1
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Bosch-Guiteras N, van Leeuwen J. Exploring conditional gene essentiality through systems genetics approaches in yeast. Curr Opin Genet Dev 2022; 76:101963. [PMID: 35939967 DOI: 10.1016/j.gde.2022.101963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 06/25/2022] [Accepted: 07/04/2022] [Indexed: 11/25/2022]
Abstract
An essential gene encodes for a cellular function that is required for viability. Although viability is a straightforward phenotype to analyze in yeast, defining a gene as essential is not always trivial. Gene essentiality has generally been studied in specific laboratory strains and under standard growth conditions, however, essentiality can vary across species, strains, and environments. Recent systematic studies of gene essentiality revealed that two sets of essential genes exist: core essential genes that are always required for viability and conditional essential genes that vary in essentiality in different genetic and environmental contexts. Here, we review recent advances made in the systematic analysis of gene essentiality in yeast and discuss the properties that distinguish core from context-dependent essential genes.
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Affiliation(s)
| | - Jolanda van Leeuwen
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
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2
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Longo LVG, Goodyear EG, Zhang S, Kudryashova E, Wu JQ. Involvement of Smi1 in cell wall integrity and glucan synthase Bgs4 localization during fission yeast cytokinesis. Mol Biol Cell 2021; 33:ar17. [PMID: 34910579 PMCID: PMC9236143 DOI: 10.1091/mbc.e21-04-0214] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cytokinesis is the final step of the cell-division cycle. In fungi, it relies on the coordination of constriction of an actomyosin contractile ring and construction of the septum at the division site. Glucan synthases synthesize glucans, which are the major components in fungal cell walls and division septa. It is known that Rho1 and Rho2 GTPases regulate glucan synthases Bgs1, Bgs4, and Ags1, and that Sbg1 and the F-BAR protein Cdc15 play roles in Bgs1 stability and delivery to the plasma membrane. Here we characterize Smi1, an intrinsically disordered protein that interacts with Bgs4 and regulates its trafficking and localization in fission yeast. Smi1 is important for septum integrity, and its absence causes severe lysis during cytokinesis. Smi1 localizes to secretory vesicles and moves together with Bgs4 toward the division site. The concentrations of the glucan synthases Bgs1 and Bgs4 and the glucanases Agn1 and Bgl2 decrease at the division site in the smi1 mutant, but Smi1 seems to be more specific to Bgs4. Mistargeting of Smi1 to mitochondria mislocalizes Bgs4 but not Bgs1. Together, our data reveal a novel regulator of glucan synthases and glucanases, Smi1, which is more important for Bgs4 trafficking, stability, and localization during cytokinesis.
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Affiliation(s)
- Larissa V G Longo
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210
| | - Evelyn G Goodyear
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210
| | - Sha Zhang
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Jian-Qiu Wu
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210.,Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio 43210
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3
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Moro S, Moscoso-Romero E, Poddar A, Mulet JM, Perez P, Chen Q, Valdivieso MH. Exomer Is Part of a Hub Where Polarized Secretion and Ionic Stress Connect. Front Microbiol 2021; 12:708354. [PMID: 34349749 PMCID: PMC8326576 DOI: 10.3389/fmicb.2021.708354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 06/18/2021] [Indexed: 11/13/2022] Open
Abstract
Plasma membrane and membranous organelles contribute to the physiology of the Eukaryotic cell by participating in vesicle trafficking and the maintenance of ion homeostasis. Exomer is a protein complex that facilitates vesicle transport from the trans-Golgi network to the plasma membrane, and its absence leads to the retention of a set of selected cargoes in this organelle. However, this retention does not explain all phenotypes observed in exomer mutants. The Schizosaccharomyces pombe exomer is composed of Cfr1 and Bch1, and cfr1Δ and bch1Δ were sensitive to high concentrations of potassium salts but not sorbitol, which showed sensitivity to ionic but not osmotic stress. Additionally, the activity of the plasma membrane ATPase was higher in exomer mutants than in the wild-type, pointing to membrane hyperpolarization, which caused an increase in intracellular K+ content and mild sensitivity to Na+, Ca2+, and the aminoglycoside antibiotic hygromycin B. Moreover, in response to K+ shock, the intracellular Ca2+ level of cfr1Δ cells increased significantly more than in the wild-type, likely due to the larger Ca2+ spikes in the mutant. Microscopy analyses showed a defective endosomal morphology in the mutants. This was accompanied by an increase in the intracellular pools of the K+ exporting P-type ATPase Cta3 and the plasma membrane Transient Receptor Potential (TRP)-like Ca2+ channel Pkd2, which were partially diverted from the trans-Golgi network to the prevacuolar endosome. Despite this, most Cta3 and Pkd2 were delivered to the plasma membrane at the cell growing sites, showing that their transport from the trans-Golgi network to the cell surface occurred in the absence of exomer. Nevertheless, shortly after gene expression in the presence of KCl, the polarized distribution of Cta3 and Pkd2 in the plasma membrane was disturbed in the mutants. Finally, the use of fluorescent probes suggested that the distribution and dynamics of association of some lipids to the plasma membrane in the presence of KCl were altered in the mutants. Thus, exomer participation in the response to K+ stress was multifaceted. These results supported the notion that exomer plays a general role in protein sorting at the trans-Golgi network and in polarized secretion, which is not always related to a function as a selective cargo adaptor.
