Fungal biofilm morphology impacts hypoxia fitness and disease progression

Kowalski, Caitlin H.; Kerkaert, Joshua D.; Liu, Ko-Wei; Bond, Matthew C.; Hartmann, Raimo; Nadell, Carey D.; Stajich, Jason E.; Cramer, Robert A.

doi:10.1038/s41564-019-0558-7

Cited by 85 publications

(181 citation statements)

References 43 publications

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“…The severe growth defect of the ΔsrcA/ΔpmrA mutant likely accounts for much of this reduced virulence capacity. However, it is also possible that changes in cell wall structure and composition that occur in vivo may be different from those that occur in vitro, which could affect inflammatory responses or colony morphology and thus would also impact virulence (39,54,57). Together, these findings indicate that the UPR targets SrcA and PmrA are jointly required to support the virulence of A. fumigatus, providing further support for the idea of UPR as a regulatory hub for fungal pathogenicity.…”

Section: Downloaded Frommentioning

confidence: 82%

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Weichert

Guirao-Abad

Aimanianda

et al. 2020

mBio

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Many species of pathogenic fungi deploy the unfolded protein response (UPR) to expand the folding capacity of the endoplasmic reticulum (ER) in proportion to the demand for virulence-related proteins that traffic through the secretory pathway. Although Ca2+ plays a pivotal role in ER function, the mechanism by which transcriptional upregulation of the protein folding machinery is coordinated with Ca2+ homeostasis is incompletely understood. In this study, we investigated the link between the UPR and genes encoding P-type Ca2+-ATPases in the human-pathogenic mold Aspergillus fumigatus. We demonstrate that acute ER stress increases transcription of the srcA gene, encoding a member of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) family, as well as that of pmrA, encoding a secretory pathway Ca2+-ATPase (SPCA) in the Golgi membrane. Loss of the UPR transcription factor HacA prevented the induction of srcA and pmrA transcription during ER stress, defining these ER/Golgi Ca2+ pumps as novel downstream targets of this pathway. While deletion of srcA alone caused no major deficiencies, a ΔsrcA/ΔpmrA mutant displayed a severe polarity defect, was hypersensitive to ER stress, and showed attenuated virulence. In addition, cell wall analyses revealed a striking reduction in mannose levels in the absence of both Ca2+ pumps. The ΔhacA mutant was hypersensitive to agents that block calcineurin-dependent signaling, consistent with a functional coupling between the UPR and Ca2+ homeostasis. Together, these findings demonstrate that the UPR integrates the need for increased levels of chaperone and folding enzymes with an influx of Ca2+ into the secretory pathway to support fungal growth, stress adaptation, and pathogenicity. IMPORTANCE The UPR is an intracellular signal transduction pathway that maintains homeostasis of the ER. The pathway is also tightly linked to the expression of virulence-related traits in diverse species of human-pathogenic and plant-pathogenic fungal species, including the predominant mold pathogen infecting humans, Aspergillus fumigatus. Despite advances in the understanding of UPR signaling, the linkages and networks that are governed by this pathway are not well defined. In this study, we revealed that the UPR is a major driving force for stimulating Ca2+ influx at the ER and Golgi membranes and that the coupling between the UPR and Ca2+ import is important for virulence, cell wall biosynthesis, and resistance to antifungal compounds that inhibit Ca2+ signaling.

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Section: Downloaded Frommentioning

confidence: 82%

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Weichert

Guirao-Abad

Aimanianda

et al. 2020

mBio

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“…Recently, Shevchenko and colleagues utilized confocal microscopy to investigate neutrophil recruitment and location in the conducting airway upon A. fumigatus infection (35). In a further development, Kowalski and colleagues utilized the passive clarity technique (PACT) to investigate the architecture of in vivo fungal growth in cleared lungs using confocal microscopy (36). Although these studies represent a significant improvement compared with previous techniques, confocal microscopy is still limited by the small fraction of tissue imaged, which makes any quantification and anatomical information of limited value.…”

Section: Discussionmentioning

confidence: 99%

Three-Dimensional Light Sheet Fluorescence Microscopy of Lungs To Dissect Local Host Immune-Aspergillus fumigatus Interactions

