Cryptococcus neoformans adapts to the host environment through TOR-mediated remodeling of phospholipid asymmetry

Ristow, Laura C.; Jezewski, Andrew J.; Chadwick, Benjamin J.; Stamnes, Mark A.; Lin, Xiaorong; Krysan, Damian J.

doi:10.1038/s41467-023-42318-y

Cited by 12 publications

(8 citation statements)

References 60 publications

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“…We previously discovered a positive association between the ability of C. neoformans to grow in 5% CO 2 and their virulence level in mouse models of cryptococcosis ( 21 ). To understand the transcriptome differences between CO 2 -tolerant and CO 2 -sensitive strains, we previously carried out RNA deep sequencing experiments using the reference clinical strain H99, and the environmental isolates A1-84-14 and A7-35-23 in 5% CO 2 or ambient air ( 21 , 23 , 24 ). H99 and A1-84-14 are both CO 2 tolerant, while A7-35-23 is highly sensitive to CO 2 ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…To decipher the unique transcriptome response in the CO 2 -sensitive strain A7-35-23, we identified 466 genes that were differentially expressed (fold change > 2 and P < 0.05) in A7-35-23 (5% CO 2 vs ambient air) but showed no significant change in the CO 2 -tolerant strains H99 and A1-84-14. We decided to focus on 34 of the 466 genes that encode potentially secretory proteins with a signal peptide, because we recently showed that CO 2 potentiates antifungal drugs that interfere with membrane ( 21 , 23 ) (Table S1). Of these 34 genes, 16 genes encode products with annotation of predicted function and 14 genes are covered in the H99 deletion sets generated by Dr. Hiten Madhani’s group.…”

Section: Resultsmentioning

confidence: 99%

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Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans

Li,

Chadwick,

Pham

et al. 2024

mBio

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Cryptococcus neoformans causes cryptococcal meningoencephalitis, a disease that kills more than 180,000 people annually. Contributing to its success as a fungal pathogen is its cell wall surrounded by a capsule. When the cryptococcal cell wall is compromised, exposed pathogen-associated molecular pattern molecules (PAMPs) could trigger host recognition and initiate attack against this fungus. Thus, cell wall composition and structure are tightly regulated. The cryptococcal cell wall is unusual in that chitosan, the acetylated form of chitin, is predominant over chitin and is essential for virulence. Recently, it was shown that acidic pH weakens the cell wall and increases exposure of PAMPs partly due to decreased chitosan levels. However, the molecular mechanism responsible for the cell wall remodeling in acidic pH is unknown. In this study, by screening for genes involved in cryptococcal tolerance to high levels of CO 2 , we serendipitously discovered that the aspartyl peptidase May1 contributes to cryptococcal sensitivity to high levels of CO 2 due to acidification of unbuffered media. Overexpression of MAY1 increases the cryptococcal cell size and elevates PAMP exposure, causing a hyper-inflammatory response in the host while MAY1 deletion does the opposite. We discovered that May1 weakens the cell wall and reduces the chitosan level, partly due to its involvement in the degradation of Chs3, the sole chitin synthase that supplies chitin to be converted to chitosan. Consistently, overexpression of CHS3 largely rescues the phenotype of MAY1 oe in acidic media. Collectively, we demonstrate that May1 remodels the cryptococcal cell wall in acidic pH by reducing chitosan levels through its influence on Chs3. IMPORTANCE The fungal cell wall is a dynamic structure, monitoring and responding to internal and external stimuli. It provides a formidable armor to the fungus. However, in a weakened state, the cell wall also triggers host immune attack when PAMPs, including glucan, chitin, and mannoproteins, are exposed. In this work, we found that the aspartyl peptidase May1 impairs the cell wall of Cryptococcus neoformans and increases the exposure of PAMPs in the acidic environment by reducing the chitosan level. Under acidic conditions, May1 is involved in the degradation of the chitin synthase Chs3, which supplies chitin to be deacetylated to chitosan. Consistently, the severe deficiency of chitosan in acidic pH can be rescued by overexpressing CHS3 . These findings improve our understanding of cell wall remodeling and reveal a potential target to compromise the cell wall integrity in this important fungal pathogen.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans

Li,

Chadwick,

Pham

et al. 2024

mBio

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“…Supporting this notion, Sch9 kinase and Sit4 phosphatase have been identified as necessary components for BBB infection ( Jin et al., 2020 ). Recently, the TOR pathway has been implicated in adaptation to the host environment through Ypk1-dependent phospholipid asymmetry remodeling ( Ristow et al., 2023 ). Besides kinases and phosphatases, Zfp1, which is homologous to Sfp1 and is involved in nutrient sensing and the cell cycle as a downstream transcription factor of TOR signaling in S. cerevisiae , is required for virulence in C. neoformans .…”

Section: Discussionmentioning

confidence: 99%

Pleiotropic roles of LAMMER kinase, Lkh1 in stress responses and virulence of Cryptococcus neoformans

Kwon,

Choi,

Kim

et al. 2024

Front. Cell. Infect. Microbiol.

