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Montanari Borges B, Gama de Santana M, Willian Preite N, de Lima Kaminski V, Trentin G, Almeida F, Vieira Loures F. Extracellular vesicles from virulent P. brasiliensis induce TLR4 and dectin-1 expression in innate cells and promote enhanced Th1/Th17 response. Virulence 2024; 15:2329573. [PMID: 38511558 PMCID: PMC10962619 DOI: 10.1080/21505594.2024.2329573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 03/07/2024] [Indexed: 03/22/2024] Open
Abstract
Extracellular vesicles (EVs) are membrane-enclosed nanoparticles that transport several biomolecules and are involved in important mechanisms and functions related to the pathophysiology of fungal diseases. EVs from Paracoccidioides brasiliensis, the main causative agent of Paracoccidioidomycosis (PCM), modulate the immune response of macrophages. In this study, we assessed the EVs proteome from a virulent P. brasiliensis isolated from granulomatous lesions and compared their immunomodulatory ability with EVs isolated from the fungus before the animal passage (control EVs) when challenging macrophages and dendritic cells (DCs). Proteome showed that virulent EVs have a higher abundance of virulence factors such as GP43, protein 14-3-3, GAPDH, as well as virulence factors never described in PCM, such as aspartyl aminopeptidase and a SidJ analogue compared with control EVs. Virulent extracellular vesicles induced higher expression of TLR4 and Dectin-1 than control EVs in macrophages and dendritic cells (DCs). In opposition, a lower TLR2 expression was induced by virulent EVs. Additionally, virulent EVs induced lower expression of CD80, CD86 and TNF-α, but promoted a higher expression of IL-6 and IL-10, suggesting that EVs isolated from virulent P. brasiliensis-yeast promote a milder DCs and macrophage maturation. Herein, we showed that EVs from virulent fungi stimulated a higher frequency of Th1/Tc1, Th17, and Treg cells, which gives new insights into fungal extracellular vesicles. Taken together, our results suggest that P. brasiliensis utilizes its EVs as virulence bags that manipulate the immune system in its favour, creating a milder immune response and helping with fungal evasion from the immune system.
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Affiliation(s)
- Bruno Montanari Borges
- Institute of Science and Technology (ICT), Federal University of São Paulo (UNIFESP), São José dos Campos, São Paulo, Brazil
| | - Monique Gama de Santana
- Institute of Science and Technology (ICT), Federal University of São Paulo (UNIFESP), São José dos Campos, São Paulo, Brazil
| | - Nycolas Willian Preite
- Institute of Science and Technology (ICT), Federal University of São Paulo (UNIFESP), São José dos Campos, São Paulo, Brazil
| | - Valéria de Lima Kaminski
- Institute of Science and Technology (ICT), Federal University of São Paulo (UNIFESP), São José dos Campos, São Paulo, Brazil
| | - Gabriel Trentin
- Department of Biochemistry and Immunology, Ribeirao Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Fausto Almeida
- Department of Biochemistry and Immunology, Ribeirao Preto Medical School, University of São Paulo, São Paulo, Brazil
| | - Flávio Vieira Loures
- Institute of Science and Technology (ICT), Federal University of São Paulo (UNIFESP), São José dos Campos, São Paulo, Brazil
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Li Y, Chadwick B, Pham T, Xie X, Lin X. Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans. mBio 2024; 15:e0092024. [PMID: 38742885 PMCID: PMC11237595 DOI: 10.1128/mbio.00920-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 04/09/2024] [Indexed: 05/16/2024] Open
Abstract
Cryptococcus neoformans causes cryptococcal meningoencephalitis, a disease that kills more than 180,000 people annually. Contributing to its success as a fungal pathogen is its cell wall surrounded by a capsule. When the cryptococcal cell wall is compromised, exposed pathogen-associated molecular pattern molecules (PAMPs) could trigger host recognition and initiate attack against this fungus. Thus, cell wall composition and structure are tightly regulated. The cryptococcal cell wall is unusual in that chitosan, the acetylated form of chitin, is predominant over chitin and is essential for virulence. Recently, it was shown that acidic pH weakens the cell wall and increases exposure of PAMPs partly due to decreased chitosan levels. However, the molecular mechanism responsible for the cell wall remodeling in acidic pH is unknown. In this study, by screening for genes involved in cryptococcal tolerance to high levels of CO2, we serendipitously discovered that the aspartyl peptidase May1 contributes to cryptococcal sensitivity to high levels of CO2 due to acidification of