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Macroautophagy--a novel Beta-amyloid peptide-generating pathway activated in Alzheimer's disease.

Yu WH, Cuervo AM, Kumar A, Peterhoff CM, Schmidt SD, Lee JH, Mohan PS, Mercken M, Farmery MR, Tjernberg LO, Jiang Y, Duff K, Uchiyama Y, Näslund J, Mathews PM, Cataldo AM, Nixon RA - J. Cell Biol. (2005)

Bottom Line: Purified AVs contain APP and beta-cleaved APP and are highly enriched in PS1, nicastrin, and PS-dependent gamma-secretase activity.Inducing or inhibiting macroautophagy in neuronal and nonneuronal cells by modulating mammalian target of rapamycin kinase elicits parallel changes in AV proliferation and Abeta production.Our results, therefore, link beta-amyloidogenic and cell survival pathways through macroautophagy, which is activated and is abnormal in AD.

View Article: PubMed Central - PubMed

Affiliation: Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY 10962, USA.

ABSTRACT
Macroautophagy, which is a lysosomal pathway for the turnover of organelles and long-lived proteins, is a key determinant of cell survival and longevity. In this study, we show that neuronal macroautophagy is induced early in Alzheimer's disease (AD) and before beta-amyloid (Abeta) deposits extracellularly in the presenilin (PS) 1/Abeta precursor protein (APP) mouse model of beta-amyloidosis. Subsequently, autophagosomes and late autophagic vacuoles (AVs) accumulate markedly in dystrophic dendrites, implying an impaired maturation of AVs to lysosomes. Immunolabeling identifies AVs in the brain as a major reservoir of intracellular Abeta. Purified AVs contain APP and beta-cleaved APP and are highly enriched in PS1, nicastrin, and PS-dependent gamma-secretase activity. Inducing or inhibiting macroautophagy in neuronal and nonneuronal cells by modulating mammalian target of rapamycin kinase elicits parallel changes in AV proliferation and Abeta production. Our results, therefore, link beta-amyloidogenic and cell survival pathways through macroautophagy, which is activated and is abnormal in AD.

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Identification of macroautophagy in the hippocampus of predepositing PS1/APP mice. Ultrastructural inspection of brain tissue from PS1/APP mice (A–D) shows that AVs (A and B, arrows) are five times more frequent in the dendrites of 8-wk-old PS1/APP than in those of age-matched NTg mice. The frequency of AVs per EM field (C) and mean number of AVs per EM field (D) within the hippocampal molecular layer (n = 3) are shown. LC3 immunoblot and analysis (E) and immunofluorescent labeling (F–K) of the hippocampal dendrites (brackets) in 8–9-wk-old PS1/APP and NTg mice show LC3-II elevation (P < 0.05) in 8-wk-old PS1/APP compared with NTg mice (E). (D) *, P < 0.001. (E) *, P < 0.05. Error bars represent SEM. LC3 immunoreactivity in pyramidal cell dendrites is increased in 9-mo-old (F–H) and 9-wk-old (I–K) PS1/APP mice and frequently exhibits a punctate labeling pattern, which is more evident at 9 mo than at 9 wk (H and K, arrows) and is uncommon in NTg mice (F and I). Bars (F, G, I, and J), 20 μm; (H and K), 10 μm.
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fig2: Identification of macroautophagy in the hippocampus of predepositing PS1/APP mice. Ultrastructural inspection of brain tissue from PS1/APP mice (A–D) shows that AVs (A and B, arrows) are five times more frequent in the dendrites of 8-wk-old PS1/APP than in those of age-matched NTg mice. The frequency of AVs per EM field (C) and mean number of AVs per EM field (D) within the hippocampal molecular layer (n = 3) are shown. LC3 immunoblot and analysis (E) and immunofluorescent labeling (F–K) of the hippocampal dendrites (brackets) in 8–9-wk-old PS1/APP and NTg mice show LC3-II elevation (P < 0.05) in 8-wk-old PS1/APP compared with NTg mice (E). (D) *, P < 0.001. (E) *, P < 0.05. Error bars represent SEM. LC3 immunoreactivity in pyramidal cell dendrites is increased in 9-mo-old (F–H) and 9-wk-old (I–K) PS1/APP mice and frequently exhibits a punctate labeling pattern, which is more evident at 9 mo than at 9 wk (H and K, arrows) and is uncommon in NTg mice (F and I). Bars (F, G, I, and J), 20 μm; (H and K), 10 μm.

