Aβ Oligomers Cause Localized Ca 2+ Elevation, Missorting of Endogenous Tau into Dendrites, Tau Phosphorylation, and Destruction of Microtubules and Spines

“Despite numerous studies on the pathway of APP misprocessing and its consequences for neurons the modes of A toxicity have remained enigmatic (Haass and Selkoe, 2007; Small and Duff, 2008).”

“Nevertheless, there were differences in structure because dot blots with antibody A11, which recognizes a more toxic generic amyloid conformation (Kayed et al., 2003), were more intense for F12 medium than for Nb (Fig.”

“There is a moderate decrease of ATP which is more apparent with F12 than with Nb medium, suggesting that F12, which was used in the original procedure (Lambert et al., 1998), could have some toxic effects on its own.”

“These include loss of synapses and neurons, deficiency in neurotransmitters and metabolism, aggregation of amyloid- (A )-peptides into extracellular “amyloid plaques” and Tau protein into intracellular “neurofibrillary tangles” (Selkoe, 2004; Binder et al., 2005; Ballatore et al., 2007).”

“…conversely Tau is considered necessary for the progression of neurodegeneration, as seen in cell and animal models (Rapoport et al., 2002; King et al., 2006; Roberson et al., 2007), and indeed the Tau pathology correlates well with clinical symptoms (Braak and Braak, 1991; Clavaguera et al., 2009).”

“4e,f), and involving NMDA receptors and others (De Felice et al., 2007; Shankar et al., 2007).”

“We also tested extracellular ATP (100 M, 3 h), which functions as a stress signal and induces Ca 2 influx via P2 receptors and has been implicated in neurodegenerative disease (Burnstock, 2007).”

“As shown previously (Stamer et al., 2002; Hollenbeck and Saxton, 2005; Thies and Mandelkow, 2007), such mitochondrial traffic jams cause a local drop of energy (ATP) and consequently spine destruction through the perturbation of the actin network and loss of synaptic components (Whiteman et al.,…”

“In addition a change in MT dynamics alters their posttranslational modifications and thus perturbs polarized trafficking of cargo (Li and Gundersen, 2008; Conde and Cáceres, 2009; Konishi and Setou, 2009).”

“Previous studies have focused primarily on global effects of A on changes in Tau (e.g., phosphorylation, cleavage) and resulting cell death (Yankner et al., 1989; Mattson, 1990; Busciglio et al., 1995; Park and Ferreira, 2005; King et al., 2006), with less attention to the localized changes due to…”

“As shown previously (Stamer et al., 2002; Hollenbeck and Saxton, 2005; Thies and Mandelkow, 2007), such mitochondrial traffic jams cause a local drop of energy (ATP) and consequently spine destruction through the perturbation of the actin network and loss of synaptic components (Whiteman et al.,…”

“4e,f), and involving NMDA receptors and others (De Felice et al., 2007; Shankar et al., 2007).”

“Thirdly, Ca 2 uncouples mitochondrial motors from microtubule tracks (Wang and Schwarz, 2009).”

“We also note that in our preparations we did not consistently observe a band at 56 kDa, a species that has been reported to be toxic for transgenic mice (Lesné et al., 2006) but can be visualized in certain conditions (Walsh et al., 2005; Ashe, 2006; Bernstein et al., 2009).”

“…upstream of changes in Tau, but conversely Tau is considered necessary for the progression of neurodegeneration, as seen in cell and animal models (Rapoport et al., 2002; King et al., 2006; Roberson et al., 2007), and indeed the Tau pathology correlates well with clinical symptoms (Braak and…”

“On the SDS gels, the different media (F12 or Nb) yielded similar bands, with the caveat that these gels can obscure the coexistence of multiple oligomeric species (Glabe, 2008).”

“We note that, apart from its minor amount, the fiber component would be of lesser importance since its toxicity is lower than that of oligomers (Klein et al., 2004; Ono et al., 2009).”

“, proteasome, mitochondria) and perturbation of calcium homeostasis (Mattson, 2007).”

“Examples of local effects are the early loss of synapses and the appearance of Tau in somata and dendrites (Götz and Ittner, 2008).”

“The neurofibrillary changes follow a typical pathway of spreading which corresponds to clinical symptoms, hence Tau pathology is considered as one of the culprits in the disease (Braak and Braak, 1991; Spires-Jones et al., 2009).”

