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Schoonover MG, Chilson EC, Strome ED. Heterozygous Mutations in Aromatic Amino Acid Synthesis Genes Trigger TOR Pathway Activation in Saccharomyces cerevisiae.. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000685. [PMID: 36468155 PMCID: PMC9713580 DOI: 10.17912/micropub.biology.000685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 11/02/2022] [Accepted: 11/15/2022] [Indexed: 01/25/2023]
Abstract
The highly conserved complexes of Target of Rapamycin (TORC1 and TORC2) are central regulators to many vital cellular processes including growth and autophagy in response to nutrient availability. Previous research has extensively elucidated exogenous nutrient control on TORC1/TORC2; however, little is known about the potential alteration of nutrient pools from mutations in biosynthesis pathways and their impact on Tor pathway activity. Here, we analyze the impacts of heterozygous mutations in aromatic amino acid biosynthesis genes on TOR signaling via differential expression of genes downstream of TORC1 and autophagy induction for TORC1 and TORC2 activity.
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2
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Huang C, Li L, Wang L, Bao J, Zhang X, Yan J, Wu J, Cao N, Wang J, Zhao L, Liu X, Yu X, Zhu X, Lin F. The Amino Acid Permease MoGap1 Regulates TOR Activity and Autophagy in Magnaporthe oryzae. Int J Mol Sci 2022; 23:13663. [PMID: 36362450 PMCID: PMC9655246 DOI: 10.3390/ijms232113663] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 11/01/2022] [Accepted: 11/02/2022] [Indexed: 08/26/2023] Open
Abstract
Rice is an important food crop all over the world. It can be infected by the rice blast fungus Magnaporthe oryzae, which results in a significant reduction in rice yield. The infection mechanism of M. oryzae has been an academic focus for a long time. It has been found that G protein, AMPK, cAMP-PKA, and MPS1-MAPK pathways play different roles in the infection process. Recently, the function of TOR signaling in regulating cell growth and autophagy by receiving nutritional signals generated by plant pathogenic fungi has been demonstrated, but its regulatory mechanism in response to the nutritional signals remains unclear. In this study, a yeast amino acid permease homologue MoGap1 was identified and a knockout mutant of MoGap1 was successfully obtained. Through a phenotypic analysis, a stress analysis, autophagy flux detection, and a TOR activity analysis, we found that the deletion of MoGap1 led to a sporulation reduction as well as increased sensitivity to cell wall stress and carbon source stress in M. oryzae. The ΔMogap1 mutant showed high sensitivity to the TOR inhibitor rapamycin. A Western blot analysis further confirmed that the TOR activity significantly decreased, which improved the level of autophagy. The results suggested that MoGap1, as an upstream regulator of TOR signaling, regulated autophagy and responded to adversities such as cell wall stress by regulating the TOR activity.
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Affiliation(s)
- Changli Huang
- Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences, China Jiliang University, Hangzhou 310018, China
| | - Lin Li
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
| | - Lei Wang
- College of Advanced Agricultural Sciences, Zhejiang Agriculture and Forest University, Hangzhou 310007, China
| | - Jiandong Bao
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
| | - Xiaozhi Zhang
- College of Advanced Agricultural Sciences, Zhejiang Agriculture and Forest University, Hangzhou 310007, China
| | - Jiongyi Yan
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Jiaqi Wu
- Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences, China Jiliang University, Hangzhou 310018, China
| | - Na Cao
- College of Biotechnology, Tianjin University of Science & Technology, Tianjin 300457, China
| | - Jiaoyu Wang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
- College of Advanced Agricultural Sciences, Zhejiang Agriculture and Forest University, Hangzhou 310007, China
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Lili Zhao
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
| | - Xiaohong Liu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Xiaoping Yu
- Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences, China Jiliang University, Hangzhou 310018, China
| | - Xueming Zhu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
- College of Advanced Agricultural Sciences, Zhejiang Agriculture and Forest University, Hangzhou 310007, China
| | - Fucheng Lin
- Zhejiang Provincial Key Laboratory of Biometrology and Inspection & Quarantine, College of Life Sciences, China Jiliang University, Hangzhou 310018, China
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
- College of Advanced Agricultural Sciences, Zhejiang Agriculture and Forest University, Hangzhou 310007, China
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
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3
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The NPR/Hal family of protein kinases in yeasts: biological role, phylogeny and regulation under environmental challenges. Comput Struct Biotechnol J 2022; 20:5698-5712. [PMID: 36320937 PMCID: PMC9596735 DOI: 10.1016/j.csbj.2022.10.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 09/30/2022] [Accepted: 10/02/2022] [Indexed: 11/30/2022] Open
Abstract
Protein phosphorylation is the most common and versatile post-translational modification occurring in eukaryotes. In yeast, protein phosphorylation is fundamental for maintaining cell growth and adapting to sudden changes in environmental conditions by regulating cellular processes and activating signal transduction pathways. Protein kinases catalyze the reversible addition of phosphate groups to target proteins, thereby regulating their activity. In Saccharomyces cerevisiae, kinases are classified into six major groups based on structural and functional similarities. The NPR/Hal family of kinases comprises nine fungal-specific kinases that, due to lack of similarity with the remaining kinases, were classified to the “Other” group. These kinases are primarily implicated in regulating fundamental cellular processes such as maintaining ion homeostasis and controlling nutrient transporters’ concentration at the plasma membrane. Despite their biological relevance, these kinases remain poorly characterized and explored. This review provides an overview of the information available regarding each of the kinases from the NPR/Hal family, including their known biological functions, mechanisms of regulation, and integration in signaling pathways in S. cerevisiae. Information gathered for non-Saccharomyces species of biotechnological or clinical relevance is also included.
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Thorner J. TOR complex 2 is a master regulator of plasma membrane homeostasis. Biochem J 2022; 479:1917-1940. [PMID: 36149412 PMCID: PMC9555796 DOI: 10.1042/bcj20220388] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/30/2022] [Accepted: 09/01/2022] [Indexed: 11/17/2022]
Abstract
As first demonstrated in budding yeast (Saccharomyces cerevisiae), all eukaryotic cells contain two, distinct multi-component protein kinase complexes that each harbor the TOR (Target Of Rapamycin) polypeptide as the catalytic subunit. These ensembles, dubbed TORC1 and TORC2, function as universal, centrally important sensors, integrators, and controllers of eukaryotic cell growth and homeostasis. TORC1, activated on the cytosolic surface of the lysosome (or, in yeast, on the cytosolic surface of the vacuole), has emerged as a primary nutrient sensor that promotes cellular biosynthesis and suppresses autophagy. TORC2, located primarily at the plasma membrane, plays a major role in maintaining the proper levels and bilayer distribution of all plasma membrane components (sphingolipids, glycerophospholipids, sterols, and integral membrane proteins). This article surveys what we have learned about signaling via the TORC2 complex, largely through studies conducted in S. cerevisiae. In this yeast, conditions that challenge plasma membrane integrity can, depending on the nature of the stress, stimulate or inhibit TORC2, resulting in, respectively, up-regulation or down-regulation of the phosphorylation and thus the activity of its essential downstream effector the AGC family protein kinase Ypk1. Through the ensuing effect on the efficiency with which Ypk1 phosphorylates multiple substrates that control diverse processes, membrane homeostasis is maintained. Thus, the major focus here is on TORC2, Ypk1, and the multifarious targets of Ypk1 and how the functions of these substrates are regulated by their Ypk1-mediated phosphorylation, with emphasis on recent advances in our understanding of these processes.
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Affiliation(s)
- Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, U.S.A
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5
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2-deoxyglucose transiently inhibits yeast AMPK signaling and triggers glucose transporter endocytosis, potentiating the drug toxicity. PLoS Genet 2022; 18:e1010169. [PMID: 35951639 PMCID: PMC9398028 DOI: 10.1371/journal.pgen.1010169] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 08/23/2022] [Accepted: 07/20/2022] [Indexed: 11/19/2022] Open
Abstract
2-deoxyglucose is a glucose analog that impacts many aspects of cellular physiology. After its uptake and its phosphorylation into 2-deoxyglucose-6-phosphate (2DG6P), it interferes with several metabolic pathways including glycolysis and protein N-glycosylation. Despite this systemic effect, resistance can arise through strategies that are only partially understood. In yeast, 2DG resistance is often associated with mutations causing increased activity of the yeast 5’-AMP activated protein kinase (AMPK), Snf1. Here we focus on the contribution of a Snf1 substrate in 2DG resistance, namely the alpha-arrestin Rod1 involved in nutrient transporter endocytosis. We report that 2DG triggers the endocytosis of many plasma membrane proteins, mostly in a Rod1-dependent manner. Rod1 participates in 2DG-induced endocytosis because 2DG, following its phosphorylation by hexokinase Hxk2, triggers changes in Rod1 post-translational modifications and promotes its function in endocytosis. Mechanistically, this is explained by a transient, 2DG-induced inactivation of Snf1/AMPK by protein phosphatase 1 (PP1). We show that 2DG-induced endocytosis is detrimental to cells, and the lack of Rod1 counteracts this process by stabilizing glucose transporters at the plasma membrane. This facilitates glucose uptake, which may help override the metabolic blockade caused by 2DG, and 2DG export—thus terminating the process of 2DG detoxification. Altogether, these results shed a new light on the regulation of AMPK signaling in yeast and highlight a remarkable strategy to bypass 2DG toxicity involving glucose transporter regulation.
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Barata-Antunes C, Talaia G, Broutzakis G, Ribas D, De Beule P, Casal M, Stefan CJ, Diallinas G, Paiva S. Interactions of cytosolic tails in the Jen1 carboxylate transporter are critical for trafficking and transport activity. J Cell Sci 2022; 135:275079. [PMID: 35437607 DOI: 10.1242/jcs.260059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 04/05/2022] [Indexed: 12/26/2022] Open
Abstract
Plasma membrane (PM) transporters of the major facilitator superfamily (MFS) are essential for cell metabolism, growth and response to stress or drugs. In Saccharomyces cerevisiae, Jen1 is a monocarboxylate/H+ symporter that provides a model to dissect the molecular details underlying cellular expression, transport mechanism and turnover of MFS transporters. Here, we present evidence revealing novel roles of the cytosolic N- and C-termini of Jen1 in its biogenesis, PM stability and transport activity, using functional analyses of Jen1 truncations and chimeric constructs with UapA, an endocytosis-insensitive transporter of Aspergillus nidulans. Our results show that both N- and C-termini are critical for Jen1 trafficking to the PM, transport activity and endocytosis. Importantly, we provide evidence that Jen1 N- and C-termini undergo transport-dependent dynamic intramolecular interactions, which affect the transport activity and turnover of Jen1. Our results support an emerging concept where the cytoplasmic termini of PM transporters control transporter cell surface stability and function through flexible intramolecular interactions with each other. These findings might be extended to other MFS members to understand conserved and evolving mechanisms underlying transporter structure-function relationships. This article has an associated First Person interview with the first authors of the paper.
