Autophagy Induction and Autophagosome Clearance in Neurons: Relationship to Autophagic Pathology in Alzheimer's Disease
Top Cited Papers
- 2 July 2008
- journal article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 28 (27), 6926-6937
- https://doi.org/10.1523/jneurosci.0800-08.2008
Abstract
Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the neurodegeneration of Alzheimer's disease (AD). The basis for the profuse accumulation of autophagic vacuoles (AVs) in affected neurons of the AD brain, however, is unknown. In this study, we show that constitutive macroautophagy in primary cortical neurons is highly efficient, because newly formed autophagosomes are rapidly cleared by fusion with lysosomes, accounting for their scarcity in the healthy brain. Even after macroautophagy is strongly induced by suppressing mTOR (mammalian target of rapamycin) kinase activity with rapamycin or nutrient deprivation, active cathepsin-positive autolysosomes rather than LC3-II-positive autophagosomes predominate, implying efficient autophagosome clearance in healthy neurons. In contrast, selectively impeding late steps in macroautophagy by inhibiting cathepsin-mediated proteolysis within autolysosomes with cysteine- and aspartyl-protease inhibitors caused a marked accumulation of electron-dense double-membrane-limited AVs, containing cathepsin D and incompletely degraded LC3-II in perikarya and neurites. Similar structures accumulated in large numbers when fusion of autophagosomes with lysosomes was slowed by disrupting their transport on microtubules with vinblastine. Finally, we find that the autophagic vacuoles accumulating after protease inhibition or prolonged vinblastine treatment strongly resembled AVs that collect in dystrophic neurites in the AD brain and in an AD mouse model. We conclude that macroautophagy is constitutively active and highly efficient in healthy neurons and that the autophagic pathology observed in AD most likely arises from impaired clearance of AVs rather than strong autophagy induction alone. Therapeutic modulation of autophagy in AD may, therefore, require targeting late steps in the autophagic pathway.Keywords
This publication has 55 references indexed in Scilit:
- Small molecules enhance autophagy and reduce toxicity in Huntington's disease modelsNature Chemical Biology, 2007
- Regulation of Autophagy by Extracellular Signal-Regulated Protein Kinases During 1-Methyl-4-Phenylpyridinium-Induced Cell DeathThe American Journal of Pathology, 2007
- Autophagy in neurodegenerative disease: friend, foe or turncoat?Trends in Neurosciences, 2006
- Proteolytic and lipolytic responses to starvationNutrition, 2006
- Autophagic Stress in Neuronal Injury and DiseaseJournal of Neuropathology and Experimental Neurology, 2006
- Suppression of basal autophagy in neural cells causes neurodegenerative disease in miceNature, 2006
- Loss of autophagy in the central nervous system causes neurodegeneration in miceNature, 2006
- Cell-Autonomous Death of Cerebellar Purkinje Neurons with Autophagy in Niemann-Pick Type C DiseasePLoS Genetics, 2005
- Correction: Uncoupling of Longevity and Telomere Length in C. elegansPLoS Genetics, 2005
- Prelysosomal convergence of autophagic and endocytic pathwaysBiochemical and Biophysical Research Communications, 1988