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Fission of tubular endosomes triggers endosomal acidification and movement.

Mesaki K, Tanabe K, Obayashi M, Oe N, Takei K - PLoS ONE (2011)

Bottom Line: It is currently unknown how sorting and the processes of maturation cooperate with each other.These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome.We believe this to be the first evidence of a cascade from sorting to degradation.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.

ABSTRACT
The early endosome acts as a sorting station for internalized molecules destined for recycling or degradation. While recycled molecules are sorted and delivered to tubular endosomes, residual compartments containing molecules to be degraded undergo "maturation" before final degradation in the lysosome. This maturation involves acidification, microtubule-dependent motility, and perinuclear localization. It is currently unknown how sorting and the processes of maturation cooperate with each other. Here, we show that fission of a tubular endosome triggers the maturation of the residual endosome, leading to degradation. Use of the dynamin inhibitor dynasore to block tubular endosome fission inhibited acidification, endosomal motility along microtubules, perinuclear localization, and degradation. However, tubular endosome fission was not affected by inhibiting endosomal acidification or by depolymerizing the microtubules. These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome. We believe this to be the first evidence of a cascade from sorting to degradation.

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Dynasore inhibits tubule fission and endosomal motility.HeLa cells were bound on ice with Alexa555-EGF and Alexa488-transferrin, rinsed, and transferred to 37°C. After 5 min, dynasore was added, and the cells were incubated further for another 25 min. For washout, the cells were rinsed at 30 min with dynasore-free media. Live images were taken just before washout (A) and at 10 min after washout (B). Frames were captured every 2 sec for a total of 2 min 30 s (See also Movie S3). C, Movements of EGF-positive endosomes for 90 s were manually tracked and are illustrated. D, The mean total movement distance of EGF-positive endosomes for 2 min. 20 endosomes were measured from 4 cells; Error bar, S.D.
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pone-0019764-g003: Dynasore inhibits tubule fission and endosomal motility.HeLa cells were bound on ice with Alexa555-EGF and Alexa488-transferrin, rinsed, and transferred to 37°C. After 5 min, dynasore was added, and the cells were incubated further for another 25 min. For washout, the cells were rinsed at 30 min with dynasore-free media. Live images were taken just before washout (A) and at 10 min after washout (B). Frames were captured every 2 sec for a total of 2 min 30 s (See also Movie S3). C, Movements of EGF-positive endosomes for 90 s were manually tracked and are illustrated. D, The mean total movement distance of EGF-positive endosomes for 2 min. 20 endosomes were measured from 4 cells; Error bar, S.D.

Mentions: To validate our hypothesis that tubule fission was inhibited by dynasore, we performed live-cell imaging. In control cells, transferrin-containing tubules pinched off at the root and separated from the EGF-positive vacuolar part. As expected, when cells were treated with dynasore, transferrin tubules formed but fission was not observed (Fig. 3A and Movie S3). When dynasore was washed out, fission events were restarted and tubular transport of transferrin was observed (Fig. 3B and Movie S4). From these results, we concluded that dynasore inhibited tubule fission from the early endosome and resulted in inhibition of recycling.


Fission of tubular endosomes triggers endosomal acidification and movement.

Mesaki K, Tanabe K, Obayashi M, Oe N, Takei K - PLoS ONE (2011)

Dynasore inhibits tubule fission and endosomal motility.HeLa cells were bound on ice with Alexa555-EGF and Alexa488-transferrin, rinsed, and transferred to 37°C. After 5 min, dynasore was added, and the cells were incubated further for another 25 min. For washout, the cells were rinsed at 30 min with dynasore-free media. Live images were taken just before washout (A) and at 10 min after washout (B). Frames were captured every 2 sec for a total of 2 min 30 s (See also Movie S3). C, Movements of EGF-positive endosomes for 90 s were manually tracked and are illustrated. D, The mean total movement distance of EGF-positive endosomes for 2 min. 20 endosomes were measured from 4 cells; Error bar, S.D.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3091875&req=5

pone-0019764-g003: Dynasore inhibits tubule fission and endosomal motility.HeLa cells were bound on ice with Alexa555-EGF and Alexa488-transferrin, rinsed, and transferred to 37°C. After 5 min, dynasore was added, and the cells were incubated further for another 25 min. For washout, the cells were rinsed at 30 min with dynasore-free media. Live images were taken just before washout (A) and at 10 min after washout (B). Frames were captured every 2 sec for a total of 2 min 30 s (See also Movie S3). C, Movements of EGF-positive endosomes for 90 s were manually tracked and are illustrated. D, The mean total movement distance of EGF-positive endosomes for 2 min. 20 endosomes were measured from 4 cells; Error bar, S.D.
Mentions: To validate our hypothesis that tubule fission was inhibited by dynasore, we performed live-cell imaging. In control cells, transferrin-containing tubules pinched off at the root and separated from the EGF-positive vacuolar part. As expected, when cells were treated with dynasore, transferrin tubules formed but fission was not observed (Fig. 3A and Movie S3). When dynasore was washed out, fission events were restarted and tubular transport of transferrin was observed (Fig. 3B and Movie S4). From these results, we concluded that dynasore inhibited tubule fission from the early endosome and resulted in inhibition of recycling.

Bottom Line: It is currently unknown how sorting and the processes of maturation cooperate with each other.These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome.We believe this to be the first evidence of a cascade from sorting to degradation.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.

ABSTRACT
The early endosome acts as a sorting station for internalized molecules destined for recycling or degradation. While recycled molecules are sorted and delivered to tubular endosomes, residual compartments containing molecules to be degraded undergo "maturation" before final degradation in the lysosome. This maturation involves acidification, microtubule-dependent motility, and perinuclear localization. It is currently unknown how sorting and the processes of maturation cooperate with each other. Here, we show that fission of a tubular endosome triggers the maturation of the residual endosome, leading to degradation. Use of the dynamin inhibitor dynasore to block tubular endosome fission inhibited acidification, endosomal motility along microtubules, perinuclear localization, and degradation. However, tubular endosome fission was not affected by inhibiting endosomal acidification or by depolymerizing the microtubules. These results demonstrate that the fission of recycling tubules is the first important step in endosomal maturation and degradation in the lysosome. We believe this to be the first evidence of a cascade from sorting to degradation.

Show MeSH
Related in: MedlinePlus