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Affiliation(s)
- Cláudia Barata-Antunes
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, 4710-057, Braga, Portugal.,Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, 4710-057, Braga, Portugal
| | - Gabriel Talaia
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, 4710-057, Braga, Portugal.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - George Broutzakis
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis 15784, Athens, Greece
| | - David Ribas
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, 4710-057, Braga, Portugal
| | - Pieter De Beule
- International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga s/n, Braga, Portugal
| | - Margarida Casal
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, 4710-057, Braga, Portugal.,Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, 4710-057, Braga, Portugal
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis 15784, Athens, Greece.,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, 70013, Heraklion, Greece
| | - Sandra Paiva
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, 4710-057, Braga, Portugal.,Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, 4710-057, Braga, Portugal
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7
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Chen Y, Zeng W, Yu S, Chen J, Zhou J. Gene co-expression network analysis reveals the positive impact of endocytosis and mitochondria-related genes over nitrogen metabolism in Saccharomyces cerevisiae. Gene 2022; 821:146267. [PMID: 35150821 DOI: 10.1016/j.gene.2022.146267] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 12/06/2021] [Accepted: 01/27/2022] [Indexed: 12/24/2022]
Abstract
Nitrogen metabolism is essential for most cellular activities. Therefore, a deep understanding of its regulatory mechanisms is necessary for the efficient utilization of nitrogen sources for Saccharomyces cerevisiae. In this study, a gene co-expression network was constructed for S. cerevisiae S288C with different nitrogen sources. From this, a key gene co-expression module related to nitrogen source preference utilization was obtained, and 10 hub genes centrally located in the co-expression network were identified. Functional studies verified that the endocytosis-related genes CAP1 and END3 significantly increased the utilization of multiple non-preferred amino acids and reduced the accumulation of the harmful nitrogen metabolite precursor urea by regulating amino acid transporters and TOR pathway. The mitochondria-related gene ATP12, MRPL22, MRP1 and NAM9 significantly increased the utilization of multiple non-preferred amino acids and reduced accumulation of the urea by coordinately regulating nitrogen catabolism repression, Ssy1p-Ptr3p-Ssy5p signaling sensor system, amino acid transporters, TOR pathway and urea metabolism-related pathways. Furthermore, these data revealed the potential positive effects of endocytosis and mitochondrial ribosomes protein translation on nitrogen source preference. This study provides new analytical perspectives for complex regulatory networks involving nitrogen metabolism in S. cerevisiae.
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Affiliation(s)
- Yu Chen
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Weizhu Zeng
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Shiqin Yu
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jian Chen
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jingwen Zhou
- Key Laboratory of Industrial Biotechnology, Ministry of Education and School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
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α-Arrestins and Their Functions: From Yeast to Human Health. Int J Mol Sci 2022; 23:ijms23094988. [PMID: 35563378 PMCID: PMC9105457 DOI: 10.3390/ijms23094988] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/26/2022] [Accepted: 04/27/2022] [Indexed: 12/10/2022] Open
Abstract
α-Arrestins, also called arrestin-related trafficking adaptors (ARTs), constitute a large family of proteins conserved from yeast to humans. Despite their evolutionary precedence over their extensively studied relatives of the β-arrestin family, α-arrestins have been discovered relatively recently, and thus their properties are mostly unexplored. The predominant function of α-arrestins is the selective identification of membrane proteins for ubiquitination and degradation, which is an important element in maintaining membrane protein homeostasis as well as global cellular metabolisms. Among members of the arrestin clan, only α-arrestins possess PY motifs that allow canonical binding to WW domains of Rsp5/NEDD4 ubiquitin ligases and the subsequent ubiquitination of membrane proteins leading to their vacuolar/lysosomal degradation. The molecular mechanisms of the selective substrate’s targeting, function, and regulation of α-arrestins in response to different stimuli remain incompletely understood. Several functions of α-arrestins in animal models have been recently characterized, including redox homeostasis regulation, innate immune response regulation, and tumor suppression. However, the molecular mechanisms of α-arrestin regulation and substrate interactions are mainly based on observations from the yeast Saccharomyces cerevisiae model. Nonetheless, α-arrestins have been implicated in health disorders such as diabetes, cardiovascular diseases, neurodegenerative disorders, and tumor progression, placing them in the group of potential therapeutic targets.
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Bowman RW, Jordahl EM, Davis S, Hedayati S, Barsouk H, Ozbaki-Yagan N, Chiang A, Li Y, O’Donnell AF. TORC1 Signaling Controls the Stability and Function of α-Arrestins Aly1 and Aly2. Biomolecules 2022; 12:biom12040533. [PMID: 35454122 PMCID: PMC9031309 DOI: 10.3390/biom12040533] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/22/2022] [Accepted: 03/25/2022] [Indexed: 02/06/2023] Open
Abstract
Nutrient supply dictates cell signaling changes, which in turn regulate membrane protein trafficking. To better exploit nutrients, cells relocalize membrane transporters via selective protein trafficking. Key in this reshuffling are the α-arrestins, selective protein trafficking adaptors conserved from yeast to man. α-Arrestins bind membrane proteins, controlling the ubiquitination and endocytosis of many transporters. To prevent the spurious removal of membrane proteins, α-arrestin-mediated endocytosis is kept in check through phospho-inhibition. This phospho-regulation is complex, with up to 87 phospho-sites on a single α-arrestin and many kinases/phosphatases targeting α-arrestins. To better define the signaling pathways controlling paralogous α-arrestins, Aly1 and Aly2, we screened the kinase and phosphatase deletion (KinDel) library, which is an array of all non-essential kinase and phosphatase yeast deletion strains, for modifiers of Aly-mediated phenotypes. We identified many Aly regulators, but focused our studies on the TORC1 kinase, a master regulator of nutrient signaling across eukaryotes. We found that TORC1 and its signaling effectors, the Sit4 protein phosphatase and Npr1 kinase, regulate the phosphorylation and stability of Alys. When Sit4 is lost, Alys are hyperphosphorylated and destabilized in an Npr1-dependent manner. These findings add new dimensions to our understanding of TORC1 regulation of α-arrestins and have important ramifications for cellular metabolism.
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Affiliation(s)
- Ray W. Bowman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Eric M. Jordahl
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Sydnie Davis
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Stefanie Hedayati
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Hannah Barsouk
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Nejla Ozbaki-Yagan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Annette Chiang
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
| | - Yang Li
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Allyson F. O’Donnell
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA; (R.W.B.II); (E.M.J.); (S.D.); (S.H.); (H.B.); (N.O.-Y.); (A.C.)
- Correspondence: ; Tel.: +1-412-648-4270
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10
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Moharir A, Gay L, Markus B. Mitochondrial energy metabolism regulates the nutrient import activity and endocytosis of APC transporters. FEBS Lett 2022; 596:1111-1123. [PMID: 35156710 PMCID: PMC9117475 DOI: 10.1002/1873-3468.14314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 01/30/2022] [Accepted: 02/01/2022] [Indexed: 11/11/2022]
Abstract
Nutrient import by APC-type transporters is predicted to have a high energy demand because it depends on the plasma membrane proton gradient established by the ATP-driven proton pump Pma1. We show that Pma1 is indeed a major energy consumer and its activity is tightly linked to the cellular ATP levels. The low Pma1 activity caused by acute loss of respiration resulted in a dramatic drop in cytoplasmic pH, which triggered the downregulation of the major proton importers, the APC transporters. This regulatory system is likely the reason for the observed rapid endocytosis of APC transporters during many environmental stresses. Furthermore, we show the importance of respiration in providing ATP to maintain a strong proton gradient for efficient nutrient uptake.
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Affiliation(s)
- Akshay Moharir
- Henry Eyring Center for Cell and Genome Science, University of Utah, 1390 President Circle, Salt Lake City, UT, 84112, USA
| | - Lincoln Gay
- Henry Eyring Center for Cell and Genome Science, University of Utah, 1390 President Circle, Salt Lake City, UT, 84112, USA
| | - Babst Markus
- Henry Eyring Center for Cell and Genome Science, University of Utah, 1390 President Circle, Salt Lake City, UT, 84112, USA
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11
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Robinson BP, Hawbaker S, Chiang A, Jordahl EM, Anaokar S, Nikiforov A, Bowman RW, Ziegler P, McAtee CK, Patton-Vogt J, O'Donnell AF. Alpha-arrestins Aly1/Art6 and Aly2/Art3 regulate trafficking of the glycerophosphoinositol transporter Git1 and impact phospholipid homeostasis. Biol Cell 2021; 114:3-31. [PMID: 34562280 DOI: 10.1111/boc.202100007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 06/23/2021] [Accepted: 07/15/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND INFORMATION Phosphatidylinositol (PI) is an essential phospholipid, critical to membrane bilayers. The complete deacylation of PI by B-type phospholipases produces intracellular and extracellular glycerophosphoinositol (GPI). Extracellular GPI is transported into the cell via Git1, a member of the Major Facilitator Superfamily of transporters at the yeast plasma membrane. Internalized GPI is degraded to produce inositol, phosphate and glycerol, thereby contributing to these pools. GIT1 gene expression is controlled by nutrient balance, with phosphate or inositol starvation increasing GIT1 expression to stimulate GPI uptake. However, less is known about control of Git1 protein levels or localization. RESULTS We find that the α-arrestins, an important class of protein trafficking adaptor, regulate Git1 localization and this is dependent upon their interaction with the ubiquitin ligase Rsp5. Specifically, α-arrestin Aly2 stimulates Git1 trafficking to the vacuole under basal conditions, but in response to GPI-treatment, either Aly1 or Aly2 promote Git1 vacuole trafficking. Cell surface retention of Git1, as occurs in aly1∆ aly2∆ cells, is linked to impaired growth in the presence of exogenous GPI and results in increased uptake of radiolabeled GPI, suggesting that accumulation of GPI somehow causes cellular toxicity. Regulation of α-arrestin Aly1 by the protein phosphatase calcineurin improves steady-state and substrate-induced trafficking of Git1, however, calcineurin plays a larger role in Git1 trafficking beyond regulation of α-arrestins. Interestingly, loss of Aly1 and Aly2 increased phosphatidylinositol-3-phosphate on the limiting membrane of the vacuole, and this was further exacerbated by GPI addition, suggesting that the effect is partially linked to Git1. Loss of Aly1 and Aly2 leads to increased incorporation of inositol label from [3 H]-inositol-labelled GPI into PI, confirming that internalized GPI influences PI balance and indicating a role for the a-arrestins in this regulation. CONCLUSIONS The α-arrestins Aly1 and Aly2 are novel regulators of Git1 trafficking with previously unanticipated roles in controlling phospholipid distribution and balance. SIGNIFICANCE To our knowledge, this is the first example of α-arrestin regulation of phosphatidyliniositol-3-phosphate levels. In future studies it will be exciting to determine if other α-arrestins similarly alter PI and PIPs to change the cellular landscape.
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Affiliation(s)
- Benjamin P Robinson
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Sarah Hawbaker
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Annette Chiang
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Eric M Jordahl
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sanket Anaokar
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Alexiy Nikiforov
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Ray W Bowman
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA.,Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Philip Ziegler
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Ceara K McAtee
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jana Patton-Vogt
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Allyson F O'Donnell
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA.,Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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12
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Megarioti AH, Primo C, Kapetanakis GC, Athanasopoulos A, Sophianopoulou V, André B, Gournas C. The Bul1/2 Alpha-Arrestins Promote Ubiquitylation and Endocytosis of the Can1 Permease upon Cycloheximide-Induced TORC1-Hyperactivation. Int J Mol Sci 2021; 22:10208. [PMID: 34638549 PMCID: PMC8508209 DOI: 10.3390/ijms221910208] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/15/2021] [Accepted: 09/16/2021] [Indexed: 12/12/2022] Open
Abstract
Selective endocytosis followed by degradation is a major mechanism for downregulating plasma membrane transporters in response to specific environmental cues. In Saccharomyces cerevisiae, this endocytosis is promoted by ubiquitylation catalyzed by the Rsp5 ubiquitin-ligase, targeted to transporters via adaptors of the alpha-arrestin family. However, the molecular mechanisms of this targeting and their control according to conditions remain incompletely understood. In this work, we dissect the molecular mechanisms eliciting the endocytosis of Can1, the arginine permease, in response to cycloheximide-induced TORC1 hyperactivation. We show that cycloheximide promotes Rsp5-dependent Can1 ubiquitylation and endocytosis in a manner dependent on the Bul1/2 alpha-arrestins. Also crucial for this downregulation is a short acidic patch sequence in the N-terminus of Can1 likely acting as a binding site for Bul1/2. The previously reported inhibition by cycloheximide of transporter recycling, from the trans-Golgi network to the plasma membrane, seems to additionally contribute to efficient Can1 downregulation. Our results also indicate that, contrary to the previously described substrate-transport elicited Can1 endocytosis mediated by the Art1 alpha-arrestin, Bul1/2-mediated Can1 ubiquitylation occurs independently of the conformation of the transporter. This study provides further insights into how distinct alpha-arrestins control the ubiquitin-dependent downregulation of a specific amino acid transporter under different conditions.
