function. We show that altered expression of either ntc or PI31 in dopaminergic neurons leads to a decrease in longevity and locomotor ability, phenotypes both associated with models of PD. Furthermore, expression of ntc-RNAi in an established α-synuclein-dependent model of PD rescues the phenotypes of diminished longevity and locomotor control.
Subject(s)
Carrier Proteins/metabolism , Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , F-Box Proteins/metabolism , Parkinson Disease/metabolism , Animals , Animals, Genetically Modified , Carrier Proteins/chemistry , Carrier Proteins/genetics , Disease Models, Animal , Drosophila Proteins/chemistry , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Eye/embryology , Eye/metabolism , F-Box Proteins/chemistry , F-Box Proteins/genetics , Female , Gene Expression , Longevity/genetics , Male , Organ Specificity/genetics , Organogenesis/genetics , Parkinson Disease/genetics , Protein Binding , Protein Interaction Domains and Motifs , alpha-Synuclein/genetics , alpha-Synuclein/metabolismABSTRACT
BACKGROUND: Parkinson disease (PD) is a progressive neurodegenerative disorder presenting with symptoms of resting tremor, bradykinesia, rigidity, postural instability and additional severe cognitive impairment over time. These symptoms arise from a decrease of available dopamine in the striatum of the brain resulting from the breakdown and death of dopaminergic (DA) neurons. A process implicated in the destruction of these neurons is mitochondrial breakdown and impairment. Upkeep and repair of mitochondria involves a number of complex and key components including Pink1, Parkin, and the PGC family of genes. PGC-1α has been characterized as a regulator of mitochondria biogenesis, insulin receptor signalling and energy metabolism, mutation of this gene has been linked to early onset forms of PD. The mammalian PGC family consists of three partially redundant genes making the study of full or partial loss of function difficult. The sole Drosophila melanogaster homologue of this gene family, spargel (srl), has been shown to function in similar pathways of mitochondrial upkeep and biogenesis. RESULTS: Directed expression of srl-RNAi in the D. melanogaster eye causes abnormal ommatidia and bristle formation while eye specific expression of srl-EY does not produce the minor rough eye phenotype associated with high temperature GMR-Gal4 expression. Ddc-Gal4 mediated tissue specific expression of srl transgene constructs in D. melanogaster DA neurons causes altered lifespan and climbing ability. Expression of a srl-RNAi causes an increase in mean lifespan but a decrease in overall loco-motor ability while induced expression of srl-EY causes a severe decrease in mean lifespan and a decrease in loco-motor ability. CONCLUSIONS: The reduced lifespan and climbing ability associated with a tissue specific expression of srl in DA neurons provides a new model of PD in D. melanogaster which may be used to identify novel therapeutic approaches to human disease treatment and prevention.
Subject(s)
Dopaminergic Neurons/metabolism , Drosophila Proteins/physiology , Locomotion/physiology , Parkinson Disease/genetics , Positive Transcriptional Elongation Factor B/physiology , Animals , Disease Models, Animal , Drosophila Proteins/genetics , Drosophila melanogaster , Locomotion/genetics , Positive Transcriptional Elongation Factor B/geneticsABSTRACT
The first step of the purine de novo synthesis pathway is catalyzed by amidophosphoribosyltransferase (E.C.2.4.2.14) which is encoded by two Prat genes in D. melanogaster, Prat and Prat2. Prat is a retrogene duplication of Prat2, where each gene has a distinct expression pattern. Prat transcription is restricted to proliferating tissues such as imaginal discs and the female germ line. Three conserved putative DNA replication-related element binding factor (DREF) sites lie upstream of the Prat coding region. These elements are upstream of many genes important in cell proliferation. We have found that DREF binds directly upstream of Prat and that the DRE sites associated with its activity are necessary for Prat expression; furthermore, we have determined that a second cis-acting element is present upstream of the Prat gene. Finally, the genes Distal-less, Mi-2 and dMyc, which influence Dref activity, do not appear to affect Prat transcription.
