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Pluska L, Jarosch E, Zauber H, Kniss A, Waltho A, Bagola K, von Delbrück M, Löhr F, Schulman BA, Selbach M, Dötsch V, Sommer T. The UBA domain of conjugating enzyme Ubc1/Ube2K facilitates assembly of K48/K63-branched ubiquitin chains. EMBO J 2021; 40:e106094. [PMID: 33576509 PMCID: PMC7957398 DOI: 10.15252/embj.2020106094] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 12/22/2020] [Accepted: 01/05/2021] [Indexed: 12/23/2022] Open
Abstract
The assembly of a specific polymeric ubiquitin chain on a target protein is a key event in the regulation of numerous cellular processes. Yet, the mechanisms that govern the selective synthesis of particular polyubiquitin signals remain enigmatic. The homologous ubiquitin-conjugating (E2) enzymes Ubc1 (budding yeast) and Ube2K (mammals) exclusively generate polyubiquitin linked through lysine 48 (K48). Uniquely among E2 enzymes, Ubc1 and Ube2K harbor a ubiquitin-binding UBA domain with unknown function. We found that this UBA domain preferentially interacts with ubiquitin chains linked through lysine 63 (K63). Based on structural modeling, in vitro ubiquitination experiments, and NMR studies, we propose that the UBA domain aligns Ubc1 with K63-linked polyubiquitin and facilitates the selective assembly of K48/K63-branched ubiquitin conjugates. Genetic and proteomics experiments link the activity of the UBA domain, and hence the formation of this unusual ubiquitin chain topology, to the maintenance of cellular proteostasis.
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Affiliation(s)
- Lukas Pluska
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
| | - Ernst Jarosch
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
| | - Henrik Zauber
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
| | - Andreas Kniss
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic ResonanceGoethe UniversityFrankfurt am MainGermany
| | - Anita Waltho
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
| | - Katrin Bagola
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
| | | | - Frank Löhr
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic ResonanceGoethe UniversityFrankfurt am MainGermany
| | - Brenda A Schulman
- Department of Molecular Machines and SignalingMax Planck Institute of BiochemistryMartinsriedGermany
| | - Matthias Selbach
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
- Charité – Universitätsmedizin BerlinBerlinGermany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic ResonanceGoethe UniversityFrankfurt am MainGermany
| | - Thomas Sommer
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz AssociationBerlin‐BuchGermany
- Institute for BiologyHumboldt‐Universität zu BerlinBerlinGermany
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Glucose regulation of the paralogous glucose sensing receptors Rgt2 and Snf3 of the yeast Saccharomyces cerevisiae. Biochim Biophys Acta Gen Subj 2021; 1865:129881. [PMID: 33617932 DOI: 10.1016/j.bbagen.2021.129881] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/08/2021] [Accepted: 02/16/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND The yeast Saccharomyces cerevisiae senses extracellular glucose levels through the two paralogous glucose sensing receptors Rgt2 and Snf3, which appear to sense high and low levels of glucose, respectively. METHODS Western blotting and qRT-PCR were used to determine expression levels of the glucose sensing receptors. RESULTS Rgt2 and Snf3 are expressed at different levels in response to different glucose concentrations. SNF3 expression is repressed by high glucose, whereas Rgt2 is turned over in response to glucose starvation. As a result, Rgt2 is predominant in cells grown on high glucose, whereas Snf3 is more abundant of the two paralogs in cells grown on low glucose. When expressed from a constitutive promoter, however, Snf3 behaves like Rgt2, being able to transduce the high glucose signal that induces HXT1 expression. Of note, constitutively active Rgt2 does not undergo glucose starvation-induced endocytic downregulation, whereas signaling defective Rgt2 is constitutively targeted for vacuolar degradation. These results suggest that glucose protects Rgt2 from endocytic degradation and reveal a previously unknown function of glucose as a signaling molecule that regulates the stability of its receptor. CONCLUSION Expression of Rgt2 and Snf3 is regulated by different mechanisms: Rgt2 expression is highly regulated at the level of protein stability; Snf3 expression is mainly regulated at the level of transcription. GENERAL SIGNIFICANCE The difference in the roles of Rgt2 and Snf3 in glucose sensing is a consequence of their cell surface abundance rather than a result of the two paralogous proteins having different functions.
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Watcharawipas A, Watanabe D, Takagi H. Sodium Acetate Responses in Saccharomyces cerevisiae and the Ubiquitin Ligase Rsp5. Front Microbiol 2018; 9:2495. [PMID: 30459728 PMCID: PMC6232821 DOI: 10.3389/fmicb.2018.02495] [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: 07/21/2018] [Accepted: 09/28/2018] [Indexed: 12/31/2022] Open
Abstract
Recent studies have revealed the feasibility of sodium acetate as a potentially novel inhibitor/stressor relevant to the fermentation from neutralized lignocellulosic hydrolysates. This mini-review focuses on the toxicity of sodium acetate, which is composed of both sodium and acetate ions, and on the involved cellular responses that it elicits, particularly via the high-osmolarity glycerol (HOG) pathway, the Rim101 pathway, the P-type ATPase sodium pumps Ena1/2/5, and the ubiquitin ligase Rsp5 with its adaptors. Increased understanding of cellular responses to sodium acetate would improve our understanding of how cells respond not only to different stimuli but also to composite stresses induced by multiple components (e.g., sodium and acetate) simultaneously. Moreover, unraveling the characteristics of specific stresses under industrially related conditions and the cellular responses evoked by these stresses would be a key factor in the industrial yeast strain engineering toward the increased productivity of not only bioethanol but also advanced biofuels and valuable chemicals that will be in demand in the coming era of bio-based industry.
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Affiliation(s)
- Akaraphol Watcharawipas
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara, Japan
| | - Daisuke Watanabe
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara, Japan
| | - Hiroshi Takagi
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara, Japan
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4
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Lorenz S. Structural mechanisms of HECT-type ubiquitin ligases. Biol Chem 2018; 399:127-145. [PMID: 29016349 DOI: 10.1515/hsz-2017-0184] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 09/25/2017] [Indexed: 12/31/2022]
Abstract
Ubiquitin ligases (E3 enzymes) transfer ubiquitin from ubiquitin-conjugating (E2) enzymes to target proteins. By determining the selection of target proteins, modification sites on those target proteins, and the types of ubiquitin modifications that are formed, E3 enzymes are key specificity factors in ubiquitin signaling. Here, I summarize our knowledge of the structural mechanisms in the HECT E3 subfamily, many members of which play important roles in human disease. I discuss interactions of the conserved HECT domain with E2 enzymes, ubiquitin and target proteins, as well as macromolecular interactions with regulatory functions. While we understand individual steps in the catalytic cycle of HECT E3 enzymes on a structural level, this review also highlights key aspects that have yet to be elucidated. For instance, it remains unclear how diverse target proteins are presented to the catalytic center and how certain HECT E3 enzymes achieve specificity in ubiquitin linkage formation. The structural and functional properties of the N-terminal regions of HECT E3 enzymes that likely act as signaling hubs are also largely unknown. Structural insights into these aspects may open up routes for a therapeutic intervention with specific HECT E3 functions in distinct pathophysiological settings.
