1
|
Perrine-Walker F. Caspofungin resistance in Candida albicans: genetic factors and synergistic compounds for combination therapies. Braz J Microbiol 2022; 53:1101-1113. [PMID: 35352319 PMCID: PMC9433586 DOI: 10.1007/s42770-022-00739-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 03/25/2022] [Indexed: 11/25/2022] Open
Abstract
Caspofungin and other echinocandins have been used for the treatment of human infections by the opportunistic yeast pathogen, Candida albicans. There has been an increase in infections by non-albicans Candida species such as Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei, and Candida auris in clinical or hospital settings. This is problematic to public health due to the increasing prevalence of echinocandin resistant species/strains. This review will present a summary on various studies that investigated the inhibitory action of caspofungin on 1,3-β-D-glucan synthesis, on cell wall structure, and biofilm formation of C. albicans. It will highlight some of the issues linked to caspofungin resistance or reduced caspofungin sensitivity in various Candida species and the potential benefits of antimicrobial peptides and other compounds in synergy with caspofungin.
Collapse
Affiliation(s)
- Francine Perrine-Walker
- Department of Biochemistry and Genetics, La Trobe Institute For Molecular Science, La Trobe University, Bundoora, VIC, 3086, Australia.
| |
Collapse
|
2
|
Chun J, Bai J, Ryu S. Yeast Surface Display System for Facilitated Production and Application of Phage Endolysin. ACS Synth Biol 2020; 9:508-516. [PMID: 32119773 DOI: 10.1021/acssynbio.9b00360] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Bacteriophage endolysin is one of the potential alternatives of conventional antibiotics, but the intrinsic limitations of the bacterial expression system may undermine the comprehensive application of this therapeutic protein. To circumvent such limitations, we adopted a yeast surface display system as a novel expression platform for endolysin. Endolysin LysSA11 from staphylococcal phage SA11 was expressed and surface-displayed in Saccharomyces cerevisiae to exhibit sufficient antimicrobial activity against Staphylococcus aureus. Without any protein isolation or purification procedures, we showed that direct treatment of LysSA11-displaying yeast cells could accomplish a 5-log reduction of viable Staphylococcus aureus within 3 h. Furthermore, the surface-displayed LysSA11 exhibited superior stability over the soluble form of purified LysSA11 during 14 days of storage in a refrigerated environment. We suggest that the yeast surface display system is an efficient, stable, and straightforward platform for the production and antibacterial applications of endolysin.
Collapse
Affiliation(s)
- Jihwan Chun
- Department of Food and Animal Biotechnology, Seoul National University, Seoul 08826, Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Korea
| | - Jaewoo Bai
- Department of Food and Animal Biotechnology, Seoul National University, Seoul 08826, Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Korea
| | - Sangryeol Ryu
- Department of Food and Animal Biotechnology, Seoul National University, Seoul 08826, Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea
- Center for Food and Bioconvergence, Seoul National University, Seoul 08826, Korea
| |
Collapse
|
3
|
Muszewska A, Piłsyk S, Perlińska-Lenart U, Kruszewska JS. Diversity of Cell Wall Related Proteins in Human Pathogenic Fungi. J Fungi (Basel) 2017; 4:E6. [PMID: 29371499 PMCID: PMC5872309 DOI: 10.3390/jof4010006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 12/13/2017] [Accepted: 12/25/2017] [Indexed: 02/06/2023] Open
Abstract
The cell wall is one of the major keys to fungal identity. Fungi use their cell wall to sense the environment, and localize nutrients and competing microorganism. Pathogenic species additionally modify their cell walls to hide from a host's immune system. With the growing number of fungal infections and alarming shortage of available drugs, we are in need of new approaches to fight pathogens. The cell wall seems to be a natural target, since animal host cells are devoid of it. The current knowledge about fungal cell wall components is often limited, and there is huge diversity both in structure and composition between species. In order to compare the distribution of diverse proteins involved in cell wall biosynthesis and maintenance, we performed sequence homology searches against 24 fungal proteomes from distinct taxonomic groups, all reported as human pathogens. This approach led to identification of 4014 cell wall proteins (CWPs), and enabled us to speculate about cell wall composition in recently sequenced pathogenic fungi with limited experimental information. We found large expansions of several CWP families, in particular taxa, and a number of new CWPs possibly involved in evading host immune recognition. Here, we present a comprehensive evolutionary history of fungal CWP families in the context of the fungal tree of life.
Collapse
Affiliation(s)
- Anna Muszewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-792 Warsaw, Poland.
| | - Sebastian Piłsyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-792 Warsaw, Poland.
| | | | - Joanna S Kruszewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-792 Warsaw, Poland.
| |
Collapse
|
4
|
Tanaka Y, Sasaki M, Ito F, Aoyama T, Sato-Okamoto M, Takahashi-Nakaguchi A, Chibana H, Shibata N. Cooperation between ER stress and calcineurin signaling contributes to the maintenance of cell wall integrity in Candida glabrata. Fungal Biol 2017; 122:19-33. [PMID: 29248112 DOI: 10.1016/j.funbio.2017.09.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 09/04/2017] [Accepted: 09/30/2017] [Indexed: 10/18/2022]
Abstract
Candida glabrata is the second most common source of Candida infections in humans. In this pathogen, the maintenance of cell wall integrity (CWI) frequently precludes effective pharmacological treatment by antifungal agents. In numerous fungi, cell wall modulation is reported to be controlled by endoplasmic reticulum (ER) stress, but how the latter affects CWI maintenance in C. glabrata is not clearly understood. Here, we characterized a C. glabrata strain harboring a mutation in the CNE1 gene, which encodes a molecular chaperone associated with nascent glycoprotein maturation in the ER. Disruption of cne1 induced ER stress and caused changes in the normal cell wall structure, specifically a reduction in the β-1,6-glucan content and accumulation of chitin. Conversely, a treatment with the typical ER stress inducer tunicamycin up-regulated the production of cell wall chitin but did not affect β-1,6-glucan content. Our results also indicated that C. glabrata features a uniquely evolved ER stress-mediated CWI pathway, which differs from that in the closely related species Saccharomyces cerevisiae. Furthermore, we demonstrated that ER stress-mediated CWI pathway in C. glabrata is also induced by the disruption of other genes encoding proteins that function in a correlated manner in the quality control of N-linked glycoproteins in the ER. These results suggest that calcineurin and ER quality control system act as a platform for maintaining CWI in C. glabrata.
Collapse
Affiliation(s)
- Yutaka Tanaka
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
| | - Masato Sasaki
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
| | - Fumie Ito
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
| | - Toshio Aoyama
- Department of Electronic and Information Engineering, Suzuka National College of Technology, Shirako-tyo, Suzuka, Mie 510-0294, Japan
| | - Michiyo Sato-Okamoto
- Medical Mycology Research Center, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8673, Japan
| | | | - Hiroji Chibana
- Medical Mycology Research Center, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8673, Japan
| | - Nobuyuki Shibata
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan.