“…focused primarily on global effects of A on changes in Tau (e.g., phosphorylation, cleavage) and resulting cell death (Yankner et al., 1989; Mattson, 1990; Busciglio et al., 1995; Park and Ferreira, 2005; King et al., 2006), with less attention to the localized changes due to Tau redistribution.”

“Despite numerous studies on the pathway of APP misprocessing and its consequences for neurons the modes of A toxicity have remained enigmatic (Haass and Selkoe, 2007; Small and Duff, 2008).”

“We note that, apart from its minor amount, the fiber component would be of lesser importance since its toxicity is lower than that of oligomers (Klein et al., 2004; Ono et al., 2009).”

“An additional function of microtubules is to subtend cellular networks such as the ER and intermediate filament network, so that these networks collapse when microtubules or motors are inactivated or reversed in direction (Stamer et al., 2002; Eriksson et al., 2009).”

“These include loss of synapses and neurons, deficiency in neurotransmitters and metabolism, aggregation of amyloid- (A )-peptides into extracellular “amyloid plaques” and Tau protein into intracellular “neurofibrillary tangles” (Selkoe, 2004; Binder et al., 2005; Ballatore et al., 2007).”

“In addition a change in MT dynamics alters their posttranslational modifications and thus perturbs polarized trafficking of cargo (Li and Gundersen, 2008; Conde and Cáceres, 2009; Konishi and Setou, 2009).”

“Lowering cytosolic Ca 2 would appear as prime target for intervention, but the decay of microtubules seems more targetable through microtubulestabilizing drugs (Mattson, 1992; Michaelis et al., 2005; Zhang et al., 2005).”

“In addition a change in MT dynamics alters their posttranslational modifications and thus perturbs polarized trafficking of cargo (Li and Gundersen, 2008; Conde and Cáceres, 2009; Konishi and Setou, 2009).”

“This could explain the increase in activity of MARK, cdk5 and others; for example, CaMK-I activates MARK2 and this pathway contributes to neuronal differentiation (Biernat et al., 2002; Uboha et al., 2007; He et al., 2008; Wu et al., 2010).”

“6c); this kinase, like MARK, is involved in axonal differentiation (Kishi et al., 2005) and also belongs to the AMPK family of kinases.”

“The neurofibrillary changes follow a typical pathway of spreading which corresponds to clinical symptoms, hence Tau pathology is considered as one of the culprits in the disease (Braak and Braak, 1991; Spires-Jones et al., 2009).”

“Earlier experiments with overexpressed Tau had shown that dendritic Tau can cause traffic jams, resulting in transport inhibition of vesicles and organelles (e.g., mito- chondria), loss of ATP supply, and decay of synaptic spines (Thies and Mandelkow, 2007).”

“…have focused primarily on global effects of A on changes in Tau (e.g., phosphorylation, cleavage) and resulting cell death (Yankner et al., 1989; Mattson, 1990; Busciglio et al., 1995; Park and Ferreira, 2005; King et al., 2006), with less attention to the localized changes due to Tau…”

“This could explain the increase in activity of MARK, cdk5 and others; for example, CaMK-I activates MARK2 and this pathway contributes to neuronal differentiation (Biernat et al., 2002; Uboha et al., 2007; He et al., 2008; Wu et al., 2010).”

“…focused primarily on global effects of A on changes in Tau (e.g., phosphorylation, cleavage) and resulting cell death (Yankner et al., 1989; Mattson, 1990; Busciglio et al., 1995; Park and Ferreira, 2005; King et al., 2006), with less attention to the localized changes due to Tau redistribution.”

“and promotes their disassembly (Schliwa et al., 1981); this mechanism operates in addition to the Ca 2 -CaM-dependent”

“These include loss of synapses and neurons, deficiency in neurotransmitters and metabolism, aggregation of amyloid- (A )-peptides into extracellular “amyloid plaques” and Tau protein into intracellular “neurofibrillary tangles” (Selkoe, 2004; Binder et al., 2005; Ballatore et al., 2007).”

“This can be done in a variety of ways, and there is a debate on which is most appropriate for assessing A toxicity (Wogulis et al., 2005).”