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Affiliation(s)
- Sonja Lorenz
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
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5
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Tanaka M, Hiramoto T, Tada H, Shintani T, Gomi K. Improved α-Amylase Production by Dephosphorylation Mutation of CreD, an Arrestin-Like Protein Required for Glucose-Induced Endocytosis of Maltose Permease and Carbon Catabolite Derepression in Aspergillus oryzae. Appl Environ Microbiol 2017; 83:e00592-17. [PMID: 28455339 PMCID: PMC5478985 DOI: 10.1128/aem.00592-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 04/24/2017] [Indexed: 12/17/2022] Open
Abstract
Aspergillusoryzae produces copious amount of amylolytic enzymes, and MalP, a major maltose permease, is required for the expression of amylase-encoding genes. The expression of these genes is strongly repressed by carbon catabolite repression (CCR) in the presence of glucose. MalP is transported from the plasma membrane to the vacuole by endocytosis, which requires the homolog of E6-AP carboxyl terminus ubiquitin ligase HulA, an ortholog of yeast Rsp5. In yeast, arrestin-like proteins mediate endocytosis as adaptors of Rsp5 and transporters. In the present study, we examined the involvement of CreD, an arrestin-like protein, in glucose-induced MalP endocytosis and CCR of amylase-encoding genes. Deletion of creD inhibited the glucose-induced endocytosis of MalP, and CreD showed physical interaction with HulA. Phosphorylation of CreD was detected by Western blotting, and two serine residues were determined as the putative phosphorylation sites. However, the phosphorylation state of the serine residues did not regulate MalP endocytosis and its interaction with HulA. Although α-amylase production was significantly repressed by creD deletion, both phosphorylation and dephosphorylation mimics of CreD had a negligible effect on α-amylase activity. Interestingly, dephosphorylation of CreD was required for CCR relief of amylase genes that was triggered by disruption of the deubiquitinating enzyme-encoding gene creB The α-amylase activity of the creB mutant was 1.6-fold higher than that of the wild type, and the dephosphorylation mimic of CreD further improved the α-amylase activity by 2.6-fold. These results indicate that a combination of the dephosphorylation mutation of CreD and creB disruption increased the production of amylolytic enzymes in A. oryzaeIMPORTANCE In eukaryotes, glucose induces carbon catabolite repression (CCR) and proteolytic degradation of plasma membrane transporters via endocytosis. Glucose-induced endocytosis of transporters is mediated by their ubiquitination, and arrestin-like proteins act as adaptors of transporters and ubiquitin ligases. In this study, we showed that CreD, an arrestin-like protein, is involved in glucose-induced endocytosis of maltose permease and carbon catabolite derepression of amylase gene expression in Aspergillusoryzae Dephosphorylation of CreD was required for CCR relief triggered by the disruption of creB, which encodes a deubiquitinating enzyme; a combination of the phosphorylation-defective mutation of CreD and creB disruption dramatically improved α-amylase production. This study shows the dual function of an arrestin-like protein and provides a novel approach for improving the production of amylolytic enzymes in A. oryzae.
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Affiliation(s)
- Mizuki Tanaka
- Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Japan
| | - Tetsuya Hiramoto
- Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Japan
| | - Hinako Tada
- Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Japan
| | - Takahiro Shintani
- Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Japan
| | - Katsuya Gomi
- Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Japan
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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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7
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Roy A, Kim JH. Endocytosis and vacuolar degradation of the yeast cell surface glucose sensors Rgt2 and Snf3. J Biol Chem 2014; 289:7247-7256. [PMID: 24451370 DOI: 10.1074/jbc.m113.539411] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sensing and signaling the presence of extracellular glucose is crucial for the yeast Saccharomyces cerevisiae because of its fermentative metabolism, characterized by high glucose flux through glycolysis. The yeast senses glucose through the cell surface glucose sensors Rgt2 and Snf3, which serve as glucose receptors that generate the signal for induction of genes involved in glucose uptake and metabolism. Rgt2 and Snf3 detect high and low glucose concentrations, respectively, perhaps because of their different affinities for glucose. Here, we provide evidence that cell surface levels of glucose sensors are regulated by ubiquitination and degradation. The glucose sensors are removed from the plasma membrane through endocytosis and targeted to the vacuole for degradation upon glucose depletion. The turnover of the glucose sensors is inhibited in endocytosis defective mutants, and the sensor proteins with a mutation at their putative ubiquitin-acceptor lysine residues are resistant to degradation. Of note, the low affinity glucose sensor Rgt2 remains stable only in high glucose grown cells, and the high affinity glucose sensor Snf3 is stable only in cells grown in low glucose. In addition, constitutively active, signaling forms of glucose sensors do not undergo endocytosis, whereas signaling defective sensors are constitutively targeted for degradation, suggesting that the stability of the glucose sensors may be associated with their ability to sense glucose. Therefore, our findings demonstrate that the amount of glucose available dictates the cell surface levels of the glucose sensors and that the regulation of glucose sensors by glucose concentration may enable yeast cells to maintain glucose sensing activity at the cell surface over a wide range of glucose concentrations.
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Affiliation(s)
- Adhiraj Roy
- Department of Biochemistry and Molecular Medicine, George Washington University Medical Center, Washington, D.C. 20037
| | - Jeong-Ho Kim
- Department of Biochemistry and Molecular Medicine, George Washington University Medical Center, Washington, D.C. 20037.
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8
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Regulations of sugar transporters: insights from yeast. Curr Genet 2013; 59:1-31. [PMID: 23455612 DOI: 10.1007/s00294-013-0388-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 01/28/2013] [Accepted: 02/02/2013] [Indexed: 12/24/2022]
Abstract
Transport across the plasma membrane is the first step at which nutrient supply is tightly regulated in response to intracellular needs and often also rapidly changing external environment. In this review, I describe primarily our current understanding of multiple interconnected glucose-sensing systems and signal-transduction pathways that ensure fast and optimum expression of genes encoding hexose transporters in three yeast species, Saccharomyces cerevisiae, Kluyveromyces lactis and Candida albicans. In addition, an overview of GAL- and MAL-specific regulatory networks, controlling galactose and maltose utilization, is provided. Finally, pathways generating signals inducing posttranslational degradation of sugar transporters will be highlighted.
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Gournas C, Amillis S, Vlanti A, Diallinas G. Transport-dependent endocytosis and turnover of a uric acid-xanthine permease. Mol Microbiol 2010; 75:246-60. [DOI: 10.1111/j.1365-2958.2009.06997.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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10
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Polyubiquitination by HECT E3s and the determinants of chain type specificity. Mol Cell Biol 2009; 29:3307-18. [PMID: 19364824 DOI: 10.1128/mcb.00240-09] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polyubiquitination can mediate several different biochemical functions, determined in part by which lysine of ubiquitin is used to link the polyubiquitin chain. Among the HECT domain ubiquitin ligases, some, such as human E6AP, preferentially catalyze the formation of K48-linked polyubiquitin chains, while others, including Saccharomyces cerevisiae Rsp5 and human Itch, preferentially catalyze the formation of K63-linked chains. The features of HECT E3s that determine their chain type specificities have not been identified. We show here that chain type specificity is a function solely of the Rsp5 HECT domain, that the identity of the cooperating E2 protein does not influence the chain type specificity, that single chains produced by Rsp5 contain between 12 and 30 ubiquitin moieties, and that the determinants of chain type specificity are located within the last 60 amino acids of the C lobe of the HECT domain. Our results are also consistent with a simple sequential-addition mechanism for polyubiquitination by Rsp5, rather than a mechanism involving the formation of either E2- or E3-linked polyubiquitin chain transfers.
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Hatanaka H, Omura F, Kodama Y, Ashikari T. Gly-46 and His-50 of yeast maltose transporter Mal21p are essential for its resistance against glucose-induced degradation. J Biol Chem 2009; 284:15448-57. [PMID: 19359240 DOI: 10.1074/jbc.m808151200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The maltose transporter gene is situated at the MAL locus, which consists of genes for a transporter, maltase, and transcriptional activator. Five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4, and MAL6) constitute a gene family in Saccharomyces cerevisiae. The expression of the maltose transporter is induced by maltose and repressed by glucose. The activity of the maltose transporter is also regulated post-translationally; Mal61p is rapidly internalized from the plasma membrane and degraded by ubiquitin-mediated proteolysis in the presence of glucose. We found that S. cerevisiae strain ATCC20598 harboring MAL21 could grow in maltose supplemented with a non- assimilable glucose analogue, 2-deoxyglucose, whereas strain ATCC96955 harboring MAL61 and strain CB11 with MAL31 and AGT1 could not. These observations implied a Mal21p-specific resistance against glucose-induced degradation. Mal21p found in ATCC20598 has 10 amino acids, including Gly-46 and His-50, that are inconsistent with the corresponding residues in Mal61p. The half-life of Mal21p for glucose-induced degradation was 118 min when expressed using the constitutive TPI1 promoter, which was significantly longer than that of Mal61p (25 min). Studies with mutant cells that are defective in endocytosis or the ubiquitination process indicated that Mal21p was less ubiquitinated than Mal61p, suggesting that Mal21p remains on the plasma membrane because of poor susceptibility to ubiquitination. Mutational studies revealed that both residues Gly-46 and His-50 in Mal21p are essential for the full resistance of maltose transporters against glucose-induced degradation.
