Biological functions of the autophagy-related proteins Atg4 and Atg8 in Cryptococcus neoformans.

Autophagy is a mechanism responsible for intracellular degradation and recycling of macromolecules and organelles, essential for cell survival in adverse conditions. More than 40 autophagy-related (ATG) genes have been identified and characterized in fungi, among them ATG4 and ATG8. ATG4 encodes a cysteine protease (Atg4) that plays an important role in autophagy by initially processing Atg8 at its C-terminus region. Atg8 is a ubiquitin-like protein essential for the synthesis of the double-layer membrane that constitutes the autophagosome vesicle, responsible for delivering the cargo from the cytoplasm to the vacuole lumen. The contributions of Atg-related proteins in the pathogenic yeast in the genus Cryptococcus remain to be explored, to elucidate the molecular basis of the autophagy pathway. In this context, we aimed to investigate the role of autophagy-related proteins 4 and 8 (Atg4 and Atg8) during autophagy induction and their contribution with non-autophagic events in C. neoformans. We found that Atg4 and Atg8 are conserved proteins and that they interact physically with each other. ATG gene deletions resulted in cells sensitive to nitrogen starvation. ATG4 gene disruption affects Atg8 degradation and its translocation to the vacuole lumen, after autophagy induction. Both atg4 and atg8 mutants are more resistant to oxidative stress, have an impaired growth in the presence of the cell wall-perturbing agent Congo Red, and are sensitive to the proteasome inhibitor bortezomib (BTZ). By that, we conclude that in C. neoformans the autophagy-related proteins Atg4 and Atg8 play an important role in the autophagy pathway; which are required for autophagy regulation, maintenance of amino acid levels and cell adaptation to stressful conditions.

The regulation of the sulfur amino acid biosynthetic pathway in Cryptococcus neoformans: the relationship of Cys3, Calcineurin, and Gpp2 phosphatases.

Cryptococcosis is a fungal disease caused by C. neoformans. To adapt and survive in diverse ecological niches, including the animal host, this opportunistic pathogen relies on its ability to uptake nutrients, such as carbon, nitrogen, iron, phosphate, sulfur, and amino acids. Genetic circuits play a role in the response to environmental changes, modulating gene expression and adjusting the microbial metabolism to the nutrients available for the best energy usage and survival. We studied the sulfur amino acid biosynthesis and its implications on C. neoformans biology and virulence. CNAG_04798 encodes a BZip protein and was annotated as CYS3, which has been considered an essential gene. However, we demonstrated that CYS3 is not essential, in fact, its knockout led to sulfur amino acids auxotroph. Western blots and fluorescence microscopy indicated that GFP-Cys3, which is expressed from a constitutive promoter, localizes to the nucleus in rich medium (YEPD); the addition of methionine and cysteine as sole nitrogen source (SD-N + Met/Cys) led to reduced nuclear localization and protein degradation. By proteomics, we identified and confirmed physical interaction among Gpp2, Cna1, Cnb1 and GFP-Cys3. Deletion of the calcineurin and GPP2 genes in a GFP-Cys3 background demonstrated that calcineurin is required to maintain Cys3 high protein levels in YEPD and that deletion of GPP2 causes GFP-Cys3 to persist in the presence of sulfur amino acids. Global transcriptional profile of mutant and wild type by RNAseq revealed that Cys3 controls all branches of the sulfur amino acid biosynthesis, and sulfur starvation leads to induction of several amino acid biosynthetic routes. In addition, we found that Cys3 is required for virulence in Galleria mellonella animal model.

Identifying Paracoccidioides phylogenetic species by PCR-RFLP of the alpha-tubulin gene.

Paracoccidioidomycosis is an important systemic fungal infection that occurs throughout Latin America. The etiological agents comprise a species complex that includes two major groups: P. brasiliensis (including subgroups S1, PS2, and PS3) and P. lutzii. A great number of phenotypes may overlap, especially among closely related groups, discouraging the use of morphology alone for species recognition. To overcome this problem, here we propose identifying cryptic Paracoccidioides spp. using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the alpha-tubulin (TUB1) gene. In silico analysis of 90 TUB1 sequences led to the identification of two restriction enzymes with the potential to identify Paracoccidioides: Bcl I and Msp I. A portion of the TUB1 gene was amplified and double digested in vitro with the Bcl I and Msp I endonucleases, which generated four different electrophoretic patterns corresponding to the four main genetic groups: S1, PS2, and PS3 of P. brasiliensis and P. lutzii. The major P. brasiliensis group recognized was S1 (n = 17; 42.5%), followed by PS2 (n = 9; 22.5%) and PS3 (n = 6; 15%). A total of eight (20%) P. lutzii isolates were identified, mainly from midwestern Brazil. Our data revealed that TUB1-RFLP is an efficient, fast, and inexpensive tool for identifying Paracoccidioides spp., which may be directly applied to the molecular epidemiological studies of paracoccidioidomycosis.

Diferentes intervalos de tempo de leitura do sistema API 20C AUX® na identificação de leveduras de interesse médico / Different reading time intervals of the API 20C AUX® system for identifying the yeasts of medical interest

Infecções de corrente sanguínea por leveduras do gênero Candida são uma das principais causas de morbidade e mortalidade em pacientes imunocomprometidos. Candida albicans permanece a espécie mais isolada nestas infecções e é de fácil e rápida identificação. Contudo, existem outras espécies, como C. parapsilosis, C. tropicalis, C. glabrata e C. krusei, que são encontradas com menor frequência e que necessitam de maior período de tempo e de metodologias comerciais automatizadas ou semi-automatizadas para sua identificação. Neste estudo foram analisadas 146 cepas de leveduras quanto à capacidade do Sistema API 20C AUX® (Biomerieux®, França) em identificar corretamente o gênero e a espécie de microrganismos em diferentes períodos de leitura, visando-se a liberação do resultado em menor tempo. C. parapsilosis, C. guilliermondii, C. pelliculosa, C. colliculosa, Rhodotorula mucilaginosa, Saccharomyces cerevisae, Trichosporon mucoides e T. asahii foram as leveduras cujos resultados finais puderam ser liberados nos períodos de tempo de 96, 120 e 144 h. Oitenta por cento das C. glabrata e 69 % das C. tropicalis também foram identificadas nos períodos além do tempo estabelecido. Com os resultados obtidos é possível antecipar a identificação do gênero e de algumas espécies de leveduras...