| |
Collapse
|
5
|
Abstract
β-(1,3)-Glucan, the major fungal cell wall component, ramifies through β-(1,6)-glycosidic linkages, which facilitates its binding with other cell wall components contributing to proper cell wall assembly. Using Saccharomyces cerevisiae as a model, we developed a protocol to quantify β-(1,6)-branching on β-(1,3)-glucan. Permeabilized S. cerevisiae and radiolabeled substrate UDP-(14C)glucose allowed us to determine branching kinetics. A screening aimed at identifying deletion mutants with reduced branching among them revealed only two, the bgl2Δ and gas1Δ mutants, showing 15% and 70% reductions in the branching, respectively, compared to the wild-type strain. Interestingly, a recombinant Gas1p introduced β-(1,6)-branching on the β-(1,3)-oligomers following its β-(1,3)-elongase activity. Sequential elongation and branching activity of Gas1p occurred on linear β-(1,3)-oligomers as well as Bgl2p-catalyzed products [short β-(1,3)-oligomers linked by a linear β-(1,6)-linkage]. The double S. cerevisiae gas1Δ bgl2Δ mutant showed a drastically sick phenotype. An ScGas1p ortholog, Gel4p from Aspergillus fumigatus, also showed dual β-(1,3)-glucan elongating and branching activity. Both ScGas1p and A. fumigatus Gel4p sequences are endowed with a carbohydrate binding module (CBM), CBM43, which was required for the dual β-(1,3)-glucan elongating and branching activity. Our report unravels the β-(1,3)-glucan branching mechanism, a phenomenon occurring during construction of the cell wall which is essential for fungal life. The fungal cell wall is essential for growth, morphogenesis, protection, and survival. In spite of being essential, cell wall biogenesis, especially the core β-(1,3)-glucan ramification, is poorly understood; the ramified β-(1,3)-glucan interconnects other cell wall components. Once linear β-(1,3)-glucan is synthesized by plasma membrane-bound glucan synthase, the subsequent event is its branching event in the cell wall space. Using Saccharomyces cerevisiae as a model, we identified GH72 and GH17 family glycosyltransferases, Gas1p and Bgl2p, respectively, involved in the β-(1,3)-glucan branching. The sick phenotype of the double Scgas1Δ bgl2Δ mutant suggested that β-(1,3)-glucan branching is essential. In addition to ScGas1p, GH72 family ScGas2p and Aspergillus fumigatus Gel4p, having CBM43 in their sequences, showed dual β-(1,3)-glucan elongating and branching activity. Our report identifies the fungal cell wall β-(1,3)-glucan branching mechanism. The essentiality of β-(1,3)-glucan branching suggests that enzymes involved in the glucan branching could be exploited as antifungal targets.
Collapse
|
6
|
Tanaka Y, Sasaki M, Ito F, Aoyama T, Sato-Okamoto M, Takahashi-Nakaguchi A, Chibana H, Shibata N. KRE5 Suppression Induces Cell Wall Stress and Alternative ER Stress Response Required for Maintaining Cell Wall Integrity in Candida glabrata. PLoS One 2016; 11:e0161371. [PMID: 27548283 PMCID: PMC4993462 DOI: 10.1371/journal.pone.0161371] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 08/04/2016] [Indexed: 01/10/2023] Open
Abstract
The maintenance of cell wall integrity in fungi is required for normal cell growth, division, hyphae formation, and antifungal tolerance. We observed that endoplasmic reticulum stress regulated cell wall integrity in Candida glabrata, which possesses uniquely evolved mechanisms for unfolded protein response mechanisms. Tetracycline-mediated suppression of KRE5, which encodes a predicted UDP-glucose:glycoprotein glucosyltransferase localized in the endoplasmic reticulum, significantly increased cell wall chitin content and decreased cell wall β-1,6-glucan content. KRE5 repression induced endoplasmic reticulum stress-related gene expression and MAP kinase pathway activation, including Slt2p and Hog1p phosphorylation, through the cell wall integrity signaling pathway. Moreover, the calcineurin pathway negatively regulated cell wall integrity, but not the reduction of β-1,6-glucan content. These results indicate that KRE5 is required for maintaining both endoplasmic reticulum homeostasis and cell wall integrity, and that the calcineurin pathway acts as a regulator of chitin-glucan balance in the cell wall and as an alternative mediator of endoplasmic reticulum stress in C. glabrata.
Collapse
Affiliation(s)
- Yutaka Tanaka
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Sendai, Japan
| | - Masato Sasaki
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Sendai, Japan
| | - Fumie Ito
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Sendai, Japan
| | - Toshio Aoyama
- Department of Electronic and Information Engineering, Suzuka National College of Technology, Suzuka, Japan
| | | | | | - Hiroji Chibana
- Medical Mycology Research Center, Chiba University, Chiba, Japan
| | - Nobuyuki Shibata
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Sendai, Japan
- * E-mail:
| |
Collapse
|
7
|
Pillet F, Lemonier S, Schiavone M, Formosa C, Martin-Yken H, Francois JM, Dague E. Uncovering by atomic force microscopy of an original circular structure at the yeast cell surface in response to heat shock. BMC Biol 2014; 12:6. [PMID: 24468076 PMCID: PMC3925996 DOI: 10.1186/1741-7007-12-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/10/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Atomic Force Microscopy (AFM) is a polyvalent tool that allows biological and mechanical studies of full living microorganisms, and therefore the comprehension of molecular mechanisms at the nanoscale level. By combining AFM with genetical and biochemical methods, we explored the biophysical response of the yeast Saccharomyces cerevisiae to a temperature stress from 30°C to 42°C during 1 h. RESULTS We report for the first time the formation of an unprecedented circular structure at the cell surface that takes its origin at a single punctuate source and propagates in a concentric manner to reach a diameter of 2-3 μm at least, thus significantly greater than a bud scar. Concomitantly, the cell wall stiffness determined by the Young's Modulus of heat stressed cells increased two fold with a concurrent increase of chitin. This heat-induced circular structure was not found either in wsc1Δ or bck1Δ mutants that are defective in the CWI signaling pathway, nor in chs1Δ, chs3Δ and bni1Δ mutant cells, reported to be deficient in the proper budding process. It was also abolished in the presence of latrunculin A, a toxin known to destabilize actin cytoskeleton. CONCLUSIONS Our results suggest that this singular morphological event occurring at the cell surface is due to a dysfunction in the budding machinery caused by the heat shock and that this phenomenon is under the control of the CWI pathway.
Collapse
Affiliation(s)
- Flavien Pillet
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
| | - Stéphane Lemonier
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, ITAV-USR 3505, F31106 Toulouse, France
| | - Marion Schiavone
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Cécile Formosa
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, UMR 7565, SRSMC, Vandoeuvre-lès-Nancy, France
- Université de Lorraine, UMR 7565, Faculté de Pharmacie, Nancy, France
| | - Hélène Martin-Yken
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Jean Marie Francois
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Etienne Dague
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, ITAV-USR 3505, F31106 Toulouse, France
| |
Collapse
|
8
|
Muccilli S, Wemhoff S, Restuccia C, Meinhardt F. Exoglucanase-encoding genes from three Wickerhamomyces anomalus killer strains isolated from olive brine. Yeast 2012; 30:33-43. [PMID: 23148020 DOI: 10.1002/yea.2935] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 10/08/2012] [Indexed: 11/08/2022] Open
Abstract
Wickerhamomyces anomalus killer strains are important for fighting pathogenic yeasts and for controlling harmful yeasts and bacteria in the food industry. Targeted disruption of key genes in β-glucan synthesis of a sensitive Saccharomyces cerevisiae strain conferred resistance to the toxins of W. anomalus strains BS91, BCA15 and BCU24 isolated from olive brine. Competitive inhibition of the killing activities by laminarin and pustulan refer to β-1,3- and β-1,6-glucans as the main primary toxin targets. The extracellular exoglucanase-encoding genes WaEXG1 and WaEXG2 from the three strains were sequenced and were found to display noticeable similarities to those from known potent W. anomalus killer strains.
Collapse
Affiliation(s)
- Serena Muccilli
- DISPA, Sezione di Tecnologia e Microbiologia degli Alimenti, University of Catania, Italy
| | | | | | | |
Collapse
|
9
|
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: 303] [Impact Index Per Article: 25.3] [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.
