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Yeast cells can excrete metabolites, in particular amino acids. These compounds can then be used by other microorganisms which can establish mutualistic interaction with yeast. How do yeast cells excrete amino acids remains poorly known. Thanks to a fruitful collaboration with the group of Dr. Isabelle Georis (Labiris, Anderlecht), George Kapetanakis (PhD student supported by FRIA) characterized Aqr1, Qdr2 and Qdr3 as three amino-acid exporters. Importantly, a yeast triple mutant lacking these proteins displays reduced capability of cross-feeding lactic acid bacteria, which cannot grow without an external amino acid supply. This study entitled “Overlapping Roles of Yeast Transporters Aqr1, Qdr2, and Qdr3 in Amino Acid Excretion and Cross-Feeding of Lactic Acid Bacteria” has just been published in the journal “Frontiers in Microbiology”.
Lactic acid bacteria are frequently found as contaminants during biofuel ethanol fermentation processes, and these infections represent a pervasive problem for many companies. As the yeast mutant described in our study provides a potential solution to this industrial problem, ULB has patented it. Furthermore, a proof of concept (POC) project supported by the Région wallonne now allows us to assess the efficiency of our invention under industrial conditions in collaboration with the start-up company Syngulon.
G. Kapetanalis and L. Sousa attended the 2021 edition of the “Levures, modèles et outils (LMO)” meeting organized in Strasbourg on 27-29 October. They both gave a brief presentation about their work on excretion of amino acids by yeast cells and its potential industrial applications.
A fruitful collaboration with the group of Dr. C. Gournas, former postdoc in the lab, led to publication of a novel article entitled “The Bul1/2 Alpha-Arrestins Promote Ubiquitylation and Endocytosis of the Can1 Permease upon Cycloheximide-Induced TORC1-Hyperactivation “ by Megarioti et al. . In this work, we dissected the mechanisms responsible for ubiquitylation and endocytosis of the yeast Can1 arginine transporter via arrestin-like adaptors under the control of “Target of Rapamycin Complex 1” (TORC1) in yeast.
C. Primo and B. André attended the last edition of the EMBO workshop on “Target of Rapamycin (TOR) signaling in photosynthetic organisms” organized online on 21 – 24 October. Cecilia presented a recorded flash-talk about her recent work on TOR control by H+-ATPases in BY-2 plant cells in collaboration with the lab of Pr. François Chaumont (UCLouvain).
N. Guarini, C. Primo and B. André participated to the last “TOR de France” meeting organized at Nice on 14-15 October. This international meeting gathers every two years, in a nice place in France, scientists studying the “Target Of Rapamycin” (TOR) kinase involved in control of cell growth and associated with several diseases including cancers. It was the first time we had the opportunity to attend a meeting abroad since November 2019. At the end of the meeting, a special prize for the “best poster” has been granted to … Nadia ! She presented her recent results about the role of yeast H+-ATPases in TORC1 control. Congratulations Nadia !
In a novel article entitled “A plant plasma-membrane H+-ATPase promotes yeast TORC1 activation via its carboxy-terminal tail” published in Scientific reports, we further investigate the activation of yeast TORC1 by nutrient uptake. In a previous study, we found that the influx of H+ coupled to active transport of amino acids or other nutrients generates a signal stimulating TORC1 activity. Furthermore, the plasma membrane H+-ATPase (Pma1) proved to be a central actor of this activation, involving more than just establishment of the H+ gradient (Saliba et al. 2018). We now report that a plant H+-ATPase can substitute for Pma1 in yeast to promote H+-elicited TORC1 activation. Furthermore, a mutant form of this H+-ATPase, that remains fully active, fails to activate TORC1, suggesting that the protein signals to TORC1. We discuss the model that fungi and plants might share a conserved mechanism of TORC1 activation that could be crucial in growth control of both categories of organisms. The authors of the study are Elie Saliba, Cecilia Primo, Nadia Guarini and B. André.
Great news! Luis Sousa was informed by the FNRS that he’s among the laureates of the 2021 competition for FRIA fellowships. Luis obtained a master diploma in Biotechnology at the University of Lisbon (Portugal), Instituto Superior Tecnico, in 2019. In July 2020, he moved to Belgium and was hired by the Syngulon startup for three months, during which he carried out experiments as part of a collaboration we established with the company. The topic of his thesis project is the mechanisms and roles of amino acids excretion by yeast cells.
Lab members together with I. Georis took a full day for a walk and picnic in beautiful woods and along the Sambre river in Montigny-le-Tilleul. A well-deserved relaxing day for everyone.
In a novel article entitled “Nitrogen coordinated import and export of arginine across the yeast vacuolar membrane” just published in PLoS Genetics, we report an extensive study of the arginine transporters localized at the yeast vacuolar membrane. We describe Vsb1 as a novel transmembrane protein acting as the main vacuolar arginine import system. We also report that Ypq2, a vacuolar transporter homologous to the human lysosomal PQLC2 protein, importantly contributes to arginine export from the vacuole where the amino acid is stored at high levels Finally, we provide clear evidence that Vsb1 and Ypq2 are inversely regulated by nitrogen supply. This paper is signed as a first author by Melody Cools who did her PhD in our lab and who established the methodology needed for conducting this study. Melody is now scientist at the Labiris institute where she pursues her research work on yeast vacuolar transporters and their regulation. This work has benefited from the valuable collaboration of Dr. Isabelle Georis (Labiris) and Pr. Alexander DeLuna (Guanajuato, Mexico).
On March 20, our lab was closed, like all others in our university. Since then, we regularly had lab meetings and journal clubs via Teams or Zoom, online tools we never used before. Three of us (Catherine, Simon and Bruno) joined the platform that was rapidly implemented in our institute (thanks to efforts of our colleagues C. Gueydan and G. De Muylder) to carry out coronavirus qRT-PCR tests for hospitals and nursing houses around Charleroi.
From May 6th, the lab is open again, with application of strict distance and hygiene rules. Thanks very much to Catherine who had in charge to organize this and who did an incredible job to collect masks for everyone, define safety rules and equip each room. Most of us could thus take over experiments which is good news. Hopefully normal life will be back soon.
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