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12
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Manzano C, Abraham Z, López-Torrejón G, Del Pozo JC. Identification of ubiquitinated proteins in Arabidopsis. PLANT MOLECULAR BIOLOGY 2008; 68:145-58. [PMID: 18535787 DOI: 10.1007/s11103-008-9358-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 05/27/2008] [Indexed: 05/03/2023]
Abstract
Ubiquitin (Ub) is a small peptide that is covalently attached to proteins in a posttranslational reaction. Ubiquitination is a precise regulatory system that is present in all eukaryotic organisms and regulates the stability, the activity, the localization and the transport of proteins. Ubiquitination involves different enzymatic activities, in which the E3 ligases catalyze the last step recruiting of the target for labelling with ubiquitin. Genomic analyses have shown that the ubiquitin-proteasome system involves a large number of proteins in plants, as approximately 5% of the total protein belongs to this pathway. In contrast to the high number of E3 ligases of ubiquitin identified, very few proteins regulated by ubiquitination have been described. To solve this, we have undertaken a new proteomic approach aimed to identify proteins modified with ubiquitin. This is based on affinity purification and identification for ubiquitinated proteins using the ubiquitin binding domain (UBA) polypeptide of the P62 protein attached to agarose beads. This P62-agarose matrix is capable of specifically binding ubiquitinated proteins. These bound proteins were digested with trypsin and the peptides separated by HPLC chromatography, spotted directly onto a MALDI target and analyzed by MALDI-TOF/TOF off-line coupled LC/MALDI-MS/MS. A total of 200 putative ubiquitinated proteins were identified. From these we found that several of the putative targets were already described in plants, as well as in other organisms, as ubiquitinated proteins. In addition, we have found that some of these proteins were indeed modified with ubiquitin in vivo. Taken together, we have shown that this approach is useful for identifying ubiquitinated protein in plants.
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Affiliation(s)
- Concepción Manzano
- Centro de Biotecnología y Genómica de Plantas, Campus de Montegancedo s/n. Boadilla del Monte, Madrid, Spain
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Musch MW, Puffer AB, Goldstein L. Volume expansion stimulates monoubiquitination and endocytosis of surface-expressed skate anion-exchanger isoform. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1657-65. [DOI: 10.1152/ajpregu.00837.2007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In hyposmotic medium, skate erythrocytes swell and then lose taurine and other solutes with obligate water to achieve a regulatory volume decrease (RVD) over a 90-min period. The skate erythrocyte anion-exchanger isoform 1 (skAE1) participates in the RVD, and increased surface expression after hyposmolality-induced volume expansion occurs within 5 min but decreases to baseline within 120 min. The subsequent fate of skAE1 is the focus of these studies. SkAE1 sent to the surface becomes monoubiquitinated, a modification that is present while skAE1 is associated with clathrin and Rab5 but is removed before skAE1 is passed to the Rab4 compartment. Endocytosis of skAE1 involves clathrin-mediated internalization. Surface plasma membrane skAE1 forms tetramers and demonstrates increased tyrosine phosphorylation, and both of these processes decrease before skAE1 appears in the Rab5 compartment. Volume expansion-stimulated surface skAE1 comes from an intracellular pool in a buoyant membrane fraction resistant to nonionic detergent extraction (DRM), and the amount of skAE1 increases in this buoyant DRM fraction on the surface. Clathrin heavy chain is found largely in the erythrocyte DRM, but in dense, rather than buoyant, fractions. Rab5- and Rab4-containing membranes are largely detergent soluble, suggesting that as skAE1 is passed to clathrin and then to Rab5 compartments, the membrane microdomain composition changes. The present studies demonstrate that skAE1, which appears on the surface after hyposmolality-induced volume expansion, is monoubiquitinated, a modification that may serve as a signal for removal of skAE1 from the surface. This modification is eliminated after clathrin-mediated removal of skAE1 in a membrane domain containing Rab5, potentially permitting recycling and reuse of skAE1.
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Estrella LA, Krishnamurthy S, Timme CR, Hampsey M. The Rsp5 E3 Ligase Mediates Turnover of Low Affinity Phosphate Transporters in Saccharomyces cerevisiae. J Biol Chem 2008; 283:5327-34. [DOI: 10.1074/jbc.m703630200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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15
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Medintz IL, Vora GJ, Rahbar AM, Thach DC. Transcript and proteomic analyses of wild-type and gpa2 mutant Saccharomyces cerevisiae strains suggest a role for glycolytic carbon source sensing in pseudohyphal differentiation. MOLECULAR BIOSYSTEMS 2007; 3:623-34. [PMID: 17700863 DOI: 10.1039/b704199c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In response to limited nitrogen and abundant carbon sources, diploid Saccharomyces cerevisiae strains undergo a filamentous transition in cell growth as part of pseudohyphal differentiation. Use of the disaccharide maltose as the principal carbon source, in contrast to the preferred nutrient monosaccharide glucose, has been shown to induce a hyper-filamentous growth phenotype in a strain deficient for GPA2 which codes for a Galpha protein component that interacts with the glucose-sensing receptor Gpr1p to regulate filamentous growth. In this report, we compare the global transcript and proteomic profiles of wild-type and Gpa2p deficient diploid yeast strains grown on both rich and nitrogen starved maltose media. We find that deletion of GPA2 results in significantly different transcript and protein profiles when switching from rich to nitrogen starvation media. The results are discussed with a focus on the genes associated with carbon utilization, or regulation thereof, and a model for the contribution of carbon sensing/metabolism-based signal transduction to pseudohyphal differentiation is proposed.
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Affiliation(s)
- Igor L Medintz
- Center for Bio/Molecular Science and Engineering, Code 6900, US Naval Research Laboratory, Washington, DC 20375, USA.
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16
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Gadura N, Michels CA. Sequences in the N-terminal cytoplasmic domain of Saccharomyces cerevisiae maltose permease are required for vacuolar degradation but not glucose-induced internalization. Curr Genet 2006; 50:101-14. [PMID: 16741702 DOI: 10.1007/s00294-006-0080-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2006] [Revised: 04/21/2006] [Accepted: 04/23/2006] [Indexed: 12/31/2022]
Abstract
In Saccharomyces cerevisiae, glucose addition to maltose fermenting cells causes a rapid loss of maltose transport activity and ubiquitin-mediated vacuolar proteolysis of maltose permease. GFP-tagged Mal61 maltose permease was used to explore the role of the N-terminal cytoplasmic domain in glucose-induced inactivation. In maltose-grown cells, Mal61/HA-GFP localizes to the cell surface and, surprisingly, to the vacuole. Studies of end3Delta and doa4Delta mutants indicate that a slow constitutive internalization of Mal61/HA-GFP is required for its vacuolar localization. Site-specific mutagenesis of multiple serine/threonine residues in a putative PEST sequence of the N-terminal cytoplasmic domain of maltose permease blocks glucose-induced Mal61p degradation but does not affect the rapid loss of maltose transport activity associated with glucose-induced internalization. The internalized multiple Ser/Thr mutant protein co-localizes with Snf7p in a putative late endosome or E-compartment. Further, alteration of a putative dileucine [D/EExxxLL/I] motif at residues 64-70 causes a significant defect in maltose transport activity and mislocalization to an E-compartment but appears to have little impact on glucose-induced internalization. We conclude that the N-terminal cytoplasmic domain of maltose permease is not the target of the signaling pathways leading to glucose-induced internalization of Mal61 permease but is required for its subsequent delivery to the vacuole for degradation.
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Affiliation(s)
- Nidhi Gadura
- Biology Department, Queens College and the Graduate School of the City University of New York, Flushing, 11367, USA
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17
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Abstract
Ubiquitylation of membrane proteins has gained considerable interest in recent years. It has been recognized as a signal that negatively regulates the cell surface expression of many plasma membrane proteins both in yeast and in mammalian cells. Moreover, it is also involved in endoplasmic reticulum-associated degradation of membrane proteins, and it acts as a sorting signal both in the secretory pathway and in endosomes, where it targets proteins into multivesicular bodies in the lumen of vacuoles/lysosomes. In this review we discuss the progress in understanding these processes, achieved during the past several years.
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Affiliation(s)
- Olivier Staub
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.
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18
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Stimpson HEM, Lewis MJ, Pelham HRB. Transferrin receptor-like proteins control the degradation of a yeast metal transporter. EMBO J 2006; 25:662-72. [PMID: 16456538 PMCID: PMC1383565 DOI: 10.1038/sj.emboj.7600984] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Accepted: 01/11/2006] [Indexed: 11/09/2022] Open
Abstract
Plasma membrane transporters are often downregulated by their substrates. The yeast manganese transporter Smf1 is subject to two levels of regulation: heavy metals induce its sequestration within the cell, and also its ubiquitination and degradation in the vacuole. Degradation requires Bsd2, a membrane protein with a PPxY motif that recruits the ubiquitin ligase Rsp5, and which has a role in the quality control of membrane proteins, that expose hydrophilic residues to the lipid bilayer. We show that degradation of Smf1 requires in addition one of a pair of related yeast proteins, Tre1 and Tre2, that also contain PPxY motifs. Tre1 can partially inhibit manganese uptake without Bsd2, but requires Bsd2 to induce Smf1 degradation. It has a relatively hydrophilic transmembrane domain and binds to Bsd2. We propose that the Tre proteins specifically link Smf1 to the Bsd2-dependent quality control system. Their luminal domains are related to the transferrin receptor, but these are dispensable for Smf1 regulation. Tre proteins and the transferrin receptors appear to have evolved independently from the same family of membrane-associated proteases.
