糖心Volg

Claudio De Virgilio

photo

 claudio.devirgilio@unifr.ch
 +41 26 300 8656
 

Prof. Dr - Group Leader

Professeur路e ordinaire
D茅partement de biologie

PER 07 bu. 0.312A
Ch. du Mus茅e 6
1700 Fribourg
PER 07, 0.312A
+41 26 300 8656

Recherche et publications

  • Publications
    101 publications


    Nature Cell Biology (2024) | Article


    microPublication biology (2024) | Article


    The Journal of cell biology (2024) | Article

  • Projets de recherche

    MENTOR: Metabolic control of cell growth by mTOR in health and disease: a multi-disciplinary training
    Statut: En cours

    顿茅产耻迟 01.01.2025
    Fin 31.12.2028
    Financement Europe 

    Amino Acid Signaling and Growth Control in Yeast
    Statut: En cours

    顿茅产耻迟 01.08.2023
    Fin 31.07.2027
    Financement FNS 
    The eukaryotic target of rapamycin complex 1 (TORC1) kinase is a central integrator of nutritional, energy, and hormonal signals that links these metabolic cues to cell growth and homeostasis. Genetically inherited or acquired deregulation of TORC1 uncouples growth and homeostasis from the respective signals, thereby establishing conditions that drive the emergence of human diseases such as neurodegeneration, epilepsy, immunodeficiencies, cancer, and metabolic syndrome. Among the signals impinging on TORC1, amino acids are both essential and primordial cues that regulate TORC1 in part via the highly conserved Rag GTPases. 糖心Volg in various eukaryotic model systems revealed that the Rag GTPases themselves are tightly regulated by both conserved GTPase activating protein (GAP) complexes that respond to amino acid-sensory modules and by posttranslational modifications. The mechanistic aspect of these regulatory events, however, remain largely to be defined. Equally incomplete is our understanding of the mechanisms by which TORC1 feedback controls the Rag GTPases and which enable TORC1 to fulfill its role as a central metabolic rheostat. Building on both our previous Rag GTPase-centered work in yeast and on the recent discovery that Rag GTPases play conceptually different roles in anchoring TORC1 to membranes (where it can be allosterically activated by the GTPase Rheb) and in selectively recruiting specific substrates for phosphorylation by TORC1, we propose here to address some of the most pertinent questions in this field using yeast as a model system and a combination of genetic, physiological, cell biological, and biochemical approaches as we have done successfully in the past. Accordingly, we plan to study the temporal, spatial, and mechanistic aspects of how the Rag GTPases and the Rheb-orthologous Rhb1 impinge on TORC1. In parallel, we intend to refine our understanding of the feedback circuits that hosts the Rag GTPase-TORC1signaling branch, comprehensively map and characterize the functional roles of the posttranslational modifications of Rag GTPases, and corroborate emerging models by reconstituting the respective elements on liposomes. The remarkably high conservation of the amino acid-sensitive Rag GTPase-TORC1 pathway, coupled with recent observations that link Rag GTPase dysfunction to human diseases, warrant that our basic research in yeast will continue to make valuable contributions to our understanding of and provide a basis to rationally target TORC1-related diseases.

    Amino Acid Signaling and Growth Control in Yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2019
    Fin 31.07.2023
    Financement FNS 
    The eukaryotic target of rapamycin complex 1 (TORC1) integrates nutritional, energy, and hormonal signals to homeostatically regulate cellular and organismal growth and metabolism. Underscoring its prime role in these processes, deregulation of TORC1 signaling is often associated with human diseases such as cancer, immunodeficiency, and type 2 diabetes. Among the various inputs that modulate the activity of TORC1, amino acids are particularly important as they represent primordial stimuli that cannot be compensated for by any other signals. Amino acid levels are communicated to TORC1 through the GTP-/GDP-loading status of the heterodimeric Rag GTPases, which function within larger complexes coined Ragulator-Rag GTPase in mammals or EGO complex (EGOC) in yeast and which appear to predominately act on lysosomal surfaces. 糖心Volg in various model systems have identified multiple proximal Rag GTPase regulatory modules (e.g., GAPs and GEFs) and specific amino acid sensors acting upstream of these modulators, but how these sensory modules impact spatially, temporally, and mechanistically on the Rag GTPase regulators remains largely mysterious. Equally important and still mostly elusive are the feedback circuits by which TORC1 controls Rag GTPases to maintain cellular homeostasis. Building on our previous Rag GTPase-centered work in yeast, including our recent discovery of two spatially distinct endosomal and vacuolar pools of TORC1 that impinge on functionally divergent effectors, we propose here a series of experimental approaches that address some of the most pertinent and pending questions in the field. Accordingly, we plan to further explore the architecture, local regulation, and effector targeting of the endosomal and vacuolar TORC1 assemblies, to pinpoint critical amino acid sensors that feed into the EGOC-TORC1 signaling branch, and to elucidate the regulatory loops that emanate from TORC1 to feedback control the Rag GTPases. Given the remarkably high conservation of many aspects of the Rag GTPase-mediated control of TORC1, our studies will likely be both valuable for our understanding of human pathologies caused by abnormal TORC1 signaling and conducive for the development of therapeutic approaches that rationally target TORC1-related diseases.