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Affiliation(s)
- Sandra Moro
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas, Salamanca, Spain.,Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain
| | - Esteban Moscoso-Romero
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas, Salamanca, Spain.,Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain
| | - Abhishek Poddar
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - Jose M Mulet
- Instituto de Biología Molecular y Celular de Plantas, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Pilar Perez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas, Salamanca, Spain
| | - Qian Chen
- Department of Biological Sciences, University of Toledo, Toledo, OH, United States
| | - M-Henar Valdivieso
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas, Salamanca, Spain.,Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain
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4
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Yanguas F, Valdivieso MH. Analysis of the SNARE Stx8 recycling reveals that the retromer-sorting motif has undergone evolutionary divergence. PLoS Genet 2021; 17:e1009463. [PMID: 33788833 PMCID: PMC8041195 DOI: 10.1371/journal.pgen.1009463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 04/12/2021] [Accepted: 03/03/2021] [Indexed: 11/25/2022] Open
Abstract
Fsv1/Stx8 is a Schizosaccharomyces pombe protein similar to mammalian syntaxin 8. stx8Δ cells are sensitive to salts, and the prevacuolar endosome (PVE) is altered in stx8Δ cells. These defects depend on the SNARE domain, data that confirm the conserved function of syntaxin8 and Stx8 in vesicle fusion at the PVE. Stx8 localizes at the trans-Golgi network (TGN) and the prevacuolar endosome (PVE), and its recycling depends on the retromer component Vps35, and on the sorting nexins Vps5, Vps17, and Snx3. Several experimental approaches demonstrate that Stx8 is a cargo of the Snx3-retromer. Using extensive truncation and alanine scanning mutagenesis, we identified the Stx8 sorting signal. This signal is an IEMeaM sequence that is located in an unstructured protein region, must be distant from the transmembrane (TM) helix, and where the 133I, 134E, 135M, and 138M residues are all essential for recycling. This sorting motif is different from those described for most retromer cargoes, which include aromatic residues, and resembles the sorting motif of mammalian polycystin-2 (PC2). Comparison of Stx8 and PC2 motifs leads to an IEMxx(I/M) consensus. Computer-assisted screening for this and for a loose Ψ(E/D)ΨXXΨ motif (where Ψ is a hydrophobic residue with large aliphatic chain) shows that syntaxin 8 and PC2 homologues from other organisms bear variation of this motif. The phylogeny of the Stx8 sorting motifs from the Schizosaccharomyces species shows that their divergence is similar to that of the genus, showing that they have undergone evolutionary divergence. A preliminary analysis of the motifs in syntaxin 8 and PC2 sequences from various organisms suggests that they might have also undergone evolutionary divergence, what suggests that the presence of almost-identical motifs in Stx8 and PC2 might be a case of convergent evolution. Eukaryotes possess membranous intracellular compartments, whose communication is essential for cellular homeostasis. Protein complexes that facilitate the generation, transport, and fusion of coated vesicles mediate this communication. Since alterations in these processes lead to human disease, their characterization is of biological and medical interest. Retromer is a protein complex that facilitates retrograde trafficking from the prevacuolar endosome to the Golgi, being essential for the functionality of the endolysosomal system. SNAREs are required for vesicle fusion and, after facilitating membrane merging, are supposed to return to their donor organelle for new rounds of fusion. However, little is known about this recycling. We have found that Stx8, a fungal SNARE similar to human syntaxin 8, is a retromer cargo, and have identified its retromer binding motif. Sequence screening and comparison has determined that this sorting motif is conserved mainly in fungal Stx8 sequences. Notably, this motif is similar to the retromer sorting motif that is present in a family of vertebrate ion transporters. Our initial phylogenetic analyses suggest that, although retromer and some of its cargoes are conserved, the sorting motif in the cargoes might have undergone evolutionary divergence.
