Fungal Dimorphism and Virulence: Molecular Mechanisms for Temperature Adaptation, Immune Evasion, and In Vivo Survival

Gauthier, Gregory M.

doi:10.1155/2017/8491383

Cited by 55 publications

(47 citation statements)

References 88 publications

(113 reference statements)

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“…Paracoccidioides spp. are dimorphic fungi that change their morphology according to the environmental temperature, with a transition from mold at 25 • C to yeast at 37 • C in human lungs (San-Blas and Vernet, 1977;Gauthier, 2017). Although the primary route of PCM infection is pulmonary, the disease is frequently diagnosed by extensive, ulcerative and painful buccal manifestations corresponding to the clinical form of the multifocal type (Franco et al, 1987;Mendes et al, 2017;de Arruda et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Mono- and Dual-Species Biofilm Formation and Interactions Between Paracoccidioides brasiliensis and Candida albicans

et al. 2020

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The oral cavity is a highly diverse microbial environment in which microorganisms interact with each other, growing as biofilms on biotic and abiotic surfaces. Understanding the interaction among oral microbiota counterparts is pivotal for clarifying the pathogenesis of oral diseases. Candida spp. is one of the most abundant fungi in the oral mycobiome with the ability to cause severe soft tissue lesions under certain conditions. Paracoccidioides spp., the causative agent of paracoccidioidomycosis, may also colonize the oral cavity leading to soft tissue damage. It was hypothesized that both fungi can interact with each other, increasing the growth of the biofilm and its virulence, which in turn can lead to a more aggressive infectivity. Therefore, this study aimed to evaluate the dynamics of mono-and dual-species biofilm growth of Paracoccidioides brasiliensis and Candida albicans and their infectivity using the Galleria mellonella model. Biomass and fungi metabolic activity were determined by the crystal violet and the tetrazolium salt reduction tests (XTT), respectively, and the colony-forming unit (CFU) was obtained by plating. Biofilm structure was characterized by both scanning electronic-and confocal laser scanning-microscopy techniques. Survival analysis of G. mellonella was evaluated to assess infectivity. Our results showed that dual-species biofilm with P. brasiliensis plus C. albicans presented a higher biomass, higher metabolic activity and CFU than their mono-species biofilms. Furthermore, G. mellonella larvae infected with P. brasiliensis plus C. albicans presented a decrease in the survival rate compared to those infected with P. brasiliensis or C. albicans, mainly in the form of biofilms. Our data indicate that P. brasiliensis and C. albicans coexistence is likely to occur on oral mucosal biofilms, as per in vitro and in vivo analysis. These data further widen the knowledge associated with the dynamics of fungal biofilm growth that can potentially lead to the discovery of new therapeutic strategies for these infections.

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Section: Introductionmentioning

confidence: 99%

Dynamics of Mono- and Dual-Species Biofilm Formation and Interactions Between Paracoccidioides brasiliensis and Candida albicans

et al. 2020

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“…Studies from several pathogenic fungi have shown that morphology is linked with expression of virulence factors, colonization of the host, and evasion of host immune responses, etc (69, 70). The cnbR Δ mutants are significantly less virulent in a heterologous wax moth larva host model (27); however, it was not clear if the diminished virulence potential of cnbR Δ mutants was due to morphology, loss of the calcineurin, or both.…”

Section: Discussionmentioning

confidence: 99%

A novel resistance pathway for calcineurin inhibitors in the human pathogenic MucoralesMucor circinelloides

Vellanki

Billmyre

Lorenzen

et al. 2019

Preprint

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24Mucormycosis is an emerging lethal fungal infection in immunocompromised 25 patients. Mucor circinelloides (Mucor) is a causal agent of mucormycosis and serves as 26 a model system to understand genetics in Mucorales. Calcineurin is a conserved 27 virulence factor in many pathogenic fungi and calcineurin inhibition or deletion of the 28 calcineurin regulatory subunit (CnbR) in Mucor results in a shift from hyphal to yeast 29 growth. We analyzed thirty-six calcineurin inhibitor resistant or bypass mutants that 30 exhibited hyphal growth in the presence of calcineurin inhibitors or in the yeast-locked 31 cnbR mutant background without carrying any mutations in known calcineurin 32 components. We found that a majority of the mutants had altered sequence in a gene, 33 named here bycA (bypass of calcineurin A). bycA encodes an amino acid permease. 34 We verified that both bycA, and the bycA cnbR double mutant are resistant to the 35 calcineurin inhibitor FK506, thereby demonstrating a novel resistance mechanism 36 against calcineurin inhibitors. We also found that the expression of bycA was 37 significantly higher in the wild type with FK506 and in the cnbR mutants, but 38 significantly lower in the wild type without FK506. These findings suggest that bycA is a 39 negative regulator of hyphal growth and/or a positive regulator of yeast growth in Mucor 40 and calcineurin suppresses the bycA gene at the mRNA level to promote hyphal growth. 41BycA is involved in the Mucor hyphal-yeast transition as our data demonstrates a 42 positive correlation between bycA expression, protein kinase A activity, and Mucor 43 yeast-growth. Also, calcineurin activity rather than hyphal morphology primarily 44 contributes to virulence traits including phagosome maturation blockade, host cell 45 damages, and pro-angiogenic growth factor induction during interactions with hosts. 46 3 Importance 47 Mucor is intrinsically resistant to most known antifungals, which makes 48 mucormycosis treatment challenging. Calcineurin is a serine/threonine phosphatase 49 widely conserved across eukaryotes. When calcineurin function is inhibited in Mucor, 50 growth shifts to a less-virulent yeast growth form which makes calcineurin an attractive 51 target for development of new antifungal drugs. Previously we identified two distinct 52 mechanisms through which Mucor can become resistant to calcineurin inhibitors 53 involving Mendelian mutations in the gene for FKBP12, calcineurin A or B subunits and 54 epimutations silencing the FKBP12 gene. Here, we identified a third novel mechanism 55 where loss of function mutations in the amino acid permease encoding the bycA gene 56 contribute to resistance against calcineurin inhibitors. When calcineurin activity is 57 absent, BycA can activate PKA to promote yeast growth via a cAMP-independent 58 pathway. Our data also shows that calcineurin activity, not morphology, primarily 59 contributes to host -pathogen interactions in the pathogenesis of Mucor. 60 61 62

