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Abeta42-induced neurodegeneration via an age-dependent autophagic-lysosomal injury in Drosophila.

Ling D, Song HJ, Garza D, Neufeld TP, Salvaterra PM - PLoS ONE (2009)

Bottom Line: Abeta(1-42)-induced impairment of the degradative function, as well as the structural integrity, of post-lysosomal autophagic vesicles triggers a neurodegenerative cascade that can be enhanced by autophagy activation or partially rescued by autophagy inhibition.Neuronal autophagy initially appears to play a pro-survival role that changes in an age-dependent way to a pro-death role in the context of Abeta(1-42) expression.Our in vivo observations provide a mechanistic understanding for the differential neurotoxicity of Abeta(1-42) and Abeta(1-40), and reveal an Abeta(1-42)-induced death execution pathway mediated by an age-dependent autophagic-lysosomal injury.

View Article: PubMed Central - PubMed

Affiliation: Division of Neuroscience, Beckman Research Institute of the City of Hope, Duarte, California, United States of America.

ABSTRACT
The mechanism of widespread neuronal death occurring in Alzheimer's disease (AD) remains enigmatic even after extensive investigation during the last two decades. Amyloid beta 42 peptide (Abeta(1-42)) is believed to play a causative role in the development of AD. Here we expressed human Abeta(1-42) and amyloid beta 40 (Abeta(1-40)) in Drosophila neurons. Abeta(1-42) but not Abeta(1-40) causes an extensive accumulation of autophagic vesicles that become increasingly dysfunctional with age. Abeta(1-42)-induced impairment of the degradative function, as well as the structural integrity, of post-lysosomal autophagic vesicles triggers a neurodegenerative cascade that can be enhanced by autophagy activation or partially rescued by autophagy inhibition. Compromise and leakage from post-lysosomal vesicles result in cytosolic acidification, additional damage to membranes and organelles, and erosive destruction of cytoplasm leading to eventual neuron death. Neuronal autophagy initially appears to play a pro-survival role that changes in an age-dependent way to a pro-death role in the context of Abeta(1-42) expression. Our in vivo observations provide a mechanistic understanding for the differential neurotoxicity of Abeta(1-42) and Abeta(1-40), and reveal an Abeta(1-42)-induced death execution pathway mediated by an age-dependent autophagic-lysosomal injury.

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Dysfunctional autophagic vesicles are at a post-lysosomal fusion stage.(A) Many GFP puncta in Aβ1–42-targeted neurons are stained by acidophilic LysoTracker Red (left panel, white arrows) while some are not (blue arrows). A high magnification view of an affected neuron (square area) shows a nearly complete colocalization of GFP puncta with LysoTracker Red staining (right two panels) suggesting that many GFP puncta are post-lysosomal vesicles. (B) Cytosolic YFP expression shows Aβ1–42-induced puncta (left panel, arrows) that colocalize with punctate LAMP1-GFP (middle panel, arrows), suggesting that they are post-lysosomal vesicles. Scale bars = 5 µm.
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pone-0004201-g004: Dysfunctional autophagic vesicles are at a post-lysosomal fusion stage.(A) Many GFP puncta in Aβ1–42-targeted neurons are stained by acidophilic LysoTracker Red (left panel, white arrows) while some are not (blue arrows). A high magnification view of an affected neuron (square area) shows a nearly complete colocalization of GFP puncta with LysoTracker Red staining (right two panels) suggesting that many GFP puncta are post-lysosomal vesicles. (B) Cytosolic YFP expression shows Aβ1–42-induced puncta (left panel, arrows) that colocalize with punctate LAMP1-GFP (middle panel, arrows), suggesting that they are post-lysosomal vesicles. Scale bars = 5 µm.

Mentions: Newly formed autophagosomes are known to fuse with lysosome-related vesicles such as autophagic vacuoles, endosomes or lysosomes to acquire catabolic enzymes necessary for their degradative function[6]. To test if Aβ1–42-induced puncta are autophagosomes that have failed in vesicle fusion, we stained fly brains with LysoTracker Red, an acidophilic chemical that marks lysosomes or other lysosome-related vesicles[26], [27]. Many of the puncta are positively stained by LysoTracker Red (Fig. 4A), suggesting that many, but not all, of the accumulated puncta are post-lysosomal autophagic vesicles. Additionally, we co-expressed a cytosolic YFP reporter along with a chimeric protein, lysosome-associated membrane protein 1 (LAMP1) fused to GFP, in Aβ1–42-targeted neurons. There is an extensive colocalization of Aβ1–42-induced YFP puncta with LAMP1-GFP (Fig. 4B), suggesting that many dysfunctional autophagic vesicles have fused with lysosomes. Some enlarged autophagic vesicles apparently derived from fusion of several smaller vesicles in neurons from Aβ1–42 fly brains (double arrowheads in Figs. 2B and S2) further suggest that the vesicle fusion process is not blocked.