Collapse
Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
| |
Collapse
|
10
|
Robledo-Ortiz CI, Flores-Carreón A, Hernández-Cervantes A, Álvarez-Vargas A, Lee KK, Díaz-Jiménez DF, Munro CA, Cano-Canchola C, Mora-Montes HM. Isolation and functional characterization of Sporothrix schenckii ROT2, the encoding gene for the endoplasmic reticulum glucosidase II. Fungal Biol 2012; 116:910-8. [DOI: 10.1016/j.funbio.2012.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 06/06/2012] [Accepted: 06/15/2012] [Indexed: 12/20/2022]
|
11
|
Kurita T, Noda Y, Yoda K. Action of multiple endoplasmic reticulum chaperon-like proteins is required for proper folding and polarized localization of Kre6 protein essential in yeast cell wall β-1,6-glucan synthesis. J Biol Chem 2012; 287:17415-17424. [PMID: 22447934 DOI: 10.1074/jbc.m111.321018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Saccharomyces cerevisiae Kre6 is a type II membrane protein essential for cell wall β-1,6-glucan synthesis. Recently we reported that the majority of Kre6 is in the endoplasmic reticulum (ER), but a significant portion of Kre6 is found in the plasma membrane of buds, and this polarized appearance of Kre6 is required for β-1,6-glucan synthesis. An essential membrane protein, Keg1, and ER chaperon Rot1 bind to Kre6. In this study we found that in mutant keg1-1 cells, accumulation of Kre6 at the buds is diminished, binding of Kre6 to Keg1 is decreased, and Kre6 becomes susceptible to ER-associated degradation (ERAD), which suggests Keg1 participates in folding and transport of Kre6. All mutants of the calnexin cycle member homologues (cwh41, rot2, kre5, and cne1) showed defects in β-1,6-glucan synthesis, although the calnexin chaperon system is considered not functional in yeast. We found synthetic defects between them and keg1-1, and Cne1 co-immunoprecipitated with Keg1 and Kre6. A stronger binding of Cne1 to Kre6 was detected when two glucosidases (Cwh41 and Rot2) that remove glucose on N-glycan were functional. Skn1, a Kre6 homologue, was not detected by immunofluorescence in the wild type yeast, but in kre6Δ cells it became detectable and behaved like Kre6. In conclusion, the action of multiple ER chaperon-like proteins is required for proper folding and localization of Kre6 and probably Skn1 to function in β-1,6-glucan synthesis.
Collapse
Affiliation(s)
- Tomokazu Kurita
- Department of Biotechnology, University of Tokyo, Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Yoichi Noda
- Department of Biotechnology, University of Tokyo, Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Koji Yoda
- Department of Biotechnology, University of Tokyo, Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan.
| |
Collapse
|
12
|
Powers-Fletcher MV, Jambunathan K, Brewer JL, Krishnan K, Feng X, Galande AK, Askew DS. Impact of the lectin chaperone calnexin on the stress response, virulence and proteolytic secretome of the fungal pathogen Aspergillus fumigatus. PLoS One 2011; 6:e28865. [PMID: 22163332 PMCID: PMC3233604 DOI: 10.1371/journal.pone.0028865] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 11/16/2011] [Indexed: 11/18/2022] Open
Abstract
Calnexin is a membrane-bound lectin chaperone in the endoplasmic reticulum (ER) that is part of a quality control system that promotes the accurate folding of glycoproteins entering the secretory pathway. We have previously shown that ER homeostasis is important for virulence of the human fungal pathogen Aspergillus fumigatus, but the contribution of calnexin has not been explored. Here, we determined the extent to which A. fumigatus relies on calnexin for growth under conditions of environmental stress and for virulence. The calnexin gene, clxA, was deleted from A. fumigatus and complemented by reconstitution with the wild type gene. Loss of clxA altered the proteolytic secretome of the fungus, but had no impact on growth rates in either minimal or complex media at 37°C. However, the ΔclxA mutant was growth impaired at temperatures above 42°C and was hypersensitive to acute ER stress caused by the reducing agent dithiothreitol. In contrast to wild type A. fumigatus, ΔclxA hyphae were unable to grow when transferred to starvation medium. In addition, depleting the medium of cations by chelation prevented ΔclxA from sustaining polarized hyphal growth, resulting in blunted hyphae with irregular morphology. Despite these abnormal stress responses, the ΔclxA mutant remained virulent in two immunologically distinct models of invasive aspergillosis. These findings demonstrate that calnexin functions are needed for growth under conditions of thermal, ER and nutrient stress, but are dispensable for surviving the stresses encountered in the host environment.
Collapse
Affiliation(s)
- Margaret V. Powers-Fletcher
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | | | - Jordan L. Brewer
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Xizhi Feng
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Amit K. Galande
- SRI International, Harrisonburg, Virginia, United States of America
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- * E-mail:
| |
Collapse
|
13
|
Määttänen P, Gehring K, Bergeron JJM, Thomas DY. Protein quality control in the ER: the recognition of misfolded proteins. Semin Cell Dev Biol 2010; 21:500-11. [PMID: 20347046 DOI: 10.1016/j.semcdb.2010.03.006] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 03/16/2010] [Accepted: 03/18/2010] [Indexed: 02/08/2023]
Abstract
The mechanism, in molecular terms of protein quality control, specifically of how the cell recognizes and discriminates misfolded proteins, remains a challenge. In the secretory pathway the folding status of glycoproteins passing through the endoplasmic reticulum is marked by the composition of the N-glycan. The different glycoforms are recognized by specialized lectins. The folding sensor UGGT acts as an unusual molecular chaperone and covalently modifies the Man9 N-glycan of a misfolded protein by adding a glucose moiety and converts it to Glc1Man9 that rebinds the lectin calnexin. However, further links between the folding status of a glycoprotein and the composition of the N-glycan are unclear. There is little unequivocal evidence for other proteins in the ER recognizing the N-glycan and also acting as molecular chaperones. Nevertheless, based upon a few examples, we suggest that this function is carried out by individual proteins in several different complexes. Thus, calnexin binds the protein disulfide isomerase ERp57, that acts upon Glc1Man9 glycoproteins. In another example the protein disulfide isomerase ERdj5 binds specifically to EDEM (which is probably a mannosidase) and a lectin OS9, and reduces the disulfide bonds of bound glycoproteins destined for ERAD. Thus the glycan recognition is performed by a lectin and the chaperone function performed by a specific partner protein that can recognize misfolded proteins. We predict that this will be a common arrangement of proteins in the ER and that members of protein foldase families such as PDI and PPI will bind specifically to lectins in the ER. Molecular chaperones BiP and GRp94 will assist in the folding of proteins bound in these complexes as well as in the folding of non-glycoproteins.
Collapse
Affiliation(s)
- Pekka Määttänen
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | | | | | | |
Collapse
|
14
|
Guérin R, Beauregard PB, Leroux A, Rokeach LA. Calnexin regulates apoptosis induced by inositol starvation in fission yeast. PLoS One 2009; 4:e6244. [PMID: 19606215 PMCID: PMC2705804 DOI: 10.1371/journal.pone.0006244] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 06/08/2009] [Indexed: 12/21/2022] Open
Abstract
Inositol is a precursor of numerous phospholipids and signalling molecules essential for the cell. Schizosaccharomyces pombe is naturally auxotroph for inositol as its genome does not have a homologue of the INO1 gene encoding inositol-1-phosphate synthase, the enzyme responsible for inositol biosynthesis. In this work, we demonstrate that inositol starvation in S. pombe causes cell death with apoptotic features. This apoptotic death is dependent on the metacaspase Pca1p and is affected by the UPR transducer Ire1p. Previously, we demonstrated that calnexin is involved in apoptosis induced by ER stress. Here, we show that cells expressing a lumenal version of calnexin exhibit a 2-fold increase in the levels of apoptosis provoked by inositol starvation. This increase is reversed by co-expression of a calnexin mutant spanning the transmembrane domain and C-terminal cytosolic tail. Coherently, calnexin is physiologically cleaved at the end of its lumenal domain, under normal growth conditions when cells approach stationary phase. This cleavage suggests that the two naturally produced calnexin fragments are needed to continue growth into stationary phase and to prevent cell death. Collectively, our observations indicate that calnexin takes part in at least two apoptotic pathways in S. pombe, and suggest that the cleavage of calnexin has regulatory roles in apoptotic processes involving calnexin.
