Recognition and control of neutrophil extracellular trap formation by MICL.

Regulation of neutrophil activation is critical for disease control. Neutrophil extracellular traps (NETs), which are web-like structures composed of DNA and neutrophil-derived proteins, are formed following pro-inflammatory signals; however, if this process is uncontrolled, NETs contribute to disease pathogenesis, exacerbating inflammation and host tissue damage1,2. Here we show that myeloid inhibitory C-type lectin-like (MICL), an inhibitory C-type lectin receptor, directly recognizes DNA in NETs; this interaction is vital to regulate neutrophil activation. Loss or inhibition of MICL functionality leads to uncontrolled NET formation through the ROS-PAD4 pathway and the development of an auto-inflammatory feedback loop. We show that in the context of rheumatoid arthritis, such dysregulation leads to exacerbated pathology in both mouse models and in human patients, where autoantibodies to MICL inhibit key functions of this receptor. Of note, we also detect similarly inhibitory anti-MICL autoantibodies in patients with other diseases linked to aberrant NET formation, including lupus and severe COVID-19. By contrast, dysregulation of NET release is protective during systemic infection with the fungal pathogen Aspergillus fumigatus. Together, we show that the recognition of NETs by MICL represents a fundamental autoregulatory pathway that controls neutrophil activity and NET formation.

Microfabrication and its use in investigating fungal biology.

Advances in microfabrication technology, and its increasing accessibility, allow us to explore fungal biology as never before. By coupling molecular genetics with fluorescence live-cell imaging in custom-designed chambers, we can now probe single yeast cell responses to changing conditions over a lifetime, characterise population heterogeneity and investigate its underlying causes. By growing filamentous fungi in complex physical environments, we can identify cross-species commonalities, reveal species-specific growth responses and examine physiological differences relevant to diverse fungal lifestyles. As affordability and expertise broadens, microfluidic platforms will become a standard technique for examining the role of fungi in cross-kingdom interactions, ranging from rhizosphere to microbiome to interconnected human organ systems. This review brings together the perspectives already gained from studying fungal biology in microfabricated systems and outlines their potential in understanding the role of fungi in the environment, health and disease.

Is There a Relationship Between Mating and Pathogenesis in Two Human Fungal Pathogens, Candida albicans and Candida glabrata?

Purpose of Review: Human fungal pathogens are rapidly increasing in incidence and readily able to evade the host immune responses. Our ability to study the genetic behind this has been limited due to the apparent lack of a sexual cycle and forward genetic tools. In this review, we discuss the evolution of mating, meiosis, and pathogenesis and if these processes are advantageous to pathogens. Recent Findings: This review summarises what is currently known about the sexual cycles of two important human fungal pathogens, Candida albicans and Candida glabrata. This includes the identification of parasexual cycle in C. albicans and the observed low levels of recombination in C. glabrata populations. Summary: In this review, we present what is currently known about the mating types and mating/sexual cycles of two clinically important human fungal pathogens, Candida albicans and Candida glabrata. We discuss the evolution of meiosis using the knowledge that has been amassed from the decades of studying Saccharomyces cerevisiae and how this can be applied to fungal pathogens. We further discuss how the evolution of pathogenesis has played a role in influencing mating processes in human fungal pathogens and compare sexual cycles between C. albicans and C. glabrata, highlighting knowledge gaps and suggesting how these two fungi have evolved distinct mating niches to allow the development of disease in a human host.

Multi trace element profiling in pathogenic and non-pathogenic fungi.

Maintaining appropriate levels of trace elements during infection of a host is essential for microbial pathogenicity. Here we compared the uptake of 10 trace elements from 3 commonly-used laboratory media by 3 pathogens, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, and a model yeast, Saccharomyces cerevisiae. The trace element composition of the yeasts, C. albicans, C. neoformans and S. cerevisiae, grown in rich (YPD) medium, differed primarily in P, S, Fe, Zn and Co. Speciation analysis of the intracellular fraction, which indicates the size of the organic ligands with which trace elements are complexed, showed that the ligands for S were similar in the three fungi but there were significant differences in binding partners for Fe and Zn between C. neoformans and S.cerevisiae. The profile for Cu varied across the 3 yeast species. In a comparison of C. albicans and A. fumigatus hyphae, the former showed higher Fe, Cu, Zn and Mn, while A. fumigatus contained higher P, S Ca and Mo. Washing C. albicans cells with the cell-impermeable chelator, EGTA, depleted 50-90 % of cellular Ca, suggesting that a large proportion of this cation is stored in the cell wall. Treatment with the cell wall stressor, Calcofluor White (CFW), alone had little effect on the elemental profile whilst combined Ca + CFW stress resulted in high cellular Cu and very high Ca. Together our data enhance our understanding of trace element uptake by pathogenic fungi and provide evidence for the cell wall as an important storage organelle for Ca.

A conserved fungal hub protein involved in adhesion and drug resistance in the human pathogen Candida albicans.

Drug resistance and cellular adhesion are two key elements of both dissemination and prevalence of the human fungal pathogen Candida albicans. Smi1 belongs to a family of hub proteins conserved among the fungal kingdom whose functions in cellular signaling affect morphogenesis, cell wall synthesis and stress resistance. The data presented here indicate that C. albicans SMI1 is a functional homolog of Saccharomyces cerevisiae KNR4 and is involved in the regulation of cell wall synthesis. Expression of SMI1 in S. cerevisiae knr4Δ null mutants rescued their sensitivity to caspofungin and to heat stress. Deletion of SMI1 in C. albicans resulted in sensitivity to the cell-wall-perturbing compounds Calcofluor White and Caspofungin. Analysis of wild-type and mutant cells by Atomic Force Microscopy showed that the Young's Modulus (stiffness) of the cell wall was reduced by 85% upon deletion of SMI1, while cell surface adhesion measured by Force Spectroscopy showed that the surface expression of adhesive molecules was also reduced in the mutant. Over-expression of SMI1, on the contrary, increased cell surface adhesion by 6-fold vs the control strain. Finally, Smi1-GFP localized as cytoplasmic patches and concentrated spots at the sites of new cell wall synthesis including the tips of growing hyphae, consistent with a role in cell wall regulation. Thus, Smi1 function appears to be conserved across fungi, including the yeast S. cerevisiae, the yeast and hyphal forms of C. albicans and the filamentous fungus Neurospora crassa.