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Miao J, Williams DL, Kruppa MD, Peters BM. Glycogen synthase activity in Candida albicans is partly controlled by the functional ortholog of Saccharomyces cerevisiae Gac1p. mSphere 2024:e0057524. [PMID: 39315809 DOI: 10.1128/msphere.00575-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2024] [Accepted: 08/29/2024] [Indexed: 09/25/2024] Open
Abstract
To adapt to various host microenvironments, the human fungal pathogen Candida albicans possesses the capacity to accumulate and store glycogen as an internal carbohydrate source. In the model yeast Saccharomyces cerevisiae, ScGlc7p and ScGac1p are the serine/threonine type 1 protein phosphatase catalytic and regulatory subunits that control glycogen synthesis by altering the phosphorylation state of the glycogen synthase Gsy2p. Despite recent delineation of the glycogen synthesis pathway in C. albicans, the molecular events driving synthase activation are currently undefined. In this study, using a combination of microbiologic and genetic techniques, we determined that the protein encoded by uncharacterized gene C1_01140C, and not the currently annotated C. albicans Gac1p, is the major regulatory subunit involved in glycogen synthesis. C1_01140Cp contains a conserved GVNK motif observed across multiple starch/glycogen-binding proteins in various species, and alanine substitution of each residue in this motif significantly impaired glycogen accumulation in C. albicans. Fluorescent protein tagging and microscopy indicated that C1_01140Cp-GFPy colocalized with CaGlc7p-tdTomato and CaGsy1p-tdTomato accordingly. Co-immunoprecipitation assays further confirmed that C1_01140Cp associates with CaGlc7p and CaGsy1p during glycogen synthesis. Lastly, c1_01140cΔ/Δ exhibited colonization defects in a murine model of vulvovaginal candidiasis. Collectively, our data indicate that uncharacterized C1_01140Cp is the functional ortholog of the PPP1R subunit ScGac1p in C. albicans.IMPORTANCEThe capacity to synthesize glycogen offers microbes metabolic flexibility, including the fungal pathogen Candida albicans. In Saccharomyces cerevisiae, dephosphorylation of glycogen synthase by the ScGlc7p-containing phosphatase is a critical rate-limiting step in glycogen synthesis. Subunits, including ScGac1p, target ScGlc7p to α-1,4-glucosyl primers for efficient ScGsy2p synthase activation. However, this process in C. albicans had not been delineated. Here, we show that the C. albicans genome encodes for two homologous phosphatase-binding subunits, annotated CaGac1p and uncharacterized C1_01140Cp, both containing a GVNK motif required for polysaccharide affinity. Surprisingly, loss of CaGac1p only moderately reduced glycogen accumulation, whereas loss of C1_01140Cp ablated it. Fluorescence microscopy and co-immunoprecipitation approaches revealed that C1_01140Cp associates with CaGlc7p and CaGsy1p during glycogen synthesis. Moreover, C1_01140Cp contributed to fungal fitness at the vaginal mucosa during murine vaginitis. Therefore, this work demonstrates that glycogen synthase regulation is conserved in C. albicans and C1_01140Cp is the functional ortholog of ScGac1p.
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Affiliation(s)
- Jian Miao
- Pharmaceutical Sciences Program, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - David L Williams
- Department of Surgery, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, USA
- Center of Excellence in Inflammation, Infectious Disease, and Immunity, East Tennessee State University, Johnson City, Tennessee, USA
| | - Michael D Kruppa
- Center of Excellence in Inflammation, Infectious Disease, and Immunity, East Tennessee State University, Johnson City, Tennessee, USA
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, USA
| | - Brian M Peters
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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2
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Guindal AM, Gonzalez R, Tronchoni J, Roodink JS, Morales P. Directed evolution of Saccharomyces cerevisiae for low volatile acidity during winemaking under aerobic conditions. Food Microbiol 2023; 114:104282. [PMID: 37290870 DOI: 10.1016/j.fm.2023.104282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 03/22/2023] [Accepted: 04/05/2023] [Indexed: 06/10/2023]
Abstract
The use of yeast respiratory metabolism has been proposed as a promising approach to solve the problem of increasing ethanol content in wine, which is largely due to climate change. The use of S. cerevisiae for this purpose is mostly hampered by acetic acid overproduction generated under the necessary aerobic conditions. However, it was previously shown that a reg1 mutant, alleviated for carbon catabolite repression (CCR), showed low acetic acid production under aerobic conditions. In this work directed evolution of three wine yeast strains was performed to recover CCR-alleviated strains, expecting they will also be improved concerning volatile acidity. This was done by subculturing strains on galactose, in the presence of 2-deoxyglucose for around 140 generations. As expected, all evolved yeast populations released less acetic acid than their parental strains in grape juice, under aerobic conditions. Single clones were isolated from the evolved populations, either directly or after one cycle of aerobic fermentation. Only some clones from one of three original strains showed lower acetic acid production than their parental strain. Most clones isolated from EC1118 showed slower growth. However, even the most promising clones failed to reduce acetic acid production under aerobic conditions in bioreactors. Therefore, despite the concept of selecting low acetic acid producers by using 2-deoxyglucose as selective agent was found to be correct, especially at the population level, the recovery of strains with potential industrial utility by this experimental approach remains a challenge.