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Affiliation(s)
- Amalia H. Megarioti
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Patr. Grigoriou E & 27 Neapoleos St., 15341 Agia Paraskevi, Greece; (A.H.M.); (A.A.); (V.S.)
| | - Cecilia Primo
- Molecular Physiology of the Cell Laboratory, Université Libre de Bruxelles (ULB), IBMM, 6041 Gosselies, Belgium; (C.P.); (G.C.K.)
| | - George C. Kapetanakis
- Molecular Physiology of the Cell Laboratory, Université Libre de Bruxelles (ULB), IBMM, 6041 Gosselies, Belgium; (C.P.); (G.C.K.)
| | - Alexandros Athanasopoulos
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Patr. Grigoriou E & 27 Neapoleos St., 15341 Agia Paraskevi, Greece; (A.H.M.); (A.A.); (V.S.)
| | - Vicky Sophianopoulou
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Patr. Grigoriou E & 27 Neapoleos St., 15341 Agia Paraskevi, Greece; (A.H.M.); (A.A.); (V.S.)
| | - Bruno André
- Molecular Physiology of the Cell Laboratory, Université Libre de Bruxelles (ULB), IBMM, 6041 Gosselies, Belgium; (C.P.); (G.C.K.)
| | - Christos Gournas
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Patr. Grigoriou E & 27 Neapoleos St., 15341 Agia Paraskevi, Greece; (A.H.M.); (A.A.); (V.S.)
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13
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Arines FM, Hamlin AJ, Yang X, Liu YYJ, Li M. A selective transmembrane recognition mechanism by a membrane-anchored ubiquitin ligase adaptor. J Cell Biol 2021; 220:211632. [PMID: 33351099 PMCID: PMC7759299 DOI: 10.1083/jcb.202001116] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 09/10/2020] [Accepted: 10/30/2020] [Indexed: 12/30/2022] Open
Abstract
While it is well-known that E3 ubiquitin ligases can selectively ubiquitinate membrane proteins in response to specific environmental cues, the underlying mechanisms for the selectivity are poorly understood. In particular, the role of transmembrane regions, if any, in target recognition remains an open question. Here, we describe how Ssh4, a yeast E3 ligase adaptor, recognizes the PQ-loop lysine transporter Ypq1 only after lysine starvation. We show evidence of an interaction between two transmembrane helices of Ypq1 (TM5 and TM7) and the single transmembrane helix of Ssh4. This interaction is regulated by the conserved PQ motif. Strikingly, recent structural studies of the PQ-loop family have suggested that TM5 and TM7 undergo major conformational changes during substrate transport, implying that transport-associated conformational changes may determine the selectivity. These findings thus provide critical information concerning the regulatory mechanism through which transmembrane domains can be specifically recognized in response to changing environmental conditions.
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Affiliation(s)
- Felichi Mae Arines
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Aaron Jeremy Hamlin
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Xi Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Yun-Yu Jennifer Liu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Ming Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
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14
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Endocytosis of nutrient transporters in fungi: The ART of connecting signaling and trafficking. Comput Struct Biotechnol J 2021; 19:1713-1737. [PMID: 33897977 PMCID: PMC8050425 DOI: 10.1016/j.csbj.2021.03.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 03/14/2021] [Accepted: 03/14/2021] [Indexed: 12/11/2022] Open
Abstract
Plasma membrane transporters play pivotal roles in the import of nutrients, including sugars, amino acids, nucleobases, carboxylic acids, and metal ions, that surround fungal cells. The selective removal of these transporters by endocytosis is one of the most important regulatory mechanisms that ensures a rapid adaptation of cells to the changing environment (e.g., nutrient fluctuations or different stresses). At the heart of this mechanism lies a network of proteins that includes the arrestin‐related trafficking adaptors (ARTs) which link the ubiquitin ligase Rsp5 to nutrient transporters and endocytic factors. Transporter conformational changes, as well as dynamic interactions between its cytosolic termini/loops and with lipids of the plasma membrane, are also critical during the endocytic process. Here, we review the current knowledge and recent findings on the molecular mechanisms involved in nutrient transporter endocytosis, both in the budding yeast Saccharomyces cerevisiae and in some species of the filamentous fungus Aspergillus. We elaborate on the physiological importance of tightly regulated endocytosis for cellular fitness under dynamic conditions found in nature and highlight how further understanding and engineering of this process is essential to maximize titer, rate and yield (TRY)-values of engineered cell factories in industrial biotechnological processes.
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Key Words
- AAs, amino acids
- ACT, amino Acid/Choline Transporter
- AP, adaptor protein
- APC, amino acid-polyamine-organocation
- Arg, arginine
- Arrestins
- Arts, arrestin‐related trafficking adaptors
- Asp, aspartic acid
- Aspergilli
- Biotechnology
- C, carbon
- C-terminus, carboxyl-terminus
- Cell factories
- Conformational changes
- Cu, copper
- DUBs, deubiquitinating enzymes
- EMCs, eisosome membrane compartments
- ER, endoplasmic reticulum
- ESCRT, endosomal sorting complex required for transport
- Endocytic signals
- Endocytosis
- Fe, iron
- Fungi
- GAAC, general amino acid control
- Glu, glutamic acid
- H+, proton
- IF, inward-facing
- LAT, L-type Amino acid Transporter
- LID, loop Interaction Domain
- Lys, lysine
- MCCs, membrane compartments containing the arginine permease Can1
- MCCs/eisosomes
- MCPs, membrane compartments of Pma1
- MFS, major facilitator superfamily
- MVB, multi vesicular bodies
- Met, methionine
- Metabolism
- Mn, manganese
- N, nitrogen
- N-terminus, amino-terminus
- NAT, nucleobase Ascorbate Transporter
- NCS1, nucleobase/Cation Symporter 1
- NCS2, nucleobase cation symporter family 2
- NH4+, ammonium
- Nutrient transporters
- OF, outward-facing
- PEST, proline (P), glutamic acid (E), serine (S), and threonine (T)
- PM, plasma membrane
- PVE, prevacuolar endosome
- Saccharomyces cerevisiae
- Signaling pathways
- Structure-function
- TGN, trans-Golgi network
- TMSs, transmembrane segments
- TORC1, target of rapamycin complex 1
- TRY, titer, rate and yield
- Trp, tryptophan
- Tyr, tyrosine
- Ub, ubiquitin
- Ubiquitylation
- VPS, vacuolar protein sorting
- W/V, weight per volume
- YAT, yeast Amino acid Transporter
- Zn, Zinc
- fAATs, fungal AA transporters
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15
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Kahlhofer J, Leon S, Teis D, Schmidt O. The α-arrestin family of ubiquitin ligase adaptors links metabolism with selective endocytosis. Biol Cell 2021; 113:183-219. [PMID: 33314196 DOI: 10.1111/boc.202000137] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022]
Abstract
The regulation of nutrient uptake into cells is important, as it allows to either increase biomass for cell growth or to preserve homoeostasis. A key strategy to adjust cellular nutrient uptake is the reconfiguration of the nutrient transporter repertoire at the plasma membrane by the addition of nutrient transporters through the secretory pathway and by their endocytic removal. In this review, we focus on the mechanisms that regulate selective nutrient transporter endocytosis, which is mediated by the α-arrestin protein family. In the budding yeast Saccharomyces cerevisiae, 14 different α-arrestins (also named arrestin-related trafficking adaptors, ARTs) function as adaptors for the ubiquitin ligase Rsp5. They instruct Rsp5 to ubiquitinate subsets of nutrient transporters to orchestrate their endocytosis. The ART proteins are under multilevel control of the major nutrient sensing systems, including amino acid sensing by the general amino acid control and target of rapamycin pathways, and energy sensing by 5'-adenosine-monophosphate-dependent kinase. The function of the six human α-arrestins is comparably under-characterised. Here, we summarise the current knowledge about the function, regulation and substrates of yeast ARTs and human α-arrestins, and highlight emerging communalities and general principles.
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Affiliation(s)
- Jennifer Kahlhofer
- Institute for Cell Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Sebastien Leon
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - David Teis
- Institute for Cell Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
| | - Oliver Schmidt
- Institute for Cell Biology, Biocenter, Medical University Innsbruck, Innsbruck, Austria
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16
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Sardana R, Emr SD. Membrane Protein Quality Control Mechanisms in the Endo-Lysosome System. Trends Cell Biol 2021; 31:269-283. [PMID: 33414051 DOI: 10.1016/j.tcb.2020.11.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/26/2020] [Accepted: 11/30/2020] [Indexed: 01/12/2023]
Abstract
Protein quality control (PQC) machineries play a critical role in selective identification and removal of mistargeted, misfolded, and aberrant proteins. This task is extremely complicated due to the enormous diversity of the proteome. It also requires nuanced and careful differentiation between 'normal' and 'folding intermediates' from 'abnormal' and 'misfolded' protein states. Multiple genetic and proteomic approaches have started to delineate the molecular underpinnings of how these machineries recognize their target and how their activity is regulated. In this review, we summarize our understanding of the various E3 ubiquitin ligases and associated machinery that mediate PQC in the endo-lysosome system in yeast and humans, how they are regulated, and mechanisms of target selection, with the intent of guiding future research in this area.
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Affiliation(s)
- Richa Sardana
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, NY, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Scott D Emr
- Weill Institute of Cell and Molecular Biology, Cornell University, Ithaca, NY, USA; Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA.
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17
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Tanahashi R, Afiah TSN, Nishimura A, Watanabe D, Takagi H. The C2 domain of the ubiquitin ligase Rsp5 is required for ubiquitination of the endocytic protein Rvs167 upon change of nitrogen source. FEMS Yeast Res 2020; 20:5986617. [PMID: 33201982 DOI: 10.1093/femsyr/foaa058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 10/16/2020] [Indexed: 12/26/2022] Open
Abstract
Ubiquitination is a key signal for endocytosis of proteins on the plasma membrane. The ubiquitin ligase Rsp5 of Saccharomyces cerevisiae, which contains an amino-terminal membrane-binding C2 domain, three substrate-recognizing tryptophan-tryptophan (WW) domains and a carboxyl-terminal catalytic homologous to the E6-AP carboxyl terminus (HECT) domain, can ubiquitinate plasma membrane proteins directing them for endocytosis. Here, we examined the roles of the C2 domain in endocytosis for the downregulation of the general amino acid permease Gap1, which is one of nitrogen-regulated permeases in S. cerevisiae. First, we constructed several rsp5 mutants producing Rsp5 variants without the C2 domain or with amino acid changes of membrane-binding lysine residues. These mutants showed defects in endocytosis of Gap1 in response to a preferred nitrogen source. Intriguingly, we found that ubiquitination of Gap1 in these mutant cells was highly similar to that in wild-type cells during endocytosis. These results indicate that the C2 domain is essential for endocytosis but not for ubiquitination of substrates such as Gap1. Moreover, genetic and biochemical analyses showed that the endocytic protein Rvs167 was ubiquitinated via Rsp5 and the C2 domain was required for efficient ubiquitination in response to a preferred nitrogen source. Here, we propose a mechanism for the C2 domain-mediated endocytosis of plasma membrane permeases.
