| Protein trafficking and Degradation |
Arrestins and intracellular traffic in Saccharomyces cerevisiae
Our objective is to characterize the function of proteins of the arrestin family (Art1-8) as endocytic adaptors in the model organism Saccharomyces cerevisiae. The results of this study could reveal important aspects of the regulation of these proteins, conserved throughout the evolution. In order to determine the process in which these proteins are involved, we carried out two-hybrid screenings with several members of this protein family and protein-protein interactions were further characterized. This study, as part of a colaboration with other groups, showed that Art4 (Rod1) acts as a downstream effector of the Snf1/AMPK signaling pathway to regulate the glucose-induced endocytosis of the lactate transporter Jen1.
Molecular mechanisms of protein monoubiquitination
Our previous studies showed that the arrestin-related protein Rim8 (Art9) functions as an adaptor that mediates the recruitment of the ESCRT (“Endosomal Sorting Complex Required for Transport”) endocytic machinery to a seven-transmembrane spanning receptor. Additionally, we found that the ESCRT subunit Vps23 is required for Rim8 monoubiquitination. To analyze this process, we set up an in vitro ubiquitination assay. By using this approach, we were able to show that the ubiquitin binding UEV (“Ubiquitin E2 Variant”) domain of Vps23 is sufficient to prevent the protein to be further polyubiquitinated and thus, directs its monoubiquitination. This result is of great interest since protein monoubiquitination plays an essential role in eukaryotic cells and the mechanisms underlying this process are still largely unknown.