Prion-like behaviour and tau-dependent cytotoxicity of pyroglutamylated amyloid-β

Abstract

Extracellular plaques of β-amyloid (Aβ) and intraneuronal neurofibrillary tangles made from tau are the histopathological signatures of Alzheimer's disease (AD). Plaques comprise Aβ fibrils that assemble from monomeric and oligomeric intermediates, and are prognostic indicators of AD. Despite the significance of plaques to AD, oligomers are considered to be the principal toxic forms of Aβ 1,2 . Interestingly, many adverse responses to Aβ, such as cytotoxicity 3 , microtubule loss 4 , impaired memory and learning 5 , and neuritic degeneration 6 , are greatly amplified by tau expression. N-terminally truncated, pyroglutamylated (pE) forms of Aβ 7,8 are strongly associated with AD, are more toxic than Aβ 1-42 and Aβ , and have been proposed as initiators of AD Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: http://www.nature.com/authors/editorial_policies/license.html#terms * Correspondence: gsb4g@virginia.edu. **Correspondence: Hans-Ulrich.Demuth@probiodrug.de. J.M.N and S.S. contributed equally to the paper.Full Methods and relevant references will be available in the online Supplementary Information accompanying this paper at http:// www.nature.com/nature.Author Contributions: J.M.N. performed most of the biochemical and cell biological experiments; S.S. was the principal force behind the experiments involving hAPP SL /hQC and TBA2.1/tau KO mice, and was aided by B.H.-P., H.C.; A.S. and T.W. fractionated and analyzed human brain extracts; E.S., K.Y. and B.W. performed the peri-hippocampal injection experiments; A.H. and C.G.G. produced and characterized the M64 and M87 antibodies; R.R. and K.R. performed the electrophysiology experiments; A.A., W.J. and S.G. performed and analyzed the immunohistochemical experiments on TBA2.1 and Tau-KO/TBA2.1 mice; G.S.B. and H.-U.D. initiated and directed the project; G.S.B. was the principal writer of the paper; all of the authors participated in the design and analysis of experiments, and in editing of the paper. Fig. 2) to the oligomers. HHS Public AccessAt 5 μM peptide, 5% pE-Aβ aggregated faster than Aβ 3(pE)-42 or Aβ 1-42 alone based on thioflavin T fluorescence shifts 15 ( Supplementary Fig. 3). The OD 450 /OD 490 ratio for Aβ 3(pE)-42 rose and peaked more rapidly than for Aβ 1-42 , but peaked at an ~25% lower level. The fastest rise in the OD 450 /OD 490 ratio was for 5% pE-Aβ, which peaked similarly to Aβ 3(pE)-42 . Aβ 3(pE)-42 , Aβ 1-42 and 5% pE-Aβ thus oligomerized by different pathways.To test whether distinct biological activities were coupled to these oligomerization differences, we compared cytotoxicity of the peptides towards cultured neurons or glia using calcein-AM and fluorescence microscopy 16 . Twelve hours of Aβ 1-42 exposure had little effect on cell viability for wild type (WT) or tau knockout (KO) neurons, or WT glial cells (Fig. 1a). Contrastingly, most WT neurons died and detached from the substrate after exposur...

Alzheimer disease

“…These data signify template mediated protein-misfolding by a process in which the original template, Aβ3(pE)-42, can transfer its distinct conformation and cytotoxic properties to Aβ1-42, which then can act as a template itself to induce further, prion-like propagation of toxic Aβ oligomers. 9 The in vivo relevance of these results was established by multiple lines of additional evidence. Most notably, putative dimers and trimers containing both conventional and pE-modified Aβ species were detected more commonly in brain cytosol collected post-mortem from AD patients than from normal age-matched controls, and transgenic mice that produced Aβ3(pE)-x experienced massive gliosis and neuron death in the hippocampus by disease.…”

“…Unlike wild type (WT) neurons, the tau KO neurons were not killed by the mixed oligomers. 9 These collective in vitro and in vivo results emphasize the exceptional potency of pE-modified Aβ and the tau requirement for its cytotoxicity.…”

“…Most notably, putative dimers and trimers containing both conventional and pE-modified Aβ species were detected more commonly in brain cytosol collected post-mortem from AD patients than from normal age-matched controls, and transgenic mice that produced Aβ3(pE)-x experienced massive gliosis and neuron death in the hippocampus by disease. 5,9,11,46,[48][49][50]79,80 At least some of these Aβ-tau connections are indirect, such as Aβ induced activation of protein kinases, which then catalyze abnormal tau phosphorylation. 11,45,47,51,52 There is also evidence, though, for a direct pathogenic connection between Aβ and tau.…”

“…Compared with fibrillar Aβ, soluble Aβ oligomers correlate better with neurotoxicity in vivo and are far more toxic than Aβ fibrils to cultured neurons. [5][6][7][8][9][10][11][12] Tau was discovered nearly 40 years ago as a microtubuleassociated protein (MAP) that stimulates tubulin polymerization, 13 but it was not until a decade later that its presence in NFTs was first described. [14][15][16] Surprisingly, beyond its generic MAP function as a stimulator of microtubule (MT) assembly, the only known specific function of tau is that it impedes the movement of kinesin MT motor proteins and their attached cargoes along MTs.…”

Alzheimer’s Disease Pathogenesis: The Denied Access Model

“…Countless articles are published which present new mechanistic hypotheses of AßO toxicity. To briefly summarize, AßOs have been linked to AD in the following ways: Oxidative stress and lipid peroxidation in neurons [33][34][35][36] toxic ion pore formation on the cell membrane [37,38], synaptic plasticity disruption [39][40][41][42], astrocyte and microglia calcium influx [36], selective neuronal degeneration [43], prion-like infectious behavior [34,44,45], binding to numerous membrane proteins [46][47][48][49], insulin resistance [50][51][52] calcium homeostasis disruption [35,53] and tau hyperphosphorylation induction [54]. One of the main issues is that AßOs lack a common description of structural toxicity and are thought of as "an emperor in need of clothes" since they possess numerous conformations ranging from monomers, to trimers, and to eventual fibrils [8].…”