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Seyedmousavi S, Guillot J, Arné P, de Hoog GS, Mouton JW, Melchers WJG, Verweij PE. Aspergillus and aspergilloses in wild and domestic animals: a global health concern with parallels to human disease. Med Mycol 2015; 53:765-97. [PMID: 26316211 DOI: 10.1093/mmy/myv067] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 06/30/2015] [Indexed: 12/22/2022] Open
Abstract
The importance of aspergillosis in humans and various animal species has increased over the last decades. Aspergillus species are found worldwide in humans and in almost all domestic animals and birds as well as in many wild species, causing a wide range of diseases from localized infections to fatal disseminated diseases, as well as allergic responses to inhaled conidia. Some prevalent forms of animal aspergillosis are invasive fatal infections in sea fan corals, stonebrood mummification in honey bees, pulmonary and air sac infection in birds, mycotic abortion and mammary gland infections in cattle, guttural pouch mycoses in horses, sinonasal infections in dogs and cats, and invasive pulmonary and cerebral infections in marine mammals and nonhuman primates. This article represents a comprehensive overview of the most common infections reported by Aspergillus species and the corresponding diseases in various types of animals.
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Affiliation(s)
- Seyedmojtaba Seyedmousavi
- Department of Medical Microbiology and Infectious Diseases, ErasmusMC, the Netherlands Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, the Netherlands Invasive Fungi Research Center, Mazandaran University of Medical Sciences, Sari, Iran
| | - Jacques Guillot
- Department of Parasitology-Mycology, Dynamyc Research Group, EnvA, UPEC, UPE, École Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
| | - Pascal Arné
- Department of Animal Production, Dynamyc Research Group, EnvA, UPEC, UPE, École Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
| | - G Sybren de Hoog
- CBS-KNAW Fungal Biodiversity Centre, Utrecht, the Netherlands, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, the Netherlands, Peking University Health Science Center, Research Center for Medical Mycology, Beijing, China, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China, and King Abdullaziz University, Jeddah, Saudi Arabia
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, ErasmusMC, the Netherlands Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Willem J G Melchers
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - Paul E Verweij
- Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, the Netherlands
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Rocha MC, de Godoy KF, de Castro PA, Hori JI, Bom VLP, Brown NA, da Cunha AF, Goldman GH, Malavazi I. The Aspergillus fumigatus pkcA G579R Mutant Is Defective in the Activation of the Cell Wall Integrity Pathway but Is Dispensable for Virulence in a Neutropenic Mouse Infection Model. PLoS One 2015; 10:e0135195. [PMID: 26295576 PMCID: PMC4546635 DOI: 10.1371/journal.pone.0135195] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/19/2015] [Indexed: 12/03/2022] Open
Abstract
Aspergillus fumigatus is an opportunistic human pathogen, which causes the life-threatening disease, invasive pulmonary aspergillosis. In fungi, cell wall homeostasis is controlled by the conserved Cell Wall Integrity (CWI) pathway. In A. fumigatus this signaling cascade is partially characterized, but the mechanisms by which it is activated are not fully elucidated. In this study we investigated the role of protein kinase C (PkcA) in this signaling cascade. Our results suggest that pkcA is an essential gene and is activated in response to cell wall stress. Subsequently, we constructed and analyzed a non-essential A. fumigatus pkcAG579R mutant, carrying a Gly579Arg substitution in the PkcA C1B regulatory domain. The pkcAG579R mutation has a reduced activation of the downstream Mitogen-Activated Protein Kinase, MpkA, resulting in the altered expression of genes encoding cell wall-related proteins, markers of endoplasmic reticulum stress and the unfolded protein response. Furthermore, PkcAG579R is involved in the formation of proper conidial architecture and protection to oxidative damage. The pkcAG579R mutant elicits increased production of TNF-α and phagocytosis but it has no impact on virulence in a murine model of invasive pulmonary aspergillosis. These results highlight the importance of PkcA to the CWI pathway but also indicated that additional regulatory circuits may be involved in the biosynthesis and/or reinforcement of the A. fumigatus cell wall during infection.
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Affiliation(s)
- Marina Campos Rocha
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Krissia Franco de Godoy
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Patrícia Alves de Castro
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Juliana Issa Hori
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Vinícius Leite Pedro Bom
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Neil Andrew Brown
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts, United Kingdom
| | - Anderson Ferreira da Cunha
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Gustavo Henrique Goldman
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol, Campinas, São Paulo, Brazil
| | - Iran Malavazi
- Departamento de Genética e Evolução, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
- * E-mail:
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53
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Fan F, Ma G, Li J, Liu Q, Benz JP, Tian C, Ma Y. Genome-wide analysis of the endoplasmic reticulum stress response during lignocellulase production in Neurospora crassa. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:66. [PMID: 25883682 PMCID: PMC4399147 DOI: 10.1186/s13068-015-0248-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 03/27/2015] [Indexed: 05/05/2023]
Abstract
BACKGROUND Lignocellulolytic fungal cells suffer endoplasmic reticulum (ER) stress during lignocellulase synthesis; however, an understanding of this integrated process on a genome-wide scale remains poor. Here, we undertook a systematic investigation of this process in Neurospora crassa (N. crassa) using transcriptomic analysis coupled with genetic screens. RESULTS A set of 766 genes was identified as the ER stress response targets (ESRTs) in N. crassa under cellulose utilization conditions. Among these, the expression of 223 and 186 genes showed dependence on IRE-1 and HAC-1, respectively. A total of 527 available mutants for ESRT genes were screened, 249 of which exhibited ER stress susceptibility, including 100 genes with unknown function. Disruption of ire-1 or hac-1 in N. crassa did not affect transcriptional induction of lignocellulase genes by cellulose but severely affected secretion of the corresponding enzymes. A global investigation of transcription factors (TFs) discovered three novel regulators (RES-1, RES-2, RRG-2) involved in lignocellulase secretion. Production of lignocellulases in Δres-1 increased by more than 30% in comparison to wild type (WT), while secretion decreased by nearly 30% in strains Δres-2 and Δrrg-2. Transcriptional profiling of the three TF mutants suggests they are deeply involved in lignocellulase secretion and ER stress response. CONCLUSIONS Here, we determined the transcriptional scope of the ER stress response during lignocellulase synthesis in the model cellulolytic fungus N. crassa. Through genome-wide mutant screening and analysis, dozens of novel genes were discovered to be involved in the process. The findings of this work will be useful for strain improvement to facilitate lignocellulase and biomass-based chemical production.
