scholarly journals Connecting virulence pathways to cell-cycle progression in the fungal pathogen Cryptococcus neoformans

2017 ◽  
Vol 63 (5) ◽  
pp. 803-811 ◽  
Author(s):  
Christina M. Kelliher ◽  
Steven B. Haase
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Cell Cycle Progression ◽  
Cycle Progression

scholarly journals Capsule Growth in Cryptococcus neoformans Is Coordinated with Cell Cycle Progression

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Rocío García-Rodas ◽  
Radames J. B. Cordero ◽  
Nuria Trevijano-Contador ◽  
Guilhem Janbon ◽  
Frédérique Moyrand ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Mutant Strain ◽  
Virulence Factor ◽  
Cell Cycle Progression ◽  
Regulatory Elements ◽  
Pathogenic Yeast ◽  
Cycle Progression ◽  
Content Type ◽  
Polysaccharide Capsule

ABSTRACT The fungal pathogen Cryptococcus neoformans has several virulence factors, among which the most important is a polysaccharide capsule. The size of the capsule is variable and can increase significantly during infection. In this work, we investigated the relationship between capsular enlargement and the cell cycle. Capsule growth occurred primarily during the G1 phase. Real-time visualization of capsule growth demonstrated that this process occurred before the appearance of the bud and that capsule growth arrested during budding. Benomyl, which arrests the cells in G2/M, inhibited capsule growth, while sirolimus (rapamycin) addition, which induces G1 arrest, resulted in cells with larger capsule. Furthermore, we have characterized a mutant strain that lacks a putative G1/S cyclin. This mutant showed an increased capacity to enlarge the capsule, both in vivo (using Galleria mellonella as the host model) and in vitro. In the absence of Cln1, there was a significant increase in the production of extracellular vesicles. Proteomic assays suggest that in the cln1 mutant strain, there is an upregulation of the glyoxylate acid cycle. Besides, this cyclin mutant is avirulent at 37°C, which correlates with growth defects at this temperature in rich medium. In addition, the cln1 mutant showed lower intracellular replication rates in murine macrophages. We conclude that cell cycle regulatory elements are involved in the modulation of the expression of the main virulence factor in C. neoformans. IMPORTANCE Cryptococcus neoformans is a pathogenic fungus that has significant incidence worldwide. Its main virulence factor is a polysaccharide capsule that can increase in size during infection. In this work, we demonstrate that this process occurs in a specific phase of the cell cycle, in particular, in G1. In agreement, mutants that have an abnormal longer G1 phase show larger capsule sizes. We believe that our findings are relevant because they provide a link between capsule growth, cell cycle progression, and virulence in C. neoformans that reveals new aspects about the pathogenicity of this fungus. Moreover, our findings indicate that cell cycle elements could be used as antifungal targets in C. neoformans by affecting both the growth of the cells and the expression of the main virulence factor of this pathogenic yeast.

scholarly journals Calcium Binding Protein Ncs1 Is Calcineurin Regulated in Cryptococcus neoformans and Essential for Cell Division and Virulence

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Eamim Daidrê Squizani ◽  
Júlia Catarina Vieira Reuwsaat ◽  
Sophie Lev ◽  
Heryk Motta ◽  
Julia Sperotto ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Calcium Binding ◽  
Cell Cycle Progression ◽  
Signaling Cascade ◽  
Calcium Sensor ◽  
Cycle Progression ◽  
Content Type ◽  
Bud Emergence ◽  
Fungal Meningitis

Cryptococcus neoformans is the major cause of fungal meningitis in HIV-infected patients. Several studies have highlighted the important contributions of Ca2+ signaling and homeostasis to the virulence of C. neoformans. Here, we identify the cryptococcal ortholog of neuronal calcium sensor 1 (Ncs1) and demonstrate its role in Ca2+ homeostasis, bud emergence, cell cycle progression, and virulence. We also show that Ncs1 function is regulated by the calcineurin/Crz1 signaling cascade. Our work provides evidence of a link between Ca2+ homeostasis and cell cycle progression in C. neoformans.

