scholarly journals Role of clathrin-mediated endocytosis in the use of heme and hemoglobin by the fungal pathogen Cryptococcus neoformans

2018 ◽  
Author(s):  
Gaurav Bairwa ◽  
Mélissa Caza ◽  
Linda Horianopoulos ◽  
Guanggan Hu ◽  
James Kronstad
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Sugar Metabolism ◽  
Heme Iron ◽  
Heme Uptake ◽  
Iron Source ◽  
Life Threatening ◽  
Uptake Process ◽  
Underlying Mechanisms

SummaryHeme is a major source of iron for pathogens of humans, and its use is critical in determining the outcome of infection and disease. Cryptococcus neoformans is an encapsulated fungal pathogen that causes life-threatening infections in immunocompromised individuals. C. neoformans effectively uses heme as an iron source but the underlying mechanisms are poorly defined. Non-iron metalloporphyrins (MPPs) are toxic analogues of heme and are thought to enter microbial cells via endogenous heme acquisition systems. We therefore carried out a mutant screen for susceptibility against manganese metalloporphyrin (Mn MPP) to identify new components for heme uptake in C. neoformans. We identified several genes involved in signaling, DNA repair, sugar metabolism and trafficking that play important roles in susceptibility to Mn MPP and in the use of heme as an iron source. We focused on investigating the role of clathrin-mediated endocytosis (CME) and found that several components of CME including Chc1, Las17, Rvs161 and Rvs167 are required for growth on heme and hemoglobin, and for endocytosis and intracellular trafficking of these molecules. We show that the hemoglobin uptake process in C. neoformans involves clathrin heavy chain, Chc1, which appears to co-localize with hemoglobin containing-vesicles and to potentially assist in proper delivery of hemoglobin to the vacuole. Additionally, C. neoformans strains lacking Chc1, Las17, Rvs161, or Rvs167 were defective in the elaboration of several key virulence factors and a las17 mutant was avirulent in a mouse model of cryptococcosis. Overall, this study unveils crucial functions of CME in the use of heme iron by C. neoformans and reveals a role for CME in fungal pathogenesis.

scholarly journals Role of clathrin-mediated endocytosis in the use of heme and hemoglobin by the fungal pathogen Cryptococcus neoformans

2018 ◽  
Vol 21 (3) ◽  
pp. e12961 ◽  
Author(s):  
Gaurav Bairwa ◽  
Mélissa Caza ◽  
Linda Horianopoulos ◽  
Guanggan Hu ◽  
James Kronstad
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen

scholarly journals Emerging Roles of Exosomes in T1DM

2020 ◽  
Vol 11 ◽  
Author(s):  
Haipeng Pang ◽  
Shuoming Luo ◽  
Yang Xiao ◽  
Ying Xia ◽  
Xia Li ◽  
...  
Keyword(s):  
Autoimmune Disorder ◽  
Elevated Blood Glucose Level ◽  
The Status ◽  
Life Threatening ◽  
Novel Biomarkers ◽  
Therapeutic Tools ◽  
Underlying Mechanisms ◽  
The Relationship

Type 1 diabetes mellitus (T1DM) is a complex autoimmune disorder that mainly affects children and adolescents. The elevated blood glucose level of patients with T1DM results from absolute insulin deficiency and leads to hyperglycemia and the development of life-threatening diabetic complications. Although great efforts have been made to elucidate the pathogenesis of this disease, the precise underlying mechanisms are still obscure. Emerging evidence indicates that small extracellular vesicles, namely, exosomes, take part in intercellular communication and regulate interorgan crosstalk. More importantly, many findings suggest that exosomes and their cargo are associated with the development of T1DM. Therefore, a deeper understanding of exosomes is beneficial for further elucidating the pathogenic process of T1DM. Exosomes are promising biomarkers for evaluating the risk of developingty T1DM, monitoring the disease state and predicting related complications because their number and composition can reflect the status of their parent cells. Additionally, since exosomes are natural carriers of functional proteins, RNA and DNA, they can be used as therapeutic tools to deliver these molecules and drugs. In this review, we briefly introduce the current understanding of exosomes. Next, we focus on the relationship between exosomes and T1DM from three perspectives, i.e., the pathogenic role of exosomes in T1DM, exosomes as novel biomarkers of T1DM and exosomes as therapeutic tools for T1DM.

scholarly journals Cryptococcus neoformans Evades Pulmonary Immunity by Modulating Xylose Precursor Transport

