scholarly journals Integrated control of transporter endocytosis and recycling by the arrestin-related protein Rod1 and the ubiquitin ligase Rsp5

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Michel Becuwe ◽  
Sébastien Léon
Keyword(s):  
Ubiquitin Ligase ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Integrated Control ◽  
Monocarboxylate Transporter ◽  
Related Protein ◽  
Endocytic Sorting ◽  
Lysosomal Targeting ◽  
Golgi Network ◽  
External Signals

After endocytosis, membrane proteins can recycle to the cell membrane or be degraded in lysosomes. Cargo ubiquitylation favors their lysosomal targeting and can be regulated by external signals, but the mechanism is ill-defined. Here, we studied the post-endocytic trafficking of Jen1, a yeast monocarboxylate transporter, using microfluidics-assisted live-cell imaging. We show that the ubiquitin ligase Rsp5 and the glucose-regulated arrestin-related trafficking adaptors (ART) protein Rod1, involved in the glucose-induced internalization of Jen1, are also required for the post-endocytic sorting of Jen1 to the yeast lysosome. This new step takes place at the trans-Golgi network (TGN), where Rod1 localizes dynamically upon triggering endocytosis. Indeed, transporter trafficking to the TGN after internalization is required for their degradation. Glucose removal promotes Rod1 relocalization to the cytosol and Jen1 deubiquitylation, allowing transporter recycling when the signal is only transient. Therefore, nutrient availability regulates transporter fate through the localization of the ART/Rsp5 ubiquitylation complex at the TGN.

scholarly journals The yeast arrestin-related protein Bul1 is a novel actor of glucose-induced endocytosis

2018 ◽  
Vol 29 (9) ◽  
pp. 1012-1020 ◽  
Author(s):  
Junie Hovsepian ◽  
Véronique Albanèse ◽  
Michel Becuwe ◽  
Vasyl Ivashov ◽  
David Teis ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Endocytic Pathway ◽  
Yeast Cells ◽  
Monocarboxylate Transporter ◽  
Related Protein ◽  
Related Family ◽  
Nutrient Signaling ◽  
Mechanistic Basis ◽  
A Current ◽  
Glucose Availability

Yeast cells have a remarkable ability to adapt to nutritional changes in their environment. During adaptation, nutrient-signaling pathways drive the selective endocytosis of nutrient transporters present at the cell surface. A current challenge is to understand the mechanistic basis of this regulation. Transporter endocytosis is triggered by their ubiquitylation, which involves the ubiquitin ligase Rsp5 and its adaptors of the arrestin-related family (ART). This step is highly regulated by nutrient availability. For instance, the monocarboxylate transporter Jen1 is ubiquitylated, endocytosed, and degraded upon exposure to glucose. The ART protein Rod1 is required for this overall process; yet Rod1 rather controls Jen1 trafficking later in the endocytic pathway and is almost dispensable for Jen1 internalization. Thus, how glucose triggers Jen1 internalization remains unclear. We report that another ART named Bul1, but not its paralogue Bul2, contributes to Jen1 internalization. Bul1 responds to glucose availability, and preferentially acts at the plasma membrane for Jen1 internalization. Thus, multiple ARTs can act sequentially along the endocytic pathway to control transporter homeostasis. Moreover, Bul1 is in charge of Jen1 endocytosis after cycloheximide treatment, suggesting that the functional redundancy of ARTs may be explained by their ability to interact with multiple cargoes in various conditions.

scholarly journals Sphingomyelin is sorted at the trans Golgi network into a distinct class of secretory vesicle

2016 ◽  
Vol 113 (24) ◽  
pp. 6677-6682 ◽  
Author(s):  
Yongqiang Deng ◽  
Felix E. Rivera-Molina ◽  
Derek K. Toomre ◽  
Christopher G. Burd
Keyword(s):  
Plasma Membrane ◽  
Intracellular Trafficking ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Secretory Vesicle ◽  
Secretory Protein ◽  
Secretory Vesicles ◽  
Distinct Class ◽  
Equinatoxin Ii ◽  
Golgi Network

One of the principal functions of the trans Golgi network (TGN) is the sorting of proteins into distinct vesicular transport carriers that mediate secretion and interorganelle trafficking. Are lipids also sorted into distinct TGN-derived carriers? The Golgi is the principal site of the synthesis of sphingomyelin (SM), an abundant sphingolipid that is transported. To address the specificity of SM transport to the plasma membrane, we engineered a natural SM-binding pore-forming toxin, equinatoxin II (Eqt), into a nontoxic reporter termed Eqt-SM and used it to monitor intracellular trafficking of SM. Using quantitative live cell imaging, we found that Eqt-SM is enriched in a subset of TGN-derived secretory vesicles that are also enriched in a glycophosphatidylinositol-anchored protein. In contrast, an integral membrane secretory protein (CD8α) is not enriched in these carriers. Our results demonstrate the sorting of native SM at the TGN and its transport to the plasma membrane by specific carriers.

scholarly journals Biochemical and structural analysis of α-catenin in cell–cell contacts

2008 ◽  
Vol 36 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Sabine Pokutta ◽  
Frauke Drees ◽  
Soichiro Yamada ◽  
W. James Nelson ◽  
William I. Weis
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Adherens Junction ◽  
Structural Data ◽  
Cell Contact ◽  
Related Protein ◽  
Imaging Studies ◽  
Actin Networks ◽  
Junction Formation ◽  
Cell Cell

Cadherins are transmembrane adhesion molecules that mediate homotypic cell–cell contact. In adherens junctions, the cytoplasmic domain of cadherins is functionally linked to the actin cytoskeleton through a series of proteins known as catenins. E-cadherin binds to β-catenin, which in turn binds to α-catenin to form a ternary complex. α-Catenin also binds to actin, and it was assumed previously that α-catenin links the cadherin–catenin complex to actin. However, biochemical, structural and live-cell imaging studies of the cadherin–catenin complex and its interaction with actin show that binding of β-catenin to α-catenin prevents the latter from binding to actin. Biochemical and structural data indicate that α-catenin acts as an allosteric protein whose conformation and activity changes depending on whether or not it is bound to β-catenin. Initial contacts between cells occur on dynamic lamellipodia formed by polymerization of branched actin networks, a process controlled by the Arp2/3 (actin-related protein 2/3) complex. α-Catenin can suppress the activity of Arp2/3 by competing for actin filaments. These findings lead to a model for adherens junction formation in which clustering of the cadherin–β-catenin complex recruits high levels of α-catenin that can suppress the Arp2/3 complex, leading to cessation of lamellipodial movement and formation of a stable contact. Thus α-catenin appears to play a central role in cell–cell contact formation.

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