Polymorphism in the regulatory regions of genes CgYPS1 and CgYPS7 encoding yapsins in Candida glabrata is associated with changes in expression levels

Exploring the effects of culture conditions on Yapsin (YPS) gene expression in Nakaseomyces glabratus

Nakaseomyces glabratus, previously known as Candida glabrata, has the great potential to cause systemic fungal infections despite its similarity to baker's yeast. Its pathogenicity is attributed to the production of numerous virulence factors, among which the YPS genes (YPS1-YPS11) encoding aspartyl proteases have yet to be sufficiently characterized, and limited studies suggest their involvement in cellular homeostasis. The study's novelty is an investigation of the role of YPS in N. glabratus's ability to adapt to different host environments. For this purpose, we isolated RNA from N. glabratus cells grown in both host niche-mimicking culture media, such as artificial saliva (AS) and vagina-simulating media (VS), as well as standard yeast media (RPMI 1640 and YPDA). We then performed quantitative real-time PCR to evaluate YPS gene expression at different growth phases. At the early logarithmic phase, we observed a general increase in the expression levels of YPS genes; however, at the stationary phase, high expression levels were maintained for YPS7 in RPMI 1640 and YPDA media and YPS6 in RPMI 1640 and AS media. In addition, although the VS medium does not promote the proliferation of N. glabratus, the yeast can survive in an acidic environment, and the significantly overexpressed gene is YPS7. These findings underscore the significant modulation of N. glabratus YPS gene expression in response to external environmental conditions. This research provides insights into the molecular basis of N. glabratus pathogenicity and highlights new potential targets for antifungal therapy.

Candida glabrata Antifungal Resistance and Virulence Factors, a Perfect Pathogenic Combination

In recent years, a progressive increase in the incidence of invasive fungal infections (IFIs) caused by Candida glabrata has been observed. The objective of this literature review was to study the epidemiology, drug resistance, and virulence factors associated with the C. glabrata complex. For this purpose, a systematic review (January 2001-February 2021) was conducted on the PubMed, Scielo, and Cochrane search engines with the following terms: "C. glabrata complex (C. glabrata sensu stricto, C. nivariensis, C. bracarensis)" associated with "pathogenicity" or "epidemiology" or "antibiotics resistance" or "virulence factors" with language restrictions of English and Spanish. One hundred and ninety-nine articles were found during the search. Various mechanisms of drug resistance to azoles, polyenes, and echinocandins were found for the C. glabrata complex, depending on the geographical region. Among the mechanisms found are the overexpression of drug transporters, gene mutations that alter thermotolerance, the generation of hypervirulence due to increased adhesion factors, and modifications in vital enzymes that produce cell wall proteins that prevent the activity of drugs designed for its inhibition. In addition, it was observed that the C. glabrata complex has virulence factors such as the production of proteases, phospholipases, and hemolysins, and the formation of biofilms that allows the complex to evade the host immune response and generate fungal resistance. Because of this, the C. glabrata complex possesses a perfect pathogenetic combination for the invasion of the immunocompromised host.

Phylogeny, evolution, and potential ecological relationship of cytochrome CYP52 enzymes in Saccharomycetales yeasts

Cytochrome P450s from the CYP52 family participate in the assimilation of alkanes and fatty acids in fungi. In this work, the evolutionary history of a set of orthologous and paralogous CYP52 proteins from Saccharomycetales yeasts was inferred. Further, the phenotypic assimilation profiles were related with the distribution of cytochrome CYP52 members among species. The maximum likelihood phylogeny of CYP52 inferred proteins reveled a frequent ancient and modern duplication and loss events that generated orthologous and paralogous groups. Phylogeny and assimilation profiles of alkanes and fatty acids showed a family expansion in yeast isolated from hydrophobic-rich environments. Docking analysis of deduced ancient CYP52 proteins suggests that the most ancient function was the oxidation of C4-C11 alkanes, while the oxidation of >10 carbon alkanes and fatty acids is a derived character. The ancient CYP52 paralogs displayed partial specialization and promiscuous interaction with hydrophobic substrates. Additionally, functional optimization was not evident. Changes in the interaction of ancient CYP52 with different alkanes and fatty acids could be associated with modifications in spatial orientations of the amino acid residues that comprise the active site. The extended family of CYP52 proteins is likely evolving toward functional specialization, and certain redundancy for substrates is being maintained.

Heterologous expression and characterization of the aspartic endoprotease Pep4um from Ustilago maydis, a homolog of the human Chatepsin D, an important breast cancer therapeutic target

The pep4um gene (um04926) of Ustilago maydis encodes a protein related to either vacuolar or lysosomal aspartic proteases. Bioinformatic analysis of the Pep4um protein revealed that it is a soluble protein with a signal peptide suggesting that it likely passes through the secretory pathway, and it has two probable self-activation sites, which are similar to those in Saccharomyces cerevisiae PrA. Moreover, the active site of the Pep4um has the two characteristic aspartic acid residues of aspartyl proteases. The pep4um gene was cloned, expressed in Pichia pastoris and a 54 kDa recombinant protein was observed. Pep4um-rec was confirmed to be an aspartic protease by specifically inhibiting its enzymatic activity with pepstatin A. Pep4um-rec enzymatic activity on acidic hemoglobin was optimal at pH 4.0 and at 40 °C. To the best of our knowledge this is the first report about the heterologous expression of an aspartic protease from a basidiomycete. An in-depth in silico analysis suggests that Pep4um is homolog of the human cathepsin D protein. Thus, the Pep4um-rec protein may be used to test inhibitors of human cathepsin D, an important breast cancer therapeutic target.