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The formation of tau pore-like structures is prevalent and cell specific: possible implications for the disease phenotypes.

Lasagna-Reeves CA, Sengupta U, Castillo-Carranza D, Gerson JE, Guerrero-Munoz M, Troncoso JC, Jackson GR, Kayed R - Acta Neuropathol Commun (2014)

Bottom Line: Due to conflicting results regarding a correlation between the presence of NFTs and disease progression, the mechanism linking pathological tau aggregation with cell death is poorly understood.Furthermore, we found that APFs are preceded by tau oligomers and do not go on to form NFTs, evading fibrillar fate.Collectively, our results demonstrate that in vivo APF formation depends on mutations in tau, phosphorylation levels, and cell type.

View Article: PubMed Central - PubMed

Affiliation: Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA. rakayed@utmb.edu.

ABSTRACT
Pathological aggregation of the microtubule-associated protein tau and subsequent accumulation of neurofibrillary tangles (NFTs) or other tau-containing inclusions are defining histopathological features of many neurodegenerative diseases, which are collectively known as tauopathies. Due to conflicting results regarding a correlation between the presence of NFTs and disease progression, the mechanism linking pathological tau aggregation with cell death is poorly understood. An emerging view is that NFTs are not the toxic entity in tauopathies; rather, tau intermediates between monomers and NFTs are pathogenic. Several proteins associated with neurodegenerative diseases, such as β-amyloid (Aβ) and α-synuclein, have the tendency to form pore-like amyloid structures (annular protofibrils, APFs) that mimic the membrane-disrupting properties of pore-forming protein toxins. The present study examined the similarities of tau APFs with other tau amyloid species and showed for the first time the presence of tau APFs in brain tissue from patients with progressive supranuclear palsy (PSP) and dementia with Lewy bodies (DLB), as well as in the P301L mouse model, which overexpresses mutated tau. Furthermore, we found that APFs are preceded by tau oligomers and do not go on to form NFTs, evading fibrillar fate. Collectively, our results demonstrate that in vivo APF formation depends on mutations in tau, phosphorylation levels, and cell type. These findings establish the pathological significance of tau APFs in vivo and highlight their suitability as therapeutic targets for several neurodegenerative tauopathies.

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In vitroformation of tau APFs. Tau oligomers used to prepare tau APFs were characterized by EM (a) and AFM (b). Tau APFs were also imaged by EM (c) and AFM (d). Tau APFs were recognized by the αAPF antibody on dot blot, which did not recognize recombinant tau monomers, oligomers, or fibrils. Tau oligomers were recognized by T22, and all tau species were detected by Tau-5 (e). A distinct peak near 670 nm on HPLC revealed that tau APFs are formed by 10–12 tau monomers (f). The scale bars for a and b correspond to 100 nm, for c 20 nm, and for d 40 nm. White arrowheads indicate tau APF formation.
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Fig1: In vitroformation of tau APFs. Tau oligomers used to prepare tau APFs were characterized by EM (a) and AFM (b). Tau APFs were also imaged by EM (c) and AFM (d). Tau APFs were recognized by the αAPF antibody on dot blot, which did not recognize recombinant tau monomers, oligomers, or fibrils. Tau oligomers were recognized by T22, and all tau species were detected by Tau-5 (e). A distinct peak near 670 nm on HPLC revealed that tau APFs are formed by 10–12 tau monomers (f). The scale bars for a and b correspond to 100 nm, for c 20 nm, and for d 40 nm. White arrowheads indicate tau APF formation.

Mentions: To determine whether tau forms APFs similarly to other amyloid proteins, full-length human tau protein was used to prepare tau oligomers as previously described [37, 38]. The presence of tau oligomers was confirmed by both EM (Figure 1a) and AFM (Figure 1b) analysis. Using tau oligomers as the starting material, APFs were prepared with 5% hexane and characterized using EM (Figure 1c) and AFM (Figure 1d). As we previously demonstrated, liposomes can catalyze the conversion of oligomers to APFs under more physiologically relevant conditions than treatment with 5% hexane [31]. When liposomes were reconstituted with tau oligomers and incubated for 2 h, APFs were detected by AFM (Additional file 1: Figure S1a). The formation of tau APFs was also confirmed by dot blot using the APF-specific antibody, αAPF, which did not recognize tau monomers, oligomers, or fibrils (Figure 1e). The selectivity of αAPF for tau APFs was confirmed by competitive ELISA (Additional file 1: Figure S1b). The conformational tau antibody T22 was used to detect tau oligomers in dot-blot (Figure 1e). The selectivity of T22 for tau oligomers has been previously described [40]. Nevertheless, we confirmed its selectivity for the oligomeric form of tau by direct and competitive ELISAs (Additional file 1: Figure S1c and d). The HPLC analysis of tau APF prepared in vitro showed a peak over 670 KDa, suggesting that APFs range from decamers to dodecamers of tau monomers (Figure 1f). We compared the toxicity of tau APFs and oligomers and found that APFs are significantly less toxic (Additional file 1: Figure S1e). As we previously reported for Aβ and α-synuclein [31], tau APFs are less toxic than the oligomers used to prepared them. Moreover, whenever cells were treated with tau oligomers we observed the formation of tau APFs whenever cells were treated with tau oligomers, suggesting that one of the toxic mechanisms of tau oligomers is APF formation (Additional file 1: Figure S1f).Figure 1


The formation of tau pore-like structures is prevalent and cell specific: possible implications for the disease phenotypes.