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Affiliation(s)
- Feiyu Fan
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
- />University of Chinese Academy of Sciences, Yuquan Road, Beijing, 100049 China
| | - Guoli Ma
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
- />University of Chinese Academy of Sciences, Yuquan Road, Beijing, 100049 China
| | - Jingen Li
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
- />University of Chinese Academy of Sciences, Yuquan Road, Beijing, 100049 China
| | - Qian Liu
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
| | - Johan Philipp Benz
- />Holzforschung München, TUM School of Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, Germany
| | - Chaoguang Tian
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
| | - Yanhe Ma
- />Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Xiqi Dao32, Tianjin Airport Economic Area, Tianjin 300308 China
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Heimel K. Unfolded protein response in filamentous fungi-implications in biotechnology. Appl Microbiol Biotechnol 2014; 99:121-32. [PMID: 25384707 DOI: 10.1007/s00253-014-6192-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 01/16/2023]
Abstract
The unfolded protein response (UPR) represents a mechanism to preserve endoplasmic reticulum (ER) homeostasis that is conserved in eukaryotes. ER stress caused by the accumulation of potentially toxic un- or misfolded proteins in the ER triggers UPR activation and the induction of genes important for protein folding in the ER, ER expansion, and transport from and to the ER. Along with this adaptation, the overall capacity for protein secretion is markedly increased by the UPR. In filamentous fungi, various approaches to employ the UPR for improved production of homologous and heterologous proteins have been investigated. As the effects on protein production were strongly dependent on the expressed protein, generally applicable strategies have to be developed. A combination of transcriptomic approaches monitoring secretion stress and basic research on the UPR mechanism provided novel and important insight into the complex regulatory cross-connections between UPR signalling, cellular physiology, and developmental processes. It will be discussed how this increasing knowledge on the UPR might stimulate the development of novel strategies for using the UPR as a tool in biotechnology.
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Affiliation(s)
- Kai Heimel
- Institut für Mikrobiologie & Genetik, Georg-August-Universität, Grisebachstr. 8, 37077, Göttingen, Germany,
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Sugui JA, Kwon-Chung KJ, Juvvadi PR, Latgé JP, Steinbach WJ. Aspergillus fumigatus and related species. Cold Spring Harb Perspect Med 2014; 5:a019786. [PMID: 25377144 DOI: 10.1101/cshperspect.a019786] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The genus Aspergillus contains etiologic agents of aspergillosis. The clinical manifestations of the disease range from allergic reaction to invasive pulmonary infection. Among the pathogenic aspergilli, Aspergillus fumigatus is most ubiquitous in the environment and is the major cause of the disease, followed by Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Aspergillus nidulans, and several species in the section Fumigati that morphologically resemble A. fumigatus. Patients that are at risk for acquiring aspergillosis are those with an altered immune system. Early diagnosis, species identification, and adequate antifungal therapy are key elements for treatment of the disease, especially in cases of pulmonary invasive aspergillosis that often advance very rapidly. Incorporating knowledge of the basic biology of Aspergillus species to that of the diseases that they cause is fundamental for further progress in the field.
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Affiliation(s)
- Janyce A Sugui
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Kyung J Kwon-Chung
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Praveen R Juvvadi
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University, Durham, North Carolina 27715
| | - Jean-Paul Latgé
- Unité des Aspergillus, Institut Pasteur, Paris 75724, France
| | - William J Steinbach
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University, Durham, North Carolina 27715 Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina 27710
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Abstract
Siderophores are chelators synthesized by microbes to sequester iron. This article summarizes the knowledge on the fungal siderophore metabolism with a focus on Aspergillus fumigatus. In recent years, A. fumigatus became a role model for fungal biosynthesis, uptake and degradation of siderophores as well as regulation of siderophore-mediated iron handling and the elucidation of siderophore functions. Siderophore functions comprise uptake, intracellular transport and storage of iron. This proved to be crucial not only for adaptation to iron starvation conditions but also for germination, asexual and sexual propagation, antioxidative defense, mutual interaction, microbial competition as well as virulence in plant and animal hosts. Recent studies also indicate the high potential of siderophores and its biosynthetic pathway to improve diagnosis and therapy of fungal infections.
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Affiliation(s)
- Hubertus Haas
- Division of Molecular Biology/Biocenter, Innsbruck Medical University, Innrain 80-82, A-6020 Innsbruck, Austria.
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57
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Abstract
The gateway to the secretory pathway is the endoplasmic reticulum (ER), an organelle that is responsible for the accurate folding, post-translational modification and final assembly of up to a third of the cellular proteome. When secretion levels are high, errors in protein biogenesis can lead to the accumulation of abnormally folded proteins, which threaten ER homeostasis. The unfolded protein response (UPR) is an adaptive signaling pathway that counters a buildup in misfolded and unfolded proteins by increasing the expression of genes that support ER protein folding capacity. Fungi, like other eukaryotic cells that are specialized for secretion, rely upon the UPR to buffer ER stress caused by fluctuations in secretory demand. However, emerging evidence is also implicating the UPR as a central regulator of fungal pathogenesis. In this review, we discuss how diverse fungal pathogens have adapted ER stress response pathways to support the expression of virulence-related traits that are necessary in the host environment.
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Affiliation(s)
- Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267-0529
| | - David S Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267-0529
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Blosser SJ, Merriman B, Grahl N, Chung D, Cramer RA. Two C4-sterol methyl oxidases (Erg25) catalyse ergosterol intermediate demethylation and impact environmental stress adaptation in Aspergillus fumigatus. MICROBIOLOGY-SGM 2014; 160:2492-2506. [PMID: 25107308 DOI: 10.1099/mic.0.080440-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The human pathogen Aspergillus fumigatus adapts to stress encountered in the mammalian host as part of its ability to cause disease. The transcription factor SrbA plays a significant role in this process by regulating genes involved in hypoxia and low-iron adaptation, antifungal drug responses and virulence. SrbA is a direct transcriptional regulator of genes encoding key enzymes in the ergosterol biosynthesis pathway, including erg25A and erg25B, and ΔsrbA accumulates C4-methyl sterols, suggesting a loss of Erg25 activity [C4-sterol methyl oxidase (SMO)]. Characterization of the two genes encoding SMOs in Aspergillus fumigatus revealed that both serve as functional C4-demethylases, with Erg25A serving in a primary role, as Δerg25A accumulates more C4-methyl sterol intermediates than Δerg25B. Single deletion of these SMOs revealed alterations in canonical ergosterol biosynthesis, indicating that ergosterol may be produced in an alternative fashion in the absence of SMO activity. A Δerg25A strain displayed moderate susceptibility to hypoxia and the endoplasmic reticulum stress-inducing agent DTT, but was not required for virulence in murine or insect models of invasive aspergillosis. Inducing expression of erg25A partially restored the hypoxia growth defect of ΔsrbA. These findings implicated Aspergillus fumigatus SMOs in the maintenance of canonical ergosterol biosynthesis and indicated an overall involvement in the fungal stress response.
