Face/Off: The Interchangeable Side of Candida Albicans

Abstract

Due to limited mobility, fungi, like most unicellular organisms, have evolved mechanisms to adapt to sudden chemical and/or physical variation in their environment. Candida albicans is recognized as a model organism to study eukaryotic responses to environmental changes, as this human commensal yeast but also opportunistic pathogen responds to numerous environmental cues through switching morphologies from yeast to hyphae growth. This mechanism is largely controlled by two major pathways: cAMP-PKA and MAPK, but each environmental signal is sensed by specific sensors. However, morphological switching is not the only response C. albicans exerts in response to environmental cues. Recently, fungal cell wall remodeling in response to host-derived environmental cues has been identified as a way for C. albicans to manipulate the innate immune system. The fungal cell wall is composed of a chitin skeleton linked to a network of β-glucan, which anchors proteins and mannans to the fungal cell surface. As localized on the cell surface, these molecules drive interactions with the environment and other cells, particularly with host immune cells. C. albicans is recognized by immune cells such as neutrophils and macrophages via pathogen recognition receptors (PRRs) that bind different components of the cell wall. While β-glucan and mannan are proinflammatory molecules, chitin can induce anti-inflammatory responses. Interestingly, C. albicans is able to regulate the exposure of these pathogen-associated molecular patterns (PAMPs) according to environmental cues resulting in a modulation of the host immune response. This review describes the mechanisms involved in C. albicans response to environmental changes and their effect on immune recognition.

Applying Cryo-X-ray Photoelectron Spectroscopy to Study the Surface Chemical Composition of Fungi and Viruses

“…All of these exhibit differences in their surface chemistry relating to the structure and composition of their cell envelope, cell wall or particle surface. They also exhibit a large variation in size starting from viruses that are in the range of 20-500 nm (Encyclopedia Britannica, 2000) to fungal cells whose filaments can stretch dimensions of hundreds of micrometers (Cottier and Hall, 2020).…”

Differences in fungal immune recognition by monocytes and macrophages: N-mannan can be a shield or activator of immune recognition

“…The fungal cell wall is the primary point of contact with the components of the host innate immune system ( Erwig and Gow, 2016 ) and is a highly dynamic organelle essential for cell viability, morphogenesis, and pathogenesis ( Garcia-Rubio et al, 2019 , Gow et al, 2017 , Gow and Yadav, 2017 , Vendele et al, 2020 ). The composition and architecture of the fungal cell wall changes in response to different environmental and stress conditions and varies in different cell morphotypes, helping the fungi to adapt in different growth conditions ( Brown et al, 2014 , Cottier and Hall, 2019 , Hopke et al, 2018 ). The best studied cell wall of a fungal pathogen is that of Candida albicans ( Gow et al, 2012 , Gow and Hube, 2012 ) .…”

Aequorin as a Useful Calcium-Sensing Reporter in Candida albicans

“…This is usually followed by a return to normal cytosolic [Ca 2+ ] through efflux from the cell or by uptake into specific organelles that serve as internal stores (vacuoles, mitochondria, endoplasmic reticulum) [ 2 ]. Candida albicans is one of the major fungal pathogens affecting human health [ 3 ]. C. albicans uses [Ca 2+ ] flux in order to rapidly modulate responses important for morphogenesis [ 4 , 5 ].…”