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Affiliation(s)
- Ryoya Tanahashi
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
| | - Tira Siti Nur Afiah
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
| | - Akira Nishimura
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
| | - Daisuke Watanabe
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
| | - Hiroshi Takagi
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan
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18
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Ivashov V, Zimmer J, Schwabl S, Kahlhofer J, Weys S, Gstir R, Jakschitz T, Kremser L, Bonn GK, Lindner H, Huber LA, Leon S, Schmidt O, Teis D. Complementary α-arrestin-ubiquitin ligase complexes control nutrient transporter endocytosis in response to amino acids. eLife 2020; 9:e58246. [PMID: 32744498 PMCID: PMC7449699 DOI: 10.7554/elife.58246] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 08/01/2020] [Indexed: 12/12/2022] Open
Abstract
How cells adjust nutrient transport across their membranes is incompletely understood. Previously, we have shown that S. cerevisiae broadly re-configures the nutrient transporters at the plasma membrane in response to amino acid availability, through endocytosis of sugar- and amino acid transporters (AATs) (Müller et al., 2015). A genome-wide screen now revealed that the selective endocytosis of four AATs during starvation required the α-arrestin family protein Art2/Ecm21, an adaptor for the ubiquitin ligase Rsp5, and its induction through the general amino acid control pathway. Art2 uses a basic patch to recognize C-terminal acidic sorting motifs in AATs and thereby instructs Rsp5 to ubiquitinate proximal lysine residues. When amino acids are in excess, Rsp5 instead uses TORC1-activated Art1 to detect N-terminal acidic sorting motifs within the same AATs, which initiates exclusive substrate-induced endocytosis. Thus, amino acid excess or starvation activate complementary α-arrestin-Rsp5-complexes to control selective endocytosis and adapt nutrient acquisition.
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Affiliation(s)
- Vasyl Ivashov
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - Johannes Zimmer
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - Sinead Schwabl
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - Jennifer Kahlhofer
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - Sabine Weys
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - Ronald Gstir
- ADSI – Austrian Drug Screening Institute GmbHInnsbruckAustria
| | | | - Leopold Kremser
- Division of Clinical Biochemistry, ProteinMicroAnalysis Facility, Medical University of InnsbruckInnsbruckAustria
| | - Günther K Bonn
- ADSI – Austrian Drug Screening Institute GmbHInnsbruckAustria
| | - Herbert Lindner
- Division of Clinical Biochemistry, ProteinMicroAnalysis Facility, Medical University of InnsbruckInnsbruckAustria
| | - Lukas A Huber
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
- ADSI – Austrian Drug Screening Institute GmbHInnsbruckAustria
| | - Sebastien Leon
- Université de Paris, CNRS, Institut Jacques MonodParisFrance
| | - Oliver Schmidt
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
| | - David Teis
- Institute for Cell Biology, Medical University of InnsbruckInnsbruckAustria
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19
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Dimou S, Diallinas G. Life and Death of Fungal Transporters under the Challenge of Polarity. Int J Mol Sci 2020; 21:ijms21155376. [PMID: 32751072 PMCID: PMC7432044 DOI: 10.3390/ijms21155376] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/24/2020] [Accepted: 07/27/2020] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic plasma membrane (PM) transporters face critical challenges that are not widely present in prokaryotes. The two most important issues are proper subcellular traffic and targeting to the PM, and regulated endocytosis in response to physiological, developmental, or stress signals. Sorting of transporters from their site of synthesis, the endoplasmic reticulum (ER), to the PM has been long thought, but not formally shown, to occur via the conventional Golgi-dependent vesicular secretory pathway. Endocytosis of specific eukaryotic transporters has been studied more systematically and shown to involve ubiquitination, internalization, and sorting to early endosomes, followed by turnover in the multivesicular bodies (MVB)/lysosomes/vacuole system. In specific cases, internalized transporters have been shown to recycle back to the PM. However, the mechanisms of transporter forward trafficking and turnover have been overturned recently through systematic work in the model fungus Aspergillus nidulans. In this review, we present evidence that shows that transporter traffic to the PM takes place through Golgi bypass and transporter endocytosis operates via a mechanism that is distinct from that of recycling membrane cargoes essential for fungal growth. We discuss these findings in relation to adaptation to challenges imposed by cell polarity in fungi as well as in other eukaryotes and provide a rationale of why transporters and possibly other housekeeping membrane proteins ‘avoid’ routes of polar trafficking.
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20
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Athanasopoulos A, André B, Sophianopoulou V, Gournas C. Fungal plasma membrane domains. FEMS Microbiol Rev 2020; 43:642-673. [PMID: 31504467 DOI: 10.1093/femsre/fuz022] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/25/2019] [Indexed: 12/11/2022] Open
Abstract
The plasma membrane (PM) performs a plethora of physiological processes, the coordination of which requires spatial and temporal organization into specialized domains of different sizes, stability, protein/lipid composition and overall architecture. Compartmentalization of the PM has been particularly well studied in the yeast Saccharomyces cerevisiae, where five non-overlapping domains have been described: The Membrane Compartments containing the arginine permease Can1 (MCC), the H+-ATPase Pma1 (MCP), the TORC2 kinase (MCT), the sterol transporters Ltc3/4 (MCL), and the cell wall stress mechanosensor Wsc1 (MCW). Additional cortical foci at the fungal PM are the sites where clathrin-dependent endocytosis occurs, the sites where the external pH sensing complex PAL/Rim localizes, and sterol-rich domains found in apically grown regions of fungal membranes. In this review, we summarize knowledge from several fungal species regarding the organization of the lateral PM segregation. We discuss the mechanisms of formation of these domains, and the mechanisms of partitioning of proteins there. Finally, we discuss the physiological roles of the best-known membrane compartments, including the regulation of membrane and cell wall homeostasis, apical growth of fungal cells and the newly emerging role of MCCs as starvation-protective membrane domains.
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Affiliation(s)
- Alexandros Athanasopoulos
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Bruno André
- Molecular Physiology of the Cell laboratory, Université Libre de Bruxelles (ULB), Institut de Biologie et de Médecine Moléculaires, rue des Pr Jeener et Brachet 12, 6041, Gosselies, Belgium
| | - Vicky Sophianopoulou
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Christos Gournas
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
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21
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Lawrie RD, Mitchell RD, Dhammi A, Wallace A, Hodgson E, Roe RM. Role of long non-coding RNA in DEET- and fipronil-mediated alteration of transcripts associated with Phase I and Phase II xenobiotic metabolism in human primary hepatocytes. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2020; 167:104607. [PMID: 32527422 DOI: 10.1016/j.pestbp.2020.104607] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 05/07/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
Human exposure to environmental chemicals both individually and in combination occurs frequently world-wide most often with unknown consequences. Use of molecular approaches to aide in the assessment of risk involved in chemical exposure is a growing field in toxicology. In this study, we examined the impact of two environmental chemicals used in and around homes, the insect repellent DEET (N,N-diethyl-m-toluamide) and the phenylpyrazole insecticide fipronil (fluocyanobenpyrazole) on transcript levels of enzymes potentially involved in xenobiotic metabolism and on long non-coding RNAs (lncRNAs). Primary human hepatocytes were treated with these two chemicals both individually and in combination. Using RNA-Seq, we found that 10 major enzyme categories involved in phase 1 and phase 2 xenobiotic metabolism were significantly (α = 0.05) up- and down-regulated (i.e., 100 μM DEET-19 transcripts, 89% up and 11% down; 10 μM fipronil-52 transcripts, 53% up and 47% down; and 100 μM DEET +10 μM fipronil-69 transcripts, 43% up and 57% down). The altered genes were then mapped to the human genome and their proximity (within 1,000,000 bp) to lncRNAs examined. Unique proximities were discovered between altered lncRNA and altered P450s (CYP) and other enzymes (DEET, 2 CYP; Fipronil, 6 CYP and 15 other; and DEET + fipronil, 7 CYP and 21 other). Many of the altered P450 transcripts were in multiple clusters in the genome with proximal altered lncRNAs, suggesting a regulator function for the lncRNA. At the gene level there was high percent identity for lncRNAs near P450 clusters, but this relationship was not found at the transcript level. The role of these altered lncRNAs associated with xenobiotic induction, human diseases and chemical mixtures is discussed.
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Affiliation(s)
- Roger D Lawrie
- Toxicology Program, Department of Biology, North Carolina State University, Raleigh, NC 27695, USA; Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA
| | - Robert D Mitchell
- Toxicology Program, Department of Biology, North Carolina State University, Raleigh, NC 27695, USA; United States Department of Agriculture, Agricultural Research Service, U.S. Livestock Insects Research Lab, Kerrville, TX 78028, USA
| | - Anirudh Dhammi
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA
| | - Andrew Wallace
- Toxicology Program, Department of Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - Ernest Hodgson
- Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695, USA
| | - R Michael Roe
- Toxicology Program, Department of Biology, North Carolina State University, Raleigh, NC 27695, USA; Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA.
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22
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Babst M. Regulation of nutrient transporters by metabolic and environmental stresses. Curr Opin Cell Biol 2020; 65:35-41. [PMID: 32200208 DOI: 10.1016/j.ceb.2020.02.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 02/15/2020] [Indexed: 12/17/2022]
Abstract
The yeast plasma membrane is a selective barrier between an erratic environment and the cell's metabolism. Nutrient transporters are the gatekeepers that control the import of molecules feeding into the metabolic pathways. Nutrient import adjusts rapidly to changes in metabolism and the environment, which is accomplished by regulating the surface expression of transporters. Recent studies indicate that the lipid environment in which transporters function regulates ubiquitination efficiency and endocytosis of these proteins. Changes in the lipid environment are caused by lateral movements of the transporters between different membrane domains and by the influence of the extracellular environment on the fluidity of the plasma membrane.
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Affiliation(s)
- Markus Babst
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112, USA.
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23
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Yeast α-arrestin Art2 is the key regulator of ubiquitylation-dependent endocytosis of plasma membrane vitamin B1 transporters. PLoS Biol 2019; 17:e3000512. [PMID: 31658248 PMCID: PMC6837554 DOI: 10.1371/journal.pbio.3000512] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 11/07/2019] [Accepted: 10/09/2019] [Indexed: 11/19/2022] Open
Abstract
Endocytosis of membrane proteins in yeast requires α-arrestin-mediated ubiquitylation by the ubiquitin ligase Rsp5. Yet, the diversity of α-arrestin targets studied is restricted to a small subset of plasma membrane (PM) proteins. Here, we performed quantitative proteomics to identify new targets of 12 α-arrestins and gained insight into the diversity of pathways affected by α-arrestins, including the cell wall integrity pathway and PM–endoplasmic reticulum contact sites. We found that Art2 is the main regulator of substrate- and stress-induced ubiquitylation and endocytosis of the thiamine (vitamin B1) transporters: Thi7, nicotinamide riboside transporter 1 (Nrt1), and Thi72. Genetic screening allowed for the isolation of transport-defective Thi7 mutants, which impaired thiamine-induced endocytosis. Coexpression of inactive mutants with wild-type Thi7 revealed that both transporter conformation and transport activity are important to induce endocytosis. Finally, we provide evidence that Art2 mediated Thi7 endocytosis is regulated by the target of rapamycin complex 1 (TORC1) and requires the Sit4 phosphatase but is not inhibited by the Npr1 kinase. A combination of proteomics, protein modeling, and molecular biology sheds light on how endocytosis of the plasma membrane vitamin B1 transporter Thi7 in yeast is regulated by the α-arrestin Art2.
