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Ubiquitin traffic signals

Addition of a K63-linked chain of ubiquitins drives Gap1 permease (green) to the vacuole (red) via MVBs in yeast cells.

Lauwers et al. have discovered how certain yeast membrane proteins end up in a cellular trash can.

The vacuole of yeast, like the lysosome of mammalian cells, is a disposal system for unwanted cellular components. According to Lauwers et al., two yeast proteins—one a disposer that resides in the vacuole, the other a disposee—are routed to this destructive organelle after being tagged with a special chain of ubiquitin molecules.

The addition of ubiquitin molecules—ubiquitylation—controls the function and cellular localization of a wide variety of proteins. This diversity seems to depend on the many different forms that ubiquitylation can take. For example, addition of a string of ubiquitins called a K48-linked chain is well known for sending proteins to another type of cellular trash can called the proteasome.

Lauwers et al. showed that addition of a single ubiquitin molecule to a plasma membrane protein called Gap1 permease prompted the protein's endocytosis. Addition of a K63-linked chain of ubiquitins, however, sent Gap1 to its destruction in the vacuole—via intermediate membrane compartments called multivesicular bodies (MVBs). K63-linked ubiquitylation also prompted MVB sorting of a second protein, carboxypeptidase S, to the vacuolar lumen—this particular protein's workplace.

K63-linked modification has been reported for a number of mammalian proteins destined for the lysosome, indicating that this signal and the pathway that recognizes it are conserved.

References

Lauwers, E., et al. 2009. J. Cell Biol. doi:10.1083/jcb.200810114.[Abstract/Free Full Text]

ruth.williams{at}rockefeller.edu

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K63-linked ubiquitin chains as a specific signal for protein sorting into the multivesicular body pathway

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J. Cell Biol. 2009 185: 493-502. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 504K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Williams, R. Search for Related Content PubMed Articles by Williams, R. Related Collections Related Article Social Bookmarking                            What's this?