Molecular Physiology of the Cell

Time flies… Our very first publication reporting a potential role of ubiquitin in downregulation of plasma membrane transporters was released in 1995, so 20 years ago. Claudine Hein, a PhD student of the lab, constructed a myc-tagged version of the Gap1 permease, allowing her to show that the inhibition of Gap1 activity observed after addition of ammonium coincides with degradation of the protein. This result surprised us as the inhibitory effect of ammonium on Gap1 was thought to be reversible. This regulation of Gap1 by ammonium had been described in 1983 by Marcelle Grenson who also isolated a mutant strain, npi1 (nitrogen permease inactivator 1), in which this regulation is defective (Grenson, 1983). Jean-Yves Springael, another PhD student of the lab, used this mutant to clone the NPI1 gene and realized that it corresponds to the RSP5 gene just shown by Johan Huibregtse and coll. to code for a new type of ubiquitin ligase, but whose molecular function remained unclear (Huibregtse et al. 1995). Finally, the paper reports the data of a collaboration with the group of Rosine Haguenauer-Tsapis (J. Monod Institute, Paris) showing that Npi1/Rsp5 is also required for stress-induced degradation of the uracil permease, a process known to involve prior endocytosis of the protein. Altogether, these observations indicated that the yeast Npi1/Rsp5 ubiquitin ligase plays a central role in endocytosis of several transporters.  Furthermore, Npi1/Rsp5 turned out to be conserved in mammals, suggesting that ubiquitin could serve as a signal for protein endocytosis in more complex species as well (what was later confirmed). This article, published in 1995 in the journal Molecular Microbiology, remains  one of our best cited papers (306 citations in August 2015). Time flies …

A relaxation single day all together in Venice ?  This is possible thanks to the excellent low-cost connection between Gosselies and Venice, so we made it ! The weather was not so good but we could enjoy walking in the small streets and flowered squares, visiting churches and the amazing Piazza San Marco, and vaporetting to the Murano island. A wonderful day.

The “Matinées de Microbiologie Moléculaire” meeting (3M) was organized in Gosselies on 27 and 28 January. Young PhD students and postdocs of the “Molecular microbiology” group of IBMM gave excellent presentations, including Elie Saliba (who talked about the role of arrestins in Gap1 permease endocytosis) and Melody Cools (who presented data on characterization of novel yeast vacuolar transporters) from our lab.

Excellent news for Céline Barthélemy, who was informed by the FNRS that she obtained a fellowship from the FRIA. Céline thus joins the lab as a PhD student and will pursue the work she initiated during her master thesis about the intracellular trafic of LAT1, a human amino acid transporter overexpressed in cancer cells. Congratulations to Céline !

B. André attended the “Vesicular traffic” one-day conference, November 19th, organized at Collège de France of Paris, where James E. Rothman, Randy W. Schekman and Thomas C. Südhof, the 2013 laureates of the Physiology and Medicine Nobel prize for their discoveries on the molecular and cellular principles of membrane traffic, presented the last results of their research. Other presentations by French colleagues also contributed to the top quality of this scientific event. What was particularly interesting is the 2nd part of Randy Schekman’s presentation about the scientific publication in top journals and the “Elife” journal concept as an alternative. All presentations are available on line.