Deletion of the Aspergillus fumigatus gene encoding the Ras-related protein RhbA reduces virulence in a model of Invasive pulmonary aspergillosis.
Aspergillus fumigatus is the predominant mold pathogen in patients who lack functional innate immunity. The A. fumigatus rhbA gene was first identified as a transcript that was upregulated when the organism was grown in the presence of mammalian cells. To gain insight into the function of rhbA in the growth and pathogenesis of A. fumigatus, we constructed a strain that lacks a functional rhbA gene. The Delta rhbA mutant showed a significant reduction in virulence compared to the virulence of the wild type in a mouse model of invasive aspergillosis. Complementation of the deletion with the wild-type gene restored full virulence. Although the Delta rhbA mutant grew as well as the wild type on solid medium containing the rich nitrogen source ammonium, the growth of the mutant was impaired on medium containing poor nitrogen sources. Like the Saccharomyces cerevisiae rhb1 mutant, the Delta rhbA mutant exhibited increased uptake of arginine. In addition, the Delta rhbA strain underwent asexual development in submerged cultures, even under ammonium-excess conditions. Growth of the mutant with poor nitrogen sources eliminated both the arginine uptake and submerged asexual development phenotypes. The mutant showed enhanced sensitivity to the TOR kinase inhibitor rapamycin. These findings establish the importance of rhbA for A. fumigatus virulence and suggest a role for rhbA in nutrient sensing.
Panepinto
John C
JC
Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45267, USA.
Oliver
Brian G
BG
Fortwendel
Jarrod R
JR
Smith
Darcey L H
DL
Askew
David S
DS
Rhodes
Judith C
JC
D000818:Animals; D001120:Arginine / Q000378:metabolism; D001228:Aspergillosis / Q000209:etiology*; D001232:Aspergillus fumigatus / Q000235:genetics* / Q000472:pathogenicity; D004195:Disease Models, Animal; D005260:Female; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology; D008172:Lung Diseases, Fungal / Q000209:etiology*; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics* / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D014774:Virulence
D005656:Fungal Proteins; D001120:Arginine; D020559:Monomeric GTP-Binding Proteins; D009584:Nitrogen; D020123:Sirolimus