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Affiliation(s)
| | | | - Hugh R B Pelham
- MRC Laboratory of Molecular Biology, Cambridge, UK
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK. Tel.: +44 1223 402290; Fax: +44 1223 412142; E-mail:
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19
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Gadura N, Robinson LC, Michels CA. Glc7-Reg1 phosphatase signals to Yck1,2 casein kinase 1 to regulate transport activity and glucose-induced inactivation of Saccharomyces maltose permease. Genetics 2005; 172:1427-39. [PMID: 16361229 PMCID: PMC1456300 DOI: 10.1534/genetics.105.051698] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Saccharomyces casein kinase 1 isoforms encoded by the essential gene pair YCK1 and YCK2 control cell growth and morphogenesis and are linked to the endocytosis of several membrane proteins. Here we define roles for the Yck1,2 kinases in Mal61p maltose permease activation and trafficking, using a yck1delta yck2-2(ts) (yck(ts)) strain with conditional Yck activity. Moreover, we provide evidence that Glc7-Reg1 phosphatase acts as an upstream activator of Yck1,2 kinases in a novel signaling pathway that modulates kinase activity in response to carbon source availability. The yck(ts) strain exhibits significantly reduced maltose transport activity despite apparently normal levels and cell surface localization of maltose permease protein. Glucose-induced internalization and rapid loss of maltose transport activity of Mal61/HAp-GFP are not observed in the yck(ts) strain and maltose permease proteolysis is blocked. We show that a reg1delta mutant exhibits a phenotype remarkably similar to that conferred by yck(ts). The reg1delta phenotype is not enhanced in the yck(ts) reg1delta double mutant and is suppressed by increased Yck1,2p dosage. Further, although Yck2p localization and abundance do not change in the reg1delta mutant, Yck1,2 kinase activity, as assayed by glucose-induced HXT1 expression and Mth1 repressor stability, is substantially reduced in the reg1delta strain.
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Affiliation(s)
- Nidhi Gadura
- Biology Department, Queens College and the Graduate School of CUNY, Flushing, New York 11367, USA
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20
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Eguez L, Chung YS, Kuchibhatla A, Paidhungat M, Garrett S. Yeast Mn2+ transporter, Smf1p, is regulated by ubiquitin-dependent vacuolar protein sorting. Genetics 2005; 167:107-17. [PMID: 15166140 PMCID: PMC1470849 DOI: 10.1534/genetics.167.1.107] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conditional cdc1(Ts) mutants of S. cerevisiae arrest with a phenotype similar to that exhibited by Mn(2+)-depleted cells. Sequence similarity between Cdc1p and a class of Mn(2+)-dependent phosphoesterases, as well as the observation that conditional cdc1(Ts) growth can be ameliorated by Mn(2+) supplement, suggests that Cdc1p activity is sensitive to intracellular Mn(2+) levels. This article identifies several previously uncharacterized cdc1(Ts) suppressors as class E vps (vacuolar protein sorting) mutants and shows that these, as well as other vps mutants, accumulate high levels of intracellular Mn(2+). Yeast VPS genes play a role in delivery of membrane transporters to the vacuole for degradation, and we show that the vps mutants accumulate elevated levels of the high-affinity Mn(2+) transporter Smf1p. cdc1(Ts) conditional growth is also alleviated by mutations, including doa4 and ubc4, that compromise protein ubiquitination, and these ubiquitination defects are associated with Smf1p accumulation. Epistasis studies show that these suppressors require functional Smf1p to alleviate the cdc1(Ts) growth defect, whereas Smf1p is dispensable for cdc1(Ts) suppression by a mutation (cos16/per1) that does not influence intracellular Mn(2+) levels. Because Smf1p is ubiquitinated in vivo, we propose that Smf1p is targeted to the vacuole for degradation by ubiquitination-dependent protein sorting.
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Affiliation(s)
- Lorena Eguez
- Department of Microbiology and Molecular Genetics and Graduate School of Biomedical Sciences, University of Medicine and Dentistry-New Jersey Medical School, Newark, New Jersey 07103-2714, USA
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21
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Jules M, Guillou V, François J, Parrou JL. Two distinct pathways for trehalose assimilation in the yeast Saccharomyces cerevisiae. Appl Environ Microbiol 2004; 70:2771-8. [PMID: 15128531 PMCID: PMC404389 DOI: 10.1128/aem.70.5.2771-2778.2004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The yeast Saccharomyces cerevisiae can synthesize trehalose and also use this disaccharide as a carbon source for growth. However, the molecular mechanism by which extracellular trehalose can be transported to the vacuole and degraded by the acid trehalase Ath1p is not clear. By using an adaptation of the assay of invertase on whole cells with NaF, we showed that more than 90% of the activity of Ath1p is extracellular, splitting of the disaccharide into glucose. We also found that Agt1p-mediated trehalose transport and the hydrolysis of the disaccharide by the cytosolic neutral trehalase Nth1p are coupled and represent a second, independent pathway, although there are several constraints on this alternative route. First, the AGT1/MAL11 gene is controlled by the MAL system, and Agt1p was active in neither non-maltose-fermenting nor maltose-inducible strains. Second, Agt1p rapidly lost activity during growth on trehalose, by a mechanism similar to the sugar-induced inactivation of the maltose permease. Finally, both pathways are highly pH sensitive and effective growth on trehalose occurred only when the medium was buffered at around pH 5.0. The catabolism of trehalose was purely oxidative, and since levels of Ath1p limit the glucose flux in the cells, batch cultures on trehalose may provide a useful alternative to glucose-limited chemostat cultures for investigation of metabolic responses in yeast.
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Affiliation(s)
- Matthieu Jules
- Centre de Bioingénierie Gilbert Durand, UMR-CNRS 5504, UMR-INRA 792, Complexe Scientifique de Rangueil, 31077 Toulouse Cedex 04, France
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22
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Jansen MLA, Daran-Lapujade P, de Winde JH, Piper MDW, Pronk JT. Prolonged maltose-limited cultivation of Saccharomyces cerevisiae selects for cells with improved maltose affinity and hypersensitivity. Appl Environ Microbiol 2004; 70:1956-63. [PMID: 15066785 PMCID: PMC383169 DOI: 10.1128/aem.70.4.1956-1963.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Accepted: 12/22/2003] [Indexed: 11/20/2022] Open
Abstract
Prolonged cultivation (>25 generations) of Saccharomyces cerevisiae in aerobic, maltose-limited chemostat cultures led to profound physiological changes. Maltose hypersensitivity was observed when cells from prolonged cultivations were suddenly exposed to excess maltose. This substrate hypersensitivity was evident from massive cell lysis and loss of viability. During prolonged cultivation at a fixed specific growth rate, the affinity for the growth-limiting nutrient (i.e., maltose) increased, as evident from a decreasing residual maltose concentration. Furthermore, the capacity of maltose-dependent proton uptake increased up to 2.5-fold during prolonged cultivation. Genome-wide transcriptome analysis showed that the increased maltose transport capacity was not primarily due to increased transcript levels of maltose-permease genes upon prolonged cultivation. We propose that selection for improved substrate affinity (ratio of maximum substrate consumption rate and substrate saturation constant) in maltose-limited cultures leads to selection for cells with an increased capacity for maltose uptake. At the same time, the accumulative nature of maltose-proton symport in S. cerevisiae leads to unrestricted uptake when maltose-adapted cells are exposed to a substrate excess. These changes were retained after isolation of individual cell lines from the chemostat cultures and nonselective cultivation, indicating that mutations were involved. The observed trade-off between substrate affinity and substrate tolerance may be relevant for metabolic engineering and strain selection for utilization of substrates that are taken up by proton symport.
