Snf1/AMPK fine-tunes TORC1 signaling in response to glucose starvation
- University of Fribourg, Switzerland
- University of Milano-Bicocca, Italy
- University of Freiburg, Germany
- KU Leuven, Belgium
Abstract
The AMP-activated protein kinase (AMPK) and the target of rapamycin complex 1 (TORC1) are central kinase modules of two opposing signaling pathways that control eukaryotic cell growth and metabolism in response to the availability of energy and nutrients. Accordingly, energy depletion activates AMPK to inhibit growth, while nutrients and high energy levels activate TORC1 to promote growth. Both in mammals and lower eukaryotes such as yeast, the AMPK and TORC1 pathways are wired to each other at different levels, which ensures homeostatic control of growth and metabolism. In this context, a previous study (Hughes Hallet et. al, 2015) reported that AMPK in yeast, i.e. Snf1, prevents the transient TORC1 reactivation during the early phase following acute glucose starvation, but the underlying mechanism has remained elusive. Using a combination of unbiased mass spectrometry (MS)-based phosphoproteomics, genetic, biochemical, and physiological experiments, we show here that Snf1 temporally maintains TORC1 inactive in glucose-starved cells primarily through the TORC1-regulatory protein Pib2. Our data, therefore, extend the function of Pib2 to a hub that integrates both glucose and, as reported earlier, glutamine signals to control TORC1. We further demonstrate that Snf1 phosphorylates the TORC1 effector kinase Sch9 within its N-terminal region and thereby antagonizes the phosphorylation of a C-terminal TORC1-target residue within Sch9 itself that is critical for its activity. The consequences of Snf1-mediated phosphorylation of Pib2 and Sch9 are physiologically additive and sufficient to explain the role of Snf1 in short-term inhibition of TORC1 in acutely glucose-starved cells.
Data availability
All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1-6 and Supplementary figures 1-3. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD037381
Article and author information
Author details
Claudio De Virgilio
Funding
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (310030_166474/184671)
- Marco Caligaris
- Raffaele Nicastro
- Benjamin Pillet
- Claudio De Virgilio
Deutsche Forschungsgemeinschaft (RO 1028/5-2)
- Sabine Rospert
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (310030_184781)
- Zehan Hu
- Jörn Dengjel
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (316030_177088)
- Zehan Hu
- Jörn Dengjel
Fonds Wetenschappelijk Onderzoek (G069413)
- Marie-Anne Deprez
- Joris Winderickx
Fonds Wetenschappelijk Onderzoek (G0C7222N)
- Marie-Anne Deprez
- Joris Winderickx
Katholieke Universiteit Leuven (C14/17/063)
- Marie-Anne Deprez
- Joris Winderickx
Katholieke Universiteit Leuven (C14/21/095)
- Marie-Anne Deprez
- Joris Winderickx
Ministero dell'Università e della Ricerca (2020-ATE-0329)
- Farida Tripodi
- Paola Coccetti
Deutsche Forschungsgemeinschaft (Project-ID 403222702 - SFB 1381,TP B08)
- Johannes Erwin Hummel
- Sabine Rospert
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Caligaris et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,211
- views
-
- 499
- downloads
-
- 27
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Snf1/AMPK fine-tunes TORC1 signaling in response to glucose starvation
eLife 12:e84319.
https://doi.org/10.7554/eLife.84319
Further reading
-
- Biochemistry and Chemical Biology
In healthy cells, cyclin D1 is expressed during the G1 phase of the cell cycle, where it activates CDK4 and CDK6. Its dysregulation is a well-established oncogenic driver in numerous human cancers. The cancer-related function of cyclin D1 has been primarily studied by focusing on the phosphorylation of the retinoblastoma (RB) gene product. Here, using an integrative approach combining bioinformatic analyses and biochemical experiments, we show that GTSE1 (G-Two and S phases expressed protein 1), a protein positively regulating cell cycle progression, is a previously unrecognized substrate of cyclin D1–CDK4/6 in tumor cells overexpressing cyclin D1 during G1 and subsequent phases. The phosphorylation of GTSE1 mediated by cyclin D1–CDK4/6 inhibits GTSE1 degradation, leading to high levels of GTSE1 across all cell cycle phases. Functionally, the phosphorylation of GTSE1 promotes cellular proliferation and is associated with poor prognosis within a pan-cancer cohort. Our findings provide insights into cyclin D1’s role in cell cycle control and oncogenesis beyond RB phosphorylation.
-
- Biochemistry and Chemical Biology
- Microbiology and Infectious Disease
Teichoic acids (TA) are linear phospho-saccharidic polymers and important constituents of the cell envelope of Gram-positive bacteria, either bound to the peptidoglycan as wall teichoic acids (WTA) or to the membrane as lipoteichoic acids (LTA). The composition of TA varies greatly but the presence of both WTA and LTA is highly conserved, hinting at an underlying fundamental function that is distinct from their specific roles in diverse organisms. We report the observation of a periplasmic space in Streptococcus pneumoniae by cryo-electron microscopy of vitreous sections. The thickness and appearance of this region change upon deletion of genes involved in the attachment of TA, supporting their role in the maintenance of a periplasmic space in Gram-positive bacteria as a possible universal function. Consequences of these mutations were further examined by super-resolved microscopy, following metabolic labeling and fluorophore coupling by click chemistry. This novel labeling method also enabled in-gel analysis of cell fractions. With this approach, we were able to titrate the actual amount of TA per cell and to determine the ratio of WTA to LTA. In addition, we followed the change of TA length during growth phases, and discovered that a mutant devoid of LTA accumulates the membrane-bound polymerized TA precursor.