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Affiliation(s)
- Sara J Blosser
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, USA
| | - Brittney Merriman
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, USA
| | - Nora Grahl
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, USA
| | - Dawoon Chung
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, USA
| | - Robert A Cramer
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, USA
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Malavazi I, Goldman GH, Brown NA. The importance of connections between the cell wall integrity pathway and the unfolded protein response in filamentous fungi. Brief Funct Genomics 2014; 13:456-70. [PMID: 25060881 DOI: 10.1093/bfgp/elu027] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the external environment, or within a host organism, filamentous fungi experience sudden changes in nutrient availability, osmolality, pH, temperature and the exposure to toxic compounds. The fungal cell wall represents the first line of defense, while also performing essential roles in morphology, development and virulence. A polarized secretion system is paramount for cell wall biosynthesis, filamentous growth, nutrient acquisition and interactions with the environment. The unique ability of filamentous fungi to secrete has resulted in their industrial adoption as fungal cell factories. Protein maturation and secretion commences in the endoplasmic reticulum (ER). The unfolded protein response (UPR) maintains ER functionality during exposure to secretion and cell wall stress. UPR, therefore, influences secretion and cell wall homeostasis, which in turn impacts upon numerous fungal traits important to pathogenesis and biotechnology. Subsequently, this review describes the relevance of the cell wall and UPR systems to filamentous fungal pathogens or industrial microbes and then highlights interconnections between the two systems. Ultimately, the possible biotechnological applications of an enhanced understanding of such regulatory systems in combating fungal disease, or the removal of natural bottlenecks in protein secretion in an industrial setting, are discussed.
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Eosinophils are recruited in response to chitin exposure and enhance Th2-mediated immune pathology in Aspergillus fumigatus infection. Infect Immun 2014; 82:3199-205. [PMID: 24842927 DOI: 10.1128/iai.01990-14] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
In patients infected with the fungus Aspergillus fumigatus, Th1 responses are considered protective, while Th2 responses are associated with increased morbidity and mortality. How host-pathogen interactions influence the development of these protective or detrimental immune responses is not clear. We compared lung immune responses to conidia from two fungal isolates that expressed different levels of the fungal cell wall component chitin. We observed that repeated aspirations of the high-chitin-expressing isolate Af5517 induced increased airway eosinophilia in the lungs of recipient mice compared to the level of eosinophilia induced by isolate Af293. CD4(+) T cells in the bronchoalveolar lavage fluid (BALF) of Af5517-aspirated mice displayed decreased gamma interferon secretion and increased interleukin-4 transcription. In addition, repeated aspirations of Af5517 induced lung transcription of the Th2-associated chemokines CCL11 (eotaxin-1) and CCL22 (macrophage-derived chemokine). Eosinophil recruitment in response to conidial aspiration was correlated with the level of chitin exposure during germination and was decreased by constitutive lung chitinase expression. Moreover, eosinophil-deficient mice subjected to multiple aspirations of Af5517 prior to neutrophil depletion and infection exhibited decreased morbidity and fungal burden compared to the levels of morbidity and fungal burden found in wild-type mice. These results suggest that exposure of chitin in germinating conidia promotes eosinophil recruitment and ultimately induces Th2-skewed immune responses after repeated aspiration. Furthermore, our results suggest that eosinophils should be examined as a potential therapeutic target in patients that mount poorly protective Th2 responses to A. fumigatus infection.
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Krishnan K, Ren Z, Losada L, Nierman WC, Lu LJ, Askew DS. Polysome profiling reveals broad translatome remodeling during endoplasmic reticulum (ER) stress in the pathogenic fungus Aspergillus fumigatus. BMC Genomics 2014; 15:159. [PMID: 24568630 PMCID: PMC3943501 DOI: 10.1186/1471-2164-15-159] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/17/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The unfolded protein response (UPR) is a network of intracellular signaling pathways that supports the ability of the secretory pathway to maintain a balance between the load of proteins entering the endoplasmic reticulum (ER) and the protein folding capacity of the ER lumen. Current evidence indicates that several pathogenic fungi rely heavily on this pathway for virulence, but there is limited understanding of the mechanisms involved. The best known functional output of the UPR is transcriptional upregulation of mRNAs involved in ER homeostasis. However, this does not take into account mechanisms of translational regulation that involve differential loading of ribosomes onto mRNAs. In this study, a global analysis of transcript-specific translational regulation was performed in the pathogenic mold Aspergillus fumigatus to determine the nature and scope of the translational response to ER stress. RESULTS ER stress was induced by treating the fungus with dithiothreitol, tunicamycin, or a thermal up-shift. The mRNAs were then fractionated on the basis of ribosome occupancy into an under-translated pool (U) and a well-translated pool (W). The mRNAs were used to interrogate microarrays and the ratio of the hybridization signal (W/U) was used as an indicator of the relative translational efficiency of a mRNA under each condition. The largest category of translationally upregulated mRNAs during ER stress encoded proteins involved in translation. Components of the ergosterol and GPI anchor biosynthetic pathways also showed increased polysome association, suggesting an important role for translational regulation in membrane and cell wall homeostasis. ER stress induced limited remodeling of the secretory pathway translatome. However, a select group of transcription factors was translationally upregulated, providing a link to subsequent modification of the transcriptome. Finally, we provide evidence that one component of the ER stress translatome is a novel mRNA isoform from the yvc1 gene that is induced by ER stress in a UPR-dependent manner. CONCLUSIONS Together, these findings define a core set of mRNAs subject to translational control during the adaptive response to acute ER stress in A. fumigatus and reveal a remarkable breadth of functions that are needed to resolve ER stress in this organism.