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Affiliation(s)
- Mickel L A Jansen
- Department of Biotechnology, Delft University of Technology, 2628 BC Delft, The Netherlands
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23
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Membrane trafficking of yeast transporters: mechanisms and physiological control of downregulation. MOLECULAR MECHANISMS CONTROLLING TRANSMEMBRANE TRANSPORT 2004. [DOI: 10.1007/b97215] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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24
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Gitan RS, Shababi M, Kramer M, Eide DJ. A cytosolic domain of the yeast Zrt1 zinc transporter is required for its post-translational inactivation in response to zinc and cadmium. J Biol Chem 2003; 278:39558-64. [PMID: 12893829 DOI: 10.1074/jbc.m302760200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nutrient metals such as zinc are both essential to life and potentially toxic if overaccumulated by cells. Non-essential toxic metals like cadmium can enter cells through the uptake transporters responsible for nutrient metal acquisition. Therefore, in the face of ever changing extracellular metal levels, organisms tightly control their intracellular levels of nutrient metals and prevent accumulation of toxic metals. We show here that post-translational inactivation of the yeast Zrt1 zinc uptake transporter is important for zinc homeostasis. During the transition from zinc-limiting to zinc-replete growth conditions (i.e. zinc shock), the Zrt1 transporter is ubiquitinated, endocytosed, and subsequently degraded in the vacuole. To further understand this process at a molecular level, we mapped a region of Zrt1 required for ubiquitination and endocytosis in response to zinc to a domain located on the intracellular surface of the plasma membrane. This domain is a critical cis-acting component of the metal signaling pathway that controls Zrt1 protein trafficking. Using mutant alleles defective for metal-responsive inactivation, we also show that Zrt1 inactivation may be an important mechanism for preventing cadmium uptake and toxicity in zinc-limited cells.
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Affiliation(s)
- Raad S Gitan
- Department of Nutritional Sciences and Biochemistry, University of Missouri, Columbia, Missouri 65211, USA
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25
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Horák J. The role of ubiquitin in down-regulation and intracellular sorting of membrane proteins: insights from yeast. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1614:139-55. [PMID: 12896807 DOI: 10.1016/s0005-2736(03)00195-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Ubiquitination is a versatile tool used by all eukaryotic organisms for controlling the stability, function, and intracellular localization of a wide variety of proteins. Two of the best characterized functions of protein ubiquitination are to mark proteins for degradation by cytosolic proteasome and to promote the internalization of certain plasma membrane proteins via the endocytotic pathway, followed by their degradation in the vacuole. Recent studies of membrane proteins both in yeast and mammalian cells suggest that the role of ubiquitin may extend beyond its function as an internalization signal in that it also may be required for modification of some component(s) of the endocytotic machinery, and for cargo protein sorting at the late endosome and the Golgi apparatus level. In this review, I will attempt to bring together what is currently known about the role of ubiquitination in controlling protein trafficking between the yeast plasma membrane, the trans-Golgi network, and the vacuole/lysosome.
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Affiliation(s)
- Jaroslav Horák
- Department of Membrane Transport, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague, Czech Republic.
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26
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Wang X, Bali M, Medintz I, Michels CA. Intracellular maltose is sufficient to induce MAL gene expression in Saccharomyces cerevisiae. EUKARYOTIC CELL 2002; 1:696-703. [PMID: 12455689 PMCID: PMC126750 DOI: 10.1128/ec.1.5.696-703.2002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The presence of maltose induces M4L gene expression in Saccharomyces cells, but little is known abouthow maltose is sensed. Strains with all maltose permease genes deleted are unable to induce MAL geneexpression. In this study, we examined the role of maltose permease in maltose sensing by substituting a heterologous transporter for the native maltose permease. PmSUC2 encodes a sucrose transporter from the dicot plant Plantago major that exhibits no significant sequence homology to maltose permease. When expressed in Saccharomyces cerevisiae, PmSUC2 is capable of transporting maltose, albeit at a reduced rate. We showed that introduction of PmSUC2 restores maltose-inducible MAL gene expression to a maltose permease-null mutant and that this induction requires the MAL activator. These data indicate that intracellular maltose is sufficient to induce MAL gene expression independently of the mechanism of maltose transport. By usingstrains expressing defective mal61 mutant alleles, we demonstrated a correlation between the rate of maltose transport and the level of the induction, which is particularly evident in medium containing very limiting concentrations of maltose. Moreover, our results indicate that a rather low concentration of intracellular maltose is needed to trigger MAL gene expression. We also showed that constitutive overexpression of either MAL61 maltose permease or PmSUC2 suppresses the noninducible phenotype of a defective mal13 MAL-activator allele, suggesting that this suppression is solely a function of maltose transport activity and is not specific to the sequence of the permease. Our studies indicate that maltose permease does not function as the maltose sensor in S. cerevisiae.
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Affiliation(s)
- Xin Wang
- Queens College and Graduate School of City University of New York, Biology Department, Flushing, New York 11367, USA
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27
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Jansen MLA, De Winde JH, Pronk JT. Hxt-carrier-mediated glucose efflux upon exposure of Saccharomyces cerevisiae to excess maltose. Appl Environ Microbiol 2002; 68:4259-65. [PMID: 12200274 PMCID: PMC124116 DOI: 10.1128/aem.68.9.4259-4265.2002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2002] [Accepted: 06/18/2002] [Indexed: 11/20/2022] Open
Abstract
When wild-type Saccharomyces cerevisiae strains pregrown in maltose-limited chemostat cultures were exposed to excess maltose, release of glucose into the external medium was observed. Control experiments confirmed that glucose release was not caused by cell lysis or extracellular maltose hydrolysis. To test the hypothesis that glucose efflux involved plasma membrane glucose transporters, experiments were performed with an S. cerevisiae strain in which all members of the hexose transporter (HXT) gene family had been eliminated and with an isogenic reference strain. Glucose efflux was virtually eliminated in the hexose-transport-deficient strain. This constitutes experimental proof that Hxt transporters facilitate export of glucose from S. cerevisiae cells. After exposure of the hexose-transport-deficient strain to excess maltose, an increase in the intracellular glucose level was observed, while the concentrations of glucose 6-phosphate and ATP remained relatively low. These results demonstrate that glucose efflux can occur as a result of uncoordinated expression of the initial steps of maltose metabolism and the subsequent reactions in glucose dissimilation. This is a relevant phenomenon for selection of maltose-constitutive strains for baking and brewing.
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Affiliation(s)
- Mickel L A Jansen
- Kluyver Laboratory of Biotechnology, Delft University of Technology, 2628 BC Delft, The Netherlands
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28
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Paiva S, Kruckeberg AL, Casal M. Utilization of green fluorescent protein as a marker for studying the expression and turnover of the monocarboxylate permease Jen1p of Saccharomyces cerevisiae. Biochem J 2002; 363:737-44. [PMID: 11964174 PMCID: PMC1222526 DOI: 10.1042/0264-6021:3630737] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Green fluorescent protein (GFP) from Aequorea victoria was used as an in vivo reporter protein when fused to the C-terminus of the Jen1 lactate permease of Saccharomyces cerevisiae. The Jen1 protein tagged with GFP is a functional lactate transporter with a cellular abundance of 1670 molecules/cell, and a catalytic-centre activity of 123 s(-1). It is expressed and tagged to the plasma membrane under induction conditions. The factors involved in proper localization and turnover of Jen1p were revealed by expression of the Jen1p-GFP fusion protein in a set of strains bearing mutations in specific steps of the secretory and endocytic pathways. The chimaeric protein Jen1p-GFP is targeted to the plasma membrane via a Sec6-dependent process; upon treatment with glucose, it is endocytosed via END3 and targeted for degradation in the vacuole. Experiments performed in a Deltadoa4 mutant strain showed that ubiquitination is associated with the turnover of the permease.
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Affiliation(s)
- Sandra Paiva
- Centro de Ciências do Ambiente, Departamento de Biologia, Universidade do Minho, 4710-057 Braga Codex, Portugal
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29
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Gandre S, Kahana C. Degradation of ornithine decarboxylase in Saccharomyces cerevisiae is ubiquitin independent. Biochem Biophys Res Commun 2002; 293:139-44. [PMID: 12054575 DOI: 10.1016/s0006-291x(02)00194-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ornithine decarboxylase (ODC), the first rate-limiting enzyme in the polyamine biosynthesis is one of the most rapidly degraded proteins in eukaryotic cells. Mammalian ODC is a notable exception to the widely accepted dogma that ubiquitination is always required for targeting a protein to degradation by the 26S proteasome. However, while it is well established that in mammalian cells degradation of ODC is ubiquitin independent, the requirement of ubiquitination for degradation of ODC in yeast cells remained undetermined. We have investigated ODC degradation in three mutant strains of Saccharomyces cerevisiae in which ubiquitin-dependent protein degradation activity is severely compromised. While yeast ODC was rapidly degraded in all these mutant strains the degradation of N-end rule substrates was inhibited. A mutant mouse ODC that fails to interact with Az was rapidly degraded in yeast cells but was stable in mammalian cells suggesting that interaction with a mammalian Az like yeast protein is not necessary for the degradation of ODC in yeast cells. Deletion analysis revealed that sequences from its unique N-terminus are involved in targeting yeast ODC to rapid degradation in yeast cells.