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Affiliation(s)
- Andrea M Guindal
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), Finca La Grajera, Carretera de Burgos km 6, 26007, Logroño, La Rioja, Spain.
| | - Ramon Gonzalez
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), Finca La Grajera, Carretera de Burgos km 6, 26007, Logroño, La Rioja, Spain.
| | - Jordi Tronchoni
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), Finca La Grajera, Carretera de Burgos km 6, 26007, Logroño, La Rioja, Spain; Universidad Internacional de Valencia - VIU, C/ Pintor Sorolla 21, 46002, Valencia, Spain.
| | - Jorik S Roodink
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), Finca La Grajera, Carretera de Burgos km 6, 26007, Logroño, La Rioja, Spain.
| | - Pilar Morales
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), Finca La Grajera, Carretera de Burgos km 6, 26007, Logroño, La Rioja, Spain.
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3
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Paine KM, Laidlaw KME, Evans GJO, MacDonald C. The phosphatase Glc7 controls the eisosomal response to starvation via post-translational modification of Pil1. J Cell Sci 2023; 136:jcs260505. [PMID: 37387118 PMCID: PMC10399984 DOI: 10.1242/jcs.260505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 06/22/2023] [Indexed: 07/01/2023] Open
Abstract
The yeast (Saccharomyces cerevisiae) plasma membrane (PM) is organised into specific subdomains that regulate surface membrane proteins. Surface transporters actively uptake nutrients in particular regions of the PM where they are also susceptible to substrate-induced endocytosis. However, transporters also diffuse into distinct subdomains termed eisosomes, where they are protected from endocytosis. Although most nutrient transporter populations are downregulated in the vacuole following glucose starvation, a small pool is retained in eisosomes to provide efficient recovery from starvation. We find the core eisosome subunit Pil1, a Bin, Amphiphysin and Rvs (BAR) domain protein required for eisosome biogenesis, is phosphorylated primarily by the kinase Pkh2. In response to acute glucose starvation, Pil1 is rapidly dephosphorylated. Enzyme localisation and activity screens suggest that the phosphatase Glc7 is the primary enzyme responsible for Pil1 dephosphorylation. Defects in Pil1 phosphorylation, achieved by depletion of GLC7 or expression of phospho-ablative or phospho-mimetic mutants, correlate with reduced retention of transporters in eisosomes and inefficient starvation recovery. We propose that precise post-translational control of Pil1 modulates nutrient transporter retention within eisosomes, depending on extracellular nutrient levels, to maximise recovery following starvation.