    Amino acid signaling and growth control in yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2016
    Fin 31.07.2019
    Financement FNS 
    The target of rapamycin complex 1 (TORC1) plays a central role in the control of eukaryotic cell growth by fine-tuning anabolic and catabolic processes to the nutritional status of organisms and individual cells. Deregulation of this pathway in humans is associated with a number of pathological conditions, including cancer, obesity, and type 2 diabetes. Amino acids represent essential and primordial signals that modulate TORC1 activity through the conserved Rag family GTPases, which assemble, as part of the lysosomal/vacuolar membrane-associated mammalian Rag-Ragulator or yeast EGO complexes, into heterodimeric sub-complexes consisting of mammalian RagA or RagB and RagC or RagD, or yeast Gtr1 and Gtr2. The TORC1-stimulating state of these heterodimers contains GTP-bound RagA/B/Gtr1 and GDP-bound RagC/D/Gtr2, and is maintained by various guanine nucleotide exchange factor (GEF) and GTPase-activating (GAP) protein complexes, which are also remarkably conserved (such as for instance the heterotrimeric RagA/B- and Gtr1-GAP complexes coined GATOR1 and SEACIT, or the heterodimeric RagC/D- and Gtr2-GAP complexes termed FNIP-Folliculin and Lst4-Lst7, respectively). The amino-acid sensitive events upstream of these Rag GTPase regulators are still poorly understood, but likely involve both lysosomal amino acid sensors, such as the v-ATPase and lysosomal amino acid transporter(s), and cytoplasmic amino acid sensors such as the leucyl-tRNA synthetase (LeuRS). Here, we propose to build on and continue our previous Rag GTPase-centered research in yeast to address some of the most pertinent and outstanding questions in this field. Accordingly, we intend (i) to further refine our understanding of the architecture of the Rag GTPase containing EGO complex (EGOC), (ii) to complete the repertory of Rag GTPase regulators, (iii) to identify the respective amino acid-controlled mechanisms that impinge on these regulators, and (iv) to address the molecular mechanism by which Rag GTPases regulate TORC1 in yeast. Given the importance of TORC1 in eukaryotic cell growth control, answers to these questions will not only be interesting for our understanding of basic mechanisms in signal transduction, but also provide insight into the human pathologies that are triggered by TORC1 deregulation.

