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Sousa IS, Tavares LFS, Silva BA, Moreno DSA, Alviano CS, Santos ALS, Kneipp LF. Calcineurin activity in Fonsecaea pedrosoi: tacrolimus and cyclosporine A inhibited conidia growth, filamentation and showed synergism with itraconazole. Braz J Microbiol 2024:10.1007/s42770-024-01463-2. [PMID: 39044105 DOI: 10.1007/s42770-024-01463-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Accepted: 07/11/2024] [Indexed: 07/25/2024] Open
Abstract
Fonsecaea pedrosoi is a melanized fungus that causes chromoblastomycosis (CBM), a tropical neglected disease responsible for chronic and disability-related subcutaneous mycosis. Given the challenging nature of CBM treatment, the study of new targets and novel bioactive drugs capable of improving patient life quality is urgent. In the present work, we detected a calcineurin activity in F. pedrosoi conidial form, employing primarily colorimetric, immunoblotting and flow cytometry assays. Our findings reveal that the calcineurin activity of F. pedrosoi was stimulated by Ca2+/calmodulin, inhibited by EGTA and specific inhibitors, such as tacrolimus (FK506) and cyclosporine A (CsA), and proved to be insensitive to okadaic acid. In addition, FK506 and CsA were able to affect the cellular viability and the fungal proliferation. This effect was corroborated by transmission electron microscopy that showed both calcineurin inhibitors promoted profound changes in the ultrastructure of conidia, causing mainly cytoplasm condensation and intense vacuolization that are clear indication of cell death. Our data indicated that FK506 exhibited the highest effectiveness, with a minimum inhibitory concentration (MIC) of 3.12 mg/L, whereas CsA required 15.6 mg/L to inhibit 100% of conidial growth. Interestingly, when both were combined with itraconazole, they demonstrated anti-F. pedrosoi activity, exhibiting a synergistic effect. Moreover, the fungal filamentation was affected after treatment with both calcineurin inhibitors. These data corroborate with other calcineurin studies in fungal cells and open up further discussions aiming to establish the role of this enzyme as a potential target for antifungal therapy against CBM infections.
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Affiliation(s)
- Ingrid S Sousa
- Laboratório de Taxonomia, Bioquímica e Bioprospecção de Fungos (LTBBF), Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, 21040-900, Brazil
| | - Lucilene F S Tavares
- Laboratório de Taxonomia, Bioquímica e Bioprospecção de Fungos (LTBBF), Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, 21040-900, Brazil
| | - Bianca A Silva
- Laboratório de Estudos Avançados de Microrganismos Emergentes e Resistentes (LEAMER), Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, 21941-901, Brazil
| | - Daniela S A Moreno
- Laboratório de Estrutura de Microrganismos, IMPG, UFRJ, Rio de Janeiro, 21941-902, Brazil
| | - Celuta S Alviano
- Laboratório de Estrutura de Microrganismos, IMPG, UFRJ, Rio de Janeiro, 21941-902, Brazil
| | - André L S Santos
- Laboratório de Estudos Avançados de Microrganismos Emergentes e Resistentes (LEAMER), Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, 21941-901, Brazil
- Rede Micologia RJ, Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Rio de Janeiro, 21941-901, Brazil
| | - Lucimar F Kneipp
- Laboratório de Taxonomia, Bioquímica e Bioprospecção de Fungos (LTBBF), Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, 21040-900, Brazil.
- Rede Micologia RJ, Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Rio de Janeiro, 21941-901, Brazil.
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Rabaan AA, Sulaiman T, Al-Ahmed SH, Buhaliqah ZA, Buhaliqah AA, AlYuosof B, Alfaresi M, Al Fares MA, Alwarthan S, Alkathlan MS, Almaghrabi RS, Abuzaid AA, Altowaileb JA, Al Ibrahim M, AlSalman EM, Alsalman F, Alghounaim M, Bueid AS, Al-Omari A, Mohapatra RK. Potential Strategies to Control the Risk of Antifungal Resistance in Humans: A Comprehensive Review. Antibiotics (Basel) 2023; 12:antibiotics12030608. [PMID: 36978475 PMCID: PMC10045400 DOI: 10.3390/antibiotics12030608] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/09/2023] [Accepted: 03/11/2023] [Indexed: 03/30/2023] Open
Abstract
Fungal infections are becoming one of the main causes of morbidity and mortality in people with weakened immune systems. Mycoses are becoming more common, despite greater knowledge and better treatment methods, due to the regular emergence of resistance to the antifungal medications used in clinical settings. Antifungal therapy is the mainstay of patient management for acute and chronic mycoses. However, the limited availability of antifungal drug classes limits the range of available treatments. Additionally, several drawbacks to treating mycoses include unfavourable side effects, a limited activity spectrum, a paucity of targets, and fungal resistance, all of which continue to be significant issues in developing antifungal drugs. The emergence of antifungal drug resistance has eliminated accessible drug classes as treatment choices, which significantly compromises the clinical management of fungal illnesses. In some situations, the emergence of strains resistant to many antifungal medications is a major concern. Although new medications have been developed to address this issue, antifungal drug resistance has grown more pronounced, particularly in patients who need long-term care or are undergoing antifungal prophylaxis. Moreover, the mechanisms that cause resistance must be well understood, including modifications in drug target affinities and abundances, along with biofilms and efflux pumps that diminish intracellular drug levels, to find novel antifungal drugs and drug targets. In this review, different classes of antifungal agents, and their resistance mechanisms, have been discussed. The latter part of the review focuses on the strategies by which we can overcome this serious issue of antifungal resistance in humans.
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Affiliation(s)
- Ali A Rabaan
- Molecular Diagnostic Laboratory, Johns Hopkins Aramco Healthcare, Dhahran 31311, Saudi Arabia
- College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
- Department of Public Health and Nutrition, The University of Haripur, Haripur 22610, Pakistan
| | - Tarek Sulaiman
- Infectious Diseases Section, Medical Specialties Department, King Fahad Medical City, Riyadh 12231, Saudi Arabia
| | - Shamsah H Al-Ahmed
- Specialty Paediatric Medicine, Qatif Central Hospital, Qatif 32654, Saudi Arabia
| | - Zainab A Buhaliqah
- Department of Family Medicine, Primary Healthcare Center, Dammam 32433, Saudi Arabia
| | - Ali A Buhaliqah
- College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
| | - Buthina AlYuosof
- Directorate of Public Health, Dammam Network, Eastern Health Cluster, Dammam 31444, Saudi Arabia
| | - Mubarak Alfaresi
- Department of Pathology and Laboratory Medicine, Zayed Military Hospital, Abu Dhabi 3740, United Arab Emirates
- Department of Pathology, College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai 505055, United Arab Emirates
| | - Mona A Al Fares
- Department of Internal Medicine, King Abdulaziz University Hospital, Jeddah 21589, Saudi Arabia
| | - Sara Alwarthan
- Department of Internal Medicine, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam 34212, Saudi Arabia
| | - Mohammed S Alkathlan
- Infectious Diseases Department, King Fahad Specialist Hospital, Buraydah 52382, Saudi Arabia
| | - Reem S Almaghrabi
- Organ Transplant Center of Excellence, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Abdulmonem A Abuzaid
- Medical Microbiology Department, Security Forces Hospital Programme, Dammam 32314, Saudi Arabia
| | - Jaffar A Altowaileb
- Microbiology Laboratory, Laboratory Department, Qatif Central Hospital, Qatif 32654, Saudi Arabia
| | - Maha Al Ibrahim
- Microbiology Laboratory, Laboratory Department, Qatif Central Hospital, Qatif 32654, Saudi Arabia
| | - Eman M AlSalman
- Department of Family Medicine, Primary Health Care Centers, Qatif Health Network, Qatif 31911, Saudi Arabia
| | - Fatimah Alsalman
- Department of Emergency Medicine, Oyun City Hospital, Al-Ahsa 36312, Saudi Arabia
| | | | - Ahmed S Bueid
- Microbiology Laboratory, King Faisal General Hospital, Al-Ahsa 31982, Saudi Arabia
| | - Awad Al-Omari
- College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
- Research Center, Dr. Sulaiman Al Habib Medical Group, Riyadh 11372, Saudi Arabia
| | - Ranjan K Mohapatra
- Department of Chemistry, Government College of Engineering, Keonjhar 758002, India
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Kurakado S, Matsumoto Y, Yamada T, Shimizu K, Wakasa S, Sugita T. Tacrolimus inhibits stress responses and hyphal formation via the calcineurin signaling pathway in Trichosporon asahii. Microbiol Immunol 2023; 67:49-57. [PMID: 36398783 DOI: 10.1111/1348-0421.13039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 10/09/2022] [Accepted: 11/07/2022] [Indexed: 11/19/2022]
Abstract
The pathogenic fungus Trichosporon asahii causes fatal deep-seated mycosis in immunocompromised patients. Calcineurin, which is widely conserved in eukaryotes, regulates cell growth and various stress responses in fungi. Tacrolimus (FK506), a calcineurin inhibitor, induces sensitivity to compounds that cause stress on the cell membrane and cell wall integrity. In this study, we demonstrated that FK506 affects stress responses and hyphal formation in T. asahii. In silico structural analysis revealed that amino acid residues in the binding site of the calcineurin-FKBP12 complex that interact with FK506 are conserved in T. asahii. The growth of T. asahii was delayed by FK506 in the presence of SDS or Congo red but not in the presence of calcium chloride. FK506 also inhibited hyphal formation in T. asahii. A mutant deficient of the cnb gene, which encodes the regulatory subunit B of calcineurin, exhibited stress sensitivities on exposure to SDS and Congo red and reduced the hyphal forming ability of T. asahii. In the cnb-deficient mutant, FK506 did not increase the stress sensitivity or reduce hyphal forming ability. These results suggest that FK506 affects stress responses and hyphal formation in T. asahii via the calcineurin signaling pathway.
