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Shi H, Meng S, Qiu J, Xie S, Jiang N, Luo C, Naqvi NI, Kou Y. MoAti1 mediates mitophagy by facilitating recruitment of MoAtg8 to promote invasive growth in Magnaporthe oryzae. MOLECULAR PLANT PATHOLOGY 2024; 25:e13439. [PMID: 38483039 PMCID: PMC10938464 DOI: 10.1111/mpp.13439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 01/18/2024] [Accepted: 02/03/2024] [Indexed: 03/17/2024]
Abstract
Mitophagy is a selective autophagy for the degradation of damaged or excessive mitochondria to maintain intracellular homeostasis. In Magnaporthe oryzae, a filamentous ascomycetous fungus that causes rice blast, the most devastating disease of rice, mitophagy occurs in the invasive hyphae to promote infection. To date, only a few proteins are known to participate in mitophagy and the mechanisms of mitophagy are largely unknown in pathogenic fungi. Here, by a yeast two-hybrid screen with the core autophagy-related protein MoAtg8 as a bait, we obtained a MoAtg8 interactor MoAti1 (MoAtg8-interacting protein 1). Fluorescent observations and protease digestion analyses revealed that MoAti1 is primarily localized to the peripheral mitochondrial outer membrane and is responsible for recruiting MoAtg8 to mitochondria under mitophagy induction conditions. MoAti1 is specifically required for mitophagy, but not for macroautophagy and pexophagy. Infection assays suggested that MoAti1 is required for mitophagy in invasive hyphae during pathogenesis. Notably, no homologues of MoAti1 were found in rice and human protein databases, indicating that MoAti1 may be used as a potential target to control rice blast. By the host-induced gene silencing (HIGS) strategy, transgenic rice plants targeted to silencing MoATI1 showed enhanced resistance against M. oryzae with unchanged agronomic traits. Our results suggest that MoATI1 is required for mitophagy and pathogenicity in M. oryzae and can be used as a target for reducing rice blast.
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Affiliation(s)
- Huanbin Shi
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
| | - Shuai Meng
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
| | - Jiehua Qiu
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
| | - Shuwei Xie
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
| | - Nan Jiang
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
| | - Chaoxi Luo
- Key Lab of Horticultural Plant Biology, Ministry of Education, and College of Plant Science and TechnologyHuazhong Agricultural UniversityWuhanChina
| | - Naweed I. Naqvi
- Temasek Life Sciences Laboratory, Department of Biological SciencesNational University of SingaporeSingapore
| | - Yanjun Kou
- State Key Lab of Rice Biology and BreedingChina National Rice Research InstituteHangzhouChina
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Meyer L, Courtin B, Gomard M, Namane A, Permal E, Badis G, Jacquier A, Fromont-Racine M. eIF2A represses cell wall biogenesis gene expression in Saccharomyces cerevisiae. PLoS One 2023; 18:e0293228. [PMID: 38011112 PMCID: PMC10681259 DOI: 10.1371/journal.pone.0293228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 10/07/2023] [Indexed: 11/29/2023] Open
Abstract
Translation initiation is a complex and highly regulated process that represents an important mechanism, controlling gene expression. eIF2A was proposed as an alternative initiation factor, however, its role and biological targets remain to be discovered. To further gain insight into the function of eIF2A in Saccharomyces cerevisiae, we identified mRNAs associated with the eIF2A complex and showed that 24% of the most enriched mRNAs encode proteins related to cell wall biogenesis and maintenance. In agreement with this result, we showed that an eIF2A deletion sensitized cells to cell wall damage induced by calcofluor white. eIF2A overexpression led to a growth defect, correlated with decreased synthesis of several cell wall proteins. In contrast, no changes were observed in the transcriptome, suggesting that eIF2A controls the expression of cell wall-related proteins at a translational level. The biochemical characterization of the eIF2A complex revealed that it strongly interacts with the RNA binding protein, Ssd1, which is a negative translational regulator, controlling the expression of cell wall-related genes. Interestingly, eIF2A and Ssd1 bind several common mRNA targets and we found that the binding of eIF2A to some targets was mediated by Ssd1. Surprisingly, we further showed that eIF2A is physically and functionally associated with the exonuclease Xrn1 and other mRNA degradation factors, suggesting an additional level of regulation. Altogether, our results highlight new aspects of this complex and redundant fine-tuned regulation of proteins expression related to the cell wall, a structure required to maintain cell shape and rigidity, providing protection against harmful environmental stress.
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Affiliation(s)
- Laura Meyer
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Baptiste Courtin
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Maïté Gomard
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Abdelkader Namane
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Emmanuelle Permal
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Gwenael Badis
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Alain Jacquier
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
| | - Micheline Fromont-Racine
- Institut Pasteur, Génétique des Interactions Macromoléculaires, Centre National de la Recherche Scientifique, UMR 3525, Paris, France
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Strížová A, Šmátralová P, Chovančíková P, Machala Z, Polčic P. Defects in Mitochondrial Functions Affect the Survival of Yeast Cells Treated with Non-Thermal Plasma. Int J Mol Sci 2023; 24:ijms24119391. [PMID: 37298346 DOI: 10.3390/ijms24119391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/14/2023] [Accepted: 05/25/2023] [Indexed: 06/12/2023] Open
Abstract
Exposure of living cells to non-thermal plasma produced in various electrical discharges affects cell physiology and often results in cell death. Even though plasma-based techniques have started finding practical applications in biotechnology and medicine, the molecular mechanisms of interaction of cells with plasma remain poorly understood. In this study, the involvement of selected cellular components or pathways in plasma-induced cell killing was studied employing yeast deletion mutants. The changes in yeast sensitivity to plasma-activated water were observed in mutants with the defect in mitochondrial functions, including transport across the outer mitochondrial membrane (∆por1), cardiolipin biosynthesis (∆crd1, ∆pgs1), respiration (ρ0) and assumed signaling to the nucleus (∆mdl1, ∆yme1). Together these results indicate that mitochondria play an important role in plasma-activated water cell killing, both as the target of the damage and the participant in the damage signaling, which may lead to the induction of cell protection. On the other hand, our results show that neither mitochondria-ER contact sites, UPR, autophagy, nor proteasome play a major role in the protection of yeast cells from plasma-induced damage.