unbuffered media. Overexpression of MAY1 increases the cryptococcal cell size and elevates PAMP exposure, causing a hyper-inflammatory response in the host while MAY1 deletion does the opposite. We discovered that May1 weakens the cell wall and reduces the chitosan level, partly due to its involvement in the degradation of Chs3, the sole chitin synthase that supplies chitin to be converted to chitosan. Consistently, overexpression of CHS3 largely rescues the phenotype of MAY1oe in acidic media. Collectively, we demonstrate that May1 remodels the cryptococcal cell wall in acidic pH by reducing chitosan levels through its influence on Chs3. IMPORTANCE The fungal cell wall is a dynamic structure, monitoring and responding to internal and external stimuli. It provides a formidable armor to the fungus. However, in a weakened state, the cell wall also triggers host immune attack when PAMPs, including glucan, chitin, and mannoproteins, are exposed. In this work, we found that the aspartyl peptidase May1 impairs the cell wall of Cryptococcus neoformans and increases the exposure of PAMPs in the acidic environment by reducing the chitosan level. Under acidic conditions, May1 is involved in the degradation of the chitin synthase Chs3, which supplies chitin to be deacetylated to chitosan. Consistently, the severe deficiency of chitosan in acidic pH can be rescued by overexpressing CHS3. These findings improve our understanding of cell wall remodeling and reveal a potential target to compromise the cell wall integrity in this important fungal pathogen.
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Affiliation(s)
- Yeqi Li
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Benjamin Chadwick
- Department of Plant Biology, University of Georgia, Athens, Georgia, USA
| | - Tuyetnhu Pham
- Department of Plant Biology, University of Georgia, Athens, Georgia, USA
| | - Xiaofeng Xie
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Xiaorong Lin
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
- Department of Plant Biology, University of Georgia, Athens, Georgia, USA
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The Entomopathogenic Fungus Beauveria bassiana Employs Autophagy as a Persistence and Recovery Mechanism during Conidial Dormancy. mBio 2023; 14:e0304922. [PMID: 36809079 PMCID: PMC10128008 DOI: 10.1128/mbio.03049-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Many filamentous fungi develop a conidiation process as an essential mechanism for their dispersal and survival in natural ecosystems. However, the mechanisms underlying conidial persistence in environments are still not fully understood. Here, we report that autophagy is crucial for conidial lifespans (i.e., viability) and vitality (e.g., stress responses and virulence) in the filamentous mycopathogen Beauveria bassiana. Specifically, Atg11-mediated selective autophagy played an important, but not dominant, role in the total autophagic flux. Furthermore, the aspartyl aminopeptidase Ape4 was found to be involved in conidial vitality during dormancy. Notably, the vacuolar translocation of Ape4 was dependent on its physical interaction with autophagy-related protein 8 (Atg8) and associated with the autophagic role of Atg8, as determined through a truncation assay of a critical carboxyl-tripeptide. These observations revealed that autophagy acted as a subcellular mechanism for conidial recovery during dormancy in environments. In addition, a novel Atg8-dependent targeting route for vacuolar hydrolase was identified, which is essential for conidial exit from a long-term dormancy. These new insights improved our understanding of the roles of autophagy in the physiological ecology of filamentous fungi as well as the molecular mechanisms involved in selective autophagy. IMPORTANCE Conidial environmental persistence is essential for fungal dispersal in ecosystems while also serving as a determinant for the biocontrol efficacy of entomopathogenic fungi during integrated pest management. This study identified autophagy as a mechanism to safeguard conidial lifespans and vitality postmaturation. In this mechanism, the aspartyl aminopeptidase Ape4 translocates into vacuoles via its physical interaction with autophagy-related protein 8 (Atg8) and is involved in conidial vitality during survival. The study revealed that autophagy acted as a subcellular mechanism for maintaining conidial persistence during dormancy, while also documenting an Atg8-dependent targeting route for vacuolar hydrolase during conidial recovery from dormancy. Thus, these observations provided new insight into the roles of autophagy in the physiological ecology of filamentous fungi and documented novel molecular mechanisms involved in selective autophagy.