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Affiliation(s)
- Sanae Kurakado
- Department of Microbiology, Meiji Pharmaceutical University, Tokyo, Japan
| | - Yasuhiko Matsumoto
- Department of Microbiology, Meiji Pharmaceutical University, Tokyo, Japan
| | - Tsuyoshi Yamada
- Teikyo University Institute of Medical Mycology, Tokyo, Japan.,Asia International Institute of Infectious Disease Control, Teikyo University, Tokyo, Japan
| | - Kiminori Shimizu
- Department of Biological Science and Technology, Tokyo University of Science, Tokyo, Japan.,Medical Mycology Research Center, Chiba University, Chiba, Japan
| | - Shogo Wakasa
- Department of Microbiology, Meiji Pharmaceutical University, Tokyo, Japan
| | - Takashi Sugita
- Department of Microbiology, Meiji Pharmaceutical University, Tokyo, Japan
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A critical role of calcineurin in stress responses, hyphal formation, and virulence of the pathogenic fungus Trichosporon asahii. Sci Rep 2022; 12:16126. [PMID: 36167890 PMCID: PMC9515189 DOI: 10.1038/s41598-022-20507-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 09/14/2022] [Indexed: 11/26/2022] Open
Abstract
Trichosporon asahii is a conditional pathogenic fungus that causes severe and sometimes fatal infections in immunocompromised patients. While calcineurin, an essential component of a calcium-dependent signaling pathway, is known to regulate stress resistance and virulence of some pathogenic fungi, its role in T. asahii has not been investigated. Here, we demonstrated that calcineurin gene-deficient T. asahii mutants are sensitive to high temperature as well as cell-membrane and cell-wall stress, and exhibit decreased hyphal formation and virulence against silkworms. Growth of T. asahii mutants deficient in genes encoding subunits of calcineurin, cna1 and cnb1, was delayed at 40 °C. The cna1 and cnb1 gene-deficient mutants also showed sensitivity to sodium dodecyl sulfate, Congo red, dithiothreitol, and tunicamycin. On the other hand, these mutants exhibited no sensitivity to caffeine, sorbitol, monensin, CaCl2, LiCl, NaCl, amphotericin B, fluconazole, or voriconazole. The ratio of hyphal formation in the cna1 and cnb1 gene-deficient mutants was decreased. Moreover, the virulence of the cna1 and cnb1 gene-deficient mutants against silkworms was attenuated. These phenotypes were restored by re-introducing each respective gene into the gene-deficient mutants. Our findings suggest that calcineurin has a role in regulating the cellular stress response and virulence of T. asahii.
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de Sousa HR, de Oliveira GP, Frazão SDO, Gorgonha KCDM, Rosa CP, Garcez EM, Lucas J, Correia AF, de Freitas WF, Borges HM, de Brito Alves LG, Paes HC, Trilles L, Lazera MDS, Teixeira MDM, Pinto VL, Felipe MSS, Casadevall A, Silva-Pereira I, Albuquerque P, Nicola AM. Faster Cryptococcus Melanization Increases Virulence in Experimental and Human Cryptococcosis. J Fungi (Basel) 2022; 8:393. [PMID: 35448624 PMCID: PMC9029458 DOI: 10.3390/jof8040393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/26/2022] [Accepted: 03/29/2022] [Indexed: 12/10/2022] Open
Abstract
Cryptococcus spp. are human pathogens that cause 181,000 deaths per year. In this work, we systematically investigated the virulence attributes of Cryptococcus spp. clinical isolates and correlated them with patient data to better understand cryptococcosis. We collected 66 C. neoformans and 19 C. gattii clinical isolates and analyzed multiple virulence phenotypes and host-pathogen interaction outcomes. C. neoformans isolates tended to melanize faster and more intensely and produce thinner capsules in comparison with C. gattii. We also observed correlations that match previous studies, such as that between secreted laccase and disease outcome in patients. We measured Cryptococcus colony melanization kinetics, which followed a sigmoidal curve for most isolates, and showed that faster melanization correlated positively with LC3-associated phagocytosis evasion, virulence in Galleria mellonella and worse prognosis in humans. These results suggest that the speed of melanization, more than the total amount of melanin Cryptococcus spp. produces, is crucial for virulence.
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Affiliation(s)
- Herdson Renney de Sousa
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Getúlio Pereira de Oliveira
- Division of Allergy and Inflammation, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA;
| | - Stefânia de Oliveira Frazão
- Laboratory of Molecular Biology of Pathogenic Fungi, Institute of Biological Sciences, University of Brasília, Brasília 70910-900, DF, Brazil; (S.d.O.F.); (I.S.-P.); (P.A.)
| | - Kaio César de Melo Gorgonha
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Camila Pereira Rosa
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Emãnuella Melgaço Garcez
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Joaquim Lucas
- Oswaldo Cruz Foundation (Fiocruz–Brasília), Brasília 70904-130, DF, Brazil; (J.L.J.); (V.L.P.J.)
| | | | - Waleriano Ferreira de Freitas
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Higor Matos Borges
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Lucas Gomes de Brito Alves
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Hugo Costa Paes
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Luciana Trilles
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases, Oswaldo Cruz Foundation (Fiocruz–Rio de Janeiro), Rio de Janeiro 21045-900, RJ, Brazil; (L.T.); (M.d.S.L.)
| | - Márcia dos Santos Lazera
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases, Oswaldo Cruz Foundation (Fiocruz–Rio de Janeiro), Rio de Janeiro 21045-900, RJ, Brazil; (L.T.); (M.d.S.L.)
| | - Marcus de Melo Teixeira
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
| | - Vitor Laerte Pinto
- Oswaldo Cruz Foundation (Fiocruz–Brasília), Brasília 70904-130, DF, Brazil; (J.L.J.); (V.L.P.J.)
| | - Maria Sueli Soares Felipe
- Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília 70790-160, DF, Brazil;
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA;
| | - Ildinete Silva-Pereira
- Laboratory of Molecular Biology of Pathogenic Fungi, Institute of Biological Sciences, University of Brasília, Brasília 70910-900, DF, Brazil; (S.d.O.F.); (I.S.-P.); (P.A.)
| | - Patrícia Albuquerque
- Laboratory of Molecular Biology of Pathogenic Fungi, Institute of Biological Sciences, University of Brasília, Brasília 70910-900, DF, Brazil; (S.d.O.F.); (I.S.-P.); (P.A.)
- Faculty of Ceilândia, University of Brasília, Brasília 72220-275, DF, Brazil
| | - André Moraes Nicola
- Faculty of Medicine, University of Brasília, Brasília 70910-900, DF, Brazil; (H.R.d.S.); (K.C.d.M.G.); (C.P.R.); (E.M.G.); (W.F.d.F.); (H.M.B.); (L.G.d.B.A.); (H.C.P.); (M.d.M.T.)
- Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília 70790-160, DF, Brazil;
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Gene, virulence and related regulatory mechanisms in Cryptococcus gattii. Acta Biochim Biophys Sin (Shanghai) 2022; 54:593-603. [PMID: 35593469 PMCID: PMC9828318 DOI: 10.3724/abbs.2022029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Cryptococcus gattii is a kind of basidiomycetous yeast, which grows in human and animal hosts. C. gattii has four distinct genomes, VGI/AFLP4, VGII/AFLP6, VGIII/AFLP5, and VGIV/AFLP7. The virulence of C. gattii is closely associated with genotype and related stress-signaling pathways, but the pathogenic mechanism of C. gattii has not been fully identified. With the development of genomics and transcriptomics, the relationship among genes, regulatory mechanisms, virulence, and treatment is gradually being recognized. In this review, to better understand how C. gattii causes disease and to characterize hypervirulent C. gattii strains, we summarize the current understanding of C. gattii genotypes, phenotypes, virulence, and the regulatory mechanisms.
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Hu G, Horianopoulos L, Sánchez-León E, Caza M, Jung W, Kronstad JW. The monothiol glutaredoxin Grx4 influences thermotolerance, cell wall integrity, and Mpk1 signaling in Cryptococcus neoformans. G3 (BETHESDA, MD.) 2021; 11:jkab322. [PMID: 34542604 PMCID: PMC8527476 DOI: 10.1093/g3journal/jkab322] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/27/2021] [Indexed: 02/07/2023]
Abstract
Monothiol glutaredoxins are important regulators of iron homeostasis that play conserved roles in the sensing and trafficking of iron-sulfur clusters. We previously characterized the role of the monothiol glutaredoxin Grx4 in iron homeostasis, the interaction with the iron regulator Cir1, and virulence in Cryptococcus neoformans. This important fungal pathogen causes cryptococcal meningoencephalitis in immunocompromised individuals worldwide. Here, we demonstrate that Grx4 is required for proliferation at elevated temperatures (both 37°C and 39°C) and under stress conditions. In particular, the grx4Δ mutant was hypersensitive to SDS, calcofluor white (CFW), and caffeine, suggesting that Grx4 is required for membrane and cell wall integrity (CWI). In this context, we found that Grx4 regulated the phosphorylation of the Mpk1 mitogen-activated protein kinase (MAPK) of the CWI pathway in cells grown at elevated temperature or upon treatment with CFW, caffeine, or SDS. The grx4Δ mutant also displayed increased sensitivity to FK506 and cyclosporin A, two inhibitors of the calcineurin pathway, indicating that Grx4 may influence growth at higher temperatures in parallel with calcineurin signaling. Upon thermal stress or calcium treatment, loss of Grx4 also caused partial mis-localization of Crz1, the transcription factor that is a calcineurin substrate. The phenotypes of the grx4Δ, crz1Δ, and cna1Δ (calcineurin) mutants suggest shared contributions to the regulation of temperature, cell wall, and other stresses. In summary, we show that Grx4 is also a key regulator of the responses to a variety of stress conditions in addition to its roles in iron homeostasis in C. neoformans.