“We also note that in our preparations we did not consistently observe a band at 56 kDa, a species that has been reported to be toxic for transgenic mice (Lesné et al., 2006) but can be visualized in certain conditions (Walsh et al., 2005; Ashe, 2006; Bernstein et al., 2009).”

“…Tau, but conversely Tau is considered necessary for the progression of neurodegeneration, as seen in cell and animal models (Rapoport et al., 2002; King et al., 2006; Roberson et al., 2007), and indeed the Tau pathology correlates well with clinical symptoms (Braak and Braak, 1991; Clavaguera et…”

“The results have not been uniform; increases in Tau phosphorylation have been observed in some cases, not in others (Davis et al., 1997; Lovell et al., 2004; Su et al., 2010).”

“The results have not been uniform; increases in Tau phosphorylation have been observed in some cases, not in others (Davis et al., 1997; Lovell et al., 2004; Su et al., 2010).”

“This type of phosphorylation causes the detachment of Tau from microtubules, makes them dynamic, and renders Tau highly diffusible and able to enter dendrites (Konzack et al., 2007).”

“Part of the problem is the definition of the toxic state of A , which may be monomeric, oligomeric (currently favored), or fibrillar (formerly favored) (Klein, 2006; Glabe, 2008; Roychaudhuri et al., 2009).”

“…polyclonal amyloid- (Cell Signaling Technology; 1:200); mAb 12E8 (1:500); mAb AT8 (1:100); polyclonal MARK phospho-T208 [prepared as described by Timm et al. (2008); 1:100]; phosphop70S6Kinase (pT389, clone 108D2, Cell Signaling Technology; 1:50); polyclonal BRSK1 (Acris, 1:100); phospho-MAPK…”

“…previously (Stamer et al., 2002; Hollenbeck and Saxton, 2005; Thies and Mandelkow, 2007), such mitochondrial traffic jams cause a local drop of energy (ATP) and consequently spine destruction through the perturbation of the actin network and loss of synaptic components (Whiteman et al., 2009).”

“Lowering cytosolic Ca 2 would appear as prime target for intervention, but the decay of microtubules seems more targetable through microtubulestabilizing drugs (Mattson, 1992; Michaelis et al., 2005; Zhang et al., 2005).”

“1b), whereas the general A antibody 6E10 (Pirttilä et al., 1994; Jung et al., 1999) reacted independently of the medium.”

“With regard to proline-directed kinases we tested MAPK, JNK, cdk5, and GSK3b, all considered to be involved in the pathological phosphorylation of Tau (Johnson, 2006).”

“This could explain the increase in activity of MARK, cdk5 and others; for example, CaMK-I activates MARK2 and this pathway contributes to neuronal differentiation (Biernat et al., 2002; Uboha et al., 2007; He et al., 2008; Wu et al., 2010).”

“Lowering cytosolic Ca 2 would appear as prime target for intervention, but the decay of microtubules seems more targetable through microtubulestabilizing drugs (Mattson, 1992; Michaelis et al., 2005; Zhang et al., 2005).”

“To confirm equal loading and successful blotting membranes were routinely stained using the CPTS staining method (Bickar and Reid, 1992), followed by standard Western blot procedure.”

“Glabe, University of California, Irvine, CA), that shows high specificity to amyloid oligomers (Kayed et al., 2007).”

“Proteasome activity was determined following (Flood et al., 2005).”

“Given this localized loss of microtubules, we hypothesized that this might lead to an impairment of mitochondrial trafficking with local dendritic energy deprivation (Yan et al., 2010).”

“This could explain the increase in activity of MARK, cdk5 and others; for example, CaMK-I activates MARK2 and this pathway contributes to neuronal differentiation (Biernat et al., 2002; Uboha et al., 2007; He et al., 2008; Wu et al., 2010).”

“1b), whereas the general A antibody 6E10 (Pirttilä et al., 1994; Jung et al., 1999) reacted independently of the medium.”

“Lowering cytosolic Ca 2 would appear as prime target for intervention, but the decay of microtubules seems more targetable through microtubulestabilizing drugs (Mattson, 1992; Michaelis et al., 2005; Zhang et al., 2005).”