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Affiliation(s)
- Anna Strížová
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, Ilkovičova 6, 84215 Bratislava, Slovakia
| | - Paulína Šmátralová
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, Ilkovičova 6, 84215 Bratislava, Slovakia
| | - Petra Chovančíková
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, Ilkovičova 6, 84215 Bratislava, Slovakia
| | - Zdenko Machala
- Division of Environmental Physics, Faculty of Mathematics, Physics, and Informatics, Comenius University in Bratislava, Mlynská dolina F2, 84248 Bratislava, Slovakia
| | - Peter Polčic
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, Ilkovičova 6, 84215 Bratislava, Slovakia
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4
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Schuster R, Okamoto K. An overview of the molecular mechanisms of mitophagy in yeast. Biochim Biophys Acta Gen Subj 2022; 1866:130203. [PMID: 35842014 DOI: 10.1016/j.bbagen.2022.130203] [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: 10/22/2021] [Revised: 05/27/2022] [Accepted: 07/11/2022] [Indexed: 11/18/2022]
Abstract
Autophagy-dependent selective degradation of excess or damaged mitochondria, termed mitophagy, is a tightly regulated process necessary for mitochondrial quality and quantity control. Mitochondria are highly dynamic and major sites for vital cellular processes such as ATP and iron‑sulfur cluster biogenesis. Due to their pivotal roles for immunity, apoptosis, and aging, the maintenance of mitochondrial function is of utmost importance for cellular homeostasis. In yeast, mitophagy is mediated by the receptor protein Atg32 that is localized to the outer mitochondrial membrane. Upon mitophagy induction, Atg32 expression is transcriptionally upregulated, which leads to its accumulation on the mitochondrial surface and to recruitment of the autophagic machinery via its direct interaction with Atg11 and Atg8. Importantly, post-translational modifications such as phosphorylation further fine-tune the mitophagic response. This review summarizes the current knowledge about mitophagy in yeast and its connection with mitochondrial dynamics and the ubiquitin-proteasome system.
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Affiliation(s)
- Ramona Schuster
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Koji Okamoto
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Bhatia-Kissova I, Camougrand N. Mitophagy in Yeast: Decades of Research. Cells 2021; 10:3541. [PMID: 34944049 PMCID: PMC8700663 DOI: 10.3390/cells10123541] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/06/2021] [Accepted: 12/10/2021] [Indexed: 12/02/2022] Open
Abstract
Mitophagy, the selective degradation of mitochondria by autophagy, is one of the most important mechanisms of mitochondrial quality control, and its proper functioning is essential for cellular homeostasis. In this review, we describe the most important milestones achieved during almost 2 decades of research on yeasts, which shed light on the molecular mechanisms, regulation, and role of the Atg32 receptor in this process. We analyze the role of ROS in mitophagy and discuss the physiological roles of mitophagy in unicellular organisms, such as yeast; these roles are very different from those in mammals. Additionally, we discuss some of the different tools available for studying mitophagy.
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Affiliation(s)
- Ingrid Bhatia-Kissova
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 84215 Bratislava, Slovakia;
| | - Nadine Camougrand
- CNRS, UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
- Institut de Biochimie et de Génétique Cellulaires, Université de Bordeaux, UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
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6
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Ko H, Bae JH, Sung BH, Kim MJ, Park HJ, Sohn JH. Microbial production of medium chain fructooligosaccharides by recombinant yeast secreting bacterial inulosucrase. Enzyme Microb Technol 2019; 130:109364. [DOI: 10.1016/j.enzmictec.2019.109364] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/12/2019] [Accepted: 06/18/2019] [Indexed: 12/29/2022]
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Abstract
In many yeast and fungi, β-(1,3)-glucan and chitin are essential components of the cell wall, an important structure that surrounds cells and which is responsible for their mechanical protection and necessary for maintaining the cellular shape. In addition, the cell wall is a dynamic structure that needs to be remodelled along with the different phases of the fungal life cycle or in response to extracellular stimuli. Since β-(1,3)-glucan and chitin perform a central structural role in the assembly of the cell wall, it has been postulated that β-(1,3)-glucanases and chitinases should perform an important function in cell wall softening and remodelling. This review focusses on fungal glucanases and chitinases and their role during fungal morphogenesis.
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Affiliation(s)
- César Roncero
- Instituto de Biología Funcional Y Genómica (IBFG), Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Salamanca, Spain
| | - Carlos R Vázquez de Aldana
- Instituto de Biología Funcional Y Genómica (IBFG), Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Salamanca, Spain.
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Pérez-Hernández A, González M, González C, van Kan JAL, Brito N. BcSUN1, a B. cinerea SUN-Family Protein, Is Involved in Virulence. Front Microbiol 2017; 8:35. [PMID: 28163701 PMCID: PMC5247446 DOI: 10.3389/fmicb.2017.00035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/06/2017] [Indexed: 12/31/2022] Open
Abstract
BcSUN1 is a glycoprotein secreted by Botrytis cinerea, an important plant pathogen that causes severe losses in agriculture worldwide. In this work, the role of BcSUN1 in different aspects of the B. cinerea biology was studied by phenotypic analysis of Bcsun1 knockout strains. We identified BcSUN1 as the only member of the Group-I SUN family of proteins encoded in the B. cinerea genome, which is expressed both in axenic culture and during infection. BcSUN1 is also weakly attached to the cellular surface and is involved in maintaining the structure of the cell wall and/or the extracellular matrix. Disruption of the Bcsun1 gene produces different cell surface alterations affecting the production of reproductive structures and adhesion to plant surface, therefore reducing B. cinerea virulence. BcSUN1 is the first member of the SUN family reported to be involved in the pathogenesis of a filamentous fungus.
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Affiliation(s)
- Alicia Pérez-Hernández
- Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna (ULL)La Laguna, Spain
| | - Mario González
- Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna (ULL)La Laguna, Spain
| | - Celedonio González
- Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna (ULL)La Laguna, Spain
| | - Jan A. L. van Kan
- Laboratory of Phytopathology, Department of Plant Sciences, Wageningen University and Research Centre (WUR)Wageningen, Netherlands
| | - Nélida Brito
- Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna (ULL)La Laguna, Spain
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9
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Kuznetsov E, Váchová L, Palková Z. Cellular localization of Sun4p and its interaction with proteins in the yeast birth scar. Cell Cycle 2016; 15:1898-907. [PMID: 27229769 PMCID: PMC4968892 DOI: 10.1080/15384101.2016.1189043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 05/05/2016] [Accepted: 05/06/2016] [Indexed: 12/18/2022] Open
Abstract
Yeast harbor several proteins with predicted glucanase activity that are potentially involved in cell wall remodeling during different processes, including mitosis. Here, we showed that 2 of these putative glucanases, Sun4p and Dse2p, co-localize to the yeast birth scar, dependently on presence of the third glucanase, Egt2p. The absence of these glucanases results in inefficient mother-daughter cell separation. The Sun4p, Dse2p and Egt2p localize to the daughter side of the bud neck, possibly forming a complex, and are involved in the separation of the virgin daughter from the mother cell during mitosis. The formation of properly assembled birth scars that delimitate cell wall area restricted in the next budding is dependent on the presence of Aim44p and its transcriptional regulator, Swi5p. AIM44 or SWI5 deletion caused the "budding within the birth scar" phenotype, together with altered localization of the birth scar proteins Sun4p and Dse2p, indicating the impairment of birth scar protein complexes.