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Affiliation(s)
- Shilpa Gandre
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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30
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Lucero P, Moreno E, Lagunas R. Catabolite inactivation of the sugar transporters in Saccharomyces cerevisiae is inhibited by the presence of a nitrogen source. FEMS Yeast Res 2002; 1:307-14. [PMID: 12702334 DOI: 10.1111/j.1567-1364.2002.tb00049.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Saccharomyces cerevisiae uses glucose preferentially to any other carbon source and this preferential use is ensured by control mechanisms triggered by glucose. The consensus is that inactivation of sugar transporters other than glucose transporters is one of these mechanisms. This inactivation is called catabolite inactivation because of its apparent analogy with the catabolite inactivation of gluconeogenic enzymes. Recently, doubt has been cast on the role of the inactivation of the sugar transporters in controlling the use of glucose because this inactivation neither is specifically triggered by glucose nor specifically affects non-glucose sugar transporters. Based on the fact that this inactivation has been almost exclusively investigated using nitrogen-starved cells, it has been proposed that it might be due to the stimulation of the protein turnover that follows nitrogen starvation. The results obtained in this work support this possibility since they show that the presence of a nitrogen source in the medium strongly inhibited the inactivation. It is concluded that, in growing yeast cells, the contribution of the inactivation by glucose of the non-glucose sugar transporters to the preferential use of glucose is much lower than generally believed.
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Affiliation(s)
- Pilar Lucero
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas, Arturo Duperier, 4, 28029 Madrid, Spain
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31
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Omura F, Kodama Y, Ashikari T. The N-terminal domain of the yeast permease Bap2p plays a role in its degradation. Biochem Biophys Res Commun 2001; 287:1045-50. [PMID: 11587526 DOI: 10.1006/bbrc.2001.5697] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The amino acid permease Bap2p in Saccharomyces cerevisiae mediates a major part of the uptake of leucine, isoleucine, and valine from media containing a preferred nitrogen source. Although the transcriptional controls of BAP2 have been well studied, the posttranslational down-regulation mechanisms for Bap2p have not been established. Here we show that Bap2p is subject to a starvation-induced degradation upon rapamycin treatment or cultivation with proline as the sole nitrogen source. The starvation-induced degradation of Bap2p was dependent on the cellular functions of ubiquitination and endocytosis. Down-regulation of the permease required the most probable ubiquitination sites, the lysine residues situated in the N-terminal 49 residues, as well as the C-terminal domain. Furthermore, when the N-terminal domain of Bap2p was fused to the general amino acid permease Gap1p, the resultant chimeric permease became susceptible to the starvation-induced degradation, indicating that the Bap2p N-terminus contains a determinant responsive to the starvation signals.
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Affiliation(s)
- F Omura
- Institute for Fundamental Research, Suntory Ltd., 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka, 618-8503, Japan.
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32
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Dunn R, Hicke L. Multiple roles for Rsp5p-dependent ubiquitination at the internalization step of endocytosis. J Biol Chem 2001; 276:25974-81. [PMID: 11356856 DOI: 10.1074/jbc.m104113200] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ubiquitination of integral plasma membrane proteins triggers their rapid internalization into the endocytic pathway. The yeast ubiquitin ligase Rsp5p, a homologue of mammalian Nedd4 and Itch, is required for the ubiquitination and subsequent internalization of multiple plasma membrane proteins, including the alpha-factor receptor (Ste2p). Here we demonstrate that Rsp5p plays multiple roles at the internalization step of endocytosis. Temperature-sensitive rsp5 mutant cells were defective in the internalization of alpha-factor by a Ste2p-ubiquitin chimera, a receptor that does not require post-translational ubiquitination. Similarly, a modified version of Ste2p bearing a NPFXD linear peptide sequence as its only internalization signal was not internalized in rsp5 cells. Internalization of these variant receptors was dependent on the catalytic cysteine residue of Rsp5p and on ubiquitin-conjugating enzymes that bind Rsp5p. Thus, a Rsp5p-dependent ubiquitination event is required for internalization mediated by ubiquitin-dependent and -independent endocytosis signals. Constitutive Ste2p-ubiquitin internalization and fluid-phase endocytosis also required active ubiquitination machinery, including Rsp5p. These observations indicate that Rsp5p-dependent ubiquitination of a trans-acting protein component of the endocytosis machinery is required for the internalization step of endocytosis.
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Affiliation(s)
- R Dunn
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA
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33
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Wang G, McCaffery JM, Wendland B, Dupré S, Haguenauer-Tsapis R, Huibregtse JM. Localization of the Rsp5p ubiquitin-protein ligase at multiple sites within the endocytic pathway. Mol Cell Biol 2001; 21:3564-75. [PMID: 11313482 PMCID: PMC100278 DOI: 10.1128/mcb.21.10.3564-3575.2001] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae RSP5 gene encodes an essential HECT E3 ubiquitin-protein ligase. Rsp5p contains an N-terminal C2 domain, three WW domains in the central portion of the molecule, and a C-terminal catalytic HECT domain. A diverse group of substrates of Rsp5p and vertebrate C2 WW-domain-containing HECT E3s have been identified, including both nuclear and membrane-associated proteins. We determined the intracellular localization of Rsp5p and the determinants necessary for localization, in order to better understand how Rsp5p activities are coordinated. Using both green fluorescent protein fusions to Rsp5p and immunogold electron microscopy, we found that Rsp5p was distributed in a punctate pattern at the plasma membrane, corresponding to membrane invaginations that are likely sites of endosome formation, as well as at perivacuolar sites. The latter appeared to correspond to endocytic intermediates, as these structures were not seen in a sla2/end4-1 mutant, and double-immunogold labeling demonstrated colocalization of Rsp5p with the endosomal markers Pep12p and Vps32p. The C2 domain was an important determinant of localization; however, mutations that disrupted HECT domain function also caused mislocalization of Rsp5p, indicating that enzymatic activity is linked to localization. Deletion of the C2 domain partially stabilized Fur4p, a protein previously shown to undergo Rsp5p- and ubiquitin-mediated endocytosis; however, Fur4p was still ubiquitinated at the plasma membrane when the C2 domain was deleted from the protein. Together, these results indicate that Rsp5p is located at multiple sites within the endocytic pathway and suggest that Rsp5p may function at multiple steps in the ubiquitin-mediated endocytosis pathway.
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Affiliation(s)
- G Wang
- Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712-1095, USA
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34
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Horak J, Wolf DH. Glucose-induced monoubiquitination of the Saccharomyces cerevisiae galactose transporter is sufficient to signal its internalization. J Bacteriol 2001; 183:3083-8. [PMID: 11325936 PMCID: PMC95208 DOI: 10.1128/jb.183.10.3083-3088.2001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In Saccharomyces cerevisiae, the addition of glucose to cells growing on galactose induces internalization of the galactose transporter Gal2p and its subsequent proteolysis in the vacuole. Here we report that the essential step in Gal2p down-regulation is its ubiquitination through the Ubc1p-Ubc4p-Ubc5p triad of ubiquitin-conjugating enzymes and Npi1/Rsp5p ubiquitin-protein ligase. Moreover, Gal2p appears to be stabilized in mutant cells defective in the ubiquitin-hydrolase Npi2p/Doa4p, and the mutant phenotype can be reversed by overexpression of ubiquitin. An analysis of the fate of Gal2p in cells overexpressing wild-type ubiquitin as well as its variants incompetent to form polyubiquitin chains showed that monoubiquitination of Gal2p is sufficient to signal internalization of the protein into the endocytic pathway.
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Affiliation(s)
- J Horak
- Institute of Physiology, Department of Membrane Transport, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic
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35
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Abstract
Genetic and biochemical studies in yeast and animal cells have led to the identification of many components required for endocytosis. In this review, we summarize our understanding of the endocytic machinery with an emphasis on the proteins regulating the internalization step of endocytosis and endosome fusion. Even though the overall endocytic machinery appears to be conserved between yeast and animals, clear differences exist. We also discuss the roles of phosphoinositides, sterols, and sphingolipid precursors in endocytosis, because in addition to proteins, these lipids have emerged as important determinants in the spatial and most likely temporal specificity of endocytic membrane trafficking events.
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Affiliation(s)
- K D'Hondt
- Biozentrum-University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
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36
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Abstract
Multi-ubiquitin chains at least four subunits long are required for efficient recognition and degradation of ubiquitylated proteins by the proteasome, but other functions of ubiquitin have been discovered that do not involve the proteasome. Some proteins are modified by a single ubiquitin or short ubiquitin chains. Instead of sending proteins to their death through the proteasome, monoubiquitylation regulates processes that range from membrane transport to transcriptional regulation.
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Affiliation(s)
- L Hicke
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University Evanston, Illinois 60208, USA.