scholarly journals Calcium binding protein Ncs1 is calcineurin-regulated in Cryptococcus neoformans and essential for cell division and virulence

2020 ◽  
Author(s):  
Eamim Daidrê Squizani ◽  
Júlia Catarina Vieira Reuwsaat ◽  
Sophie Lev ◽  
Heryk Motta ◽  
Julia Sperotto ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Cell Cycle Progression ◽  
Calcium Sensor ◽  
Cycle Progression ◽  
Bud Emergence ◽  
Fungal Meningitis ◽  
Ef Hand ◽  
Signalling Cascade ◽  
Calcineurin Pathway

AbstractIntracellular calcium (Ca2+) is crucial for signal transduction in Cryptococcus neoformans, the major cause of fatal fungal meningitis. The calcineurin pathway is the only Ca2+-requiring signalling cascade implicated in cryptococcal stress adaptation and virulence, with Ca2+-binding mediated by the EF-hand domains of the Ca2+ sensor protein calmodulin. In this study, we identified the cryptococcal ortholog of neuronal calcium sensor-1 (Ncs1) as a member of the EF-hand superfamily. We demonstrated that Ncs1 has a role in Ca2+ homeostasis under stress and non-stress conditions, as the ncs1Δ mutant is sensitive to a high Ca2+ concentration and has an elevated basal Ca2+ level that correlates with increased expression of the Ca2+ transporter genes, CCH1 and MID1. Furthermore, NCS1 expression is induced by Ca2+, with the Ncs1 protein adopting a punctate subcellular distribution. We also demonstrate that, in contrast to Saccharomyces cerevisiae, NCS1 expression in C. neoformans is regulated by the calcineurin pathway via the transcription factor Crz1, as NCS1 expression is reduced by FK506 treatment and CRZ1 deletion. Moreover, the ncs1Δ mutant shares a high temperature and high Ca2+ sensitivity phenotype with the calcineurin and calmodulin mutants (cna1Δ and cam1Δ) and the NCS1 promoter contains two calcineurin/Crz1-dependent response elements (CDRE1). Ncs1-deficency coincided with reduced growth, characterized by delayed bud emergence and aberrant cell division, and hypovirulence in a mouse infection model. In summary, our data shows that Ncs1 plays distinct roles in Ca2+ sensing in C. neoformans despite widespread functional conservation of Ncs1 and other regulators of Ca2+ homeostasis.ImportanceCryptococcus neoformans is the major cause of fungal meningitis in HIV infected patients. Several studies have highlighted the important contribution of Ca2+ signalling and homeostasis to the virulence of C. neoformans. Here, we identify the cryptococcal ortholog of neuronal calcium sensor-1 (Ncs1) and demonstrate its role in Ca2+ homeostasis, bud emergence, cell cycle progression and virulence. We also show that Ncs1 function is regulated by the calcineurin/Crz1 signalling cascade. Our work provides evidence of a link between Ca2+ homeostasis and cell cycle progression in C. neoformans.

scholarly journals A fungal arrestin protein contributes to cell cycle progression and pathogenesis

2019 ◽  
Author(s):  
Calla L. Telzrow ◽  
Connie B. Nichols ◽  
Natalia Castro-Lopez ◽  
Floyd L. Wormley ◽  
J. Andrew Alspaugh
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Cell Cycle Progression ◽  
Lipid Synthesis ◽  
Adaptor Protein ◽  
Cellular Responses ◽  
Fungal Virulence ◽  
Human Fungal Pathogen ◽  
Mutant Phenotypes

