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On May 13, the group of Isabelle Georis and our laboratory co-organized the “Yeasterday” meeting in Brussels. This annual meeting gathers scientists from the Benelux who use yeast as a model system or a tool in their research. The oral presentations given by young colleagues (PhD students and postdocs) were of top quality. Luis Sousa from our lab had the opportunity to present his work about amino acid excretion by yeast cells. The final plenary lecture was presented by Dr. Isabelle Sagot (CNRS, IBGC, Bordeaux) about the “The cell biology of quiescent yeast”. We thank all speakers, attendees and sponsors (Paelo, Syngulon FNRS, Rocc, aquilabiolabs) for this exciting science sharing day !
 We are pleased to announce the publication in iScience of an article entitled “Plasma membrane H+-ATPases promote TORC1 activation in plant suspension cells“. This study was carried out by Dr. Cecilia Primo in tight collaboration with the group of Pr. François Chaumont (UCLouvain, Belgium). The article reports that similar to what we have shown in yeast (Saliba et al. 2018, 2021), plasma membrane H+-ATPases in plant cells play an important role in regulation of TORC1 (Target Of Rapamycin Complex 1), the kinase complex coordinating cell growth and metabolism. This study opens the perspectives of better understanding the well-established role of these H+ pumps in regulation of plant cell growth and exploiting this new knowledge in biotechnological processes.
Good news for the end of this year! Christopher Dereppe was informed by the FNRS that he’s among the laureates of the last competition for FRIA fellowships. Christopher obtained a master diploma in Biochemistry and Molecular and Cellular Biology in 2021 at ULB. He did his master thesis work in our lab where he investigated a novel pathway of TORC1 activation in yeast. He will now further investigate the signals and molecular mechanisms of this pathway. Congratulations to him !
George Kapetanakis and Bruno André attended the 71st National Conference of the Hellenic Society of Biochemistry & Molecular Biology. George K. gave a presentation on his recent work on amino acid export proteins and Bruno A. was invited to give a conference on TOR regulation in yeast.
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.
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