| Title: |
Ubiquitin initiates sorting of Golgi and plasma membrane proteins into the vacuolar degradation pathway |
| Authors: |
Scheuring, David; Künzl, Fabian; Viotti, Corrado; Yan, Melody San Wan; Jiang, Liwen; Schellmann, Swen; Robinson, David G; Pimpl, Peter |
| Publisher Information: |
BioMed Central Ltd. |
| Publication Year: |
2012 |
| Collection: |
BioMed Central |
| Description: |
Background In yeast and mammals, many plasma membrane (PM) proteins destined for degradation are tagged with ubiquitin. These ubiquitinated proteins are internalized into clathrin-coated vesicles and are transported to early endosomal compartments. There, ubiquitinated proteins are sorted by the endosomal sorting complex required for transport (ESCRT) machinery into the intraluminal vesicles of multivesicular endosomes. Degradation of these proteins occurs after endosomes fuse with lysosomes/lytic vacuoles to release their content into the lumen. In plants, some PM proteins, which cycle between the PM and endosomal compartments, have been found to be ubiquitinated, but it is unclear whether ubiquitin is sufficient to mediate internalization and thus acts as a primary sorting signal for the endocytic pathway. To test whether plants use ubiquitin as a signal for the degradation of membrane proteins, we have translationally fused ubiquitin to different fluorescent reporters for the plasma membrane and analyzed their transport. Results Ubiquitin-tagged PM reporters localized to endosomes and to the lumen of the lytic vacuole in tobacco mesophyll protoplasts and in tobacco epidermal cells. The internalization of these reporters was significantly reduced if clathrin-mediated endocytosis was inhibited by the coexpression of a mutant of the clathrin heavy chain, the clathrin hub. Surprisingly, a ubiquitin-tagged reporter for the Golgi was also transported into the lumen of the vacuole. Vacuolar delivery of the reporters was abolished upon inhibition of the ESCRT machinery, indicating that the vacuolar delivery of these reporters occurs via the endocytic transport route. Conclusions Ubiquitin acts as a sorting signal at different compartments in the endomembrane system to target membrane proteins into the vacuolar degradation pathway: If displayed at the PM, ubiquitin triggers internalization of PM reporters into the endocytic transport route, but it also mediates vacuolar delivery if displayed at the Golgi. In ... |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| Relation: |
http://www.biomedcentral.com/1471-2229/12/164 |
| Availability: |
http://www.biomedcentral.com/1471-2229/12/164 |
| Rights: |
Copyright 2012 Scheuring et al.; licensee BioMed Central Ltd. |
| Accession Number: |
edsbas.C3DC24B1 |
| Database: |
BASE |