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Affiliation(s)
- Guanggan Hu
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Linda Horianopoulos
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Eddy Sánchez-León
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Mélissa Caza
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Wonhee Jung
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Republic of Korea
| | - James W Kronstad
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Mattoon ER, Casadevall A, Cordero RJB. Beat the heat: correlates, compounds, and mechanisms involved in fungal thermotolerance. FUNGAL BIOL REV 2021. [DOI: 10.1016/j.fbr.2021.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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CgEnd3 Regulates Endocytosis, Appressorium Formation, and Virulence in the Poplar Anthracnose Fungus Colletotrichum gloeosporioides. Int J Mol Sci 2021; 22:ijms22084029. [PMID: 33919762 PMCID: PMC8103510 DOI: 10.3390/ijms22084029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/02/2021] [Accepted: 04/03/2021] [Indexed: 01/23/2023] Open
Abstract
The hemibiotrophic ascomycete fungus Colletotrichum gloeosporioides is the causal agent of anthracnose on numerous plants, and it causes considerable economic losses worldwide. Endocytosis is an essential cellular process in eukaryotic cells, but its roles in C. gloeosporioides remain unknown. In our study, we identified an endocytosis-related protein, CgEnd3, and knocked it out via polyethylene glycol (PEG)-mediated protoplast transformation. The lack of CgEnd3 resulted in severe defects in endocytosis. C. gloeosporioides infects its host through a specialized structure called appressorium, and ΔCgEnd3 showed deficient appressorium formation, melanization, turgor pressure accumulation, penetration ability of appressorium, cellophane membrane penetration, and pathogenicity. CgEnd3 also affected oxidant adaptation and the expression of core effectors during the early stage of infection. CgEnd3 contains one EF hand domain and four calcium ion-binding sites, and it is involved in calcium signaling. A lack of CgEnd3 changed the responses to cell-wall integrity agents and fungicide fludioxonil. However, CgEnd3 regulated appressorium formation and endocytosis in a calcium signaling-independent manner. Taken together, these results demonstrate that CgEnd3 plays pleiotropic roles in endocytosis, calcium signaling, cell-wall integrity, appressorium formation, penetration, and pathogenicity in C. gloeosporioides, and it suggests that CgEnd3 or endocytosis-related genes function as promising antifungal targets.
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F. Q. Smith D, Casadevall A. Fungal immunity and pathogenesis in mammals versus the invertebrate model organism Galleria mellonella. Pathog Dis 2021; 79:ftab013. [PMID: 33544836 PMCID: PMC7981337 DOI: 10.1093/femspd/ftab013] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 02/03/2021] [Indexed: 02/07/2023] Open
Abstract
In recent decades, Galleria mellonella (Lepidoptera: Pyralidae) have emerged as a model system to explore experimental aspects of fungal pathogenesis. The benefits of the G. mellonella model include being faster, cheaper, higher throughput and easier compared with vertebrate models. Additionally, as invertebrates, their use is subject to fewer ethical and regulatory issues. However, for G. mellonella models to provide meaningful insight into fungal pathogenesis, the G. mellonella-fungal interactions must be comparable to mammalian-fungal interactions. Indeed, as discussed in the review, studies suggest that G. mellonella and mammalian immune systems share many similarities, and fungal virulence factors show conserved functions in both hosts. While the moth model has opened novel research areas, many comparisons are superficial and leave large gaps of knowledge that need to be addressed concerning specific mechanisms underlying G. mellonella-fungal interactions. Closing these gaps in understanding will strengthen G. mellonella as a model for fungal virulence in the upcoming years. In this review, we provide comprehensive comparisons between fungal pathogenesis in mammals and G. mellonella from immunological and virulence perspectives. When information on an antifungal immune component is unknown in G. mellonella, we include findings from other well-studied Lepidoptera. We hope that by outlining this information available in related species, we highlight areas of needed research and provide a framework for understanding G. mellonella immunity and fungal interactions.
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Affiliation(s)
- Daniel F. Q. Smith
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
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11
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Stempinski PR, Zielinski JM, Dbouk NH, Huey ES, McCormack EC, Rubin AM, Chandrasekaran S, Kozubowski L. Genetic contribution to high temperature tolerance in Cryptococcus neoformans. Genetics 2021; 217:1-15. [PMID: 33683363 PMCID: PMC8045695 DOI: 10.1093/genetics/iyaa009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 10/24/2020] [Indexed: 11/12/2022] Open
Abstract
The human fungal pathogen Cryptococcus neoformans relies on a complex signaling network for the adaptation and survival at the host temperature. Protein phosphatase calcineurin is central to proliferation at 37°C but its exact contributions remain ill-defined. To better define genetic contributions to the C. neoformans temperature tolerance, 4031 gene knockouts were screened for genes essential at 37°C and under conditions that keep calcineurin inactive. Identified 83 candidate strains, potentially sensitive to 37°C, were subsequently subject to technologically simple yet robust assay, in which cells are exposed to a temperature gradient. This has resulted in identification of 46 genes contributing to the maximum temperature at which C. neoformans can proliferate (Tmax). The 46 mutants, characterized by a range of Tmax on drug-free media, were further assessed for Tmax under conditions that inhibit calcineurin, which led to identification of several previously uncharacterized knockouts exhibiting synthetic interaction with the inhibition of calcineurin. A mutant that lacked septin Cdc11 was among those with the lowest Tmax and failed to proliferate in the absence of calcineurin activity. To further define connections with calcineurin and the role for septins in high temperature growth, the 46 mutants were tested for cell morphology at 37°C and growth in the presence of agents disrupting cell wall and cell membrane. Mutants sensitive to calcineurin inhibition were tested for synthetic lethal interaction with deletion of the septin-encoding CDC12 and the localization of the septin Cdc3-mCherry. The analysis described here pointed to previously uncharacterized genes that were missed in standard growth assays indicating that the temperature gradient assay is a valuable complementary tool for elucidating the genetic basis of temperature range at which microorganisms proliferate.
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Affiliation(s)
- Piotr R Stempinski
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
| | - Jessica M Zielinski
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
| | - Nadir H Dbouk
- Department of Biology, Furman University, Greenville, SC 29613, USA
| | - Elizabeth S Huey
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
| | - Ellen C McCormack
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
| | - Alexander M Rubin
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
| | | | - Lukasz Kozubowski
- Department of Genetics & Biochemistry, Eukaryotic Pathogens Innovation Center (EPIC), Clemson University, Clemson, SC 29634, USA
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12
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LeBlanc EV, Polvi EJ, Veri AO, Privé GG, Cowen LE. Structure-guided approaches to targeting stress responses in human fungal pathogens. J Biol Chem 2020; 295:14458-14472. [PMID: 32796038 DOI: 10.1074/jbc.rev120.013731] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 08/11/2020] [Indexed: 11/06/2022] Open
Abstract
Fungi inhabit extraordinarily diverse ecological niches, including the human body. Invasive fungal infections have a devastating impact on human health worldwide, killing ∼1.5 million individuals annually. The majority of these deaths are attributable to species of Candida, Cryptococcus, and Aspergillus Treating fungal infections is challenging, in part due to the emergence of resistance to our limited arsenal of antifungal agents, necessitating the development of novel therapeutic options. Whereas conventional antifungal strategies target proteins or cellular components essential for fungal growth, an attractive alternative strategy involves targeting proteins that regulate fungal virulence or antifungal drug resistance, such as regulators of fungal stress responses. Stress response networks enable fungi to adapt, grow, and cause disease in humans and include regulators that are highly conserved across eukaryotes as well as those that are fungal-specific. This review highlights recent developments in elucidating crystal structures of fungal stress response regulators and emphasizes how this knowledge can guide the design of fungal-selective inhibitors. We focus on the progress that has been made with highly conserved regulators, including the molecular chaperone Hsp90, the protein phosphatase calcineurin, and the small GTPase Ras1, as well as with divergent stress response regulators, including the cell wall kinase Yck2 and trehalose synthases. Exploring structures of these important fungal stress regulators will accelerate the design of selective antifungals that can be deployed to combat life-threatening fungal diseases.
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Affiliation(s)
- Emmanuelle V LeBlanc
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Elizabeth J Polvi
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Amanda O Veri
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Gilbert G Privé
- Departments of Medical Biophysics and Biochemistry, University of Toronto, Toronto, Ontario, Canada.,Princess Margaret Cancer Centre, Toronto, Ontario, Canada
| | - Leah E Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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13
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Freitas e Silva KS, C. Silva L, Gonçales RA, Neves BJ, Soares CM, Pereira M. Setting New Routes for Antifungal Drug Discovery Against Pathogenic Fungi. Curr Pharm Des 2020; 26:1509-1520. [DOI: 10.2174/1381612826666200317125956] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 02/11/2020] [Indexed: 01/08/2023]
Abstract
:Fungal diseases are life-threatening to human health and responsible for millions of deaths around the world. Fungal pathogens lead to a high number of morbidity and mortality. Current antifungal treatment comprises drugs, such as azoles, echinocandins, and polyenes and the cure is not guaranteed. In addition, such drugs are related to severe side effects and the treatment lasts for an extended period. Thus, setting new routes for the discovery of effective and safe antifungal drugs should be a priority within the health care system. The discovery of alternative and efficient antifungal drugs showing fewer side effects is time-consuming and remains a challenge. Natural products can be a source of antifungals and used in combinatorial therapy. The most important natural products are antifungal peptides, antifungal lectins, antifungal plants, and fungi secondary metabolites. Several proteins, enzymes, and metabolic pathways could be targets for the discovery of efficient inhibitor compounds and recently, heat shock proteins, calcineurin, salinomycin, the trehalose biosynthetic pathway, and the glyoxylate cycle have been investigated in several fungal species. HSP protein inhibitors and echinocandins have been shown to have a fungicidal effect against azole-resistant fungi strains. Transcriptomic and proteomic approaches have advanced antifungal drug discovery and pointed to new important specific-pathogen targets. Certain enzymes, such as those from the glyoxylate cycle, have been a target of antifungal compounds in several fungi species. Natural and synthetic compounds inhibited the activity of such enzymes and reduced the ability of fungal cells to transit from mycelium to yeast, proving to be promisor antifungal agents. Finally, computational biology has developed effective approaches, setting new routes for early antifungal drug discovery since normal approaches take several years from discovery to clinical use. Thus, the development of new antifungal strategies might reduce the therapeutic time and increase the quality of life of patients.