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Affiliation(s)
| | | | | | | | | | - David S Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0529, USA.
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Guillemette T, Calmes B, Simoneau P. Impact of the UPR on the virulence of the plant fungal pathogen A. brassicicola. Virulence 2014; 5:357-64. [PMID: 24189567 PMCID: PMC3956514 DOI: 10.4161/viru.26772] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 10/10/2013] [Accepted: 10/10/2013] [Indexed: 11/19/2022] Open
Abstract
The fungal genus Alternaria contains many destructive plant pathogens, including Alternaria brassicicola, which causes black spot disease on a wide range of Brassicaceae plants and which is routinely used as a model necrotrophic pathogen in studies with Arabidopsis thaliana. During host infection, many fungal proteins that are critical for disease progression are processed in the endoplasmic reticulum (ER)/Golgi system and secreted in planta. The unfolded protein response (UPR) is an essential part of ER protein quality control that ensures efficient maturation of secreted and membrane-bound proteins in eukaryotes. This review highlights the importance of the UPR signaling pathway with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle. Understanding the pathogenicity mechanisms that fungi uses during infection is crucial for the development of new antifungal therapies. Therefore the UPR pathway has emerged as a promising drug target for plant disease control.
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Affiliation(s)
- Thomas Guillemette
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Benoit Calmes
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Philippe Simoneau
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
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63
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Affiliation(s)
- David S Askew
- Department of Pathology & Laboratory Medicine; University of Cincinnati; Cincinnati, OH USA
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Jiang H, Shen Y, Liu W, Lu L. Deletion of the putative stretch-activated ion channel Mid1 is hypervirulent in Aspergillus fumigatus. Fungal Genet Biol 2014; 62:62-70. [DOI: 10.1016/j.fgb.2013.11.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/04/2013] [Accepted: 11/07/2013] [Indexed: 12/22/2022]
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65
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Miyazaki T, Kohno S. ER stress response mechanisms in the pathogenic yeast Candida glabrata and their roles in virulence. Virulence 2013; 5:365-70. [PMID: 24335436 PMCID: PMC3956515 DOI: 10.4161/viru.27373] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The maintenance of endoplasmic reticulum (ER) homeostasis is critical for numerous aspects of cell physiology. Eukaryotic cells respond to the accumulation of misfolded proteins in the ER (ER stress) by activating the unfolded protein response (UPR), an intracellular signaling pathway that adjusts the folding capacity of the ER. Recent studies of several pathogenic fungi have revealed that the UPR is important for antifungal resistance and virulence; therefore, the pathway has attracted much attention as a potential therapeutic target. While the UPR is highly conserved among eukaryotes, our group recently discovered that the pathogenic yeast Candida glabrata lacks the typical fungal UPR, but possesses alternative mechanisms to cope with ER stress. This review summarizes how C. glabrata responds to ER stress and discusses the impacts of ER quality control systems on antifungal resistance and virulence.
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Affiliation(s)
- Taiga Miyazaki
- Department of Molecular Microbiology and Immunology; Nagasaki University School of Medicine; Nagasaki, Japan; Department of Respiratory Medicine; Sasebo City General Hospital; Nagasaki, Japan
| | - Shigeru Kohno
- Department of Molecular Microbiology and Immunology; Nagasaki University School of Medicine; Nagasaki, Japan
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66
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Moore MM. The crucial role of iron uptake in Aspergillus fumigatus virulence. Curr Opin Microbiol 2013; 16:692-9. [DOI: 10.1016/j.mib.2013.07.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 07/16/2013] [Accepted: 07/16/2013] [Indexed: 02/01/2023]
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Glazier VE, Panepinto JC. The ER stress response and host temperature adaptation in the human fungal pathogen Cryptococcus neoformans. Virulence 2013; 5:351-6. [PMID: 24253500 PMCID: PMC3956513 DOI: 10.4161/viru.27187] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
In all eukaryotic cells, the ER stress response is pivotal to survival and adaptation under stress conditions. During temperature adaptation in the human fungal pathogen Cryptococcus neoformans, ER stress is engaged transiently. Studies of this response have demonstrated that both the engagement (turning on the response), as well as the resolution (turning off the response) are required for temperature adaptation and, therefore, pathogenesis. In this review, we synthesize our current understanding of ER stress response engagement and resolution in C. neoformans during host temperature adaptation with a focus on the posttranscriptional events that regulate it. Identification of fungal-specific and Cryptococcus-specific elements of the evolutionarily conserved ER stress response pathway could lead to identification of anti-fungal targets in this fundamental stress response.
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Affiliation(s)
- Virginia E Glazier
- Department of Microbiology and Immunology; Witebsky Center for Microbial Pathogenesis and Immunology; University at Buffalo; The State University of New York; Buffalo, NY USA
| | - John C Panepinto
- Department of Microbiology and Immunology; Witebsky Center for Microbial Pathogenesis and Immunology; University at Buffalo; The State University of New York; Buffalo, NY USA
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68
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Are we there yet? Recent progress in the molecular diagnosis and novel antifungal targeting of Aspergillus fumigatus and invasive aspergillosis. PLoS Pathog 2013; 9:e1003642. [PMID: 24204250 PMCID: PMC3812002 DOI: 10.1371/journal.ppat.1003642] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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69
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Cheon SA, Jung KW, Bahn YS, Kang HA. The unfolded protein response (UPR) pathway in Cryptococcus. Virulence 2013; 5:341-50. [PMID: 24504058 DOI: 10.4161/viru.26774] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Unique and evolutionarily conserved signaling pathways allow an organism to sense, respond to, and adapt to internal and external environmental cues at its biological niche. In eukaryotic cells, the unfolded protein response (UPR) pathway regulates endoplasmic reticulum (ER) homeostasis upon exposure to environmental changes causing ER stress. The UPR pathway of Cryptococcus neoformans, an opportunistic fungal pathogen, which causes life-threatening meningoencephalitis in immunocompromised individuals, consists of the evolutionarily conserved Ire1 kinase, a unique bZIP transcription factor, Hxl1, and the ER-resident molecular chaperone Kar2/BiP. Although the Cryptococcus UPR pathway regulates ER stress, antifungal drug resistance, and virulence in an Ire1/Hxl1-dependent manner, Ire1 has Hxl1-independent roles in capsule biosynthesis and thermotolerance. In this review, we highlight the conserved and unique features of the Cryptococcus UPR pathway compared with other fungal UPR systems and its importance in the pathogenesis of cryptococcosis and discuss future challenges in this field.
