AfMkk2 is required for cell wall integrity signaling, adhesion, and full virulence of the human pathogen Aspergillus fumigatus

ABSTRACT Protein O-mannosyltransferases initiate O mannosylation of secretory proteins, which are of fundamental importance in eukaryotes. In this study, the PMT gene family of the human fungal pathogen Aspergillus fumigatus was identified and characterized. Unlike the case in Saccharomyces cerevisiae, where the PMT family is highly redundant, only one member of each PMT subfamily, namely, Afpmt1, Afpmt2, and Afpmt4, is present in A. fumigatus. Mutants with a deletion of Afpmt1 are viable. In vitro and in vivo activity assays confirmed that the protein encoded by Afpmt1 acts as an O-mannosyltransferase (AfPmt1p). Characterization of the ΔAfpmt1 mutant showed that a lack of AfPmt1p results in sensitivity to elevated temperature and defects in growth and cell wall integrity, thereby affecting cell morphology, conidium formation, and germination. In a mouse model, Afpmt1 was not required for the virulence of A. fumigatus under the experimental conditions used.

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Isolate-Dependent Growth, Virulence, and Cell Wall Composition in the Human Pathogen Aspergillus fumigatus

PLoS ONE ◽

10.1371/journal.pone.0100430 ◽

2014 ◽

Vol 9 (6) ◽

pp. e100430 ◽

Cited By ~ 18

Author(s):

Nansalmaa Amarsaikhan ◽

Evan M. O’Dea ◽

Angar Tsoggerel ◽

Henry Owegi ◽

Jordan Gillenwater ◽

...

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Cell Wall Composition ◽

Human Pathogen ◽

Dependent Growth

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Role of the Guanine Nucleotide Exchange Factor Rom2 in Cell Wall Integrity Maintenance of Aspergillus fumigatus

Eukaryotic Cell ◽

10.1128/ec.00246-12 ◽

2012 ◽

Vol 12 (2) ◽

pp. 288-298 ◽

Cited By ~ 21

Author(s):

Sweta Samantaray ◽

Michael Neubauer ◽

Christoph Helmschrott ◽

Johannes Wagener

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Guanine Nucleotide Exchange Factor ◽

Cell Wall Integrity ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Content Type ◽

Guanine Nucleotide Exchange ◽

Stress Sensors ◽

Nucleotide Exchange Factor

ABSTRACTAspergillus fumigatusis a mold and the causal agent of invasive aspergillosis, a systemic disease with high lethality. Recently, we identified and functionally characterized three stress sensors implicated in the cell wall integrity (CWI) signaling of this pathogen, namely, Wsc1, Wsc3, and MidA. Here, we functionally characterize Rom2, a guanine nucleotide exchange factor with essential function for the cell wall integrity ofA. fumigatus. A conditionalrom2mutant has severe growth defects under repressive conditions and incorporates all phenotypes of the three cell wall integrity sensor mutants, e.g., the echinocandin sensitivity of the Δwsc1mutant and the Congo red, calcofluor white, and heat sensitivity of the ΔmidAmutant. Rom2 interacts with Rho1 and shows a similar intracellular distribution focused at the hyphal tips. Our results place Rom2 between the cell surface stress sensors Wsc1, Wsc3, MidA, and Rho1 and their downstream effector mitogen-activated protein (MAP) kinase module Bck1-Mkk2-MpkA.

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Deciphering cell wall integrity signalling in Aspergillus fumigatus: identification and functional characterization of cell wall stress sensors and relevant Rho GTPases

Molecular Microbiology ◽

10.1111/j.1365-2958.2011.07946.x ◽

2012 ◽

Vol 83 (3) ◽

pp. 506-519 ◽

Cited By ~ 71

Author(s):

Karl Dichtl ◽

Christoph Helmschrott ◽

Franziska Dirr ◽

Johannes Wagener

Keyword(s):

Cell Wall ◽

Aspergillus Fumigatus ◽

Rho Gtpases ◽

Functional Characterization ◽

Wall Stress ◽

Cell Wall Integrity ◽

Cell Wall Stress ◽

Stress Sensors

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Heat Shock Protein 90 Is Required for Conidiation and Cell Wall Integrity in Aspergillus fumigatus

Eukaryotic Cell ◽

10.1128/ec.00032-12 ◽

2012 ◽

Vol 11 (11) ◽

pp. 1324-1332 ◽

Cited By ~ 84

Author(s):

Frédéric Lamoth ◽

Praveen R. Juvvadi ◽

Jarrod R. Fortwendel ◽

William J. Steinbach

Keyword(s):

Cell Wall ◽

Heat Shock ◽

Heat Shock Protein ◽

Aspergillus Fumigatus ◽

Cellular Localization ◽

Fluorescent Protein ◽

Heat Shock Protein 90 ◽

Cell Wall Integrity ◽

Compensatory Mechanisms ◽

Content Type

ABSTRACTHeat shock protein 90 (Hsp90) is a eukaryotic molecular chaperone. Its involvement in the resistance ofCandida albicansto azole and echinocandin antifungals is well established. However, little is known about Hsp90's function in the filamentous fungal pathogenAspergillus fumigatus. We investigated the role of Hsp90 inA. fumigatusby genetic repression and examined its cellular localization under various stress conditions. Failure to generate a deletion strain ofhsp90suggested that it is essential. Genetic repression of Hsp90 was achieved by an inducible nitrogen-dependent promoter (pniiA-Hsp90) and led to decreased spore viability, decreased hyphal growth, and severe defects in germination and conidiation concomitant with the downregulation of the conidiation-specific transcription factorsbrlA,wetA, andabaA. Hsp90 repression potentiated the effect of cell wall inhibitors affecting the β-glucan structure of the cell wall (caspofungin, Congo red) and of the calcineurin inhibitor FK506, supporting a role in regulating cell wall integrity pathways. Moreover, compromising Hsp90 abolished the paradoxical effect of caspofungin. Pharmacological inhibition of Hsp90 by geldanamycin and its derivatives (17-AAG and 17-DMAG) resulted in similar effects. C-terminal green fluorescent protein (GFP) tagging of Hsp90 revealed mainly cytosolic distribution under standard growth conditions. However, treatment with caspofungin resulted in Hsp90 accumulation at the cell wall and at sites of septum formation, further highlighting its role in cell wall stress compensatory mechanisms. Targeting Hsp90 with fungal-specific inhibitors to cripple stress response compensatory pathways represents an attractive new antifungal strategy.

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