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ABSTRACT In metazoans, autophagosomes fuse with late endosomes (LEs)/multivesicular bodies (MVBs) to form a hybrid organelle known as an amphisome. Subsequently upon fusion with lysosomes the contents of amphisomes are degraded. While the formation of metazoan amphisomes has been well established, it has remained an open question whether amphisomes form and deliver their cargo to the central vacuole for degradation in plant cells. In this mini review, we provide an update on recent discoveries in the field of plant autophagy that demonstrate the formation of amphisome-like organelles that are generated through several distinct autophagosome/MVB fusion pathways.
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Spatiotemporal analysis of axonal autophagosome–lysosome dynamics reveals limited fusion events and slow maturation
Macroautophagy is a homeostatic process required to clear cellular waste. Neuronal autophagosomes form constitutively in the distal tip of the axon and are actively transported toward the soma, with cargo degradation initiated en route. Cargo turnover requires autophagosomes to fuse with lysosomes to acquire degradative enzymes; however, directly imaging these fusion events in the axon is impractical. Here we use a quantitative model, parameterized and validated using data from primary hippocampal neurons, to explore the autophagosome maturation process. We demonstrate that retrograde autophagosome motility is independent of fusion and that most autophagosomes fuse with only a few lysosomes during axonal transport. Our results indicate that breakdown of the inner autophagosomal membrane is much slower in neurons than in nonneuronal cell types, highlighting the importance of this late maturation step. Together, rigorous quantitative measurements and mathematical modeling elucidate the dynamics of autophagosome–lysosome interaction and autophagosomal maturation in the axon.
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- Award ID(s):
- 1848057
- PAR ID:
- 10424408
- Editor(s):
- Edelstein-Keshet, Leah
- Date Published:
- Journal Name:
- Molecular Biology of the Cell
- Volume:
- 33
- Issue:
- 13
- ISSN:
- 1059-1524
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1091/mbc.E22-03-0111