“We also note that in our preparations we did not consistently observe a band at 56 kDa, a species that has been reported to be toxic for transgenic mice (Lesné et al., 2006) but can be visualized in certain conditions (Walsh et al., 2005; Ashe, 2006; Bernstein et al., 2009).”

“, 2007), and indeed the Tau pathology correlates well with clinical symptoms (Braak and Braak, 1991; Clavaguera et al., 2009).”

“Many studies employing supraphysiological concentrations of synthetic Ab peptides in oligomeric form (generally larger than dimers/ trimers) have also provided evidence of tau alteration (Zempel et al. 2010) and various neurotoxic effects.”

“A recent report (Zempel et al., 2010) suggests that spines might serve as a site of convergence for amyloid beta and tau.”

“Acute exposure of neuronal cultures to Ab led to hyperphosphorylation (De Felice et al., 2008) and mislocalization of tau into dendritic spines (Zempel et al., 2010), which, at least in some dendrites, was associated with spine collapse and dendritic degeneration.”

“Some experiments indicated that tau is normally highly enriched in axons relative to dendrites (Binder et al., 1985), but in response to Aβ is extensively redistributed into the somato-dendritic compartment (Delacourte et al., 1990; Zempel et al., 2010).”

“In cultured neurons, A β-induced tau hyperphosphorylation and dendritic disruption can be attenuated by anti-A β antibodies or tau reduction using RNAi-targeting strategies [128-130].”

“This in turn causes local elevations in Ca2+ and disruption of synaptic function through impaired trafficking and/or synaptic anchoring of glutamate receptors (3, 127, 128).”

“It has also been suggested that mutations in presenilins affect intracellular calcium levels [132], and that elevations in intracellular calcium play key roles in promoting tau pathology [133] through activation of microtubule affinity-regulating kinase, cyclin-dependent kinase 5 or AMP-activated kinase [134].”

“Moreover, in cell culture experiments, applying exogenous Aβ to mouse primary neurons instigates τ phosphorylation and mislocalization to dendrites [163], and in human stem cell-derived neuronal cultures, overexpressing fAD mutations in APP and PS1 causes both plaque and tangle pathology [21].”

“Zempel and collaborators have shown that AβOs induce tau missorting, a phenomenon in which axonal taumoves to dendrites in hyperphosphorylated form, disrupting cytoskeletal organization and axonal transport (Zempel et al., 2010), ultimately instigating neuronal collapse.”

“1), 125–139 2011 The Authors (Zempel et al. 2010).”

“There is growing recognition that Ab42 oligomers induce Tau relocation from the axon to dendrites (Zempel et al., 2010), where it can act as a protein scaffold to facilitate the interaction of the Src kinase Fyn with NMDAR.”

“Another possibility is that excessive NMDAR activation and calcium influx triggered by oligomers [57,58,63,64] stimulate the activity of tyrosine phosphatases on IRS-1, as described for glutamate-induced neuronal damage [65], thus attenuating insulin signal transduction.”

“and is missorted from axons to the somatodendritic compartment, where it interferes with synaptic function [180,181].”

“In another study, Zempel et al. (2010) investigated differentiated primary hippocampal neurons for early localized changes following exposure to Aβ oligomers.”

“The activity-dependent transport mechanism into spines may be altered in anti- and pro-aggregant animals because of TauRD missorting to somatodendritic compartments (Zempel et al., 2010).”

“S3), and that Aβ causes Tau to mis-sort into the dendrite [16,17].”

“Light and electron microscopy set-ups, live-imaging conditions, photoconversion, and quantification procedures were described previously (Zempel et al , 2010; Li et al , 2011).”

“Similarly, exposure to oligomeric Ab promotes levels of tau in dendrites (Figure 2B, e), contributing to the increased levels of tau in this compartment in AD (Zempel et al., 2010).”

“In cultured neurons, mislocalization of an FTLD-tau mutant in postsynaptic spines depletes glutamate receptors (Hoover et al., 2010), and amyloid-b (Ab) oligomers induce missorting of tau into dendrites and spine retraction (Zempel et al., 2010).”

“…when neurons suffer from various neurotoxic insults, such as Aβ (Otth et al., 2002; Han et al., 2005; Zheng et al., 2005, 2010; Lopes et al., 2007; Zempel et al., 2010; Shukla et al., 2012), ischemia/hypoxia (Wen et al., 2007; Barros-Miñones et al., 2013), oxidative stress (Absalon et al.,…”

“These include increased phosphorylation and cytoplasmic and dendritic translocation, often linked to neurodegeneration which was Tau or even P-Tau dependent [26-38].”