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Affiliation(s)
- Evgeny Kuznetsov
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Libuše Váchová
- Institute of Microbiology of the Czech Academy of Sciences, v.v.i., Prague, Czech Republic
| | - Zdena Palková
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
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10
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Robinson DG, Wang JY, Storey JD. A nested parallel experiment demonstrates differences in intensity-dependence between RNA-seq and microarrays. Nucleic Acids Res 2015; 43:e131. [PMID: 26130709 PMCID: PMC4787771 DOI: 10.1093/nar/gkv636] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 06/08/2015] [Indexed: 12/03/2022] Open
Abstract
Understanding the differences between microarray and RNA-Seq technologies for measuring gene expression is necessary for informed design of experiments and choice of data analysis methods. Previous comparisons have come to sometimes contradictory conclusions, which we suggest result from a lack of attention to the intensity-dependent nature of variation generated by the technologies. To examine this trend, we carried out a parallel nested experiment performed simultaneously on the two technologies that systematically split variation into four stages (treatment, biological variation, library preparation and chip/lane noise), allowing a separation and comparison of the sources of variation in a well-controlled cellular system, Saccharomyces cerevisiae. With this novel dataset, we demonstrate that power and accuracy are more dependent on per-gene read depth in RNA-Seq than they are on fluorescence intensity in microarrays. However, we carried out quantitative PCR validations which indicate that microarrays may demonstrate greater systematic bias in low-intensity genes than in RNA-seq.
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Affiliation(s)
- David G Robinson
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Jean Y Wang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - John D Storey
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA Center for Statistics and Machine Learning, Princeton University, Princeton, NJ 08544, USA Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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11
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Bühligen F, Rüdinger P, Fetzer I, Stahl F, Scheper T, Harms H, Müller S. Sustainability of industrial yeast serial repitching practice studied by gene expression and correlation analysis. J Biotechnol 2013; 168:718-28. [DOI: 10.1016/j.jbiotec.2013.09.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 12/24/2022]
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12
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Berner TS, Jacobsen S, Arneborg N. The impact of different ale brewer's yeast strains on the proteome of immature beer. BMC Microbiol 2013; 13:215. [PMID: 24079909 PMCID: PMC3849757 DOI: 10.1186/1471-2180-13-215] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/23/2013] [Indexed: 11/16/2022] Open
Abstract
Background It is well known that brewer’s yeast affects the taste and aroma of beer. However, the influence of brewer’s yeast on the protein composition of beer is currently unknown. In this study, changes of the proteome of immature beer, i.e. beer that has not been matured after fermentation, by ale brewer’s yeast strains with different abilities to degrade fermentable sugars were investigated. Results Beers were fermented from standard hopped wort (13° Plato) using two ale brewer’s yeast (Saccharomyces cerevisiae) strains with different attenuation degrees. Both immature beers had the same alcohol and protein concentrations. Immature beer and unfermented wort proteins were analysed by 2-DE and compared in order to determine protein changes arising from fermentation. Distinct protein spots in the beer and wort proteomes were identified using Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and MS/MS and revealed common beer proteins, such as lipid transfer proteins (LTP1 and LTP2), protein Z and amylase-protease inhibitors. During fermentation, two protein spots, corresponding to LTP2, disappeared, while three protein spots were exclusively found in beer. These three proteins, all derived from yeast, were identified as cell wall associated proteins, that is Exg1 (an exo-β-1,3-glucanase), Bgl2 (an endo-β-1,2-glucanase), and Uth1 (a cell wall biogenesis protein). Conclusion Yeast strain dependent changes in the immature beer proteome were identified, i.e. Bgl2 was present in beer brewed with KVL011, while lacking in WLP001 beer.
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Affiliation(s)
- Torben Sune Berner
- Food Microbiology, Department of Food Science, University of Copenhagen, DK-1958, Frederiksberg, Denmark.
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13
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Kuznetsov E, Kučerová H, Váchová L, Palková Z. SUN family proteins Sun4p, Uth1p and Sim1p are secreted from Saccharomyces cerevisiae and produced dependently on oxygen level. PLoS One 2013; 8:e73882. [PMID: 24040106 PMCID: PMC3770667 DOI: 10.1371/journal.pone.0073882] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/24/2013] [Indexed: 11/19/2022] Open
Abstract
The SUN family is comprised of proteins that are conserved among various yeasts and fungi, but that are absent in mammals and plants. Although the function(s) of these proteins are mostly unknown, they have been linked to various, often unrelated cellular processes such as those connected to mitochondrial and cell wall functions. Here we show that three of the four Saccharomyces cerevisiae SUN family proteins, Uth1p, Sim1p and Sun4p, are efficiently secreted out of the cells in different growth phases and their production is affected by the level of oxygen. The Uth1p, Sim1p, Sun4p and Nca3p are mostly synthesized during the growth phase of both yeast liquid cultures and colonies. Culture transition to slow-growing or stationary phases is linked with a decreased cellular concentration of Sim1p and Sun4p and with their efficient release from the cells. In contrast, Uth1p is released mainly from growing cells. The synthesis of Uth1p and Sim1p, but not of Sun4p, is repressed by anoxia. All four proteins confer cell sensitivity to zymolyase. In addition, Uth1p affects cell sensitivity to compounds influencing cell wall composition and integrity (such as Calcofluor white and Congo red) differently when growing on fermentative versus respiratory carbon sources. In contrast, Uth1p is essential for cell resistance to boric acids irrespective of carbon source. In summary, our novel findings support the hypothesis that SUN family proteins are involved in the remodeling of the yeast cell wall during the various phases of yeast culture development and under various environmental conditions. The finding that Uth1p is involved in cell sensitivity to boric acid, i.e. to a compound that is commonly used as an important antifungal in mycoses, opens up new possibilities of investigating the mechanisms of boric acid's action.
