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Rescue from tau-induced neuronal dysfunction produces insoluble tau oligomers.

Cowan CM, Quraishe S, Hands S, Sealey M, Mahajan S, Allan DW, Mudher A - Sci Rep (2015)

Bottom Line: Moreover, contrary to common belief, these tau oligomers were neither highly phosphorylated, and nor did they contain beta-pleated sheet structure.Whether these are inert or actively protective remains to be established.Nevertheless, this has wide implications for emerging therapeutic strategies such as those that target dissolution of tau oligomers as they may be ineffective or even counterproductive unless they act on the relevant toxic oligomeric tau species.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK.

ABSTRACT
Aggregation of highly phosphorylated tau is a hallmark of Alzheimer's disease and other tauopathies. Nevertheless, animal models demonstrate that tau-mediated dysfunction/toxicity may not require large tau aggregates but instead may be caused by soluble hyper-phosphorylated tau or by small tau oligomers. Challenging this widely held view, we use multiple techniques to show that insoluble tau oligomers form in conditions where tau-mediated dysfunction is rescued in vivo. This shows that tau oligomers are not necessarily always toxic. Furthermore, their formation correlates with increased tau levels, caused intriguingly, by either pharmacological or genetic inhibition of tau kinase glycogen-synthase-kinase-3beta (GSK-3β). Moreover, contrary to common belief, these tau oligomers were neither highly phosphorylated, and nor did they contain beta-pleated sheet structure. This may explain their lack of toxicity. Our study makes the novel observation that tau also forms non-toxic insoluble oligomers in vivo in addition to toxic oligomers, which have been reported by others. Whether these are inert or actively protective remains to be established. Nevertheless, this has wide implications for emerging therapeutic strategies such as those that target dissolution of tau oligomers as they may be ineffective or even counterproductive unless they act on the relevant toxic oligomeric tau species.

No MeSH data available.


Related in: MedlinePlus

Insoluble tau oligomers can be purified fromhTau0N3R-expressing Drosophila and were increaseddramatically after treatment with GSK-3β inhibitors.TEM of immuno-gold labelling for anti-hTau of S3 insoluble fractions showgranular tau oligomers comprised of hTau in all conditions expressing hTau{elavC155-Gal4/Y;UAS-hTau0N3R/ + }:(a) hTau, (b) hTau-Li, (c) hTau-AR. No suchstructures were detected in controls: d) wild-type. (See also Supplementary Fig. 8, for additionalcontrols of no sample labelled with anti h-Tau; and hTau labelled for anirrelevant rabbit polyclonal antibody, anti-v-glut). Scale bar in a(applicable toa–f) = 100 nm.(g–h); hundreds of such structures wereobserved in preparations from 18 pooled flies) Atomic Force Microscopy ofmaterial immuno-precipiated from fly head lysates using anti-hTau antibodyshows the appearance of numerous granular tau oligomers present after LiCltreatment (f) but only very sparse in untreatedhTau0N3R flies (e). Oligomer sizes were determinedby cross-sectional height analysis of individual oligomers. The heights ofthe oligomers ranged between 15 and 30 nm, with a mean height of17.07 nm (SD = 8.86). The widths of themajority of oligomers are between 20 and 40 nm and the averagewidth was calculated to be 20.6 nm(SD = 11.4). A minority of oligomers have a largerwidth than 30 nm but the height of the oligomers wasconsistently 30 nm or below. Scale bar ini = 1 μm.(g–i)’) Immuno-gold labeling forhTau in situ in sections of peripheral nerves from hTau-Li fliesdemonstrates labeled granular tau oligomers (arrows) within axons. Examplesare given at lower magnifications (g–i) in whichaxonal profiles are clearer, and at higher magnifications(g’–i’) in which GTOscan be seen more clearly. Scalebars = 100 nm.
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f3: Insoluble tau oligomers can be purified fromhTau0N3R-expressing Drosophila and were increaseddramatically after treatment with GSK-3β inhibitors.TEM of immuno-gold labelling for anti-hTau of S3 insoluble fractions showgranular tau oligomers comprised of hTau in all conditions expressing hTau{elavC155-Gal4/Y;UAS-hTau0N3R/ + }:(a) hTau, (b) hTau-Li, (c) hTau-AR. No suchstructures were detected in controls: d) wild-type. (See also Supplementary Fig. 8, for additionalcontrols of no sample labelled with anti h-Tau; and hTau labelled for anirrelevant rabbit polyclonal antibody, anti-v-glut). Scale bar in a(applicable toa–f) = 100 nm.(g–h); hundreds of such structures wereobserved in preparations from 18 pooled flies) Atomic Force Microscopy ofmaterial immuno-precipiated from fly head lysates using anti-hTau antibodyshows the appearance of numerous granular tau oligomers present after LiCltreatment (f) but only very sparse in untreatedhTau0N3R flies (e). Oligomer sizes were determinedby cross-sectional height analysis of individual oligomers. The heights ofthe oligomers ranged between 15 and 30 nm, with a mean height of17.07 nm (SD = 8.86). The widths of themajority of oligomers are between 20 and 40 nm and the averagewidth was calculated to be 20.6 nm(SD = 11.4). A minority of oligomers have a largerwidth than 30 nm but the height of the oligomers wasconsistently 30 nm or below. Scale bar ini = 1 μm.(g–i)’) Immuno-gold labeling forhTau in situ in sections of peripheral nerves from hTau-Li fliesdemonstrates labeled granular tau oligomers (arrows) within axons. Examplesare given at lower magnifications (g–i) in whichaxonal profiles are clearer, and at higher magnifications(g’–i’) in which GTOscan be seen more clearly. Scalebars = 100 nm.