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Diallinas G, Martzoukou O. Transporter membrane traffic and function: lessons from a mould. FEBS J 2019; 286:4861-4875. [DOI: 10.1111/febs.15078] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/26/2019] [Accepted: 09/30/2019] [Indexed: 12/16/2022]
Affiliation(s)
- George Diallinas
- Department of Biology National and Kapodistrian University of Athens Greece
| | - Olga Martzoukou
- Department of Biology National and Kapodistrian University of Athens Greece
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25
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Ishii A, Kurokawa K, Hotta M, Yoshizaki S, Kurita M, Koyama A, Nakano A, Kimura Y. Role of Atg8 in the regulation of vacuolar membrane invagination. Sci Rep 2019; 9:14828. [PMID: 31616012 PMCID: PMC6794316 DOI: 10.1038/s41598-019-51254-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 09/26/2019] [Indexed: 01/23/2023] Open
Abstract
Cellular heat stress can cause damage, and significant changes, to a variety of cellular structures. When exposed to chronically high temperatures, yeast cells invaginate vacuolar membranes. In this study, we found that the expression of Atg8, an essential autophagy factor, is induced after chronic heat stress. In addition, without Atg8, vacuolar invaginations are induced conspicuously, beginning earlier and invaginating vacuoles more frequently after heat stress. Our results indicate that Atg8's invagination-suppressing functions do not require Atg8 lipidation, in contrast with autophagy, which requires Atg8 lipidation. Genetic analyses of vps24 and vps23 further suggest that full ESCRT machinery is necessary to form vacuolar invaginations irrespective of Atg8. In contrast, through a combined mutation with the vacuole BAR domain protein Ivy1, vacuoles show constitutively enhanced invaginated structures. Finally, we found that the atg8Δivy1Δ mutant is sensitive against agents targeting functions of the vacuole and/or plasma membrane (cell wall). Collectively, our findings revealed that Atg8 maintains vacuolar membrane homeostasis in an autophagy-independent function by coordinating with other cellular factors.
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Affiliation(s)
- Ayane Ishii
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Kazuo Kurokawa
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama, 351-0198, Japan
| | - Miyuu Hotta
- Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Suzuka Yoshizaki
- Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Maki Kurita
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Aya Koyama
- Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Akihiko Nakano
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama, 351-0198, Japan
| | - Yoko Kimura
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan. .,Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan.
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26
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Cytosolic N- and C-Termini of the Aspergillus nidulans FurE Transporter Contain Distinct Elements that Regulate by Long-Range Effects Function and Specificity. J Mol Biol 2019; 431:3827-3844. [DOI: 10.1016/j.jmb.2019.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 07/04/2019] [Accepted: 07/04/2019] [Indexed: 01/05/2023]
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Abstract
Cell nutrition, detoxification, signalling, homeostasis and response to drugs, processes related to cell growth, differentiation and survival are all mediated by plasma membrane (PM) proteins called transporters. Despite their distinct fine structures, mechanism of function, energetic requirements, kinetics and substrate specificities, all transporters are characterized by a main hydrophobic body embedded in the PM as a series of tightly packed, often intertwined, α-helices that traverse the lipid bilayer in a zigzag mode, connected with intracellular or extracellular loops and hydrophilic N- and C-termini. Whereas longstanding genetic, biochemical and biophysical evidence suggests that specific transmembrane segments, and also their connecting loops, are responsible for substrate recognition and transport dynamics, emerging evidence also reveals the functional importance of transporter N- and C-termini, in respect to transport catalysis, substrate specificity, subcellular expression, stability and signalling. This review highlights selected prototypic examples of transporters in which their termini play important roles in their functioning.
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Affiliation(s)
- Emmanuel Mikros
- Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis, 15771 Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15781 Athens, Greece
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28
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Babst M. Eisosomes at the intersection of TORC1 and TORC2 regulation. Traffic 2019; 20:543-551. [PMID: 31038844 DOI: 10.1111/tra.12651] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 12/14/2022]
Abstract
Eisosomes are furrows in the yeast plasma membrane that form a membrane domain with distinct lipid and protein composition. Recent studies highlighted the importance of this domain for the regulation of proton-nutrient symporters. The amino acids and other nutrients, which these transporters deliver to the cytoplasm not only feed into metabolic pathways but also activate the metabolic regulator TORC1. Eisosomes have also been shown to harbor the membrane stress sensors Slm1 and Slm2. Membrane tension caused by hypoosmotic shock results in the redistribution of Slm1/2 from eisosomes to TORC2 which in turn regulates lipid synthesis. Therefore, eisosomes function upstream of both TORC1 and TORC2 regulation.
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Affiliation(s)
- Markus Babst
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, Utah
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29
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Wawrzycka D, Sadlak J, Maciaszczyk-Dziubinska E, Wysocki R. Rsp5-dependent endocytosis and degradation of the arsenite transporter Acr3 requires its N-terminal acidic tail as an endocytic sorting signal and arrestin-related ubiquitin-ligase adaptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:916-925. [PMID: 30776335 DOI: 10.1016/j.bbamem.2019.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 02/06/2019] [Accepted: 02/11/2019] [Indexed: 01/15/2023]
Abstract
The yeast plasma membrane transporter Acr3 mediates efflux of toxic arsenite and antimonite. Here, we investigated the mechanisms of Acr3 turnover. We found that after arrival and residence at the plasma membrane, Acr3 is subjected to internalization followed by proteolysis in the vacuole. Endocytic degradation of Acr3 is promoted by the ubiquitin ligase Rsp5 and requires polyubiquitination of Acr3 at multiple lysine residues via lysine 63-linked ubiquitin chains. The turnover of Acr3 also depends on two arrestin-related proteins, Art3/Aly2 and Art4/Rod1, that enable recruitment of Rsp5 to its targets. Finally, we found that a short acidic patch located in the N-terminal tail of Acr3 is needed for its ubiquitination and internalization. We propose that this motif serves as an endocytic signal that facilitates binding of the arrestin-Rsp5 complexes to the Acr3 cargo.
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Affiliation(s)
- Donata Wawrzycka
- Institute of Experimental Biology, University of Wroclaw, 50-328 Wroclaw, Poland
| | - Joanna Sadlak
- Institute of Experimental Biology, University of Wroclaw, 50-328 Wroclaw, Poland
| | | | - Robert Wysocki
- Institute of Experimental Biology, University of Wroclaw, 50-328 Wroclaw, Poland.
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30
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AMPK-Mediated Regulation of Alpha-Arrestins and Protein Trafficking. Int J Mol Sci 2019; 20:ijms20030515. [PMID: 30691068 PMCID: PMC6387238 DOI: 10.3390/ijms20030515] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 01/17/2019] [Accepted: 01/17/2019] [Indexed: 12/18/2022] Open
Abstract
The adenosine monophosphate-activated protein kinase (AMPK) plays a central role in the regulation of cellular metabolism. Recent studies reveal a novel role for AMPK in the regulation of glucose and other carbohydrates flux by controlling the endocytosis of transporters. The first step in glucose metabolism is glucose uptake, a process mediated by members of the GLUT/SLC2A (glucose transporters) or HXT (hexose transporters) family of twelve-transmembrane domain glucose transporters in mammals and yeast, respectively. These proteins are conserved from yeast to humans, and multiple transporters—each with distinct kinetic properties—compete for plasma membrane occupancy in order to enhance or limit the rate of glucose uptake. During growth in the presence of alternative carbon sources, glucose transporters are removed and replaced with the appropriate transporter to help support growth in response to this environment. New insights into the regulated protein trafficking of these transporters reveal the requirement for specific α-arrestins, a little-studied class of protein trafficking adaptor. A defining feature of the α-arrestins is that each contains PY-motifs, which can bind to the ubiquitin ligases from the NEDD4/Rsp5 (Neural precursor cell Expressed, Developmentally Down-regulated 4 and Reverses Spt- Phenotype 5, respectively) family. Specific association of α-arrestins with glucose and carbohydrate transporters is thought to bring the ubiquitin ligase in close proximity to its membrane substrate, and thereby allows the membrane cargo to become ubiquitinated. This ubiquitination in turn serves as a mark to stimulate endocytosis. Recent results show that AMPK phosphorylation of the α-arrestins impacts their abundance and/or ability to stimulate carbohydrate transporter endocytosis. Indeed, AMPK or glucose limitation also controls α-arrestin gene expression, adding an additional layer of complexity to this regulation. Here, we review the recent studies that have expanded the role of AMPK in cellular metabolism to include regulation of α-arrestin-mediated trafficking of transporters and show that this mechanism of regulation is conserved over the ~150 million years of evolution that separate yeast from man.
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31
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Investigation of Ldb19/Art1 localization and function at the late Golgi. PLoS One 2018; 13:e0206944. [PMID: 30403748 PMCID: PMC6221343 DOI: 10.1371/journal.pone.0206944] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 10/22/2018] [Indexed: 12/21/2022] Open
Abstract
The arrestin-related family of proteins (ARTs) are potent regulators of membrane traffic at multiple cellular locations in the yeast Saccharomyces cerevisiae. Several ARTs act at multiple locations, suggesting that ARTs with well-established functions at one location may have additional, as of yet, uncharacterized roles at other locations in the cell. To more fully understand the spectrum of cellular functions regulated by ART proteins, we explored the localization and function of Ldb19/Art1, which has previously been shown to function at the plasma membrane, yet is reported to localize to the trans-Golgi network (TGN). We report that the C-terminal fusion of Ldb19 with GFP is functional and, as previously reported, localizes to the TGN. We further establish that Ldb19 associates with late stages of TGN maturation that are enriched in the clathrin adaptor protein complex-1 (AP-1). Additionally, we present genetic interaction assays that suggest Ldb19 acts at the late TGN in a mechanism related to that of AP-1. However, Ldb19 and AP-1 have dissimilar phenotypes in a subset of assays of membrane traffic, suggesting Ldb19 functions at the TGN are distinct from those of AP-1. Together these results indicate Ldb19 functions at the TGN, in addition to its well-established role in endocytosis.
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32
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Yu SC, Kuemmel F, Skoufou-Papoutsaki MN, Spanu PD. Yeast transformation efficiency is enhanced by TORC1- and eisosome-dependent signaling. Microbiologyopen 2018; 8:e00730. [PMID: 30311441 PMCID: PMC6528558 DOI: 10.1002/mbo3.730] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 08/09/2018] [Accepted: 08/10/2018] [Indexed: 12/12/2022] Open
Abstract
Transformation of baker's yeast (Saccharomyces cerevisiae) plays a key role in several experimental techniques, yet the molecular mechanisms underpinning transformation are still unclear. The addition of amino acids to the growth and transformation medium increases transformation efficiency. Here, we show that target of rapamycin complex 1 (TORC1) activated by amino acids enhances transformation via ubiquitin‐mediated endocytosis. We created mutants of the TORC1 pathway, alpha‐arrestins, and eisosome‐related genes. Our results demonstrate that the TORC1‐Npr1‐Art1/Rsp5 pathway regulates yeast transformation. Based on our previous study, activation of this pathway results in up to a 200‐fold increase in transformation efficiency, or greater. Additionally, we suggest DNA may be taken up by domains at the membrane compartment of Can1 (MCC) in the plasma membrane formed by eisosomes. Yeast studies on transformation could be used as a platform to understand the mechanism of DNA uptake in mammalian systems, which is clinically relevant to optimize gene therapy.