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Affiliation(s)
- Seon Ah Cheon
- Department of Life Science; Research Center for Biomolecules and Biosystems; College of Natural Science; Chung-Ang University; Seoul, Korea; Department of Agricultural Biotechnology and Center for Fungal Pathogenesis; Seoul National University; Seoul, Korea
| | - Kwang-Woo Jung
- Department of Biotechnology; Center for Fungal Pathogenesis; Yonsei University; Seoul, Korea
| | - Yong-Sun Bahn
- Department of Biotechnology; Center for Fungal Pathogenesis; Yonsei University; Seoul, Korea
| | - Hyun Ah Kang
- Department of Life Science; Research Center for Biomolecules and Biosystems; College of Natural Science; Chung-Ang University; Seoul, Korea
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70
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Krishnan K, Askew DS. The fungal UPR: a regulatory hub for virulence traits in the mold pathogen Aspergillus fumigatus. Virulence 2013; 5:334-40. [PMID: 24189125 PMCID: PMC3956511 DOI: 10.4161/viru.26571] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Aspergillus fumigatus is an opportunistic pathogen that is responsible for a life-threatening fungal infection known as invasive aspergillosis. Current therapies for the treatment of this disease continue to be associated with a poor outcome, so there is a need for more information about aspects of the fungus-host interaction that could offer novel targets for drug intervention. One attractive possibility is the unfolded protein response (UPR), an intracellular signaling network that helps the fungus meet the demand for secretion in the host environment. The major function of the UPR is to mitigate ER stress by maintaining an equilibrium between the load of client proteins entering the endoplasmic reticulum (ER) and the protein folding capacity of the organelle. However, recent findings suggest that A. fumigatus, as well as several other pathogenic fungi, also rely upon this pathway for virulence. In this review, we provide an update on the A. fumigatus UPR, discuss emerging evidence that the UPR is situated at the nexus of a number of physiological functions that are vital for the virulence of this fungus, and suggest exciting possibilities for future therapeutic targeting of this pathway for the treatment of aspergillosis.
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Affiliation(s)
- Karthik Krishnan
- Department of Pathology & Laboratory Medicine; University of Cincinnati College of Medicine; Cincinnati, OH USA
| | - David S Askew
- Department of Pathology & Laboratory Medicine; University of Cincinnati College of Medicine; Cincinnati, OH USA
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71
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Heimel K, Freitag J, Hampel M, Ast J, Bölker M, Kämper J. Crosstalk between the unfolded protein response and pathways that regulate pathogenic development in Ustilago maydis. THE PLANT CELL 2013; 25:4262-77. [PMID: 24179126 PMCID: PMC3877826 DOI: 10.1105/tpc.113.115899] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The unfolded protein response (UPR) is a conserved eukaryotic signaling pathway regulating endoplasmic reticulum (ER) homeostasis during ER stress, which results, for example, from an increased demand for protein secretion. Here, we characterize the homologs of the central UPR regulatory proteins Hac1 (for Homologous to ATF/CREB1) and Inositol Requiring Enzyme1 in the plant pathogenic fungus Ustilago maydis and demonstrate that the UPR is tightly interlinked with the b mating-type-dependent signaling pathway that regulates pathogenic development. Exact timing of UPR is required for virulence, since premature activation interferes with the b-dependent switch from budding to filamentous growth. In addition, we found crosstalk between UPR and the b target Clampless1 (Clp1), which is essential for cell cycle release and proliferation in planta. The unusual C-terminal extension of the U. maydis Hac1 homolog, Cib1 (for Clp1 interacting bZIP1), mediates direct interaction with Clp1. The interaction between Clp1 and Cib1 promotes stabilization of Clp1, resulting in enhanced ER stress tolerance that prevents deleterious UPR hyperactivation. Thus, the interaction between Cib1 and Clp1 constitutes a checkpoint to time developmental progression and increased secretion of effector proteins at the onset of biotrophic development. Crosstalk between UPR and the b mating-type regulated developmental program adapts ER homeostasis to the changing demands during biotrophy.
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Affiliation(s)
- Kai Heimel
- Georg-August-University Göttingen, Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, 37077 Goettingen, Germany
- Karlsruhe Institute of Technology, Institute for Applied Bioscience, Department of Genetics, 76187 Karlsruhe, Germany
| | - Johannes Freitag
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO), 35032 Marburg, Germany
| | - Martin Hampel
- Georg-August-University Göttingen, Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, 37077 Goettingen, Germany
| | - Julia Ast
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
| | - Michael Bölker
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO), 35032 Marburg, Germany
- Address correspondence to
| | - Jörg Kämper
- Karlsruhe Institute of Technology, Institute for Applied Bioscience, Department of Genetics, 76187 Karlsruhe, Germany
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72
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Stress signaling pathways for the pathogenicity of Cryptococcus. EUKARYOTIC CELL 2013; 12:1564-77. [PMID: 24078305 DOI: 10.1128/ec.00218-13] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Sensing, responding, and adapting to the surrounding environment are crucial for all living organisms to survive, proliferate, and differentiate in their biological niches. This ability is also essential for Cryptococcus neoformans and its sibling species Cryptococcus gattii, as these pathogens have saprobic and parasitic life cycles in natural and animal host environments. The ability of Cryptococcus to cause fatal meningoencephalitis is highly related to its capability to remodel and optimize its metabolic and physiological status according to external cues. These cues act through multiple stress signaling pathways through a panoply of signaling components, including receptors/sensors, small GTPases, secondary messengers, kinases, transcription factors, and other miscellaneous adaptors or regulators. In this minireview, we summarize and highlight the importance of several stress signaling pathways that influence the pathogenicity of Cryptococcus and discuss future challenges in these areas.