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Affiliation(s)
- Katherine M. Paine
- York Biomedical Research Institute. University of York, York YO10 5DD, UK
- Department of Biology, University of York, York YO10 5DD, UK
| | - Kamilla M. E. Laidlaw
- York Biomedical Research Institute. University of York, York YO10 5DD, UK
- Department of Biology, University of York, York YO10 5DD, UK
| | - Gareth J. O. Evans
- York Biomedical Research Institute. University of York, York YO10 5DD, UK
- Department of Biology, University of York, York YO10 5DD, UK
| | - Chris MacDonald
- York Biomedical Research Institute. University of York, York YO10 5DD, UK
- Department of Biology, University of York, York YO10 5DD, UK
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4
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Protein kinase Snf1 is involved in the proper regulation of the unfolded protein response in Saccharomyces cerevisiae. Biochem J 2015; 468:33-47. [PMID: 25730376 DOI: 10.1042/bj20140734] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Glc7 is the only catalytic subunit of the protein phosphatase type 1 in the yeast S. cerevisiae and, together with its regulatory subunits, is involved in many essential processes. Analysis of the non-essential mutants in the regulatory subunits of Glc7 revealed that the lack of Reg1, and no other subunit, causes hypersensitivity to unfolded protein response (UPR)-inducers, which was concomitant with an augmented UPR element-dependent transcriptional response. The Glc7-Reg1 complex takes part in the regulation of the yeast AMP-activated serine/threonine protein kinase Snf1 in response to glucose. We demonstrate in the present study that the observed phenotypes of reg1 mutant cells are attributable to the inappropriate activation of Snf1. Indeed, growth in the presence of limited concentrations of glucose, where Snf1 is active, or expression of active forms of Snf1 in a wild-type strain increased the sensitivity to the UPR-inducer tunicamycin. Furthermore, reg1 mutant cells showed a sustained HAC1 mRNA splicing and KAR2 mRNA levels during the recovery phase of the UPR, and dysregulation of the Ire1-oligomeric equilibrium. Finally, overexpression of protein phosphatases Ptc2 and Ptc3 alleviated the growth defect of reg1 cells under endoplasmic reticulum (ER) stress conditions. Altogether, our results reveal that Snf1 plays an important role in the attenuation of the UPR, as well as identifying the protein kinase and its effectors as possible pharmacological targets for human diseases that are associated with insufficient UPR activation.
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Stein K, Chiang HL. Exocytosis and Endocytosis of Small Vesicles across the Plasma Membrane in Saccharomyces cerevisiae. MEMBRANES 2014; 4:608-29. [PMID: 25192542 PMCID: PMC4194051 DOI: 10.3390/membranes4030608] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/02/2014] [Accepted: 08/18/2014] [Indexed: 12/14/2022]
Abstract
When Saccharomyces cerevisiae is starved of glucose, the gluconeogenic enzymes fructose-1,6-bisphosphatase (FBPase), phosphoenolpyruvate carboxykinase, isocitrate lyase, and malate dehydrogenase, as well as the non-gluconeogenic enzymes glyceraldehyde-3-phosphate dehydrogenase and cyclophilin A, are secreted into the periplasm. In the extracellular fraction, these secreted proteins are associated with small vesicles that account for more than 90% of the total number of extracellular structures observed. When glucose is added to glucose-starved cells, FBPase is internalized and associated with clusters of small vesicles in the cytoplasm. Specifically, the internalization of FBPase results in the decline of FBPase and vesicles in the extracellular fraction and their appearance in the cytoplasm. The clearance of extracellular vesicles and vesicle-associated proteins from the extracellular fraction is dependent on the endocytosis gene END3. This internalization is regulated when cells are transferred from low to high glucose. It is rapidly occurring and is a high capacity process, as clusters of vesicles occupy 10%–20% of the total volume in the cytoplasm in glucose re-fed cells. FBPase internalization also requires the VPS34 gene encoding PI3K. Following internalization, FBPase is delivered to the vacuole for degradation, whereas proteins that are not degraded may be recycled.
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Affiliation(s)
- Kathryn Stein
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Hui-Ling Chiang
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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Giardina BJ, Chiang HL. The key gluconeogenic enzyme fructose-1,6-bisphosphatase is secreted during prolonged glucose starvation and is internalized following glucose re-feeding via the non-classical secretory and internalizing pathways in Saccharomyces cerevisiae. PLANT SIGNALING & BEHAVIOR 2013; 8:24936. [PMID: 23673352 PMCID: PMC3999075 DOI: 10.4161/psb.24936] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 05/03/2013] [Accepted: 05/04/2013] [Indexed: 06/02/2023]
Abstract
In Saccharomyces cerevisia, the key gluconeogenic enzyme fructose-1,6-bisphosphatase is secreted into the periplasm during prolonged glucose starvation and is internalized into Vid/endosomes following glucose re-feeding. Fructose-1,6-bisphosphatase does not contain signal sequences required for the classical secretory and endocytic pathways. Hence, the secretion and internalization are mediated via the non-classical pathways.