2020 ◽  
Vol 88 (8) ◽  
Author(s):  
Lucy X. Li ◽  
Camaron R. Hole ◽  
Javier Rangel-Moreno ◽  
Shabaana A. Khader ◽  
Tamara L. Doering
Keyword(s):  
Cryptococcus Neoformans ◽  
Mutant Strain ◽  
Fungal Pathogen ◽  
Wild Type ◽  
Content Type ◽  
Helper Cell Type ◽  
Lymphoid Structures ◽  
Type Infection

ABSTRACT Cryptococcus neoformans is a fungal pathogen that kills almost 200,000 people each year and is distinguished by abundant and unique surface glycan structures that are rich in xylose. A mutant strain of C. neoformans that cannot transport xylose precursors into the secretory compartment is severely attenuated in virulence in mice yet surprisingly is not cleared. We found that this strain failed to induce the nonprotective T helper cell type 2 (Th2) responses characteristic of wild-type infection, instead promoting sustained interleukin 12p40 (IL-12p40) induction and increased IL-17A (IL-17) production. It also stimulated dendritic cells to release high levels of proinflammatory cytokines, a behavior we linked to xylose expression. We further discovered that inducible bronchus-associated lymphoid tissue (iBALT) forms in response to infection with either wild-type cryptococci or the mutant strain with reduced surface xylose; although iBALT formation is slowed in the latter case, the tissue is better organized. Finally, our temporal studies suggest that lymphoid structures in the lung restrict the spread of mutant fungi for at least 18 weeks after infection, which is in contrast to ineffective control of the pathogen after infection with wild-type cells. These studies demonstrate the role of xylose in modulation of host response to a fungal pathogen and show that cryptococcal infection triggers iBALT formation.

scholarly journals Transcription factor Liv4 is required for growth and pathogenesis of Cryptococcus neoformans

2020 ◽  
Vol 20 (3) ◽  
Author(s):  
Jiu Yi ◽  
Junjun Sang ◽  
Jingyu Zhao ◽  
Lei Gao ◽  
Yali Yang ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Regulatory Mechanisms ◽  
Regulatory Function ◽  
Growth Defect ◽  
Detailed Characterization ◽  
Phenotypic Changes ◽  
Life Threatening

ABSTRACT Cryptococcus neoformans is an important invasive fungal pathogen that causes life-threatening meningoencephalitis in humans. Its biological and pathogenic regulatory mechanisms remain largely unknown, particularly due to the presence of those core transcription factors (TFs). Here, we conducted a detailed characterization of the TF Liv4 in the biology and virulence of C. neoformans. Deletion of TF Liv4 protein resulted in growth defect under both normal and stress conditions (such as high temperature and cell wall/membrane damaging agents), drastic morphological damage and also attenuated virulence in C. neoformans. These phenotypic changes might be contributed to transcriptional abnormality in the liv4Δ mutant, in which several cryptococcal genes involved in energy metabolism and cell wall integrity were downregulated. Furthermore, ChIP-seq and ChIP-qPCR assays suggested TF Liv4 might exert its regulatory function in transcription by its activation of RBP1 in C. neoformans. Taken together, our work highlights the importance of TF Liv4 in the growth and virulence of C. neoformans, and it facilitates a better understanding of cryptococcal pathogenesis mechanisms.

scholarly journals Human astrocytes inhibit Cryptococcus neoformans growth by a nitric oxide-mediated mechanism.

1994 ◽  
Vol 180 (1) ◽  
pp. 365-369 ◽  
Author(s):  
S C Lee ◽  
D W Dickson ◽  
C F Brosnan ◽  
A Casadevall
Keyword(s):  
Nitric Oxide ◽  
Cryptococcus Neoformans ◽  
Interleukin 1 ◽  
Primary Cultures ◽  
Immune Deficiency Syndrome ◽  
Deficiency Syndrome ◽  
Effector Cells ◽  
Human Astrocytes ◽  
Life Threatening

Cryptococcus neoformans is an opportunistic fungus that causes life-threatening meningoencephalitis in 5-10% of patients with acquired immune deficiency syndrome. Cryptococcal meningoencephalitis is characterized by a lymphohistiocytic infiltrate, accumulation of encapsulated forms of C. neoformans, and varying degrees of glial reaction. Little is known about the contribution of endogenous central nervous system cells to the pathogenesis of cryptococcal infections. In this study, we investigated the role of astrocytes as potential effector cells against C. neoformans. Primary cultures of human fetal astrocytes, activated with interleukin 1 beta plus interferon gamma inhibited the growth of C. neoformans. The inhibition of C. neoformans growth was paralleled by production of nitrite, and reversed by the inhibitors of nitric oxide (NO.) synthase, NG-methyl-mono-arginine and NG-nitro-arginine methyl ester. The results suggest a novel function for human astrocytes in host defence and provide a precedent for the use of NO. as an antimicrobial effector molecule by human cells.