Mentions: To further confirm that these structures contain tau, we performed immuno-gold EMon insoluble fractions. In all hTau0N3R-expressing conditions wedetected 20–50 nm granular oligomeric structuresdecorated with anti-hTau antibody (Fig. 3a–c).No labeling was evident in non-transgenic or antibody controls (Fig. 3d and Supplementary Fig.8). In line with the results from the EM (Fig.1) and biochemical analyses (Fig. 2), many moresuch structures were evident in the drug treated hTau0N3R animalsthan in untreated controls. These data strongly imply that insoluble taugranules, GTO-like structures, are forming in drug-treatedhTau0N3R flies.


Rescue from tau-induced neuronal dysfunction produces insoluble tau oligomers.

Cowan CM, Quraishe S, Hands S, Sealey M, Mahajan S, Allan DW, Mudher A - Sci Rep (2015)

Insoluble tau oligomers can be purified fromhTau0N3R-expressing Drosophila and were increaseddramatically after treatment with GSK-3β inhibitors.TEM of immuno-gold labelling for anti-hTau of S3 insoluble fractions showgranular tau oligomers comprised of hTau in all conditions expressing hTau{elavC155-Gal4/Y;UAS-hTau0N3R/ + }:(a) hTau, (b) hTau-Li, (c) hTau-AR. No suchstructures were detected in controls: d) wild-type. (See also Supplementary Fig. 8, for additionalcontrols of no sample labelled with anti h-Tau; and hTau labelled for anirrelevant rabbit polyclonal antibody, anti-v-glut). Scale bar in a(applicable toa–f) = 100 nm.(g–h); hundreds of such structures wereobserved in preparations from 18 pooled flies) Atomic Force Microscopy ofmaterial immuno-precipiated from fly head lysates using anti-hTau antibodyshows the appearance of numerous granular tau oligomers present after LiCltreatment (f) but only very sparse in untreatedhTau0N3R flies (e). Oligomer sizes were determinedby cross-sectional height analysis of individual oligomers. The heights ofthe oligomers ranged between 15 and 30 nm, with a mean height of17.07 nm (SD = 8.86). The widths of themajority of oligomers are between 20 and 40 nm and the averagewidth was calculated to be 20.6 nm(SD = 11.4). A minority of oligomers have a largerwidth than 30 nm but the height of the oligomers wasconsistently 30 nm or below. Scale bar ini = 1 μm.(g–i)’) Immuno-gold labeling forhTau in situ in sections of peripheral nerves from hTau-Li fliesdemonstrates labeled granular tau oligomers (arrows) within axons. Examplesare given at lower magnifications (g–i) in whichaxonal profiles are clearer, and at higher magnifications(g’–i’) in which GTOscan be seen more clearly. Scalebars = 100 nm.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4660438&req=5