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Predominance of Cryptococcus neoformans Var. grubii in Ahvaz, Molecular Identification and Evaluation of Virulence Factors. Jundishapur J Microbiol 2021. [DOI: 10.5812/jjm.112408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Background: Cryptococcus neoformans is an encapsulated yeast pathogen with worldwide distribution, and the highest incidence of cryptococcosis was attributed to C. neoformans (var. grubii. The pathogenicity of Cryptococcus species is associated with several factors, including capsule and melanin production, growth at 37 ºC, and secretion of extracellular enzymes. Objectives: The present study aimed to isolate and identify Cryptococcus species from pigeon guano in Ahvaz, Iran and investigate important virulence factors in the isolates. Methods: Seventy-three isolates of C. neoformans var. grubii were identified based on classical and molecular microbiology methods. Capsule size was measured by the grow yeasts in the presence of 5% CO2. Specific media demonstrated the activity of extracellular enzymes (phospholipase, hemolysin, proteinase, esterase, urease, catalase, and gelatinase). Besides, melanin production was evaluated by the niger seed agar medium. Results: Two hundred and seventeen samples were examined for the presence of Cryptococcus over 165 days in Ahvaz. All tested isolates were contained capsules with variable sizes under 5% CO2 concentration. Moreover, 100% of isolates were produced extracellular enzymes (urease, hemolysin, and catalase), whereas no proteinase and gelatinase activities were observed among isolates. Furthermore, most isolates had phospholipase (93.1%) and esterase activities (86.3%). Also, melanin was produced by all of the isolates. Conclusions: Although two methods were used for recovery of Cryptococcus, only Cryptococcus was isolated from pigeon guano, and swabs from the cage walls were negative. Cryptococcus neoformans var. grubii was the only species from pigeon droppings from Ahvaz with more pathogenic factors. Owing to the high pathogenicity of the isolates, the frequency of the disease is expected to be higher.
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Jiang ST, Chang AN, Han LT, Guo JS, Li YH, Liu TB. Autophagy Regulates Fungal Virulence and Sexual Reproduction in Cryptococcus neoformans. Front Cell Dev Biol 2020; 8:374. [PMID: 32528953 PMCID: PMC7262457 DOI: 10.3389/fcell.2020.00374] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/27/2020] [Indexed: 01/12/2023] Open
Abstract
Autophagy (macroautophagy) is an evolutionarily conserved degradation pathway involved in bulk degradation of cytoplasmic organelles, old protein, and other macromolecules and nutrient recycling during starvation. Extensive studies on functions of autophagy-related genes have revealed that autophagy plays a role in cell differentiation and pathogenesis of pathogenic fungi. In this study, we identified and characterized 14 core autophagy machinery genes (ATGs) in C. neoformans. To understand the function of autophagy in virulence and fungal development in C. neoformans, we knocked out the 14 ATGs in both α and a mating type strain backgrounds in C. neoformans, respectively, by using biolistic transformation and in vivo homologous recombination. Fungal virulence assay showed that virulence of each atgΔ mutants was attenuated in a murine inhalation systemic-infection model, although virulence factor production was not dramatically impaired in vitro. Fungal mating assays showed that all the 14 ATGs are essential for fungal sexual reproduction as basidiospore production was blocked in bilateral mating between each atgΔ mutants. Fungal nuclei development assay showed that nuclei in the bilateral mating of each atgΔ mutants failed to undergo meiosis after fusion, indicating autophagy is essential for regulating meiosis during mating. Overall, our study showed that autophagy is essential for fungal virulence and sexual reproduction in C. neoformans, which likely represents a conserved novel virulence and sexual reproduction control mechanism that involves the autophagy-mediated proteolysis pathway.
