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Analysis of in vivo turnover of tau in a mouse model of tauopathy.

Yamada K, Patel TK, Hochgräfe K, Mahan TE, Jiang H, Stewart FR, Mandelkow EM, Holtzman DM - Mol Neurodegener (2015)

Bottom Line: This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau.Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region.These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033, Japan. yamadaka@m.u-tokyo.ac.jp.

ABSTRACT

Background: Intracellular accumulation of tau as neurofibrillary tangles (NFTs) is the hallmark of Alzheimer's disease (AD) as well as in other tauopathies. Tau is present not only in the cytoplasm but also in the extracellular space such as cerebrospinal fluid (CSF) and brain interstitial fluid (ISF). Although clearance is one critical parameter leading to such intracellular/extracellular tau accumulation, in vivo turnover of tau has not been well characterized. The current study has attempted to precisely determine in vivo turnover rates of tau utilizing tet-off regulatable mice. In particular, we assessed intracellular tau and extracellular tau, soluble tau, insoluble tau and phosphorylated tau at certain sites utilizing a combination of in vivo microdialysis, biochemical analysis and specific ELISAs recognizing each species. To examine the effect of a tauopathy-associated mutation on tau clearance, half-lives of various tau species were compared between the mice with a FTDP-17 mutation that induces β-sheet formation, ΔK280 mutation (pro-aggregant mice) and control mice with additional β-sheet breaking mutations (anti-aggregant mice).

Results: Here we report that tau is metabolized at much slower turnover rates in vivo than in cell culture. We found that insoluble tau in pro-aggregant mice had a significantly slower half-life (t1/2 = ~34.2 days) than soluble tau (t1/2 = ~9.7 days). In contrast, soluble tau phosphorylated in the proline rich region was cleared faster than total soluble tau. When comparing pro-aggregant mice to anti-agregant mice, turnover rates of soluble tau species were not significantly different.

Conclusions: The current study provides a comprehensive description of in vivo turnover of various tau species present in mice that express human tau. The turnover rate of soluble tau was not significantly altered between pro-aggregant mice and anti-aggregant mice. This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau. In contrast, different tau species displayed different half-lives. Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region. These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.

No MeSH data available.


Related in: MedlinePlus

Turnover of soluble tau in pro-aggregant mice and anti-aggregant mice. a Doxycycline specifically reduced human tau in intracellular fractions of pro-aggregant mice. Human (black bars) and murine tau levels (white bars) in intracellular soluble fractions following doxycycline treatment were measured (n = 4 for day 10, n = 5 for day 4 and day 18, n = 7 for day 8, n = 12 for day 0. ****p < 0.0001) in pro-aggregant mice. b Doxycycline specifically reduced human tau in ISF of pro-aggregant mice. The levels of human tau (black bars) and lactate (white bars) in ISF of pro-aggregant following doxycycline treatment were measured (n = 6 for day 0, n = 5 for day 3, n = 4 for day 7, n = 4 for day 9, n = 5 for day 17, n = 4-6/group). c Semi-log plot of intracellular (black circles) and extracellular soluble human tau (white circles) changes (Log % soluble human tau) over time in pro-aggregant mice d Phosphorylated tau showed different clearance kinetics in brain of pro-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray squares, Log % soluble pT231/pS235 tau, white squares, Log % soluble murine and human pS202/pT205, white triangles, Log % soluble human pS396) over time in pro-aggregant mice. e Phosphorylated tau showed different clearance kinetics in the brain of anti-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray triangles, Log % phosphorylated murine and human tau pS202/pT205, white squares, Log % soluble human pS396) over time in anti-aggregant mice
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Fig2: Turnover of soluble tau in pro-aggregant mice and anti-aggregant mice. a Doxycycline specifically reduced human tau in intracellular fractions of pro-aggregant mice. Human (black bars) and murine tau levels (white bars) in intracellular soluble fractions following doxycycline treatment were measured (n = 4 for day 10, n = 5 for day 4 and day 18, n = 7 for day 8, n = 12 for day 0. ****p < 0.0001) in pro-aggregant mice. b Doxycycline specifically reduced human tau in ISF of pro-aggregant mice. The levels of human tau (black bars) and lactate (white bars) in ISF of pro-aggregant following doxycycline treatment were measured (n = 6 for day 0, n = 5 for day 3, n = 4 for day 7, n = 4 for day 9, n = 5 for day 17, n = 4-6/group). c Semi-log plot of intracellular (black circles) and extracellular soluble human tau (white circles) changes (Log % soluble human tau) over time in pro-aggregant mice d Phosphorylated tau showed different clearance kinetics in brain of pro-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray squares, Log % soluble pT231/pS235 tau, white squares, Log % soluble murine and human pS202/pT205, white triangles, Log % soluble human pS396) over time in pro-aggregant mice. e Phosphorylated tau showed different clearance kinetics in the brain of anti-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray triangles, Log % phosphorylated murine and human tau pS202/pT205, white squares, Log % soluble human pS396) over time in anti-aggregant mice

Mentions: By using hippocampal soluble fractions, we first investigated turnover rates of intracellular soluble tau in 16–17 month old pro-aggregant mice. In these fractions, doxycycline specifically reduced human but not murine tau as expected (Fig. 2a). A linear regression of semi-log plot (Fig. 2c) revealed that the estimated half-life of intracellular soluble tau in pro-aggregant mice was 9.7 days (Table 1). The half-life of tau determined in cell culture ranges from ~5 to 60 h [9–12, 24]. The significantly longer half-life of tau indicates that tau metabolism is different between cells and the in vivo environment.Fig. 2


Analysis of in vivo turnover of tau in a mouse model of tauopathy.

