skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: 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.  more » « less
Award ID(s):
1848057
PAR ID:
10424408
Author(s) / Creator(s):
; ; ;
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
More Like this
  1. ; ; ; ; ; (, Cells)
    null (Ed.)
    In eukaryotic cells, autophagosomes and multivesicular bodies (MVBs) are two closely related partners in the lysosomal/vacuolar protein degradation system. Autophagosomes are double membrane-bound organelles that transport cytoplasmic components, including proteins and organelles for autophagic degradation in the lysosomes/vacuoles. MVBs are single-membrane organelles in the endocytic pathway that contain intraluminal vesicles whose content is either degraded in the lysosomes/vacuoles or recycled to the cell surface. In plants, both autophagosome and MVB pathways play important roles in plant responses to biotic and abiotic stresses. More recent studies have revealed that autophagosomes and MVBs also act together in plant stress responses in a variety of processes, including deployment of defense-related molecules, regulation of cell death, trafficking and degradation of membrane and soluble constituents, and modulation of plant hormone metabolism and signaling. In this review, we discuss these recent findings on the coordination and crosstalk between autophagosome and MVB pathways that contribute to the complex network of plant stress responses. 
    more » « less
  2. ; ; (, Frontiers in Chemical Engineering)
    GM1 gangliosidosis is a lysosomal storage disorder caused by deficiency of β-galactosidase (βgal) and subsequent accumulation of GM1 ganglioside in lysosomes. One of the pathological aspects of GM1 gangliosidosis, and other storage disorders, is impaired autophagy, i.e., a reduced fusion of autophagosomes and lysosomes to degrade cellular waste. Enzyme replacement therapy (ERT) can effectively treat systemic deficiency but is limited by immunogenicity and shortened half-life of intravenously administered enzyme. In this paper, we report a hyaluronic acid-b-polylactic acid (HA-PLA) polymersome delivery system that can achieve an enzyme-responsive and sustained delivery of βgal to promote the cell’s self-healing process of autophagy. HA-PLA polymersomes have an average diameter of 138.0 ± 17.6 nm and encapsulate βgal with an efficiency of 77.7 ± 3.4%. In the presence of model enzyme Hyaluronidase, HA-PLA polymersomes demonstrate a two-fold higher release of encapsulant than without enzyme. We also identified reduced autophagy in a cellular model of GM1 Gangliosidosis (GM1SV3) compared to healthy cells, illustrated using immunofluorescence. Enhanced autophagy was reported in GM1SV3 cells treated with βgal-loaded polymersomes. Most notably, the fusion of lysosomes and autophagosomes in GM1SV3 cells returned to normal levels of healthy cells after 24 h of polymersome treatment. The HA-PLA polymersomes described here can provide a promising delivery system to treat GM1 Gangliosidosis. 
    more » « less
  3. ; ; ; (, Communications Biology)
    Abstract Immune cells degrade internalized pathogens in phagosomes through sequential biochemical changes. The degradation must be fast enough for effective infection control. The presumption is that each phagosome degrades cargos autonomously with a distinct but stochastic kinetic rate. However, here we show that the degradation kinetics of individual phagosomes is not stochastic but coupled to their intracellular motility. By engineering RotSensors that are optically anisotropic, magnetic responsive, and fluorogenic in response to degradation activities in phagosomes, we monitored cargo degradation kinetics in single phagosomes simultaneously with their translational and rotational dynamics. We show that phagosomes that move faster centripetally are more likely to encounter and fuse with lysosomes, thereby acidifying faster and degrading cargos more efficiently. The degradation rates increase nearly linearly with the translational and rotational velocities of phagosomes. Our results indicate that the centripetal motion of phagosomes functions as a clock for controlling the progression of cargo degradation. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, bioRxiv)
    Autophagosomes and lysosomes work in tandem to conduct autophagy, an intracellular degradation system which is crucial for cellular homeostasis. Altered autophagy contributes to the pathophysiology of various diseases, including cancers and metabolic diseases. Although many studies have investigated autophagy to elucidate disease pathogenesis, specific identification of the various components of the cellular degradation machinery remains difficult. The goal of this paper is to describe an approach to reproducibly identify and distinguish subcellular structures involved in autophagy. We provide methods that avoid common pitfalls, including a detailed explanation for how to distinguish lysosomes and lipid droplets and discuss the differences between autophagosomes and inclusion bodies. These methods are based on using transmission electron microscopy (TEM), capable of generating nanometer-scale micrographs of cellular degradation components in a fixed sample. In addition to TEM, we discuss other imaging techniques, such as immunofluorescence and immunogold labeling, which can be utilized for the reliable and accurate classification of cellular organelles. Our results show how these methods may be employed to accurately quantify the cellular degradation machinery under various conditions, such as treatment with the endoplasmic reticulum stressor thapsigargin or the ablation of dynamin-related protein 1. 
    more » « less
  5. ; ; ; ; ; ; ; (, Developmental Neurobiology)
    Abstract Serotonergic neurons produce extensively branched axons that fill most of the central nervous system, where they modulate a wide variety of behaviors. Many behavioral disorders have been correlated with defective serotonergic axon morphologies. Proper behavioral output therefore depends on the precise outgrowth and targeting of serotonergic axons during development. To direct outgrowth, serotonergic neurons utilize serotonin as a signaling molecule prior to it assuming its neurotransmitter role. This process, termed serotonin autoregulation, regulates axon outgrowth, branching, and varicosity development of serotonergic neurons. However, the receptor that mediates serotonin autoregulation is unknown. Here we asked if serotonin receptor 5‐HT1A plays a role in serotonergic axon outgrowth and branching. Using culturedDrosophilaserotonergic neurons, we found that exogenous serotonin reduced axon length and branching only in those expressing 5‐HT1A. Pharmacological activation of 5‐HT1A led to reduced axon length and branching, whereas the disruption of 5‐HT1A rescued outgrowth in the presence of exogenous serotonin. Altogether this suggests that 5‐HT1A is a serotonin autoreceptor in a subpopulation of serotonergic neurons and initiates signaling pathways that regulate axon outgrowth and branching duringDrosophiladevelopment. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email