scholarly journals Central Nervous System Vasculitis for Cryptococcosis in an Immunocompetent Patient

Diseases ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 75 ◽  
Author(s):  
Dan Zimelewicz Oberman ◽  
Liliana Patrucco ◽  
Carolina Cuello Oderiz
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cryptococcus Neoformans ◽  
Cryptococcal Meningitis ◽  
Fungal Pathogen ◽  
Immunocompetent Patient ◽  
Central Nervous System Vasculitis ◽  
Diagnostic Challenge ◽  
Threatening Condition ◽  
Life Threatening

Cryptococcal meningitis is a life-threatening condition caused by a fungal pathogen, Cryptococcus neoformans, that can infect both immunosuppressed and immunocompetent hosts. It is an important cause of morbidity and mortality in severely immunodeficient patients. However, in an immunocompetent patient it represents a diagnostic challenge, mainly because it is extremely rare, but also because of its nonspecific clinical manifestation. Neurovascular involvement in cryptococcal meningitis is rare and not well known and only few reports have described this association. We describe a cryptococcal meningitis in an immunocompetent patient associated with central nervous system vasculitis.

scholarly journals A Predicted Mannoprotein Cmp1 Regulates Fungal Virulence in Cryptococcus neoformans

Pathogens ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 881
Author(s):  
Lian-Tao Han ◽  
Lei Wu ◽  
Tong-Bao Liu
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Gene Expression Pattern ◽  
Fungal Virulence ◽  
Human Fungal Pathogen ◽  
Overexpression Strain ◽  
Reproduction Process ◽  
Localization Analysis ◽  
Survival Assay

The capsule of the fungal pathogen Cryptococcus neoformans consists of glucuronoxylomannan (GXM), glucuronoxylomannogalactan (GXMGal), and mannoproteins (MPs). MPs are a kind of glycoproteins with low content but high immunogenicity, which can stimulate the immune protection of the host. However, there is not much information about the role of mannoproteins in virulence of the human fungal pathogen C. neoformans. In this study, we reported the identification and functional analysis of a predicted mannoprotein Cmp1 that regulates fungal virulence in C. neoformans. Gene expression pattern analysis indicates that the CMP1 gene was ubiquitously expressed at all stages of cryptococcal development. Subcellular localization analysis indicated that Cmp1 was localized in the cytoplasm of cryptococcal cells. Disruption or overexpression of CMP1 results in impairing capsule formation in Cryptococcus, but it does not affect the melanin production and sensitivity under various stress conditions, nor does it affect the sexual reproduction process of Cryptococcus. Survival assay showed that the pathogenicity of the cmp1Δ mutant or the CMP1 overexpression strain was significantly attenuated in a murine inhalation model of cryptococcosis. In conclusion, our findings implied that the mannoprotein Cmp1 is required for the virulence of C. neoformans.

scholarly journals The Pathogenic Fungus Cryptococcus neoformans Expresses Two Functional GDP-Mannose Transporters with Distinct Expression Patterns and Roles in Capsule Synthesis

2007 ◽  
Vol 6 (5) ◽  
pp. 776-785 ◽  
Author(s):  
Tricia R. Cottrell ◽  
Cara L. Griffith ◽  
Hong Liu ◽  
Ashley A. Nenninger ◽  
Tamara L. Doering
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Pathogenic Fungus ◽  
Expression Patterns ◽  
Growth Conditions ◽  
Phosphomannose Isomerase ◽  
Microarray Experiments ◽  
Life Threatening ◽  
Nucleotide Sugars ◽  
Intracellular Organelles