    Nutrient signal transduction and control of quiescence in yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2013
    Fin 31.07.2016
    Financement FNS 
    NUTRIENT SIGNAL TRANSDUCTION AND CONTROL OF QUIESCENCE IN YEAST Eukaryotic cell proliferation is controlled by growth factors and essential nutrients, in the absence of which cells typically enter a quiescent resting state. In the yeast Saccharomyces cerevisiae, entry into and exit from this resting state are dynamically regulated processes. They are fine-tuned by a small set of nutrient-signaling pathways among which the Target Of Rapamycin Complex 1 (TORC1) pathway, which is regulated by the abundance and quality of the available carbon and/or nitrogen source, and the glucose-responsive Protein Kinase A (PKA) pathway are particularly important. Accordingly, TORC1, via the S6 kinase (S6K) ortholog Sch9, and PKA both antagonize (in parallel) the function of a key activator of the quiescence program coined Rim15. Recent work from our lab and others uncovered that Rim15, like its orthologous counterpart in higher eukaryotes, namely the greatwall/MASTL kinase, phosphorylates the small endosulfines (Igo1/2 in yeast) to inhibit the type 2 protein phosphatase (PP2A) module PP2A-Cdc55. Since the latter event is essential for both proper cell cycle control in higher eukaryotes and entry into quiescence in yeast, in the first part of our project, we intend to continue and extend our Igo1/2-centered research by (i) dissecting the molecular details of Igo1/2-mediated control of PP2A-Cdc55, (ii) identifying and characterizing the downstream targets of the Igo1/2-PP2A-Cdc55 effector branch that are relevant for the quiescence program, and (iii) studying the potential role of Igo1/2-PP2A-Cdc55 in regulation of the G1-S cell cycle transition. In parallel to the studies on entry into quiescence, we aim to gain further insight into the mechanisms of how cells exit from quiescence. We previously found that the EGO (exit from rapamycin-induced growth arrest) protein complex (EGOC), similar to the structurally related mammalian Rag-Ragulator complex, functions as a critical hub that relays amino acid signals to TORC1. Based on our recent discoveries that the leucyl-tRNA synthetase controls TORC1 by regulating the GTP-loading status of the Rag GTPase Gtr1 within EGOC and the identification of a bona fide Gtr1-GAP, we propose here a set of approaches to address some of the currently most pertinent questions in the field, i.e. (i) how do amino acids regulate structural and functional aspects of EGOC and how does EGOC activate TORC1?, (ii) which regulatory mechanisms (e.g., GAPs and GEFs) impinge on the Rag GTPases?, and (iii) which of the TORC1 effector branches incite cells to exit quiescence? Deregulation of TORC1 in humans is associated with distinct cancers and cancer predisposition hypertrophic syndromes that are all characterized by pathologically high cell growth. 糖心Volg aiming to identify the conserved regulators that impinge on, or effectors that are regulated by TORC1, such as the ones proposed here, are therefore likely to contribute to both our basic understanding of cell growth and quiescence and the development of diagnostic and therapeutic tools for the treatment of diseases associated with aberrant TORC1 function.

    Nutrient signal transduction and control of quiescence in yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2010
    Fin 31.07.2013
    Financement FNS 
    Regulation of cell proliferation and growth in response to extracellular cues like growth factors, hormones and/or nutrients critically affects development and life span in virtually every biological system examined. In the absence of stimulatory signals, cells may enter into a reversible quiescence (or G0) state that is typically characterized by low metabolic activity, including low rates of protein synthesis and transcription. While in metazoans quiescence is induced following limitation of growth factors and hormones, in simpler, unicellular organisms, quiescence is primarily induced by nutrient limitation and ensures maximal long-term survival (also referred to as chronological life span [CLS]). Despite the universal importance of the quiescent state, the mechanisms regulating entry into, survival in, and exit from quiescence remain poorly understood. This proposal is focused on the molecular analysis of signaling events that critically control initiation of and exit from the G0 program, using the unicellular eukaryote S. cerevisiae as a model system. Initiation of the yeast quiescence program is a highly coordinated process, which requires downregulation of conserved nutrient-responsive signal transduction pathways. Specifically, inhibiting the kinase activities of the Target Of Rapamycin Complex 1 (TORC1) or the protein kinase A (PKA) had been found to drive cells into a quiescent-like state and to significantly extend CLS. In contrast, reducing the kinase activity of Rim15 precludes access to quiescence and decreases CLS. While TORC1 (via its substrate Sch9) and PKA are thought to signal in parallel pathways to positively regulate ribosome biogenesis and growth, they negatively regulate quiescence and CLS by maintaining Rim15 in an inactive state in the cytoplasm. The molecular elements linking Rim15 to distal readouts including the expression of specific nutrient-regulated genes, trehalose and glycogen accumulation, extension of CLS, and induction of autophagy are presently only partially characterized, but involve the stress-response and post-diauxic shift transcription factors Msn2/4 and Gis1, respectively, and the paralogous Rim15 target proteins Igo1 and Igo2. In this context, two of the specific aims of this proposal are (i) the elucidation the molecular function of Igo1 and Igo2 and (ii) the isolation and characterization of additional Rim15 target proteins. Furthermore, we are directing our efforts toward completing the inventory of Rim15 target proteins using both proteome chip analyses and quantitative, label-free mass spectrometry approaches. Exit from the yeast quiescence program is also a highly regulated, yet poorly understood process. In a search for (ego) mutants exhibiting a specific defect in exit from a rapamycin-induced growth arrest, we previously identified the vacuolar membrane-associated EGO protein complex (EGOC). We showed recently that EGOC, consisting of Ego1, Ego3, and the two GTPases Gtr1 and Gtr2, functions upstream of TORC1 to mediate amino acid signaling. Specifically, we found that TORC1 activity is dictated by the nucleotide-bound state of Gtr1 and that Vam6 functions as a guanine-nucleotide exchange factor (GEF) for Gtr1. In this context, further aims of this proposal are (i) the isolation of additional Gtr1/2 regulatory proteins, (ii) characterization of their interactions within the EGOC, and (iii) study of their potential role in nutrient-regulated activation/inactivation of TORC1. Our studies so far have uncovered that the nutrient-regulated hub TORC1 orchestrates both entry into and exit from G0. Since hyperactivation of mammalian TORC1 (mTORC1) has been implicated in a number of cancers and cancer predisposition hypertrophic syndromes, our studies are likely to contribute to the understanding, and hopefully treatment, of such diseases.