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Dual-specificity LAMMER kinases are highly evolutionarily conserved in eukaryotes and play pivotal roles in diverse physiological processes, such as growth, differentiation, and stress responses. Although the functions of LAMMER kinase in fungal pathogens in pathogenicity and stress responses have been characterized, its role in Cryptococcus neoformans, a human fungal pathogen and a model yeast of basidiomycetes, remains elusive. In this study, we identified a LKH1 homologous gene and constructed a strain with a deleted LKH1 and a complemented strain. Similar to other fungi, the lkh1Δ mutant showed intrinsic growth defects. We observed that C. neoformans Lkh1 was involved in diverse stress responses, including oxidative stress and cell wall stress. Particularly, Lkh1 regulates DNA damage responses in Rad53-dependent and -independent manners. Furthermore, the absence of LKH1 reduced basidiospore formation. Our observations indicate that Lkh1 becomes hyperphosphorylated upon treatment with rapamycin, a TOR protein inhibitor. Notably, LKH1 deletion led to defects in melanin synthesis and capsule formation. Furthermore, we found that the deletion of LKH1 led to the avirulence of C. neoformans in a systemic cryptococcosis murine model. Taken together, Lkh1 is required for the stress response, sexual differentiation, and virulence of C. neoformans.

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“…It is understood that these proteins are promiscuous and transport a diverse array of substrates, and coupled with the expanded repertoire of PDR genes in Cryptococcus , it is not surprising to find roles other than traditional efflux pumps and subsequent resistance to xenobiotics. PDR6 has also been implicated in aging and replicative life span (13), and most recently, PDR9 , a full-length PDR gene in the same clade as AFR1 , was found to play a role in CO 2 tolerance via an unknown mechanism that may involve phospholipid flipping (48). Hence, PDR6 may act through multiple direct and indirect mechanisms to modulate the inflammatory host response, such as by secreting immunomodulatory molecules, aiding in maintaining the correct PM fluidity by regulating ergosterol transport, and preventing exposure of surface PAMPs by supporting correct cell wall and/or capsule architecture.…”

Section: Discussionmentioning

confidence: 99%

Lack of an atypical PDR transporter generates an immunogenicCryptococcus neoformansstrain that drives a dysregulated and lethal immune response in murine lungs

Winski,

Stuckey,

Marrufo

et al. 2024

Preprint

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Cryptococcus neoformansis an opportunistic fungal pathogen responsible for >150,000 deaths every year with a mortality rate as high as 81%. This high medical burden is due, in part, to an incomplete understanding of its pathogenesis. In a previous study, we identified a cryptococcal atypical pleiotropic drug resistance (PDR) transporter,PDR6, that regulated antifungal resistance and host interactions. Here, we follow-up on the role ofPDR6in cryptococcal virulence.In vivo, mice infected with thepdr6Δ strain display altered symptomatology and disease progression. Specifically, we observed a significant increase in the innate immune cell populations in thepdr6Δ-infected mice when compared to their WT-infected littermates. Furthermore, quantification of pulmonary cytokines/chemokines revealed a robust increase of pro-inflammatory cytokines in mice infected with thepdr6Δ mutant strain. Whereas antifungal treatment ofpdr6Δ-infected animals did not affect survival, treatment with a corticosteroid significantly extended survival, highlighting the importance of a balanced/controlled host immune response. We determined that the hyper-inflammatory immune response occurs, in part, because the loss of the Pdr6 transporter indirectly alters the cryptococcal cell wall architecture and results in the increased exposure of chitin, β-glucan, and other cryptococcal-specific pathogen associated molecular patterns. Taken together, this study provides clinical insights regarding cryptococcal pathogenesis while also providing additional functions of PDR-type ATP-binding cassette (ABC) transporters in pathogenic fungi.IMPORTANCEYeasts of theCryptococcusgenus, especiallyC. neoformans, can cause disease with unacceptably high mortality. This is due to delays in diagnostics, ineffective treatments, and an incomplete understanding of the interactions between this fungus and our immune system. In this study, we expand our knowledge of the biological function of thePDR6gene, particularly its effect on modulating the host’s immune response. Normally,C. neoformans’s infections are characterized by an anti-inflammatory response that is unable to control the yeast. In the absence ofPDR6, the response to the infection is a dysregulated pro-inflammatory response that initially controls the fungi but eventually results in death of the host due to too much tissue damage. This is due, in part, to an altered fungal surface. Given the dual role ofPDR6in modulating antifungal sensitivity and immune responses, this work provides important insights that may lead to new or improved therapeutics.

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Cryptococcus neoformans adapts to the host environment through TOR-mediated remodeling of phospholipid asymmetry

Cited by 12 publications

References 60 publications

Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans

Aspartyl peptidase May1 induces host inflammatory response by altering cell wall composition in the fungal pathogen Cryptococcus neoformans

Pleiotropic roles of LAMMER kinase, Lkh1 in stress responses and virulence of Cryptococcus neoformans

Lack of an atypical PDR transporter generates an immunogenicCryptococcus neoformansstrain that drives a dysregulated and lethal immune response in murine lungs

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