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7
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Böhm S, Buchberger A. The budding yeast Cdc48(Shp1) complex promotes cell cycle progression by positive regulation of protein phosphatase 1 (Glc7). PLoS One 2013; 8:e56486. [PMID: 23418575 PMCID: PMC3572051 DOI: 10.1371/journal.pone.0056486] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 01/10/2013] [Indexed: 12/11/2022] Open
Abstract
The conserved, ubiquitin-selective AAA ATPase Cdc48 regulates numerous cellular processes including protein quality control, DNA repair and the cell cycle. Cdc48 function is tightly controlled by a multitude of cofactors mediating substrate specificity and processing. The UBX domain protein Shp1 is a bona fide substrate-recruiting cofactor of Cdc48 in the budding yeast S. cerevisiae. Even though Shp1 has been proposed to be a positive regulator of Glc7, the catalytic subunit of protein phosphatase 1 in S. cerevisiae, its cellular functions in complex with Cdc48 remain largely unknown. Here we show that deletion of the SHP1 gene results in severe growth defects and a cell cycle delay at the metaphase to anaphase transition caused by reduced Glc7 activity. Using an engineered Cdc48 binding-deficient variant of Shp1, we establish the Cdc48Shp1 complex as a critical regulator of mitotic Glc7 activity. We demonstrate that shp1 mutants possess a perturbed balance of Glc7 phosphatase and Ipl1 (Aurora B) kinase activities and show that hyper-phosphorylation of the kinetochore protein Dam1, a key mitotic substrate of Glc7 and Ipl1, is a critical defect in shp1. We also show for the first time a physical interaction between Glc7 and Shp1 in vivo. Whereas loss of Shp1 does not significantly affect Glc7 protein levels or localization, it causes reduced binding of the activator protein Glc8 to Glc7. Our data suggest that the Cdc48Shp1 complex controls Glc7 activity by regulating its interaction with Glc8 and possibly further regulatory subunits.
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Affiliation(s)
- Stefanie Böhm
- Department of Biochemistry, Biocenter, University of Würzburg, Würzburg, Germany
| | - Alexander Buchberger
- Department of Biochemistry, Biocenter, University of Würzburg, Würzburg, Germany
- * E-mail:
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8
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Alibhoy AA, Giardina BJ, Dunton DD, Chiang HL. Vps34p is required for the decline of extracellular fructose-1,6-bisphosphatase in the vacuole import and degradation pathway. J Biol Chem 2012; 287:33080-93. [PMID: 22833678 DOI: 10.1074/jbc.m112.360412] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
When Saccharomyces cerevisiae are starved of glucose for a prolonged period of time, gluconeogenic enzymes such as fructose-1,6-bisphosphatase (FBPase), malate dehydrogenase, isocitrate lyase, and phosphoenolpyruvate carboxykinase are induced. However, when glucose is added to prolonged-starved cells, these enzymes are degraded in the vacuole via the vacuole import and degradation (Vid) pathway. The Vid pathway merges with the endocytic pathway to remove intracellular and extracellular proteins simultaneously. Ultrastructural and cell extraction studies indicate that substantial amounts of FBPase were in the extracellular fraction (periplasm) during glucose starvation. FBPase levels in the extracellular fraction decreased after glucose re-feeding in wild-type cells. The decline of FBPase in the extracellular fraction was dependent on the SLA1 and ARC18 genes involved in actin polymerization and endocytosis. Moreover, the reduction of extracellular FBPase was also dependent on the VPS34 gene. VPS34 encodes the PI3 kinase and is also required for the Vid pathway. Vps34p co-localized with actin patches in prolonged-starved cells. In the absence of this gene, FBPase and the Vid vesicle protein Vid24p associated with actin patches before and after the addition of glucose. Furthermore, high levels of FBPase remained in the extracellular fraction in the Δvps34 mutant during glucose re-feeding. When the Asn-736 residue of Vps34p was mutated and when the C-terminal 11 amino acids were deleted, mutant proteins failed to co-localize with actin patches, and FBPase in the extracellular fraction did not decrease as rapidly. We suggest that VPS34 plays a critical role in the decline of extracellular FBPase in response to glucose.