Collapse
Affiliation(s)
- Renée Guérin
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| | | | - Alexandre Leroux
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| | - Luis A. Rokeach
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| |
Collapse
|
15
|
The effect of calnexin deletion on the expression level of binding protein (BiP) under heat stress conditions in Saccharomyces cerevisiae. Cell Mol Biol Lett 2008; 13:621-31. [PMID: 18661113 PMCID: PMC6275899 DOI: 10.2478/s11658-008-0026-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 05/08/2008] [Accepted: 05/08/2008] [Indexed: 11/20/2022] Open
Abstract
In order to investigate the effect of calnexin deletion on the induction of the main ER molecular chaperone BiP, we cultured the wild-type and calnexin-disrupted Saccharomyces cerevisiae strains under normal and stressed conditions. The growth rate of the calnexin-disrupted yeast was almost the same as that of the wild-type yeast under those conditions. However, the induced level of BiP mRNA in the ER was evidently higher in calnexin-disrupted S. cerevisiae than in the wild-type at 37 degrees C, but was almost the same in the two strains under normal conditions. The Western blot analysis results for BiP protein expression in the ER showed a parallel in the mRNA levels in the two strains. It is suggested that under heat stress conditions, the induction of BiP in the ER might recover part of the function of calnexin in calnexin-disrupted yeast, and result in the same growth rate as in wild-type yeast.
Collapse
|
16
|
Endoplasmic reticulum alpha-glycosidases of Candida albicans are required for N glycosylation, cell wall integrity, and normal host-fungus interaction. EUKARYOTIC CELL 2007; 6:2184-93. [PMID: 17933909 PMCID: PMC2168260 DOI: 10.1128/ec.00350-07] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cell surface of Candida albicans is enriched in highly glycosylated mannoproteins that are involved in the interaction with the host tissues. N glycosylation is a posttranslational modification that is initiated in the endoplasmic reticulum (ER), where the Glc(3)Man(9)GlcNAc(2) N-glycan is processed by alpha-glucosidases I and II and alpha1,2-mannosidase to generate Man(8)GlcNAc(2). This N-oligosaccharide is then elaborated in the Golgi to form N-glycans with highly branched outer chains rich in mannose. In Saccharomyces cerevisiae, CWH41, ROT2, and MNS1 encode for alpha-glucosidase I, alpha-glucosidase II catalytic subunit, and alpha1,2-mannosidase, respectively. We disrupted the C. albicans CWH41, ROT2, and MNS1 homologs to determine the importance of N-oligosaccharide processing on the N-glycan outer-chain elongation and the host-fungus interaction. Yeast cells of Cacwh41Delta, Carot2Delta, and Camns1Delta null mutants tended to aggregate, displayed reduced growth rates, had a lower content of cell wall phosphomannan and other changes in cell wall composition, underglycosylated beta-N-acetylhexosaminidase, and had a constitutively activated PKC-Mkc1 cell wall integrity pathway. They were also attenuated in virulence in a murine model of systemic infection and stimulated an altered pro- and anti-inflammatory cytokine profile from human monocytes. Therefore, N-oligosaccharide processing by ER glycosidases is required for cell wall integrity and for host-fungus interactions.
Collapse
|
17
|
Abstract
An extracellular matrix composed of a layered meshwork of beta-glucans, chitin, and mannoproteins encapsulates cells of the yeast Saccharomyces cerevisiae. This organelle determines cellular morphology and plays a critical role in maintaining cell integrity during cell growth and division, under stress conditions, upon cell fusion in mating, and in the durable ascospore cell wall. Here we assess recent progress in understanding the molecular biology and biochemistry of cell wall synthesis and its remodeling in S. cerevisiae. We then review the regulatory dynamics of cell wall assembly, an area where functional genomics offers new insights into the integration of cell wall growth and morphogenesis with a polarized secretory system that is under cell cycle and cell type program controls.
Collapse
Affiliation(s)
- Guillaume Lesage
- Department of Biology, McGill University, Montreal, PQ H3A 1B1, Canada
| | | |
Collapse
|
18
|
Wheeler RT, Fink GR. A drug-sensitive genetic network masks fungi from the immune system. PLoS Pathog 2006; 2:e35. [PMID: 16652171 PMCID: PMC1447670 DOI: 10.1371/journal.ppat.0020035] [Citation(s) in RCA: 262] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 03/16/2006] [Indexed: 11/20/2022] Open
Abstract
Fungal pathogens can be recognized by the immune system via their β-glucan, a potent proinflammatory molecule that is present at high levels but is predominantly buried beneath a mannoprotein coat and invisible to the host. To investigate the nature and significance of “masking” this molecule, we characterized the mechanism of masking and consequences of unmasking for immune recognition. We found that the underlying β-glucan in the cell wall of Candida albicans is unmasked by subinhibitory doses of the antifungal drug caspofungin, causing the exposed fungi to elicit a stronger immune response. Using a library of bakers' yeast (Saccharomyces cerevisiae) mutants, we uncovered a conserved genetic network that is required for concealing β-glucan from the immune system and limiting the host response. Perturbation of parts of this network in the pathogen C. albicans caused unmasking of its β-glucan, leading to increased β-glucan receptor-dependent elicitation of key proinflammatory cytokines from primary mouse macrophages. By creating an anti-inflammatory barrier to mask β-glucan, opportunistic fungi may promote commensal colonization and have an increased propensity for causing disease. Targeting the widely conserved gene network required for creating and maintaining this barrier may lead to novel broad-spectrum antimycotics. Opportunistic fungal pathogens such as Candida albicans often cause fatal infections in patients with a compromised immune system. Unfortunately, current drugs often fail to halt fungal disease, are ineffective against drug-resistant strains, and have severe side effects. Despite the clear clinical significance of fungal infections, it is still not understood how fungi are recognized by the immune system. Candida has high levels of the structural molecule β-glucan in its cell wall, but the majority of its β-glucan is masked by a mannoprotein coat and is therefore invisible to the immune system. Masking of β-glucan may be a fungal virulence factor, because exposed β-glucan provokes a proinflammatory response that is important for mounting an effective immune response against the fungus and clearing the infection. By surveying the genome of the model fungus Saccharomyces cerevisiae (bakers' yeast), the authors discovered a genetic network required for masking β-glucan from the immune system. Mutation of genes in this network in C. albicans caused unmasking of β-glucan and an increased immune response to the fungus. The authors also found that sublethal doses of the antifungal drug caspofungin cause unmasking and lead to a greater immune response. Drugs targeting this fungally conserved masking network may provide new tools to fight fungal infections.
Collapse
Affiliation(s)
- Robert T Wheeler
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA.
| | | |
Collapse
|
19
|
Maneesri J, Azuma M, Sakai Y, Igarashi K, Matsumoto T, Fukuda H, Kondo A, Ooshima H. Deletion of MCD 4 involved in glycosylphosphatidylinositol (GPI) anchor synthesis leads to an increase in beta-1,6-glucan level and a decrease in GPI-anchored protein and mannan levels in the cell wall of Saccharomyces cerevisiae. J Biosci Bioeng 2005; 99:354-60. [PMID: 16233801 DOI: 10.1263/jbb.99.354] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Accepted: 12/22/2004] [Indexed: 11/17/2022]
Abstract
Most proteins involved in the synthesis of the GPI core structure of Saccharomyces cerevisiae are essential for growth. To explore the relationship between the GPI anchor structure and beta-1,6-glucan synthesis, we screened deletion mutants in genes involved in GPI synthesis for osmotic remedial growth. Heterozygous diploid strains were dissected on medium with osmotic support and slow growth of the mcd 4 deletion mutant was observed. The mcd 4 mutant showed abnormal morphology and cell aggregation, and was hypersensitive to SDS, hygromycin B and K1 killer toxin. Incorporation of GPI cell wall proteins was examined using a GPI-Flo 1 fusion protein. The result suggested that the mcd 4 deletion causes a decrease in GPI cell wall proteins levels. The mutation also caused a decrease in mannan levels and an increase in alkali-insoluble beta-1,6-glucan and chitin levels in the cell wall.
