Breaking news on how ubiquitin regulates intracellular transport
Camilla Raiborg, a postdoc of the Norwegian Cancer Society working in Harald Stenmark's group at the Department of Biochemistry of the Institute for Cancer Research, has recently published two articles together with international collaborators that reveal how the small protein ubiquitin regulates intracellular trafficking.
The first article, published in Nature Cell Biology in collaboration with the group of Ivan Dikic at the Goethe University in Frankfurt, shows that the protein machinery that controls intracellular transport (labelled red in the figure from the article) is regulated by mono-ubiquitin. Proteins such as Eps15 and Hrs function by sorting ubiquitinated membrane proteins for endocytosis and endosome-lysosome transport, respectively. The article in Nature Cell Biology (journal impact factor = 20.35) shows that mono-ubiquitination of these sorting proteins cause them to bind their "own" ubiquitin moiety instead of interacting with ubiquitinated cargo (black), and this ubiquitination of the sorting machinery has thus a negative regulatory function in intracellular protein trafficking.