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Affiliation(s)
- Evgeny Kuznetsov
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Helena Kučerová
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
- Institute of Microbiology of the ASCR, v.v.i., Prague, Czech Republic
| | - Libuše Váchová
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
- Institute of Microbiology of the ASCR, v.v.i., Prague, Czech Republic
| | - Zdena Palková
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
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14
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Welter E, Montino M, Reinhold R, Schlotterhose P, Krick R, Dudek J, Rehling P, Thumm M. Uth1 is a mitochondrial inner membrane protein dispensable for post-log-phase and rapamycin-induced mitophagy. FEBS J 2013; 280:4970-82. [PMID: 23910823 DOI: 10.1111/febs.12468] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 07/01/2013] [Accepted: 07/19/2013] [Indexed: 01/01/2023]
Abstract
Mitochondria are turned over by an autophagic process termed mitophagy. This process is considered to remove damaged, superfluous and aged organelles. However, little is known about how defective organelles are recognized, what types of damage induce turnover, and whether an identical set of factors contributes to degradation under different conditions. Here we systematically compared the mitophagy rate and requirement for mitophagy-specific proteins during post-log-phase and rapamycin-induced mitophagy. To specifically assess mitophagy of damaged mitochondria, we analyzed cells accumulating proteins prone to degradation due to lack of the mitochondrial AAA-protease Yme1. While autophagy 32 (Atg32) was required under all tested conditions, the function of Atg33 could be partially bypassed in post-log-phase and rapamycin-induced mitophagy. Unexpectedly, we found that Uth1 was dispensable for mitophagy. A re-evaluation of its mitochondrial localization revealed that Uth1 is a protein of the inner mitochondrial membrane that is targeted by a cleavable N-terminal pre-sequence. In agreement with our functional analyses, this finding excludes a role of Uth1 as a mitochondrial surface receptor.
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Affiliation(s)
- Evelyn Welter
- Department of Cellular Biochemistry, Georg-August University, Göttingen, Germany
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15
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Patil VA, Greenberg ML. Cardiolipin-mediated cellular signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 991:195-213. [PMID: 23775697 DOI: 10.1007/978-94-007-6331-9_11] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
This review focuses on recent studies showing that cardiolipin (CL), a unique mitochondrial phospholipid, regulates many cellular functions and signaling pathways, both inside and outside the mitochondria. Inside the mitochondria, CL is a critical target of mitochondrial generated reactive oxygen species (ROS) and regulates signaling events related to apoptosis and aging. CL deficiency causes perturbation of signaling pathways outside the mitochondria, including the PKC-Slt2 cell integrity pathway and the high osmolarity glycerol (HOG) pathway, and is a key player in the cross-talk between the mitochondria and the vacuole. Understanding these connections may shed light on the pathology of Barth syndrome, a disorder of CL remodeling.
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Affiliation(s)
- Vinay A Patil
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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Orlean P. Architecture and biosynthesis of the Saccharomyces cerevisiae cell wall. Genetics 2012; 192:775-818. [PMID: 23135325 PMCID: PMC3522159 DOI: 10.1534/genetics.112.144485] [Citation(s) in RCA: 301] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 08/06/2012] [Indexed: 01/02/2023] Open
Abstract
The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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Imai K, Fujita N, Gromiha MM, Horton P. Eukaryote-wide sequence analysis of mitochondrial β-barrel outer membrane proteins. BMC Genomics 2011; 12:79. [PMID: 21272379 PMCID: PMC3045335 DOI: 10.1186/1471-2164-12-79] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 01/28/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The outer membranes of mitochondria are thought to be homologous to the outer membranes of Gram negative bacteria, which contain 100's of distinct families of β-barrel membrane proteins (BOMPs) often forming channels for transport of nutrients or drugs. However, only four families of mitochondrial BOMPs (MBOMPs) have been confirmed to date. Although estimates as high as 100 have been made in the past, the number of yet undiscovered MBOMPs is an open question. Fortunately, the recent discovery of a membrane integration signal (the β-signal) for MBOMPs gave us an opportunity to look for undiscovered MBOMPs. RESULTS We present the results of a comprehensive survey of eukaryotic protein sequences intended to identify new MBOMPs. Our search employs recent results on β-signals as well as structural information and a novel BOMP predictor trained on both bacterial and mitochondrial BOMPs. Our principal finding is circumstantial evidence suggesting that few MBOMPs remain to be discovered, if one assumes that, like known MBOMPs, novel MBOMPs will be monomeric and β-signal dependent. In addition to this, our analysis of MBOMP homologs reveals some exceptions to the current model of the β-signal, but confirms its consistent presence in the C-terminal region of MBOMP proteins. We also report a β-signal independent search for MBOMPs against the yeast and Arabidopsis proteomes. We find no good candidates MBOMPs in yeast but the Arabidopsis results are less conclusive. CONCLUSIONS Our results suggest there are no remaining MBOMPs left to discover in yeast; and if one assumes all MBOMPs are β-signal dependent, few MBOMP families remain undiscovered in any sequenced organism.
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Affiliation(s)
- Kenichiro Imai
- AIST, Computational Biology Research Center, Tokyo, Aomi 135-0064, Japan
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18
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Ritch JJ, Davidson SM, Sheehan JJ, Austriaco N. The Saccharomyces SUN gene, UTH1, is involved in cell wall biogenesis. FEMS Yeast Res 2009; 10:168-76. [PMID: 20070376 DOI: 10.1111/j.1567-1364.2009.00601.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Deletion of the Saccharomyces gene, UTH1, a founding member of the SUN family of fungal genes, has pleiotropic effects. Several phenotypes of Deltauth1 cells including their decreased levels of mitochondrial proteins, their impaired autophagic degradation of mitochondria, and their increased viability in the presence of mammalian BAX, a proapoptotic regulator localized to the mitochondria, have prompted others to propose that the Uth1p functions primarily at the mitochondria. In this report, we show that cells lacking UTH1 have more robust cell walls with higher levels of beta-d-glucan that allows them to grow in the presence of calcofluor white or sodium dodecyl sulfate, two reagents known to perturb the yeast cell wall. Moreover, these Deltauth1 cells are also significantly more resistant to spheroplast formation induced by zymolyase treatment than their wild-type counterparts. Surprisingly, our data suggest that several of the enhanced growth phenotypes of Deltauth1 cells, including their resistance to BAX-mediated toxicity, arise from a strengthened cell wall. Therefore, we propose that Uth1p's role at the cell wall and not at the mitochondria may better explain many of its effects on yeast physiology and programmed cell death.