Collapse
Affiliation(s)
- Jaruwan Maneesri
- Department of Applied and Bioapplied Chemistry, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Schuldiner M, Collins SR, Thompson NJ, Denic V, Bhamidipati A, Punna T, Ihmels J, Andrews B, Boone C, Greenblatt JF, Weissman JS, Krogan NJ. Exploration of the Function and Organization of the Yeast Early Secretory Pathway through an Epistatic Miniarray Profile. Cell 2005; 123:507-19. [PMID: 16269340 DOI: 10.1016/j.cell.2005.08.031] [Citation(s) in RCA: 670] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 08/12/2005] [Accepted: 08/22/2005] [Indexed: 10/25/2022]
Abstract
We present a strategy for generating and analyzing comprehensive genetic-interaction maps, termed E-MAPs (epistatic miniarray profiles), comprising quantitative measures of aggravating or alleviating interactions between gene pairs. Crucial to the interpretation of E-MAPs is their high-density nature made possible by focusing on logically connected gene subsets and including essential genes. Described here is the analysis of an E-MAP of genes acting in the yeast early secretory pathway. Hierarchical clustering, together with novel analytical strategies and experimental verification, revealed or clarified the role of many proteins involved in extensively studied processes such as sphingolipid metabolism and retention of HDEL proteins. At a broader level, analysis of the E-MAP delineated pathway organization and components of physical complexes and illustrated the interconnection between the various secretory processes. Extension of this strategy to other logically connected gene subsets in yeast and higher eukaryotes should provide critical insights into the functional/organizational principles of biological systems.
Collapse
Affiliation(s)
- Maya Schuldiner
- Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California 94143, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
D'Alessio C, Caramelo JJ, Parodi AJ. Absence of nucleoside diphosphatase activities in the yeast secretory pathway does not abolish nucleotide sugar-dependent protein glycosylation. J Biol Chem 2005; 280:40417-27. [PMID: 16172132 DOI: 10.1074/jbc.m503149200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is accepted that glycosyltransferase-generated nucleoside diphosphates are converted to monophosphates in the secretory pathway by nucleoside diphosphatases (NDPases) to provide substrates for antiport transport systems by which entrance of nucleotide sugars from the cytosol into the lumen is coupled to exit of nucleoside monophosphates. Working with Saccharomyces cerevisiae mutants affected in anterograde and/or retrograde endoplasmic reticulum (ER)-Golgi vesicular traffic and/or defective in one or both secretory pathway (Golgi) NDPases, we show that UDP-Glc: glycoprotein glucosyltransferase-mediated glucosylation is not dependent on the presence of NDPases or on ER-Golgi vesicular traffic and that GDP-Man-dependent N- and O-mannosylations are reduced but not abolished in the absence of NDPases in the secretory pathway. Further, the absence of the main Man-1-P transferase (a Golgi GMP-generating enzyme) does not modify the limited mannosylation observed in the absence of NDPases. Based on these results and on available additional information, we suggest that in the absence of NDPases, the already characterized nucleotide sugar transporters allow entrance of nucleotide sugars into the luminal compartments and that resulting nucleoside diphosphates exit to the cytosol by a still unknown mechanism. Further, an unexpected side result suggests that formation of Ser/Thr-Man(2) may occur in the ER and not exclusively in the Golgi.
Collapse
Affiliation(s)
- Cecilia D'Alessio
- Laboratory of Glycobiology, Fundación Instituto Leloir, Avda. Patricias Argentinas 435, Buenos Aires C1405BWE, Argentina
| | | | | |
Collapse
|
22
|
Zhong Q, Gvozdenovic-Jeremic J, Webster P, Zhou J, Greenberg ML. Loss of function of KRE5 suppresses temperature sensitivity of mutants lacking mitochondrial anionic lipids. Mol Biol Cell 2004; 16:665-75. [PMID: 15563612 PMCID: PMC545902 DOI: 10.1091/mbc.e04-09-0808] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Disruption of PGS1, which encodes the enzyme that catalyzes the committed step of cardiolipin (CL) synthesis, results in loss of the mitochondrial anionic phospholipids phosphatidylglycerol (PG) and CL. The pgs1Delta mutant exhibits severe growth defects at 37 degrees C. To understand the essential functions of mitochondrial anionic lipids at elevated temperatures, we isolated suppressors of pgs1Delta that grew at 37 degrees C. One of the suppressors has a loss of function mutation in KRE5, which is involved in cell wall biogenesis. The cell wall of pgs1Delta contained markedly reduced beta-1,3-glucan, which was restored in the suppressor. Stabilization of the cell wall with osmotic support alleviated the cell wall defects of pgs1Delta and suppressed the temperature sensitivity of all CL-deficient mutants. Evidence is presented suggesting that the previously reported inability of pgs1Delta to grow in the presence of ethidium bromide was due to defective cell wall integrity, not from "petite lethality." These findings demonstrated that mitochondrial anionic lipids are required for cellular functions that are essential in cell wall biogenesis, the maintenance of cell integrity, and survival at elevated temperature.
Collapse
Affiliation(s)
- Quan Zhong
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | | | | | | | | |
Collapse
|
23
|
Borkovich KA, Alex LA, Yarden O, Freitag M, Turner GE, Read ND, Seiler S, Bell-Pedersen D, Paietta J, Plesofsky N, Plamann M, Goodrich-Tanrikulu M, Schulte U, Mannhaupt G, Nargang FE, Radford A, Selitrennikoff C, Galagan JE, Dunlap JC, Loros JJ, Catcheside D, Inoue H, Aramayo R, Polymenis M, Selker EU, Sachs MS, Marzluf GA, Paulsen I, Davis R, Ebbole DJ, Zelter A, Kalkman ER, O'Rourke R, Bowring F, Yeadon J, Ishii C, Suzuki K, Sakai W, Pratt R. Lessons from the genome sequence of Neurospora crassa: tracing the path from genomic blueprint to multicellular organism. Microbiol Mol Biol Rev 2004; 68:1-108. [PMID: 15007097 PMCID: PMC362109 DOI: 10.1128/mmbr.68.1.1-108.2004] [Citation(s) in RCA: 434] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We present an analysis of over 1,100 of the approximately 10,000 predicted proteins encoded by the genome sequence of the filamentous fungus Neurospora crassa. Seven major areas of Neurospora genomics and biology are covered. First, the basic features of the genome, including the automated assembly, gene calls, and global gene analyses are summarized. The second section covers components of the centromere and kinetochore complexes, chromatin assembly and modification, and transcription and translation initiation factors. The third area discusses genome defense mechanisms, including repeat induced point mutation, quelling and meiotic silencing, and DNA repair and recombination. In the fourth section, topics relevant to metabolism and transport include extracellular digestion; membrane transporters; aspects of carbon, sulfur, nitrogen, and lipid metabolism; the mitochondrion and energy metabolism; the proteasome; and protein glycosylation, secretion, and endocytosis. Environmental sensing is the focus of the fifth section with a treatment of two-component systems; GTP-binding proteins; mitogen-activated protein, p21-activated, and germinal center kinases; calcium signaling; protein phosphatases; photobiology; circadian rhythms; and heat shock and stress responses. The sixth area of analysis is growth and development; it encompasses cell wall synthesis, proteins important for hyphal polarity, cytoskeletal components, the cyclin/cyclin-dependent kinase machinery, macroconidiation, meiosis, and the sexual cycle. The seventh section covers topics relevant to animal and plant pathogenesis and human disease. The results demonstrate that a large proportion of Neurospora genes do not have homologues in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. The group of unshared genes includes potential new targets for antifungals as well as loci implicated in human and plant physiology and disease.