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Affiliation(s)
- Abbas A Alibhoy
- Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA
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9
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Soontorngun N, Baramee S, Tangsombatvichit C, Thepnok P, Cheevadhanarak S, Robert F, Turcotte B. Genome-wide location analysis reveals an important overlap between the targets of the yeast transcriptional regulators Rds2 and Adr1. Biochem Biophys Res Commun 2012; 423:632-7. [PMID: 22687600 DOI: 10.1016/j.bbrc.2012.05.151] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 05/26/2012] [Indexed: 10/28/2022]
Abstract
Upon glucose depletion, a massive reprogramming of gene expression occurs in the yeast Saccharomyces cerevisiae for the use of alternate carbon sources such as the nonfermentable compounds ethanol and glycerol. This process is mediated by the master kinase Snf1 that controls the activity of various targets including the transcriptional regulators Cat8, Sip4 and Adr1. We have recently identified Rds2 as an additional player in this pathway. Here, we have performed genome-wide location analysis of Rds2 in cells grown in the presence of glycerol. We show that Rds2 binds to promoters of genes involved in gluconeogenesis, the glyoxylate shunt, and the TCA cycle as well as some genes encoding mitochondrial components or some involved in the stress response. Interestingly, we also detected Rds2 at the promoters of SIP4, ADR1 and HAP4 which encodes the limiting subunit of the Hap2/3/4/5 complex, a regulator of respiration. Strikingly, we observed an important overlap between the targets of Rds2 and Adr1. Finally, we provide a model to account for the complex interplay among these transcriptional regulators.
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Affiliation(s)
- Nitnipa Soontorngun
- Division of Biochemical Technology, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, 49 Tianthalay Road, Tha Kham, Bang Khuntian, Bangkok 10150, Thailand.
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10
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Castermans D, Somers I, Kriel J, Louwet W, Wera S, Versele M, Janssens V, Thevelein JM. Glucose-induced posttranslational activation of protein phosphatases PP2A and PP1 in yeast. Cell Res 2012; 22:1058-77. [PMID: 22290422 PMCID: PMC3367521 DOI: 10.1038/cr.2012.20] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The protein phosphatases PP2A and PP1 are major regulators of a variety of cellular processes in yeast and other eukaryotes. Here, we reveal that both enzymes are direct targets of glucose sensing. Addition of glucose to glucose-deprived yeast cells triggered rapid posttranslational activation of both PP2A and PP1. Glucose activation of PP2A is controlled by regulatory subunits Rts1, Cdc55, Rrd1 and Rrd2. It is associated with rapid carboxymethylation of the catalytic subunits, which is necessary but not sufficient for activation. Glucose activation of PP1 was fully dependent on regulatory subunits Reg1 and Shp1. Absence of Gac1, Glc8, Reg2 or Red1 partially reduced activation while Pig1 and Pig2 inhibited activation. Full activation of PP2A and PP1 was also dependent on subunits classically considered to belong to the other phosphatase. PP2A activation was dependent on PP1 subunits Reg1 and Shp1 while PP1 activation was dependent on PP2A subunit Rts1. Rts1 interacted with both Pph21 and Glc7 under different conditions and these interactions were Reg1 dependent. Reg1-Glc7 interaction is responsible for PP1 involvement in the main glucose repression pathway and we show that deletion of Shp1 also causes strong derepression of the invertase gene SUC2. Deletion of the PP2A subunits Pph21 and Pph22, Rrd1 and Rrd2, specifically enhanced the derepression level of SUC2, indicating that PP2A counteracts SUC2 derepression. Interestingly, the effect of the regulatory subunit Rts1 was consistent with its role as a subunit of both PP2A and PP1, affecting derepression and repression of SUC2, respectively. We also show that abolished phosphatase activation, except by reg1Δ, does not completely block Snf1 dephosphorylation after addition of glucose. Finally, we show that glucose activation of the cAMP-PKA (protein kinase A) pathway is required for glucose activation of both PP2A and PP1. Our results provide novel insight into the complex regulatory role of these two major protein phosphatases in glucose regulation.