Amich

Mokhtari

Strobel

et al. 2020

mBio

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Aspergillus fumigatus is an opportunistic fungal pathogen that can cause life-threatening invasive lung infections in immunodeficient patients. The cellular and molecular processes of infection during onset, establishment, and progression of A. fumigatus infections are highly complex and depend on both fungal attributes and the immune status of the host. Therefore, preclinical animal models are of paramount importance to investigate and gain better insight into the infection process. Yet, despite their extensive use, commonly employed murine models of invasive pulmonary aspergillosis are not well understood due to analytical limitations. Here, we present quantitative light sheet fluorescence microscopy (LSFM) to describe fungal growth and the local immune response in whole lungs at cellular resolution within its anatomical context. We analyzed three very common murine models of pulmonary aspergillosis based on immunosuppression with corticosteroids, chemotherapy-induced leukopenia, or myeloablative irradiation. LSFM uncovered distinct architectures of fungal growth and degrees of tissue invasion in each model. Furthermore, LSFM revealed the spatial distribution, interaction, and activation of two key immune cell populations in antifungal defense: alveolar macrophages and polymorphonuclear neutrophils. Interestingly, the patterns of fungal growth correlated with the detected effects of the immunosuppressive regimens on the local immune cell populations. Moreover, LSFM demonstrates that the commonly used intranasal route of spore administration did not result in complete intra-alveolar deposition, as about 80% of fungal growth occurred outside the alveolar space. Hence, characterization by LSFM is more rigorous than by previously used methods employing murine models of invasive pulmonary aspergillosis and pinpoints their strengths and limitations. IMPORTANCE The use of animal models of infection is essential to advance our understanding of the complex host-pathogen interactions that take place during Aspergillus fumigatus lung infections. As in the case of humans, mice need to suffer an immune imbalance in order to become susceptible to invasive pulmonary aspergillosis (IPA), the most serious infection caused by A. fumigatus. There are several immunosuppressive regimens that are routinely used to investigate fungal growth and/or immune responses in murine models of invasive pulmonary aspergillosis. However, the precise consequences of the use of each immunosuppressive model for the local immune populations and for fungal growth are not completely understood. Here, to pin down the scenarios involving commonly used IPA models, we employed light sheet fluorescence microscopy (LSFM) to analyze whole lungs at cellular resolution. Our results will be valuable to optimize and refine animal models to maximize their use in future research.

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“…One recent, striking example in support of the species-specific model was the discovery of the gene hypoxia-responsive morphology factor A or hrmA (Afu5g14900) [45]. While homologs of hmrA are present in other distantly related fungi, this subtelomeric gene is polymorphic within A. fumigatus and is absent from the genomes of all sequenced Aspergillus section Fumigati species.…”

Section: Support For the Species-specific Pathogenicity Modelmentioning

confidence: 99%

“…While homologs of hmrA are present in other distantly related fungi, this subtelomeric gene is polymorphic within A. fumigatus and is absent from the genomes of all sequenced Aspergillus section Fumigati species. Investigation of hrmA function shows that it likely regulates a cluster of genes, which also appear to be absent from the genomes of other Aspergillus section Fumigati species, that collectively contribute to the generation of a morphotype that facilitates adaptation to very low oxygen conditions encountered by the fungus inside human lungs [45].…”

Section: Support For the Species-specific Pathogenicity Modelmentioning

confidence: 99%

Evolving moldy murderers: Aspergillus section Fumigati as a model for studying the repeated evolution of fungal pathogenicity

et al. 2020

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Fungal biofilm morphology impacts hypoxia fitness and disease progression

Cited by 85 publications

References 43 publications

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Three-Dimensional Light Sheet Fluorescence Microscopy of Lungs To Dissect Local Host Immune-Aspergillus fumigatus Interactions

Evolving moldy murderers: Aspergillus section Fumigati as a model for studying the repeated evolution of fungal pathogenicity

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Fungal biofilm morphology impacts hypoxia fitness and disease progression

Cited by 85 publications

References 43 publications

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca 2+ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca 2+ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Three-Dimensional Light Sheet Fluorescence Microscopy of Lungs To Dissect Local Host Immune-Aspergillus fumigatus Interactions

Evolving moldy murderers: Aspergillus section Fumigati as a model for studying the repeated evolution of fungal pathogenicity

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Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus

Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca ²⁺ -ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus