The Lysine Deacetylase RpdA Is Essential for Virulence in Aspergillus fumigatus.

Ingo Bauer,Verena Petzer,Nir Osherov,Yana Shadkchan,Thomas Orasch,Hubertus Haas,Anna-Maria Dietl,Matthias Misslinger,Stefan Graessle,Beate Abt

doi:10.3389/fmicb.2019.02773

Abstract

Current suboptimal treatment options of invasive fungal infections and emerging resistance of the corresponding pathogens urge the need for alternative therapy strategies and require the identification of novel antifungal targets. Aspergillus fumigatus is the most common airborne opportunistic mold pathogen causing invasive and often fatal disease. Establishing a novel in vivo conditional gene expression system, we demonstrate that downregulation of the class 1 lysine deacetylase (KDAC) RpdA leads to avirulence of A. fumigatus in a murine model for pulmonary aspergillosis. The xylP promoter used has previously been shown to allow xylose-induced gene expression in different molds. Here, we demonstrate for the first time that this promoter also allows in vivo tuning of A. fumigatus gene activity by supplying xylose in the drinking water of mice. In the absence of xylose, an A. fumigatus strain expressing rpdA under control of the xylP promoter, rpdAxylP, was avirulent and lung histology showed significantly less fungal growth. With xylose, however, rpdAxylP displayed full virulence demonstrating that xylose was taken up by the mouse, transported to the site of fungal infection and caused rpdA induction in vivo. These results demonstrate that (i) RpdA is a promising target for novel antifungal therapies and (ii) the xylP expression system is a powerful new tool for in vivo gene silencing in A. fumigatus.

Highlights

Aspergillus fumigatus is the most common airborne mold pathogen, capable of causing systemic disease, termed invasive pulmonary aspergillosis, mostly in immunocompromised patients (van de Veerdonk et al, 2017)
The endogenous rpdA promoter was replaced by the xylP promoter with concomitant integration of a pyrithiamine resistance cassette via homologous recombination in A. fumigatus AfS35, termed wild type here, resulting in rpdAxylP transformants, which were verified by Southern blot analysis (Supplementary Figure S1)
It has been shown that the class 1 KDAC RpdA is essential for growth of both A. nidulans and A. fumigatus under axenic conditions (Tribus et al, 2010; Bauer et al, 2016)

Summary

Introduction

Aspergillus fumigatus is the most common airborne mold pathogen, capable of causing systemic disease, termed invasive pulmonary aspergillosis, mostly in immunocompromised patients (van de Veerdonk et al, 2017). The highly conserved N-terminal tails of histones are subject to a variety of post-translational modifications, which significantly impact the expression of genes. One of these modifications is the reversible acetylation of distinct lysine residues, catalyzed by lysine acetyltransferases and their counterparts, lysine deacetylases (KDACs), originally termed histone deacetylases (HDACs). The term KDAC appears more appropriate as it became evident that non-histone proteins are subject to acetylation by the very same enzymes (reviewed by Narita et al, 2019). One example for an A. fumigatus non-histone protein, whose acetylation status has been proposed to have significant implications on virulence, is the heat shock protein 90 (Lamoth et al, 2014)

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