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Affiliation(s)
- Francisco Yanguas
- Departamento de Microbiología y Genética, Universidad de Salamanca. Salamanca. Spain
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC). Salamanca. Spain
| | - M.-Henar Valdivieso
- Departamento de Microbiología y Genética, Universidad de Salamanca. Salamanca. Spain
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas (CSIC). Salamanca. Spain
- * E-mail:
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5
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Degreif D, Cucu B, Budin I, Thiel G, Bertl A. Lipid determinants of endocytosis and exocytosis in budding yeast. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:1005-1016. [DOI: 10.1016/j.bbalip.2019.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/23/2019] [Accepted: 03/18/2019] [Indexed: 01/10/2023]
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6
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Pérez P, Cortés JC, Cansado J, Ribas JC. Fission yeast cell wall biosynthesis and cell integrity signalling. ACTA ACUST UNITED AC 2018; 4:1-9. [PMID: 32743131 PMCID: PMC7388972 DOI: 10.1016/j.tcsw.2018.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 10/04/2018] [Accepted: 10/09/2018] [Indexed: 02/02/2023]
Abstract
The cell wall is a structure external to the plasma membrane that is essential for the survival of the fungi. This polysaccharidic structure confers resistance to the cell internal turgor pressure and protection against mechanical injury. The fungal wall is also responsible for the shape of these organisms due to different structural polysaccharides, such as β-(1,3)-glucan, which form fibers and confer rigidity to the cell wall. These polysaccharides are not present in animal cells and therefore they constitute excellent targets for antifungal chemotherapies. Cell wall damage leads to the activation of MAPK signaling pathways, which respond to the damage by activating the repair of the wall and the maintenance of the cell integrity. Fission yeast Schizosaccharomyces pombe is a model organism for the study morphogenesis, cell wall, and how different inputs might regulate this structure. We present here a short overview of the fission yeast wall composition and provide information about the main biosynthetic activities that assemble this cell wall. Additionally, we comment the recent advances in the knowledge of the cell wall functions and discuss the role of the cell integrity MAPK signaling pathway in the regulation of fission yeast wall.
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Affiliation(s)
- Pilar Pérez
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas and Universidad de Salamanca, 37007 Salamanca, Spain
- Corresponding author.
| | - Juan C.G. Cortés
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas and Universidad de Salamanca, 37007 Salamanca, Spain
| | - Jose Cansado
- Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071 Murcia, Spain
| | - Juan C. Ribas
- Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas and Universidad de Salamanca, 37007 Salamanca, Spain
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7
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Zhu YH, Hyun J, Pan YZ, Hopper JE, Rizo J, Wu JQ. Roles of the fission yeast UNC-13/Munc13 protein Ync13 in late stages of cytokinesis. Mol Biol Cell 2018; 29:2259-2279. [PMID: 30044717 PMCID: PMC6249806 DOI: 10.1091/mbc.e18-04-0225] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cytokinesis is a complicated yet conserved step of the cell-division cycle that requires the coordination of multiple proteins and cellular processes. Here we describe a previously uncharacterized protein, Ync13, and its roles during fission yeast cytokinesis. Ync13 is a member of the UNC-13/Munc13 protein family, whose animal homologues are essential priming factors for soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex assembly during exocytosis in various cell types, but no roles in cytokinesis have been reported. We find that Ync13 binds to lipids in vitro and dynamically localizes to the plasma membrane at cell tips during interphase and at the division site during cytokinesis. Deletion of Ync13 leads to defective septation and exocytosis, uneven distribution of cell-wall enzymes and components of cell-wall integrity pathway along the division site and massive cell lysis during cell separation. Interestingly, loss of Ync13 compromises endocytic site selection at the division plane. Collectively, we find that Ync13 has a novel function as an UNC-13/Munc13 protein in coordinating exocytosis, endocytosis, and cell-wall integrity during fission yeast cytokinesis.