Collapse
Affiliation(s)
- Katherine A Borkovich
- Department of Plant Pathology, University of California, Riverside, California 92521, USA. Katherine/
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Chavan M, Suzuki T, Rekowicz M, Lennarz W. Genetic, biochemical, and morphological evidence for the involvement of N-glycosylation in biosynthesis of the cell wall beta1,6-glucan of Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2003; 100:15381-6. [PMID: 14676317 PMCID: PMC307576 DOI: 10.1073/pnas.2536561100] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent evidence indicates that Stt3p plays a central role in the recognition and/or catalytic step in N-glycosylation (asparagine-linked glycosylation) in the lumen of the endoplasmic reticulum. It is known that stt3 mutants exhibit certain phenotypic features that are suggestive of a cell wall defect. To understand the basis of these phenotypes, we devised a genetic screen to isolate strains bearing mutations that lead to synthetic lethality in combination with the stt3-1 mutation. Using this screen, we were surprised to identify two KRE genes (KRE5 and KRE9) that are involved in the biosynthesis of the cell wall beta1,6-glucan. This finding led us to propose that the N-glycosylation process is essential in the biosynthesis of cell wall beta1,6-glucan. This proposal was supported by the observation that several stt3 mutants exhibited a 60-70% reduction in the content of cell wall beta1,6-glucan as compared with WT cells. Transmission electron microscopy revealed that the stt3 mutant strains exhibit a diffused cell wall with loss of the outer mannoprotein layer as compared with the WT cells. Thus, we provide genetic, morphological, and biochemical evidence for the critical involvement of N-glycosylation in some step in assembly of the cell wall beta1,6-glucan in Saccharomyces cerevisiae.
Collapse
Affiliation(s)
- Manasi Chavan
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | | | | | | |
Collapse
|
25
|
Pagé N, Gérard-Vincent M, Ménard P, Beaulieu M, Azuma M, Dijkgraaf GJP, Li H, Marcoux J, Nguyen T, Dowse T, Sdicu AM, Bussey H. A Saccharomyces cerevisiae genome-wide mutant screen for altered sensitivity to K1 killer toxin. Genetics 2003; 163:875-94. [PMID: 12663529 PMCID: PMC1462477 DOI: 10.1093/genetics/163.3.875] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using the set of Saccharomyces cerevisiae mutants individually deleted for 5718 yeast genes, we screened for altered sensitivity to the antifungal protein, K1 killer toxin, that binds to a cell wall beta-glucan receptor and subsequently forms lethal pores in the plasma membrane. Mutations in 268 genes, including 42 in genes of unknown function, had a phenotype, often mild, with 186 showing resistance and 82 hypersensitivity compared to wild type. Only 15 of these genes were previously known to cause a toxin phenotype when mutated. Mutants for 144 genes were analyzed for alkali-soluble beta-glucan levels; 63 showed alterations. Further, mutants for 118 genes with altered toxin sensitivity were screened for SDS, hygromycin B, and calcofluor white sensitivity as indicators of cell surface defects; 88 showed some additional defect. There is a markedly nonrandom functional distribution of the mutants. Many genes affect specific areas of cellular activity, including cell wall glucan and mannoprotein synthesis, secretory pathway trafficking, lipid and sterol biosynthesis, and cell surface signal transduction, and offer new insights into these processes and their integration.
Collapse
Affiliation(s)
- Nicolas Pagé
- Biology Department, McGill University, Montreal, Quebec H3A 1B1, Canada
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Kim SY, Sohn JH, Pyun YR, Choi ES. A cell surface display system using novel GPI-anchored proteins in Hansenula polymorpha. Yeast 2002; 19:1153-63. [PMID: 12237856 DOI: 10.1002/yea.911] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A cell surface display system was developed in yeast Hansenula polymorpha. The four genes HpSED1, HpGAS1, HpTIP1and HpCWP1, encoding glycosylphosphatidyl-inositol (GPI)-anchored cell surface proteins from H. polymorpha, were cloned, characterized and evaluated for their efficacies as cell surface display motifs of reporter proteins. Sequence analysis of these genes revealed that each encodes a typical GPI-anchored protein that is structurally similar to a counterpart gene in S. cerevisiae. The genes showed a high content of serine-threonine (alanine) and harboured a putative secretion signal in the N-terminus and the GPI-attachment signal in the C-terminus. The surface anchoring efficiency of these putative cell surface proteins was tested by fusion to the C-terminal of carboxymethylcellulase (CMCase) from Bacillus subtilis. In all cases, high CMCase activities were detected in intact cell fraction, indicating anchoring of CMCase to the cell surface. HpCwp1p, HpGas1p and the 40 C-terminal amino acids of HpTip1p from H. polymorpha exhibited a comparatively high CMCase surface anchoring efficiency. When these proteins were used as anchoring motifs for surface display of the glucose oxidase (GOD) from Aspergillus niger, most enzyme activity was detected at the cell surface. Fluorescence activated cell sorter (FACS) analysis of cells displaying GOD on the cell surface demonstrated that GOD was well exposed on the cell surface. HpCwp1p showed the highest anchoring efficiency among others.
Collapse
Affiliation(s)
- So-Young Kim
- Microbial Genomics Laboratory, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Yusong, Taejon 305-333, Korea
| | | | | | | |
Collapse
|
27
|
Li H, Pagé N, Bussey H. Actin patch assembly proteins Las17p and Sla1p restrict cell wall growth to daughter cells and interact with cis-Golgi protein Kre6p. Yeast 2002; 19:1097-112. [PMID: 12237851 DOI: 10.1002/yea.904] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cytoplasmic tail of Kre6p, a Golgi membrane protein involved in cell wall synthesis, interacts with the actin patch assembly components Las17p and Sla1p in a two-hybrid assay, and Kre6p co-immunoprecipitates with Las17p. Kre6p showed extensive co-localization with Och1p-containing cis-Golgi vesicles. The correct localization of Kre6p requires its cytoplasmic tail, Las17p, Sla1p and Vrp1p, suggesting that the cytoplasmic tail of Kre6p acts as a receptor, linking this cis-Golgi protein to Las17p and Sla1p. The actin patch assembly mutants las17 delta, sla1delta and vrp1 delta showed elevated levels of cell wall beta-1,6-glucan, and mutant cells were capable of only a limited number of cell divisions compared to wild-type. EM image analysis and beta-1,6-glucan localization indicated abnormal wall proliferation in the mother cells of these mutants. The pattern of cell wall hypertrophy indicates a failure to restrict cell wall growth to the bud.
Collapse
Affiliation(s)
- Huijuan Li
- Department of Biology, McGill University, Montreal H3A 1B1, Canada
| | | | | |
Collapse
|
28
|
Levinson JN, Shahinian S, Sdicu AM, Tessier DC, Bussey H. Functional, comparative and cell biological analysis ofSaccharomyces cerevisiae Kre5p. Yeast 2002; 19:1243-59. [PMID: 12271460 DOI: 10.1002/yea.908] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Saccharomyces cerevisiae kre5delta mutants lack beta-1,6-glucan, a polymer required for proper cell wall assembly and architecture. A functional and cell biological analysis of Kre5p was conducted to further elucidate the role of this diverged protein glucosyltransferase-like protein in beta-1,6-glucan synthesis. Kre5p was found to be a primarily soluble N-glycoprotein of approximately 200 kDa, that localizes to the endoplasmic reticulum. The terminal phenotype of Kre5p-deficient cells was observed, and revealed a severe cell wall morphological defect. KRE6, encoding a glucanase-like protein, was identified as a multicopy suppressor of a temperature-sensitive kre5 allele, suggesting that these proteins may participate in a common beta-1,6-biosynthetic pathway. An analysis of truncated versions of Kre5p indicated that all major regions of the protein are required for viability. Finally, Candida albicans KRE5 was shown to partially restore growth to S. cerevisiae kre5delta cells, suggesting that these proteins are functionally related.
