Villers, Jennifer
[UCL]
Yeast cells can grow on a wide variety of nitrogen sources, and, according to the quality of the source, modulate their set of nitrogen transporters present at the plasma membrane. The addition of a preferred nitrogen source to proline-grown cells induces the transcriptional repression of genes encoding transporters of non-preferred nitrogen sources. This gene regulation is called Nitrogen Catabolite Repression (NCR) and many transcriptomic studies were carried out to identify NCR-sensitive genes. Other regulations are possible at the post-translational level. For instance, the general amino acid permease Gap1 is rapidly ubiquitylated, endocytosed and degraded in the vacuole in an Rsp5-Bul1/2-dependent manner. However, little is known about the nitrogen-induced post-translational regulation of other plasma membrane transporters. In this study, we used a large-scale proteomic approach to identify plasma membrane proteins that are regulated by the nitrogen source. We found seventeen plasma membrane proteins more abundant when grown in proline-containing medium, and four proteins more abundant when grown in the presence of ammonium. Using the same global proteomic approach, we showed that five NCR-sensitive nitrogen transporters—Gap1, Put4, Opt2, Dal5 and Ptr2—are endocytosed and degraded after addition of a preferred nitrogen source to proline-grown cells. Although the degradation kinetics is different for each transporter, it is Rsp5-dependent for at least four of them—Gap1, Put4, Dal5 and Ptr2. Surprisingly, we found that the deletion of the Bul1 and Bul2 ubiquitin ligase adaptors increases vacuolar trafficking and degradation of Put4, Dal5 and Ptr2 in proline-grown cells. The exact role of Bul1 and Bul2 in this process remains to be determined. To conclude, we can argue that mass spectrometry is a technique of choice to monitor the nitrogen-induced remodeling of the plasma membrane proteome and to approach the study of endocytic mechanisms.
Bibliographic reference |
Villers, Jennifer. Impact of the nitrogen source on the remodeling of the yeast plasma membrane proteome. Prom. : Morsomme , Pierre |
Permanent URL |
http://hdl.handle.net/2078.1/171757 |