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Affiliation(s)
- Yi-Hua Zhu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Joanne Hyun
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Yun-Zu Pan
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - James E Hopper
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Jian-Qiu Wu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210
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8
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Esher SK, Ost KS, Kohlbrenner MA, Pianalto KM, Telzrow CL, Campuzano A, Nichols CB, Munro C, Wormley FL, Alspaugh JA. Defects in intracellular trafficking of fungal cell wall synthases lead to aberrant host immune recognition. PLoS Pathog 2018; 14:e1007126. [PMID: 29864141 PMCID: PMC6002136 DOI: 10.1371/journal.ppat.1007126] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 06/14/2018] [Accepted: 05/29/2018] [Indexed: 11/19/2022] Open
Abstract
The human fungal pathogen, Cryptococcus neoformans, dramatically alters its cell wall, both in size and composition, upon entering the host. This cell wall remodeling is essential for host immune avoidance by this pathogen. In a genetic screen for mutants with changes in their cell wall, we identified a novel protein, Mar1, that controls cell wall organization and immune evasion. Through phenotypic studies of a loss-of-function strain, we have demonstrated that the mar1Δ mutant has an aberrant cell surface and a defect in polysaccharide capsule attachment, resulting in attenuated virulence. Furthermore, the mar1Δ mutant displays increased staining for exposed cell wall chitin and chitosan when the cells are grown in host-like tissue culture conditions. However, HPLC analysis of whole cell walls and RT-PCR analysis of cell wall synthase genes demonstrated that this increased chitin exposure is likely due to decreased levels of glucans and mannans in the outer cell wall layers. We observed that the Mar1 protein differentially localizes to cellular membranes in a condition dependent manner, and we have further shown that the mar1Δ mutant displays defects in intracellular trafficking, resulting in a mislocalization of the β-glucan synthase catalytic subunit, Fks1. These cell surface changes influence the host-pathogen interaction, resulting in increased macrophage activation to microbial challenge in vitro. We established that several host innate immune signaling proteins are required for the observed macrophage activation, including the Card9 and MyD88 adaptor proteins, as well as the Dectin-1 and TLR2 pattern recognition receptors. These studies explore novel mechanisms by which a microbial pathogen regulates its cell surface in response to the host, as well as how dysregulation of this adaptive response leads to defective immune avoidance.
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Affiliation(s)
- Shannon K. Esher
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Kyla S. Ost
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Maria A. Kohlbrenner
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Kaila M. Pianalto
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Calla L. Telzrow
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Althea Campuzano
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - Connie B. Nichols
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
| | - Carol Munro
- MRC Centre for Medical Mycology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
| | - Floyd L. Wormley
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - J. Andrew Alspaugh
- Departments of Molecular Genetics and Microbiology/Medicine, Duke University School of Medicine, Durham, NC, United States of America
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9
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Araújo DS, de Sousa Lima P, Baeza LC, Parente AFA, Melo Bailão A, Borges CL, de Almeida Soares CM. Employing proteomic analysis to compare Paracoccidioides lutzii yeast and mycelium cell wall proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1304-1314. [PMID: 28844734 DOI: 10.1016/j.bbapap.2017.08.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 08/17/2017] [Accepted: 08/21/2017] [Indexed: 12/21/2022]
Abstract
Paracoccidioidomycosis is an important systemic mycosis caused by thermodimorphic fungi of the Paracoccidioides genus. During the infective process, the cell wall acts at the interface between the fungus and the host. In this way, the cell wall has a key role in growth, environment sensing and interaction, as well as morphogenesis of the fungus. Since the cell wall is absent in mammals, it may present molecules that are described as target sites for new antifungal drugs. Despite its importance, up to now few studies have been conducted employing proteomics in for the identification of cell wall proteins in Paracoccidioides spp. Here, a detailed proteomic approach, including cell wall-fractionation coupled to NanoUPLC-MSE, was used to study and compare the cell wall fractions from Paracoccidioides lutzii mycelia and yeast cells. The analyzed samples consisted of cell wall proteins extracted by hot SDS followed by extraction by mild alkali. In summary, 512 proteins constituting different cell wall fractions were identified, including 7 predicted GPI-dependent cell wall proteins that are potentially involved in cell wall metabolism. Adhesins previously described in Paracoccidioides spp. such as enolase, glyceraldehyde-3-phosphate dehydrogenase were identified. Comparing the proteins in mycelium and yeast cells, we detected some that are common to both fungal phases, such as Ecm33, and some specific proteins, as glucanase Crf1. All of those proteins were described in the metabolism of cell wall. Our study provides an important elucidation of cell wall composition of fractions in Paracoccidioides, opening a way to understand the fungus cell wall architecture.
