Abeta exacerbates the neuronal dysfunction caused by human tau expression in a Drosophila model of Alzheimer's disease.
Alzheimer's disease (AD) is characterised by neurofibrillary tangles composed of hyper-phosphorylated tau, and neuritic plaques composed of misfolded amyloid peptide (Abeta(42)). It is generally believed that the hyper-phosphorylated tau and oligomeric Abeta(42) are responsible for the neuronal dysfunction and cognitive impairments that underlie the early stages of AD, but the mechanism by which they interact in the pathogenic process is not clear. Mounting evidence suggests that Abeta(42) pathology lies upstream of hyper-phosphorylated tau pathology. Similarly much is being learnt about how each protein affects neuronal function. However, the impact that either pathological protein has on neuronal dysfunction caused by the other is not extensively studied. We have investigated this in a Drosophila model of AD in which we express both phosphorylated human tau (tau(wt)) and oligomeric Abeta(42). We find that expression of tau(wt) causes neuronal dysfunction by disrupting axonal transport and synaptic structure, and that this leads to behavioural impairments and reduced lifespan. Co-expression of Abeta(42) with tau(wt) increases tau phosphorylation and exacerbates all these tau-mediated phenotypes. Treatment of tau(wt)/Abeta(42) and flies with LiCl ameliorates the exacerbating effect of Abeta(42), suggesting that GSK-3beta may be involved in the mechanism by which Abeta(42) and tau(wt) interact to cause neuronal dysfunction. Conversely to the effect of Abeta(42), mimicking the wingless signalling pathway by co-expression of dishevelled with tau(wt) reduces tau phosphorylation and suppresses the tau-mediated phenotypes. It is therefore possible to speculate that the mechanism by which Abeta(42) interacts with tau in the pathogenesis of AD is by down-regulating endogenous wnt signalling.
Department of Neurosciences, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK.
James
J
Folwell
Catherine M
CM
Cowan
Kiren K
KK
Ubhi
Hassan
H
Shiabh
Tracey A
TA
Newman
David
D
Shepherd
Amritpal
A
Mudher
D000544:Alzheimer Disease / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D016229:Amyloid beta-Peptides / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D001370:Axonal Transport / Q000502:physiology*; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology; D004330:Drosophila / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008124:Locomotion / Q000502:physiology; D008136:Longevity / Q000502:physiology; D009469:Neuromuscular Junction / Q000473:pathology / Q000502:physiology; D009474:Neurons / Q000473:pathology / Q000502:physiology; D010446:Peptide Fragments / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013569:Synapses / Q000473:pathology / Q000502:physiology; D051155:Wnt1 Protein / Q000378:metabolism; D016875:tau Proteins / Q000235:genetics* / Q000378:metabolism
D016229:Amyloid beta-Peptides; D029721:Drosophila Proteins; C054369:MAPT protein, human; D010446:Peptide Fragments; D051155:Wnt1 Protein; C075222:amyloid beta-protein (1-42); D016875:tau Proteins; C074622:wg protein, Drosophila; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3