Abstract

Aspergillus fumigatus is an opportunistic fringal pathogen that causes invasive pulmonary infections in neutropenic patients. The infections carry high morbidity and mortality, especially when dissemination has occurred. A. fumigatus is able to penetrate blood vessels, and this property of angioinvasion allows the organism entry into the vascular compartment. During this past cycle, we identified a gene (rhbA) in the Ras family of small GTPases that is upregulated in A. fumigatus when it is grown on a monolayer of endothelial cells, as a model of angioinvasion. The gene is in the newly recognized Rheb group of the Ras family. Functions of Rheb proteins are not fully understood in mammalian or lower eukaryotic systems. Mammalian Rheb genes may serve to coordinate Ras and PKA signaling. In yeast, the gene appears to regulate arginine uptake, and in fission yeast, the gene is essential and its loss causes growth arrest in Go. In A. fumigatus, we have found that deletion of the gene results in attenuation of virulence in a mouse model of disseminated infection. We propose the following four specific aims to test our hypothesis that rhbA is a general regulator of transport in A. fumigatus The first aim is to determine what types of transporters may be disregulated in the ArhbA mutant, based on our discovery that the mutant is hypersensitive to the drugs FK506 and rapamycin and to sulfate.
The second aim i s to determine whether rhbA has the same function in A. fumigatus as has been reported for RSG] in S. cerevisiae. We will also test whether rhbA antagonizes the action of dominant active Ras.
The third aim i nvestigates the proteins with which RHBA interacts using the yeast two-hybrid assay.
The fourth aim tests whether the decrement in virulence seen in the deltarhbA mutant is due to lack of regulation of a specific interacting partner or whether it is due to the overall disregulation of transport that is seen in the null mutant. Completion of these aims should significantly clarify the function of rhbA in A. fumigatus.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI041119-05
Application #
6383505
Study Section
Special Emphasis Panel (ZRG1-MBC-1 (01))
Program Officer
Duncan, Rory A
Project Start
1997-08-01
Project End
2005-05-31
Budget Start
2001-08-01
Budget End
2002-05-31
Support Year
5
Fiscal Year
2001
Total Cost
$252,296
Indirect Cost

  Institution

Name
University of Cincinnati
Department
Pathology
Type
Schools of Medicine
DUNS #
City
Cincinnati
State
OH
Country
United States
Zip Code
45221

  Publications

Richie, Daryl L; Miley, Michael D; Bhabhra, Ruchi et al. (2007) The Aspergillus fumigatus metacaspases CasA and CasB facilitate growth under conditions of endoplasmic reticulum stress. Mol Microbiol 63:591-604
Rhodes, Judith C (2006) Aspergillus fumigatus: growth and virulence. Med Mycol 44 Suppl 1:S77-81
Zhao, Wei; Panepinto, John C; Fortwendel, Jarrod R et al. (2006) Deletion of the regulatory subunit of protein kinase A in Aspergillus fumigatus alters morphology, sensitivity to oxidative damage, and virulence. Infect Immun 74:4865-74
Fortwendel, Jarrod R; Zhao, Wei; Bhabhra, Ruchi et al. (2005) A fungus-specific ras homolog contributes to the hyphal growth and virulence of Aspergillus fumigatus. Eukaryot Cell 4:1982-9
Fortwendel, Jarrod R; Panepinto, John C; Seitz, Amy E et al. (2004) Aspergillus fumigatus rasA and rasB regulate the timing and morphology of asexual development. Fungal Genet Biol 41:129-39
Bhabhra, Ruchi; Miley, Michael D; Mylonakis, Eleftherios et al. (2004) Disruption of the Aspergillus fumigatus gene encoding nucleolar protein CgrA impairs thermotolerant growth and reduces virulence. Infect Immun 72:4731-40
Panepinto, John C; Oliver, Brian G; Fortwendel, Jarrod R et al. (2003) Deletion of the Aspergillus fumigatus gene encoding the Ras-related protein RhbA reduces virulence in a model of Invasive pulmonary aspergillosis. Infect Immun 71:2819-26
Panepinto, John C; Oliver, Brian G; Amlung, Thomas W et al. (2002) Expression of the Aspergillus fumigatus rheb homologue, rhbA, is induced by nitrogen starvation. Fungal Genet Biol 36:207-14
Oliver, Brian G; Panepinto, John C; Askew, David S et al. (2002) cAMP alteration of growth rate of Aspergillus fumigatus and Aspergillus niger is carbon-source dependent. Microbiology 148:2627-33
Oliver, Brian G; Panepinto, John C; Fortwendel, Jarrod R et al. (2002) Cloning and expression of pkaC and pkaR, the genes encoding the cAMP-dependent protein kinase of Aspergillus fumigatus. Mycopathologia 154:85-91

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