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Affiliation(s)
- J J Ritch
- Department of Biology, Providence College, Providence, RI 02918, USA
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19
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Thomas DP, Lopez-Ribot JL, Lee SA. A proteomic analysis of secretory proteins of a pre-vacuolar mutant of Candida albicans. J Proteomics 2009; 73:342-51. [PMID: 19819358 DOI: 10.1016/j.jprot.2009.10.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 10/01/2009] [Accepted: 10/05/2009] [Indexed: 10/20/2022]
Abstract
S. cerevisiae mutants lacking VPS4 missort several vacuolar proteins to the extracellular space, including carboxypeptidase (CPY), vacuolar protease A (PrA), and vacuolar protease B (PrB). In addition, certain soluble secretory proteins, such as invertase and acid phosphatase, are missorted from the pre-vacuolar compartment (PVC) to the general secretory pathway prior to exocytosis. Although little is known about sorting of proteins via the PVC in Candida albicans, we have previously demonstrated that the C. albicans vps4Delta null mutant missorts PrA and CPY extracellularly, but fails to secrete the aspartyl proteases Sap2p and Sap4-6p. To further define the role of C. albicans VPS4 in the trafficking of pre-vacuolar proteins, we have used 2 dimensional gel electrophoresis (2-DE) and mass spectrometry techniques to study soluble proteins in the supernatants of planktonic cultures obtained from the C. albicans vps4Delta mutant compared to control strain DAY185. Results indicated that lack of VPS4 results in a decrease of canonically secreted proteins whilst having a limited effect on non-canonically secreted extracellular proteins. Four canonically secreted proteins (Cht3p, Pra1p, Mp65p and Sun41p) were identified as reduced in the supernatants from the mutant strain. We also indentified two other major consequences of lack of VPS4, likely associated with secretion defects: altered branching and biofilm formation.
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Affiliation(s)
- Derek P Thomas
- Dept. of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, United States
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20
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21
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Abstract
The Candida albicans cell wall maintains the structural integrity of the organism in addition to providing a physical contact interface with the environment. The major components of the cell wall are fibrillar polysaccharides and proteins. The proteins of the cell wall are the focus of this review. Three classes of proteins are present in the candidal cell wall. One group of proteins attach to the cell wall via a glycophosphatidylinositol remnant or by an alkali-labile linkage. A second group of proteins with N-terminal signal sequences but no covalent attachment sequences are secreted by the classical secretory pathway. These proteins may end up in the cell wall or in the extracellular space. The third group of proteins lack a secretory signal, and the pathway(s) by which they become associated with the surface is unknown. Potential constituents of the first two classes have been predicted from analysis of genome sequences. Experimental analyses have identified members of all three classes. Some members of each class selected for consideration of confirmed or proposed function, phenotypic analysis of a mutant, and regulation by growth conditions and transcription factors are discussed in more detail.
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22
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Kurischko C, Kuravi VK, Wannissorn N, Nazarov PA, Husain M, Zhang C, Shokat KM, McCaffery JM, Luca FC. The yeast LATS/Ndr kinase Cbk1 regulates growth via Golgi-dependent glycosylation and secretion. Mol Biol Cell 2008; 19:5559-78. [PMID: 18843045 DOI: 10.1091/mbc.e08-05-0455] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Saccharomyces cerevisiae Cbk1 is a LATS/Ndr protein kinase and a downstream component of the regulation of Ace2 and morphogenesis (RAM) signaling network. Cbk1 and the RAM network are required for cellular morphogenesis, cell separation, and maintenance of cell integrity. Here, we examine the phenotypes of conditional cbk1 mutants to determine the essential function of Cbk1. Cbk1 inhibition severely disrupts growth and protein secretion, and triggers the Swe1-dependent morphogenesis checkpoint. Cbk1 inhibition also delays the polarity establishment of the exocytosis regulators Rab-GTPase Sec4 and its exchange factor Sec2, but it does not interfere with actin polarity establishment. Cbk1 binds to and phosphorylates Sec2, suggesting that it regulates Sec4-dependent exocytosis. Intriguingly, Cbk1 inhibition causes a >30% decrease in post-Golgi vesicle accumulation in late secretion mutants, indicating that Cbk1 also functions upstream of Sec2-Sec4, perhaps at the level of the Golgi. In agreement, conditional cbk1 mutants mislocalize the cis-Golgi mannosyltransferase Och1, are hypersensitive to the aminoglycoside hygromycin B, and exhibit diminished invertase and Sim1 glycosylation. Significantly, the conditional lethality and hygromycin B sensitivity of cbk1 mutants are suppressed by moderate overexpression of several Golgi mannosyltransferases. These data suggest that an important function for Cbk1 and the RAM signaling network is to regulate growth and secretion via Golgi and Sec2/Sec4-dependent processes.
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Affiliation(s)
- Cornelia Kurischko
- Department of Animal Biology and the Mari Lowe Center for Comparative Oncology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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23
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Abstract
Progress in aging research is now rapid, and surprisingly, studies in a single-celled eukaryote are a driving force. The genetic modulators of replicative life span in yeast are being identified, the molecular events that accompany aging are being discovered, and the extent to which longevity pathways are conserved between yeast and multicellular eukaryotes is being tested. In this review, we provide a brief retrospective view on the development of yeast as a model for aging and then turn to recent discoveries that have pushed aging research into novel directions and also linked aging in yeast to well-developed hypotheses in mammals. Although the question of what causes aging still cannot be answered definitively, that day may be rapidly approaching.
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Affiliation(s)
- K A Steinkraus
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA.
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24
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Firon A, Aubert S, Iraqui I, Guadagnini S, Goyard S, Prévost MC, Janbon G, d'Enfert C. The SUN41 and SUN42 genes are essential for cell separation in Candida albicans. Mol Microbiol 2007; 66:1256-75. [DOI: 10.1111/j.1365-2958.2007.06011.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Shankarnarayan S, Narang SS, Malone CL, Deschenes RJ, Fassler JS. Modulation of yeast Sln1 kinase activity by the CCW12 cell wall protein. J Biol Chem 2007; 283:1962-73. [PMID: 18048366 DOI: 10.1074/jbc.m706877200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The yeast Sln1p sensor kinase is best known as an osmosensor involved in the regulation of the hyperosmolarity glycerol mitogen-activated protein kinase cascade. Down-regulation of Sln1 kinase activity occurs under hypertonic conditions and leads to phosphorylation of the Hog1p mitogen-activated protein kinase and increased osmotic stress-response gene expression. Conditions leading to kinase up-regulation include osmotic imbalance caused by glycerol retention in the glycerol channel mutant, fps1 (Tao, W., Deschenes, R. J., and Fassler, J. S. (1999) J. Biol. Chem. 274, 360-367). The hypothesis that Sln1p kinase activity is responsive to turgor was first suggested by the increased Sln1p kinase activity in mutants lacking Fps1p in which glycerol accumulation leads to water uptake. Also consistent with the turgor hypothesis is the observation that reduced turgor caused by treatment of cells with nystatin, a drug that increases membrane permeability and causes cell shrinkage, reduced Sln1p kinase activity (Tao, W., Deschenes, R. J., and Fassler, J. S. (1999) J. Biol. Chem. 274, 360-367; Reiser, V., Raitt, D. C., and Saito, H. (2003) J. Cell Biol. 161, 1035-1040). The turgor hypothesis is revisited here in the context of the identification and characterization of the cell wall gene, CCW12, as a determinant of Sln1p activity. Results of this analysis suggest that the activity of the plasma membrane localized Sln1p is affected by the presence or absence of specific outer cell wall proteins and that this effect is independent of turgor.