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Affiliation(s)
- Danielle Silva Araújo
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil
| | - Patrícia de Sousa Lima
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil; Laboratório Interdisciplinar de Biologia, Universidade Estadual de Goiás, Itapuranga, Goiás, Brazil
| | - Lilian Cristiane Baeza
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil
| | - Ana Flávia Alves Parente
- Laboratório de Bioquímica e Química de Proteínas, Instituto de Biologia, Campus Universitário Darci Ribeiro, Brasília, DF, Brazil
| | - Alexandre Melo Bailão
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil
| | - Clayton Luiz Borges
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil
| | - Célia Maria de Almeida Soares
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, ICB II, Campus II, Universidade Federal de Goiás, 74001-970 Goiânia, Goiás, Brazil.
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10
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Traffic Through the Trans-Golgi Network and the Endosomal System Requires Collaboration Between Exomer and Clathrin Adaptors in Fission Yeast. Genetics 2016; 205:673-690. [PMID: 27974503 DOI: 10.1534/genetics.116.193458] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 12/09/2016] [Indexed: 11/18/2022] Open
Abstract
Despite its biological and medical relevance, traffic from the Golgi to the plasma membrane (PM) is one of the least understood steps of secretion. Exomer is a protein complex that mediates the trafficking of certain cargoes from the trans-Golgi network/early endosomes to the PM in budding yeast. Here, we show that in Schizosaccharomyces pombe the Cfr1 and Bch1 proteins constitute the simplest form of an exomer. Cfr1 co-immunoprecipitates with Assembly Polypeptide adaptor 1 (AP-1), AP-2, and Golgi-localized, gamma-adaptin ear domain homology, ARF-binding (GGA) subunits, and cfr1+ interacts genetically with AP-1 and GGA genes. Exomer-defective cells exhibit multiple mild defects, including alterations in the morphology of Golgi stacks and the distribution of the synaptobrevin-like Syb1 protein, carboxypeptidase missorting, and stress sensitivity. S. pombe apm1Δ cells exhibit a defect in trafficking through the early endosomes that is severely aggravated in the absence of exomer. apm1Δ cfr1Δ cells exhibit a dramatic disorganization of intracellular compartments, including massive accumulation of electron-dense tubulovesicular structures. While the trans-Golgi network/early endosomes are severely disorganized in the apm1Δ cfr1Δ strain, gga21Δ gga22Δ cfr1Δ cells exhibit a significant disturbance of the prevacuolar/vacuolar compartments. Our findings show that exomer collaborates with clathrin adaptors in trafficking through diverse cellular compartments, and that this collaboration is important to maintain their integrity. These results indicate that the effect of eliminating exomer is more pervasive than that described to date, and suggest that exomer complexes might participate in diverse steps of vesicle transport in other organisms.
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11
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Davidson R, Pontasch JA, Wu JQ. Sbg1 Is a Novel Regulator for the Localization of the β-Glucan Synthase Bgs1 in Fission Yeast. PLoS One 2016; 11:e0167043. [PMID: 27898700 PMCID: PMC5127554 DOI: 10.1371/journal.pone.0167043] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 11/08/2016] [Indexed: 02/03/2023] Open
Abstract
Glucan synthases synthesize glucans, complex polysaccharides that are the major components in fungal cell walls and division septa. Studying regulation of glucan synthases is important as they are essential for fungal cell survival and thus popular targets for anti-fungal drugs. Linear 1,3-β-glucan is the main component of primary septum and is synthesized by the conserved β-glucan synthase Bgs1 in fission yeast cytokinesis. It is known that Rho1 GTPase regulates Bgs1 catalytic activity and the F-BAR protein Cdc15 plays a role in Bgs1 delivery to the plasma membrane. Here we characterize a novel protein Sbg1 that is present in a complex with Bgs1 and regulates its protein levels and localization. Sbg1 is essential for contractile-ring constriction and septum formation during cytokinesis. Sbg1 and Bgs1 physically interact and are interdependent for localization to the plasma membrane. Bgs1 is less stable and/or mis-targeted to vacuoles in sbg1 mutants. Moreover, Sbg1 plays an earlier and more important role in Bgs1 trafficking and localization than Cdc15. Together, our data reveal a new mode of regulation for the essential β-glucan synthase Bgs1 by the novel protein Sbg1.