ABSTRACTArrestins, a structurally specialized and functionally diverse group of proteins, are central regulators of adaptive cellular responses in eukaryotes. Previous studies on fungal arrestins have demonstrated their capacity to modulate diverse cellular processes through their adaptor functions, facilitating the localization and function of other proteins. However, the mechanisms by which arrestin-regulated processes are involved in fungal virulence remain unexplored. We have identified a small family of four arrestins - Ali1, Ali2, Ali3, and Ali4 - in the human fungal pathogen Cryptococcus neoformans. Using complementary microscopy, proteomic, and reverse genetic techniques, we have defined a role for Ali1 as a novel contributor to cytokinesis, a fundamental cell cycle-associated process. We observed that Ali1 strongly interacts with proteins involved in lipid synthesis, and that ali1Δ mutant phenotypes are rescued by supplementation with lipid precursors that are used to build cellular membranes. From these data, we hypothesize that Ali1 contributes to cytokinesis by serving as an adaptor protein, facilitating the localization of enzymes that modify the plasma membrane during cell division, specifically the fatty acid synthases, Fas1 and Fas2. Finally, we assessed the contributions of the C. neoformans arrestin family to virulence, to better understand the mechanisms by which arrestin-regulated adaptive cellular responses influence fungal infection. We observed that the C. neoformans arrestin family contributes to virulence, and that the individual arrestin proteins likely fulfill distinct functions that are important for disease progression.IMPORTANCETo survive in unpredictable conditions, all organisms must adapt to stressors by regulating adaptive cellular responses. Arrestin proteins are conserved regulators of adaptive cellular responses in eukaryotes. Studies that have been limited to mammals and model fungi have demonstrated that disruption of arrestin-regulated pathways is detrimental for viability. The human fungal pathogen Cryptococcus neoformans causes more than 180,000 infection-related deaths annually, especially among immunocompromised patients. In addition to being genetically-tractable, C. neoformans has a small arrestin family of four members, lending itself to a comprehensive characterization of its arrestin family. This study serves as a functional analysis of arrestins in a pathogen, particularly in the context of fungal fitness and virulence. We investigate the functions of one arrestin protein, Ali1, and define its novel contributions to cytokinesis. We additionally explore the virulence contributions of the C. neoformans arrestin family and find that they contribute to disease establishment and progression.

scholarly journals Effects of 5′-3′ Exonuclease Xrn1 on Cell Size, Proliferation and Division, and mRNA Levels of Periodic Genes in Cryptococcus neoformans

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 430
Author(s):  
Xueru Zhao ◽  
Xin Li ◽  
Ping Zhang ◽  
Chenxi Li ◽  
Weijia Feng ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cryptococcus Neoformans ◽  
Cell Size ◽  
Dna Content ◽  
Cell Cycle Progression ◽  
Polymerase Activity ◽  
Yeast Cells ◽  
Mrna Levels ◽  
Cancer Disease ◽  
Cycle Progression

Cell size affects almost all biosynthetic processes by controlling the size of organelles and disrupting the nutrient uptake process. Yeast cells must reach a critical size to be able to enter a new cell cycle stage. Abnormal changes in cell size are often observed under pathological conditions such as cancer disease. Thus, cell size must be strictly controlled during cell cycle progression. Here, we reported that the highly conserved 5′-3′ exonuclease Xrn1 could regulate the gene expression involved in the cell cycle pathway of Cryptococcus neoformans. Chromosomal deletion of XRN1 caused an increase in cell size, defects in cell growth and altered DNA content at 37 °C. RNA-sequencing results showed that the difference was significantly enriched in genes involved in membrane components, DNA metabolism, integration and recombination, DNA polymerase activity, meiotic cell cycle, nuclear division, organelle fission, microtubule-based process and reproduction. In addition, the proportion of the differentially expressed periodic genes was up to 19.8% when XRN1 was deleted, including cell cycle-related genes, chitin synthase genes and transcription factors, indicating the important role of Xrn1 in the control of cell cycle. This work provides insights into the roles of RNA decay factor Xrn1 in maintaining appropriate cell size, DNA content and cell cycle progression.

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