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Affiliation(s)
- Su-Ting Jiang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.,Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - An-Ni Chang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Lian-Tao Han
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.,Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Jie-Shu Guo
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.,Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Yuan-Hong Li
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.,Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Tong-Bao Liu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.,Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
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Roberto TN, Lima RF, Pascon RC, Idnurm A, Vallim MA. Biological functions of the autophagy-related proteins Atg4 and Atg8 in Cryptococcus neoformans. PLoS One 2020; 15:e0230981. [PMID: 32251488 PMCID: PMC7135279 DOI: 10.1371/journal.pone.0230981] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 03/12/2020] [Indexed: 11/28/2022] Open
Abstract
Autophagy is a mechanism responsible for intracellular degradation and recycling of macromolecules and organelles, essential for cell survival in adverse conditions. More than 40 autophagy-related (ATG) genes have been identified and characterized in fungi, among them ATG4 and ATG8. ATG4 encodes a cysteine protease (Atg4) that plays an important role in autophagy by initially processing Atg8 at its C-terminus region. Atg8 is a ubiquitin-like protein essential for the synthesis of the double-layer membrane that constitutes the autophagosome vesicle, responsible for delivering the cargo from the cytoplasm to the vacuole lumen. The contributions of Atg-related proteins in the pathogenic yeast in the genus Cryptococcus remain to be explored, to elucidate the molecular basis of the autophagy pathway. In this context, we aimed to investigate the role of autophagy-related proteins 4 and 8 (Atg4 and Atg8) during autophagy induction and their contribution with non-autophagic events in C. neoformans. We found that Atg4 and Atg8 are conserved proteins and that they interact physically with each other. ATG gene deletions resulted in cells sensitive to nitrogen starvation. ATG4 gene disruption affects Atg8 degradation and its translocation to the vacuole lumen, after autophagy induction. Both atg4 and atg8 mutants are more resistant to oxidative stress, have an impaired growth in the presence of the cell wall-perturbing agent Congo Red, and are sensitive to the proteasome inhibitor bortezomib (BTZ). By that, we conclude that in C. neoformans the autophagy-related proteins Atg4 and Atg8 play an important role in the autophagy pathway; which are required for autophagy regulation, maintenance of amino acid levels and cell adaptation to stressful conditions.
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Affiliation(s)
- Thiago Nunes Roberto
- Departamento de Ciências Biológicas, Universidade Federal de São Paulo, Diadema, São Paulo, Brazil
| | - Ricardo Ferreira Lima
- Departamento de Infectologia, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil
| | | | - Alexander Idnurm
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Marcelo Afonso Vallim
- Departamento de Ciências Biológicas, Universidade Federal de São Paulo, Diadema, São Paulo, Brazil
- * E-mail:
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Zhao X, Feng W, Zhu X, Li C, Ma X, Li X, Zhu X, Wei D. Conserved Autophagy Pathway Contributes to Stress Tolerance and Virulence and Differentially Controls Autophagic Flux Upon Nutrient Starvation in Cryptococcus neoformans. Front Microbiol 2019; 10:2690. [PMID: 32038502 PMCID: PMC6988817 DOI: 10.3389/fmicb.2019.02690] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 11/06/2019] [Indexed: 12/14/2022] Open
Abstract