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Affiliation(s)
- Reshma Davidson
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Josef A. Pontasch
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Jian-Qiu Wu
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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12
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Role and organization of the actin cytoskeleton during cell-cell fusion. Semin Cell Dev Biol 2016; 60:121-126. [PMID: 27476112 DOI: 10.1016/j.semcdb.2016.07.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 07/25/2016] [Accepted: 07/26/2016] [Indexed: 11/23/2022]
Abstract
Cell-cell fusion is a ubiquitous process that underlies fertilization and development of eukaryotes. This process requires fusogenic machineries to promote plasma membrane merging, and also relies on the organization of dedicated sub-cortical cytoskeletal assemblies. This review describes the role of actin structures, so called actin fusion foci, essential for the fusion of two distinct cell types: Drosophila myoblast cells, which fuse to form myotubes, and sexually differentiated cells of the fission yeast Schizosaccharomyces pombe, which fuse to form a zygote. I describe the respective composition and organization of the two structures, discuss their proposed role in promoting plasma membrane apposition, and consider the universality of similar structures for cell-cell fusion.
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de León N, Valdivieso MH. The long life of an endocytic patch that misses AP-2. Curr Genet 2016; 62:765-770. [PMID: 27126383 DOI: 10.1007/s00294-016-0605-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 04/15/2016] [Indexed: 10/21/2022]
Abstract
Endocytosis is the process by which cells regulate extracellular fluid uptake and internalize molecules bound to their plasma membrane. This process requires the generation of protein-coated vesicles. In clathrin-mediated endocytosis (CME) the assembly polypeptide 2 (AP-2) adaptor facilitates rapid endocytosis of some plasma membrane receptors by mediating clathrin recruitment to the endocytic site and by connecting cargoes to the clathrin coat. While this adaptor is essential for early embryonic development in mammals, initial results suggested that it is dispensable for endocytosis in unicellular eukaryotes. The drastic effect of depleting AP-2 in metazoa and the mild effect of deleting AP-2 subunits in Saccharomyces cerevisiae have prevented a detailed analysis of the dynamics of endocytic patches in the absence of this adaptor. Using live-cell imaging of Schizosaccharomyces pombe endocytic sites we have shown that eliminating AP-2 perturbs the dynamics of endocytic patches beyond the moment of coat assembly. These perturbations affect the cell growth pattern and cell wall synthesis. Our results highlight the importance of using different model organisms to address the study of conserved aspects of CME.
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Affiliation(s)
- Nagore de León
- Departamento de Microbiología y Genética/Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain.,Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
| | - M-Henar Valdivieso
- Departamento de Microbiología y Genética/Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain.
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de León N, Hoya M, Curto MA, Moro S, Yanguas F, Doncel C, Valdivieso MH. The AP-2 complex is required for proper temporal and spatial dynamics of endocytic patches in fission yeast. Mol Microbiol 2016; 100:409-24. [PMID: 26749213 DOI: 10.1111/mmi.13327] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/06/2016] [Indexed: 12/27/2022]
Abstract
In metazoans the AP-2 complex has a well-defined role in clathrin-mediated endocytosis. By contrast, its direct role in endocytosis in unicellular eukaryotes has been questioned. Here, we report co- immunoprecipitation between the fission yeast AP-2 component Apl3p and clathrin, as well as the genetic interactions between apl3Δ and clc1 and sla2Δ/end4Δ mutants. Furthermore, a double clc1 apl3Δ mutant was found to be defective in FM4-64 uptake. In an otherwise wild-type strain, apl3Δ cells exhibit altered dynamics of the endocytic sites, with a heterogeneous and extended lifetime of early and late markers at the patches. Additionally, around 50% of the endocytic patches exhibit abnormal spatial dynamics, with immobile patches and patches that bounce backwards to the cell surface, showing a pervasive effect of the absence of AP-2. These alterations in the endocytic machinery result in abnormal cell wall synthesis and morphogenesis. Our results complement those found in budding yeast and confirm that a direct role of AP-2 in endocytosis has been conserved throughout evolution.