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73
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The immune interplay between the host and the pathogen in Aspergillus fumigatus lung infection. BIOMED RESEARCH INTERNATIONAL 2013; 2013:693023. [PMID: 23984400 PMCID: PMC3745895 DOI: 10.1155/2013/693023] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 06/14/2013] [Indexed: 12/22/2022]
Abstract
The interplay between Aspergillus fumigatus and the host immune response in lung infection has been subject of studies over the last years due to its importance in immunocompromised patients. The multifactorial virulence factors of A. fumigatus are related to the fungus biological characteristics, for example, structure, ability to grow and adapt to high temperatures and stress conditions, besides capability of evading the immune system and causing damage to the host. In this context, the fungus recognition by the host innate immunity occurs when the pathogen disrupts the natural and chemical barriers followed by the activation of acquired immunity. It seems clear that a Th1 response has a protective role, whereas Th2 reactions are often associated with higher fungal burden, and Th17 response is still controversial. Furthermore, a fine regulation of the effector immunity is required to avoid excessive tissue damage associated with fungal clearance, and this role could be attributed to regulatory T cells. Finally, in this work we reviewed the aspects involved in the complex interplay between the host immune response and the pathogen virulence factors, highlighting the immunological issues and the importance of its better understanding to the development of novel therapeutic approaches for invasive lung aspergillosis.
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74
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Abstract
The response of eukaryotic microbes to low-oxygen (hypoxic) conditions is strongly regulated at the level of transcription. Comparative analysis shows that some of the transcriptional regulators (such as the sterol regulatory element-binding proteins, or SREBPs) are of ancient origin and probably regulate sterol synthesis in most eukaryotic microbes. However, in some fungi SREBPs have been replaced by a zinc-finger transcription factor (Upc2). Nuclear localization of fungal SREBPs is determined by regulated proteolysis, either by site-specific proteases or by an E3 ligase complex and the proteasome. The exact mechanisms of oxygen sensing are not fully characterized but involve responding to low levels of heme and/or sterols and possibly to levels of nitric oxide and reactive oxygen species. Changes in central carbon metabolism (glycolysis and respiration) are a core hypoxic response in some, but not all, fungal species. Adaptation to hypoxia is an important virulence characteristic of pathogenic fungi.
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Affiliation(s)
- Geraldine Butler
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland;
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75
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Powers-Fletcher MV, Feng X, Krishnan K, Askew DS. Deletion of the sec4 homolog srgA from Aspergillus fumigatus is associated with an impaired stress response, attenuated virulence and phenotypic heterogeneity. PLoS One 2013; 8:e66741. [PMID: 23785510 PMCID: PMC3681910 DOI: 10.1371/journal.pone.0066741] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/10/2013] [Indexed: 01/04/2023] Open
Abstract
Small GTPases of the Rab family are master regulators of membrane trafficking, responsible for coordinating the sorting, packaging and delivery of membrane-bound vesicles to specific sites within eukaryotic cells. The contribution of these proteins to the biology of the human pathogenic fungus Aspergillus fumigatus has not been explored. In this study, we characterized the srgA gene, encoding a Rab GTPase closely related to Sec4. We found that a GFP-SrgA fusion protein accumulated preferentially at hyphal tips and mature condiophores. The radial growth of a ΔsrgA mutant was impaired on both rich and minimal medium, consistent with a role for SrgA in filamentous growth. In addition, the ΔsrgA mutant revealed dysmorphic conidiophores that produced conidia with heterogeneous morphology. The ΔsrgA mutant was hypersensitive to brefeldin A-mediated inhibition of vesicular trafficking and showed increased temperature sensitivity relative to wild type A. fumigatus. However, the most striking phenotype of this mutant was its phenotypic heterogeneity. Individual colonies isolated from the original ΔsrgA mutant showed variable morphology with colony sectoring. In addition, each isolate of the ΔsrgA mutant displayed divergent phenotypes with respect to thermotolerance, in vitro stress response and virulence in a Galleria mellonella infection model. Taken together, these results indicate that SrgA contributes to the asexual development and filamentous growth of A. fumigatus. However, the discordant phenotypes observed among individual isolates of the ΔsrgA mutant suggest that the absence of srgA exerts selective pressure for the acquisition of compensatory changes, such as second-site suppressor mutations.
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Affiliation(s)
- Margaret V. Powers-Fletcher
- 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
| | - Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, 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:
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77
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Abstract
The filamentous fungi are an ecologically important group of organisms which also have important industrial applications but devastating effects as pathogens and agents of food spoilage. Protein kinases have been implicated in the regulation of virtually all biological processes but how they regulate filamentous fungal specific processes is not understood. The filamentous fungus Aspergillus nidulans has long been utilized as a powerful molecular genetic system and recent technical advances have made systematic approaches to study large gene sets possible. To enhance A. nidulans functional genomics we have created gene deletion constructs for 9851 genes representing 93.3% of the encoding genome. To illustrate the utility of these constructs, and advance the understanding of fungal kinases, we have systematically generated deletion strains for 128 A. nidulans kinases including expanded groups of 15 histidine kinases, 7 SRPK (serine-arginine protein kinases) kinases and an interesting group of 11 filamentous fungal specific kinases. We defined the terminal phenotype of 23 of the 25 essential kinases by heterokaryon rescue and identified phenotypes for 43 of the 103 non-essential kinases. Uncovered phenotypes ranged from almost no growth for a small number of essential kinases implicated in processes such as ribosomal biosynthesis, to conditional defects in response to cellular stresses. The data provide experimental evidence that previously uncharacterized kinases function in the septation initiation network, the cell wall integrity and the morphogenesis Orb6 kinase signaling pathways, as well as in pathways regulating vesicular trafficking, sexual development and secondary metabolism. Finally, we identify ChkC as a third effector kinase functioning in the cellular response to genotoxic stress. The identification of many previously unknown functions for kinases through the functional analysis of the A. nidulans kinome illustrates the utility of the A. nidulans gene deletion constructs.
