The Candida albicans ENO1 gene encodes a transglutaminase involved in growth, cell division, morphogenesis, and osmotic protection

Abstract

Candida albicans is an opportunistic fungus that is part of the normal microflora commonly found in the human digestive tract and the normal mucosa or skin of healthy individuals. However, in immunocompromised individuals, it becomes a serious health concern and a threat to their lives and is ranked as the leading fungal infection in humans worldwide. As existing treatments for this infection are non-specific or under threat of developing resistance, there is a dire necessity to find new targets for designing specific drugs to defeat this fungus. Some authors reported the presence of the transglutaminase activity in Candida and Saccharomyces, but its identity remains unknown. We report here the phenotypic effects produced by the inhibition of transglutaminase enzymatic activity with cystamine, including growth inhibition of yeast cells, induction of autophagy in response to damage caused by cystamine, alteration of the normal yeast division pattern, changes in cell wall, and inhibition of the yeast-to-mycelium transition. The latter phenomenon was also observed in the C. albicans ATCC 26555 strain. Growth inhibition by cystamine was also determined in other Candida strains, demonstrating the importance of transglutaminase in these species. Finally, we identified enolase 1 as the cell wall protein responsible for TGase activity. After studying the inhibition of enzymatic activities with anti-CaEno1 antibodies and through bioinformatics studies, we suggest that the enolase and transglutaminase catalytic sites are localized in different domains of the protein. The aforementioned data indicate that TGase/Eno1 is a putative target for designing new drugs to control C. albicans infection.

The Cell Wall of Candida albicans: A Proteomics View

“…It also affected the yeast division pattern and the cell wall structure. Interestingly, the protein responsible for TGase activity in cell wall was identified as enolase by mass spectrometry [19].…”

“…Our group recently performed the 14 C-lysine labeling of proteins of the cell wall using them as endogenous substrates by the TGase present in this cellular fraction. Labeled proteins were then sequentially extracted with 2% SDS, and chitinase, separated by 10% SDS-PAGE and the proteins in radioactive areas were identified by tandem mass spectrometry (MS/MS) [19]. Most of the radioactive labeled proteins were identified in the SDS-solubilized fraction (1048 proteins), 37 proteins in the fraction solubilized with zymolyase, and 41 proteins were released with chitinase.…”

“…Hsp70 protein is involved in protein folding and translocation, has antigenic properties, and could play a role in the biosynthesis, secretion, and assembly of other components of the cell wall [73]. The full list of cell wall proteins identified from the sequential extractions with 2% SDS, zymolyase, and chitinase has been reported [19].…”

“…The analysis of all SDS-extracted proteins [19] in the PANTHER classification system according the cellular component revealed that 518 proteins (43.2%) correspond to cell part, two proteins (0.2%) belong to the extracellular region, 254 proteins (21.2%) are part of macromolecular complexes, 119 (9.9%) are membrane proteins, one (0.1%) belongs to the nucleoid, and replication factor C subunit 3 RFC3; nuclear pore complex protein NUP50; histones H2AZ, H2A.1, H2A.2, H3.3 and H4; histone deacetylase complex subunit SAP30L; high mobility group protein DSP1; transcription elongation factors SPT5 and SPT6; mediator of RNA polymerase II transcription subunits 10 (NUT2) and 4 (MED4); DNA-directed RNA polymerase II subunits RPB2, RPB7 and RPB8; single-stranded telomeric DNA-binding/mRNAbinding protein GBP2; DNA-directed RNA polymerase I subunit RPA49; negative cofactor 2 transcription regulator complex subunit HFL2; DNA-directed RNA polymerase III core subunit RPC19 and RPC40; RNA polymerase-associated protein LEO1 homolog; transcription factor IWS1; snoRNP complex protein SIK1; nucleolar protein 58 NOP58; Karyopherin β (Importin subunit β) and Karyopherin β-3 (Importin subunit β); Importin subunit α; restriction of telomere capping protein 3; U3 small nucleolar RNA-associated protein 22 UTP22; decapping protein 1, isoform a Proteasome Proteasome endopeptidase complex subunits PRE8 (proteasome subunit α type 2) and PRE9 (proteasome subunit α type 4); proteasome subunit β, proteasome regulatory particle base subunit RPN2 (26S proteasome non-ATPase regulatory subunit 1); proteasome regulatory particle lid subunit (26S proteasome non-ATPase regulatory subunit 8); proteasome regulatory particle base subunit RPN10 (26S proteasome non-ATPase regulatory subunit 4); proteasome regulatory particle lid subunit RPN5 (26S proteasome non-ATPase regulatory subunit 12); proteasome core particle subunit beta 1 PRE3; proteasome endopeptidase complex PRE10 (proteasome subunit α type 3); proteasome endopeptidase complex PRE5 (proteasome subunit α type-related); proteasome assembly chaperone 2; proteasome core particle subunit β4; proteasome core particle subunit β6; proteasome regulatory particle base subunit RPN1; proteasome endopeptidase complex PRE6; proteasome endopeptidase complex PUP2; 26S proteasome non-ATPase regulatory subunit 13 (proteasome regulatory particle lid subunit); proteasome endopeptidase complex SCL1 (proteasome subunit α type-6).…”

Processed Food Additive Microbial Transglutaminase and Its Cross-Linked Gliadin Complexes Are Potential Public Health Concerns in Celiac Disease

“…Microbiome [7,[12][13][14]24,25] Dysbiome [7,[12][13][14]24,25] Yeasts [34][35][36] Fungi [37,38] Viruses [15][16][17][18]…”