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Affiliation(s)
- Kleber S. Freitas e Silva
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
| | - Lívia C. Silva
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
| | - Relber A. Gonçales
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
| | - Bruno J. Neves
- LabMol - Laboratory for Molecular Modeling and Drug Design, Faculdade de Farmácia, Universidade Federal de Goiás, Goiânia, GO, 74605-510, Brazil
| | - Célia M.A. Soares
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
| | - Maristela Pereira
- Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
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14
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Crystal structure and transient dimerization for the FKBP12 protein from the pathogenic fungus Candida auris. Biochem Biophys Res Commun 2020; 525:1103-1108. [PMID: 32184021 DOI: 10.1016/j.bbrc.2020.03.059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 03/10/2020] [Indexed: 11/21/2022]
Abstract
International concern over the recent emergence of Candida auris infections reflects not only its comparative ease of transmission and substantial mortality but the increasing level of resistance observed to all three major classes of antifungal drugs. Diminution in virulence has been reported for a wide range of fungal pathogens when the FK506-binding protein FKBP12 binds to that immunosuppressant drug and the binary complex then inhibits the fungal calcineurin signaling pathway. Structure-based drug design efforts have described modifications of FK506 which modestly reduce virulence for a number of fungal pathogens while also lessening the side effect of suppressing the tissue immunity response in the patient. To aid in such studies, we report the crystal structure of Candida auris FKBP12. As physiological relevance has been proposed for transient homodimerization interactions of distantly related fungal FKBP12 proteins, we report the solution NMR characterization of the homodimerization interactions of the FKBP12 proteins from both Candida auris and Candida glabrata.
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15
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Bashir Q, LeMaster DM, Hernández G. 1H, 13C, 15 N chemical shift assignments of the FKBP12 protein from the pathogenic fungi Candida auris and Candida glabrata. BIOMOLECULAR NMR ASSIGNMENTS 2020; 14:105-109. [PMID: 31950462 PMCID: PMC7566231 DOI: 10.1007/s12104-020-09928-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 01/08/2020] [Indexed: 06/10/2023]
Abstract
Multi-drug resistance is becoming an increasingly severe clinical challenge not only among pathogenic bacteria but among fungal pathogens as well. Drug design is inherently more challenging for the eukaryotic fungi due to their closer evolutionary similarity to humans. The recent rapid expansion in invasive infections throughout the world by Candida auris is of particular concern due to a substantial mortality rate, comparatively facile transmission, and an increasing level of resistance to all three of the major classes of anti-fungal drugs. One promising avenue for the development of an alternative class of anti-fungal agents currently under investigation is for drugs against the FK506-binding protein FKBP12 which, when bound to that drug, inhibits the fungal calcineurin signaling pathway with a resultant diminution in virulence. The specific challenge to this approach is that the homologous human calcineurin pathway functions in controlling the tissue immunity response, so that drug selectivity for the fungal pathway must be designed. To facilitate such efforts, we report the nearly complete backbone and sidechain resonances for the FKBP12 proteins of both Candida auris and clinically significant Candida glabrata fungi.
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Affiliation(s)
- Qamar Bashir
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
| | - David M LeMaster
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA
| | - Griselda Hernández
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY, 12201, USA.
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16
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Coelho C, Farrer RA. Pathogen and host genetics underpinning cryptococcal disease. ADVANCES IN GENETICS 2020; 105:1-66. [PMID: 32560785 DOI: 10.1016/bs.adgen.2020.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cryptococcosis is a severe fungal disease causing 220,000 cases of cryptococcal meningitis yearly. The etiological agents of cryptococcosis are taxonomically grouped into at least two species complexes belonging to the genus Cryptococcus. All of these yeasts are environmentally ubiquitous fungi (often found in soil, leaves and decaying wood, tree hollows, and associated with bird feces especially pigeon guano). Infection in a range of animals including humans begins following inhalation of spores or aerosolized yeasts. Recent advances provide fundamental insights into the factors from both the pathogen and its hosts which influence pathogenesis and disease. The complex interactions leading to disease in mammalian hosts have also updated from the availability of better genomic tools and datasets. In this review, we discuss recent genetic research on Cryptococcus, covering the epidemiology, ecology, and evolution of Cryptococcus pathogenic species. We also discuss the insights into the host immune response obtained from the latest genetic modified host models as well as insights from monogenic disorders in humans. Finally we highlight outstanding questions that can be answered in the near future using bioinformatics and genomic tools.
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Affiliation(s)
- Carolina Coelho
- Medical Research Council Centre for Medical Mycology at the University of Exeter, Exeter, United Kingdom
| | - Rhys A Farrer
- Medical Research Council Centre for Medical Mycology at the University of Exeter, Exeter, United Kingdom.
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17
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Park HS, Lee SC, Cardenas ME, Heitman J. Calcium-Calmodulin-Calcineurin Signaling: A Globally Conserved Virulence Cascade in Eukaryotic Microbial Pathogens. Cell Host Microbe 2020; 26:453-462. [PMID: 31600499 DOI: 10.1016/j.chom.2019.08.004] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/29/2019] [Accepted: 08/02/2019] [Indexed: 12/19/2022]
Abstract
Calcium is an abundant intracellular ion, and calcium homeostasis plays crucial roles in several cellular processes. The calcineurin signaling cascade is one of the major pathways governed by intracellular calcium. Calcineurin, a conserved protein from yeast to humans, is a calcium-calmodulin-dependent serine-threonine-specific phosphatase that orchestrates cellular stress responses. In eukaryotic microbial pathogens, calcineurin controls essential virulence pathways, such as the ability to grow at host temperature, morphogenesis to enable invasive hyphal growth, drug tolerance and resistance, cell wall integrity, and sexual development. Therefore, the calcineurin cascade is an attractive target in drug development against eukaryotic pathogens. In the present review, we summarize and discuss the current knowledge on the roles of calcineurin in eukaryotic microbial pathogens, focusing on fungi and parasitic protists.
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Affiliation(s)
- Hee-Soo Park
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Soo Chan Lee
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Maria E Cardenas
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
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18
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Vellanki S, Billmyre RB, Lorenzen A, Campbell M, Turner B, Huh EY, Heitman J, Lee SC. A Novel Resistance Pathway for Calcineurin Inhibitors in the Human-Pathogenic Mucorales Mucor circinelloides. mBio 2020; 11:e02949-19. [PMID: 31992620 PMCID: PMC6989107 DOI: 10.1128/mbio.02949-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 12/16/2019] [Indexed: 12/24/2022] Open
Abstract
Mucormycosis is an emerging lethal fungal infection in immunocompromised patients. Mucor circinelloides is a causal agent of mucormycosis and serves as a model system to understand genetics in Mucorales. Calcineurin is a conserved virulence factor in many pathogenic fungi, and calcineurin inhibition or deletion of the calcineurin regulatory subunit (CnbR) in Mucor results in a shift from hyphal to yeast growth. We analyzed 36 calcineurin inhibitor-resistant or bypass mutants that exhibited hyphal growth in the presence of calcineurin inhibitors or in the yeast-locked cnbRΔ mutant background without carrying any mutations in known calcineurin components. We found that a majority of the mutants had altered sequence in a gene, named here bycA (bypass of calcineurin). bycA encodes an amino acid permease. We verified that both the bycAΔ single mutant and the bycAΔ cnbRΔ double mutant are resistant to calcineurin inhibitor FK506, thereby demonstrating a novel mechanism of resistance against calcineurin inhibitors. We also found that the level of expression of bycA was significantly higher in the wild-type strain treated with FK506 and in the cnbRΔ mutants but was significantly lower in the wild-type strain without FK506 treatment. These findings suggest that bycA is a negative regulator of hyphal growth and/or a positive regulator of yeast growth in Mucor and that calcineurin suppresses expression of the bycA gene at the mRNA level to promote hyphal growth. BycA is involved in the Mucor hypha-yeast transition as our data demonstrate positive correlations among bycA expression, protein kinase A activity, and Mucor yeast growth. Also, calcineurin, independently of its role in morphogenesis, contributes to virulence traits, including phagosome maturation blockade, host cell damages, and proangiogenic growth factor induction during interactions with hosts.IMPORTANCEMucor is intrinsically resistant to most known antifungals, which makes mucormycosis treatment challenging. Calcineurin is a serine/threonine phosphatase that is widely conserved across eukaryotes. When calcineurin function is inhibited in Mucor, growth shifts to a less virulent yeast growth form, which makes calcineurin an attractive target for development of new antifungal drugs. Previously, we identified two distinct mechanisms through which Mucor can become resistant to calcineurin inhibitors involving Mendelian mutations in the gene for FKBP12, including mechanisms corresponding to calcineurin A or B subunits and epimutations silencing the FKBP12 gene. Here, we identified a third novel mechanism where loss-of-function mutations in the amino acid permease corresponding to the bycA gene contribute to resistance against calcineurin inhibitors. When calcineurin activity is absent, BycA can activate protein kinase A (PKA) to promote yeast growth via a cAMP-independent pathway. Our data also show that calcineurin activity contributes to host-pathogen interactions primarily in the pathogenesis of Mucor.
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Affiliation(s)
- Sandeep Vellanki
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - R Blake Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Alejandra Lorenzen
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Micaela Campbell
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Broderick Turner
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Eun Young Huh
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Soo Chan Lee
- South Texas Center for Emerging Infectious Diseases (STCEID), Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
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Maryam M, Fu MS, Alanio A, Camacho E, Goncalves DS, Faneuff EE, Grossman NT, Casadevall A, Coelho C. The enigmatic role of fungal annexins: the case of Cryptococcus neoformans. MICROBIOLOGY-SGM 2019; 165:852-862. [PMID: 31140968 DOI: 10.1099/mic.0.000815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Annexins are multifunctional proteins that bind to phospholipid membranes in a calcium-dependent manner. Annexins play a myriad of critical and well-characterized roles in mammals, ranging from membrane repair to vesicular secretion. The role of annexins in the kingdoms of bacteria, protozoa and fungi have been largely overlooked. The fact that there is no known homologue of annexins in the yeast model organism Saccharomyces cerevisiae may contribute to this gap in knowledge. However, annexins are found in most medically important fungal pathogens, with the notable exception of Candida albicans. In this study we evaluated the function of the one annexin gene in Cryptococcus neoformans, a causative agent of cryptococcosis. This gene CNAG_02415, is annotated in the C. neoformans genome as a target of calcineurin through its transcription factor Crz1, and we propose to update its name to cryptococcal annexin, AnnexinC1. C. neoformans strains deleted for AnnexinC1 revealed no difference in survival after exposure to various chemical stressors relative to wild-type strain, as well as no major alteration in virulence or mating. The only alteration observed in strains deleted for AnnexinC1 was a small increase in the titan cells' formation in vitro. The preservation of annexins in many different fungal species suggests an important function, and therefore the lack of a strong phenotype for annexin-deficient C. neoformans indicates either the presence of redundant genes that can compensate for the absence of AnnexinC1 function or novel functions not revealed by standard assays of cell function and pathogenicity.