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26
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Hiller E, Heine S, Brunner H, Rupp S. Candida albicans Sun41p, a putative glycosidase, is involved in morphogenesis, cell wall biogenesis, and biofilm formation. EUKARYOTIC CELL 2007; 6:2056-65. [PMID: 17905924 PMCID: PMC2168408 DOI: 10.1128/ec.00285-07] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The SUN gene family has been defined in Saccharomyces cerevisiae and comprises a fungus-specific family of proteins which show high similarity in their C-terminal domains. Genes of this family are involved in different cellular processes, like DNA replication, aging, mitochondrial biogenesis, and cytokinesis. In Candida albicans the SUN family comprises two genes, SUN41 and SIM1. We demonstrate that C. albicans mutants lacking SUN41 show similar defects as found for S. cerevisiae, including defects in cytokinesis. In addition, the SUN41 mutant showed a higher sensitivity towards the cell wall-disturbing agent Congo red, whereas no difference was observed in the presence of calcofluor white. Compared to the wild type, SUN41 deletion strains exhibited a defect in biofilm formation, a reduced adherence on a Caco-2 cell monolayer, and were unable to form hyphae on solid medium under the conditions tested. Interestingly, Sun41p was found to be secreted in the medium of cells growing as blastospores as well as those forming hyphae. Our results support a function of SUN41p as a glycosidase involved in cytokinesis, cell wall biogenesis, adhesion to host tissue, and biofilm formation, indicating an important role in the host-pathogen interaction.
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Affiliation(s)
- Ekkehard Hiller
- Fraunhofer Institute for Interfacial Engineering and Biotechnology, Nobelstrasse 12, 70569 Stuttgart, Germany
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27
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Norice CT, Smith FJ, Solis N, Filler SG, Mitchell AP. Requirement for Candida albicans Sun41 in biofilm formation and virulence. EUKARYOTIC CELL 2007; 6:2046-55. [PMID: 17873081 PMCID: PMC2168420 DOI: 10.1128/ec.00314-07] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cell wall of Candida albicans lies at the crossroads of pathogenicity and therapeutics. It contributes to pathogenicity through adherence and invasion; it is the target of both chemical and immunological antifungal strategies. We have initiated a dissection of cell wall function through targeted insertional mutagenesis of cell wall-related genes. Among 25 such genes, we were unable to generate homozygous mutations in 4, and they may be essential for viability. We created homozygous mutations in the remaining 21 genes. Insertion mutations in SUN41, Orf19.5412, Orf19.1277, MSB2, Orf19.3869, and WSC1 caused hypersensitivity to the cell wall inhibitor caspofungin, while two different ecm33 insertions caused mild caspofungin resistance. Insertion mutations in SUN41 and Orf19.5412 caused biofilm defects. Through analysis of homozygous sun41Delta/sun41Delta deletion mutants and sun41Delta/sun41Delta+pSUN41-complemented strains, we verified that Sun41 is required for biofilm formation and normal caspofungin tolerance. The sun41Delta/sun41Delta mutant had altered expression of four cell wall damage response genes, thus suggesting that it suffers a cell wall structural defect. Sun41 is required for inducing disease, because the mutant was severely attenuated in mouse models of disseminated and oropharyngeal candidiasis. Although the mutant produced aberrant hyphae, it had no defect in damaging endothelial or epithelial cells, unlike many other hypha-defective mutants. We suggest that the sun41Delta/sun41Delta cell wall defect is the primary cause of its attenuated virulence. As a small fungal surface protein with predicted glucosidase activity, Sun41 represents a promising therapeutic target.
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28
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Tal R, Winter G, Ecker N, Klionsky DJ, Abeliovich H. Aup1p, a yeast mitochondrial protein phosphatase homolog, is required for efficient stationary phase mitophagy and cell survival. J Biol Chem 2006; 282:5617-24. [PMID: 17166847 DOI: 10.1074/jbc.m605940200] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autophagy is a catabolic membrane-trafficking process that occurs in all eukaryotic cells and leads to the hydrolytic degradation of cytosolic material in the vacuolar or lysosomal lumen. Mitophagy, a selective form of autophagy targeting mitochondria, is poorly understood at present. Several recent reports suggest that mitophagy is a selective process that targets damaged mitochondria, whereas other studies imply a role for mitophagy in cell death processes. In a screen for protein phosphatase homologs that functionally interact with the autophagy-dedicated protein kinase Atg1p in yeast, we have identified Aup1p, encoded by Saccharomyces cerevisiae reading frame YCR079w. Aup1p is highly similar to a family of protein phosphatase homologs in animal cells that are predicted to localize to mitochondria based on sequence analysis. Interestingly, we found that Aup1p localizes to the mitochondrial intermembrane space and is required for efficient mitophagy in stationary phase cells. Viability studies demonstrate that Aup1p is required for efficient survival of cells in prolonged stationary phase cultures, implying a pro-survival role for mitophagy under our working conditions. Our data suggest that Aup1p may be part of a signal transduction mechanism that marks mitochondria for sequestration into autophagosomes.