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78
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Essential roles of the Kar2/BiP molecular chaperone downstream of the UPR pathway in Cryptococcus neoformans. PLoS One 2013; 8:e58956. [PMID: 23484059 PMCID: PMC3590199 DOI: 10.1371/journal.pone.0058956] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 02/08/2013] [Indexed: 11/19/2022] Open
Abstract
The endoplasmic reticulum (ER) is a central hub where secreted or membrane-bound proteins are maturated and folded properly in eukaryotes. Maintenance of ER homeostasis is particularly important for human fungal pathogens, such as Cryptococcus neoformans, which encounter a plethora of host-mediated stresses during infection. Our previous study demonstrated that the unfolded protein response (UPR) pathway, composed of the evolutionarily conserved Ire1 kinase and the unique Hxl1 transcription factor, has pleiotropic roles in ER stress response, thermotolerance, antifungal drug resistance, and virulence in C. neoformans. Here, we functionally characterized an ER-resident molecular chaperone, Kar2/BiP, in C. neoformans. Conditional expression of KAR2 by the copper-regulated promoter revealed that Kar2 is essential for the viability of C. neoformans. Constitutive expression of KAR2 by the strong histone H3 promoter partially restores resistance to ER stress, cell wall stress, thermotolerance, and genotoxic stress in ire1Δ and hxl1Δ mutants, suggesting that Kar2 mainly functions downstream of the UPR pathway. Furthermore, Kar2 appears to control azole resistance in C. neoformans downstream of the UPR pathway without regulation of ERG11 or ERG3. Interestingly, we discovered that azole treatment is sensed as ER-stress and subsequently activates the Ire1-dependent Hxl1 splicing event and induction of KAR2 by the UPR pathway. In contrast, the constitutive expression of Kar2 is not sufficient to restore the Ire1-mediated regulation of capsule production in C. neoformans UPR mutants. In conclusion, this study demonstrates that Kar2 is not only essential for vegetative growth but also required for response and adaptation to the environmental stresses and antifungal drugs downstream of the UPR pathway in C. neoformans.
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79
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Li Y, Liu H, Huang YY, Pu LJ, Zhang XD, Jiang CC, Jiang ZW. Suppression of endoplasmic reticulum stress-induced invasion and migration of breast cancer cells through the downregulation of heparanase. Int J Mol Med 2013; 31:1234-42. [PMID: 23467544 DOI: 10.3892/ijmm.2013.1292] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 02/11/2013] [Indexed: 11/05/2022] Open
Abstract
Tumor metastasis is the ultimate stage of cancer, and the primary cause of mortality in patients. Tumor cells breaking through the natural barrier consisting of the basement membrane (BM) and extracellular matrix (ECM) is the a crucial step in tumor invasion and metastasis. Thus, protecting this barrier is the key to reducing mortality. Heparanase is a mammalian endo-β-glucuronidase which has been found to promote the cleavage of heparan sulfate (HS), and plays a significant role in tumor cell invasion and metastasis. Although chemotherapeutic reagents have a strong antitumor activity, they may promote the invasion and migration of cancer cells, as has been observed during clinical treatment. Chemotherapeutic reagents can induce endoplasmic reticulum (ER) stress; in this study, we used adriamycin (ADM) and a classical ER stress inducer, tunicamycin (TM). We report that the activation of ER stress is involved in the enhanced invasion and migration ability of breast cancer cells and we hypothesized that this effect is associated with the activation of heparanase. In support of this, we used the heparanase inhibitor, OGT2115, and low molecular weight heparin (LMWH) to inhibit the expression and activity of heparanase, and we found that the invasion and migration ability of the cells was suppressed. Our findings demonstrate that heparanase inhibitors suppress breast cancer cell invasion and migration induced by ER stress, and provide a strong rationale for the development of heparanase-based therapeutics for the prevention of metastasis induced by chemotherapeutic reagents.
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Affiliation(s)
- Yang Li
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233000, P.R. China
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80
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Effects of a defective endoplasmic reticulum-associated degradation pathway on the stress response, virulence, and antifungal drug susceptibility of the mold pathogen Aspergillus fumigatus. EUKARYOTIC CELL 2013; 12:512-9. [PMID: 23355008 DOI: 10.1128/ec.00319-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Proteins that are destined for release outside the eukaryotic cell, insertion into the plasma membrane, or delivery to intracellular organelles are processed and folded in the endoplasmic reticulum (ER). An imbalance between the level of nascent proteins entering the ER and the organelle's ability to manage that load results in the accumulation of unfolded proteins. Terminally unfolded proteins are disposed of by ER-associated degradation (ERAD), a pathway that transports the aberrant proteins across the ER membrane into the cytosol for proteasomal degradation. The ERAD pathway was targeted in the mold pathogen Aspergillus fumigatus by deleting the hrdA gene, encoding the A. fumigatus ortholog of Hrd1, the E3 ubiquitin ligase previously shown to contribute to ERAD in other species. Loss of HrdA was associated with impaired degradation of a folding-defective ERAD substrate, CPY*, as well as activation of the unfolded-protein response (UPR). The ΔhrdA mutant showed resistance to voriconazole and reduced thermotolerance but was otherwise unaffected by a variety of environmental stressors. A double-deletion mutant deficient in both HrdA and another component of the same ERAD complex, DerA, was defective in secretion and showed hypersensitivity to ER, thermal, and cell wall stress. However, the ΔhrdA ΔderA mutant remained virulent in mouse and insect infection models. These data demonstrate that HrdA and DerA support complementary ERAD functions that promote survival under conditions of ER stress but are dispensable for virulence in the host environment.
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81
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Miyazaki T, Nakayama H, Nagayoshi Y, Kakeya H, Kohno S. Dissection of Ire1 functions reveals stress response mechanisms uniquely evolved in Candida glabrata. PLoS Pathog 2013; 9:e1003160. [PMID: 23382685 PMCID: PMC3561209 DOI: 10.1371/journal.ppat.1003160] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 12/12/2012] [Indexed: 11/18/2022] Open
Abstract
Proper protein folding in the endoplasmic reticulum (ER) is vital in all eukaryotes. When misfolded proteins accumulate in the ER lumen, the transmembrane kinase/endoribonuclease Ire1 initiates splicing of HAC1 mRNA to generate the bZIP transcription factor Hac1, which subsequently activates its target genes to increase the protein-folding capacity of the ER. This cellular machinery, called the unfolded protein response (UPR), is believed to be an evolutionarily conserved mechanism in eukaryotes. In this study, we comprehensively characterized mutant phenotypes of IRE1 and other related genes in the human fungal pathogen Candida glabrata. Unexpectedly, Ire1 was required for the ER stress response independently of Hac1 in this fungus. C. glabrata Ire1 did not cleave mRNAs encoding Hac1 and other bZIP transcription factors identified in the C. glabrata genome. Microarray analysis revealed that the transcriptional response to ER stress is not mediated by Ire1, but instead is dependent largely on calcineurin signaling and partially on the Slt2 MAPK pathway. The loss of Ire1 alone did not confer increased antifungal susceptibility in C. glabrata contrary to UPR-defective mutants in other fungi. Taken together, our results suggest that the canonical Ire1-Hac1 UPR is not conserved in C. glabrata. It is known in metazoans that active Ire1 nonspecifically cleaves and degrades a subset of ER-localized mRNAs to reduce the ER load. Intriguingly, this cellular response could occur in an Ire1 nuclease-dependent fashion in C. glabrata. We also uncovered the attenuated virulence of the C. glabrata Δire1 mutant in a mouse model of disseminated candidiasis. This study has unveiled the unique evolution of ER stress response mechanisms in C. glabrata.