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37
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Omura F, Kodama Y, Ashikari T. The basal turnover of yeast branched-chain amino acid permease Bap2p requires its C-terminal tail. FEMS Microbiol Lett 2001; 194:207-14. [PMID: 11164310 DOI: 10.1111/j.1574-6968.2001.tb09471.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The branched-chain amino acid permease Bap2p is a transport system for leucine, isoleucine, and valine in Saccharomyces cerevisiae, and its synthesis is regulated transcriptionally. However, the downregulation mechanisms of Bap2p have not been established. Here we demonstrate that the C-terminal region of Bap2p plays a pivotal role in its basal turnover. Truncation of the C-terminal 29 residues caused the stabilization and accumulation in the plasma membrane of Bap2p. Furthermore, when the Bap2p C-terminal region was fused to green fluorescent protein, the fusion protein localized to the plasma membrane, suggesting the existence of a possible degradation-related acceptor site for the C-terminal tail of Bap2p.
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Affiliation(s)
- F Omura
- Institute for Fundamental Research, Suntory Ltd., 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, 618-8503, Osaka, Japan.
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38
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Marchal C, Haguenauer-Tsapis R, Urban-Grimal D. Casein kinase I-dependent phosphorylation within a PEST sequence and ubiquitination at nearby lysines signal endocytosis of yeast uracil permease. J Biol Chem 2000; 275:23608-14. [PMID: 10811641 DOI: 10.1074/jbc.m001735200] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Uracil uptake by Saccharomyces cerevisiae is mediated by the FUR4-encoded uracil permease. The modification of uracil permease by phosphorylation at the plasma membrane is a key mechanism for regulating endocytosis of this protein. This modification in turn facilitates its ubiquitination and internalization. Following endocytosis, the permease is targeted to the lysosome/vacuole for proteolysis. We have previously shown that uracil permease is phosphorylated at several serine residues within a well characterized N-terminal PEST sequence. In this report, we provide evidence that lysine residues 38 and 41, adjacent to the PEST sequence, are the target sites for ubiquitination of the permease. Conservative substitutions at both Lys(38) and Lys(41) give variant permeases that are phosphorylated but fail to internalize. The PEST sequence contains potential phosphorylation sites conforming to the consensus sequences for casein kinase 1. Casein kinase 1 (CK1) protein kinases, encoded by the redundant YCKI and YCK2 genes, are located at the plasma membrane. Either alone supports growth, but loss of function of both is lethal. Here, we show that in CK1-deficient cells, the permease is poorly phosphorylated and poorly ubiquitinated. Moreover, CK1 overproduction rescued the defective endocytosis of a mutant permease in which the serine phosphoacceptors were replaced by threonine (a less effective phosphoacceptor), which suggests that Yck activity may play a direct role in phosphorylating the permease. Permease internalization was not greatly affected in CK1-deficient cells, despite the low level of ubiquitination of the protein. This may be due to CK1 having a second counteracting role in endocytosis as shown by the higher turnover of variant permeases with unphosphorylatable versions of the PEST sequence.
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Affiliation(s)
- C Marchal
- Institut Jacques Monod, CNRS-UMRC9922, Université Paris 6 and Paris 7-Denis Diderot, 2 Place Jussieu, 75251 Paris cedex 05, France
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39
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Medintz I, Wang X, Hradek T, Michels CA. A PEST-like sequence in the N-terminal cytoplasmic domain of Saccharomyces maltose permease is required for glucose-induced proteolysis and rapid inactivation of transport activity. Biochemistry 2000; 39:4518-26. [PMID: 10758001 DOI: 10.1021/bi992455a] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Maltose permease is required for maltose transport into Saccharomyces cells. Glucose addition to maltose-fermenting cells causes selective delivery of this integral plasma membrane protein to the yeast vacuole via endocytosis for degradation by resident proteases. This glucose-induced degradation is independent of the proteasome but requires ubiquitin and certain ubiquitin conjugating enzymes. We used mutation analysis to identify target sequences in Mal61/HA maltose permease involved in its selective glucose-induced degradation. A nonsense mutation was introduced at codon 581, creating a truncated functional maltose permease. Additional missense mutations were introduced into the mal61/HA-581NS allele, altering potential phosphorylation and ubiquitination sites. No significant effect was seen on the rate of glucose-induced degradation of these mutant proteins. Deletion mutations were constructed, removing residues 2-30, 31-60, 61-90, and 49-78 of the N-terminal cytoplasmic domain, as well as a missense mutation of a dileucine motif. Results indicate that the proline-, glutamate-, aspartate-, serine-, and threonine-rich (PEST) sequence found in the N-terminal cytoplasmic domain, particularly residues 49-78, is required for glucose-induced degradation of Mal61/HAp and for the rapid glucose-induced inactivation of maltose transport activity. The decreased rate of glucose-induced degradation correlates with a decrease in the level of glucose-induced ubiquitination of the DeltaPEST mutant permease. In addition, newly synthesized mutant permease proteins lacking residues 49-78 or carrying an alteration in the dileucine motif, residues 69 and 70, are resistant to glucose-induced inactivation of maltose transport activity. This N-terminal PEST-like sequence is the target of both the Rgt2p-dependent and the Glc7p-Reg1p-dependent glucose signaling pathways.
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Affiliation(s)
- I Medintz
- Biology Department, Queens College and the Graduate School of the City University of New York, 65-30 Kissena Boulevard, Flushing, New York 11367, USA
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40
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Jiang H, Medintz I, Zhang B, Michels CA. Metabolic signals trigger glucose-induced inactivation of maltose permease in Saccharomyces. J Bacteriol 2000; 182:647-54. [PMID: 10633097 PMCID: PMC94326 DOI: 10.1128/jb.182.3.647-654.2000] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Organisms such as Saccharomyces capable of utilizing several different sugars selectively ferment glucose when less desirable carbon sources are also available. This is achieved by several mechanisms. Glucose down-regulates the transcription of genes involved in utilization of these alternate carbon sources. Additionally, it causes posttranslational modifications of enzymes and transporters, leading to their inactivation and/or degradation. Two glucose sensing and signaling pathways stimulate glucose-induced inactivation of maltose permease. Pathway 1 uses Rgt2p as a sensor of extracellular glucose and causes degradation of maltose permease protein. Pathway 2 is dependent on glucose transport and stimulates degradation of permease protein and very rapid inactivation of maltose transport activity, more rapid than can be explained by loss of protein alone. In this report, we characterize signal generation through pathway 2 using the rapid inactivation of maltose transport activity as an assay of signaling activity. We find that pathway 2 is dependent on HXK2 and to a lesser extent HXK1. The correlation between pathway 2 signaling and glucose repression suggests that these pathways share common upstream components. We demonstrate that glucose transport via galactose permease is able to stimulate pathway 2. Moreover, rapid transport and fermentation of a number of fermentable sugars (including galactose and maltose, not just glucose) are sufficient to generate a pathway 2 signal. These results indicate that pathway 2 responds to a high rate of sugar fermentation and monitors an intracellular metabolic signal. Production of this signal is not specific to glucose, glucose catabolism, glucose transport by the Hxt transporters, or glucose phosphorylation by hexokinase 1 or 2. Similarities between this yeast glucose sensing pathway and glucose sensing mechanisms in mammalian cells are discussed.
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Affiliation(s)
- H Jiang
- Biology Department, Queens College and the Graduate School of the City University of New York, Flushing, New York 11367, USA
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41
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Lucero P, Peñalver E, Vela L, Lagunas R. Monoubiquitination is sufficient to signal internalization of the maltose transporter in Saccharomyces cerevisiae. J Bacteriol 2000; 182:241-3. [PMID: 10613890 PMCID: PMC94267 DOI: 10.1128/jb.182.1.241-243.2000] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Monoubiquitination of the 12-transmembrane segment (12-TMS) Saccharomyces cerevisiae maltose transporter promoted the maximal internalization rate of this protein. This modification is similar to that of the 7-TMS alpha-factor receptor but different from that of the 12-TMS uracil and general amino acid permeases. This result shows that binding of ubiquitin-Lys63 chains is not required for maximal internalization of all 12-TMS-containing proteins.
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Affiliation(s)
- P Lucero
- Instituto de Investigaciones Biomédicas "Alberto Sols," Consejo Superior de Investigaciones Científicas, 28029 Madrid, Spain
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42
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Petersson J, Pattison J, Kruckeberg AL, Berden JA, Persson BL. Intracellular localization of an active green fluorescent protein-tagged Pho84 phosphate permease in Saccharomyces cerevisiae. FEBS Lett 1999; 462:37-42. [PMID: 10580087 DOI: 10.1016/s0014-5793(99)01471-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Green fluorescent protein (GFP) from Aequorea victoria was used as an in vivo reporter protein when fused to the carboxy-terminus of the Pho84 phosphate permease of Saccharomyces cerevisiae. Both components of the fusion protein displayed their native functions and revealed a cellular localization and degradation of the Pho84-GFP chimera consistent with the behavior of the wild-type Pho84 protein. The GFP-tagged chimera allowed for a detection of conditions under which the Pho84 transporter is localized to its functional environment, i.e. the plasma membrane, and conditions linked to relocation of the protein to the vacuole for degradation. By use of the methodology described, GFP should be useful in studies of localization and degradation also of other membrane proteins in vivo.
