Surface Stress Induces a Conserved Cell Wall Stress Response in the Pathogenic Fungus Candida albicans

Abstract

cThe human fungal pathogen Candida albicans can grow at temperatures of up to 45°C. Here, we show that at 42°C substantially less biomass was formed than at 37°C. The cells also became more sensitive to wall-perturbing compounds, and the wall chitin levels increased, changes that are indicative of wall stress. Quantitative mass spectrometry of the wall proteome using 15 N metabolically labeled wall proteins as internal standards revealed that at 42°C the levels of the ␤-glucan transglycosylases Phr1 and Phr2, the predicted chitin transglycosylases Crh11 and Utr2, and the wall maintenance protein Ecm33 increased. Consistent with our previous results for fluconazole stress, this suggests that a wall-remodeling response is mounted to relieve wall stress. Thermal stress as well as different wall and membrane stressors led to an increased phosphorylation of the mitogen-activated protein (MAP) kinase Mkc1, suggesting activation of the cell wall integrity (CWI) pathway. Furthermore, all wall and membrane stresses tested resulted in diminished cell separation. This was accompanied by decreased secretion of the major chitinase Cht3 and the endoglucanase Eng1 into the medium. Consistent with this, cht3 cells showed a similar phenotype. When treated with exogenous chitinase, cell clusters both from stressed cells and mutant strains were dispersed, underlining the importance of Cht3 for cell separation. We propose that surface stresses lead to a conserved cell wall remodeling response that is mainly governed by Mkc1 and is characterized by chitin reinforcement of the wall and the expression of remedial wall remodeling enzymes.

Role of Retrograde Trafficking in Stress Response, Host Cell Interactions, and Virulence of Candida albicans

“…Many of these proteins are also increased in the cell wall of C. albicans cells exposed to Congo red, Calcofluor white (16), or heat stress (17). Interestingly, exposure to fluconazole alters the cell wall proteome similarly to Congo red (16), indicating that plasma membrane stress may cause a cell wall stress response.…”

“…Sample preparation for MS analysis was performed as outlined previously (16,17) After treatment of 4 mg of freeze-dried cell wall pellet with 2 g Trypsin Gold (Promega) for 18 h, the resulting peptide mix was desalted using a C 18 tip column (Varian). Next, 250 ng of the desalted peptides in 10 l 0.1% trifluoroacetic acid (TFA) was injected into an Ultimate 2000 nano-high-performance liquid chromatography (nano-HPLC) system (LC Packings) equipped with a PepMap100 C 18 reversed-phase column (75-m inner diameter, 25-cm length; Dionex).…”

Cell Wall-Related Bionumbers and Bioestimates of Saccharomyces cerevisiae and Candida albicans

“…The wall proteome of C. albicans has been extensively studied both qualitatively and quantitatively (39,43). It shows an amazing adaptability that helps the cell to adequately respond to changes in, for example, pH, temperature, hypoxic conditions, carbon source, and iron availability and to plasma membrane and wall stress (43)(44)(45)(46)(47)(48)(49). The wall proteome also reflects morphotype and contains yeast-and hypha-specific wall proteins (50).…”

Extracellular Electron Transfer Mediated by Flavins in Gram-positive Bacillus sp. WS-XY1 and Yeast Pichia stipitis

“…Most prior A C C E P T E D M A N U S C R I P T by thicker cell walls, which can increase the stress resistance of the cells by regulating their architecture and biophysical properties [5,6]. For example, Gram-positive bacteria have applications in high temperature and extreme pH environments [7][8][9][10]; whereas, studies into the EET mechanism that operates with such microorganisms have rarely reported in detail [11].…”