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Affiliation(s)
- Sheng-Chun Yu
- Department of Life Sciences, Imperial College London, London, UK
| | - Florian Kuemmel
- Department of Life Sciences, Imperial College London, London, UK
| | | | - Pietro D Spanu
- Department of Life Sciences, Imperial College London, London, UK
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33
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Deletion of the GCW13 gene derepresses Gap1-dependent uptake of amino acids in Pichia pastoris grown on methanol as the sole carbon source. Biochem Biophys Res Commun 2018; 501:226-231. [PMID: 29733846 DOI: 10.1016/j.bbrc.2018.04.221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 04/27/2018] [Indexed: 11/23/2022]
Abstract
In Pichia pastoris, most of the Glycosylphosphatidylinositol (GPI)-anchored proteins are of unknown function. Gcw13, one of these GPI-anchored proteins, was found to exert an inhibitory effect on the growth of the histidine auxotrophic P. pastoris strain GS115 on methanol as the sole carbon source. To investigate the biological function of Gcw13, RNA sequencing (RNA-Seq) was performed to compare the difference of gene expression between GS115 and GCW13-deletion strain D13. RNA-Seq analysis showed that, in strain D13, the expression of genes involved in the methanol utilization pathway or peroxisome biogenesis was not changed, and a high proportion of genes involved in the biosynthesis of amino acids were down-regulated, whereas GAP1, which encodes a general amino acid permease, was significantly up-regulated. Besides, the intracellular concentrations of various amino acids were significantly higher in D13 than that in GS115. We also observed that deletion of GCW13 resulted in more Gap1 presented on the cell surface and more active uptake of the toxic proline analogue l-azetidine-2-carboxylate acid (AzC). These results suggest that Gcw13 suppresses the expression of GAP1 and facilitates the endocytosis of Gap1 on methanol, resulting in decreasing Gap1-dependent uptake of amino acids in P. pastoris, which might contribute to the poor growth of GS115 on methanol.
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34
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Hager NA, Krasowski CJ, Mackie TD, Kolb AR, Needham PG, Augustine AA, Dempsey A, Szent-Gyorgyi C, Bruchez MP, Bain DJ, Kwiatkowski AV, O'Donnell AF, Brodsky JL. Select α-arrestins control cell-surface abundance of the mammalian Kir2.1 potassium channel in a yeast model. J Biol Chem 2018; 293:11006-11021. [PMID: 29784874 DOI: 10.1074/jbc.ra117.001293] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/04/2018] [Indexed: 12/16/2022] Open
Abstract
Protein composition at the plasma membrane is tightly regulated, with rapid protein internalization and selective targeting to the cell surface occurring in response to environmental changes. For example, ion channels are dynamically relocalized to or from the plasma membrane in response to physiological alterations, allowing cells and organisms to maintain osmotic and salt homeostasis. To identify additional factors that regulate the selective trafficking of a specific ion channel, we used a yeast model for a mammalian potassium channel, the K+ inward rectifying channel Kir2.1. Kir2.1 maintains potassium homeostasis in heart muscle cells, and Kir2.1 defects lead to human disease. By examining the ability of Kir2.1 to rescue the growth of yeast cells lacking endogenous potassium channels, we discovered that specific α-arrestins regulate Kir2.1 localization. Specifically, we found that the Ldb19/Art1, Aly1/Art6, and Aly2/Art3 α-arrestin adaptor proteins promote Kir2.1 trafficking to the cell surface, increase Kir2.1 activity at the plasma membrane, and raise intracellular potassium levels. To better quantify the intracellular and cell-surface populations of Kir2.1, we created fluorogen-activating protein fusions and for the first time used this technique to measure the cell-surface residency of a plasma membrane protein in yeast. Our experiments revealed that two α-arrestin effectors also control Kir2.1 localization. In particular, both the Rsp5 ubiquitin ligase and the protein phosphatase calcineurin facilitated the α-arrestin-mediated trafficking of Kir2.1. Together, our findings implicate α-arrestins in regulating an additional class of plasma membrane proteins and establish a new tool for dissecting the trafficking itinerary of any membrane protein in yeast.
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Affiliation(s)
- Natalie A Hager
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Collin J Krasowski
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Timothy D Mackie
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Alexander R Kolb
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Patrick G Needham
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Andrew A Augustine
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Alison Dempsey
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Christopher Szent-Gyorgyi
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Marcel P Bruchez
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Daniel J Bain
- the Department of Geology and Environmental Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and
| | - Adam V Kwiatkowski
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Allyson F O'Donnell
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282,
| | - Jeffrey L Brodsky
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260,
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35
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Conrad M, Kankipati HN, Kimpe M, Van Zeebroeck G, Zhang Z, Thevelein JM. The nutrient transceptor/PKA pathway functions independently of TOR and responds to leucine and Gcn2 in a TOR-independent manner. FEMS Yeast Res 2018; 17:3950251. [PMID: 28810702 PMCID: PMC5812495 DOI: 10.1093/femsyr/fox048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 07/06/2017] [Indexed: 12/25/2022] Open
Abstract
Two nutrient-controlled signalling pathways, the PKA and TOR pathway, play a major role in nutrient regulation of growth as well as growth-correlated properties in yeast. The relationship between the two pathways is not well understood. We have used Gap1 and Pho84 transceptor-mediated activation of trehalase and phosphorylation of fragmented Sch9 as a read-out for rapid nutrient activation of PKA or TORC1, respectively. We have identified conditions in which L-citrulline-induced activation of Sch9 phosphorylation is compromised, but not activation of trehalase: addition of the TORC1 inhibitor, rapamycin and low levels of L-citrulline. The same disconnection was observed for phosphate activation in phosphate-starved cells. The leu2 auxotrophic mutation reduces amino acid activation of trehalase, which is counteracted by deletion of GCN2. Both effects were also independent of TORC1. Our results show that rapid activation of the TOR pathway by amino acids is not involved in rapid activation of the PKA pathway and that effects of Gcn2 inactivation as well as leu2 auxotrophy all act independently of the TOR pathway. Hence, rapid nutrient signalling to PKA and TOR in cells arrested by nutrient starvation acts through parallel pathways.
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Affiliation(s)
- Michaela Conrad
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
| | - Harish Nag Kankipati
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
| | - Marlies Kimpe
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
| | - Griet Van Zeebroeck
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
| | - Zhiqiang Zhang
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
| | - Johan M Thevelein
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, B-3001 KU Leuven, Belgium.,Center for Microbiology, VIB, Kasteelpark Arenberg 31, B-3001 Leuven-Heverlee, Flanders, Belgium
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Saliba E, Evangelinos M, Gournas C, Corrillon F, Georis I, André B. The yeast H +-ATPase Pma1 promotes Rag/Gtr-dependent TORC1 activation in response to H +-coupled nutrient uptake. eLife 2018; 7:31981. [PMID: 29570051 PMCID: PMC5915174 DOI: 10.7554/elife.31981] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 03/22/2018] [Indexed: 11/25/2022] Open
Abstract
The yeast Target of Rapamycin Complex 1 (TORC1) plays a central role in controlling growth. How amino acids and other nutrients stimulate its activity via the Rag/Gtr GTPases remains poorly understood. We here report that the signal triggering Rag/Gtr-dependent TORC1 activation upon amino-acid uptake is the coupled H+ influx catalyzed by amino-acid/H+ symporters. H+-dependent uptake of other nutrients, ionophore-mediated H+ diffusion, and inhibition of the vacuolar V-ATPase also activate TORC1. As the increase in cytosolic H+ elicited by these processes stimulates the compensating H+-export activity of the plasma membrane H+-ATPase (Pma1), we have examined whether this major ATP-consuming enzyme might be involved in TORC1 control. We find that when the endogenous Pma1 is replaced with a plant H+-ATPase, H+ influx or increase fails to activate TORC1. Our results show that H+ influx coupled to nutrient uptake stimulates TORC1 activity and that Pma1 is a key actor in this mechanism. Cells adapt their growth rate depending on the amount of nutrients available. The protein complex called TORC1 plays a central role in this. When nutrients are abundant, TORC1 is very active and stimulates the production of proteins and other molecules needed for the cell to grow. However, when nutrients such as amino acids become scarce, TORC1 reduces its activity and allows the cells to adapt to starvation. This TORC1-mediated control of the metabolism is crucial for the cell to survive, and faulty TORC1 proteins have been associated with several diseases including cancers. TORC1 was originally discovered in yeast, which provides a powerful model to study this control system. However, until now, it was not known how TORC1 is reactivated when amino acids are added to cells that have been starved of these molecules. Knowing the answer to this question would allow us to better understand how the availability of nutrients controls the activity of TORC1. Now, Saliba et al. have discovered that TORC1 is not reactivated by the amino acids themselves, but by protons, which are positively charged hydrogen ions that travel into the cell together with the amino acids. This influx of protons is the driving force behind the active transport of amino acids and other nutrients into the cell, and potentially serves as a general signal to activate TORC1 in response to the uptake of nutrients, especially when cells have been starved. Furthermore, the results showed that a specific enzyme in the cell membrane plays an essential role in activating TORC1. This enzyme pumps the protons out of the cell to compensate for their influx and to maintain the proton gradient in the membrane that drives the absorption of nutrients. When this enzyme was replaced with an equivalent plant enzyme, the proton-coupled nutrient uptake did not activate TORC1 in the yeast cells. These findings may help scientists who are interested in how TORC1 is regulated in organisms other than mammals, such as plants or fungi. A next step will be to find out how exactly the proton pump in the cell membrane helps to activate TORC1.
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Affiliation(s)
- Elie Saliba
- Molecular Physiology of the Cell, Université Libre de Bruxelles, Biopark, Gosselies, Belgium
| | - Minoas Evangelinos
- Molecular Physiology of the Cell, Université Libre de Bruxelles, Biopark, Gosselies, Belgium
| | - Christos Gournas
- Molecular Physiology of the Cell, Université Libre de Bruxelles, Biopark, Gosselies, Belgium
| | - Florent Corrillon
- Molecular Physiology of the Cell, Université Libre de Bruxelles, Biopark, Gosselies, Belgium
| | - Isabelle Georis
- Institut de Recherches Microbiologiques J.-M. Wiame, Brussels, Belgium
| | - Bruno André
- Molecular Physiology of the Cell, Université Libre de Bruxelles, Biopark, Gosselies, Belgium
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Hovsepian J, Albanèse V, Becuwe M, Ivashov V, Teis D, Léon S. The yeast arrestin-related protein Bul1 is a novel actor of glucose-induced endocytosis. Mol Biol Cell 2018. [PMID: 29514933 PMCID: PMC5921569 DOI: 10.1091/mbc.e17-07-0466] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Yeast cells have a remarkable ability to adapt to nutritional changes in their environment. During adaptation, nutrient-signaling pathways drive the selective endocytosis of nutrient transporters present at the cell surface. A current challenge is to understand the mechanistic basis of this regulation. Transporter endocytosis is triggered by their ubiquitylation, which involves the ubiquitin ligase Rsp5 and its adaptors of the arrestin-related family (ART). This step is highly regulated by nutrient availability. For instance, the monocarboxylate transporter Jen1 is ubiquitylated, endocytosed, and degraded upon exposure to glucose. The ART protein Rod1 is required for this overall process; yet Rod1 rather controls Jen1 trafficking later in the endocytic pathway and is almost dispensable for Jen1 internalization. Thus, how glucose triggers Jen1 internalization remains unclear. We report that another ART named Bul1, but not its paralogue Bul2, contributes to Jen1 internalization. Bul1 responds to glucose availability, and preferentially acts at the plasma membrane for Jen1 internalization. Thus, multiple ARTs can act sequentially along the endocytic pathway to control transporter homeostasis. Moreover, Bul1 is in charge of Jen1 endocytosis after cycloheximide treatment, suggesting that the functional redundancy of ARTs may be explained by their ability to interact with multiple cargoes in various conditions.
