Abstract
BackgroundTau is an axonal protein that binds to and regulates microtubule function. Hyper-phosphorylation of Tau reduces its binding to microtubules and it is associated with β-amyloid deposition in Alzheimer’s disease. Paradoxically, Tau reduction may prevent β-amyloid pathology, raising the possibility that Tau mediates intracellular Aβ clearance. The current studies investigated the role of Tau in autophagic and proteasomal intracellular Aβ1-42 clearance and the subsequent effect on plaque deposition.ResultsTau deletion impaired Aβ clearance via autophagy, but not the proteasome, while introduction of wild type human Tau into Tau−/− mice partially restored autophagic clearance of Aβ1-42, suggesting that exogenous Tau expression can support autophagic Aβ1-42 clearance. Tau deletion impaired autophagic flux and resulted in Aβ1-42 accumulation in pre-lysosomal autophagic vacuoles, affecting Aβ1-42 deposition into the lysosome. This autophagic defect was associated with decreased intracellular Aβ1-42 and increased plaque load in Tau−/− mice, which displayed less cell death. Nilotinib, an Abl tyrosine kinase inhibitor that promotes autophagic clearance mechanisms, reduced Aβ1-42 only when exogenous human Tau was expressed in Tau−/− mice.ConclusionsThese studies demonstrate that Tau deletion affects intracellular Aβ1-42 clearance, leading to extracellular plaque.Electronic supplementary materialThe online version of this article (doi:10.1186/1750-1326-9-46) contains supplementary material, which is available to authorized users.
Highlights
Tau is an axonal protein that binds to and regulates microtubule function
We previously demonstrated that lentiviral Aβ1-42 expression leads to phosphorylated Tau (p-Tau) accumulation and inhibition of both the proteasome and autophagy [13,14,16,17], while the Abl tyrosine kinase inhibitor Nilotinib increases autophagic Aβ and p-Tau clearance, leading to decreased plaque levels in Alzheimer’s disease (AD) models [14,16]
Autophagy and the proteasome contribute to p-Tau and Aβ1-42 clearance We previously demonstrated that impaired autophagic clearance of intracellular Aβ leads to more plaque deposition in parkin deficient mice [13,14,16,17]
Summary
Tau is an axonal protein that binds to and regulates microtubule function. Hyper-phosphorylation of Tau reduces its binding to microtubules and it is associated with β-amyloid deposition in Alzheimer’s disease. Tau reduction may prevent β-amyloid pathology, raising the possibility that Tau mediates intracellular Aβ clearance. Two major pathologies that are linked to Alzheimer’s disease (AD), include extracellular β-amyloid (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) comprised of hyper-phosphorylated Tau (p-Tau) [1]. We previously demonstrated that lentiviral Aβ1-42 expression leads to p-Tau accumulation and inhibition of both the proteasome and autophagy [13,14,16,17], while the Abl tyrosine kinase inhibitor Nilotinib increases autophagic Aβ and p-Tau clearance, leading to decreased plaque levels in AD models [14,16]. Our data suggest that Tau deletion inhibits autophagic flux, resulting in reduction of intracellular Aβ degradation and increased plaque deposition
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