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Affiliation(s)
- J Petersson
- Department of Engineering and Natural Sciences, Växjö University, 351 95, Växjö, Sweden
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43
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Beaudenon SL, Huacani MR, Wang G, McDonnell DP, Huibregtse JM. Rsp5 ubiquitin-protein ligase mediates DNA damage-induced degradation of the large subunit of RNA polymerase II in Saccharomyces cerevisiae. Mol Cell Biol 1999; 19:6972-9. [PMID: 10490634 PMCID: PMC84692 DOI: 10.1128/mcb.19.10.6972] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rsp5 is an E3 ubiquitin-protein ligase of Saccharomyces cerevisiae that belongs to the hect domain family of E3 proteins. We have previously shown that Rsp5 binds and ubiquitinates the largest subunit of RNA polymerase II, Rpb1, in vitro. We show here that Rpb1 ubiquitination and degradation are induced in vivo by UV irradiation and by the UV-mimetic compound 4-nitroquinoline-1-oxide (4-NQO) and that a functional RSP5 gene product is required for this effect. The 26S proteasome is also required; a mutation of SEN3/RPN2 (sen3-1), which encodes an essential regulatory subunit of the 26S proteasome, partially blocks 4-NQO-induced degradation of Rpb1. These results suggest that Rsp5-mediated ubiquitination and degradation of Rpb1 are components of the response to DNA damage. A human WW domain-containing hect (WW-hect) E3 protein closely related to Rsp5, Rpf1/hNedd4, also binds and ubiquitinates both yeast and human Rpb1 in vitro, suggesting that Rpf1 and/or another WW-hect E3 protein mediates UV-induced degradation of the large subunit of polymerase II in human cells.
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Affiliation(s)
- S L Beaudenon
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08855, USA
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44
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Abstract
Glucose, the most abundant monosaccharide in nature, is the principal carbon and energy source for nearly all cells. The first, and rate-limiting, step of glucose metabolism is its transport across the plasma membrane. In cells of many organisms glucose ensures its own efficient metabolism by serving as an environmental stimulus that regulates the quantity, types, and activity of glucose transporters, both at the transcriptional and posttranslational levels. This is most apparent in the baker's yeast Saccharomyces cerevisiae, which has 20 genes encoding known or likely glucose transporters, each of which is known or likely to have a different affinity for glucose. The expression and function of most of these HXT genes is regulated by different levels of glucose. This review focuses on the mechanisms S. cerevisiae and a few other fungal species utilize for sensing the level of glucose and transmitting this information to the nucleus to alter HXT gene expression. One mechanism represses transcription of some HXT genes when glucose levels are high and works through the Mig1 transcriptional repressor, whose function is regulated by the Snf1-Snf4 protein kinase and Reg1-Glc7 protein phosphatase. Another pathway induces HXT expression in response to glucose and employs the Rgt1 transcriptional repressor, a ubiquitin ligase protein complex (SCF(Grr1)) that regulates Rgt1 function, and two glucose sensors in the membrane (Snf3 and Rgt2) that bind glucose and generate the intracellular signal to which Rgt1 responds. These two regulatory pathways collaborate with other, less well-understood, pathways to ensure that yeast cells express the glucose transporters best suited for the amount of glucose available.
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Affiliation(s)
- S Ozcan
- Department of Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky 40536, USA
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45
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Swaminathan S, Amerik AY, Hochstrasser M. The Doa4 deubiquitinating enzyme is required for ubiquitin homeostasis in yeast. Mol Biol Cell 1999; 10:2583-94. [PMID: 10436014 PMCID: PMC25490 DOI: 10.1091/mbc.10.8.2583] [Citation(s) in RCA: 243] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Attachment of ubiquitin to cellular proteins frequently targets them to the 26S proteasome for degradation. In addition, ubiquitination of cell surface proteins stimulates their endocytosis and eventual degradation in the vacuole or lysosome. In the yeast Saccharomyces cerevisiae, ubiquitin is a long-lived protein, so it must be efficiently recycled from the proteolytic intermediates to which it becomes linked. We identified previously a yeast deubiquitinating enzyme, Doa4, that plays a central role in ubiquitin-dependent proteolysis by the proteasome. Biochemical and genetic data suggest that Doa4 action is closely linked to that of the proteasome. Here we provide evidence that Doa4 is required for recycling ubiquitin from ubiquitinated substrates targeted to the proteasome and, surprisingly, to the vacuole as well. In the doa4Delta mutant, ubiquitin is strongly depleted under certain conditions, most notably as cells approach stationary phase. Ubiquitin depletion precedes a striking loss of cell viability in stationary phase doa4Delta cells. This loss of viability and several other defects of doa4Delta cells are rescued by provision of additional ubiquitin. Ubiquitin becomes depleted in the mutant because it is degraded much more rapidly than in wild-type cells. Aberrant ubiquitin degradation can be partially suppressed by mutation of the proteasome or by inactivation of vacuolar proteolysis or endocytosis. We propose that Doa4 helps recycle ubiquitin from both proteasome-bound ubiquitinated intermediates and membrane proteins destined for destruction in the vacuole.
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Affiliation(s)
- S Swaminathan
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA
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46
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Matĕjcková-Forejtová A, Kinclová O, Sychrová H. Degradation of Candida albicans Can1 permease expressed in Saccharomyces cerevisiae. FEMS Microbiol Lett 1999; 176:257-62. [PMID: 10418152 DOI: 10.1111/j.1574-6968.1999.tb13670.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The Candida albicans amino-acid Can1 permease expressed in Saccharomyces cerevisiae is degraded in the vacuole after internalisation by endocytosis. The CaCan1 inactivation and degradation is slow and not inducible by ammonium ions or 'stress' conditions. Using Saccharomyces cerevisiae mutants defective in ubiquitin-protein ligase and ubiquitin-protein hydrolase we have shown that the degradation of heterologous CaCan1 permease is ubiquitin dependent.
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47
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Springael JY, De Craene JO, André B. The yeast Npi1/Rsp5 ubiquitin ligase lacking its N-terminal C2 domain is competent for ubiquitination but not for subsequent endocytosis of the gap1 permease. Biochem Biophys Res Commun 1999; 257:561-6. [PMID: 10198251 DOI: 10.1006/bbrc.1999.0505] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The yeast ubiquitin ligase Npi1/Rsp5 and its mammalian homologue Nedd4 are involved in ubiquitination of various cell surface proteins, these being subsequently internalized by endocytosis and degraded in the vacuole/lysosome. Both enzymes consist of an N-terminal C2 domain, three to four successive WW(P) domains, and a C-terminal catalytic domain (HECT) containing a highly conserved cysteine residue involved in ubiquitin thioester formation. In this study, we show that the conserved cysteine of the HECT domain is required for yeast cell viability and for ubiquitination and subsequent endocytosis of the Gap1 permease. In contrast, the C2 domain of Npi1/Rsp5 is not essential to cell viability. Its deletion impairs internalization of Gap1, without detectably affecting ubiquitination of the permease. This suggests that Npi1/Rsp5 participates, via its C2 domain, in endocytosis of ubiquitinated permeases.
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Affiliation(s)
- J Y Springael
- Laboratoire de Physiologie Cellulaire et de Génétique des Levures, Université Libre de Bruxelles-Campus Plaine CP244, Bd du triomphe, Bruxelles, B-1050, Belgium
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48
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Abstract
G-protein-coupled receptors and transporters in Saccharomyces cerevisiae are modified with ubiquitin in response to ligand biding. In most cases, the proteasome does not recognize these ubiquitinated proteins. Instead, ubiquitination serves to trigger internalization and degradation of plasma membrane proteins in the lysosome-like vacuole. A number of mammalian receptors and at least one ion channel undergo ubiquitination at the plasma membrane, and this modification is required for their downregulation. Some of these cell-surface proteins appear to be degraded by both the proteasome and lysosomal proteases. Recent evidence indicates that other proteins required for receptor internalization might also be regulated by ubiquitination, suggesting that ubiquitin plays diverse roles in regulating plasma membrane protein activity.
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Affiliation(s)
- L Hicke
- Dept of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL, USA.
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