Collapse
Affiliation(s)
- Joshua N Levinson
- Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1
| | | | | | | | | |
Collapse
|
29
|
Harkins HA, Pagé N, Schenkman LR, De Virgilio C, Shaw S, Bussey H, Pringle JR. Bud8p and Bud9p, proteins that may mark the sites for bipolar budding in yeast. Mol Biol Cell 2001; 12:2497-518. [PMID: 11514631 PMCID: PMC58609 DOI: 10.1091/mbc.12.8.2497] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2000] [Revised: 04/10/2001] [Accepted: 04/25/2001] [Indexed: 11/11/2022] Open
Abstract
The bipolar budding pattern of a/alpha Saccharomyces cerevisiae cells appears to depend on persistent spatial markers in the cell cortex at the two poles of the cell. Previous analysis of mutants with specific defects in bipolar budding identified BUD8 and BUD9 as potentially encoding components of the markers at the poles distal and proximal to the birth scar, respectively. Further genetic analysis reported here supports this hypothesis. Mutants deleted for BUD8 or BUD9 grow normally but bud exclusively from the proximal and distal poles, respectively, and the double-mutant phenotype suggests that the bipolar budding pathway has been totally disabled. Moreover, overexpression of these genes can cause either an increased bias for budding at the distal (BUD8) or proximal (BUD9) pole or a randomization of bud position, depending on the level of expression. The structures and localizations of Bud8p and Bud9p are also consistent with their postulated roles as cortical markers. Both proteins appear to be integral membrane proteins of the plasma membrane, and they have very similar overall structures, with long N-terminal domains that are both N- and O-glycosylated followed by a pair of putative transmembrane domains surrounding a short hydrophilic domain that is presumably cytoplasmic. The putative transmembrane and cytoplasmic domains of the two proteins are very similar in sequence. When Bud8p and Bud9p were localized by immunofluorescence and tagging with GFP, each protein was found predominantly in the expected location, with Bud8p at presumptive bud sites, bud tips, and the distal poles of daughter cells and Bud9p at the necks of large-budded cells and the proximal poles of daughter cells. Bud8p localized approximately normally in several mutants in which daughter cells are competent to form their first buds at the distal pole, but it was not detected in a bni1 mutant, in which such distal-pole budding is lost. Surprisingly, Bud8p localization to the presumptive bud site and bud tip also depends on actin but is independent of the septins.
Collapse
Affiliation(s)
- H A Harkins
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | | | | | | | | | | | | |
Collapse
|
30
|
Murray AK, Nichols RL, Sassenrath-Cole GF. Cell wall biosynthesis: glycan containing oligomers in developing cotton fibers, cotton fabric, wood and paper. PHYTOCHEMISTRY 2001; 57:975-986. [PMID: 11423144 DOI: 10.1016/s0031-9422(01)00143-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A series of oligomeric glycans can be extracted from the cell walls of developing cotton fibers with weak acid. Glycans that produce similar profiles on high pH anion chromatography with pulsed amperometric detection (HPAEC-PAD) are also found in a protein complex extracted from developing fibers and in amorphous aggregates found in association with immature fibers in developing, but not in mature cotton bolls. The quantity and composition of the glycans recovered from the carbohydrate-protein complex varies significantly with the time of day when the bolls are harvested. This diurnal variation is consistent with the hypothesis that secondary cell walls are deposited primarily at night. Incubation of re-hydrated cotton fibers in the presence of exogenous oligosaccharides, myo-inositol and glycerol substantially alters the apparent quantity of the oligomers extracted from the fibers. The same and similar glycans have also been extracted from cotton fabric, marine algae, various paper products and wood. While many of the oligomers isolated from the various cellulose sources display the same peaks by HPAEC-PAD, the specific number of oligomers and their relative quantities appear unique for each source of cellulosic material. Oligomeric glycans, as described in the preceding, are present in all cellulose sources that have been investigated. Their relative abundance changes in response to source, stage of development and other physiological variables. We hypothesize that the glycans are intermediates in the biological assembly of cellulose, and that their incorporation in cellulose is mediated by physicochemical and enzymatic mechanisms.
Collapse
Affiliation(s)
- A K Murray
- Glycozyme, Inc., 17935 Sky Park Circle, Ste. E, Irvine, CA 92614, USA.
| | | | | |
Collapse
|
31
|
Abstract
The N-glycans found on eukaryotic glycoproteins occur in a vast range of different structures. A universal N-glycan core is attached to proteins during synthesis in the endoplasmic reticulum, and then diversity is generated as the proteins pass through the Golgi apparatus. Many of the Golgi-localised glycosyltransferases have now been identified in both yeast and mammalian cells, but it is still unclear how these enzymes are integrated into the Golgi and the rest of the cell so as to ensure efficient and specific processing of passing substrates. This review discusses the potential of the yeast system to address these issues.
Collapse
Affiliation(s)
- S Munro
- Medical Research Council Laboratory of Molecular Biology, Hills Road, CB2 2QH, Cambridge, UK.
| |
Collapse
|
32
|
Abstract
beta-1,6-Glucan is an essential fungal-specific component of the Saccharomyces cerevisiae cell wall that interconnects all other wall components into a lattice. Considerable biochemical and genetic effort has been directed at the identification and characterization of the steps involved in its biosynthesis. Structural studies show that the polymer plays a central role in wall structure, attaching mannoproteins via their glycosylphosphatidylinositol (GPI) glycan remnant to beta-1,3-glucan and chitin. Genetic approaches have identified genes that upon disruption result in beta-1,6-glucan defects of varying severity, often with reduced growth or lethality. These gene products have been localized throughout the secretory pathway and at the cell surface, suggesting a possible biosynthetic route. Current structural and genetic data have therefore allowed the development of models to predict biosynthetic events. Based on knowledge of beta-1,3-glucan and chitin synthesis, it is likely that the bulk of beta-1,6-glucan polymer synthesis occurs at the cell surface, but requires key prior intracellular events. However, the activity of most of the identified gene products remain unknown, making it unclear to what extent and how directly they contribute to the synthesis of this polymer. With the recent availability of new tools, reagents and methods (including genomics), the field is poised for a convergence of biochemical and genetic methods to identify and characterize the biochemical steps in the synthesis of this polymer.
Collapse
Affiliation(s)
- S Shahinian
- Department of Biology, McGill University, 1205 Dr Penfield Avenue, Montréal, Québec H3A 1B1, Canada
| | | |
Collapse
|
33
|
Montijn RC, Vink E, Müller WH, Verkleij AJ, Van Den Ende H, Henrissat B, Klis FM. Localization of synthesis of beta1,6-glucan in Saccharomyces cerevisiae. J Bacteriol 1999; 181:7414-20. [PMID: 10601196 PMCID: PMC94196 DOI: 10.1128/jb.181.24.7414-7420.1999] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Beta1,6-Glucan is a key component of the yeast cell wall, interconnecting cell wall proteins, beta1,3-glucan, and chitin. It has been postulated that the synthesis of beta1,6-glucan begins in the endoplasmic reticulum with the formation of protein-bound primer structures and that these primer structures are extended in the Golgi complex by two putative glucosyltransferases that are functionally redundant, Kre6 and Skn1. This is followed by maturation steps at the cell surface and by coupling to other cell wall macromolecules. We have reinvestigated the role of Kre6 and Skn1 in the biogenesis of beta1,6-glucan. Using hydrophobic cluster analysis, we found that Kre6 and Skn1 show significant similarities to family 16 glycoside hydrolases but not to nucleotide diphospho-sugar glycosyltransferases, indicating that they are glucosyl hydrolases or transglucosylases instead of genuine glucosyltransferases. Next, using immunogold labeling, we tried to visualize intracellular beta1,6-glucan in cryofixed sec1-1 cells which had accumulated secretory vesicles at the restrictive temperature. No intracellular labeling was observed, but the cell surface was heavily labeled. Consistent with this, we could detect substantial amounts of beta1,6-glucan in isolated plasma membrane-derived microsomes but not in post-Golgi secretory vesicles. Taken together, our data indicate that the synthesis of beta1, 6-glucan takes place largely at the cell surface. An alternative function for Kre6 and Skn1 is discussed.