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Affiliation(s)
- Ruth Tal
- Department of Biochemistry and Food Science, Faculty of Agricultural, Food, and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
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29
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Kurischko C, Weiss G, Ottey M, Luca FC. A role for the Saccharomyces cerevisiae regulation of Ace2 and polarized morphogenesis signaling network in cell integrity. Genetics 2005; 171:443-55. [PMID: 15972461 PMCID: PMC1456762 DOI: 10.1534/genetics.105.042101] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 06/14/2005] [Indexed: 01/11/2023] Open
Abstract
Saccharomyces cerevisiae RAM is a conserved signaling network that regulates maintenance of polarized growth and daughter-cell-specific transcription, the latter of which is critical for septum degradation. Consequently, cells defective in RAM function (designated ramDelta) are round in morphology, form feeble mating projections, and fail to separate following cytokinesis. It was recently demonstrated that RAM genes are essential in strains containing functional SSD1 (SSD1-v), which encodes a protein of unknown function that binds the RAM Cbk1p kinase. Here we investigated the essential function of RAM in SSD1-v strains and identified two functional groups of dosage suppressors for ramDelta lethality. We establish that all ramDelta mutants exhibit cell integrity defects and cell lysis. All dosage suppressors rescue the lysis but not the cell polarity or cell separation defects of ramDelta cells. One class of dosage suppressors is composed of genes encoding cell wall proteins, indicating that alterations in cell wall structure can rescue the cell lysis in ramDelta cells. Another class of ramDelta dosage suppressors is composed of ZRG8 and SRL1, which encode two unrelated proteins of unknown function. We establish that ZRG8 and SRL1 share similar genetic interactions and phenotypes. Significantly, Zrg8p coprecipitates with Ssd1p, localizes similarly to RAM proteins, and is dependent on RAM for localization. Collectively, these data indicate that RAM and Ssd1p function cooperatively to control cell integrity and suggest that Zrg8p and Srl1p function as nonessential inhibitors of Ssd1p.
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Affiliation(s)
- Cornelia Kurischko
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, 19104, USA
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30
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Lu JMY, Deschenes RJ, Fassler JS. Role for the Ran binding protein, Mog1p, in Saccharomyces cerevisiae SLN1-SKN7 signal transduction. EUKARYOTIC CELL 2005; 3:1544-56. [PMID: 15590828 PMCID: PMC539023 DOI: 10.1128/ec.3.6.1544-1556.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Yeast Sln1p is an osmotic stress sensor with histidine kinase activity. Modulation of Sln1 kinase activity in response to changes in the osmotic environment regulates the activity of the osmotic response mitogen-activated protein kinase pathway and the activity of the Skn7p transcription factor, both important for adaptation to changing osmotic stress conditions. Many aspects of Sln1 function, such as how kinase activity is regulated to allow a rapid response to the continually changing osmotic environment, are not understood. To gain insight into Sln1p function, we conducted a two-hybrid screen to identify interactors. Mog1p, a protein that interacts with the yeast Ran1 homolog, Gsp1p, was identified in this screen. The interaction with Mog1p was characterized in vitro, and its importance was assessed in vivo. mog1 mutants exhibit defects in SLN1-SKN7 signal transduction and mislocalization of the Skn7p transcription factor. The requirement for Mog1p in normal localization of Skn7p to the nucleus does not fully account for the mog1-related defects in SLN1-SKN7 signal transduction, raising the possibility that Mog1p may play a role in Skn7 binding and activation of osmotic response genes.
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Affiliation(s)
- Jade Mei-Yeh Lu
- Department of Biological Sciences, University of Iowa, 202 BBE, Iowa City, IA 52242, USA
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31
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Tanay A, Steinfeld I, Kupiec M, Shamir R. Integrative analysis of genome-wide experiments in the context of a large high-throughput data compendium. Mol Syst Biol 2005; 1:2005.0002. [PMID: 16729037 PMCID: PMC1681453 DOI: 10.1038/msb4100005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 02/24/2005] [Indexed: 12/21/2022] Open
Abstract
Biological systems are orchestrated by heterogeneous regulatory programs that control complex processes and adapt to a dynamic environment. Recent advances in high-throughput experimental methods provide genome-wide perspectives on such regulatory programs. A considerable amount of data on the behavior of model systems in a variety of conditions is rapidly accumulating. Still, the dominant paradigm is to analyze new genome-wide experiments separately from any other extant data, for example, by clustering the new data alone. Here we introduce a new methodology for analyzing the results of a new functional genomic study vis-à-vis a large compendium of previously published results from heterogeneous experimental techniques. We demonstrate our methodology on Saccharomyces cerevisiae, using a compendium of some 2000 experiments from 60 different publications. Most importantly, we show how the integrated analysis reveals unexpected connections among biological processes, and differentiates between novel and known effects in the analyzed experiments. Such characterization is impossible when new data sets are studied in isolation. Our results exemplify the power of the integrative approach in the analysis of genomic scale data sets and call for a paradigm shift in their study.
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Affiliation(s)
- Amos Tanay
- School of Computer Science, Tel Aviv University, Tel Aviv, Israel.
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32
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Camougrand N, Kissová I, Velours G, Manon S. Uth1p: a yeast mitochondrial protein at the crossroads of stress, degradation and cell death. FEMS Yeast Res 2005; 5:133-40. [PMID: 15489196 DOI: 10.1016/j.femsyr.2004.05.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2004] [Revised: 03/30/2004] [Accepted: 05/06/2004] [Indexed: 12/31/2022] Open
Abstract
UTH1 is a yeast aging gene that has been identified on the basis of stress resistance and longer life span of mutants. It was also shown to participate in mitochondrial biogenesis. The absence of Uth1p was found to trigger resistance to autophagy induced by rapamycin. Uth1p is therefore the first mitochondrial protein proven to be required for the autophagic degradation of mitochondria. Since this protein is also involved in yeast cell death induced by heterologous expression of the pro-apoptotic protein Bax, the results are discussed in the light of evidence suggesting a co-regulation of apoptosis and autophagy in mammalian cells.
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Affiliation(s)
- Nadine Camougrand
- Institut de Biochimie et Genetique, Cellulaires du CNRS, UMR5095 CNRS/Université de Bordeaux 2, 1 rue Camille Saint Saens, 33077 Bordeaux Cedex, France.
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33
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Alonso-Nuñez ML, An H, Martín-Cuadrado AB, Mehta S, Petit C, Sipiczki M, del Rey F, Gould KL, de Aldana CRV. Ace2p controls the expression of genes required for cell separation in Schizosaccharomyces pombe. Mol Biol Cell 2005; 16:2003-17. [PMID: 15689498 PMCID: PMC1073678 DOI: 10.1091/mbc.e04-06-0442] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Schizosaccharomyces pombe cells divide by medial fission through contraction of an actomyosin ring and deposition of a multilayered division septum that must be cleaved to release the two daughter cells. Here we describe the identification of seven genes (adg1(+), adg2(+), adg3(+), cfh4(+), agn1(+), eng1(+), and mid2(+)) whose expression is induced by the transcription factor Ace2p. The expression of all of these genes varied during the cell cycle, maximum transcription being observed during septation. At least three of these proteins (Eng1p, Agn1p, and Cfh4p) localize to a ring-like structure that surrounds the septum region during cell separation. Deletion of the previously uncharacterized genes was not lethal to the cells, but produced defects or delays in cell separation to different extents. Electron microscopic observation of mutant cells indicated that the most severe defect is found in eng1Delta agn1Delta cells, lacking the Eng1p endo-beta-1,3-glucanase and the Agn1p endo-alpha-glucanase. The phenotype of this mutant closely resembled that of ace2Delta mutants, forming branched chains of cells. This suggests that these two proteins are the main activities required for cell separation to be completed.