Lasagna-Reeves CA, Sengupta U, Castillo-Carranza D, Gerson JE, Guerrero-Munoz M, Troncoso JC, Jackson GR, Kayed R - Acta Neuropathol Commun (2014)

In vitroformation of tau APFs. Tau oligomers used to prepare tau APFs were characterized by EM (a) and AFM (b). Tau APFs were also imaged by EM (c) and AFM (d). Tau APFs were recognized by the αAPF antibody on dot blot, which did not recognize recombinant tau monomers, oligomers, or fibrils. Tau oligomers were recognized by T22, and all tau species were detected by Tau-5 (e). A distinct peak near 670 nm on HPLC revealed that tau APFs are formed by 10–12 tau monomers (f). The scale bars for a and b correspond to 100 nm, for c 20 nm, and for d 40 nm. White arrowheads indicate tau APF formation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Fig1: In vitroformation of tau APFs. Tau oligomers used to prepare tau APFs were characterized by EM (a) and AFM (b). Tau APFs were also imaged by EM (c) and AFM (d). Tau APFs were recognized by the αAPF antibody on dot blot, which did not recognize recombinant tau monomers, oligomers, or fibrils. Tau oligomers were recognized by T22, and all tau species were detected by Tau-5 (e). A distinct peak near 670 nm on HPLC revealed that tau APFs are formed by 10–12 tau monomers (f). The scale bars for a and b correspond to 100 nm, for c 20 nm, and for d 40 nm. White arrowheads indicate tau APF formation.
Mentions: To determine whether tau forms APFs similarly to other amyloid proteins, full-length human tau protein was used to prepare tau oligomers as previously described [37, 38]. The presence of tau oligomers was confirmed by both EM (Figure 1a) and AFM (Figure 1b) analysis. Using tau oligomers as the starting material, APFs were prepared with 5% hexane and characterized using EM (Figure 1c) and AFM (Figure 1d). As we previously demonstrated, liposomes can catalyze the conversion of oligomers to APFs under more physiologically relevant conditions than treatment with 5% hexane [31]. When liposomes were reconstituted with tau oligomers and incubated for 2 h, APFs were detected by AFM (Additional file 1: Figure S1a). The formation of tau APFs was also confirmed by dot blot using the APF-specific antibody, αAPF, which did not recognize tau monomers, oligomers, or fibrils (Figure 1e). The selectivity of αAPF for tau APFs was confirmed by competitive ELISA (Additional file 1: Figure S1b). The conformational tau antibody T22 was used to detect tau oligomers in dot-blot (Figure 1e). The selectivity of T22 for tau oligomers has been previously described [40]. Nevertheless, we confirmed its selectivity for the oligomeric form of tau by direct and competitive ELISAs (Additional file 1: Figure S1c and d). The HPLC analysis of tau APF prepared in vitro showed a peak over 670 KDa, suggesting that APFs range from decamers to dodecamers of tau monomers (Figure 1f). We compared the toxicity of tau APFs and oligomers and found that APFs are significantly less toxic (Additional file 1: Figure S1e). As we previously reported for Aβ and α-synuclein [31], tau APFs are less toxic than the oligomers used to prepared them. Moreover, whenever cells were treated with tau oligomers we observed the formation of tau APFs whenever cells were treated with tau oligomers, suggesting that one of the toxic mechanisms of tau oligomers is APF formation (Additional file 1: Figure S1f).Figure 1

Bottom Line: Due to conflicting results regarding a correlation between the presence of NFTs and disease progression, the mechanism linking pathological tau aggregation with cell death is poorly understood.Furthermore, we found that APFs are preceded by tau oligomers and do not go on to form NFTs, evading fibrillar fate.Collectively, our results demonstrate that in vivo APF formation depends on mutations in tau, phosphorylation levels, and cell type.

View Article: PubMed Central - PubMed

Affiliation: Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA. rakayed@utmb.edu.

ABSTRACT
Pathological aggregation of the microtubule-associated protein tau and subsequent accumulation of neurofibrillary tangles (NFTs) or other tau-containing inclusions are defining histopathological features of many neurodegenerative diseases, which are collectively known as tauopathies. Due to conflicting results regarding a correlation between the presence of NFTs and disease progression, the mechanism linking pathological tau aggregation with cell death is poorly understood. An emerging view is that NFTs are not the toxic entity in tauopathies; rather, tau intermediates between monomers and NFTs are pathogenic. Several proteins associated with neurodegenerative diseases, such as β-amyloid (Aβ) and α-synuclein, have the tendency to form pore-like amyloid structures (annular protofibrils, APFs) that mimic the membrane-disrupting properties of pore-forming protein toxins. The present study examined the similarities of tau APFs with other tau amyloid species and showed for the first time the presence of tau APFs in brain tissue from patients with progressive supranuclear palsy (PSP) and dementia with Lewy bodies (DLB), as well as in the P301L mouse model, which overexpresses mutated tau. Furthermore, we found that APFs are preceded by tau oligomers and do not go on to form NFTs, evading fibrillar fate. Collectively, our results demonstrate that in vivo APF formation depends on mutations in tau, phosphorylation levels, and cell type. These findings establish the pathological significance of tau APFs in vivo and highlight their suitability as therapeutic targets for several neurodegenerative tauopathies.

Show MeSH
Related in: MedlinePlus