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Affiliation(s)
- Maria Maryam
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Man Shun Fu
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Alexandre Alanio
- Institut Pasteur, Molecular Mycology Unit, CNRS UMR2000, Université Paris Diderot, Sorbonne Paris Cité ; Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France.,W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Emma Camacho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Diego S Goncalves
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,Universidade Federal Fluminense, Rio Janeiro, Brazil
| | - Eden E Faneuff
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,Department of Biological Sciences, California State Polytechnic University, Pomona CA, USA
| | - Nina T Grossman
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Carolina Coelho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.,Medical Research Council Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Ashgrove Road West, Aberdeen AB252ZD, UK
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20
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Zheng YH, Ma YY, Ding Y, Chen XQ, Gao GX. An insight into new strategies to combat antifungal drug resistance. DRUG DESIGN DEVELOPMENT AND THERAPY 2018; 12:3807-3816. [PMID: 30464412 PMCID: PMC6225914 DOI: 10.2147/dddt.s185833] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Invasive fungal infections especially in immunocompromised patients represent a dominating cause of mortality. The most commonly used antifungal agents can be divided into three broad categories, including triazoles, echinocandins and polyenes. Antifungal resistance is on the increase, posing a growing threat to the stewardship of immunocompromised patients with fungal infections. The paucity of currently available antifungals leads to the rapid emergence of drug resistance and thus aggravates the refractoriness of invasive fungal infections. Therefore, deep exploration into mechanisms of drug resistance and search for new antifungal targets are required. This review highlights the therapeutic strategies targeting Hsp90, calcineurin, trehalose biosynthesis and sphingolipids biosynthesis, in an attempt to provide clinical evidence for overcoming drug resistance and to form the rationale for combination therapy of conventional antifungals and agents with novel mechanisms of action. What’s more, this review also gives a concise introduction of three new-fashioned antifungals, including carboxymethyl chitosan, silver nanoparticles and chromogranin A-N46.
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Affiliation(s)
- Yan-Hua Zheng
- Department of Hematology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China, ;
| | - Yue-Yun Ma
- Department of Clinical Laboratory Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Yi Ding
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Xie-Qun Chen
- Department of Hematology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China, ;
| | - Guang-Xun Gao
- Department of Hematology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China, ;
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21
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Evolutionarily Conserved and Divergent Roles of Unfolded Protein Response (UPR) in the Pathogenic Cryptococcus Species Complex. Sci Rep 2018; 8:8132. [PMID: 29802329 PMCID: PMC5970146 DOI: 10.1038/s41598-018-26405-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/10/2018] [Indexed: 01/01/2023] Open
Abstract
The unfolded protein response (UPR) pathway, consisting of the evolutionarily conserved Ire1 kinase/endonuclease and the bZIP transcription factor Hxl1, is critical for the pathogenicity of Cryptococcus neoformans; however, its role remains unknown in other pathogenic Cryptococcus species. Here, we investigated the role of the UPR pathway in C. deuterogattii, which causes pneumonia and systemic cryptococcosis, even in immunocompetent individuals. In response to ER stress, C. deuterogattii Ire1 triggers unconventional splicing of HXL1 to induce the expression of UPR target genes such as KAR2, DER1, ALG7, and ERG29. Furthermore, C. deuterogattii Ire1 is required for growth at mammalian body temperature, similar to C. neoformans Ire1. However, deletion of HXL1 does not significantly affect the growth of C. deuterogattii at 37 °C, which is in contrast to the indispensable role of HXL1 in the growth of C. neoformans at 37 °C. Nevertheless, both C. deuterogattii ire1Δ and hxl1Δ mutants are avirulent in a murine model of systemic cryptococcosis, suggesting that a non-thermotolerance phenotypic trait also contributes to the role of the UPR pathway in the virulence of pathogenic Cryptococcus species. In conclusion, the UPR pathway plays redundant and distinct roles in the virulence of members of the pathogenic Cryptococcus species complex.
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Plant Homeodomain Genes Play Important Roles in Cryptococcal Yeast-Hypha Transition. Appl Environ Microbiol 2018; 84:AEM.01732-17. [PMID: 29500261 DOI: 10.1128/aem.01732-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Accepted: 02/19/2018] [Indexed: 11/20/2022] Open
Abstract
Cryptococcus neoformans is a major opportunistic fungal pathogen. Like many dimorphic fungal pathogens, C. neoformans can undergo morphological transition from the yeast form to the hypha form, and its morphotype is tightly linked to its virulence. Although some genetic factors controlling morphogenesis have been identified, little is known about the epigenetic regulation in this process. Proteins with the plant homeodomain (PHD) finger, a structurally conserved domain in eukaryotes, were first identified in plants and are known to be involved in reading and effecting chromatin modification. Here, we investigated the role of the PHD finger family genes in Cryptococcus mating and yeast-hypha transition. We found 16 PHD finger domains distributed among 15 genes in the Cryptococcus genome, with two genes, ZNF1α and RUM1α, located in the mating type locus. We deleted these 15 PHD genes and examined the impact of their disruption on cryptococcal morphogenesis. The deletion of five PHD finger genes dramatically affected filamentation. The rum1αΔ and znf1αΔ mutants showed enhanced ability to initiate filamentation but impaired ability to maintain filamentous growth. The bye1Δ and the phd11Δ mutants exhibited enhanced filamentation, while the set302Δ mutants displayed reduced filamentation. Ectopic overexpression of these five genes in the corresponding null mutants partially or completely restored the defect in filamentation. Furthermore, we demonstrated that Phd11, a suppressor of filamentation, regulates the yeast-hypha transition through the known master regulator Znf2. The findings indicate the importance of epigenetic regulation in controlling dimorphic transition in C. neoformansIMPORTANCE Morphotype is known to have a profound impact on cryptococcal interaction with various hosts, including mammalian hosts. The yeast form of Cryptococcus neoformans is considered the virulent form, while its hyphal form is attenuated in mammalian models of cryptococcosis. Although some genetic regulators critical for cryptococcal morphogenesis have been identified, little is known about epigenetic regulation in this process. Given that plant homeodomain (PHD) finger proteins are involved in reading and effecting chromatin modification and their functions are unexplored in C. neoformans, we investigated the roles of the 15 PHD finger genes in Cryptococcus mating and yeast-hypha transition. Five of them profoundly affect filamentation as either a suppressor or an activator. Phd11, a suppressor of filamentation, regulates this process via Znf2, a known master regulator of morphogenesis. Thus, epigenetic regulation, coupled with genetic regulation, controls this yeast-hypha transition event.
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Xu L, Li Y, Biggins JB, Bowman BR, Verdine GL, Gloer JB, Alspaugh JA, Bills GF. Identification of cyclosporin C from Amphichorda felina using a Cryptococcus neoformans differential temperature sensitivity assay. Appl Microbiol Biotechnol 2018; 102:2337-2350. [PMID: 29396588 DOI: 10.1007/s00253-018-8792-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 01/02/2018] [Accepted: 01/16/2018] [Indexed: 12/25/2022]
Abstract
We used a temperature differential assay with the opportunistic fungal pathogen Cryptococcus neoformans as a simple screening platform to detect small molecules with antifungal activity in natural product extracts. By screening of a collection extracts from two different strains of the coprophilous fungus, Amphichorda felina, we detected strong, temperature-dependent antifungal activity using a two-plate agar zone of inhibition assay at 25 and 37 °C. Bioassay-guided fractionation of the crude extract followed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR) identified cyclosporin C (CsC) as the main component of the crude extract responsible for growth inhibition of C. neoformans at 37 °C. The presence of CsC was confirmed by comparison with a commercial standard. We sequenced the genome of A. felina to identify and annotate the CsC biosynthetic gene cluster. The only previously characterized gene cluster for the biosynthesis of similar compounds is that of the related immunosuppressant drug cyclosporine A (CsA). The CsA and CsC gene clusters share a high degree of synteny and sequence similarity. Amino acid changes in the adenylation domain of the CsC nonribosomal peptide synthase's sixth module may be responsible for the substitution of L-threonine compared to L-α-aminobutyric acid in the CsA peptide core. This screening strategy promises to yield additional antifungal natural products with a focused spectrum of antimicrobial activity.
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Affiliation(s)
- Lijian Xu
- Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, 1881 East Road, 3SCR6.4676, Houston, TX, 77054, USA
- College of Agricultural Resources and Environment, Heilongjiang University, Harbin, 150080, China
| | - Yan Li
- Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, 1881 East Road, 3SCR6.4676, Houston, TX, 77054, USA
- Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - John B Biggins
- LifeMine Therapeutics, 430 E. 29th Street, Suite 830, New York, NY, 10016, USA
| | - Brian R Bowman
- LifeMine Therapeutics, 430 E. 29th Street, Suite 830, New York, NY, 10016, USA
| | - Gregory L Verdine
- LifeMine Therapeutics, 430 E. 29th Street, Suite 830, New York, NY, 10016, USA
| | - James B Gloer
- Department of Chemistry, University of Iowa, Iowa City, IA, 52242, USA
| | - J Andrew Alspaugh
- Departments of Biochemistry and Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Gerald F Bills
- Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, 1881 East Road, 3SCR6.4676, Houston, TX, 77054, USA.