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Affiliation(s)
- Maria Luisa Alonso-Nuñez
- Departamento de Microbiología y Genética, Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca, Campus Miguel de Unamuno, Spain
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34
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Phadnis N, Ayres Sia E. Role of the Putative Structural Protein Sed1p in Mitochondrial Genome Maintenance. J Mol Biol 2004; 342:1115-29. [PMID: 15351639 DOI: 10.1016/j.jmb.2004.07.096] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Revised: 07/08/2004] [Accepted: 07/22/2004] [Indexed: 11/17/2022]
Abstract
The nuclear gene MIP1 encodes the mitochondrial DNA polymerase responsible for replicating the mitochondrial genome in Saccharomyces cerevisiae. A number of other factors involved in replicating and segregating the mitochondrial genome are yet to be identified. Here, we report that a bacterial two-hybrid screen using the mitochondrial polymerase, Mip1p, as bait identified the yeast protein Sed1p. Sed1p is a cell surface protein highly expressed in the stationary phase. We find that several modified forms of Sed1p are expressed and the largest of these forms interacts with the mitochondrial polymerase in vitro. Deletion of SED1 causes a 3.5-fold increase in the rate of mitochondrial DNA point mutations as well as a 4.3-fold increase in the rate of loss of respiration. In contrast, we see no change in the rate of nuclear point mutations indicating the specific role of Sed1p function in mitochondrial genome stability. Indirect immunofluorescence analysis of Sed1p localization shows that Sed1p is targeted to the mitochondria. Moreover, Sed1p is detected in purified mitochondrial fractions and the localization to the mitochondria of the largest modified form is insensitive to the action of proteinase K. Deletion of the sed1 gene results in a reduction in the quantity of Mip1p and also affects the levels of a mitochondrially-expressed protein, Cox3p. Our results point towards a role for Sed1p in mitochondrial genome maintenance.
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Affiliation(s)
- Naina Phadnis
- Department of Biology, University of Rochester, Rochester, NY 14627-0211, USA
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Kissová I, Deffieu M, Manon S, Camougrand N. Uth1p is involved in the autophagic degradation of mitochondria. J Biol Chem 2004; 279:39068-74. [PMID: 15247238 DOI: 10.1074/jbc.m406960200] [Citation(s) in RCA: 319] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The absence of the outer mitochondrial membrane protein Uth1p was found to induce resistance to rapamycin treatment and starvation, two conditions that induce the autophagic process. Biochemical studies showed the onset of a fully active autophagic activity both in wild-type and Deltauth1 strains. On the other hand, the disorganization of the mitochondrial network induced by rapamycin treatment or 15 h of nitrogen starvation was followed in cells expressing mitochondria-targeted green fluorescent protein; a rapid colocalization of green fluorescent protein fluorescence with vacuole-selective FM4-64 labeling was observed in the wild-type but not in the Deltauth1 strain. Degradation of mitochondrial proteins, followed by Western blot analysis, did not occur in mutant strains carrying null mutations of the vacuolar protease Pep4p, the autophagy-specific protein Atg5p, and Uth1p. These data show that, although the autophagic machinery was fully functional in the absence of Uth1p, this protein is involved in the autophagic degradation of mitochondria.
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Affiliation(s)
- Ingrid Kissová
- Unité Mixte de Recherche 5095 CNRS, Université de Bordeaux 2, 33077 Bordeaux, France
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Priault M, Camougrand N, Kinnally KW, Vallette FM, Manon S. Yeast as a tool to study Bax/mitochondrial interactions in cell death. FEMS Yeast Res 2003; 4:15-27. [PMID: 14554193 DOI: 10.1016/s1567-1356(03)00143-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae has proven to be a powerful tool in investigations of the molecular aspects of the events involved in apoptosis, particularly the steps implicating mitochondria. Yeast does not have obvious homologs of the proteins involved in the regulation of apoptosis, and provides a simplified model system in which the function of these proteins can be unraveled. This review focuses on the interactions of two of the major pro-apoptotic Bcl-2 family members, Bax and Bid, with mitochondria. It is shown that yeast has allowed questioning of several crucial aspects of the function of these two proteins, namely the molecular mechanisms driving their insertion into the mitochondrial outer membrane and those leading to the permeabilization to cytochrome c. More recently, signaling pathways leading to Bax-induced cell death, as well as other forms of cell death, have been identified in yeast. Both 'apoptosis-like' and autophagy-related forms of cell degradation are involved, and mitochondria play a central role in these two signaling pathways.
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Affiliation(s)
- Muriel Priault
- IBGC/CNRS, 1 Rue Camille Saint-Saëns, Université de Bordeaux 2, F-33077 Bordeaux, France
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Camougrand N, Grelaud-Coq A, Marza E, Priault M, Bessoule JJ, Manon S. The product of the UTH1 gene, required for Bax-induced cell death in yeast, is involved in the response to rapamycin. Mol Microbiol 2003; 47:495-506. [PMID: 12519199 DOI: 10.1046/j.1365-2958.2003.03311.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A yeast mutant was isolated that was resistant to Bax-induced cell death. It supports a mutation leading to decreased amounts of the protein Uth1p. A strain in which the UTH1 gene is disrupted also exhibits resistance to Bax expression. The absence of Uth1p does not change the mitochondrial localization of Bax, its insertion in the mitochondrial outer membrane or its cytochrome c-releasing activity. On the other hand, the absence of Uth1p does prevent the appearance of other hallmarks related to Bax expression in yeast, such as oxidation of mitochondrial lipid, production of reactive oxygen species and maintenance of plasma membrane properties after ethanol stress. The absence of Uth1p was also found to induce resistance to rapamycin, a specific inducer of autophagy. This resistance only appears when cells are grown under respiratory conditions, but not under fermentative conditions, suggesting that Uth1p acts in an autophagic pathway involving mitochondria, in accordance with its main localization in the outer mitochondrial membrane. Taken together, these data show that Bax is able to activate a death pathway related to autophagy in yeast, which also exhibits typical hallmarks of apoptosis, revealing a possible dual function of Bax in both types of death. This hypothesis is discussed in the light of observations suggesting a co-regulation of apoptosis and autophagy in mammalian cells.
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