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Affiliation(s)
- Nagore de León
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - Marta Hoya
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - M-Angeles Curto
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - Sandra Moro
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - Francisco Yanguas
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - Cristina Doncel
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
| | - M-Henar Valdivieso
- Departamento de Microbiología y Genética, Instituto de Biología Funcional y Genómica (IBFG), University of Salamanca/CSIC, Calle Zacarías González 2, 37007, Salamanca, Spain
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Arasada R, Pollard TD. A role for F-BAR protein Rga7p during cytokinesis in S. pombe. J Cell Sci 2015; 128:2259-68. [PMID: 25977474 DOI: 10.1242/jcs.162974] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Accepted: 05/07/2015] [Indexed: 12/22/2022] Open
Abstract
F-BAR proteins are known to participate in cytokinesis, but their mechanisms are not well understood. Here we investigated Rga7p, an Schizosaccharomyces pombe F-BAR protein with a RhoGAP domain. Localization of Rga7p to the cytokinetic cleavage furrow depends on its F-BAR domain, actin filaments, the formins Cdc12p and For3p, and the presence of a contractile ring. Rga7p is not required for the constriction of the contractile ring but does participate in the transport of a β-glucan synthetase (Bgs4p) from the late Golgi compartments to plasma membrane that is adjacent to the contractile ring. Cells without Rga7p moved Bgs4p normally from the poles to the Golgi complex near to the cell center, but Bgs4p then moved slowly from the late Golgi compartments to the cleavage site. The late arrival and lower than normal numbers of Bgs4p result in septal defects late in cytokinesis, and in the lysis of separating cells, similar to that in cells with mutations in the cwg1(+) gene (which encodes Bgs4p).
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Affiliation(s)
- Rajesh Arasada
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
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Núñez A, Dulude D, Jbel M, Rokeach LA. Calnexin is essential for survival under nitrogen starvation and stationary phase in Schizosaccharomyces pombe. PLoS One 2015; 10:e0121059. [PMID: 25803873 PMCID: PMC4372366 DOI: 10.1371/journal.pone.0121059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 02/06/2015] [Indexed: 12/04/2022] Open
Abstract
Cell fate is determined by the balance of conserved molecular mechanisms regulating death (apoptosis) and survival (autophagy). Autophagy is a process by which cells recycle their organelles and macromolecules through degradation within the vacuole in yeast and plants, and lysosome in metazoa. In the yeast Schizosaccharomyces pombe, autophagy is strongly induced under nitrogen starvation and in aging cells. Previously, we demonstrated that calnexin (Cnx1p), a highly conserved transmembrane chaperone of the endoplasmic reticulum (ER), regulates apoptosis under ER stress or inositol starvation. Moreover, we showed that in stationary phase, Cnx1p is cleaved into two moieties, L_Cnx1p and S_Cnx1p. Here, we show that the processing of Cnx1p is regulated by autophagy, induced by nitrogen starvation or cell aging. The cleavage of Cnx1p involves two vacuolar proteases: Isp6, which is essential for autophagy, and its paralogue Psp3. Blocking autophagy through the knockout of autophagy-related genes (atg) results in inhibition of both, the cleavage and the trafficking of Cnx1p from the ER to the vacuole. We demonstrate that Cnx1p is required for cell survival under nitrogen-starvation and in chronological aging cultures. The death of the mini_cnx1 mutant (overlapping S_cnx1p) cells is accompanied by accumulation of high levels of reactive-oxygen species (ROS), a slowdown in endocytosis and severe cell-wall defects. Moreover, mutant cells expressing only S_Cnx1p showed cell wall defects. Co-expressing mutant overlapping the L_Cnx1p and S_Cnx1p cleavage products reverses the death, ROS phenotype and cell wall defect to wild-type levels. As it is involved in both apoptosis and autophagy, Cnx1p could be a nexus for the crosstalk between these pro-death and pro-survival mechanisms. Ours, and observations in mammalian systems, suggest that the multiple roles of calnexin depend on its sub-cellular localization and on its cleavage. The use of S. pombe should assist in further shedding light on the multiple roles of calnexin.
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Affiliation(s)
- Andrés Núñez
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Dominic Dulude
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Mehdi Jbel
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Luis A. Rokeach
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
- * E-mail:
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