    Nutrient signal transduction and control of quisecence in yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2007
    Fin 31.07.2010
    Financement FNS 
    Regulation of cell proliferation and growth in response to extracellular cues like growth factors, hormones and/or nutrients critically affects development and life span in virtually every biological system examined. In the absence of stimulatory signals, cells may enter into a reversible quiescence (or G0) state that is typically characterized by low metabolic activity, including low rates of protein synthesis and transcription. While in metazoans quiescence is induced following limitation of growth factors and hormones, in simpler, unicellular organisms, quiescence is primarily induced by nutrient limitation and ensures maximal long-term survival (also referred to as chronological life span [CLS]). Despite the universal importance of the quiescent state, the mechanisms regulating entry into, survival in, and exit from quiescence remain poorly understood. This proposal is focused on the molecular analysis of signaling events that critically control initiation of and exit from the G0 program, using the unicellular eukaryote S. cerevisiae as a model system. Initiation of the yeast quiescence program is a highly coordinated process, which requires downregulation of conserved nutrient-responsive signal transduction pathways. Specifically, inhibiting the kinase activities of the Target Of Rapamycin Complex 1 (TORC1) or the protein kinase A (PKA) had been found to drive cells into a quiescent-like state and to significantly extend CLS. In contrast, reducing the kinase activity of Rim15 precludes access to quiescence and decreases CLS. While TORC1 (via its substrate Sch9) and PKA are thought to signal in parallel pathways to positively regulate ribosome biogenesis and growth, they negatively regulate quiescence and CLS by maintaining Rim15 in an inactive state in the cytoplasm. The molecular elements linking Rim15 to distal readouts including the expression of specific nutrient-regulated genes, trehalose and glycogen accumulation, extension of CLS, and induction of autophagy are presently only partially characterized, but involve the stress-response and post-diauxic shift transcription factors Msn2/4 and Gis1, respectively, and the paralogous Rim15 target proteins Igo1 and Igo2. In this context, two of the specific aims of this proposal are (i) the elucidation the molecular function of Igo1 and Igo2 and (ii) the isolation and characterization of additional Rim15 target proteins. Furthermore, we are directing our efforts toward completing the inventory of Rim15 target proteins using both proteome chip analyses and quantitative, label-free mass spectrometry approaches. Exit from the yeast quiescence program is also a highly regulated, yet poorly understood process. In a search for (ego) mutants exhibiting a specific defect in exit from a rapamycin-induced growth arrest, we previously identified the vacuolar membrane-associated EGO protein complex (EGOC). We showed recently that EGOC, consisting of Ego1, Ego3, and the two GTPases Gtr1 and Gtr2, functions upstream of TORC1 to mediate amino acid signaling. Specifically, we found that TORC1 activity is dictated by the nucleotide-bound state of Gtr1 and that Vam6 functions as a guanine-nucleotide exchange factor (GEF) for Gtr1. In this context, further aims of this proposal are (i) the isolation of additional Gtr1/2 regulatory proteins, (ii) characterization of their interactions within the EGOC, and (iii) study of their potential role in nutrient-regulated activation/inactivation of TORC1. Our studies so far have uncovered that the nutrient-regulated hub TORC1 orchestrates both entry into and exit from G0. Since hyperactivation of mammalian TORC1 (mTORC1) has been implicated in a number of cancers and cancer predisposition hypertrophic syndromes, our studies are likely to contribute to the understanding, and hopefully treatment, of such diseases.

    Understanding and treatment of mTORC1-dependent hyperproliferative diseases
    Statut: Termin茅

    顿茅产耻迟 01.05.2007
    Fin 30.04.2010
    Financement Autre 
    ...

    Nutrient-regulated protein kineases and cell proliferation control in yeast
    Statut: Termin茅

    顿茅产耻迟 01.08.2005
    Fin 31.07.2007
    Financement FNS 

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