Abeta42-induced neurodegeneration via an age-dependent autophagic-lysosomal injury in Drosophila.

Ling D, Song HJ, Garza D, Neufeld TP, Salvaterra PM - PLoS ONE (2009)

Dysfunctional autophagic vesicles are at a post-lysosomal fusion stage.(A) Many GFP puncta in Aβ1–42-targeted neurons are stained by acidophilic LysoTracker Red (left panel, white arrows) while some are not (blue arrows). A high magnification view of an affected neuron (square area) shows a nearly complete colocalization of GFP puncta with LysoTracker Red staining (right two panels) suggesting that many GFP puncta are post-lysosomal vesicles. (B) Cytosolic YFP expression shows Aβ1–42-induced puncta (left panel, arrows) that colocalize with punctate LAMP1-GFP (middle panel, arrows), suggesting that they are post-lysosomal vesicles. Scale bars = 5 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2626277&req=5

pone-0004201-g004: Dysfunctional autophagic vesicles are at a post-lysosomal fusion stage.(A) Many GFP puncta in Aβ1–42-targeted neurons are stained by acidophilic LysoTracker Red (left panel, white arrows) while some are not (blue arrows). A high magnification view of an affected neuron (square area) shows a nearly complete colocalization of GFP puncta with LysoTracker Red staining (right two panels) suggesting that many GFP puncta are post-lysosomal vesicles. (B) Cytosolic YFP expression shows Aβ1–42-induced puncta (left panel, arrows) that colocalize with punctate LAMP1-GFP (middle panel, arrows), suggesting that they are post-lysosomal vesicles. Scale bars = 5 µm.
Mentions: Newly formed autophagosomes are known to fuse with lysosome-related vesicles such as autophagic vacuoles, endosomes or lysosomes to acquire catabolic enzymes necessary for their degradative function[6]. To test if Aβ1–42-induced puncta are autophagosomes that have failed in vesicle fusion, we stained fly brains with LysoTracker Red, an acidophilic chemical that marks lysosomes or other lysosome-related vesicles[26], [27]. Many of the puncta are positively stained by LysoTracker Red (Fig. 4A), suggesting that many, but not all, of the accumulated puncta are post-lysosomal autophagic vesicles. Additionally, we co-expressed a cytosolic YFP reporter along with a chimeric protein, lysosome-associated membrane protein 1 (LAMP1) fused to GFP, in Aβ1–42-targeted neurons. There is an extensive colocalization of Aβ1–42-induced YFP puncta with LAMP1-GFP (Fig. 4B), suggesting that many dysfunctional autophagic vesicles have fused with lysosomes. Some enlarged autophagic vesicles apparently derived from fusion of several smaller vesicles in neurons from Aβ1–42 fly brains (double arrowheads in Figs. 2B and S2) further suggest that the vesicle fusion process is not blocked.

Bottom Line: Abeta(1-42)-induced impairment of the degradative function, as well as the structural integrity, of post-lysosomal autophagic vesicles triggers a neurodegenerative cascade that can be enhanced by autophagy activation or partially rescued by autophagy inhibition.Neuronal autophagy initially appears to play a pro-survival role that changes in an age-dependent way to a pro-death role in the context of Abeta(1-42) expression.Our in vivo observations provide a mechanistic understanding for the differential neurotoxicity of Abeta(1-42) and Abeta(1-40), and reveal an Abeta(1-42)-induced death execution pathway mediated by an age-dependent autophagic-lysosomal injury.

View Article: PubMed Central - PubMed

Affiliation: Division of Neuroscience, Beckman Research Institute of the City of Hope, Duarte, California, United States of America.

ABSTRACT
The mechanism of widespread neuronal death occurring in Alzheimer's disease (AD) remains enigmatic even after extensive investigation during the last two decades. Amyloid beta 42 peptide (Abeta(1-42)) is believed to play a causative role in the development of AD. Here we expressed human Abeta(1-42) and amyloid beta 40 (Abeta(1-40)) in Drosophila neurons. Abeta(1-42) but not Abeta(1-40) causes an extensive accumulation of autophagic vesicles that become increasingly dysfunctional with age. Abeta(1-42)-induced impairment of the degradative function, as well as the structural integrity, of post-lysosomal autophagic vesicles triggers a neurodegenerative cascade that can be enhanced by autophagy activation or partially rescued by autophagy inhibition. Compromise and leakage from post-lysosomal vesicles result in cytosolic acidification, additional damage to membranes and organelles, and erosive destruction of cytoplasm leading to eventual neuron death. Neuronal autophagy initially appears to play a pro-survival role that changes in an age-dependent way to a pro-death role in the context of Abeta(1-42) expression. Our in vivo observations provide a mechanistic understanding for the differential neurotoxicity of Abeta(1-42) and Abeta(1-40), and reveal an Abeta(1-42)-induced death execution pathway mediated by an age-dependent autophagic-lysosomal injury.

Show MeSH
Related in: MedlinePlus