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Affiliation(s)
- Taiga Miyazaki
- Department of Molecular Microbiology and Immunology, Nagasaki University School of Medicine, Nagasaki, Japan.
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82
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Abstract
Over the last 3 decades, the frequency of life-threatening human fungal infections has increased as advances in medical therapies, solid-organ and hematopoietic stem cell transplantations, an increasing geriatric population, and HIV infections have resulted in significant rises in susceptible patient populations. Although significant advances have been made in understanding how fungi cause disease, the dynamic microenvironments encountered by fungi during infection and the mechanisms by which they adapt to these microenvironments are not fully understood. As inhibiting and preventing in vivo fungal growth are main goals of antifungal therapies, understanding in vivo fungal metabolism in these host microenvironments is critical for the improvement of existing therapies or the design of new approaches. In this minireview, we focus on the emerging appreciation that pathogenic fungi like Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus are exposed to oxygen-limited or hypoxic microenvironments during fungal pathogenesis. The implications of these in vivo hypoxic microenvironments for fungal metabolism and pathogenesis are discussed with an aim toward understanding the potential impact of hypoxia on invasive fungal infection outcomes.
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83
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Molecular characterization of the putative transcription factor SebA involved in virulence in Aspergillus fumigatus. EUKARYOTIC CELL 2012; 11:518-31. [PMID: 22345349 DOI: 10.1128/ec.00016-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Nutrient sensing and acquisition mechanisms, as well as the capability to cope with different stressing conditions, are essential for A. fumigatus virulence and survival in the mammalian host. This study characterized the A. fumigatus SebA transcription factor, which is the putative homologue of the factor encoded by Trichoderma atroviride seb1. The ΔsebA mutant demonstrated reduced growth in the presence of paraquat, hydrogen peroxide, CaCl2, and poor nutritional conditions, while viability associated with sebA was also affected by heat shock exposure. Accordingly, SebA::GFP (SebA::green fluorescent protein) was shown to accumulate in the nucleus upon exposure to oxidative stress and heat shock conditions. In addition, genes involved in either the oxidative stress or heat shock response had reduced transcription in the ΔsebA mutant. The A. fumigatus ΔsebA strain was attenuated in virulence in a murine model of invasive pulmonary aspergillosis. Furthermore, killing of the ΔsebA mutant by murine alveolar macrophages was increased compared to killing of the wild-type strain. A. fumigatus SebA plays a complex role, contributing to several stress tolerance pathways and growth under poor nutritional conditions, and seems to be integrated into different stress responses.
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84
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Moreno AA, Mukhtar MS, Blanco F, Boatwright JL, Moreno I, Jordan MR, Chen Y, Brandizzi F, Dong X, Orellana A, Pajerowska-Mukhtar KM. IRE1/bZIP60-mediated unfolded protein response plays distinct roles in plant immunity and abiotic stress responses. PLoS One 2012; 7:e31944. [PMID: 22359644 PMCID: PMC3281089 DOI: 10.1371/journal.pone.0031944] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 01/16/2012] [Indexed: 11/18/2022] Open
Abstract
Endoplasmic reticulum (ER)-mediated protein secretion and quality control have been shown to play an important role in immune responses in both animals and plants. In mammals, the ER membrane-located IRE1 kinase/endoribonuclease, a key regulator of unfolded protein response (UPR), is required for plasma cell development to accommodate massive secretion of immunoglobulins. Plant cells can secrete the so-called pathogenesis-related (PR) proteins with antimicrobial activities upon pathogen challenge. However, whether IRE1 plays any role in plant immunity is not known. Arabidopsis thaliana has two copies of IRE1, IRE1a and IRE1b. Here, we show that both IRE1a and IRE1b are transcriptionally induced during chemically-induced ER stress, bacterial pathogen infection and treatment with the immune signal salicylic acid (SA). However, we found that IRE1a plays a predominant role in the secretion of PR proteins upon SA treatment. Consequently, the ire1a mutant plants show enhanced susceptibility to a bacterial pathogen and are deficient in establishing systemic acquired resistance (SAR), whereas ire1b is unaffected in these responses. We further demonstrate that the immune deficiency in ire1a is due to a defect in SA- and pathogen-triggered, IRE1-mediated cytoplasmic splicing of the bZIP60 mRNA, which encodes a transcription factor involved in the expression of UPR-responsive genes. Consistently, IRE1a is preferentially required for bZIP60 splicing upon pathogen infection, while IRE1b plays a major role in bZIP60 processing upon Tunicamycin (Tm)-induced stress. We also show that SA-dependent induction of UPR-responsive genes is altered in the bzip60 mutant resulting in a moderate susceptibility to a bacterial pathogen. These results indicate that the IRE1/bZIP60 branch of UPR is a part of the plant response to pathogens for which the two Arabidopsis IRE1 isoforms play only partially overlapping roles and that IRE1 has both bZIP60-dependent and bZIP60-independent functions in plant immunity.
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Affiliation(s)
- Adrian A. Moreno
- FONDAP Center for Genome Regulation, Núcleo Milenio en Biotecnología Celular Vegetal, Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile
| | - M. Shahid Mukhtar
- Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Francisca Blanco
- FONDAP Center for Genome Regulation, Núcleo Milenio en Biotecnología Celular Vegetal, Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile
| | - Jon Lucas Boatwright
- Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Ignacio Moreno
- FONDAP Center for Genome Regulation, Núcleo Milenio en Biotecnología Celular Vegetal, Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile
| | - Melissa R. Jordan
- Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Yani Chen
- Michigan State University–DOE Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Federica Brandizzi
- Michigan State University–DOE Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Xinnian Dong
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| | - Ariel Orellana
- FONDAP Center for Genome Regulation, Núcleo Milenio en Biotecnología Celular Vegetal, Centro de Biotecnología Vegetal, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile
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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.
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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:
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