The incidence of fungal infection is increasing and yet available antifungal drugs are limited, some are toxic, and drug resistant strains are emerging. We have elucidated a conserved signal transduction cascade that controls virulence of Cryptococcus neoformans, the leading cause of fungal meningitis. The central element of this virulence pathway is the calcium-calmodulin activated protein phosphatase calcineurin, which is the molecular target of the immunosuppressive antifungal drugs cyclosporin A and FK506. C. neoformans mutants lacking either the catalytic A or the regulatory B subunit of calcineurin are inviable at 37 degrees C and other stress conditions and, as a consequence, are avirulent in animal models. In studies supported by this award, we identified: 1) the calcineurin B regulatory subunit and calmodulin, 2) the calcineurin binding protein (Cbpl) that is a conserved regulator or effector and which is the founding member of a protein family conserved from fungi to humans, and 3) the novel C2 domain protein Cts1 that may function as a downstream effector of the calcineurin signaling pathway to promote cell wall biogenesis and growth at 37degrees C. In parallel we discovered that calcineurin is required for virulence of Candida albicans, the most common human fungal pathogen. C. albicans cnb1/cnb1 mutants lacking the calcineurin B regulatory subunit are severely attenuated in animal models. Yet, in contrast to C. neoformans calcineurin is not required for growth of C. albicans at 37 degrees C. Instead, calcineurin is necessary for C. albicans to survive and proliferate in serum. These studies illustrate how a conserved signaling cascade has been co-opted to control virulence of two divergent fungal pathogens by unique molecular mechanisms. Here we propose to delineate this molecular virulence cascade in both C. neoformans and C. albicans. Importantly, this pathway can be targeted for therapeutic intervention using non-immunosuppressive calcineurin inhibitors that retain antifungal activity and synergistic drug combinations that we have discovered.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI042159-07
Application #
6892323
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Program Officer
Duncan, Rory A
Project Start
1998-01-01
Project End
2009-04-30
Budget Start
2005-05-01
Budget End
2006-04-30
Support Year
7
Fiscal Year
2005
Total Cost
$346,500
Indirect Cost
Name
Duke University
Department
Genetics
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
Geunes-Boyer, Scarlett; Beers, Michael F; Perfect, John R et al. (2012) Surfactant protein D facilitates Cryptococcus neoformans infection. Infect Immun 80:2444-53
Chen, Ying-Lien; Brand, Alexandra; Morrison, Emma L et al. (2011) Calcineurin controls drug tolerance, hyphal growth, and virulence in Candida dubliniensis. Eukaryot Cell 10:803-19
Aboobakar, Eanas F; Wang, Xuying; Heitman, Joseph et al. (2011) The C2 domain protein Cts1 functions in the calcineurin signaling circuit during high-temperature stress responses in Cryptococcus neoformans. Eukaryot Cell 10:1714-23
Kozubowski, Lukasz; Thompson, J Will; Cardenas, Maria E et al. (2011) Association of calcineurin with the COPI protein Sec28 and the COPII protein Sec13 revealed by quantitative proteomics. PLoS One 6:e25280
Kozubowski, Lukasz; Aboobakar, Eanas F; Cardenas, Maria E et al. (2011) Calcineurin colocalizes with P-bodies and stress granules during thermal stress in Cryptococcus neoformans. Eukaryot Cell 10:1396-402
Reedy, Jennifer L; Filler, Scott G; Heitman, Joseph (2010) Elucidating the Candida albicans calcineurin signaling cascade controlling stress response and virulence. Fungal Genet Biol 47:107-16
Kozubowski, Lukasz; Heitman, Joseph (2010) Septins enforce morphogenetic events during sexual reproduction and contribute to virulence of Cryptococcus neoformans. Mol Microbiol 75:658-75
Geunes-Boyer, Scarlett; Heitman, Joseph; Wright, Jo Rae et al. (2010) Surfactant protein D binding to Aspergillus fumigatus hyphae is calcineurin-sensitive. Med Mycol 48:580-8
Geunes-Boyer, Scarlett; Oliver, Timothy N; Janbon, Guilhem et al. (2009) Surfactant protein D increases phagocytosis of hypocapsular Cryptococcus neoformans by murine macrophages and enhances fungal survival. Infect Immun 77:2783-94
Idnurm, Alexander; Walton, Felicia J; Floyd, Anna et al. (2009) Identification of ENA1 as a virulence gene of the human pathogenic fungus Cryptococcus neoformans through signature-tagged insertional mutagenesis. Eukaryot Cell 8:315-26

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