“Therefore, MARKs may have regulatory functions in spine morphology and synaptic transmission, but may also act as critical mediators in Aβ-induced toxicity on synapses and dendritic spines (Zempel et al., 2010; Hayashi et al., 2011; Yu et al., 2012).”

“kinases, and finally, leading to neuronal loss [51, 52].”

“Two families of protein kinases contribute to tau phosphorylation, those that are proline directed and tend to phosphorylate serine and threonine motifs outside the microtubule binding domain and those that are KXGS-motif and non-proline directed and tend to phosphorylate within the repeat domain [14, 31].”

“They can inhibit hippocampal long-term potentiation in vivo [87], and cause abnormal tau phosphorylation and neuritic dystrophy [88-90].”

“In neurons which were acutely exposed to Aβ, Aβ initiated tau-mediated neurotoxicity by facilitating tau phosphorylation (60) and directing pathogenic tau species into dendritic spines (33), leading to spine collapse and dendritic degeneration.”

“Supporting the possible involvement of microtubule destabilization in AD pathogenesis, it has been recently reported [31] that natural oligomeric Ab, isolated from AD patients, disrupted the microtubule cytoskeleton and caused neuritic dystrophy (see also [67]).”

“The barrier breaks down when Tau is phosphorylated in its repeat domain and detached from microtubules, for example, by the kinase MARK/Par1.”

“Cultured rat neurons treated with oligomeric Ab also displayed translocation of tau from the axonal compartment to dendrites with concurrent increase of tau phosphorylation at specific epitopes (Zempel et al., 2010).”

“Although the associations revealed by these data are cross-sectional, the most likely interpretation based on previous animal studies (Zempel et al., 2010, 2013; Rozkalne et al., 2011; Cohen et al., 2013; Spires-Jones and Hyman, 2014; Koffie et al., 2019), is that amyloid-b deposition is followed…”

“…Ab-mediated synaptic plasticity deficits, from studies indicating that dendritic tau mediates Ab synaptotoxicity, and from a study that found synaptic tau phosphorylation in APP/PS1 mice (Roberson et al., 2007, 2011; Shipton et al., 2011; Ittner et al., 2010; Zempel et al., 2010; Wu et al., 2018).”

“It has been proposed that Aβ can trigger Ca influx (23), which activates calpain, a Ca-dependent protease that cleaves p35 to produce p25 for cdk5 activation (24).”

“…it is possible that a direct interaction between the two proteins may be involved in the induction of synaptic dysfunction as tau and Aβ coexist within synaptic compartments in AD brain (Hoover et al., 2010; Ittner et al., 2010; Zempel et al., 2010; Tai et al., 2012; Miller et al., 2014).”

“Tau has been implicated in A-induced cytoskeletal changes (King et al., 2006; Zempel et al., 2013), including deacetylation and polyglutamylation of tubulin and microtubule disassembly within dendrites of subpopulations of neurons (Zempel et al., 2010, 2013).”

“Treating primary neurons with physiological concentrations of amyloid-β induces synapse loss, which has recently been associated with tau mislocalization to dendrites [62].”

“Moreover, this redistribution of tau seems to be responsible for spine loss (Zempel et al., 2010).”

“Alternatively, the small decrease in Aβ levels observed in the present study may have affected levels of phosphorylated tau because Aβ directly precedes aberrant tau phosphorylation [54–56].”

“…the association of Ab oligomers with AVs in AD brains, we utilized the well-characterized A11 antibody that only recognizes soluble Ab oligomers, but not APP and its cleaved products C99, soluble monomer, or insoluble fibrils (Jimenez et al., 2008, 2011; Kayed et al., 2003; Zempel et al., 2010).”

“The reduction in mitochondria in the axon may be due to alterations in mitochondrial fission/fusion [3,5,6] and/or due to defects in the axonal transport of mitochondria [4,6,8,10–12].”

“Although Tau is found mainly in the neuronal axon and soma, previous work suggests that Tau is missorted and accumulated at synapses under pathological conditions (24, 28).”