Yamada K, Patel TK, Hochgräfe K, Mahan TE, Jiang H, Stewart FR, Mandelkow EM, Holtzman DM - Mol Neurodegener (2015)

Turnover of soluble tau in pro-aggregant mice and anti-aggregant mice. a Doxycycline specifically reduced human tau in intracellular fractions of pro-aggregant mice. Human (black bars) and murine tau levels (white bars) in intracellular soluble fractions following doxycycline treatment were measured (n = 4 for day 10, n = 5 for day 4 and day 18, n = 7 for day 8, n = 12 for day 0. ****p < 0.0001) in pro-aggregant mice. b Doxycycline specifically reduced human tau in ISF of pro-aggregant mice. The levels of human tau (black bars) and lactate (white bars) in ISF of pro-aggregant following doxycycline treatment were measured (n = 6 for day 0, n = 5 for day 3, n = 4 for day 7, n = 4 for day 9, n = 5 for day 17, n = 4-6/group). c Semi-log plot of intracellular (black circles) and extracellular soluble human tau (white circles) changes (Log % soluble human tau) over time in pro-aggregant mice d Phosphorylated tau showed different clearance kinetics in brain of pro-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray squares, Log % soluble pT231/pS235 tau, white squares, Log % soluble murine and human pS202/pT205, white triangles, Log % soluble human pS396) over time in pro-aggregant mice. e Phosphorylated tau showed different clearance kinetics in the brain of anti-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray triangles, Log % phosphorylated murine and human tau pS202/pT205, white squares, Log % soluble human pS396) over time in anti-aggregant mice
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4621881&req=5

Fig2: Turnover of soluble tau in pro-aggregant mice and anti-aggregant mice. a Doxycycline specifically reduced human tau in intracellular fractions of pro-aggregant mice. Human (black bars) and murine tau levels (white bars) in intracellular soluble fractions following doxycycline treatment were measured (n = 4 for day 10, n = 5 for day 4 and day 18, n = 7 for day 8, n = 12 for day 0. ****p < 0.0001) in pro-aggregant mice. b Doxycycline specifically reduced human tau in ISF of pro-aggregant mice. The levels of human tau (black bars) and lactate (white bars) in ISF of pro-aggregant following doxycycline treatment were measured (n = 6 for day 0, n = 5 for day 3, n = 4 for day 7, n = 4 for day 9, n = 5 for day 17, n = 4-6/group). c Semi-log plot of intracellular (black circles) and extracellular soluble human tau (white circles) changes (Log % soluble human tau) over time in pro-aggregant mice d Phosphorylated tau showed different clearance kinetics in brain of pro-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray squares, Log % soluble pT231/pS235 tau, white squares, Log % soluble murine and human pS202/pT205, white triangles, Log % soluble human pS396) over time in pro-aggregant mice. e Phosphorylated tau showed different clearance kinetics in the brain of anti-aggregant mice. Semi-log plot of soluble human tau (white circles, Log % soluble human tau), and phosphorylated soluble tau (black circles, Log % soluble human pS202/pT205, gray triangles, Log % phosphorylated murine and human tau pS202/pT205, white squares, Log % soluble human pS396) over time in anti-aggregant mice
Mentions: By using hippocampal soluble fractions, we first investigated turnover rates of intracellular soluble tau in 16–17 month old pro-aggregant mice. In these fractions, doxycycline specifically reduced human but not murine tau as expected (Fig. 2a). A linear regression of semi-log plot (Fig. 2c) revealed that the estimated half-life of intracellular soluble tau in pro-aggregant mice was 9.7 days (Table 1). The half-life of tau determined in cell culture ranges from ~5 to 60 h [9–12, 24]. The significantly longer half-life of tau indicates that tau metabolism is different between cells and the in vivo environment.Fig. 2

Bottom Line: This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau.Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region.These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033, Japan. yamadaka@m.u-tokyo.ac.jp.

ABSTRACT

Background: Intracellular accumulation of tau as neurofibrillary tangles (NFTs) is the hallmark of Alzheimer's disease (AD) as well as in other tauopathies. Tau is present not only in the cytoplasm but also in the extracellular space such as cerebrospinal fluid (CSF) and brain interstitial fluid (ISF). Although clearance is one critical parameter leading to such intracellular/extracellular tau accumulation, in vivo turnover of tau has not been well characterized. The current study has attempted to precisely determine in vivo turnover rates of tau utilizing tet-off regulatable mice. In particular, we assessed intracellular tau and extracellular tau, soluble tau, insoluble tau and phosphorylated tau at certain sites utilizing a combination of in vivo microdialysis, biochemical analysis and specific ELISAs recognizing each species. To examine the effect of a tauopathy-associated mutation on tau clearance, half-lives of various tau species were compared between the mice with a FTDP-17 mutation that induces β-sheet formation, ΔK280 mutation (pro-aggregant mice) and control mice with additional β-sheet breaking mutations (anti-aggregant mice).

Results: Here we report that tau is metabolized at much slower turnover rates in vivo than in cell culture. We found that insoluble tau in pro-aggregant mice had a significantly slower half-life (t1/2 = ~34.2 days) than soluble tau (t1/2 = ~9.7 days). In contrast, soluble tau phosphorylated in the proline rich region was cleared faster than total soluble tau. When comparing pro-aggregant mice to anti-agregant mice, turnover rates of soluble tau species were not significantly different.

Conclusions: The current study provides a comprehensive description of in vivo turnover of various tau species present in mice that express human tau. The turnover rate of soluble tau was not significantly altered between pro-aggregant mice and anti-aggregant mice. This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau. In contrast, different tau species displayed different half-lives. Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region. These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.

No MeSH data available.


Related in: MedlinePlus