Collapse
Affiliation(s)
- R C Montijn
- Swammerdam Institute of Life Science, University of Amsterdam, BioCentrum Amsterdam, Amsterdam 1098 SM, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
34
|
Zapun A, Jakob CA, Thomas DY, Bergeron JJ. Protein folding in a specialized compartment: the endoplasmic reticulum. Structure 1999; 7:R173-82. [PMID: 10467145 DOI: 10.1016/s0969-2126(99)80112-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The endoplasmic reticulum ensures proper folding of secretory proteins. In this review, we summarize and discuss the functions of different classes of folding mediators in the secretory pathway and propose updated models of the quality control system.
Collapse
Affiliation(s)
- A Zapun
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | | | | | | |
Collapse
|
35
|
Castro O, Chen LY, Parodi AJ, Abeijón C. Uridine diphosphate-glucose transport into the endoplasmic reticulum of Saccharomyces cerevisiae: in vivo and in vitro evidence. Mol Biol Cell 1999; 10:1019-30. [PMID: 10198054 PMCID: PMC25230 DOI: 10.1091/mbc.10.4.1019] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
It has been proposed that synthesis of beta-1,6-glucan, one of Saccharomyces cerevisiae cell wall components, is initiated by a uridine diphosphate (UDP)-glucose-dependent reaction in the lumen of the endoplasmic reticulum (ER). Because this sugar nucleotide is not synthesized in the lumen of the ER, we have examined whether or not UDP-glucose can be transported across the ER membrane. We have detected transport of this sugar nucleotide into the ER in vivo and into ER-containing microsomes in vitro. Experiments with ER-containing microsomes showed that transport of UDP-glucose was temperature dependent and saturable with an apparent Km of 46 microM and a Vmax of 200 pmol/mg protein/3 min. Transport was substrate specific because UDP-N-acetylglucosamine did not enter these vesicles. Demonstration of UDP-glucose transport into the ER lumen in vivo was accomplished by functional expression of Schizosaccharomyces pombe UDP-glucose:glycoprotein glucosyltransferase (GT) in S. cerevisiae, which is devoid of this activity. Monoglucosylated protein-linked oligosaccharides were detected in alg6 or alg5 mutant cells, which transfer Man9GlcNAc2 to protein; glucosylation was dependent on the inhibition of glucosidase II or the disruption of the gene encoding this enzyme. Although S. cerevisiae lacks GT, it contains Kre5p, a protein with significant homology and the same size and subcellular location as GT. Deletion mutants, kre5Delta, lack cell wall beta-1,6 glucan and grow very slowly. Expression of S. pombe GT in kre5Delta mutants did not complement the slow-growth phenotype, indicating that both proteins have different functions in spite of their similarities.
Collapse
Affiliation(s)
- O Castro
- Instituto de Investigaciones Bioquímicas Fundación Campomar, 1405 Buenos Aires, Argentina
| | | | | | | |
Collapse
|
36
|
Kapteyn JC, Van Egmond P, Sievi E, Van Den Ende H, Makarow M, Klis FM. The contribution of the O-glycosylated protein Pir2p/Hsp150 to the construction of the yeast cell wall in wild-type cells and beta 1,6-glucan-deficient mutants. Mol Microbiol 1999; 31:1835-44. [PMID: 10209754 DOI: 10.1046/j.1365-2958.1999.01320.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cell wall of yeast contains a major structural unit, consisting of a cell wall protein (CWP) attached via a glycosylphosphatidylinositol (GPI)-derived structure to beta 1,6-glucan, which is linked in turn to beta 1, 3-glucan. When isolated cells walls were digested with beta 1,6-glucanase, 16% of all CWPs remained insoluble, suggesting an alternative linkage between CWPs and structural cell wall components that does not involve beta 1,6-glucan. The beta 1,6-glucanase-resistant protein fraction contained the recently identified GPI-lacking, O-glycosylated Pir-CWPs, including Pir2p/Hsp150. Evidence is presented that Pir2p/Hsp150 is attached to beta 1,3-glucan through an alkali-sensitive linkage, without beta 1,6-glucan as an interconnecting moiety. In beta 1,6-glucan-deficient mutants, the beta 1,6-glucanase-resistant protein fraction increased from 16% to over 80%. This was accompanied by increased incorporation of Pir2p/Hsp150. It is argued that this is part of a more general compensatory mechanism in response to cell wall weakening caused by low levels of beta 1,6-glucan.
Collapse
Affiliation(s)
- J C Kapteyn
- Center for Fungal Cell Wall Research, University of Amsterdam, The Netherlands.
| | | | | | | | | | | |
Collapse
|
37
|
Abstract
The properties of the N-glycan processing glycosidases located in the endoplasmic reticulum of Saccharomyces cerevisiae are described. alpha-Glucosidase I encoded by CWH41 cleaves the terminal alpha1, 2-linked glucose and alpha-glucosidase II encoded by ROT2 removes the two alpha1,3-linked glucose residues from the Glc3Man9GlcNAc2 oligosaccharide precursor while the alpha1,2-mannosidase encoded by MNS1 removes one specific mannose to form a single isomer of Man8GlcNAc2. Although trimming by these glycosidases is not essential for the formation of N-glycan outer chains, recent studies on mutants lacking these enzymes indicate that alpha-glucosidases I and II play an indirect role in cell wall beta1,6-glucan formation and that the alpha1,2-mannosidase is involved in endoplasmic reticulum quality control. Detailed structure-function studies of recombinant yeast alpha1,2-mannosidase are described that serve as a model for other members of this enzyme family that has been conserved through eukaryotic evolution.
Collapse
Affiliation(s)
- A Herscovics
- McGill Cancer Centre, McGill University, 3655 Drummond Street, Montreal, Que. H3G 1Y6, Canada.
| |
Collapse
|
38
|
Nagahashi S, Lussier M, Bussey H. Isolation of Candida glabrata homologs of the Saccharomyces cerevisiae KRE9 and KNH1 genes and their involvement in cell wall beta-1,6-glucan synthesis. J Bacteriol 1998; 180:5020-9. [PMID: 9748432 PMCID: PMC107535 DOI: 10.1128/jb.180.19.5020-5029.1998] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/1998] [Accepted: 07/28/1998] [Indexed: 11/20/2022] Open
Abstract
The Candida glabrata KRE9 (CgKRE9) and KNH1 (CgKNH1) genes have been isolated as multicopy suppressors of the tetracycline-sensitive growth of a Saccharomyces cerevisiae mutant with the disrupted KNH1 locus and the KRE9 gene placed under the control of a tetracycline-responsive promoter. Although a cgknh1Delta mutant showed no phenotype beyond slightly increased sensitivity to the K1 killer toxin, disruption of CgKRE9 resulted in several phenotypes similar to those of the S. cerevisiae kre9Delta null mutant: a severe growth defect on glucose medium, resistance to the K1 killer toxin, a 50% reduction of beta-1,6-glucan, and the presence of aggregates of cells with abnormal morphology on glucose medium. Replacement in C. glabrata of the cognate CgKRE9 promoter with the tetracycline-responsive promoter in a cgknh1Delta background rendered cell growth tetracycline sensitive on media containing glucose or galactose. cgkre9Delta cells were shown to be sensitive to calcofluor white specifically on glucose medium. In cgkre9 mutants grown on glucose medium, cellular chitin levels were massively increased.
Collapse
Affiliation(s)
- S Nagahashi
- Department of Biology, McGill University, Montréal, Quebec, Canada H3A 1B1
| | | | | |
Collapse
|