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Abstract
Fungi must meet four criteria to infect humans: growth at human body temperatures, circumvention or penetration of surface barriers, lysis and absorption of tissue, and resistance to immune defenses, including elevated body temperatures. Morphogenesis between small round, detachable cells and long, connected cells is the mechanism by which fungi solve problems of locomotion around or through host barriers. Secretion of lytic enzymes, and uptake systems for the released nutrients, are necessary if a fungus is to nutritionally utilize human tissue. Last, the potent human immune system evolved in the interaction with potential fungal pathogens, so few fungi meet all four conditions for a healthy human host. Paradoxically, the advances of modern medicine have made millions of people newly susceptible to fungal infections by disrupting immune defenses. This article explores how different members of four fungal phyla use different strategies to fulfill the four criteria to infect humans: the Entomophthorales, the Mucorales, the Ascomycota, and the Basidiomycota. Unique traits confer human pathogenic potential on various important members of these phyla: pathogenic Onygenales comprising thermal dimorphs such as Histoplasma and Coccidioides; the Cryptococcus spp. that infect immunocompromised as well as healthy humans; and important pathogens of immunocompromised patients-Candida, Pneumocystis, and Aspergillus spp. Also discussed are agents of neglected tropical diseases important in global health such as mycetoma and paracoccidiomycosis and common pathogens rarely implicated in serious illness such as dermatophytes. Commensalism is considered, as well as parasitism, in shaping genomes and physiological systems of hosts and fungi during evolution.
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Xu X, Lin J, Zhao Y, Kirkman E, So YS, Bahn YS, Lin X. Glucosamine stimulates pheromone-independent dimorphic transition in Cryptococcus neoformans by promoting Crz1 nuclear translocation. PLoS Genet 2017; 13:e1006982. [PMID: 28898238 PMCID: PMC5595294 DOI: 10.1371/journal.pgen.1006982] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 08/17/2017] [Indexed: 02/06/2023] Open
Abstract
Morphotype switch is a cellular response to external and internal cues. The Cryptococcus neoformans species complex can undergo morphological transitions between the yeast and the hypha form, and such morphological changes profoundly affect cryptococcal interaction with various hosts. Filamentation in Cryptococcus was historically considered a mating response towards pheromone. Recent studies indicate the existence of pheromone-independent signaling pathways but their identity or the effectors remain unknown. Here, we demonstrated that glucosamine stimulated the C. neoformans species complex to undergo self-filamentation. Glucosamine-stimulated filamentation was independent of the key components of the pheromone pathway, which is distinct from pheromone-elicited filamentation. Glucosamine stimulated self-filamentation in H99, a highly virulent serotype A clinical isolate and a widely used reference strain. Through a genetic screen of the deletion sets made in the H99 background, we found that Crz1, a transcription factor downstream of calcineurin, was essential for glucosamine-stimulated filamentation despite its dispensability for pheromone-mediated filamentation. Glucosamine promoted Crz1 translocation from the cytoplasm to the nucleus. Interestingly, multiple components of the high osmolality glycerol response (HOG) pathway, consisting of the phosphorelay system and some of the Hog1 MAPK module, acted as repressors of glucosamine-elicited filamentation through their calcineurin-opposing effect on Crz1’s nuclear translocation. Surprisingly, glucosamine-stimulated filamentation did not require Hog1 itself and was distinct from the conventional general stress response. The results demonstrate that Cryptococcus can resort to multiple genetic pathways for morphological transition in response to different stimuli. Given that the filamentous form attenuates cryptococcal virulence and is immune-stimulatory in mammalian models, the findings suggest that morphogenesis is a fertile ground for future investigation into novel means to compromise cryptococcal pathogenesis. Cryptococcal meningitis claims half a million lives each year. There is no clinically available vaccine and the current antifungal therapies have serious limitations. Thus identifying cryptococcal specific programs that can be targeted for antifungal or vaccine development is of great value. We have shown previously that switching from the yeast to the hypha form drastically attenuates/abolishes cryptococcal virulence. Cryptococcal cells in the filamentous form also trigger host immune responses that can protect the host from a subsequent lethal challenge. However, self-filamentation is rarely observed in serotype A isolates that are responsible for the vast majority of cryptococcosis cases. In this study, we found that glucosamine stimulated self-filamentation in genetically distinct strains of the Cryptococcus species complex, including the most commonly used serotype A reference strain H99. We demonstrated that filamentation elicited by glucosamine did not depend on the pheromone pathway, but it requires the calcineurin transcription factor Crz1. Glucosamine promotes nuclear translocation of Crz1, which is positively controlled by the phosphatase calcineurin and is suppressed by the HOG pathway. These findings raise the possibility of manipulating genetic pathways controlling fungal morphogenesis against diseases caused by the Cryptococcus species complex.
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Affiliation(s)
- Xinping Xu
- Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail: (XL); (XX)
| | - Jianfeng Lin
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
| | - Youbao Zhao
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
| | - Elyssa Kirkman
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Yee-Seul So
- Department of Biotechnology, Yonsei University, Seoul, Korea
| | - Yong-Sun Bahn
- Department of Biotechnology, Yonsei University, Seoul, Korea
| | - Xiaorong Lin
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
- * E-mail: (XL); (XX)
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Heat shock protein 90 localizes to the surface and augments virulence factors of Cryptococcus neoformans. PLoS Negl Trop Dis 2017; 11:e0005836. [PMID: 28783748 PMCID: PMC5559104 DOI: 10.1371/journal.pntd.0005836] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 08/16/2017] [Accepted: 07/26/2017] [Indexed: 12/15/2022] Open
Abstract
Background Thermotolerance is an essential attribute for pathogenesis of Cryptococcus as exemplified by the fact that only two species in the genus, which can grow at 37°C, are human pathogens. Species which have other virulence factors including capsule formation and melanisation, but lack the ability to propagate at 37°C are not pathogenic. In another related fungal pathogen, Candida albicans, heat shock protein 90 has been implicated to be a central player in commanding pathogenicity by governing yeast to hyphal transition and drug resistance. Exploring Hsp90 biology in Cryptococcus in context of thermotolerance may thus highlight important regulatory principles of virulence and open new therapeutic avenues. Methodology/Principal findings Hsp90 is involved in regulating thermotolerance in Cryptococcus as indicated by growth hypersensitivity at 37°C upon mild compromise of Hsp90 function relative to 25°C. Biochemical studies revealed a more potent inhibition of ATPase activity by pharmacological inhibitor 17-AAG at 37°C as compared to 25°C. Catalytic efficiency of the protein at 37°C was found to be 6.39×10−5μM-1. Furthermore, indirect immunofluorescence analysis using a specific antibody revealed cell surface localization of Hsp90 via ER Golgi classical secretory pathway. Hsp90 was found to be induced under capsule inducing conditions and Hsp90 inhibition led to decrease in capsular volume. Finally compromising Hsp90 function improved anidulafungin tolerance in Cryptococcus. Conclusions/Significance Our findings highlight that Hsp90 regulates pathogenicity of the fungus by myriad ways. Firstly, it is involved in mediating thermotolerance which implies targeting Hsp90 can abrogate thermotolerance and hence growth of the fungus. Secondly, this study provides the first report of biochemical properties of Hsp90 of a pathogenic fungus. Finally, since Hsp90 is localised at the cell wall, targeting cell surface Hsp90 can represent a novel strategy to combat this lethal infection. Thermotolerance is a pre-requisite for microbes to propagate successfully as human pathogens. In this study, we have investigated the role of Heat shock protein 90 in the pathogenesis and thermotolerance of C. neoformans, an environmental fungus that causes meningoencephalitis in humans. We show that thermotolerance of Cryptococcus critically depends on Hsp90 function as modest inhibition of Hsp90 function, robustly compromised growth of the fungus at 37°C with little effect at 25°C. This observation correlated with the fact that pharmacological inhibitor, 17-AAG also showed a more potent inhibition of ATPase activity of the protein at 37°C as indicated by a lower IC50 as compared to 25°C. Indirect immunofluorescence analysis using an antibody specific to CnHsp90 revealed cell surface localization of Hsp90. BFA sensitivity of such surface localization indicated involvement of ER-Golgi classical secretory pathway for this localization. Furthermore, inhibition of Hsp90 function not only abrogated the natural resistance of C. neoformans to cell wall targeting inhibitors echinocandins but also led to decrease in capsular assembly which is one of the classical virulence determinants of the pathogen. In all, this study provides the first detailed biochemical as well as functional insights into the role of Hsp90 in governing thermotolerance and augmenting virulence factors in C. neoformans.
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Juvvadi PR, Lee SC, Heitman J, Steinbach WJ. Calcineurin in fungal virulence and drug resistance: Prospects for harnessing targeted inhibition of calcineurin for an antifungal therapeutic approach. Virulence 2017; 8:186-197. [PMID: 27325145 PMCID: PMC5354160 DOI: 10.1080/21505594.2016.1201250] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 06/07/2016] [Accepted: 06/08/2016] [Indexed: 01/26/2023] Open
Abstract
Increases in the incidence and mortality due to the major invasive fungal infections such as aspergillosis, candidiasis and cryptococcosis caused by the species of Aspergillus, Candida and Cryptococcus, are a growing threat to the immunosuppressed patient population. In addition to the limited armamentarium of the current classes of antifungal agents available (pyrimidine analogs, polyenes, azoles, and echinocandins), their toxicity, efficacy and the emergence of resistance are major bottlenecks limiting successful patient outcomes. Although these drugs target distinct fungal pathways, there is an urgent need to develop new antifungals that are more efficacious, fungal-specific, with reduced or no toxicity and simultaneously do not induce resistance. Here we review several lines of evidence which indicate that the calcineurin signaling pathway, a target of the immunosuppressive drugs FK506 and cyclosporine A, orchestrates growth, virulence and drug resistance in a variety of fungal pathogens and can be exploited for novel antifungal drug development.