Autophagy is mainly a catabolic process, which is used to cope with nutrient deficiency and various stress conditions. Human environment often imposes various stresses on Cryptococcus neoformans, a major fungal pathogen of immunocompromised individuals; therefore, autophagic response of C. neoformans to these stresses often determines its survival in the host. However, a systematic study on how autophagy related (ATG) genes influence on autophagic flux, virulence, stress response and pathogenicity of C. neoformans is lacking. In this study, 22 ATG-deficient strains were constructed to investigate their roles in virulence, pathogenesis, stress response, starvation tolerance and autophagic flux in C. neoformans. Our results showed that Atg6 and Atg14-03 significantly affect the growth of C. neoformans at 37°C and laccase production. Additionally, atg2Δ and atg6Δ strains were sensitive to oxidative stress caused by hydrogen peroxide. Approximately half of the atgΔ strains displayed higher sensitivity to 1.5 M NaCl and remarkably lower virulence in the Galleria mellonella model than the wild type. Autophagic flux in C. neoformans was dependent on the Atg1-Atg13, Atg5-Atg12-Atg16, and Atg2-Atg18 complexes and Atg11. Cleavage of the green fluorescent protein (GFP) from Atg8 was difficult to detect in these autophagy defective mutants; however, it was detected in the atg3Δ, atg4Δ, atg6Δ and atg14Δ strains. Additionally, no homologs of Saccharomyces cerevisiae ATG10 were detected in C. neoformans. Our results indicate that these ATG genes contribute differentially to carbon and nitrogen starvation tolerance in C. neoformans compared with S. cerevisiae. Overall, this study advances our knowledge of the specific roles of ATG genes in C. neoformans.
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Affiliation(s)
- Xueru Zhao
- National Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Weijia Feng
- National Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xiangyang Zhu
- National Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Chenxi Li
- Beijing Key Laboratory of Genetic Engineering Drug and Biotechnology, Institute of Biochemistry and Molecular Biology, School of Life Sciences, Beijing Normal University, Beijing, China
| | - Xiaoyu Ma
- Beijing Key Laboratory of Genetic Engineering Drug and Biotechnology, Institute of Biochemistry and Molecular Biology, School of Life Sciences, Beijing Normal University, Beijing, China
| | - Xin Li
- National Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xudong Zhu
- Beijing Key Laboratory of Genetic Engineering Drug and Biotechnology, Institute of Biochemistry and Molecular Biology, School of Life Sciences, Beijing Normal University, Beijing, China
| | - Dongsheng Wei
- National Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
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Ribeiro GF, de Góes CG, Onorio DS, de Campos CBL, Morais FV. Autophagy in Paracoccidioides brasiliensis under normal mycelia to yeast transition and under selective nutrient deprivation. PLoS One 2018; 13:e0202529. [PMID: 30138387 PMCID: PMC6107164 DOI: 10.1371/journal.pone.0202529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 08/03/2018] [Indexed: 11/23/2022] Open
Abstract
Paracoccidioides spp. is a thermally dimorphic fungus endemic to Latin America and the etiological agent of paracoccidioidomycosis (PCM), a granulomatous disease acquired through fungal propagule inhalation by its mammalian host. The infection is established after successful mycelia to yeast transition in the host pulmonary alveoli. The challenging environment inside the host exposes the fungus to the need of adaptation in order to circumvent nutritional, thermal, oxidative, immunological and other stresses that can directly affect their survival. Considering that autophagy is a response to abrupt environmental changes and is induced by stress conditions, this study hypothesizes that this process might be crucially involved in the adaptation of Paracoccidioides spp. to the host and, therefore, it is essential for the proper establishment of the disease. By labelling autophagous vesicles with monodansylcadaverine, autophagy was observed as an early event in cells during the normal mycelium to yeast transition, as well as in yeast cells of P. brasiliensis under glucose deprivation, and under either rapamycin or 3-methyladenine (3-MA). Findings in this study demonstrated that autophagy is triggered in P. brasiliensis during the thermal-induced mycelium to yeast transition and by glucose-limited conditions in yeasts, both of which modulated by rapamycin or 3-MA. Certainly, further genetic and in vivo analyses are needed in order to finally address the contribution of autophagy for adaptation. Yet, our data propose that autophagy possibly plays an important role in Paracoccidioides brasiliensis virulence and pathogenicity.