Mentions: Elevation of LC3-II in AD brains at preclinical stages of AD (Fig. 1 E) suggested that macroautophagic induction is an early response in the disease process. To investigate early induction in PS1/APP mice, we also analyzed LC3-II levels in these mice at an age (8–9 wk) that precedes known neuropathology, including Aβ deposition (“predepositing” mice; Matsuoka et al., 2001). AVs were visible in the cell bodies and neurites of predepositing PS1/APP mice (Fig. 2, A and B) but were significantly less frequent in NTg animals (Fig. 2 C). Based on the EM fields that were surveyed from NTg and PS1/APP mice at 8–9 wk, >95% of images from NTg mice had zero or one AV present, whereas >80% of EM images from PS1/APP mice had at least one AV per field (Fig. 2 C). Quantitative ultrastructural analyses confirmed an increased incidence of AVs in the neocortex of these predepositing PS1/APP mice, where AVs were fivefold more numerous (n = 3 each; P < 0.001) than in age-matched NTg mice (Fig. 2 D). LC3-II levels in predepositing PS1/APP brains, as determined by Western blot analysis, were modestly yet significantly elevated (n = 6; P < 0.05) in the absence of a significant change in LC3-I levels (Fig. 2 E). Furthermore, LC3 immunoreactivity, which was present predominantly in neuronal cell bodies in NTg mice (Fig. 2, F and I), was distributed to both hippocampal cell bodies and dendrites in 9-mo- (Fig. 2, G and H) and 9-wk-old (Fig. 2, J and K) PS1/APP mice. The staining pattern for LC3 in many dendrites was more frequently punctate in PS1/APP than in NTg mice (Fig. 2, I and J), although less so than in older PS1/APP mice (Fig. 2, compare H with K). Collectively, these observations demonstrate that macroautophagy is induced at a prepathological stage of disease in PS1/APP mice and that, in addition, different subtypes of AVs accumulate pathologically as neuritic dystrophy develops in older mice, as in AD.


Macroautophagy--a novel Beta-amyloid peptide-generating pathway activated in Alzheimer's disease.

Yu WH, Cuervo AM, Kumar A, Peterhoff CM, Schmidt SD, Lee JH, Mohan PS, Mercken M, Farmery MR, Tjernberg LO, Jiang Y, Duff K, Uchiyama Y, Näslund J, Mathews PM, Cataldo AM, Nixon RA - J. Cell Biol. (2005)

Identification of macroautophagy in the hippocampus of predepositing PS1/APP mice. Ultrastructural inspection of brain tissue from PS1/APP mice (A–D) shows that AVs (A and B, arrows) are five times more frequent in the dendrites of 8-wk-old PS1/APP than in those of age-matched NTg mice. The frequency of AVs per EM field (C) and mean number of AVs per EM field (D) within the hippocampal molecular layer (n = 3) are shown. LC3 immunoblot and analysis (E) and immunofluorescent labeling (F–K) of the hippocampal dendrites (brackets) in 8–9-wk-old PS1/APP and NTg mice show LC3-II elevation (P < 0.05) in 8-wk-old PS1/APP compared with NTg mice (E). (D) *, P < 0.001. (E) *, P < 0.05. Error bars represent SEM. LC3 immunoreactivity in pyramidal cell dendrites is increased in 9-mo-old (F–H) and 9-wk-old (I–K) PS1/APP mice and frequently exhibits a punctate labeling pattern, which is more evident at 9 mo than at 9 wk (H and K, arrows) and is uncommon in NTg mice (F and I). Bars (F, G, I, and J), 20 μm; (H and K), 10 μm.
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Related In: Results  -  Collection