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Affiliation(s)
- Praveen R. Juvvadi
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University School of Medicine, Durham, NC, USA
| | - Soo Chan Lee
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC, USA
| | - Joseph Heitman
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC, USA
- Department of Medicine, Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - William J. Steinbach
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University School of Medicine, Durham, NC, USA
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC, USA
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Scorzoni L, de Paula E Silva ACA, Marcos CM, Assato PA, de Melo WCMA, de Oliveira HC, Costa-Orlandi CB, Mendes-Giannini MJS, Fusco-Almeida AM. Antifungal Therapy: New Advances in the Understanding and Treatment of Mycosis. Front Microbiol 2017; 8:36. [PMID: 28167935 PMCID: PMC5253656 DOI: 10.3389/fmicb.2017.00036] [Citation(s) in RCA: 243] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 01/06/2017] [Indexed: 01/08/2023] Open
Abstract
The high rates of morbidity and mortality caused by fungal infections are associated with the current limited antifungal arsenal and the high toxicity of the compounds. Additionally, identifying novel drug targets is challenging because there are many similarities between fungal and human cells. The most common antifungal targets include fungal RNA synthesis and cell wall and membrane components, though new antifungal targets are being investigated. Nonetheless, fungi have developed resistance mechanisms, such as overexpression of efflux pump proteins and biofilm formation, emphasizing the importance of understanding these mechanisms. To address these problems, different approaches to preventing and treating fungal diseases are described in this review, with a focus on the resistance mechanisms of fungi, with the goal of developing efficient strategies to overcoming and preventing resistance as well as new advances in antifungal therapy. Due to the limited antifungal arsenal, researchers have sought to improve treatment via different approaches, and the synergistic effect obtained by the combination of antifungals contributes to reducing toxicity and could be an alternative for treatment. Another important issue is the development of new formulations for antifungal agents, and interest in nanoparticles as new types of carriers of antifungal drugs has increased. In addition, modifications to the chemical structures of traditional antifungals have improved their activity and pharmacokinetic parameters. Moreover, a different approach to preventing and treating fungal diseases is immunotherapy, which involves different mechanisms, such as vaccines, activation of the immune response and inducing the production of host antimicrobial molecules. Finally, the use of a mini-host has been encouraging for in vivo testing because these animal models demonstrate a good correlation with the mammalian model; they also increase the speediness of as well as facilitate the preliminary testing of new antifungal agents. In general, many years are required from discovery of a new antifungal to clinical use. However, the development of new antifungal strategies will reduce the therapeutic time and/or increase the quality of life of patients.
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Affiliation(s)
- Liliana Scorzoni
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Ana C A de Paula E Silva
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Caroline M Marcos
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Patrícia A Assato
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Wanessa C M A de Melo
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Haroldo C de Oliveira
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Caroline B Costa-Orlandi
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Maria J S Mendes-Giannini
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
| | - Ana M Fusco-Almeida
- Laboratório de Micologia Clínica, Departamento de Análises Clínicas, Universidade Estadual Paulista (UNESP), Faculdade de Ciências Farmacêuticas Araraquara, Brasil
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de Castro PA, Chiaratto J, Morais ER, Dos Reis TF, Mitchell TK, Brown NA, Goldman GH. The putative flavin carrier family FlcA-C is important for Aspergillus fumigatus virulence. Virulence 2016; 8:797-809. [PMID: 27652896 DOI: 10.1080/21505594.2016.1239010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Aspergillus fumigatus is an opportunistic fungal pathogen and the most important species causing pulmonary fungal infections. The signaling by calcium is very important for A. fumigatus pathogenicity and it is regulated by the transcription factor CrzA. We have previously used used ChIP-seq (Chromatin Immunoprecipitation DNA sequencing) aiming to identify gene targets regulated by CrzA. We have identified among several genes regulated by calcium stress, the putative flavin transporter, flcA. This transporter belongs to a small protein family composed of FlcA, B, and C. The ΔflcA null mutant showed several phenotypes, such as morphological defects, increased sensitivity to calcium chelating-agent ethylene glycol tetraacetic acid (EGTA), cell wall or oxidative damaging agents and metals, repre-sentative of deficiencies in calcium signaling and iron homeostasis. Increasing calcium concentrations improved significantly the ΔflcA growth and conidiation, indicating that ΔflcA mutant has calcium insufficiency. Finally, ΔflcA-C mutants showed reduced flavin adenine dinucleotide (FAD) and were avirulent in a low dose murine infection model.
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Affiliation(s)
- Patrícia A de Castro
- a Faculdade de Ciências Farmacêuticas de Ribeirão Preto and Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , Brazil
| | - Jéssica Chiaratto
- a Faculdade de Ciências Farmacêuticas de Ribeirão Preto and Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , Brazil
| | - Enyara Rezende Morais
- a Faculdade de Ciências Farmacêuticas de Ribeirão Preto and Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , Brazil
| | - Thaila Fernanda Dos Reis
- a Faculdade de Ciências Farmacêuticas de Ribeirão Preto and Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , Brazil
| | - Thomas K Mitchell
- b Department of Plant Pathology , The Ohio State University , Columbus , OH , USA
| | - Neil A Brown
- c Plant Biology and Crop Science, Rothamsted Research , Harpenden, Herts , UK
| | - Gustavo H Goldman
- a Faculdade de Ciências Farmacêuticas de Ribeirão Preto and Faculdade de Medicina de Ribeirão Preto , Universidade de São Paulo , Ribeirão Preto , Brazil
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Steenwyk JL, Soghigian JS, Perfect JR, Gibbons JG. Copy number variation contributes to cryptic genetic variation in outbreak lineages of Cryptococcus gattii from the North American Pacific Northwest. BMC Genomics 2016; 17:700. [PMID: 27590805 PMCID: PMC5009542 DOI: 10.1186/s12864-016-3044-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/24/2016] [Indexed: 12/13/2022] Open
Abstract
Background Copy number variants (CNVs) are a class of structural variants (SVs) and are defined as fragments of DNA that are present at variable copy number in comparison with a reference genome. Recent advances in bioinformatics methodologies and sequencing technologies have enabled the high-resolution quantification of genome-wide CNVs. In pathogenic fungi SVs have been shown to alter gene expression, influence host specificity, and drive fungicide resistance, but little attention has focused specifically on CNVs. Using publicly available sequencing data, we identified 90 isolates across 212 Cryptococcus gattii genomes that belong to the VGII subgroups responsible for the recent deadly outbreaks in the North American Pacific Northwest. We generated CNV profiles for each sample to investigate the prevalence and function of CNV in C. gattii. Results We identified eight genetic clusters among publicly available Illumina whole genome sequence data from 212 C. gattii isolates through population structure analysis. Three clusters represent the VGIIa, VGIIb, and VGIIc subgroups from the North American Pacific Northwest. CNV was bioinformatically predicted and affected ~300–400 Kilobases (Kb) of the C. gattii VGII subgroup genomes. Sixty-seven loci, encompassing 58 genes, showed highly divergent patterns of copy number variation between VGII subgroups. Analysis of PFam domains within divergent CN variable genes revealed enrichment of protein domains associated with transport, cell wall organization and external encapsulating structure. Conclusions CNVs may contribute to pathological and phenotypic differences observed between the C. gattii VGIIa, VGIIb, and VGIIc subpopulations. Genes overlapping with population differentiated CNVs were enriched for several virulence related functional terms. These results uncover novel candidate genes to examine the genetic and functional underpinnings of C. gattii pathogenicity. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3044-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jacob L Steenwyk
- Biology Department, Clark University, 950 Main Street, Worcester, MA, USA.,Current address: Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - John S Soghigian
- Biology Department, Clark University, 950 Main Street, Worcester, MA, USA.,Current address: Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, New Haven, CT, USA
| | - John R Perfect
- Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - John G Gibbons
- Biology Department, Clark University, 950 Main Street, Worcester, MA, USA.
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31
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Coelho C, Casadevall A. Cryptococcal therapies and drug targets: the old, the new and the promising. Cell Microbiol 2016; 18:792-9. [PMID: 26990050 DOI: 10.1111/cmi.12590] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 02/28/2016] [Accepted: 03/08/2016] [Indexed: 01/09/2023]
Abstract
Half a century after the introduction of Amphotericin B the management of cryptococcosis remains unsatisfactory. The disease, caused primarily by the two fungal species Cryptococcus neoformans and Cryptococcus gattii, remains responsible for considerable morbidity and mortality despite standard medical care. Current therapeutic options are limited to Amphotericin B, azoles and 5-flucytosine. However, this organism has numerous well-characterized virulence mechanisms that are amenable to pharmacological interference and are thus potential therapeutic targets. Here, we discuss existing approved antifungal drugs, resistance mechanisms to these drugs and non-standard antifungal drugs that have potential in treatment of cryptococcosis, including immunomodulatory strategies that synergize with antifungal drugs, such as cytokine administration or monoclonal antibodies. Finally, we summarize attempts to target well-described virulence factors of Cryptococcus, the capsule or fungal melanin. This review emphasizes the pressing need for new therapeutic alternatives for cryptococcosis.
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Affiliation(s)
- Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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Bielska E, May RC. What makes Cryptococcus gattii a pathogen? FEMS Yeast Res 2015; 16:fov106. [PMID: 26614308 DOI: 10.1093/femsyr/fov106] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2015] [Indexed: 02/06/2023] Open
Abstract
Cryptococcosis is an invasive fungal infection of humans and other animals, typically caused by the species Cryptococcus neoformans in patients with impaired immunity. However, there is growing recognition of the importance of the related species C. gattii in causing infections in apparently immunocompetent individuals. In particular, an ongoing outbreak of cryptococcal disease in the Pacific Northwest region, which started in 1999, has driven an intense research effort into this previously neglected pathogen. Here, we discuss some of the recent discoveries in this organism from the Pacific Northwest region and highlight areas for future investigation.
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Affiliation(s)
- Ewa Bielska
- Institute of Microbiology and Infection & School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Robin C May
- Institute of Microbiology and Infection & School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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Abstract
Understanding of the taxonomy and phylogeny of Cryptococcus gattii has been advanced by modern molecular techniques. C. gattii probably diverged from Cryptococcus neoformans between 16 million and 160 million years ago, depending on the dating methods applied, and maintains diversity by recombining in nature. South America is the likely source of the virulent C. gattii VGII molecular types that have emerged in North America. C. gattii shares major virulence determinants with C. neoformans, although genomic and transcriptomic studies revealed that despite similar genomes, the VGIIa and VGIIb subtypes employ very different transcriptional circuits and manifest differences in virulence phenotypes. Preliminary evidence suggests that C. gattii VGII causes severe lung disease and death without dissemination, whereas C. neoformans disseminates readily to the central nervous system (CNS) and causes death from meningoencephalitis. Overall, currently available data indicate that the C. gattii VGI, VGII, and VGIII molecular types more commonly affect nonimmunocompromised hosts, in contrast to VGIV. New, rapid, cheap diagnostic tests and imaging modalities are assisting early diagnosis and enabling better outcomes of cerebral cryptococcosis. Complications of CNS infection include increased intracranial pressure, severe neurological sequelae, and development of immune reconstitution syndrome, although the mortality rate is low. C. gattii VGII isolates may exhibit higher fluconazole MICs than other genotypes. Optimal therapeutic regimens are yet to be determined; in most cases, initial therapy with amphotericin B and 5-flucytosine is recommended.