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Affiliation(s)
- Giselle Ferreira Ribeiro
- Laboratório de Biologia Celular e Molecular de Fungos, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP, Brazil
| | - Caroline Gonçalves de Góes
- Laboratório de Biologia Celular e Molecular de Fungos, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP, Brazil
| | - Diego Santos Onorio
- Laboratório de Biologia Celular e Molecular de Fungos, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP, Brazil
| | - Cláudia Barbosa Ladeira de Campos
- Laboratório de Bioquímica, Biologia Celular e Molecular de Fungos, Instituto de Ciência e Tecnologia–Universidade Federal de São Paulo–UNIFESP, São José dos Campos, SP, Brazil
| | - Flavia Villaça Morais
- Laboratório de Biologia Celular e Molecular de Fungos, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP, Brazil
- * E-mail:
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ATG Genes Influence the Virulence of Cryptococcus neoformans through Contributions beyond Core Autophagy Functions. Infect Immun 2018; 86:IAI.00069-18. [PMID: 29986893 DOI: 10.1128/iai.00069-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 07/03/2018] [Indexed: 12/31/2022] Open
Abstract
The process of autophagy is conserved among all eukaryotes from yeast to humans and is mainly responsible for bulk degradation of cellular contents and nutrient recycling during starvation. Autophagy has been suggested to play a role in the pathogenesis of the opportunistic human fungal pathogen Cryptococcus neoformans, potentially through a contribution to the export of virulence factors. In this study, we showed that deletion of each of the ATG1, ATG7, ATG8, and ATG9 genes in C. neoformans leads to autophagy-related phenotypes, including impaired amino acid homeostasis under nitrogen starvation. In addition, the atgΔ mutants were hypersensitive to inhibition of the ubiquitin-proteasome system, a finding consistent with a role in amino acid homeostasis. Although each atgΔ mutant was not markedly impaired in virulence factor production in vitro, we found that all four ATG genes contribute to C. neoformans virulence in a murine inhalation model of cryptococcosis. Interestingly, these mutants displayed significant differences in their ability to promote disease development. A more detailed investigation of virulence for the atg1Δ and atg8Δ mutants revealed that both strains stimulated an exaggerated host immune response, which, in turn, contributed to disease severity. Overall, our results suggest that different ATG genes are involved in nonautophagic functions and contribute to C. neoformans virulence beyond their core functions in autophagy.
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Sprenger M, Kasper L, Hensel M, Hube B. Metabolic adaptation of intracellular bacteria and fungi to macrophages. Int J Med Microbiol 2017; 308:215-227. [PMID: 29150190 DOI: 10.1016/j.ijmm.2017.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/21/2017] [Accepted: 11/05/2017] [Indexed: 02/07/2023] Open
Abstract
The mature phagosome of macrophages is a hostile environment for the vast majority of phagocytosed microbes. In addition to active destruction of the engulfed microbes by antimicrobial compounds, restriction of essential nutrients in the phagosomal compartment contributes to microbial growth inhibition and killing. However, some pathogenic microorganisms have not only developed various strategies to efficiently withstand or counteract antimicrobial activities, but also to acquire nutrients within macrophages for intracellular replication. Successful intracellular pathogens are able to utilize host-derived amino acids, carbohydrates and lipids as well as trace metals and vitamins during intracellular growth. This requires sophisticated strategies such as phagosome modification or escape, efficient nutrient transporters and metabolic adaptation. In this review, we discuss the metabolic adaptation of facultative intracellular bacteria and fungi to the intracellular lifestyle inside macrophages.
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Affiliation(s)
- Marcel Sprenger
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knoell-Institute, Jena, Germany
| | - Lydia Kasper
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knoell-Institute, Jena, Germany
| | - Michael Hensel
- Division of Microbiology, University Osnabrück, Osnabrück, Germany
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knoell-Institute, Jena, Germany; Friedrich Schiller University, Jena, Germany; Center for Sepsis Control and Care, University Hospital, Jena, Germany.
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