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fig2: Identification of macroautophagy in the hippocampus of predepositing PS1/APP mice. Ultrastructural inspection of brain tissue from PS1/APP mice (A–D) shows that AVs (A and B, arrows) are five times more frequent in the dendrites of 8-wk-old PS1/APP than in those of age-matched NTg mice. The frequency of AVs per EM field (C) and mean number of AVs per EM field (D) within the hippocampal molecular layer (n = 3) are shown. LC3 immunoblot and analysis (E) and immunofluorescent labeling (F–K) of the hippocampal dendrites (brackets) in 8–9-wk-old PS1/APP and NTg mice show LC3-II elevation (P < 0.05) in 8-wk-old PS1/APP compared with NTg mice (E). (D) *, P < 0.001. (E) *, P < 0.05. Error bars represent SEM. LC3 immunoreactivity in pyramidal cell dendrites is increased in 9-mo-old (F–H) and 9-wk-old (I–K) PS1/APP mice and frequently exhibits a punctate labeling pattern, which is more evident at 9 mo than at 9 wk (H and K, arrows) and is uncommon in NTg mice (F and I). Bars (F, G, I, and J), 20 μm; (H and K), 10 μm.
Mentions: Elevation of LC3-II in AD brains at preclinical stages of AD (Fig. 1 E) suggested that macroautophagic induction is an early response in the disease process. To investigate early induction in PS1/APP mice, we also analyzed LC3-II levels in these mice at an age (8–9 wk) that precedes known neuropathology, including Aβ deposition (“predepositing” mice; Matsuoka et al., 2001). AVs were visible in the cell bodies and neurites of predepositing PS1/APP mice (Fig. 2, A and B) but were significantly less frequent in NTg animals (Fig. 2 C). Based on the EM fields that were surveyed from NTg and PS1/APP mice at 8–9 wk, >95% of images from NTg mice had zero or one AV present, whereas >80% of EM images from PS1/APP mice had at least one AV per field (Fig. 2 C). Quantitative ultrastructural analyses confirmed an increased incidence of AVs in the neocortex of these predepositing PS1/APP mice, where AVs were fivefold more numerous (n = 3 each; P < 0.001) than in age-matched NTg mice (Fig. 2 D). LC3-II levels in predepositing PS1/APP brains, as determined by Western blot analysis, were modestly yet significantly elevated (n = 6; P < 0.05) in the absence of a significant change in LC3-I levels (Fig. 2 E). Furthermore, LC3 immunoreactivity, which was present predominantly in neuronal cell bodies in NTg mice (Fig. 2, F and I), was distributed to both hippocampal cell bodies and dendrites in 9-mo- (Fig. 2, G and H) and 9-wk-old (Fig. 2, J and K) PS1/APP mice. The staining pattern for LC3 in many dendrites was more frequently punctate in PS1/APP than in NTg mice (Fig. 2, I and J), although less so than in older PS1/APP mice (Fig. 2, compare H with K). Collectively, these observations demonstrate that macroautophagy is induced at a prepathological stage of disease in PS1/APP mice and that, in addition, different subtypes of AVs accumulate pathologically as neuritic dystrophy develops in older mice, as in AD.

Bottom Line: Purified AVs contain APP and beta-cleaved APP and are highly enriched in PS1, nicastrin, and PS-dependent gamma-secretase activity.Inducing or inhibiting macroautophagy in neuronal and nonneuronal cells by modulating mammalian target of rapamycin kinase elicits parallel changes in AV proliferation and Abeta production.Our results, therefore, link beta-amyloidogenic and cell survival pathways through macroautophagy, which is activated and is abnormal in AD.

View Article: PubMed Central - PubMed

Affiliation: Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY 10962, USA.

ABSTRACT
Macroautophagy, which is a lysosomal pathway for the turnover of organelles and long-lived proteins, is a key determinant of cell survival and longevity. In this study, we show that neuronal macroautophagy is induced early in Alzheimer's disease (AD) and before beta-amyloid (Abeta) deposits extracellularly in the presenilin (PS) 1/Abeta precursor protein (APP) mouse model of beta-amyloidosis. Subsequently, autophagosomes and late autophagic vacuoles (AVs) accumulate markedly in dystrophic dendrites, implying an impaired maturation of AVs to lysosomes. Immunolabeling identifies AVs in the brain as a major reservoir of intracellular Abeta. Purified AVs contain APP and beta-cleaved APP and are highly enriched in PS1, nicastrin, and PS-dependent gamma-secretase activity. Inducing or inhibiting macroautophagy in neuronal and nonneuronal cells by modulating mammalian target of rapamycin kinase elicits parallel changes in AV proliferation and Abeta production. Our results, therefore, link beta-amyloidogenic and cell survival pathways through macroautophagy, which is activated and is abnormal in AD.

Show MeSH
Related in: MedlinePlus