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Yu SJ, Chang YL, Chen YL. Calcineurin signaling: lessons from Candida species. FEMS Yeast Res 2015; 15:fov016. [DOI: 10.1093/femsyr/fov016] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/06/2015] [Indexed: 12/24/2022] Open
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Abstract
Few among the millions of fungal species fulfill four basic conditions necessary to infect humans: high temperature tolerance, ability to invade the human host, lysis and absorption of human tissue, and resistance to the human immune system. In previously healthy individuals, invasive fungal disease is rare because animals' sophisticated immune systems evolved in constant response to fungal challenges. In contrast, fungal diseases occur frequently in immunocompromised patients. Paradoxically, successes of modern medicine have put increasing numbers of patients at risk for invasive fungal infections. Uncontrolled HIV infection additionally makes millions vulnerable to lethal fungal diseases. A concerted scientific and social effort is needed to meet these challenges.
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Affiliation(s)
- Julia R Köhler
- Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Arturo Casadevall
- Departments of Microbiology and Immunology and Medicine, Division of Infectious Diseases, Albert Einstein College of Medicine, New York, New York 10461
| | - John Perfect
- Division of Infectious Diseases, Duke Medical Center, Durham, North Carolina 27710
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Juvvadi PR, Lamoth F, Steinbach WJ. Calcineurin as a Multifunctional Regulator: Unraveling Novel Functions in Fungal Stress Responses, Hyphal Growth, Drug Resistance, and Pathogenesis. FUNGAL BIOL REV 2014; 28:56-69. [PMID: 25383089 DOI: 10.1016/j.fbr.2014.02.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Calcineurin signaling plays diverse roles in fungi in regulating stress responses, morphogenesis and pathogenesis. Although calcineurin signaling is conserved among fungi, recent studies indicate important divergences in calcineurin-dependent cellular functions among different human fungal pathogens. Fungal pathogens utilize the calcineurin pathway to effectively survive the host environment and cause life-threatening infections. The immunosuppressive calcineurin inhibitors (FK506 and cyclosporine A) are active against fungi, making targeting calcineurin a promising antifungal drug development strategy. Here we summarize current knowledge on calcineurin in yeasts and filamentous fungi, and review the importance of understanding fungal-specific attributes of calcineurin to decipher fungal pathogenesis and develop novel antifungal therapeutic approaches.
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Affiliation(s)
- Praveen R Juvvadi
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA
| | - Frédéric Lamoth
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA ; Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland ; Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland
| | - William J Steinbach
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Duke University Medical Center, Durham NC, USA ; Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham NC, USA
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Firacative C, Duan S, Meyer W. Galleria mellonella model identifies highly virulent strains among all major molecular types of Cryptococcus gattii. PLoS One 2014; 9:e105076. [PMID: 25133687 PMCID: PMC4136835 DOI: 10.1371/journal.pone.0105076] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 07/20/2014] [Indexed: 12/18/2022] Open
Abstract
Cryptococcosis is mainly caused by Cryptococcus neoformans. However, the number of cases due to C. gattii is increasing, affecting mainly immunocompetent hosts. C. gattii is divided into four major molecular types, VGI to VGIV, which differ in their host range, epidemiology, antifungal susceptibility and geographic distribution. Besides studies on the Vancouver Island outbreak strains, which showed that the subtype VGIIa is highly virulent compared to the subtype VGIIb, little is known about the virulence of the other major molecular types. To elucidate the virulence potential of the major molecular types of C. gattii, Galleria mellonella larvae were inoculated with ten globally selected strains per molecular type. Survival rates were recorded and known virulence factors were studied. One VGII, one VGIII and one VGIV strain were more virulent (p <0.05) than the highly virulent Vancouver Island outbreak strain VGIIa (CDCR265), 11 (four VGI, two VGII, four VGIII and one VGIV) had similar virulence (p >0.05), 21 (five VGI, five VGII, four VGIII and seven VGIV) were less virulent (p <0.05) while one strain of each molecular type were avirulent. Cell and capsule size of all strains increased markedly during larvae infection (p <0.001). No differences in growth rate at 37°C were observed. Melanin synthesis was directly related with the level of virulence: more virulent strains produced more melanin than less virulent strains (p <0.05). The results indicate that all C. gattii major molecular types exhibit a range of virulence, with some strains having the potential to be more virulent. The study highlights the necessity to further investigate the genetic background of more and less virulent strains in order to recognize critical features, other than the known virulence factors (capsule, melanin and growth at mammalian body temperature), that maybe crucial for the development and progression of cryptococcosis.
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Affiliation(s)
- Carolina Firacative
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Millennium Institute, Sydney, Australia
- Grupo de Microbiología, Instituto Nacional de Salud, Bogotá, Colombia
| | - Shuyao Duan
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Millennium Institute, Sydney, Australia
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Millennium Institute, Sydney, Australia
- * E-mail:
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Kwon-Chung KJ, Fraser JA, Doering TL, Wang Z, Janbon G, Idnurm A, Bahn YS. Cryptococcus neoformans and Cryptococcus gattii, the etiologic agents of cryptococcosis. Cold Spring Harb Perspect Med 2014; 4:a019760. [PMID: 24985132 PMCID: PMC4066639 DOI: 10.1101/cshperspect.a019760] [Citation(s) in RCA: 326] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cryptococcus neoformans and Cryptococcus gattii are the two etiologic agents of cryptococcosis. They belong to the phylum Basidiomycota and can be readily distinguished from other pathogenic yeasts such as Candida by the presence of a polysaccharide capsule, formation of melanin, and urease activity, which all function as virulence determinants. Infection proceeds via inhalation and subsequent dissemination to the central nervous system to cause meningoencephalitis. The most common risk for cryptococcosis caused by C. neoformans is AIDS, whereas infections caused by C. gattii are more often reported in immunocompetent patients with undefined risk than in the immunocompromised. There have been many chapters, reviews, and books written on C. neoformans. The topics we focus on in this article include species description, pathogenesis, life cycle, capsule, and stress response, which serve to highlight the specializations in virulence that have occurred in this unique encapsulated melanin-forming yeast that causes global deaths estimated at more than 600,000 annually.
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Affiliation(s)
- Kyung J Kwon-Chung
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - James A Fraser
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Zhou Wang
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Guilhem Janbon
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, 75015 Paris, France
| | - Alexander Idnurm
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri, Kansas City, Missouri 64110
| | - Yong-Sun Bahn
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
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Abstract
SummaryFungal pathogens pose a major threat to human health worldwide. They infect billions of people each year, leading to at least 1·5 million deaths. Treatment of fungal infections is difficult due to the limited number of clinically useful antifungal drugs, and the emergence of drug resistance. A promising new strategy to enhance the efficacy of antifungal drugs and block the evolution of drug resistance is to target the molecular chaperone Hsp90. Pharmacological inhibitors of Hsp90 function that are in development as anticancer agents have potential to be repurposed as agents for combination antifungal therapy for some applications, such as biofilm infections. For systemic infections, however, effective combination therapy regimens may require Hsp90 inhibitors that can selectively target Hsp90 in the pathogen, or alternate strategies to compromise function of the Hsp90 chaperone machine. Selectively impairing Hsp90 function in the pathogen could in principle be achieved by targeting Hsp90 co-chaperones or regulators of Hsp90 function that are more divergent between pathogen and host than Hsp90. Antifungal combination therapies could also exploit downstream effectors of Hsp90 that are critical for fungal drug resistance and virulence. Here, we discuss the progress and prospects for establishing Hsp90 as an important therapeutic target for life-threatening fungal infections.
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O'Meara TR, Cowen LE. Hsp90-dependent regulatory circuitry controlling temperature-dependent fungal development and virulence. Cell Microbiol 2014; 16:473-81. [PMID: 24438186 DOI: 10.1111/cmi.12266] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 01/09/2014] [Accepted: 01/13/2014] [Indexed: 11/28/2022]
Abstract
The pathogenic fungi Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans are an increasing cause of human mortality, especially in immunocompromised populations. During colonization and adaptation to various host environments, these fungi undergo morphogenetic alterations that allow for survival within the host. One key environmental cue driving morphological changes is external temperature. The Hsp90 chaperone protein provides one mechanism to link temperature with the signalling cascades that regulate morphogenesis, fungal development and virulence. Candida albicans is a model system for understanding the connections between morphogenesis and Hsp90. Due to the high degree of conservation in Hsp90, many of the connections in C. albicans may be extrapolated to other fungal pathogens or parasites. Examining the role of Hsp90 during development and morphogenesis in these three major fungal pathogens may provide insight into key aspects of adaptation to the host, leading to additional avenues for therapy.
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Affiliation(s)
- Teresa R O'Meara
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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Calcineurin controls hyphal growth, virulence, and drug tolerance of Candida tropicalis. EUKARYOTIC CELL 2014; 13:844-54. [PMID: 24442892 DOI: 10.1128/ec.00302-13] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Candida tropicalis, a species closely related to Candida albicans, is an emerging fungal pathogen associated with high mortality rates of 40 to 70%. Like C. albicans and Candida dubliniensis, C. tropicalis is able to form germ tubes, pseudohyphae, and hyphae, but the genes involved in hyphal growth machinery and virulence remain unclear in C. tropicalis. Recently, echinocandin- and azole-resistant C. tropicalis isolates have frequently been isolated from various patients around the world, making treatment difficult. However, studies of the C. tropicalis genes involved in drug tolerance are limited. Here, we investigated the roles of calcineurin and its potential target, Crz1, for core stress responses and pathogenesis in C. tropicalis. We demonstrate that calcineurin and Crz1 are required for hyphal growth, micafungin tolerance, and virulence in a murine systemic infection model, while calcineurin but not Crz1 is essential for tolerance of azoles, caspofungin, anidulafungin, and cell wall-perturbing agents, suggesting that calcineurin has both Crz1-dependent and -independent functions in C. tropicalis. In addition, we found that calcineurin and Crz1 have opposite roles in controlling calcium tolerance. Calcineurin serves as a negative regulator, while Crz1 plays a positive role for calcium tolerance in C. tropicalis.
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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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