ABSTRACT Cryptococcus neoformans is a fungal pathogen that is responsible for life-threatening disease, particularly in the context of compromised immunity. This organism makes extensive use of mannose in constructing its cell wall, glycoproteins, and glycolipids. Mannose also comprises up to two-thirds of the main cryptococcal virulence factor, a polysaccharide capsule that surrounds the cell. The glycosyltransfer reactions that generate cellular carbohydrate structures usually require activated donors such as nucleotide sugars. GDP-mannose, the mannose donor, is produced in the cytosol by the sequential actions of phosphomannose isomerase, phosphomannomutase, and GDP-mannose pyrophosphorylase. However, most mannose-containing glycoconjugates are synthesized within intracellular organelles. This topological separation necessitates a specific transport mechanism to move this key precursor across biological membranes to the appropriate site for biosynthetic reactions. We have discovered two GDP-mannose transporters in C. neoformans, in contrast to the single such protein reported previously for other fungi. Biochemical studies of each protein expressed in Saccharomyces cerevisiae show that both are functional, with similar kinetics and substrate specificities. Microarray experiments indicate that the two proteins Gmt1 and Gmt2 are transcribed with distinct patterns of expression in response to variations in growth conditions. Additionally, deletion of the GMT1 gene yields cells with small capsules and a defect in capsule induction, while deletion of GMT2 does not alter the capsule. We suggest that C. neoformans produces two GDP-mannose transporters to satisfy its enormous need for mannose utilization in glycan synthesis. Furthermore, we propose that the two proteins have distinct biological roles. This is supported by the different expression patterns of GMT1 and GMT2 in response to environmental stimuli and the dissimilar phenotypes that result when each gene is deleted.

scholarly journals The interplay of phenotype and genotype in Cryptococcus neoformans disease

2020 ◽  
Vol 40 (10) ◽  
Author(s):  
Sophie Altamirano ◽  
Katrina M. Jackson ◽  
Kirsten Nielsen
Keyword(s):  
Patient Outcome ◽  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Proper Treatment ◽  
Rapid Adaptation ◽  
Complete Understanding ◽  
Phenotypic Changes ◽  
Life Threatening ◽  
Opportunistic Fungal Pathogen

Abstract Cryptococcus neoformans is an opportunistic fungal pathogen that causes life-threatening meningitis primarily in immunocompromised individuals. In order to survive and proliferate during infection, C. neoformans must adapt to a variety of stresses it encounters within the host. Patient outcome depends on the interaction between the pathogen and the host. Understanding the mechanisms that C. neoformans uses to facilitate adaptation to the host and promote pathogenesis is necessary to better predict disease severity and establish proper treatment. Several virulence phenotypes have been characterized in C. neoformans, but the field still lacks a complete understanding of how genotype and phenotype contribute to clinical outcome. Furthermore, while it is known that C. neoformans genotype impacts patient outcome, the mechanisms remain unknown. This lack of understanding may be due to the genetic heterogeneity of C. neoformans and the extensive phenotypic variation observed between and within isolates during infection. In this review, we summarize the current understanding of how the various genotypes and phenotypes observed in C. neoformans correlate with human disease progression in the context of patient outcome and recurrence. We also postulate the mechanisms underlying the genetic and phenotypic changes that occur in vivo to promote rapid adaptation in the host.

scholarly journals Using genetically encoded heme sensors to probe the mechanisms of heme uptake and homeostasis in Candida albicans

2020 ◽  
Author(s):  
Ziva Weissman ◽  
Mariel Pinsky ◽  
Rebecca K. Donegan ◽  
Amit R. Reddi ◽  
Daniel Kornitzer
Keyword(s):  
Candida Albicans ◽  
Genetic Analysis ◽  
Heme Oxygenase ◽  
Fungal Pathogen ◽  
Heme Uptake ◽  
Host Environment ◽  
Iron Source

ABSTRACTCandida albicans is a major fungal pathogen that can utilize hemin and hemoglobin as iron sources in the iron-scarce host environment. While C. albicans is a heme prototroph, we show here that it can also efficiently utilize external heme as a cellular heme source. Using genetically encoded ratiometric fluorescent heme sensors, we show that heme extracted from hemoglobin and free hemin enter the cells with different kinetics. Heme supplied as hemoglobin is taken up via the CFEM (Common in Fungal Extracellular Membrane) hemophore cascade, and reaches the cytoplasm over several hours, whereas entry of free hemin via CFEM-dependent and independent pathways is much faster, less than an hour. To prevent an influx of extracellular heme from reaching toxic levels in the cytoplasm, the cells deploy Hmx1, a heme oxygenase. Hmx1 was previously suggested to be involved in utilization of hemoglobin and hemin as iron sources, but we find that it is primarily required to prevent heme toxicity. Taken together, the combination of novel heme sensors with genetic analysis revealed new details of the fungal mechanisms of heme import and homeostasis, necessary to balance the uses of heme as essential cofactor and potential iron source against its toxicity.

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