Cell wall integrity is linked to mitochondria and phospholipid homeostasis in Candida albicans through the activity of the post‐transcriptional regulator Ccr4‐Pop2

Abstract

SummaryThe cell wall is essential for viability of fungi and is an effective drug target in pathogens such as Candida albicans. The contribution of post-transcriptional gene regulators to cell wall integrity in C. albicans is unknown. We show that the C. albicans Ccr4-Pop2 mRNA deadenylase, a regulator of mRNA stability and translation, is required for cell wall integrity. The ccr4/ pop2 mutants display reduced wall b-glucans and sensitivity to the echinocandin caspofungin. Moreover, the deadenylase mutants are compromised for filamentation and virulence. We demonstrate that defective cell walls in the ccr4/pop2 mutants are linked to dysfunctional mitochondria and phospholipid imbalance. To further understand mitochondrial function in cell wall integrity, we screened a Saccharomyces cerevisiae collection of mitochondrial mutants. We identify several mitochondrial proteins required for caspofungin tolerance and find a connection between mitochondrial phospholipid homeostasis and caspofungin sensitivity. We focus on the mitochondrial outer membrane SAM complex subunit Sam37, demonstrating that it is required for both trafficking of phospholipids between the ER and mitochondria and cell wall integrity. Moreover, in C. albicans also Sam37 is essential for caspofungin tolerance. Our study provides the basis for an integrative view of mitochondrial function in fungal cell wall biogenesis and resistance to echinocandin antifungal drugs.

Identification of Proteins Involved in pH Adaptation in Extremophile Yeast Yarrowia lipolytica

“…Similar conclusions were reported for stress adaptation in S. cerevisiae (Martínez-Pastor et al, 2010;Rodriguez-Colman et al, 2010) and Candida albicans (Dagley et al, 2011). VDAC is not only responsible for protein import into mitochondria but essentially contributes to antioxidant resistance of mitochondria (Tikunov et al, 2010).…”

“…Massive and tightly cross-linked polysaccharide cell walls are a specific attribute of all yeast species including Y. lipolytica. It protects the cells from rapid changes in environmental conditions but also substantially hinders experimental processing of yeast samples (Dagley et al, 2011). This problem is commonly addressed in transcriptomic studies, but proteomic research also requires optimal extraction procedures.…”

Exploiting mitochondria as targets for the development of new antifungals

“…[33][34][35][36] Biogenesis usually includes both the SAM (Sorting and Assembly Machinery) and the ERMES (ER-Mitochondrial Encounter Structure) complexes of proteins that are vitally important in the insertion of proteins in mitochondria through the Transporters of the Outer Membrane (TOMs) (Fig. 1).…”

A model system for mitochondrial biogenesis reveals evolutionary rewiring of protein import and membrane assembly pathways

“…mutant strains, with a loss of viability seen only for the deletion of the SAM50 gene. Given the emergence of data from S. cerevisiae suggesting the involvement of subunits of the SAM complex in contacts between the mitochondrial outer membrane and endoplasmic reticulum (48,49) and between the mitochondrial outer membrane and the mitochondrial inner membrane (50), C. albicans is a unique system in which to address the essential function of Sam50 that might distinguish it from Sam51.…”

“…The C. albicans sam37ΔΔ mutant and the sam37ΔΔ mutant overexpressing SAM35 (sam37ΔΔ SAM35↑↑) under the strong constitutive promoter TEF1 have been described previously (35). The sam51ΔΔ mutant was constructed by standard methods using PCR and homologous recombination, with the URA3 and ARG4-based selection cassettes (48). The conditional C. albicans sam50 mutant (sam50ΔSAM50↓↓) was made by deleting the first allele with the ARG4 marker cassette and placing the other allele under the control of the repressible MET3 promoter (1,362 bp of the 5′ UTR of MET3) by constructing a URA3-MET3 promoter fusion cassette.…”