Carbon metabolism snapshot by ddPCR during the early step of Candida albicans phagocytosis by macrophages

Abstract

During Candida macrophage interactions, phagocytosed yeast cells feed in order to grow, develop hyphae and escape. Through numerous proteomic and transcriptomic studies, two metabolic phases have been described. A shift to a starvation mode is generally identified as early as one-hour post phagocytosis, followed by a glycolytic growth mode after C. albicans escaped from the macrophage. Healthy macrophages contain low amounts of glucose. To determine if this carbon source was sensed and metabolized by the pathogen, we explored the transcription level of a delimited set of key genes expressed in C. albicans cells during phagocytosis by macrophages, at an early stage of the interaction. This analysis was performed using a technical digital droplet PCR approach to quantify reliably the expression of carbon metabolic genes after 30 min of phagocytosis. Our data confirm the technique of digital droplet PCR for the detection of C. albicans transcripts using cells recovered after a short period of phagocytosis. At this stage, carbon metabolism is clearly oriented towards the use of alternative sources. However, the activation of high-affinity glucose transport system suggests that the low amount of glucose initially present in the macrophages is detected by the pathogen.

The Dual Function of the Fungal Toxin Candidalysin during Candida albicans—Macrophage Interaction and Virulence

“…C. albicans counteracts oxidative and nitrosative stress by suppression of ROS generation [38], and production of detoxifying enzymes like superoxide dismutases [39][40][41][42]. Internalized fungal cells rapidly reprogram their metabolism to adapt to nutrient starvation inside the phagosome; this includes the up-regulation of genes involved in alternative carbon use (glyoxylate cycle and fatty acid beta oxidation), or encoding oligopeptide transporters and amino acid permeases whereas genes associated with protein biosynthesis are down-regulated [41,43,44]. The data indicate that C. albicans cells experience metabolic starvation inside the phagosome.…”

Deletion of the ATP2 Gene in Candida albicans Blocks Its Escape From Macrophage Clearance

“…Most C. albicans wild type cells can escape from the macrophage in 6-8 h (Wartenberg et al, 2014). In the early phase (1 h) of C. albicans-macrophages interaction, C. albicans switched to a slow gluconeogenic growth mode in the glucosedeficient environment, and in the late phase (6-8 h), along with hyphae formation and escape, C. albicans resumed rapid glycolytic growth (Lorenz et al, 2004;Tucey et al, 2018;Laurian et al, 2020). Why did ATP2 deletion lead to a substantial reduction of C. albicans escaping macrophage clearance?…”