f3: Insoluble tau oligomers can be purified fromhTau0N3R-expressing Drosophila and were increaseddramatically after treatment with GSK-3β inhibitors.TEM of immuno-gold labelling for anti-hTau of S3 insoluble fractions showgranular tau oligomers comprised of hTau in all conditions expressing hTau{elavC155-Gal4/Y;UAS-hTau0N3R/ + }:(a) hTau, (b) hTau-Li, (c) hTau-AR. No suchstructures were detected in controls: d) wild-type. (See also Supplementary Fig. 8, for additionalcontrols of no sample labelled with anti h-Tau; and hTau labelled for anirrelevant rabbit polyclonal antibody, anti-v-glut). Scale bar in a(applicable toa–f) = 100 nm.(g–h); hundreds of such structures wereobserved in preparations from 18 pooled flies) Atomic Force Microscopy ofmaterial immuno-precipiated from fly head lysates using anti-hTau antibodyshows the appearance of numerous granular tau oligomers present after LiCltreatment (f) but only very sparse in untreatedhTau0N3R flies (e). Oligomer sizes were determinedby cross-sectional height analysis of individual oligomers. The heights ofthe oligomers ranged between 15 and 30 nm, with a mean height of17.07 nm (SD = 8.86). The widths of themajority of oligomers are between 20 and 40 nm and the averagewidth was calculated to be 20.6 nm(SD = 11.4). A minority of oligomers have a largerwidth than 30 nm but the height of the oligomers wasconsistently 30 nm or below. Scale bar ini = 1 μm.(g–i)’) Immuno-gold labeling forhTau in situ in sections of peripheral nerves from hTau-Li fliesdemonstrates labeled granular tau oligomers (arrows) within axons. Examplesare given at lower magnifications (g–i) in whichaxonal profiles are clearer, and at higher magnifications(g’–i’) in which GTOscan be seen more clearly. Scalebars = 100 nm.
Mentions: To further confirm that these structures contain tau, we performed immuno-gold EMon insoluble fractions. In all hTau0N3R-expressing conditions wedetected 20–50 nm granular oligomeric structuresdecorated with anti-hTau antibody (Fig. 3a–c).No labeling was evident in non-transgenic or antibody controls (Fig. 3d and Supplementary Fig.8). In line with the results from the EM (Fig.1) and biochemical analyses (Fig. 2), many moresuch structures were evident in the drug treated hTau0N3R animalsthan in untreated controls. These data strongly imply that insoluble taugranules, GTO-like structures, are forming in drug-treatedhTau0N3R flies.

Bottom Line: Moreover, contrary to common belief, these tau oligomers were neither highly phosphorylated, and nor did they contain beta-pleated sheet structure.Whether these are inert or actively protective remains to be established.Nevertheless, this has wide implications for emerging therapeutic strategies such as those that target dissolution of tau oligomers as they may be ineffective or even counterproductive unless they act on the relevant toxic oligomeric tau species.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK.

ABSTRACT
Aggregation of highly phosphorylated tau is a hallmark of Alzheimer's disease and other tauopathies. Nevertheless, animal models demonstrate that tau-mediated dysfunction/toxicity may not require large tau aggregates but instead may be caused by soluble hyper-phosphorylated tau or by small tau oligomers. Challenging this widely held view, we use multiple techniques to show that insoluble tau oligomers form in conditions where tau-mediated dysfunction is rescued in vivo. This shows that tau oligomers are not necessarily always toxic. Furthermore, their formation correlates with increased tau levels, caused intriguingly, by either pharmacological or genetic inhibition of tau kinase glycogen-synthase-kinase-3beta (GSK-3β). Moreover, contrary to common belief, these tau oligomers were neither highly phosphorylated, and nor did they contain beta-pleated sheet structure. This may explain their lack of toxicity. Our study makes the novel observation that tau also forms non-toxic insoluble oligomers in vivo in addition to toxic oligomers, which have been reported by others. Whether these are inert or actively protective remains to be established. Nevertheless, this has wide implications for emerging therapeutic strategies such as those that target dissolution of tau oligomers as they may be ineffective or even counterproductive unless they act on the relevant toxic oligomeric tau species.

No MeSH data available.


Related in: MedlinePlus