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Affiliation(s)
- Junie Hovsepian
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Véronique Albanèse
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Michel Becuwe
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Vasyl Ivashov
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - David Teis
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Sébastien Léon
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75205 Paris, France
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Conformation-dependent partitioning of yeast nutrient transporters into starvation-protective membrane domains. Proc Natl Acad Sci U S A 2018; 115:E3145-E3154. [PMID: 29559531 DOI: 10.1073/pnas.1719462115] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The eukaryotic plasma membrane is compartmentalized into domains enriched in specific lipids and proteins. However, our understanding of the molecular bases and biological roles of this partitioning remains incomplete. The best-studied domain in yeast is the membrane compartment containing the arginine permease Can1 (MCC) and later found to cluster additional transporters. MCCs correspond to static, furrow-like invaginations of the plasma membrane and associate with subcortical structures named "eisosomes" that include upstream regulators of the target of rapamycin complex 2 (TORC2) in the sensing of sphingolipids and membrane stress. However, how and why Can1 and other nutrient transporters preferentially segregate in MCCs remains unknown. In this study we report that the clustering of Can1 in MCCs is dictated by its conformation, requires proper sphingolipid biosynthesis, and controls its ubiquitin-dependent endocytosis. In the substrate-free outward-open conformation, Can1 accumulates in MCCs in a manner dependent on sustained biogenesis of complex sphingolipids. An arginine transport-elicited shift to an inward-facing conformation promotes its cell-surface dissipation and makes it accessible to the ubiquitylation machinery triggering its endocytosis. We further show that under starvation conditions MCCs increase in number and size, this being dependent on the BAR domain-containing Lsp1 eisosome component. This expansion of MCCs provides protection for nutrient transporters from bulk endocytosis occurring in parallel with autophagy upon TORC1 inhibition. Our study reveals nutrient-regulated protection from endocytosis as an important role for protein partitioning into membrane domains.
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Accelerated invagination of vacuoles as a stress response in chronically heat-stressed yeasts. Sci Rep 2018; 8:2644. [PMID: 29422608 PMCID: PMC5805771 DOI: 10.1038/s41598-018-20781-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 01/24/2018] [Indexed: 01/01/2023] Open
Abstract
When exposed to sublethal high temperatures, budding yeast cells can survive for a period of time; however, a sufficient amount of ubiquitin is necessary for this survival. To understand the nature of the stress, we examined the morphological changes in yeast cells, focusing on the vacuoles. Changes in vacuolar morphology were notable, and ruffled vacuolar membranes, accelerated invaginations of vacuolar membranes, and vesicle-like formations were observed. These changes occurred in the absence of Atg1, Atg9 or Ivy1 but appeared to require endosomal sorting proteins, such as Vps23, Vps24 or Pep12. Furthermore, the serial sections of the vacuoles analysed using an electron microscopic analysis revealed that spherical invaginated structures were linked together in a vacuole. Because degradation of cell surface proteins is induced from heat stress, fusion of endosomal and vacuolar membranes might occur frequently in heat-stressed cells, and yeast cells might be able to cope with a rapid increase in vacuolar surface area by such invaginations.
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Regulation of Sensing, Transportation, and Catabolism of Nitrogen Sources in Saccharomyces cerevisiae. Microbiol Mol Biol Rev 2018; 82:82/1/e00040-17. [PMID: 29436478 DOI: 10.1128/mmbr.00040-17] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Nitrogen is one of the most important essential nutrient sources for biogenic activities. Regulation of nitrogen metabolism in microorganisms is complicated and elaborate. For this review, the yeast Saccharomyces cerevisiae was chosen to demonstrate the regulatory mechanism of nitrogen metabolism because of its relative clear genetic background. Current opinions on the regulation processes of nitrogen metabolism in S. cerevisiae, including nitrogen sensing, transport, and catabolism, are systematically reviewed. Two major upstream signaling pathways, the Ssy1-Ptr3-Ssy5 sensor system and the target of rapamycin pathway, which are responsible for sensing extracellular and intracellular nitrogen, respectively, are discussed. The ubiquitination of nitrogen transporters, which is the most general and efficient means for controlling nitrogen transport, is also summarized. The following metabolic step, nitrogen catabolism, is demonstrated at two levels: the transcriptional regulation process related to GATA transcriptional factors and the translational regulation process related to the general amino acid control pathway. The interplay between nitrogen regulation and carbon regulation is also discussed. As a model system, understanding the meticulous process by which nitrogen metabolism is regulated in S. cerevisiae not only could facilitate research on global regulation mechanisms and yeast metabolic engineering but also could provide important insights and inspiration for future studies of other common microorganisms and higher eukaryotic cells.
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mTORC1 as the main gateway to autophagy. Essays Biochem 2017; 61:565-584. [PMID: 29233869 PMCID: PMC5869864 DOI: 10.1042/ebc20170027] [Citation(s) in RCA: 356] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 10/19/2017] [Accepted: 10/20/2017] [Indexed: 12/16/2022]
Abstract
Cells and organisms must coordinate their metabolic activity with changes in their environment to ensure their growth only when conditions are favourable. In order to maintain cellular homoeostasis, a tight regulation between the synthesis and degradation of cellular components is essential. At the epicentre of the cellular nutrient sensing is the mechanistic target of rapamycin complex 1 (mTORC1) which connects environmental cues, including nutrient and growth factor availability as well as stress, to metabolic processes in order to preserve cellular homoeostasis. Under nutrient-rich conditions mTORC1 promotes cell growth by stimulating biosynthetic pathways, including synthesis of proteins, lipids and nucleotides, and by inhibiting cellular catabolism through repression of the autophagic pathway. Its close signalling interplay with the energy sensor AMP-activated protein kinase (AMPK) dictates whether the cell actively favours anabolic or catabolic processes. Underlining the role of mTORC1 in the coordination of cellular metabolism, its deregulation is linked to numerous human diseases ranging from metabolic disorders to many cancers. Although mTORC1 can be modulated by a number of different inputs, amino acids represent primordial cues that cannot be compensated for by any other stimuli. The understanding of how amino acids signal to mTORC1 has increased considerably in the last years; however this area of research remains a hot topic in biomedical sciences. The current ideas and models proposed to explain the interrelationship between amino acid sensing, mTORC1 signalling and autophagy is the subject of the present review.
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Barthelemy C, Barry AO, Twyffels L, André B. FTY720-induced endocytosis of yeast and human amino acid transporters is preceded by reduction of their inherent activity and TORC1 inhibition. Sci Rep 2017; 7:13816. [PMID: 29062000 PMCID: PMC5653847 DOI: 10.1038/s41598-017-14124-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 10/03/2017] [Indexed: 12/20/2022] Open
Abstract
FTY720 is a sphingoid base analog that acts as an anticancer agent in animal models. Its effect on tumor cells stems largely from its ability to trigger endocytosis of several nutrient transporters. The observation that FTY720 similarly stimulates downregulation of amino acid permeases in yeast suggests that the cellular mechanisms it targets, which are still poorly characterized, are evolutionarily conserved. We here report that adding FTY720 to yeast cells results in rapid inhibition of the intrinsic activity of multiple permeases. This effect is associated with inhibition of the TORC1 kinase complex, which in turn promotes ubiquitin-dependent permease endocytosis. Further analysis of the Gap1 permease showed that FTY720 elicits its ubiquitylation via the same factors that promote this modification when TORC1 is inhibited by rapamycin. We also show that FTY720 promotes endocytosis of the LAT1/SLC7A5 amino acid transporter in HeLa cells, this being preceded by loss of its transport activity and by mTORC1 inhibition. Our data suggest that in yeast, TORC1 deactivation resulting from FTY720-mediated inhibition of membrane transport elicits permease endocytosis. The same process seems to occur in human cells even though our data and previous reports suggest that FTY720 promotes transporter endocytosis via an additional mechanism insensitive to rapamycin.
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Affiliation(s)
- Céline Barthelemy
- Molecular Physiology of the Cell, Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium
| | - Abdoulaye Oury Barry
- Molecular Physiology of the Cell, Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium
| | - Laure Twyffels
- Center for Microscopy and Molecular Imaging (CMMI), Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium
| | - Bruno André
- Molecular Physiology of the Cell, Université libre de Bruxelles (ULB), IBMM (Biopark), Gosselies, Belgium.
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Talaia G, Gournas C, Saliba E, Barata-Antunes C, Casal M, André B, Diallinas G, Paiva S. The α-Arrestin Bul1p Mediates Lactate Transporter Endocytosis in Response to Alkalinization and Distinct Physiological Signals. J Mol Biol 2017; 429:3678-3695. [PMID: 28965784 DOI: 10.1016/j.jmb.2017.09.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/21/2017] [Accepted: 09/22/2017] [Indexed: 01/06/2023]
Abstract
Eukaryotic α-arrestins connect environmental or stress signaling pathways to the endocytosis of plasma membrane transporters or receptors. The Saccharomyces cerevisiae lactate transporter Jen1p has been used as a model cargo for elucidating the mechanisms underlying endocytic turnover in response to carbon sources. Here, we discover a novel pathway of Jen1p endocytosis mediated by the α-arrestin Bul1p in response to the presence of cycloheximide or rapamycin, or prolonged growth in lactate. While cycloheximide or rapamycin modify cells pleiotropically, the major effect of prolonged growth in lactate was shown to be external pH alkalinization. Importantly, employment of specific inactive Jen1p versions showed that Bul1p-dependent endocytosis requires lactate transport, according to the signal imposed. Our results support a model where conformational changes of Jen1p, associated with substrate/H+ symport, are critical for the efficiency of Bul1p-dependent Jen1p turnover.
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Affiliation(s)
- Gabriel Talaia
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus of Gualtar, Braga 4710-057, Portugal
| | - Christos Gournas
- Molecular Physiology of the Cell, Université Libre de Bruxelles (ULB), IBMM, Gosselies, Belgium
| | - Elie Saliba
- Molecular Physiology of the Cell, Université Libre de Bruxelles (ULB), IBMM, Gosselies, Belgium
| | - Cláudia Barata-Antunes
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus of Gualtar, Braga 4710-057, Portugal
| | - Margarida Casal
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus of Gualtar, Braga 4710-057, Portugal
| | - Bruno André
- Molecular Physiology of the Cell, Université Libre de Bruxelles (ULB), IBMM, Gosselies, Belgium
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis 15784, Athens, Greece
| | - Sandra Paiva
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus of Gualtar, Braga 4710-057, Portugal.