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Affiliation(s)
- Dries Castermans
- Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KULeuven, Belgium
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11
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Alibhoy AA, Chiang HL. Vacuole import and degradation pathway: Insights into a specialized autophagy pathway. World J Biol Chem 2011; 2:239-45. [PMID: 22125667 PMCID: PMC3224871 DOI: 10.4331/wjbc.v2.i11.239] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 08/30/2011] [Accepted: 11/06/2011] [Indexed: 02/05/2023] Open
Abstract
Glucose deprivation induces the synthesis of pivotal gluconeogenic enzymes such as fructose-1,6-bisphosphatase, malate dehydrogenase, phosphoenolpyruvate carboxykinase and isocitrate lyase in Saccharomyces cerevisiae. However, following glucose replenishment, these gluconeogenic enzymes are inactivated and degraded. Studies have characterized the mechanisms by which these enzymes are inactivated in response to glucose. The site of degradation of these proteins has also been ascertained to be dependent on the duration of starvation. Glucose replenishment of short-term starved cells results in these proteins being degraded in the proteasome. In contrast, addition of glucose to cells starved for a prolonged period results in these proteins being degraded in the vacuole. In the vacuole dependent pathway, these proteins are sequestered in specialized vesicles termed vacuole import and degradation (Vid). These vesicles converge with the endocytic pathway and deliver their cargo to the vacuole for degradation. Recent studies have identified that internalization, as mediated by actin polymerization, is essential for delivery of cargo proteins to the vacuole for degradation. In addition, components of the target of rapamycin complex 1 interact with cargo proteins during glucose starvation. Furthermore, Tor1p dissociates from cargo proteins following glucose replenishment. Future studies will be needed to elaborate on the importance of internalization at the plasma membrane and the subsequent import of cargo proteins into Vid vesicles in the vacuole dependent degradation pathway.
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Affiliation(s)
- Abbas A Alibhoy
- Abbas A Alibhoy, Hui-Ling Chiang, Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, PA 17033, United States
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12
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Cannon JF. Function of protein phosphatase-1, Glc7, in Saccharomyces cerevisiae. ADVANCES IN APPLIED MICROBIOLOGY 2010; 73:27-59. [PMID: 20800758 DOI: 10.1016/s0065-2164(10)73002-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Budding yeast, Saccharomyces cerevisiae, and its close relatives are unique among eukaryotes in having a single gene, GLC7, encoding protein phosphatase-1 (PP1). This enzyme with a highly conserved amino acid sequence controls many processes in all eukaryotic cells. Therefore, the study of Glc7 function offers a unique opportunity to gain a comprehensive understanding of this critical regulatory enzyme. This review summarizes our current knowledge of how Glc7 function modulates processes in the cytoplasm and nucleus. Additionally, global Glc7 regulation is described.
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Affiliation(s)
- John F Cannon
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA.
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13
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Yan Y, Kang B. Regulation of Vid-dependent degradation of FBPase by TCO89, a component of TOR Complex 1. Int J Biol Sci 2010; 6:361-70. [PMID: 20617129 PMCID: PMC2899454 DOI: 10.7150/ijbs.6.361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/28/2010] [Indexed: 11/17/2022] Open
Abstract
A pivotal gluconeogenic enzyme in Saccharomyces cerevisuae, fructose-1, 6-bisphosphatase (FBPase) was selectively turned over in vacuole via Vid (vacuole import and degradation) dependent pathway in response to the fresh glucose after chronic glucose starvation. TCO89, a novel and unique component of Tor Complex I (TORCI), was found to physically associate with FBPase and significantly affect FBPase degradation via Vid pathway. Further investigation indicated that Δtco89 mutant strongly impaired FBPase's importing into Vid vesicles and Vid24's association with Vid vesicles. Inactivation of TORCI by rapamycin treatment strongly blocked FBPase degradation. Other components of TORCI were also found to physically associate with FBPase. The P1S mutation of FBPase, reported to block its degradation, was observed to impair the association of FBPase with TORCI components. These results implicated an important regulatory role of TCO89 and TORCI in this pathway.
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Affiliation(s)
- Yan Yan
- Intercollege Program in Genetics, College of Medicine, the Pennsylvania State University, Hershey, Pennsylvania 17033, USA.