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“…Studies of several pathogenic fungi have shown that morphology is linked with expression of virulence factors, colonization of the host, evasion of host immune responses, etc. (69,70). The cnbRΔ mutants were shown to be significantly less virulent in a heterologous wax moth larva host model (27); however, it was not clear if the diminished virulence potential of cnbRΔ mutants was due to morphology or loss of the calcineurin or both.…”

Section: A Novel Link Between Calcineurin and Byca An Amino Acid Permentioning

confidence: 99%

A Novel Resistance Pathway for Calcineurin Inhibitors in the Human-Pathogenic Mucorales Mucor circinelloides

Vellanki

Billmyre

Lorenzen

et al. 2020

mBio

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Mucormycosis is an emerging lethal fungal infection in immunocompromised patients. Mucor circinelloides is a causal agent of mucormycosis and serves as a model system to understand genetics in Mucorales. Calcineurin is a conserved virulence factor in many pathogenic fungi, and calcineurin inhibition or deletion of the calcineurin regulatory subunit (CnbR) in Mucor results in a shift from hyphal to yeast growth. We analyzed 36 calcineurin inhibitor-resistant or bypass mutants that exhibited hyphal growth in the presence of calcineurin inhibitors or in the yeast-locked cnbRΔ mutant background without carrying any mutations in known calcineurin components. We found that a majority of the mutants had altered sequence in a gene, named here bycA (bypass of calcineurin). bycA encodes an amino acid permease. We verified that both the bycAΔ single mutant and the bycAΔ cnbRΔ double mutant are resistant to calcineurin inhibitor FK506, thereby demonstrating a novel mechanism of resistance against calcineurin inhibitors. We also found that the level of expression of bycA was significantly higher in the wild-type strain treated with FK506 and in the cnbRΔ mutants but was significantly lower in the wild-type strain without FK506 treatment. These findings suggest that bycA is a negative regulator of hyphal growth and/or a positive regulator of yeast growth in Mucor and that calcineurin suppresses expression of the bycA gene at the mRNA level to promote hyphal growth. BycA is involved in the Mucor hypha-yeast transition as our data demonstrate positive correlations among bycA expression, protein kinase A activity, and Mucor yeast growth. Also, calcineurin, independently of its role in morphogenesis, contributes to virulence traits, including phagosome maturation blockade, host cell damages, and proangiogenic growth factor induction during interactions with hosts. IMPORTANCE Mucor is intrinsically resistant to most known antifungals, which makes mucormycosis treatment challenging. Calcineurin is a serine/threonine phosphatase that is widely conserved across eukaryotes. When calcineurin function is inhibited in Mucor, growth shifts to a less virulent yeast growth form, which makes calcineurin an attractive target for development of new antifungal drugs. Previously, we identified two distinct mechanisms through which Mucor can become resistant to calcineurin inhibitors involving Mendelian mutations in the gene for FKBP12, including mechanisms corresponding to calcineurin A or B subunits and epimutations silencing the FKBP12 gene. Here, we identified a third novel mechanism where loss-of-function mutations in the amino acid permease corresponding to the bycA gene contribute to resistance against calcineurin inhibitors. When calcineurin activity is absent, BycA can activate protein kinase A (PKA) to promote yeast growth via a cAMP-independent pathway. Our data also show that calcineurin activity contributes to host-pathogen interactions primarily in the pathogenesis of Mucor.

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Fungal Dimorphism and Virulence: Molecular Mechanisms for Temperature Adaptation, Immune Evasion, and In Vivo Survival

Cited by 55 publications

References 88 publications

Dynamics of Mono- and Dual-Species Biofilm Formation and Interactions Between Paracoccidioides brasiliensis and Candida albicans

Dynamics of Mono- and Dual-Species Biofilm Formation and Interactions Between Paracoccidioides brasiliensis and Candida albicans

A novel resistance pathway for calcineurin inhibitors in the human pathogenic MucoralesMucor circinelloides

A Novel Resistance Pathway for Calcineurin Inhibitors in the Human-Pathogenic Mucorales Mucor circinelloides

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