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Villers J, Savocco J, Szopinska A, Degand H, Nootens S, Morsomme P. Study of the Plasma Membrane Proteome Dynamics Reveals Novel Targets of the Nitrogen Regulation in Yeast. Mol Cell Proteomics 2017; 16:1652-1668. [PMID: 28679684 PMCID: PMC5587864 DOI: 10.1074/mcp.m116.064923] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 06/26/2017] [Indexed: 12/19/2022] Open
Abstract
Yeast cells, to be able to grow on a wide variety of nitrogen sources, regulate the set of nitrogen transporters present at their plasma membrane. Such regulation relies on both transcriptional and post-translational events. Although microarray studies have identified most nitrogen-sensitive genes, nitrogen-induced post-translational regulation has only been studied for very few proteins among which the general amino acid permease Gap1. Adding a preferred nitrogen source to proline-grown cells triggers Gap1 endocytosis and vacuolar degradation in an Rsp5-Bul1/2-dependent manner. Here, we used a proteomic approach to follow the dynamics of the plasma membrane proteome after addition of a preferred nitrogen source. We identified new targets of the nitrogen regulation and four transporters of poor nitrogen sources-Put4, Opt2, Dal5, and Ptr2-that rapidly decrease in abundance. Although the kinetics is different for each transporter, we found that three of them-Put4, Dal5, and Ptr2-are endocytosed, like Gap1, in an Rsp5-dependent manner and degraded in the vacuole. Finally, we showed that Gap1 stabilization at the plasma membrane, through deletion of Bul proteins, regulates the abundance of Put4, Dal5 and Ptr2.
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Affiliation(s)
- Jennifer Villers
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Jérôme Savocco
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Aleksandra Szopinska
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Hervé Degand
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Sylvain Nootens
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Pierre Morsomme
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
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46
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Gournas C, Saliba E, Krammer EM, Barthelemy C, Prévost M, André B. Transition of yeast Can1 transporter to the inward-facing state unveils an α-arrestin target sequence promoting its ubiquitylation and endocytosis. Mol Biol Cell 2017; 28:2819-2832. [PMID: 28814503 PMCID: PMC5638585 DOI: 10.1091/mbc.e17-02-0104] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 08/10/2017] [Accepted: 08/11/2017] [Indexed: 02/01/2023] Open
Abstract
Transition of the plasma membrane Can1 transporter to an inward-facing conformation, as occurs during catalysis of substrate transport, provokes the unmasking of a cytosolic region targeted by the α-arrestin protein Art1, which upon activation by TORC1 recruits the Rsp5 ubiquitin ligase, thereby causing Can1 ubiquitylation and endocytosis. Substrate-transport–elicited endocytosis is a common control mechanism of membrane transporters avoiding excess uptake of external compounds, though poorly understood at the molecular level. In yeast, endocytosis of transporters is triggered by their ubiquitylation mediated by the Rsp5 ubiquitin-ligase, recruited by α-arrestin–family adaptors. We here report that transport-elicited ubiquitylation of the arginine transporter Can1 is promoted by transition to an inward-facing state. This conformational change unveils a region of the N-terminal cytosolic tail targeted by the Art1 α-arrestin, which is activated via the TORC1 kinase complex upon arginine uptake. Can1 mutants altered in the arginine-binding site or a cytosolic tripeptide sequence permanently expose the α-arrestin–targeted region so that Art1 activation via TORC1 is sufficient to trigger their endocytosis. We also provide evidence that substrate-transport elicited endocytosis of other amino acid permeases similarly involves unmasking of a cytosolic Art1-target region coupled to activation of Art1 via TORC1. Our results unravel a mechanism likely involved in regulation of many other transporters by their own substrates. They also support the emerging view that transporter ubiquitylation relies on combinatorial interaction rules such that α-arrestins, stimulated via signaling cascades or in their basal state, recognize transporter regions permanently facing the cytosol or unveiled during transport.
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Affiliation(s)
- Christos Gournas
- Molecular Physiology of the Cell, Université Libre de Bruxelles, 6041 Gosselies, Belgium
| | - Elie Saliba
- Molecular Physiology of the Cell, Université Libre de Bruxelles, 6041 Gosselies, Belgium
| | - Eva-Maria Krammer
- Structure and Function of Biological Membranes, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Céline Barthelemy
- Molecular Physiology of the Cell, Université Libre de Bruxelles, 6041 Gosselies, Belgium
| | - Martine Prévost
- Structure and Function of Biological Membranes, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Bruno André
- Molecular Physiology of the Cell, Université Libre de Bruxelles, 6041 Gosselies, Belgium
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47
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MacDonald C, Piper RC. Genetic dissection of early endosomal recycling highlights a TORC1-independent role for Rag GTPases. J Cell Biol 2017; 216:3275-3290. [PMID: 28768685 PMCID: PMC5626546 DOI: 10.1083/jcb.201702177] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 06/07/2017] [Accepted: 07/17/2017] [Indexed: 12/11/2022] Open
Abstract
Recycling of internalized membrane proteins back to the cell surface controls diverse cellular processes. MacDonald and Piper genetically dissect a recycling pathway in yeast to reveal a cohort of novel and conserved factors, including the Rag GTPases, which contribute to metabolic control by regulating surface recycling independently of TORC1 signaling. Endocytosed cell surface membrane proteins rely on recycling pathways for their return to the plasma membrane. Although endosome-to-plasma membrane recycling is critical for many cellular processes, much of the required machinery is unknown. We discovered that yeast has a recycling route from endosomes to the cell surface that functions efficiently after inactivation of the sec7-1 allele of Sec7, which controls transit through the Golgi. A genetic screen based on an engineered synthetic reporter that exclusively follows this pathway revealed that recycling was subject to metabolic control through the Rag GTPases Gtr1 and Gtr2, which work downstream of the exchange factor Vam6. Gtr1 and Gtr2 control the recycling pathway independently of TORC1 regulation through the Gtr1 interactor Ltv1. We further show that the early-endosome recycling route and its control though the Vam6>Gtr1/Gtr2>Ltv1 pathway plays a physiological role in regulating the abundance of amino acid transporters at the cell surface.
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Affiliation(s)
- Chris MacDonald
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
| | - Robert C Piper
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
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48
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Hovsepian J, Defenouillère Q, Albanèse V, Váchová L, Garcia C, Palková Z, Léon S. Multilevel regulation of an α-arrestin by glucose depletion controls hexose transporter endocytosis. J Cell Biol 2017; 216:1811-1831. [PMID: 28468835 PMCID: PMC5461024 DOI: 10.1083/jcb.201610094] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/03/2017] [Accepted: 03/28/2017] [Indexed: 01/13/2023] Open
Abstract
Changes in nutrient availability trigger massive rearrangements of the yeast plasma membrane proteome. This work shows that the arrestin-related protein Csr2/Art8 is regulated by glucose signaling at multiple levels, allowing control of hexose transporter ubiquitylation and endocytosis upon glucose depletion. Nutrient availability controls the landscape of nutrient transporters present at the plasma membrane, notably by regulating their ubiquitylation and subsequent endocytosis. In yeast, this involves the Nedd4 ubiquitin ligase Rsp5 and arrestin-related trafficking adaptors (ARTs). ARTs are targeted by signaling pathways and warrant that cargo ubiquitylation and endocytosis appropriately respond to nutritional inputs. Here, we show that glucose deprivation regulates the ART protein Csr2/Art8 at multiple levels to trigger high-affinity glucose transporter endocytosis. Csr2 is transcriptionally induced in these conditions through the AMPK orthologue Snf1 and downstream transcriptional repressors. Upon synthesis, Csr2 becomes activated by ubiquitylation. In contrast, glucose replenishment induces CSR2 transcriptional shutdown and switches Csr2 to an inactive, deubiquitylated form. This glucose-induced deubiquitylation of Csr2 correlates with its phospho-dependent association with 14-3-3 proteins and involves protein kinase A. Thus, two glucose signaling pathways converge onto Csr2 to regulate hexose transporter endocytosis by glucose availability. These data illustrate novel mechanisms by which nutrients modulate ART activity and endocytosis.
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Affiliation(s)
- Junie Hovsepian
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Quentin Defenouillère
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Véronique Albanèse
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Libuše Váchová
- Institute of Microbiology of the Czech Academy of Sciences, v.v.i. BIOCEV, 252 50 Vestec, Czech Republic.,Faculty of Science, Charles University, BIOCEV, 252 50 Vestec, Czech Republic
| | - Camille Garcia
- Proteomics Facility, Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Zdena Palková
- Faculty of Science, Charles University, BIOCEV, 252 50 Vestec, Czech Republic
| | - Sébastien Léon
- Institut Jacques Monod, UMR 7592 Centre National de la Recherche Scientifique/Université Paris-Diderot, Sorbonne Paris Cité, 75013 Paris, France
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Ho HC, MacGurn JA, Emr SD. Deubiquitinating enzymes Ubp2 and Ubp15 regulate endocytosis by limiting ubiquitination and degradation of ARTs. Mol Biol Cell 2017; 28:1271-1283. [PMID: 28298493 PMCID: PMC5415021 DOI: 10.1091/mbc.e17-01-0008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 12/18/2022] Open
Abstract
Endocytic down-regulation of cell-surface proteins is a fundamental cellular process for cell survival and adaptation to environmental stimuli. Ubiquitination of cargo proteins serves as the sorting signal for downstream trafficking and relies on the arrestin-related trafficking adaptor (ART)-Rsp5 ubiquitin ligase adaptor network in yeast. Hence proper regulation of the abundance and activity of these ligase-adaptor complexes is critical for main-tenance of optimal plasma membrane protein composition. Here we report that the stability of ARTs is regulated by the deubiquitinating enzymes (DUBs) Ubp2 and Ubp15. By counteracting the E3 ubiquitin ligase Rsp5, Ubp2 and Ubp15 prevent hyperubiquitination and proteasomal degradation of ARTs. Specifically, we show that loss of both Ubp2 and Ubp15 results in a defect in Hxt6 endocytosis associated with Art4 instability. Our results uncover a novel function for DUBs in the endocytic pathway by which Ubp2 and Ubp15 positively regulate the ART-Rsp5 network.
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Affiliation(s)
- Hsuan-Chung Ho
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - Jason A MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Scott D Emr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
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Primo C, Ferri-Blázquez A, Loewith R, Yenush L. Reciprocal Regulation of Target of Rapamycin Complex 1 and Potassium Accumulation. J Biol Chem 2016; 292:563-574. [PMID: 27895122 DOI: 10.1074/jbc.m116.746982] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/16/2016] [Indexed: 12/19/2022] Open
Abstract
The proper maintenance of potassium homeostasis is crucial for cell viability. Among the major determinants of potassium uptake in the model organism Saccharomyces cerevisiae are the Trk1 high affinity potassium transporter and the functionally redundant Hal4 (Sat4) and Hal5 protein kinases. These kinases are required for the plasma membrane accumulation of not only Trk1 but also several nutrient permeases. Here, we show that overexpression of the target of rapamycin complex 1 (TORC1) effector NPR1 improves hal4 hal5 growth defects by stabilizing nutrient permeases at the plasma membrane. We subsequently found that internal potassium levels and TORC1 activity are linked. Specifically, growth under limiting potassium alters the activities of Npr1 and another TORC1 effector kinase, Sch9; hal4 hal5 and trk1 trk2 mutants display hypersensitivity to rapamycin, and reciprocally, TORC1 inhibition reduces potassium accumulation. Our results demonstrate that in addition to carbon and nitrogen, TORC1 also responds to and regulates potassium fluxes.
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Affiliation(s)
- Cecilia Primo
- From the Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Avd. de los Naranjos s/n, Valencia, Spain 46022 and
| | - Alba Ferri-Blázquez
- From the Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Avd. de los Naranjos s/n, Valencia, Spain 46022 and
| | - Robbie Loewith
- the Department of Molecular Biology and Institute of Genetics and Genomics of Geneva (iGE3), Swiss National Centre for Competence in Research in Chemical Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Lynne Yenush
- From the Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Avd. de los Naranjos s/n, Valencia, Spain 46022 and
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