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14
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Brown CR, Hung GC, Dunton D, Chiang HL. The TOR complex 1 is distributed in endosomes and in retrograde vesicles that form from the vacuole membrane and plays an important role in the vacuole import and degradation pathway. J Biol Chem 2010; 285:23359-70. [PMID: 20457600 DOI: 10.1074/jbc.m109.075143] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The key gluconeogenic enzyme fructose-1,6-bisphosphatase (FBPase) is induced when Saccharomyces cerevisiae are starved of glucose. However, when glucose is added to cells that have been starved for 3 days, FBPase is degraded in the vacuole. FBPase is first imported to Vid (vacuole import and degradation) vesicles, and these vesicles then merge with the endocytic pathway. In this report we show that two additional gluconeogenic enzymes, isocitrate lyase and phosphoenolpyruvate carboxykinase, were also degraded in the vacuole via the Vid pathway. These new cargo proteins and FBPase interacted with the TORC1 complex during glucose starvation. However, Tor1p was dissociated from FBPase after the addition of glucose. FBPase degradation was inhibited in cells overexpressing TOR1, suggesting that excessive Tor1p is inhibitory. Both Tco89p and Tor1p were found in endosomes coming from the plasma membrane as well as in retrograde vesicles forming from the vacuole membrane. When TORC1 was inactivated by rapamycin, FBPase degradation was inhibited. We suggest that TORC1 interacts with multiple cargo proteins destined for the Vid pathway and plays an important role in the degradation of FBPase in the vacuole.
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Affiliation(s)
- C Randell Brown
- Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA
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15
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Aging defined by a chronologic–replicative protein network in Saccharomyces cerevisiae: An interactome analysis. Mech Ageing Dev 2009; 130:444-60. [DOI: 10.1016/j.mad.2009.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 04/20/2009] [Accepted: 04/30/2009] [Indexed: 11/18/2022]
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16
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Brown CR, Chiang HL. A selective autophagy pathway that degrades gluconeogenic enzymes during catabolite inactivation. Commun Integr Biol 2009; 2:177-83. [PMID: 19513275 PMCID: PMC2686377 DOI: 10.4161/cib.7711] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 12/23/2008] [Indexed: 11/19/2022] Open
Abstract
In Saccharomyces cerevisiae, glucose starvation induces key gluconeogenic enzymes such as fructose-1,6-bisphosphatase (FBPase), malate dehydrogenase (MDH2) and phosphoenolpyruvate carboxykinase, while glucose addition inactivates these enzymes. Significant progress has been made identifying mechanisms that mediate the "catabolite inactivation" of FBPase and MDH2. For example, the site of their degradation has been shown to change, depending on the duration of starvation. When glucose is added to short-termed starved cells, these proteins are degraded in the proteasome. However, when glucose is added to long-termed starved cells, they are degraded in the vacuole by a selective autophagy pathway. For the vacuole pathway, these proteins are first imported into novel vesicles called Vid (vacuole import and degradation) vesicles. Following import, Vid vesicles merge with the endocytic pathway. Future experiments will be directed at understanding the molecular mechanisms that regulate the switch from proteasomal to vacuolar degradation and determining the site of Vid vesicle biogenesis.
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Affiliation(s)
- C Randell Brown
- Department of Cellular and Molecular Physiology; Penn State College of Medicine; Hershey, Pennsylvania USA
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17
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Abstract
In the presence of glucose, yeast undergoes an important remodelling of its metabolism. There are changes in the concentration of intracellular metabolites and in the stability of proteins and mRNAs; modifications occur in the activity of enzymes as well as in the rate of transcription of a large number of genes, some of the genes being induced while others are repressed. Diverse combinations of input signals are required for glucose regulation of gene expression and of other cellular processes. This review focuses on the early elements in glucose signalling and discusses their relevance for the regulation of specific processes. Glucose sensing involves the plasma membrane proteins Snf3, Rgt2 and Gpr1 and the glucose-phosphorylating enzyme Hxk2, as well as other regulatory elements whose functions are still incompletely understood. The similarities and differences in the way in which yeasts and mammalian cells respond to glucose are also examined. It is shown that in Saccharomyces cerevisiae, sensing systems for other nutrients share some of the characteristics of the glucose-sensing pathways.
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Affiliation(s)
- Juana M Gancedo
- Department of Metabolism and Cell Signalling, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain.
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18
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Abstract
Eukaryotic cells possess an exquisitely interwoven and fine-tuned series of signal transduction mechanisms with which to sense and respond to the ubiquitous fermentable carbon source glucose. The budding yeast Saccharomyces cerevisiae has proven to be a fertile model system with which to identify glucose signaling factors, determine the relevant functional and physical interrelationships, and characterize the corresponding metabolic, transcriptomic, and proteomic readouts. The early events in glucose signaling appear to require both extracellular sensing by transmembrane proteins and intracellular sensing by G proteins. Intermediate steps involve cAMP-dependent stimulation of protein kinase A (PKA) as well as one or more redundant PKA-independent pathways. The final steps are mediated by a relatively small collection of transcriptional regulators that collaborate closely to maximize the cellular rates of energy generation and growth. Understanding the nuclear events in this process may necessitate the further elaboration of a new model for eukaryotic gene regulation, called "reverse recruitment." An essential feature of this idea is that fine-structure mapping of nuclear architecture will be required to understand the reception of regulatory signals that emanate from the plasma membrane and cytoplasm. Completion of this task should result in a much improved understanding of eukaryotic growth, differentiation, and carcinogenesis.
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Affiliation(s)
- George M Santangelo
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS 39406-5018, USA.
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19
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Cai H, Kauffman S, Naider F, Becker JM. Genomewide screen reveals a wide regulatory network for di/tripeptide utilization in Saccharomyces cerevisiae. Genetics 2005; 172:1459-76. [PMID: 16361226 PMCID: PMC1456296 DOI: 10.1534/genetics.105.053041] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small peptides of two to six residues serve as important sources of amino acids and nitrogen required for growth by a variety of organisms. In the yeast Saccharomyces cerevisiae, the membrane transport protein Ptr2p, encoded by PTR2, mediates the uptake of di/tripeptides. To identify genes involved in regulation of dipeptide utilization, we performed a systematic, functional examination of this process in a haploid, nonessential, single-gene deletion mutant library. We have identified 103 candidate genes: 57 genes whose deletion decreased dipeptide utilization and 46 genes whose deletion enhanced dipeptide utilization. On the basis of Ptr2p-GFP expression studies, together with PTR2 expression analysis and dipeptide uptake assays, 42 genes were ascribed to the regulation of PTR2 expression, 37 genes were involved in Ptr2p localization, and 24 genes did not apparently affect Ptr2p-GFP expression or localization. The 103 genes regulating dipeptide utilization were distributed among most of the Gene Ontology functional categories, indicating a very wide regulatory network involved in transport and utilization of dipeptides in yeast. It is anticipated that further characterization of how these genes affect peptide utilization should add new insights into the global mechanisms of regulation of transport systems in general and peptide utilization in particular.
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Affiliation(s)
- Houjian Cai
- Department of Microbiology, University of Tennessee, Knoxville 37996-0845, USA
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20
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Hung GC, Brown CR, Wolfe AB, Liu J, Chiang HL. Degradation of the gluconeogenic enzymes fructose-1,6-bisphosphatase and malate dehydrogenase is mediated by distinct proteolytic pathways and signaling events. J Biol Chem 2004; 279:49138-50. [PMID: 15358789 DOI: 10.1074/jbc.m404544200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The key gluconeogenic enzyme fructose-1,6-bisphosphatase (FBPase) is subjected to catabolite inactivation and degradation when glucose-starved cells are replenished with fresh glucose. In various studies, the proteasome and the vacuole have each been reported to be the major site of FBPase degradation. Because different growth conditions were used in these studies, we examined whether variations in growth conditions could alter the site of FBPase degradation. Here, we demonstrated that FBPase was degraded outside the vacuole (most likely in the proteasome), when glucose was added to cells that were grown in low glucose media for a short period of time. By contrast, cells that were grown in the same low glucose media for longer periods of time degraded FBPase in the vacuole in response to glucose. Another gluconeogenic enzyme malate dehydrogenase (MDH2) showed the same degradation characteristics as FBPase in that the short term starvation of cells led to a non-vacuolar degradation, whereas long term starvation resulted in the vacuolar degradation of this protein. The N-terminal proline is required for the degradation of FBPase and MDH2 for both the vacuolar and non-vacuolar proteolytic pathways. The cAMP signaling pathway and the phosphorylation of glucose were needed for the vacuolar-dependent degradation of FBPase and MDH2. By contrast, the cAMP-dependent signaling pathway was not involved in the non-vacuolar degradation of these proteins, although the phosphorylation of glucose was required.
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Affiliation(s)
- Guo-Chiuan Hung
- Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA
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